• Journal of Korea Water Resources Association
• /
• v.41 no.4
• /
• pp.445-454
• /
• 2008

Many countermeasures for local scour at bridge piers constructed on the river and sea have been developed and researched to protect piers against local scour. The most commonly employed method is riprap protection, which is sometimes required the filter installation between riprap and base layers. However, the construction of stone filters are really hard to perform in the field, require the high cost, or sometimes are impossible. The experimental modeling is conducted to analyze the riprap failure modes and the stability of riprap protection without filters based on the different approach velocity and riprap layer thickness conditions. Also, the stability index to evaluate the performance of riprap protection is developed using the experimental results. The cover and thickness of the riprap layer play a very important role in the stability and thicker riprap layers can prevent a total disintegration of the riprap layer effectively, especially due to winnowing failure.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.15 no.4
• /
• pp.13-21
• /
• 2011

Seismic structure pounding between adjacent superstructures may induce the destruction of pier and bridge superstructures and cause local damage that leads to the collapse of the whole bridge system. The pounding problem is related to the expansion of joints, gap distance and seismic response of the abutments. In this research, methods of the contact element approach, the linear spring model, the Kelvin-Voigt model and the Hertz model were studied to analyse the pounding characteristics. The shaking table test for a model specimen such as a bridge superstructure with elastomeric bearings was performed to evaluate the contact element approach methods. Relationships between the time history response from the numerical analysis results and the measured response from the shaking table test are compared. The experimental results were not well matched with the numerical analysis results using the existing pounding stiffness models. Therefore, in this study, coefficients are proposed to calculate the appropriate pounding stiffness ratio.

• Journal of the Korean Geosynthetics Society
• /
• v.15 no.1
• /
• pp.11-19
• /
• 2016

This paper presents the results of a scale model test to the effect of heat exchanger drainage method in retaining wall of weathered granite soil. Purpose to rise in the temperature of the heat wires inside the weathered granite soil is preventing the collapse of the retaining wall and drainage smoothly moved to the drainage layer. Especially using a spray gun to simulate the rainfall since the rainfall drainage work is important for the rainfall effect on soil, find the difference about displacement of the retaining wall, change of volume water content, drainage, earth pressure and change in the strain of the geosynthetic was effected to heat exchanger within the soil. The result from applying the heat exchanger method decreased the earth pressure and displacement of the wall and increased drainage of water.

• Korean journal of communication and information
• /
• v.84
• /
• pp.124-151
• /
• 2017

This study examines photographers who experienced steep changes from film to digital photography working and photography culture after using digital camera through a phenomenological approach. Digital technologies have brought many transition. Most of all digital camera popularize photography among people who had no knowledge and experience about camera. On the contrary digital photography made many professional photographers difficulties. After being digital photography, most film companies and film developing and printing studios have diminished. In addition many professional photographers have to cover increasing working time by decreasing photography price. For this research researcher interviewed 12 professional photographers who is working as a digital photographer. After collecting data, researcher analyse data by phenomenological approach. This study is looking for a meaning of photographers' labor after digital photography times.

• Korean Journal of Child Studies
• /
• v.23 no.1
• /
• pp.153-171
• /
• 2002

This research addressed the issue of how mothers' representations of attachment are transmitted to children, focusing on post-infancy attachment and on maternal stress as a mediator between mother's attachment style and child attachment security. Fifty-three mother-child dyads participated in a lab visit when the children were 30 months (T1) and 49 months (T2) of age. The Attachment Style Questionnaire and the Parental Stress Inventory were used to measure mothers' characteristics; the Separation-Reunion procedure and classification at T1 and the Attachment Q-set at T2 were used to measure children's attachment security. The models were analyzed by Analysis of Moment Structure Equation. Results confirmed evidence that no direct pathway exists between maternal attachment style and child attachment security : at T1 child attachment security formation was related to maternal stress, but there was no such relationship at T2.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.5
• /
• pp.1-11
• /
• 2008

Wireless Sensor Networks is applied to improvement of life convenience or service like U-City as well as environment pollution, tunnel and structural health monitoring, storm, and earthquake diagnostic system. To increase the usability of sensor data and applicability, mobile devices and their facilities allow the applications of sensor networks to give mobile users and actuators the results of event detection at anytime and anywhere. In this paper, we present MUSNEMO(Multi-sensor centric Ubiquitous Smart sensor NEtwork using Mobile devices) developed system for providing more efficient and valuable information services with a variety of mobile devices and network camera integrated to WSN. Our system is performed based on IEEE 802.15.4 protocol stack. To validate system usability, we built sensor network environments where were equipped with five application sensors such magnetic, photodiode, microphone, motion and vibration. We also built and tested proposed MUSNEMO to provide a novel model for event detection systems with mobile framework.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.453-453
• /
• 2011

