• KDI Journal of Economic Policy
• /
• 제14권4호
• /
• pp.27-49
• /
• 1992

본호(本鎬)는 지난 몇년간 우리나라 주가(株價) 및 지가(地價)의 급변을 거품현상(現象)으로 해석하는 견해(見解)를 재검토(再檢討)하고 시장기본요인(市場基本要因)의 중요성을 강조하고자 하였다. 자산가격변화(資産價格變化)에 대한 자기실현적(自己實現的) 예측(豫測)에 바탕을 둔 거품이론(理論)으로 최근 우리나라의 주가(株價) 및 지가변동(地價變動)을 설명하기에는 여러가지 제약점이 있다. 지난 몇년간 우리나라 주가(株價) 및 지가(地價)의 급변을 거품현상이라고 주장하는 사람들은 거품의 존재유무(存在有無)에 대한 검증 없이 막연하게 자산가격의 급변 내지는 불규칙한 변동을 거품현상으로 해석하는 경향이 있으며 주가(株價) 및 지관(地慣)의 거품검증을 시행한 경우에도 검증과정에서 여러가지 계량경제학적(計量經濟學的) 문제점을 보이고 있고, 근본적으로는 검증모형(檢證模型)이 잘못 구체화되었다는 오특정(誤特定)(misspecification)의 문제를 안고 있다. 본고(本稿)에서는 지난 몇 년간 우리나라 지가(地價) 및 주가변화(株價變化)를 3저여건(低與件)의 도래와 퇴조에 따른 경제여건의 변화와 시장기본요인의 변화로 설명할 수 있음을 보였다. 우선 실질금리(實質金利), 성장율(成長率) 등 시장기본요인(市場基本要因)의 변화로 우리나라 주가 및 지가변화를 상당부분 설명할 수 있었으며, 다음으로는 이부문(二部門) 일반균형(一般均衡) 자산구성모형(資産構成模型)을 구성하여 유동성(游動性) 및 환율(換率)이 변화할 때 지가(地價)의 과잉변동현상(過剩變動現像)이 발생함을 보였다. 1986~89년간 지가(地價)의 급등(急騰)은 동(同) 기간중(期間中) 엔화절상(貨切上), 원화절상(貨切上) 및 유동성증가(流動性增加)(실질금리(實質金利)의 하락(下落))에 따른 것이며, 90년 이후 지가상승세(地價上昇勢)의 둔화(鈍化)는 동(同) 기간중(期間中) 엔화절하(貨切下), 원화절하(貨切下)로의 반전 및 유동성압박(流動性壓迫)에 따른 실질금리(實質金利)의 상승(上昇)과 밀접히 관련되어 있다.

• 상하수도학회지
• /
• 제27권2호
• /
• pp.261-272
• /
• 2013

Algae boom (Red tide) in south coastal area of Korea has been appeared several times during a decade. If algae boom appears in the desalination plant, media filter and UF filter are clogged quickly, and the plant should be shutdown. In general, Algae can be removed from water by flotation better than by sedimentation, because of the low density of algal cell. The purpose of this study conducts the CFD simulation of DAF flotation basin to apply the design of the dissolved air flotation with ball filter in the Test Bed for SWRO desalination plant. In this study, Eulerian-Eulerian multiphase model was applied to simulate the behavior of air bubbles and seawater. Density difference model and gravity were used. But de-sludge process and mass transfer between air bubbles and seawater were ignored. Main parameter is hydraulic loading rate which is varied from 20 m/hr to 27.5 m/hr. Geometry of flotation basin were changed to improve the DAF performance. According to the result of this study, the increase of hydraulic loading rate causes that the flow in the separation basin is widely affected and the concentration of air is increased. The flow pattern in the contact zone of flotation basin is greatly affected by the location of nozzle header. When the nozzle header was installed not the bottom of the contact zone but the above, the opportunity of contact between influent and recycle flow was increased.

• 한국식품저장유통학회지
• /
• 제16권3호
• /
• pp.321-326
• /
• 2009

마이크로버블을 이용한 세척시간과 세척방법에 따라 처리한 상추의 세척효과와 저장 중 품질 변화를 살펴본 결과는 다음과 같다. 세척시간 설정을 위한 실험을 통해 마이크로버블로 1, 3, 5분간 세척하여 미생물변화, 관능검사, 세척된 정도를 측정한 결과 5분간 처리한 시료가 가장 좋은 결과를 나타냈다. 세척방법에 따라 전처리한 상추의 미생물 변화는 세척처리 한 직후 무세척(CT)구는 4.30 log CFU/g, 손세척(HW)구는 4.10 log CFU/g, 일반버블세척(BW)구는 3.98 log CFU/g, 마이크로버블세척(MW)구는 3.25 log CFU/g에서 저장 10일째에는 무세척(CT)구는 7.00log CFU/g, 손세척(HW)구는 6.19 log CFU/g, 일반버블세척(BW)구는 6.02 log CFU/g, 마이크로버블세척(MW)구는 5.89 log CFU/g로 마이크로버블처리구가 가장 적은 변화를 보였다. 관능검사에서는 일반버블세척(BW)구와 마이크로버블세척(MW)구가 무세척(CT)구와 손세척(HW)구보다 유의적으로 높게 평가되었으며, 일반버블세척(BW)구와 마이크로버블세척(MW)구는 유의적 차이를 보이지 않았다. 또한 잔류농약시험에서도 마이크로버블을 이용한 처리구가 대조구 보다 2-3배정도 제거효과를 보였다. 상추의 세척상태를 측정한 결과 손세척구와 일반버블처리구은 완전히 깨끗하게 세척되지 못한 반면 마이크로버블처리구는 이물질이 보이지 않아 세척효과가 큰 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2015년도 추계 학술논문 발표대회
• /
• pp.141-142
• /
• 2015

This literature study is focused on the improvement of lightweight concrete in perspective of foaming agent. Lightweight concrete is the cured concrete as putting required amount of foaming agent to slurry which is a mixture of a certain amount of cement, sand, and water. It has lower density than general concrete, because foaming agent disintegrates numerous bubbles evenly and independently. Thus, it is capable of lightening the weight and great for sound absorption and insulation, In foreign countries, studies for structural lightweight concrete mainly of tunnel grouting and weight lightening of heavy structures are going along actively. Domestically, exterior panel and ALC blocks are alternatively used for flooring. Therefore, this research consider improvement of lightweight concrete in perspective of foaming agent with foundation study.

