• 환경영향평가
• /
• 제21권1호
• /
• pp.1-13
• /
• 2012

We diagnosed on status and problems of environmental assessment regarding development of offshore wind power, and also on reasonable core assessment items. Most of the coastal wind power are located on the western coastline of Korea and Jeju Island. In the selections of the site for the offshore wind farms, a previous investigations should be conducted with regard to distances from the land, stabilities from external forces (tide, wave, etc.) and topographical changes, and characteristics of the surroundings (distributions of protected area, fishing ground, artificial seagrasses, and shipping traffic). It is needed to assess dispersion of suspended solids, changes of the sea bottom, and impacts on fisheries resources and fishing activities under construction of offshore wind power. Furthermore, the responses of marine organisms to noise and vibration, impacts by electromagnetic fields, impacts on sea birds, hindrances to sea lane routes, and damaged scenery and marine protection areas are thoroughly assessed during operation processes. The consultation criteria in case of development of offshore wind farm is adjusted by focusing marine environmental impact assessment.

• 한국지진공학회논문집
• /
• 제7권4호
• /
• pp.71-79
• /
• 2003

사장교에서 케이블은 교량 전체에 있어서 매우 중요한 요소이다. 차량, 바람 혹은 풍우에 의한 케이블의 진동은 교량의 안전성과 사용성을 감소시키는 주요 원인이 되어왔으며 이러한 문제를 해결하는 효과적인 방법중의 하나는 케이블 댐퍼를 설치하는 것이다. 이 케이블 댐퍼를 최적으로 설계하기 위해서는 케이블의 동특성을 정확하게 평가해야 하며 케이블 동특성치를 얻기 위해서는 정확한 가진이 필요하다. 따라서 본 연구에서는 케이블 가진시스템을 개발하고 성능을 평가하기 위해 케이블 가진시스템의 운동방정식을 유도하였으며, 케이블 가진기를 케이블 모형에 설치하여 정현진동실험과 공진진동실험을 수행하여 케이블의 동특성을 효과적으로 구하였다.

• Advances in aircraft and spacecraft science
• /
• 제3권3호
• /
• pp.243-257
• /
• 2016

The increase of air traffic volume has brought an increasing amount of issues related to carbon and NOx emissions and noise pollution. Aircraft manufacturers are concentrating their efforts to develop technologies to increase aircraft efficiency and consequently to reduce pollutant discharge and noise emission. Ultra High By-Pass Ratio engine concepts provide reduction of fuel consumption and noise emission thanks to a decrease of the jet velocity exhausting from the engine nozzles. In order to keep same thrust, mass flow and therefore section of fan/nacelle diameter should be increased to compensate velocity reduction. Such feature will lead to close-coupled architectures for engine installation under the wing. A strong jet-wing interaction resulting in a change of turbulent mixing in the aeroacoustic field as well as noise enhancement due to reflection phenomena are therefore expected. On the other hand, pressure fluctuations on the wing as well as on the fuselage represent the forcing loads, which stress panels causing vibrations. Some of these vibrations are re-emitted in the aeroacoustic field as vibration noise, some of them are transmitted in the cockpit as interior noise. In the present work, the interaction between a jet and wing or fuselage is reproduced by a flat surface tangential to an incompressible jet at different radial distances from the nozzle axis. The change in the aerodynamic field due to the presence of the rigid plate was studied by hot wire anemometric measurements, which provided a characterization of mean and fluctuating velocity fields in the jet plume. Pressure fluctuations acting on the flat plate were studied by cavity-mounted microphones which provided point-wise measurements in stream-wise and spanwise directions. Statistical description of velocity and wall pressure fields are determined in terms of Fourier-domain quantities. Scaling laws for pressure auto-spectra and coherence functions are also presented.