21세기에 들어 홍수의 규모가 대형화 되었고, 그 발생빈도 및 강도도 증가하고 있다. 최근에는 지구온난화가 지속화되면서 전 세계적으로 높은 강도의 기상이변들이 속출하고 있고, 이러한 이상기후에 따른 태풍, 집중호우 등의 대규모 호우로 인해 댐 및 제방 등의 수공구조물 붕괴와 같은 비상상황이 초래 될 수 있다. 이와 같은 피해들을 통해 홍수 침수 범위의 예측, 분석을 통한 홍수위험 및 다양한 홍수위험지도 작성의 필요성이 대두되었고, 실제로 국가 차원의 홍수위 험지도가 제작되고 있다. 특히, 홍수 위험도 분석에 있어서 홍수에 노출된 지역의 인구수, 홍수에 노출된 지역에서의 경제적 활동의 형태, 홍수가 발생했을 때 2차적 피해를 불러올 수 있는 설비 등을 나타내는 홍수 취약도(Flood Vulnerability)에 대한 정량적 평가는 홍수위험지표 및 홍수위험강도 등에 의한 Flood Risk 개념을 기반으로 한 홍수위험지도 제작을 위해 매우 중요한 사항이라 할 수 있다. 그러나 현재까지의 홍수취약도 산정방법은 방법론적인 면에 있어 다소 단순하고, 직관에 의한 위험도의 분류가 이루어지고 있는 실정이다. 또한 취약도 지표의 산정과정이 전문가의 의견에 의존하는 경우가 많아 홍수 취약도 선정과정과 가중치 결정과정에 전문가들의 주관이 개입되는 등 홍수위험지표의 정량화에 어려움을 겪는 경우가 많다. 본 연구에서는 위와 같은 문제를 극복하기 위해 Flood Risk Mapping 기술의 적용에 있어 중요한 요소인 홍수취약도를 다기준의사결정법에 의해 산정하고, 국내 낙동강 유역에 대해 행정구역별로 세분화된 홍수위험지도 제작을 위한 취약도 지표를 산정하고자 하였다. 이를 위해 다기준의사결정법중의 하나 인 PROMEETEE와 ELECTRE를 이용하여 민감도, 노출도, 저감성 지표를 낙동강 유역에 대해 정량화하여 도시하였다. 본 연구결과를 통해 홍수위험지표 및 지수들의 결합에 대한새로운 방법론을 제시하고, 그에 따른 지도화 기법을 확립할 수 있을 것으로 기대된다.

• Polymer(Korea)
• /
• v.29 no.4
• /
• pp.369-374
• /
• 2005

In this work, the calcium alginate microcapsules containing lemon oil were prepared by emulsification-internal gelation and their potential use as aromatherapy was examined by the controlled release system. The lemon oil encapsulated in the alginate was successfully observed by Fourier transform (FT-IR) spectroscopy and differential scanning calorimeter (DSC) measurements. Analysis of the diameters and shapes of microcapsules was conducted by scanning electron microscopy (SEM). The mean diameters ranging from 4 to 7 um and encapsulation yield ranging from 50 to $85\%$ were obtained. The controlled release of the lemon oil at $37^{circ}$ was demonstrated by the infrared moisture determination (IMDB). It was found that the amount of released lemon oil decreased with increasing concentrations of alginate and $CaCl_2$ due to the higher the cross-linking density of the capsules prepared. The oil release from the capsule was measured as a function of physical force. We confirmed that the external factor could control the collapse of capsule wall and the release rate.

• Journal of Korea Water Resources Association
• /
• v.38 no.5 s.154
• /
• pp.333-343
• /
• 2005

The upwind model is well known to simulate shockwaves, but it is rarely applied to natural rivers because of problems caused by the source terms. Although several methods have been developed to deal with the source terms, none of them has been applied to natural rivers. This paper deals with application of the upwind model to the natural river. An implicit upwind model is applied to a hypothetical irregular channel and a natural river with highly irregular bed, width, and hydraulic structures. Different types of the flows including steady-state flow, flood wave, dam-break wave, and bore are simulated to test accuracy and applicability of the implicit upwind model. It is proved that the model can simulate various types of flows in natural rivers with high accuracy and robustness.

• Explosives and Blasting
• /
• v.27 no.2
• /
• pp.12-18
• /
• 2009

Recently, several cases of destruction of old cylindrical silos by explosive demolition method have been reported. This study deals with the subject concerning the pre-weakening of a cylindrical concrete silo for the application of overturning explosive demolition method. In the past, the pre-weakening operation of structure in explosive demolition has been done by use of some empirical methods. These empirical approaches, however, have possibilities of unexpected accidents. In order to provide a guideline for the pre-weakening of cylindrical silos and similar structures, this paper shows the result of a case study, in which the instability of a silo due to pre-weakening is investigated by a numerical structural analysis before actually conducting pre-weakening and demolition operations.