• 한국농공학회논문집
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• 제61권6호
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• pp.1-8
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• 2019

Carbon dioxide is one of the major driving forces causing climate changes, and many countries have been trying to reduce carbon dioxide emissions from various sources. Soil stores more carbon dioxide(two to three times) amounts than atmosphere indicating that soil organic carbon emission management are a pivotal issue. In this study, we developed a Soil Organic Carbon(SOC) storage estimation model to predict SOC storage amounts in soils. Also, SOC storage values were assessed based on the carbon emission price provided from Republic Of Korea(ROK). Here, the SOC model calculated the soil hydraulic properties based on the soil physical and chemical information. Base on the calculated the soil hydraulic properties and the soil physical chemical information, SOC storage amounts were estimated. In validation, the estimated SOC storage amounts were 486,696 tons($3.526kg/m^2$) in Jindo-gun and shown similarly compared to the previous literature review. These results supported the robustness of our SOC model in estimating SOC storage amounts. The total SOC storage amount in ROK was 305 Mt, and the SOC amount at Gyeongsangbuk-do were relatively higher than other regions. But the SOC storage amount(per unit) was highest in Jeju island indicating that volcanic ashes might influence on the relatively higher SOC amount. Based on these results, the SOC storage value was shown as 8.4 trillion won in ROK. Even though our SOC model was not fully validated due to lacks of measured SOC data, our approach can be useful for policy-makers in reducing soil organic carbon emission from soils against climate changes.

• 한국습지학회지
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• 제21권1호
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• pp.1-8
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• 2019

본 연구에서는 다중최적화기법을 이용하여 2가지 수문학적 과정을 통하여 유출량을 산정하는 수문모형의 모형 최적화를 시도하였으며, 수문모형으로는 융설량과 유출량을 동시에 산정할 수 있는 분포형 수문모형인 HL-RDHM을 이용하였다. 대상유역으로는 융설량 자료를 수집할 수 있는 미국 콜로라도의 Durango River 유역을 선정하였다. 다중최적화기법으로는 MOSCEM을 활용하였으며, 융설과 관련된 매개변수 5개와 유출에 관련된 매개변수 13개를 선정하여 매개변수 보정과 수문모형 최적화를 시도하였다. 모형 최적화를 위해 2004 - 2005년의 자료가 활용되었고, 2001 - 2004년 자료를 이용하여 검증하였다. 융설량과 유출량을 동시에 최적화함으로써 RMSE 기준으로, 3개의 SNOTEL 지점에서 초기해에 의한 모의치 보다 7% - 40%까지 RMSE 오차를 줄일 수 있었고, 유출구의 USGS 관측점에서 초기해에 비해 약 40% 값이 개선됨을 확인하였다.

• Geomechanics and Engineering
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• 제17권1호
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• pp.57-67
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• 2019

Water-induced strength reduction is one of the most critical causes for rock deformation and failure. Understanding the effects of water on the strength, toughness and deformability of rocks are of a great importance in rock fracture mechanics and design of structures in rock. However, only a few studies have been conducted to understand the effects of water on fracture properties such as fracture toughness, crack propagation velocity, consumed energy, and microstructural damage. Thus, in this study, we focused on the understanding of how microscale damages induced by water saturation affect mesoscale mechanical and fracture properties compared with oven dried specimens along three notch orientations-divider, arrester, and short transverse. The mechanical properties of calcite-cemented sandstone were examined using standard uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) tests. In addition, fracture properties such as fracture toughness, consumed energy and crack propagation velocity were examined with cracked chevron notched Brazilian disk (CCNBD) tests. Digital Image Correlation (DIC), a non-contact optical measurement technique, was used for both strain and crack propagation velocity measurements along the bedding plane orientations. Finally, environmental scanning electron microscope (ESEM) was employed to investigate the microstructural damages produced in calcite-cemented sandstone specimens before and after CCNBD tests. As results, both mechanical and fracture properties reduced significantly when specimens were saturated. The effects of water on fracture properties (fracture toughness and consumed energy) were predominant in divider specimens when compared with arrester and short transverse specimens. Whereas crack propagation velocity was faster in short transverse and slower in arrester, and intermediate in divider specimens. Based on ESEM data, water in the calcite-cemented sandstone induced microstructural damages (microcracks and voids) and increased the strength disparity between cement/matrix and rock forming mineral grains, which in turn reduced the crack propagation resistance of the rock, leading to lower both consumed energy and fracture toughness ($K_{IC}$).

