• Title/Summary/Keyword: series model

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Adaptive Learning Path Recommendation based on Graph Theory and an Improved Immune Algorithm

  • BIAN, Cun-Ling;WANG, De-Liang;LIU, Shi-Yu;LU, Wei-Gang;DONG, Jun-Yu
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.5
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    • pp.2277-2298
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    • 2019
  • Adaptive learning in e-learning has garnered researchers' interest. In it, learning resources could be recommended automatically to achieve a personalized learning experience. There are various ways to realize it. One of the realistic ways is adaptive learning path recommendation, in which learning resources are provided according to learners' requirements. This paper summarizes existing works and proposes an innovative approach. Firstly, a learner-centred concept map is created using graph theory based on the features of the learners and concepts. Then, the approach generates a linear concept sequence from the concept map using the proposed traversal algorithm. Finally, Learning Objects (LOs), which are the smallest concrete units that make up a learning path, are organized based on the concept sequences. In order to realize this step, we model it as a multi-objective combinatorial optimization problem, and an improved immune algorithm (IIA) is proposed to solve it. In the experimental stage, a series of simulated experiments are conducted on nine datasets with different levels of complexity. The results show that the proposed algorithm increases the computational efficiency and effectiveness. Moreover, an empirical study is carried out to validate the proposed approach from a pedagogical view. Compared with a self-selection based approach and the other evolutionary algorithm based approaches, the proposed approach produces better outcomes in terms of learners' homework, final exam grades and satisfaction.

Gugokri-Nongdari Sedimentary Succession and Environment in the Southwestern Eumsung Basin (Cretaceous), Korea (백악기 음성분지 남서부의 구곡리-농다리 퇴적층과 퇴적환경)

  • Ryang, Woo-Hun
    • Journal of the Korean earth science society
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    • v.39 no.6
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    • pp.545-554
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    • 2018
  • The Cretaceous Eumsung (Eumseong) Basin is a pull-apart basin, formed along a series of the Gongju strike-slip faults trending NE-SW. The Nongdari-Meer forest of the Gugokri area in the southwestern part of the basin is comprised of thick purple mudstone, intercalating conglomerate, pebbly sandstone, and green mudstone beds. The succession mainly consists of seven sedimentary facies: stratified conglomerate (C2), conglomerate encased in siltstone (CE), stratified pebbly sandstone encased in siltstone (PSE2), purple sandy siltstone (Zp), green sandy siltstone (Zg), purple mudstone (Mp), and green mudstone (Mg). Sedimentary environment is mainly indicative of alluvial-plain setting in an alluvial-to-lacustrine sedimentary system, developed in the southwestern part of the basin. Geological survey was fulfilled in succession of the Gugokri sedimentary system using 1:5000 topographic map, which resulted in a geological route map. This study newly suggested that there be fluvial systems showing ENE and NNE trends in the study area, based on data of palaeocurrent direction and sedimentary characteristics in new outcrops of the forest. The study also revised the precedent sedimentation model of the Gugokri system.

Assessment of Drought Severity on Cropland in Korea Peninsula using Normalized Precipitation Evapotranspiration Index (NPEI) (정규화강수증발산지수(NPEI)를 활용한 한반도 농경지의 가뭄심도 평가)

  • Lim, Chul-Hee;Kim, Damin;Shin, Yuseung;Lee, Woo-Kyun
    • Journal of Climate Change Research
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    • v.6 no.3
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    • pp.223-231
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    • 2015
  • Although a considerable part of climate change can be explained by temperature change, hydrological change such as precipitation, evapotranspiration, and runoff impact more on society. For the ascertain a hydrological change in agriculture sector, this study estimate evapotranspiration of cropland in the Korean peninsula, and then to assess the drought severity in the past 30 years through the estimated potential evapotranspiration and observed precipitation. The potential evapotranspiration is estimated by EPIC model and Penman-Monteith method and the drought severity in cropland of the Korean peninsula is assessed using Normalized Precipitation Evapotranspiration Index (NPEI) based on the difference in precipitation and potential evapotranspiration. In North Korea, the estimated evapotranspiration tends to increase even though a significant change is not found due to the change of climate. Although a time series change in drought severity in the past 30 years is not pronounced, a deviation by year and difference between South and North Korea is certain. One reason of this is difference in precipitation and evapotranspiration change according to the latitude. The result including expansion of facilities for water management in North Korea can be used for agricultural decision making, as well as base data of climate change adaptation.

