• Journal of The Geomorphological Association of Korea
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• v.25 no.2
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• pp.15-29
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• 2018

The sediment transport process in a river reflects the process of geomorphological change in the watershed, influencesthe river bed variation and the river channel migration, and is a parametric phenomenon that exhibits a dynamic self-adjusting process. Sediment load is divided into bedload and suspended load depending on the dominant mechanism. Quantitative sediment load is important information for solving river problems. Because it is difficult and time consuming to measure bedload, compared to that ofsuspended load, data on the sediment transport load and the research required for the gravel-bed rivers are insufficient. This study is to analyze the ratio of the bedload to the total sediment load in gravel-bed rivers. The sediment load ratio in gravel-bed rivers increases with the flow rate per unit width, and the rate of the bedload varies more rapidly than the suspended load. The sediment transport efficiency coefficient has been affected by the ratio of the flow depth to the mean diameter of particles and has been dependent on the shear velocity Reynolds number. So $A^{\ast}$ and $B^{\ast}$ are introduced to compensate for the uncertainties such as bed materials, sediment transport, and flow velocity distribution, and the coefficient of bedload ratio has been presented. For the sediment load data in experimental channels and rivers, A* was 3.1. The dominant variables of $B^{\ast}$ were $u_*d_m/{\nu}$ in the gravel-bed and h/dm in the sand-bed. When $B^{\ast}$ the is the same, in the experimental channels the coefficient of bedload ratio was affected by the bed forms, but in the rivers it was of little difference between the gravel-bed and sand-bed.

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.15-24
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• 2012

Even though decision of coefficient of horizontal subgrade reaction is important in analysis for pile under lateral load, the behavior of pile under lateral loading is estimated differently due to using established suggestion. Therefore this study estimates coefficient of horizontal subgrade reaction by using Chang's method or numerical inverse analysis method with the result of lateral load test. Then this study investigates the adequacy and reliability for coefficient of horizontal subgrade reaction. The analytical results of coefficient of horizontal subgrade reaction with lateral load test showed that coefficient of horizontal subgrade reaction with Chang's method was underestimated as compared with inverse analysis. Deformation modulus of foundation by Standard Specifications for Highway Bridges and Eo${\fallingdotseq}$1,400~1,600N showed similar range like range of coefficient of horizontal subgrade reaction with lateral load test.

• Fibers and Polymers
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• v.6 no.4
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• pp.318-321
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• 2005

Demand for the fabric wipes is growing continuously. Wipes in industry are used for cleaning purpose. Cleaning involves rubbing action, so it is very important to know how much frictional force is encountered during the cleaning action. In this study the effects of normal load, sliding speed on frictional characteristics of nonwoven and woven wipes, both dry and wetted with different liquids, against glass and floor tile surfaces have been reported. With the increase in the normal load the coefficient of friction goes on decreasing for both nonwoven and woven wipes and this trend is observed in both dry and wet wipes. The coefficient of friction of both nonwoven and woven wipes against glass surface is in general higher than the floor tile surface. The wipes wetted with water shows an increase in coefficient of friction as compared to dry sample, but there is reduction in the coefficient of friction when the wipe samples are wetted with vegetable oil. In case of dry wipes, the coefficient of friction in case of nonwoven wipe is higher than the woven wipe. In case of woven wipes, the ranges of coefficient of friction either due to change in liquid type, normal load or sliding speed are in general smaller than that in case of nonwoven fabrics.

• International Journal of Control, Automation, and Systems
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• v.1 no.3
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• pp.368-375
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• 2003

Data fusion approach is investigated to avoid suction in the left ventricular assist system (LVAS) using a nonpulsatile pump. LVAS requires careful control of pump speed to support the heart while preventing suction in the left ventricle and providing proper cardiac output at adequate perfusion pressure to the body. Since the implanted sensors are usually unreliable for long-term use, a sensorless approach is adopted to detect suction. The pump model is developed to provide the load coefficient as a necessary signal to the data fusion system without the implanted sensors. The load coefficient of the pump mimics the pulsatility property of the actual pump flow and provides more comparable information than the pump flow after suction occurs. Four signals are generated from the load coefficient as inputs to the data fusion system for suction detection and a neural fuzzy method is implemented to construct the data fusion system. The data fusion approach has a good ability to classify suction status and it can also be used to design a controller for LVAS.

