• 한국산업융합학회 논문집
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• 제5권1호
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• pp.53-64
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• 2002

The purpose of this study was to predict the future urban activities effectively and rationally. For the purpose, a simulation model, based on SD, was built by integrating economic activities, land use and traffic of a city and by dividing Daegu Metropolitan City into seven districts and one county. To identify the effect of the development of a new city in the Dalsung County area, the future population and traffic volume of the city were predicted, using the model. The results are summarized as follows. The future population according to the development of a new city in the Dalsung County area was predicted, and the effects before and after the development twenty years later were compared. The future population of the Dalsung County was found to have slightly increased, whereas that of the adjoining Dalsuh Metropolitan District was found to has slightly decreased. For the other districts, there were no changes of the future population. It was found, therefore, that the development of a new city would have no effect on other districts. Then, the traffic volume according to the development of a new city in the Dalsung County area was also predicted. It was found that in the initial stage the traffic volume would increase with the increase in population of Dalsung County. It was predicted that particularly,. the traffic volume for the purpose of business would greatly increase. The traffic volume of Dalsuh Metropolitan District showed a slight decrease, whereas for the other districts, there were no changes of the traffic volume.

• 한국항해항만학회지
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• 제35권4호
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• pp.343-349
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• 2011

The forecasting of container volume which is the basis of port logistics facilities expansion has a great influence on development of an port. Based on this importance, various previous studies have presented methodology on container volume forecasting. The results of many previous studies pointed out the limitations of future forecasting based on past container volume and emphasized that more various factors should be considered to compensate this. Taking notice of this point, this study forecasted future container volume by using ARIMA model, time series analysis and System Dynamics (SD) method, a dynamic analysis technique and performed the comparative review with the forecast of the Ministry of Land, Transport and Maritime affairs. Recently with rapid changes in economic and social environment, the non-linear change tendency for forecasting container traffic is presented as a new alternative to the country.

• 무역학회지
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• 제47권6호
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• pp.291-305
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• 2022

In this study, the volume of Pohang Port was predicted. All cargo of Pohang port, iron ore, steel, and bituminous coals were selected as prediction targets. SARIMA, Prophet, and Neural Prophet were used as analysis methods. The predictive power of each model was verified, and a predictive model with high performance was used to predict the volume of goods in Pohang port. As a result of the analysis, it was found that Neural Prophet showed the highest performance in all predictive power. As a result of predicting the future volume of goods until August 2027 using Neural Prophet, it was found that the volume of all items in Pohang port was decreasing. In particular, it was analyzed that the decline in steel cargo was steep. In order to increase the volume of cargo at Pohang port, it is necessary to diversify the cargo handled at Pohang port and check the policy of increasing the volume of cargo.

• 한국항만경제학회지
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• 제31권1호
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• pp.69-84
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• 2015

본고는 개입 승법계절 ARIMA모형과 인공신경망모형을 이용하여 해상운송 물동량을 추정하고 사전적 예측치를 도출하였다. 개입 ARIMA의 추정결과 오차항에서 자기상관이 존재하지 않고 정규성이 존재함으로써 오차항의 기본가정이 잘 충족되고 있음을 확인하였다. 그리고 개입 승법계절 ARIMA모형과 인공신경망모형에 대해 예측실적 오류를 ME, MAE, RMSE, MSE로 측정한 결과 ARIMA $(2,1,0)(1,0,1)_{12}$이 가장 우수한 예측모형임을 확인할 수 있었다. 2015년부터 2019년까지의 기간에 대해 개입 ARIMA모형을 이용한 해상운송 물동량의 사전적 예측치 결과 4.54%에서 4.99%의 연평균 증가율을 보였고, 인공신경망모형을 이용한 예측결과 2.00%에서 2.44%까지의 연평균 증가율을 나타냈다.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제3권1호
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• pp.57-73
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• 1999

Baroclinic hydraulic model experiments on the time-varying states of the flow pattern and water exchange in Sagami Bay were carried out based on quasi-steady state experiments on the flow pattern. For the model experiments, density changes as well as time changes in the volume transport of the upper layer were executed to investigate the flow response of the bay in the case of a sudden inflow of low density water and variable volume transport into the Sagami Bay. The results of the model experiments showed that when the volume transport was increased frontal eddies or frontal wave streamers from the Kuroshio Through Flow were transferred to the inner part of the bay along with cyclonic circulation in the bay. In addition, density boundary currents appeared and flowed along the eastern boundary of the bay. As the upper layer density decreased, frontal eddies, frontal streamers and coastal boundary density currents occurred and proceeded along the eastern boundary of the bay at a high speed.