The Analysis of the Effect of Fiscal Decentralization on Economic Growth: Centering The U. S. (재정분권화가 경제성장에 미치는 영향에 관한 실증연구: 미국의 경우를 중심으로)

  • Choi, Won Ick
    • International Area Studies Review
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    • v.16 no.3
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    • pp.77-97
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    • 2012
  • Estimated coefficients has serious problems including inconsistency, biasness, etc. because many researches about the effect of fiscal decentralization on a country's economic growth use the traditional OLS method. Researches use the data intactly so that so called "spurious regression" phenomenon exists. This causes fundamental fallacy. This research tries unit root test, cointegration test, and then estimates the United States' economic time series by using VECM. The analysis of the effect of the state level-fiscal decentralization on economic growth shows two long term-equilibriums. During short term-dynamic adjustment, fiscal decentralization and economic growth move the same or different directions. In case of prediction GDP increases steeply and then from 2015 gently; and fiscal decentralization index shows a general reduction trend and then decreases slowly. At local level it shows two long term-equilibriums. During short term-dynamic adjustment, fiscal decentralization and economic growth also move the same or different directions. Impulse response analysis shows the very negative effect of fiscal decentralization on economic growth.

High-revenue Online Provisioning for Virtual Clusters in Multi-tenant Cloud Data Center Network

  • Lu, Shuaibing;Fang, Zhiyi;Wu, Jie
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.3
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    • pp.1164-1183
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    • 2019
  • The rapid development of cloud computing and high requirements of operators requires strong support from the underlying Data Center Networks. Therefore, the effectiveness of using resources in the data center networks becomes a point of concern for operators and material for research. In this paper, we discuss the online virtual-cluster provision problem for multiple tenants with an aim to decide when and where the virtual cluster should be placed in a data center network. Our objective is maximizing the total revenue for the data center networks under the constraints. In order to solve this problem, this paper divides it into two parts: online multi-tenancy scheduling and virtual cluster placement. The first part aims to determine the scheduling orders for the multiple tenants, and the second part aims to determine the locations of virtual machines. We first approach the problem by using the variational inequality model and discuss the existence of the optimal solution. After that, we prove that provisioning virtual clusters for a multi-tenant data center network that maximizes revenue is NP-hard. Due to the complexity of this problem, an efficient heuristic algorithm OMS (Online Multi-tenancy Scheduling) is proposed to solve the online multi-tenancy scheduling problem. We further explore the virtual cluster placement problem based on the OMS and propose a novel algorithm during the virtual machine placement. We evaluate our algorithms through a series of simulations, and the simulations results demonstrate that OMS can significantly increase the efficiency and total revenue for the data centers.

Seismic Fragility Evaluation of Cut-and-cover Tunnel (박스형 터널의 지진 취약도 평가)

  • Park, Duhee;Nguyen, Duy-Duan;Lee, Tae-Hyung;Nguyen, Van-Quang
    • Journal of the Korean Geotechnical Society
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    • v.34 no.11
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    • pp.71-80
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    • 2018
  • In this study, the seismic response of cut-and-cover box tunnels is evaluated from pseudo-static analyses and the fragility curves are derived. A series of site profiles were used to evaluate the effect of soil conditions. A total of 20 ground motions were used. The fragility curves were developed as functions of peak ground acceleration for three damage states, which are minor, moderate, and extensive states. The damage indices, defined as the ratio of the elastic moment to the yield moment, correlated to three damage states, were used. The curves are shown to greatly depend on the site profile. The curves are further compared to those derived in previous studies. The widely used empirically derived curves are shown not to account for the site effects, and therefore underestimate the response for soft sites.

Modeling of the effect of current density and contact time on membrane fouling reduction in EC-MBR at different MLSS concentration (EC-MBR 공정의 MLSS, 전류밀도 및 접촉시간이 막 오염 감소에 미치는 영향 모델링)

  • Kim, Wan-Kyu;Chang, In-Soung
    • Journal of Korean Society of Water and Wastewater
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    • v.33 no.2
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    • pp.111-119
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    • 2019
  • Electro-coagulation process has been gained an attention recently because it could overcome the membrane fouling problems in MBR(Membrane bio-reactor). Effect of the key operational parameters in electro-coagulation, current density(${\rho}_i$) and contact time(t) on membrane fouling reduction was investigated in this study. A kinetic model for ${\rho}_i$ and t required to reduce the membrane fouling was suggested under different MLSS(mixed liquor suspended solids) concentration. Total 48 batch type experiments of electro-coagulations under different sets of current densities(2.5, 6, 12 and $24A/m^2$), contact times(0, 2, 6 and 12 hr) and MLSS concentration(4500, 6500 and 8500mg/L) were carried out. After each electro-coagulation under different conditions, a series of membrane filtration was performed to get information on how much of membrane fouling was reduced. The membrane fouling decreased as the ${\rho}_i$ and t increased but as MLSS decreased. Total fouling resistances, Rt (=Rc+Rf) were calculated and compared to those of the controls (Ro), which were obtained from the experiments without electro-coagulation. A kinetic approach for the fouling reduction rate (Rt/Ro) was carried out and three equations under different MLSS concentration were suggested: i) ${\rho}_i^{0.39}t=3.5$ (MLSS=4500 mg/L), ii) ${\rho}_i^{0.46}t=7.0$ (MLSS=6500 mg/L), iii) ${\rho}_i^{0.74}t=10.5$ (MLSS=8500 mg/L). These equations state that the product of ${\rho}_i$ and t needed to reduce the fouling in certain amounts (in this study, 10% of fouling reduction) is always constant.

