• Journal of the Korean Regional Science Association
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• v.13 no.2
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• pp.45-54
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• 1997

A regional economy is characterized as a spatial economy. However the literature shows that it has been treated as a point economy since space is little recognized in regional modeling due to mathematical complication. This leads to the fact that regional model does not sufficiently represent regional characteristic. This paper attempts to construct a regional growth model in a partial equilibrium framework specifically taking into consideration land as a primary factor. The model is formulated largely neoclassical. Labor is assumed to move in response to differences in the wage rate, while capital is perfectly mobile across regions. The paper shows that two growth equilibrium points exist, one stable equilibrium point and the other unstable equilibrium point. The unstable growth equilibrium indicates the existence of minimum threshold that a region must overcome the minimum threshold to grow constantly. Consequently, directions of regional growth are characterized by two growth paths depending on the initial condition of a region. That is to say, a region below the minimum threshold is converging toward the lower stable equilibrium point over time. When a regional economy initially lies above the minimum threshold, it will grow forever. A regional economy is not thus necessarily converging a stationary is not thus necessarily converging a stationary equilibrium point through factor movement. Finally, the impacts of the presence of agglomeration economies and diseconomies are analyzed through the phase diagram. The paper also shows that agglomeration economies result in lowering the minimum threshold and in escalating the level of stable equilibrium However, when agglomeration diseconomies prevail, the results are opposite, i.e., rising the minimum threshold of growth and lowering the growth level of stable equilibrium.

• Molecules and Cells
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• v.45 no.2
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• pp.65-75
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• 2022

Hypothalamus is a brain region that controls food intake and energy expenditure while sensing signals that convey information about energy status. Within the hypothalamus, molecularly and functionally distinct neurons work in concert under physiological conditions. However, under pathological conditions such as in diet-induced obesity (DIO) model, these neurons show dysfunctional firing patterns and distorted regulation by neurotransmitters and neurohormones. Concurrently, resident glial cells including astrocytes dramatically transform into reactive states. In particular, it has been reported that reactive astrogliosis is observed in the hypothalamus, along with various neuroinflammatory signals. However, how the reactive astrocytes control and modulate DIO by influencing neighboring neurons is not well understood. Recently, new lines of evidence have emerged indicating that these reactive astrocytes directly contribute to the pathology of obesity by synthesizing and tonically releasing the major inhibitory transmitter GABA. The released GABA strongly inhibits the neighboring neurons that control energy expenditure. These surprising findings shed light on the interplay between reactive astrocytes and neighboring neurons in the hypothalamus. This review summarizes recent discoveries related to the functions of hypothalamic reactive astrocytes in obesity and raises new potential therapeutic targets against obesity.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.877-880
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• 1999

A rigorous formulation is suggested〔l,2,3〕 in solving the scattering of plane waves by a dielectric wedge. Correcting surface currents are expanded in a Neumann series of fractional orders to meet the edge condition of static limit〔4〕. For the better converging series, the modified Neumann series satisfying the static limit edge condition and the radiation condition are suggested here for the surface currents having two different wave numbers of air and dielectric〔4〕. This representation gives accurate solutions over the whole region including the grazing incidence of the plane waves upon the dielectric wedge of large permittivities.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.6
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• pp.102-108
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• 2011

The flow characteristics of unventilated dual impinging jets were experimentally investigated. Two nozzles with an aspect ratio of 20 were separated by 6 nozzle widths. The Reynolds number based on nozzle width and nozzle exit velocity was set to 5,000. A Particle Image Velocimetry (PIV) was used to measure turbulent velocity components. It was found that, when an impingement plate was installed in the converging region, there was a stagnation region in the inner area between nozzles. However, when it was installed in the combined region, both jets were merged and collided into the plate, showing single-jet characteristics. In addition, at a dual impinging jet, as the distance between a nozzle and an impingement plate decreased, the spanwise turbulent intensity at the plate increased.

