• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.1335-1336
• /
• 2007

Among the emerging non-volatile memory technologies, phase change memories are the most attractive in terms of both performance and scalability perspectives. Phase-change random access memory(PRAM), compare with flash memory technologies, has advantages of high density, low cost, low consumption energy and fast response speed. However, PRAM device has disadvantages of set operation speed and reset operation power consumption. In this paper, we investigated scalability of $Ge_{1}Se_{1}Te_{2}$ chalcogenide material to improve its properties. As a result, reduction of phase change region have improved electrical properties of PRAM device.

• 환경영향평가
• /
• 제21권5호
• /
• pp.757-765
• /
• 2012

The purpose of this study was to estimate the spatial-temporal NPP(Net Primary Productivity) and SCS(Soil Carbon Storage) of forest ecosystem under climate change in the capital area of South Korea using Mapss-Century1 (MC1), one of Dynamic Global Vegetation Models (DGVMs). The characteristics of the NPP and SCS changes were simulated based on a biogeochemical module in this model. As results of the simulation, the NPP varies from 2.02 to 7.43 tC $ha^{-1}\;yr^{-1}$ and the SCS varies from 34.55 to 84.81 tC $ha^{-1}$ during 1971~2000 respectively. Spatial mean NPP showed a little decreasing tendency in near future (2021~2050) and then increased in far future (2071~2100) under the condition of increasing air temperature and precipitation which were simulated by the A1B climate change scenario of Intergovernmental Panel on Climate Change (IPCC). But it was estimated that the temporal change of spatial mean NPP indicates 4.62% increasing tendency in which elevation is over 150m in this area. However, spatial mean SCS was decreased in the two future periods under same climate condition.

• Advances in environmental research
• /
• 제9권2호
• /
• pp.97-107
• /
• 2020

The indiscriminate growth in global population poses a threat to the world in handling and disposal of Municipal solid waste. Rapid urban growth increases the production, consumption and generation of Municipal solid waste which leads to a drastic change in the environment. The methane produced from the Municipal Solid waste accounts for up to 11% global anthropogenic emissions, which is a major cause for global warming. This study reports the methane emission estimation using IPCC default, TNO, LandGEM, EPER and close flux chamber from open dump yards at Perungudi and Kodungaiyur in Chennai, India. The result reveals that the methane emission using close flux chamber was in the range of 8.8 Gg/yr-11.3 Gg/yr and 6.1Gg/yr to 9.1 Gg/yr at Kodungaiyur and Perungudi dump yard respectively. The per capita waste generation was estimated based on waste generation and population. The waste generation potential was projected using linear regression model for the period 2017-2050. The trend of CH₄ emission in the actual field measurement were increased every year, similarly the emission trend also increased in IPCC default method (mass balance approach), EPER Germany (zero order decay model) where as TNO and Land GEM (first order decay model) were decreased. The present study reveals that Kodungaiyur dump yard is more vulnerable to methane emission compared to Perungudi dump yard and has more potential in waste to energy conversion mechanisms than compare to Perungudi dump yard.

• 한국기후변화학회지
• /
• 제1권1호
• /
• pp.21-30
• /
• 2010

본 연구에서는 홍수, 가뭄, 물관리 등 수자원 분야 취약성을 규준(criteria) 및 지표(indicators)를 활용하여 평가하는 방법을 제시하였다. 제시된 방법을 통해 전국 및 지역 단위의 취약성 평가를 실시하였다. 또한, 평가 규모별 적정 유역 크기에 대한 방안도 아울러 제시하였다. 수자원 취약성 평가에 이용한 규준은 크게 평가 대상지의 민감도, 기후에의 노출, 기후변화에 대한 적응력으로 분류할 수 있으며, 각 규준을 지표로 계량화 및 표준화하여 취약성 평가에 반영한다. 기후변화에 대한 수자원 분야의 취약성은 일반적으로 시간이 갈수록 증가하는 것으로 평가되었다. 평가 대상지의 유역 규모는 국가 차원의 취약성 평가는 대유역을 기준으로 설정하는 것이 유의하며, 지역 차원의 평가는 소유역을 기준이 적절함을 알 수 있었다.