• Smart Structures and Systems
• /
• 제6권5_6호
• /
• pp.461-480
• /
• 2010

This paper analyses the data collected from the $2^{nd}$ Jindo Bridge, a cable-stayed bridge in Korea that is a structural health monitoring (SHM) international test bed for advanced wireless smart sensors network (WSSN) technology. The SHM system consists of a total of 70 wireless smart sensor nodes deployed underneath of the deck, on the pylons, and on the cables to capture the vibration of the bridge excited by traffic and environmental loadings. Analysis of the data is performed in both the time and frequency domains. Modal properties of the bridge are identified using the frequency domain decomposition and the stochastic subspace identification methods based on the output-only measurements, and the results are compared with those obtained from a detailed finite element model. Tension forces for the 10 instrumented stay cables are also estimated from the ambient acceleration data and compared both with those from the initial design and with those obtained during two previous regular inspections. The results of the data analyses demonstrate that the WSSN-based SHM system performs effectively for this cable-stayed bridge, giving direct access to the physical status of the bridge.

• International Journal of Computer Science & Network Security
• /
• 제21권6호
• /
• pp.11-16
• /
• 2021

At the present time, the number of accidents has enlarged speedily and in country like India per day there are about 204 accidents occurred. Accidents of two-wheeler compose a foremost segment of every accident and it can be true for the reason that two-wheelers like bikes not able to produce as many as security measurements normally incorporated in cars, truks and bus etc. General main rootcost of the two-wheeler accidents happen only when people community not remember to wearing a device helmet and during the driving time feels like sleep condition, alcohol disbursement, many of the drivers doesn't know heavy vehicles like Loory and buses approaching into very closer to their two wheelers, contravention of two wheelers in traffic rules and regulations. Let's overcome the above situations; our important objective is to develop an intelligent system device that can successfully facilitate in avoidance of every kind of problems. Suppose any of the above stated situations occurs, at that moment how system device identify and represents the commanders and community, and finally the stated situation be able to taken care of straight away without any further delay. A smart intelligent helmet system is a defending head covering used by rider for making bike riding safer than earlier. This is finished by incorporating sophisticated features like detecting the usage of helmet by the rider, connected Bluetooth module in helmet. In order to maintain the temperature inside the helmet device we need to include CPU fan module inside the device. RF based helmet prevents road accidents and identify whether people community is not using a component helmet or used. Main responsibility of the system is to detect accidents by vibration sensors, accelerometers and also with the help of modules global positioning system and global system for mobile commnicaiton module. A wireless communication device used to discover the accident area site location and likewise notifying the two-wheeler drived people's relatives and short message text information passed to the positioned hospitals.

• 한국지반환경공학회 논문집
• /
• 제18권4호
• /
• pp.13-21
• /
• 2017

자갈궤도는 100여년 이상 전세계적으로 널리 사용되는 궤도구조로 저렴한 초기 건설비용, 유연한 유지보수와 진동 및 소음의 저감효과가 있지만, 열차운행에 따라서 지속적인 침하가 발생하는 단점이 있다. 이로 인해 지속적인 유지보수가 필요하며, 최근 열차의 속도, 용량, 중량의 증가로 유지보수비용이 증가하고 있는 실정이다. 파울링(fouling)은 노반 세립분이나 자갈입자가 파쇄되면서 발생한 세립분이 자갈 사이의 공극을 메우는 현상으로 배수가 나빠지고, 자갈궤도의 침하를 가속화시키는 등 자갈도상의 열화의 주원인으로 지목되고 있다. 본 논문에서는 GPR(Ground Penetrating Radar)을 이용하여, 도상의 상태를 평가 할 수 있는 분석방법을 제안하였다. 경험에 의존하는 기존의 분석기법을 대신하여, 고속선에 사용되는 자갈의 감쇠 특성을 반영한 이득함수(gain function)를 제안하였다. 실내 박스 실험과 실모형 실험을 통해 제안한 이득함수로 증폭한 GPR신호에 힐버트 변환을 추가로 적용하여 자갈층과 노반층에서 반사된 신호의 세기변화를 깊이에 따라 계산하였다. 이로부터 신호의 세기가 비교적 크게 변화하는 곳을 파울링층과 노반층의 경계로 구분할 수 있었다. 다만 현장적용을 위해서는 침목의 영향을 분리하고 전자기파 분산특성 등에 대한 추가 연구가 필요할 것으로 사료된다.