CRPN (Customer-oriented Risk Priority Number): RPN Evaluation Method Based on Customer Opinion through SNS Opinion Mining (CRPN(Customer-oriented Risk Priority Number): SNS 오피니언 마이닝을 활용한 고객 의견 기반의 RPN 평가 기법)

  • Yoo, In-Hyeok;Kang, Won-Kyung;Choi, Kyu-Nam;Park, Ji-Yun;Lee, Geon-Ju;Kang, Sung-Woo
    • Journal of Korean Society for Quality Management
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    • v.47 no.1
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    • pp.97-108
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    • 2019
  • Purpose: The purpose of this study is to propose a new Risk Priority Number(RPN) evaluation method which analyzes value of product functions by mining customer opinions in Social Network Service(SNS). Methods: A traditional RPN is measured by three evaluation standards (Severity, Occurrence, Detection) which are analyzed by manufacturing engineers and researchers. On the other hand, these standards are analyzed by customers' viewpoints through SNS opinion mining in this research. In order to extract customer feedbacks from textual data sets, the methodology in this paper implies natural language processing, hereby collecting product related data sets and analyzing the opinions automatically. An emotional polarity of an opinion indicates severity, while the number of negative opinion shows occurrence, and the entire number of customer opinion refers to detection. Results: The results of this study are as follows; As a result of the CRPN evaluation, it is confirmed that the features evaluated as risky are highly likely to be improved in the next series. Therefore, CRPN is an effective risk assessment model that reflects customer feedback. Conclusion: Reflecting customer feedback is a useful tool for risk assessment of the product as well as for developing new products and improving existing products.

Full-scale investigations into installation damage of nonwoven geotextiles

  • Sardehaei, Ehsan Amjadi;Mehrjardi, Gholamhosein Tavakoli;Dawson, Andrew
    • Geomechanics and Engineering
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    • v.17 no.1
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    • pp.81-95
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    • 2019
  • Due to the importance of soil reinforcement using geotextiles in geotechnical engineering, study and investigation into long-term performance, design life and survivability of geotextiles, especially due to installation damage are necessary and will affect their economy. During installation, spreading and compaction of backfill materials, geotextiles may encounter severe stresses which can be higher than they will experience in-service. This paper aims to investigate the installation damage of geotextiles, in order to obtain a good approach to the estimation of the material's strength reduction factor. A series of full-scale tests were conducted to simulate the installation process. The study includes four deliberately poorly-graded backfill materials, two kinds of subgrades with different CBR values, three nonwoven needle-punched geotextiles of classes 1, 2 and 3 (according to AASHTO M288-08) and two different relative densities for the backfill materials. Also, to determine how well or how poorly the geotextiles tolerated the imposed construction stresses, grab tensile tests and visual inspections were carried out on geotextile specimens (before and after installation). Visual inspections of the geotextiles revealed sedimentation of fine-grained particles in all specimens and local stretching of geotextiles by larger soil particles which exerted some damage. A regression model is proposed to reliably predict the installation damage reduction factor. The results, obtained by grab tensile tests and via the proposed models, indicated that the strength reduction factor due to installation damage was reduced as the median grain size and relative density of the backfill decreases, stress transferred to the geotextiles' level decreases and as the as-received grab tensile strength of geotextile and the subgrades' CBR value increase.

Loneliness and Game Addiction in the Early Adolescence: A Four-Year Panel Study (초기 청소년의 외로움과 게임중독의 종단적 관계: 게임이용자 패널 데이터의 자기회귀 교차지연 효과 분석)

  • Jin, Borae
    • The Journal of the Korea Contents Association
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    • v.19 no.5
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    • pp.178-186
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    • 2019
  • Previous studies have shown the significant association between loneliness and game addiction. To determine the causal relationship between them, the present study utilized a series of autoregressive cross-lagged models to early adolescent panel data (N = 346) from KOCCA's Game User Panel Research. Results indicated that loneliness and game addiction, respectively, had relatively strong and stable autoregressive effects across four time points. Also, game addiction at a prior time increased loneliness at a later time, but loneliness was not significantly related to game addiction later in time. These results suggest that game addiction may cause loneliness, not the vice versa.