• 한국농공학회논문집
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• 제62권1호
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• pp.61-70
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• 2020

To estimate the ventilation volume of mechanically ventilated swine farms, various regression models were applied, and errors were compared to select the regression model that can best simulate actual data. Linear regression, linear spline, polynomial regression (degrees 2 and 3), logistic curve, generalized additive model (GAM), and gompertz curve were compared. Overfitting models were excluded even when the error rate was small. The evaluation criteria were root mean square error (RMSE) and mean absolute percentage error (MAPE). The evaluation results indicated that degree 3 exhibited the lowest error rate; however, an overestimation contradiction was observed in a certain section. The logistic curve was the most stable and superior to all the models. In the estimation of ventilation volume by all of the models, the estimated ventilation volume of the logistic curve was the smallest except for the model with a large error rate and the overestimated model.

• Computers and Concrete
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• 제29권 6호
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• pp.361-374
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• 2022

On the premise of ensuring that the automatic and quantitative discharging function of concrete conveyors is met, the accuracy of the weight forecast by the mathematical model of the screw conveying volume is improved, and the error of the weight of the concrete parts and the accumulation thickness is reduced. In this paper, the discrete element method (DEM) is used to simulate the macroscopic flow of concrete. Using the concrete discrete element model, the size of the screw conveyor is set, and establish the response model between the influencing factors (process and structure) and the concrete mass flow rate according to the design points of the screw discharging experiment. The nonlinear data fitting method is used to obtain the volumetric efficiency function under the influence of process and structural factors, and the traditional screw conveying volume model is improved. The mass flow rate of concrete predicted by the improved mathematical model of screw conveying volume is consistent with the test results. The model can accurately describe the conveying process of concrete and achieve the purpose of improving the accuracy of forecasting the weight of discharged concrete.

• 무역학회지
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• 제46권6호
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• pp.211-224
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• 2021

Based on the perspective of international trade and cross-border e-commerce development, this paper explores the impact of cross-border e-commerce on international trade. This paper first describes the current situation of China's cross-border e-commerce and proposes a theoretical model of the influence of China's cross-border e-commerce on its international trade based on the research and summary of a large number of relevant documents. This paper establishes an extended gravity model based on the proposed theoretical model. Relevant data of 13 trading partner countries were used as sample data, and OLS regression analysis and heterogeneity analysis were conducted on gravity model by using Eviews 11.0. Then, in order to study the influence of each variable on import and export trade volume, import and export trade volume were respectively taken as explained variables and further studied by OLS regression analysis. To test the robustness of the model, the empirical analysis results show that cross-border e-commerce does promote the volume of China's international trade.

• 사물인터넷융복합논문지
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• 제10권1호
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• pp.39-45
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• 2024

항만 성능에 대한 정확한 평가는 컨테이너 물동량은 매우 중요한 요소이며, 효과적인 항만 개발 및 운영 전략에 대한 정확한 예측이 필수적이다. 하지만 해양 산업의 급격한 변화로 인해 컨테이너 물동량 예측의 정확성이 향상되기는 어렵다. 이를 해결하기 위해 사물인터넷(IoT)을 이용한 항만 성능에 미치는 영향을 분석하여 부산항의 경쟁력과 효율성을 향상시키기 위해 적용이 필요하다. 이에 본 연구에서는 부산항의 미래 컨테이너 물동량을 예측하기 위한 예측 모델을 개발하는 것을 목표로 이를 통해 항만 관리 기관의 개선된 의사 결정과 항만 생산성을 향상시키는 데 초점을 맞추고 있다. 항만 컨테이너 물동량을 예측하기 위해 본 연구에서는 기계 학습 모델의 Extreme Gradient Boosting (XGBoost) 기법을 도입하였다. XGBoost는 다른 알고리즘에 비해 높은 정확도, 빠른 학습 및 예측 속도,과적합을 방지하고 Feature Importance 제공하는 장점이 돋보인다. 특히 XGBoost는 회귀 예측 모델링에 직접 사용할 수 있어 기존 연구에서 제시된 물동량 예측 모델의 정확도 향상에 도움이 된다. 이를 통해 본 연구는 4.3% MAPE (Mean absolute percenture error) 값으로 제안된 방법이 컨테이너 물동량을 정확하고 신뢰성 있게 예측할 수 있다. 본 연구에서 제시한 방법론을 통해서 부산 컨테이너물동량의 정확성을 높일 수 있을 것으로 판단된다.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.106-114
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• 2003

The pressure ripple in the delivery port is caused by flow ripple, which is induced by variation of pumping chamber volume. The other reason is the reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume, when the pumping chamber is connected with the outlet volume. In this study, a mathematical model is presented for analyzing discharge pressure ripple, which includes vane detachment, cam ring movement , and fluid inertia effects in V-groove in the side plate. From the analysis and experiment, it was found that V-groove on the side plate, coefficient of spring supporting the cam ring, and average discharge pressure are the main factors of discharge pressure ripple in variable displacement vane pump. The theoretical results, provided in this study, were well agreed with experimental results. The analytical model to estimate the magnitude of pressure ripple in this study is expected to be used f3r the optimal design of the variable displacement vane pump.