• 한국전산유체공학회지
• /
• 제7권3호
• /
• pp.44-52
• /
• 2002

An analytic methodology was developed for free surface motions between liquid metal coolant and cover gas in order to calculate the phenomena of gas entrainment in hot pool surface through IHX EMP and reactor core. The methodology was setup by applying the first order VOF convection model to CFX4 general purpose fluid dynamics analysis code. The methodology was validated by applying it to an experimental apparatus designed for free surface motions of KALIMER reactor. The distributions of free surface calculated by the present methodology were almost coincident with the experimental data. The developed methodology was applied to the KALIMER reactor of full power operating condition. The shapes of the free surface were nearly uniform. From the results, it was found that the altitude of the free surface from the IHX inlet nozzle of KALIMER reactor is high enough not to affect to free surface motions of generating gas bubbles from the turbulent shear flows such as hydraulic jump and water falls.

• 설비공학논문집
• /
• 제15권4호
• /
• pp.268-273
• /
• 2003

In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. An electro-conductivity probe was used to measure local volume fraction and bubble frequency. Since the gas is concentrated at the near nozzle, the flow parameters are high near the nozzle. In general their axial and radial values tended to decrease with increasing distance. For visualization of flow characteristics, a Particle Image Velocimetry (P.I..V) and a thermo-vision camera were used in the present study. The experimental results show that heat transfer from bubble surface to water is largely completed within z=10mm from the nozzle, and then the temperature of bubble surface reaches that of water rapidly. Due to the centrifugal force, the flow was more developed near the wall than at bubble-water plume. Vortex flow in the bottom region was relatively weaker than that in the upper region.

• Progress in Superconductivity
• /
• 제3권2호
• /
• pp.247-251
• /
• 2002

In general, the bubbling, generated during the fabrication of the tapes, breaks the superconducting filament, and critical current of the tapes will be decreased. Heat-treatment schemes of Bi-2223/Ag HTS tapes were modified, such as pre-annealing of multi-stacked billet, 2-step main sintering and ramp rate etc. The generation of bubbling was drastically decreased from 20 bubbles/m to 0 ~ 1 bubble/m by the modified heat-treatment. Therefore, the value of critical current of the tapes without bubbling was increased almost twice higher than that of already existing tapes. Critical current up to 42 A in 40 m length Bi-22231Ag tapes have been measured at 77K, self-field, 1$mutextrm{V}$/cm criterion. It could be confirmed that elimination of bubbling is effective to maintain the superconducting property along the tape length.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제13권1호
• /
• pp.44-50
• /
• 2005

In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. An electro-conductivity probe was used to measure local volume fraction and bubble frequency. Since the gas was concentrated at the near the nozzle, the flow parameters were high near the nozzle. In general their axial and radial values tended to decrease with increasing distance. For visualization of flow characteristics, a Particle Image Velocimetry (PIV) and a thermo-vision camera were used in the present study. The experimental results showed that heat transfer from bubble surface to water was largely completed within z = 10 mm from the nozzle, and then the temperature of bubble surface reached that of water rapidly. Due to the centrifugal force, the flow was more developed near the wall than at bubble-water plume. Vortex flow in the bottom region was relatively weaker than that in the upper region.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 추계학술대회 논문집
• /
• pp.830-839
• /
• 2008

This study is designed to manufacture the upgraded sound absorption concrete by using foamed concrete by using artificial light weight aggregate which raises the continuous void ratio to increase the sound absorption ratio and improve the strength. In manufacturing the sound absorption block, the pre-foaming form is applied to generate continuous voids, controlling the density by the addition of bubbles. It is general that the more porosity creates, the weaker strength becomes. Each of specimens are used for this experiment and measured their absorption ratio to examine the absorption property depending on frequency. As a results of experiment, it is evaluated that the absorption capacity of the sound absorption block has relation to compression strength and surface shape.

• 한국재료학회지
• /
• 제32권4호
• /
• pp.223-229
• /
• 2022

A porous photocatalyst concrete filter was successfully produced to remove NOx, by mixing TiO₂ photocatalyst with lightweight aerated concrete. Ultra Fine Bubbles were used to form continuous pores inside the porous photocatalytic concrete filter, which was mixed via a bubble generation experiment. The optimal mixing condition was determined to be with 4 % of the bubble generation agent B. NO removal specimens were prepared for various photocatalytic loading conditions, and the specimen containing 3 % P-25 removed NO at a concentration of 1.03 µmol in 1 h. The NO removal rate of the porous photocatalytic concrete filter prepared in this study was 10.99 %. This photocatalytic filter performance was more than 9 times the amount of NO removed by a general photocatalytic filter. The porous photocatalyst concrete filter for removing NOx developed in this study can be applied to various construction sites and the air quality can be solved by reducing NOx contributing to the formation of fine particles.