• Asian Journal of Atmospheric Environment
• /
• 제12권2호
• /
• pp.109-126
• /
• 2018

This paper presents seasonal variation of $PM_{10}$ over five urban sites in Sabah, Malaysia for the period of January through December 2012. The variability of $PM_{10}$ along with the diurnal and weekly cycles of CO, $NO_2$, $SO_2$, and $O_3$ at Kota Kinabalu site were also discussed to investigate the possible sources for increased $PM_{10}$ concentration at the site. This work is crucial to understand the behaviour and possible sources of $PM_{10}$ in the urban atmosphere of Sabah region. In Malaysia, many air pollution studies in the past focused in west Peninsular, but very few local studies were dedicated for Sabah region. This work aims to fill the gap by presenting the descriptive statistics on the variability of $PM_{10}$ concentration in the urban atmosphere of Sabah. To further examine its diurnal and weekly cycle pattern, its responses towards the variations of CO, $NO_2$, $SO_2$, and ozone were also investigated. The highest mean value of $PM_{10}$ for the whole study period is seen from Tawau ($35.7{\pm}17.8{\mu}g\;m^{-3}$), while the lowest is from Keningau ($31.9{\pm}18.6{\mu}g\;m^{-3}$). The concentrations of $PM_{10}$ in all cities exhibited seasonal variations with the peak values occurred during the south-west monsoons. The $PM_{10}$ data consistently exhibited strong correlations with traffic related gaseous pollutants ($NO_2$, and CO), except for $SO_2$ and $O_3$. The analysis of diurnal cycles of $PM_{10}$ levels indicated that two peaks were associated during the morning and evening rush hours. The bimodal distribution of $PM_{10}$, CO, and $NO_2$ in the front and at the back of ozone peak is a representation of urban air pollution pattern. In the weekly cycle, higher $PM_{10}$, CO, and $NO_2$ concentrations were observed during the weekday when compared to weekend. The characteristics of $NO_2$ concentration rationed to CO and $SO_2$ suggests that mobile sources is the dominant factor for the air pollution in Kota Kinabalu; particularly during weekdays.

• 한국터널지하공간학회 논문집
• /
• 제21권3호
• /
• pp.347-362
• /
• 2019

도심지 터널 공사가 많아지면서 이에 따른 소음, 진동, 교통불편 및 민원 저감을 위해 TBM 굴착이 증가하고 있다. 그러나 이러한 추세에도 불구하고 국내 TBM 공동구 설계 및 시공을 위한 기준들은 대부분 해외기술(일본, 독일 등)을 이용하고 있어 국내환경을 고려하지 못하고 있다. 특히, 공동구 TBM 설계의 주요 기준이 되는 굴진율은 대부분 일축압축강도만으로 산정되며 이마저도 실제 현장 특성과 맞지 않아 개선이 필요하다. 본 연구에서는 국내 현장에 적합한 굴진율을 예측하기 위해 수행되었다. 이를 위해 시공 중인 소단면 쉴드 TBM 굴착 현장의 지반 및 굴진데이터를 수집하고 상관관계 분석을 통해 굴진율에 영향을 미치는 주요인자를 파악하였다. 도출된 영향인자들은 통계적 분석기법을 기반으로 한 다중선형 회귀분석에 적용되어 굴진율을 예측하는 회귀식의 예측변수로 이용되었다. 결과적으로 회귀분석을 통해 도출된 회귀식은 일축압축강도와 절리간격을 예측변수로 추정되었으며, 해외 경험식과 비교하여 국내현장 굴진율의 예측 정확도가 높은 것으로 나타났다. 다만, 이 회귀식을 타 국내 현장에 적용할 경우 예측오차가 다소 증가하였다. 회귀식이 갖는 이와 같은 적용 한계를 개선하기 위해서는 추가적인 연구를 통해 현장조건에 제약을 받지 않는 굴진율 예측모델 도출이 필요할 것으로 보인다.