• Wind and Structures
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• 제6권2호
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• pp.141-150
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• 2003

This paper presents galloping analysis of multiple-degree-of-freedom (MDOF) structural roofs with multiple orientations. Instead of using drag and lift coefficients and/or their combined coefficient in traditional galloping analysis for slender structures, this study uses wind pressure coefficients for wind force representation on each and every different orientation roof, facilitating the galloping analysis of multiple-orientation roof structures. In the study, influences of nonlinear aerodynamic forces are considered. An energy-based equivalent technique, together with the modal analysis, is used to solve the nonlinear MDOF vibration equations. The critical wind speed for galloping of roof structures is derived, which is then applied to galloping analysis of roofs of a stadium and a high-rise building in China. With the aid of various experimental results obtained in pertinent research, this study also shows that consideration of nonlinear aerodynamic forces in galloping analysis generally increases the critical wind speed, thus enhancing aerodynamic stability of structures.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.488-488
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• 2015

Intermittent streamflow is common phenomenon in arid and semi-arid regions. To manage water resources of intermittent streamflows, stochactic simulation data is essential; however the seasonally stochastic modeling for intermittent streamflow is a difficult task. In this study, using the periodic Markov chain model, we simulate intermittent monthly streamflow for occurrence and the periodic gamma autoregressive and copula models for amount. The copula models were tested in a previous study for the simulation of yearly streamflow, resulting in successful replication of the key and operational statistics of historical data; however, the copula models have never been tested on a monthly time scale. The intermittent models were applied to the Colorado River system in the present study. A few drawbacks of the PGAR model were identified, such as significant underestimation of minimum values on an aggregated yearly time scale and restrictions of the parameter boundaries. Conversely, the copula models do not present such drawbacks but show feasible reproduction of key and operational statistics. We concluded that the periodic Markov chain based the copula models is a practicable method to simulate intermittent monthly streamflow time series.

• Water Engineering Research
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• 제4권2호
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• pp.87-97
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• 2003

In this study, using the numerical model, the flow motion around skewed abutment is investigated to evaluate the skewness effect on the flow distribution. The skewness angle of the abutment which make with main flow direction is changed from $30\circ$ to $150\circ$ with increments of $10\circ$ while the contraction ratios due to the abutment are kept constant. For the investigation of the combined effects on the relationship between the skewness angle and flow intensities, this process will be .repeated fer different types of abutment (single and double) with different flow intensities. The maximum velocities and the velocity distributions, which can be obtained from each angle, are examined and analyzed corresponding to different angles of inclination. Based on successive model applications, an empirical expression, given in a function of contracted ratio and skewness angle, is derived for relating velocity amplifications according to the angle variations.

• 한국가시화정보학회지
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• 제4권1호
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• pp.47-55
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• 2006

The left ventricular filling flow is now considered as an indicator which can be used for early diagnosing of cardiovascular diseases. Because the understanding of left ventricular flow physics is critical for this purpose, the downstream flow characteristics of the artificial heart valve are investigated using particle image velocimetry (PIV) method. In this study, we investigated the wake characteristics of flows passing through three different artificial valves (St.Jude medical bileaflet mechanical valve. Bjork-Shiley monostrut mechanical valve and St.Jude medical Biocor bio valve). The downstream flow field has remarkably altered according to the different valves. SJM MHV has the flow field similar to the pulsating circular jet and BS MHV has oblique pulsating jet. SJM BHV shows the similar flow field of clinical data of normal heart.

• 한국주거학회논문집
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• 제12권4호
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• pp.227-230
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• 2001

The Sri Autobindo Learning Center(SALC) is sponsoring the development of a passive solar village in Creston, Colorado, Situated near the Sangre de Cristo mountains, Savitri Village will be one of several religious communities in the area. This village will incorporate 12 permanent residences and teaching and guest facilities for fifty to one hundred people. The purpose of this study is to evaluate the passive solar elements and performance of guest house at the Sri Autobindo Learning Center(SALC). To do this evaluation, the following tasks needed to be addressed. 1. the guest house design 2. the location of weather data 3. The determination of the building heating load As part of the evaluation process, guest house design will be modified and the building load and solar saving recalculated. This process will be completed until the building performance is deemed satisfactory. The conclusion is as follows; The high solar savings fraction predicted by SUNCODE should taken as an indication that further design changes would probably not be cost effective. But adding removal overhangs or other low costs measures to increase comfort in the summer appear to be appropriate.

• 한국농공학회지
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• 제44권3호
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• pp.101-110
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• 2002

Most of the agricultural structures are in shortage of feasible facility management because these structures are small in size and spacially distributed in rural area. Inspection tools based on visual inspections are generally used for agricultural structures in most of the countries, including Korea. It is necessary to survey data of the irrigation structures to maintain records, and to develop the interface program by constructing database of inspection data. This study was conducted to develop a system for safe appraisal and repair works on agricultural irrigation structures. Repair and rehabilitation method can be chosen from an optimum viewpoint if the information between the method and life-cycle management cost of agricultural structures is constructed in the database. In this study, the system assisting onsite field investigation and determining the typical rehabilitation method of typical agricultural structural problems such as fractures and cracks of members was developed.

• Computers and Concrete
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• 제22권2호
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• pp.239-248
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• 2018

TBM penetration rate is a function of intact rock properties, rock mass conditions and TBM operational parameters. Machine rate of penetrationcan be predicted by knowledge of the ground conditions and its effects on machine performance. The variation of TBM operational parameters such as penetration rate and thrust plays an important role in its performance. This study presents the results of the analysis on the TBM penetration rates in schistose rock types present along the alignment of Golab tunnel based on the analysis of a TBM performance database established for every stroke through different schistose rock types. The results of the analysis are compared to the results of some empirical and theoretical predictive models such as NTH and QTBM. Additional analysis was performed to find the optimum thrust and revolution per minute values for different schistose rock types.