• Title/Summary/Keyword: Non-Parametric Research

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Differences in the Effects of a Horticultural Activity Program Depending on the Level of Resilience of College Students

  • Kim, Yong Hyun;Bae, Hwa-Ok;Huh, Moo Ryong
    • Journal of People, Plants, and Environment
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    • v.22 no.3
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    • pp.255-268
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    • 2019
  • Horticultural therapy, as a kind of complementary alternative therapies using nature as a medium, is an intervention method that can be applied to various subjects by utilizing horticultural activities that anyone can enjoy as a leisure activity. This research defined the resilience of individuals as a personal characteristic, and examined differences in the intervention effect of horticultural activities depending on the level of resilience. The results obtained in this study can be utilized in planning a horticultural activity program and setting the purpose and goals of horticultural activity programs. The subjects of this study were divided into the high resilience experimental group (Group A), the low resilience experimental Group (Group C), the high resilience control group (Group B), and the low resilience control group (Group D). The experiment was conducted in the campus of G University from September to November 2017, and the experimental group participated in the program once per week, a total of 10 sessions. The Korean version of the Connor-Davidson Resilience Scale, autonomic nervous assessment, and the interpersonal relationship change scale were carried out as pre- and post-assessment. Statistical analysis was performed using a non-parametric test. Group A showed statistically significant positive changes in relaxation of physical tension and stability. In conclusion, those with high resilience showed the higher intervention effects of horticultural activities on physical relaxation and stability than those with low resilience. However, there were some possible limitations in this study. Since the number of subjects was small and subjects were limited to college students, it is impossible to generalize the results of this study. Therefore, it is necessary to conduct follow-up studies to address and overcome these limitations.

Assessment of nonlocal nonlinear free vibration of bi-directional functionally-graded Timoshenko nanobeams

  • Elnaz Zare;Daria K. Voronkova;Omid Faraji;Hamidreza Aghajanirefah;Hamid Malek Nia;Mohammad Gholami;Mojtaba Gorji Azandariani
    • Advances in nano research
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    • v.16 no.5
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    • pp.473-487
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    • 2024
  • The current study employs the nonlocal Timoshenko beam (NTB) theory and von-Kármán's geometric nonlinearity to develop a non-classic beam model for evaluating the nonlinear free vibration of bi-directional functionally-graded (BFG) nanobeams. In order to avoid the stretching-bending coupling in the equations of motion, the problem is formulated based on the physical middle surface. The governing equations of motion and the relevant boundary conditions have been determined using Hamilton's principle, followed by discretization using the differential quadrature method (DQM). To determine the frequencies of nonlinear vibrations in the BFG nanobeams, a direct iterative algorithm is used for solving the discretized underlying equations. The model verification is conducted by making a comparison between the obtained results and benchmark results reported in prior studies. In the present work, the effects of amplitude ratio, nanobeam length, material distribution, nonlocality, and boundary conditions are examined on the nonlinear frequency of BFG nanobeams through a parametric study. As a main result, it is observed that the nonlinear vibration frequencies are greater than the linear vibration frequencies for the same amplitude of the nonlinear oscillator. The study finds that the difference between the dimensionless linear frequency and the nonlinear frequency is smaller for CC nanobeams compared to SS nanobeams, particularly within the α range of 0 to 1.5, where the impact of geometric nonlinearity on CC nanobeams can be disregarded. Furthermore, the nonlinear frequency ratio exhibits an increasing trend as the parameter µ is incremented, with a diminishing dependency on nanobeam length (L). Additionally, it is established that as the nanobeam length increases, a critical point is reached at which a sharp rise in the nonlinear frequency ratio occurs, particularly within the nanobeam length range of 10 nm to 30 nm. These findings collectively contribute to a comprehensive understanding of the nonlinear vibration behavior of BFG nanobeams in relation to various parameters.