• Phonetics and Speech Sciences
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• v.9 no.2
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• pp.39-51
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• 2017

The current study aims to investigate the effect of sociolinguistic factors such as region, generation and gender on the acoustic properties of Korean high and mid back vowels. We analyzed the vowel productions of one hundred twenty-eight subjects from the Korean Standard Speech Database, chosen to represent the different possible combinations of region, generation, and gender. The results reveal a chain-like shift in the back vowels. Unlike previous studies that have reported /o/-/u/ becoming closer as a result of a decreasing F1 in /o/, we found that the distance between the two vowels is decided more by the changing F2 in /u/. Also, the F2 of /u/ and /ɯ/, and the F2 of /ʌ/ and F1 of /o/ appear to move in tandem. Lastly, this study suggests that the reason the vowel changes differ across gender and regional dialects could be because they are all converging on to the standard Korean.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.842-851
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• 2005

In this paper, a new method for constrained optimization of noisy functions is proposed. In approximate optimization using response surface methods, if constraints have severe noise, the approximate feasible region defined by approximate constraints is apt to include some of the infeasible region defined by actual constraints. This can cause the approximate optimum to converge into the infeasible region. In the proposed method, the approximate optimization is performed with the approximate constraints shifted by their deviations, which are calculated using a diagonal quadratic response surface method. This can prevent the approximate optimum from converging into the infeasible region. To fit the objective and constraints into diagonal quadratic models, we select the center and 4 additional points along each axis of design variables as experimental points. The deviation of each function is calculated using the differences between the real and approximate function values at the experimental points. A sequential approximate optimization technique based on the trust region algorithm is adopted to manage approximate models. The proposed approach is validated by solving some design problems. The results of the problems show the effectiveness of the proposed method.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.3
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• pp.300-310
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• 1999

A constant-volume combustion chamber is developed to measure the burnt gas temperature over the wide ranges of equivalence ratio from 1.5 to 2.7 and pressure from 0.1 to 2.7 and pressure from 0.1 to 6 MPa by two-color method. The combustion temperature is also calculated by the conventional two-region model. The premixed fuel rich propane-oxygen-inert gas mixtures under high pressures are simultaneously ignited by eight spark plugs located on the circumference of combustion chamber with 45 degree intervals. The eight converging flames compress the end gases to high pressures. The transmissiv-ity in the chamber center during the final stage of combustion at the highest pressure is measured by in situ laser extinction method. Comparisons are made with the combustion temperatures between two-color method and two-region model. It is found that the burnt gas temperature mea-sured by two-color method is higher than that calculated by two-region model because of being the negative temperature gradient on the calculation and the temperature distribution of light path-length on the measurement and the burnt gas temperature for the turbulent combustion is higher than that of the laminar combustion under the same conditions because the heat loss for turbulent combustion is lower due to the shorter combustion period.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.43-54
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• 1999

The effects of equivalence ratio and pressure on burnt gas temperature in premixed fuel rich propane-oxygen-inert gas combustion are investigated over the wide ranges of equivalence ration from 1.5 to 2.7 and pressure from 0.1 to 7 MPa by using a specially designed disk -type constant-voume combustion chamber, The premixtures are simultaneously ignited by eight spark plugs located on the circumference of combustion chamber with 45 degree interals. The eight converging flames compress the end gases to high pressures. The burnt gas temperature is meausured by the nmodifie dtow-colr pyrometry method. The transmissivity in the chamber center during the final stage of combustion at the hightest pressure is meausred by in situ laser extinction method. It is found that a temperature difference between the burnt gas temperature measured by mofidied and conventrational two-color method is 10 to 20 K, but the accuracy of the modified two-color methdo is higher if the local transmissivity in observed region is uniform , and the combustion at higher pressures results gas density conditions and the burnt gas temperature increases as the volume fraction of argon is increased because the specific heat of argon is lower compared to that of nitrogen with a constant equivalence ratio.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.823-826
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• 2002

Experiments were conducted to show the characteristics of the flow on unventilated parallel plane jets. Measurements of mean velocity components and turbulent intensities were carried out with a particle image velocimetry. The measurements range of these experiments was Reynolds number of 5300 based on the nozzle width and the cases of nozzle-to-nozzle distance were 4, 6, 8, and 10 times the width of the nozzle. Results show that a recirculation zone with a sub-atmospheric static pressure was bounded by the inner shear layers of the individual jets and the nozzles plate. The positions, where maximum value of mean turbulent intensities and mean turbulent kinetic energy show, were at the same position with the merging point. The spread of jets in the merging region increases more rapidly than that of jets in the converging and the combined region. As nozzle-to-nozzle distances were increased, it was shown that merging and combined lengths were shorter.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.428-433
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• 1993

The second harmonic of Q-switched Nd:YAG laser beam with gaussian mode is cut off by pinhole of a certain radius and its central portion passed through pinhole is focused by converging lens. It is confirmed that the shape of this beam in focal region is central symmetric but non-gaussian. Change of transmittance due to self-focusing is investigated by scanning (z-scan) $CS_2$ of 1 mm thickness in the focal region. It is found that the observed results can be consistently explained by Fresnel theory within 1.5% accuracy and efficiency of self-focusing depends on spatial shape of incident beam.