• Journal of environmental and Sanitary engineering
• /
• v.13 no.3
• /
• pp.72-78
• /
• 1998

For investigation into gas permeation characteristics, the porous alumina membrane with asymmetrical structure, having upper layer with 10 nanometer under of pore diameter and lower layer with 36 nanometer of pore diameter, was prepared by anodic oxidation using DC power supply of constant current mode in an aqueous solution of sulfuric acid. The aluminium plate was pre-treated with thermal oxidation, chemical polishing and electrochemical polishing before anodic oxidation. Because the pore size depended upon the electrolyte, electrolyte concentration, temperature, current density, and so on, the the membranes were prepared by controling the current density, as a very low current density for upper layer of membrane and a high current density for lower layer of membrane. By control of current quantity, the thicknesses of upper layer of membranes were about $6{\;}{\mu}m$ and the total thicknesses of membranes were about $80-90{\;}{\mu}m$. We found that the mechanism of gas permeation depended on model of the Knudsen flow for the membrane prepared at each condition.

• Journal of the Korean Mathematical Society
• /
• v.36 no.2
• /
• pp.355-367
• /
• 1999

We prove the existence of 2N-1 distinct ordered positive solutions of a class of semilinear elliptic Dirichlet boundary value problems on Rn when the forcing term has N distinct positive stable zeros and the coefficient function decaying to the zero at infinity.

• The Korean Journal of Pain
• /
• v.1 no.1
• /
• pp.125-128
• /
• 1988

A case of the left stellate ganglion block (SGB) with a warm serration of the left lower extremity in a 25-year-old male soldier is presented. During the Korean War, this patient received a penetrating gun shot wound from the right knee through the left abdominal wall, left upper arm and left thumb. He was evacuated to the a marine corps surgical hospital where amputation of the left thumb and an end-to-end anatomosis of the left brachial artery were performed. After surgery, left ulnar and median nerve paralysis and causalgia developed and about 9 months later an upper thoracic ganglionectomy was proposed at the Chin-Hae Navel Hospital. Before the ganglionectomy a stellate ganglion block for diagnostic and prognostic purposes was requested by the surgeon. This block was performed by the supraclavicular anterior approach using 10 ml of 2% procaine. The effect of the block including Horner's syndrome was confirmed 5 minute later in this patient. This patient returned to the ward by walking unassisted 10 minutes after the block, and complained of a warm sensation in the left lower extremity 20 minutes later as well as the left upper arm. This warm sensation in the lower extremity following ipsilateral stellate ganglion block indicates that the local anesthetics solution injected tinto the neck spread down to lumbar sympathetic ganalgion along the fascial membrane of the sympathetic chain as a consequence of the 10 minutes walk.

• Journal of the Korean Mathematical Society
• /
• v.49 no.1
• /
• pp.153-164
• /
• 2012

In this paper, we study the existence, non-existence, and multiplicity of positive solutions for a coupled telegraph system using the xed-point theorem of cone expansion/compression type, the upper-lowe solutions method, and xed point index theory.

• ETRI Journal
• /
• v.15 no.3
• /
• pp.35-45
• /
• 1994

In this paper we develop an approximation formalism on the queue length distribution for general queueing models. Our formalism is based on two steps of approximation; the first step is to find a lower bound on the exact formula, and subsequently the Chernoff upper bound technique is applied to this lower bound. We demonstrate that for the M/M/1 model our formula is equivalent to the exact solution. For the D/M/1 queue, we find an extremely tight lower bound below the exact formula. On the other hand, our approach shows a tight upper bound on the exact distribution for both the ND/D/1 and M/D/1 queues. We also consider the $M+{\Sigma}N_jD/D/1$ queue and compare our formula with other formalisms for the $M+{\Sigma}N_jD/D/1$ and M+D/D/1 queues.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.1
• /
• pp.328-335
• /
• 1996