The Prediction of DEA based Efficiency Rating for Venture Business Using Multi-class SVM (다분류 SVM을 이용한 DEA기반 벤처기업 효율성등급 예측모형)

  • Park, Ji-Young;Hong, Tae-Ho
    • Asia pacific journal of information systems
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    • v.19 no.2
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    • pp.139-155
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    • 2009
  • For the last few decades, many studies have tried to explore and unveil venture companies' success factors and unique features in order to identify the sources of such companies' competitive advantages over their rivals. Such venture companies have shown tendency to give high returns for investors generally making the best use of information technology. For this reason, many venture companies are keen on attracting avid investors' attention. Investors generally make their investment decisions by carefully examining the evaluation criteria of the alternatives. To them, credit rating information provided by international rating agencies, such as Standard and Poor's, Moody's and Fitch is crucial source as to such pivotal concerns as companies stability, growth, and risk status. But these types of information are generated only for the companies issuing corporate bonds, not venture companies. Therefore, this study proposes a method for evaluating venture businesses by presenting our recent empirical results using financial data of Korean venture companies listed on KOSDAQ in Korea exchange. In addition, this paper used multi-class SVM for the prediction of DEA-based efficiency rating for venture businesses, which was derived from our proposed method. Our approach sheds light on ways to locate efficient companies generating high level of profits. Above all, in determining effective ways to evaluate a venture firm's efficiency, it is important to understand the major contributing factors of such efficiency. Therefore, this paper is constructed on the basis of following two ideas to classify which companies are more efficient venture companies: i) making DEA based multi-class rating for sample companies and ii) developing multi-class SVM-based efficiency prediction model for classifying all companies. First, the Data Envelopment Analysis(DEA) is a non-parametric multiple input-output efficiency technique that measures the relative efficiency of decision making units(DMUs) using a linear programming based model. It is non-parametric because it requires no assumption on the shape or parameters of the underlying production function. DEA has been already widely applied for evaluating the relative efficiency of DMUs. Recently, a number of DEA based studies have evaluated the efficiency of various types of companies, such as internet companies and venture companies. It has been also applied to corporate credit ratings. In this study we utilized DEA for sorting venture companies by efficiency based ratings. The Support Vector Machine(SVM), on the other hand, is a popular technique for solving data classification problems. In this paper, we employed SVM to classify the efficiency ratings in IT venture companies according to the results of DEA. The SVM method was first developed by Vapnik (1995). As one of many machine learning techniques, SVM is based on a statistical theory. Thus far, the method has shown good performances especially in generalizing capacity in classification tasks, resulting in numerous applications in many areas of business, SVM is basically the algorithm that finds the maximum margin hyperplane, which is the maximum separation between classes. According to this method, support vectors are the closest to the maximum margin hyperplane. If it is impossible to classify, we can use the kernel function. In the case of nonlinear class boundaries, we can transform the inputs into a high-dimensional feature space, This is the original input space and is mapped into a high-dimensional dot-product space. Many studies applied SVM to the prediction of bankruptcy, the forecast a financial time series, and the problem of estimating credit rating, In this study we employed SVM for developing data mining-based efficiency prediction model. We used the Gaussian radial function as a kernel function of SVM. In multi-class SVM, we adopted one-against-one approach between binary classification method and two all-together methods, proposed by Weston and Watkins(1999) and Crammer and Singer(2000), respectively. In this research, we used corporate information of 154 companies listed on KOSDAQ market in Korea exchange. We obtained companies' financial information of 2005 from the KIS(Korea Information Service, Inc.). Using this data, we made multi-class rating with DEA efficiency and built multi-class prediction model based data mining. Among three manners of multi-classification, the hit ratio of the Weston and Watkins method is the best in the test data set. In multi classification problems as efficiency ratings of venture business, it is very useful for investors to know the class with errors, one class difference, when it is difficult to find out the accurate class in the actual market. So we presented accuracy results within 1-class errors, and the Weston and Watkins method showed 85.7% accuracy in our test samples. We conclude that the DEA based multi-class approach in venture business generates more information than the binary classification problem, notwithstanding its efficiency level. We believe this model can help investors in decision making as it provides a reliably tool to evaluate venture companies in the financial domain. For the future research, we perceive the need to enhance such areas as the variable selection process, the parameter selection of kernel function, the generalization, and the sample size of multi-class.