• Wind and Structures
• /
• 제20권2호
• /
• pp.169-189
• /
• 2015

To investigate the effects of "sudden change" of wind fluctuations on vehicle running performance, which is caused by the artificial discrete simulation of wind field, a three-dimensional vehicle model is set up with multi-body dynamics theory and the vehicle dynamic responses in crosswind conditions are obtained in time domain. Based on Hilbert Huang Transform, the effects of simulation separations on time-frequency characteristics of wind field are discussed. In addition, the probability density distribution of "sudden change" of wind fluctuations is displayed, addressing the effects of simulation separation, mean wind speed and vehicle speed on the "sudden change" of wind fluctuations. The "sudden change" of vehicle dynamic responses, which is due to the discontinuity of wind fluctuations on moving vehicle, is also analyzed. With Principal Component Analysis, the comprehensive evaluation of vehicle running performance in crosswind conditions at different simulation separations of wind field is investigated. The results demonstrate that the artificial discrete simulation of wind field often causes "sudden change" in the wind fluctuations and the corresponding vehicle dynamic responses are noticeably affected. It provides a theoretical foundation for the choice of a suitable simulation separation of wind field in engineering application.

• Water Engineering Research
• /
• 제1권4호
• /
• pp.267-277
• /
• 2000

This study reports an examination of the sensitivity of water resources in the Keum River basin to climate change. Assuming a doubling in $CO_2$ concentrations, a cooperative study provided four climate change scenarios for this study, which have been translated into temperature and precipitation scenarios on a basin scale. The study utilized these temperature and precipitation data for each climate change scenario as inputs to the NWS-PC model to generate the corresponding streamflow scenario over the Keum River basin. A reservoir simulation model for the Dae-Chung Dam in the Keum River basin has been developed with an object-oriented simulation environment, STELLA. For each streamflow scenario, the performance of the reservoir was assessed in terms of reliability, resiliency, and vulnerability. Although the simulation results are heavily dependent on the choice of the climate change scenarios, the following conclusions can be clearly concluded: (1) the future streamflow over the Dae-Chung Dam tends to decease during the dry period, which seriously increases competitive water use issues and (2) flood control issues predominate under the $2CO_2$-High case.

• Korean Journal of Acupuncture
• /
• 제26권3호
• /
• pp.1-11
• /
• 2009

Objectives : The object of this study is to investigate the balance/imbalance of skin capacitances between left and right meridians, and to analyze the change patterns of electric energy on meridians with the lapse of time. Method : Electric potential was measured on five source points (LU9, PC7, HT7, LI4, SI4) bilaterally for 4 hours. The energy balance/imbalance between left and right was investigated, and the change patterns with time were analyzed. Results and Conclusions : The amplitude of meridian energy on five source points and the energy balance/imbalance between left and right were varied in each individual. When a source point showed a balanced meridian energy bilaterally, the change patterns of meridian energy with time were similar between left and right. While, when it showed an imbalanced energy between left and right, the change patterns of meridian energy were also different between left and right. Through this study, we proposed a new diagnostic method of meridian energy.

• 대한원격탐사학회지
• /
• 제33권6_2호
• /
• pp.1075-1087
• /
• 2017

본 연구에서는 위성영상에 대한 변화탐지 기법의 결과를 토지피복지도 갱신의 기초자료로 활용하고자 하였다. $S^2CVA$(Sequential Spectral Change Vector Analysis) 기법을 다시기 다중분광 위성영상에 적용하여 해당 지역 내의 변화지역을 추출하였다. 특히, 분광변화벡터의 방향정보를 이용하여 계절적 변화에 의한 변화지역의 오탐지를 최소화하고자 하였다. 변화탐지 결과인 이진영상은 구역통계를 활용하여 토지 피복도와 함께 통합하였으며, 토지피복지도 갱신을 위하여 객체 기반의 분석을 수행하였다. PlanetScope 자료와 환경부의 토지피복지도를 이용한 실험결과, 토지피복지도 내에 변화된 지역을 효과적으로 탐지할 수 있음을 확인하였다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.276-279
• /
• 2003

The phase change upon reflection from target surfaces in white-light interferometer induces measurement errors when target surfaces are composed of dissimilar materials. We prove that this phase change on reflection considered of the polarization of the white-light causes the shift of both envelope peak position and fringe peak position of several tens of nanometer. In addition, we propose a new equation of white-light interference fringe pertinent to the polarization of source.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2009년도 춘계학술대회 논문집
• /
• pp.107-108
• /
• 2009

This study is focused on the thickness change in burring with stainless 409L according to the change of main design variables and forming conditions, to manufacture the automobile exhaust flange. Large plastic deformations by burring process decreases thickness of inner radius and occurs cracks. The optimal design of performs by the finite element analysis achieves adequate improvement of thickness decrease.