• Tribology and Lubricants
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• v.13 no.4
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• pp.71-78
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• 1997

Wear is affected by numerous factors-contact load, sliding velocity and distance, friction coefficient, material properties and environmental conditions. Among these wear factors, surface hardness is one of very important factors to determine wear. But surface hardness is varied by work hardening during repeated sliding contact. In this reason wear rate is increased or decreased with varying surface hardness, and transition of wear mechanism is happened. In this study, the surface hardening by accumulating residual stress was analyzed by considering the repeated sliding Hertzian contact model. The results showed that surface hardness was increased with increasing contact load, friction coefficient and contact number. And the depth of hardening layer, plastic layer and elastic layer depended upon contact load and number, but they didn't depend upon friction coefficient. The predicted surface hardness was about 1.5-1.8 times as hard as the material.

• Journal of Environmental Impact Assessment
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• v.16 no.1
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• pp.79-87
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• 2007

The performance of a stream water quality analysis model depends upon many factors attributed to the geological characteristics of a watershed as well as the distribution behaviors of pollutant itself on a surface of watershed. Because the model run has to import the pollution load from the watershed as a boundary condition along an interface between a stream water body and a watershed, it has been used to introduce a pollution delivery coefficient to behalf of the boundary condition of load importation. Although a nonlinear regression model (NRM) was developed to cope with the limitation of a conventional empirical way, this an up-to-date study has also a limitation that it can't be applied where the pollution load washed off (assumed at a source) is less than that delivered (observed) in a stream. The objective of this study is to identify what causes the limitation of NRM and to suggest how we can purify the process to evaluate a pollution delivery coefficient using many field observed cases. As a major result, it was found what causes the pollution load delivered to becomes bigger than that assumed at the source. In addition, the pollution load discharged to a stream water body from a specific watershed was calculated more accurately.

• Land and Housing Review
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• v.9 no.3
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• pp.1-8
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• 2018

In Europe and the United States, the use of limit states design has almost been established for pile foundation design. According to the global trend, the Ministry of Land, Transport and Maritime Affairs has established the basic design criteria of the bridge under the limit state design method. However, it is difficult to reflect on the design right now because of lack of research on resistance coefficient of the pile method and ground condition. In this study, to obtain the resistance coefficient of PHC bored pile which is widely used in Korea, the bearing capacity calculated by the LH design standard and the bridge design standard method, the static load test(21 times) and the dynamic load test(EOID 21 times, Restrike 21) The reliability analysis was performed on the results. The analysis of the resistance coefficient of PHC bored pile by loading test was analyzed by adding more than two times data. As a result, the resistance coefficient obtained from the static load test(ultimate bearing capacity) was 0.64 ~ 0.83 according to the design formula and the target reliability index, and the resistance coefficient obtained from the dynamic load test(ultimate bearing capacity) was 0.42~0.55. Respectively. The resistance coefficient obtained from the modified bearing capacity of dynamic load test(EOID's ultimate end bearing capacity + restrike's ultimate skin bearing capacity) was 0.55~0.71, which was reduced to about 14% when compared with the resistance coefficient obtained by the static load test(ultimate bearing capacity). As a result of the addition of the data, the resistivity coefficient was not changed significantly, even if the data were increased more than 2 times by the same value or 0.04 as the previous resistance coefficient. In conclusion, the overall resistance coefficient calculated by the static load test and dynamic load tests in this study is larger than the resistance coefficient of 0.3 suggested by the bridge design standard(2015).