Management Efficiency of the Full-time and Part-time Oak Mushroom Farms using DEA models (DEA 모형을 이용한 주업과 겸업 표고재배 임가의 경영효율성 비교 분석)

  • Lee, Seong-Youn;Jeon, Jun-Heon;Won, Hyun-Kyu;Lee, Jung-Min
    • Journal of Korean Society of Forest Science
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    • v.103 no.4
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    • pp.639-645
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    • 2014
  • This study was conducted to evaluate the management efficiency of oak mushroom farms in Korea using the Data Envelopment Analysis (DEA), which is one of the non-parametric estimation methods. The data that was analyzed in this study was from the result of 2013 survey entitled "Standard Diagnostic Table for Oak Mushroom Management", which was conducted from March 2012 to October 2012. This survey was based on the inputs and outputs of 20 oak mushroom farms. Specifically, this study analyzed the technical efficiency, pure-technical efficiency and scale efficiency using CCR and BCC model of the DEA methods. Furthermore, this study compares the management efficiency between the full time oak mushroom production farms and part time oak mushroom production farms. Results showed that mean value for the technical efficiency was 0.655 which is considered as inefficient in general. For the pure-technical efficiency and scale efficiency, the mean values were 0.830 and 0.747, respectively which showed that inefficiency in the management was observed in the mushroom farms. Results also showed that there were seven farms with a total efficiency of 1, namely Decision Making Unit(DMU)2, DMU5, DMU6, DMU8, DMU10, DMU15 and DMU20. The management efficiency of DMU7 specifically the inputs for production was analyzed and compared to DMU5 and DMU6 and results showed that the DMU7 had an excessive inoculation and site development cost. Lastly, it was also observed that the full time mushroom production farms were more efficient as compared to the part time mushroom farms because of the lower scale efficiency value or smaller area for mushroom production allotted in the part time farms.

A Study on Technology Forecasting of Unmanned Aerial Vehicles (UAVs) Using TFDEA (TFDEA를 이용한 무인항공기 기술예측에 관한 연구)

  • Jung, Byungki;Kim, H.C.;Lee, Choonjoo
    • Journal of Korea Technology Innovation Society
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    • v.19 no.4
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    • pp.799-821
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    • 2016
  • Unmanned Aerial Vehicles (UAVs) are essential systems for Intelligence, Surveillance, and Reconnaissance (ISR) operations in current battlespace. And its importance will be getting extended because of complexity and uncertainty of battlespace. In this study, we forecast the advancement of 96 UAVs during the period of 32 years from 1982 to 2014 using TFDEA. TFDEA is a quantitative technology forecasting method which is characterized as non-parametric and non-statistical mathematical programming. Inman et al. (2006) showed that TFDEA is more accurate in forecasting compared with classical econometrics (e.g. regression). This study got 4.06% point of annual technological rate of change (RoC) for UAVs by applying TFDEA. And most UAVs in the period are inefficient according to the global SOA frontiers. That is because the countries which develop UAVs are in the middle class of technological level, so more than 60% of world UAVs markets are shared by North America and Europe which are advanced countries in terms of technological maturity level. This study could give some insights for UAVs development and its advancement. And also can be used for evaluating the adequacy of Required Operational Capability (ROC) of suggested future systems and managing the progress of Research and Development (R&D).

Development of Non-linear Analysis Model for Torsional Behavior of Composite Box-Girder with Corrugated Steel Webs (복부 파형강판을 갖는 복합교량의 비틀림 거동에 대한 비선형 해석 모델 개발)