The one-dimensional flame analysis was carried out to understand the combustion phenomena in porous media. The downstream as well as upstream solution corresponding to upper and lower solutions could be obtained. While upper flame temperature gets higher, lower flame temperature gets lower, as the flame approaches the central part of the combustor. The reason why upstream flame and downstream flame exist at the same flow condition is that the regions where net heat recirculation is identical exist in upstream and downstream of the combustor. In order for the downstream flame to be stabilized, more heats needed to be recirculated towards upstream because of larger radiation loss of downstream flame.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.29 no.1
• /
• pp.140-151
• /
• 2001

This study based on the theoretical understanding of multi-layer planting which have engineering, ecological and landscape benefits, was conducted to find out the status of multi-layer planting in the apartment and neighborhood park in Seoul. This study was also aimed to seek for the problematic matters, and suggest a solution on the current multi-layer planting. The results of this study were as follows; 1) Since landscape woody plants have been classified just as tree and shrub in Korea, the classification for the multi-layer planting has been unreasonable, and landscape woody plants might have been classified as tree, sub-tree and shrub, or upper, middle, and lower-layer, It could be defined that upper layer is over eight meters in full growth, middle over 3-8 meters and lower under 3 meters. 2) In apartments, the upper layer consisted of eighteen species, the middle and lower layer seven species each. In neighborhood parks, the upper layer consisted of fifteen species, and the middle and lower layer five species each. 3) In terms of planting year of the surveyed areas, there were no differences in the number of species when planting year of the apartment was divided into two groups, the first half(1900-1995) and the second(1996-2000). But, in terms of individual occupation, the percentage was decreased in upper layer, while there was increasing in middle and lower layer. 4) As the result of survey of multi-layered area, it appeared that apartment was shown 0.65 percent and neighborhood park 0.61 percent of the planted area, which was less than 1 percentage of landscape architecturally planted area. 5) In apartment, the number of individual in middle layers has been increased in the first half and the second, but with respect to the correlation with multi-layered area, the apartments had the "$\rho$=0.208", saying that increasing middle layer was scattered planting instead of multi-layered planting. 6) In planting at the apartments in Korea, the planting density was limited, because the layer division was restricted to only tree and shrub. On the contrary, it was divided into upper, middle and lower tree in Japan. Therefore, in Korea, it should be classified as the planting density by dividing into tree, sub-tree, and shrubs, or upper, middle and lower tree by the law. And, it should be considered that the multi-layered planting has a proper organic relation as well as the planting density.g density.

• Communications of the Korean Mathematical Society
• /
• v.22 no.1
• /
• pp.53-64
• /
• 2007

In this paper, we apply the generalized quasilinearization technique to a forced Duffing equation with three-point mixed nonlinear nonlocal boundary conditions and obtain sequences of upper and lower solutions converging monotonically and quadratically to the unique solution of the problem.

• Journal of electromagnetic engineering and science
• /
• v.1 no.2
• /
• pp.156-160
• /
• 2001

Very convenient equivalent circuits fur the design of bandpass filters with an attenuation pole in the lower or upper stopband are provided together with necessary closed-form solutions. The proposed approach gives us much flexibility and simplifies the design of inserting attenuation poles.

• Journal of the Society of Naval Architects of Korea
• /
• v.54 no.6
• /
• pp.461-469
• /
• 2017

A segment of the wave board has been expressed as a submerged line segment in the two dimensional wave flume. The lower end of the line segment could be extended to the bottom of the wave flume and the other opposite upper end of the board could be extended to the free surface. It is assumed that the motion of the wave board could be defined by the sinusoidal motion in horizontal direction on either end of the wave board. When the amplitude of sinusoidal motion of the wave board on lower and upper end are equal, the wave board motion could express the horizontally oscillating submerged segment of piston type wave generator. The submerged segment of flap type wave generator also could be expressed by taking the motion amplitude differently for the either end of the board. The pivot point of the segment motion could play a role of hinge point of the flap type wave generator. Simplified analytic solution of oscillating submerged wave board segment in water of finite depth has been derived through the first order perturbation method at two dimensional domain. The case study of the analytic solution has been carried out and it is found out that the solution could be utilized for the design of wave generator with arbitrary shape by linear superposition.