• Magazine of the Korean Society of Agricultural Engineers
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• v.20 no.3
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• pp.4750-4770
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• 1978

Under the various variations of the sample thickness, the load increment ratio and the load increment duration, this consolidation test of the clay in the Asan Bay was tried for the comparison with the standard consolidation test. The results gained are as follows; 1. The void ratio variations of the leached-clay samples were increasingly high, according as the sample thickness thinned and the load increment duration and the laod increment ratio increased. 2. The coefficient of consolidation were increased with the increment of the sample thickness, of the load increment ratio and of the load increment duration. Near the pre-consolidation load, the coefficient of secondary consolidation had the maximum value and lessened with the increment of the sample thicknss, and of the load increment duration 3. The value of the pre-consolidation load increased in proportion to the increment of the sample thickness and the decrease of the load increment ratio and the load increment duration. 4. The compression indices increased as the increment of load increased and decreased as the sample thickness increased. 5. The initial compression ratio increased as the sample thickness, the load increment ratio and the load increment duration decreased. The ratio of primary compression to the secondary decreased with the increment of the sample thickness and of the load increment ratio. 6. The time at the completion of psimary consolidation increased with the increment of the sample thickness and of the consolidation load, and with the decrease of the load increment ratio. 7. The compression indicses increaed as the sample thickness lessened and decreased as the load increment ratio increased. The coefficient of consolidation increased according as the sample thickness, the load increment ratio and the load increment duration went up. The settlement at the construction site should be calculated highly in proportion as the sample thickness lessened and the load increment ratio increased. The consolidation ratio is thought to be accelerated if the sample thickness and the load increment ratio becomes higher and the load increment duration longer.

• Land and Housing Review
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• v.8 no.4
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• pp.233-247
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• 2017

In Europe and the USA, the use of limit state design method has been established, and the Korea Ministry of Land, Transport and Maritime Affairs has implemented the bridge substructure design standard based on the critical state. But Korean piling methods and ground conditions are different from Europe and USA, the limit state design method can not be used immediately. In this study, the resistance coefficient was proposed by comparing and analyzing the results of the static load test(9 times) and dynamic load tests(9 times of EOID and 9 times of Restrike) with the bearing capacity calculated by Meyerhof(LH design standard, Road bridge design standard) method and surcharge load method(using Terzaghi's bearing capacity coefficient and Hansen & Vesic's bearing capacity coefficient). The previous LHI study showed the resistance coefficient of the LH design standard was 0.36 ~ 0.44, and this research result showed the resistance coefficient was 0.39 ~ 0.48 which is about 8% higher than the previous study. In this study, we tried to obtain the resistance coefficient mainly from the static load test and the resistance coefficient was 0.57 ~ 0.69(Meyhof method : LH design standard) based on the ultimate bearing capacity and the resistance coefficient was 0.49 ~ 0.60(Meyhof method : LH design standard) based on the Davissons bearing capacity. The difference of the resistance coefficient between the static and dynamic load test was greater than that we expected, we proposed the resistance coefficient(0.52 ~ 0.62 : Meyerhof method: LH design standard) using the modified bearing capacity of the dynamic load test. Summarizing the result, the coefficient of resistance obtained from the static and dynamic load tests was 0.35 ~ 0.76, which is greater than 0.3 suggested by the Road bridge design standard, so the economical design might be possible using the coefficient of resistance proposed by this study.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.1
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• pp.18-22
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• 2009

Short-term load forecasting (STLF) is an important task in power system planning and operation. Its accuracy affects the reliability and economic operation of power systems. STLF is to be classified into load forecasting for weekdays, weekends, and holidays. Due to the limited historical data available, it is more difficult to accurately forecast load for holidays than to forecast load for weekdays and weekends. It has been recognized that the forecasting errors for holidays are large compared with those for weekdays in Korea. This paper presents a polynomial regression with data mining technique to forecast load for holidays. In statistics, a polynomial is widely used in situations where the response is curvilinear, because even complex nonlinear relationships can be adequately modeled by polynomials over a reasonably small range of the dependent variables. In the paper, the coefficient of determination is proposed as a selection criterion for screening weekday data used in holiday load forecasting. A numerical example is presented to validate the effectiveness of the proposed holiday load forecasting method.