  • Ko, Hee Jung;Moon, Jiho;Lee, Hak-Eun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.3A
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    • pp.153-162
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    • 2011
  • Composite box-girder with corrugated steel webs has been widely used in civil engineering practice as an alternative of conventional pre-stressed concrete box-girder because the efficiency of pre-stressing can be increased and weight reduction of superstructure can be achieved by replacing concrete webs as a corrugated steel webs. However, most of previous researches were limited in shear and flexural behavior of such girder so that the torsional behaviors of composite box-girder with corrugated steel webs are not fully understood yet and it needs to be investigated. Some of previous researchers developed the nonlinear theory for torsional analysis of composite box-girder with corrugated steel webs. However, their theories were developed by ignoring the tensile behavior of concrete. Thus, there are certain limitations in analysis of serviceability such as cracking moment and torsional stiffness of the girder. This paper presents the analytical model for torsional behavior of composite box-girder with corrugated steel webs considering tensile behavior of concrete. Based on the proposed analytical model, nonlinear torsional analysis program of composite box-girder with corrugated steel webs was developed. Then, for verification of validation of the developed model, test for the girder was conducted and the results were compared with those of analytical model. Finally, parametric study was conducted and the effects of tensile behavior of concrete on the torsional behavior of the girder were discussed.

Robust determination of control parameters in K chart with respect to data structures (데이터 구조에 강건한 K 관리도의 관리 모수 결정)

  • Park, Ingkeun;Lee, Sungim
    • Journal of the Korean Data and Information Science Society
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    • v.26 no.6
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    • pp.1353-1366
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    • 2015
  • These days Shewhart control chart for evaluating stability of the process is widely used in various field. But it must follow strict assumption of distribution. In real-life problems, this assumption is often violated when many quality characteristics follow non-normal distribution. Moreover, it is more serious in multivariate quality characteristics. To overcome this problem, many researchers have studied the non-parametric control charts. Recently, SVDD (Support Vector Data Description) control chart based on RBF (Radial Basis Function) Kernel, which is called K-chart, determines description of data region on in-control process and is used in various field. But it is important to select kernel parameter or etc. in order to apply the K-chart and they must be predetermined. For this, many researchers use grid search for optimizing parameters. But it has some problems such as selecting search range, calculating cost and time, etc. In this paper, we research the efficiency of selecting parameter regions as data structure vary via simulation study and propose a new method for determining parameters so that it can be easily used and discuss a robust choice of parameters for various data structures. In addition, we apply it on the real example and evaluate its performance.

Stochastic projection on international migration using Coherent functional data model (일관성 함수적 자료모형을 활용한 국제인구이동의 확률적 예측)

  • Kim, Soon-Young;Oh, Jinho
    • The Korean Journal of Applied Statistics
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    • v.32 no.4
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    • pp.517-541
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    • 2019
  • According to the OECD (2015) and UN (2017), Korea was classified as an immigration country. The designation as an immigration country means that net migration will remain positive and international migration is likely to affect population growth. KOSTAT (2011) used a model with more than 15 parameters to divide sexes, immigration and emigration based on the Wilson (2010) model, which takes into account population migration factors. Five years later, we assume the average of domestic net migration rate for the last five years and foreign government policy likely quota. However, both of these results were conservative estimates of international migration and provide different results than those used by the OECD and UN to classify an immigration country. In this paper, we proposed a stochastic projection on international migration using nonparametric model (FDM by Hyndman and Ullah (2007) and Coherent FDM by Hyndman et al. (2013)) that uses a functional data model for the international migration data of Korea from 2000-2017, noting the international migration such as immigration, emigration and net migration is non-linear and not linear. According to the result, immigration rate will be 1.098(male), 1.026(female) in 2018 and 1.228(male), 1.152(female) in 2025 per 1000 population, and the emigration rate will be 0.907(male), 0.879(female) in 2018 and 0.987(male), 0.959(female) in 2025 per 1000 population. Thus the net migration is expected to increase to 0.191(male), 0.148(female) in 2018 and 0.241(male), 0.192(female) in 2025 per 1000 population.

Analysis of Plastic Hinge on Pile-Bent Structure with Varying Diameters (변단면 단일 현장타설말뚝의 소성힌지 영향분석)

  • Ahn, Sangyong;Jeong, Sangseom;Kim, Jaeyoung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.3C
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    • pp.149-158
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    • 2010
  • In this study, the behavior of Pile-Bent structure with varying diameters subjected to lateral loads were evaluated by a load transfer approach. An analytical method based on the beam-column model and nonlinear load transfer curve method was proposed to consider material non-linearity (elastic, yielding) and P-${\Delta}$ effect. For an effective analysis of behavior Pile-Bent structure, the bending moment and fracture lateral load of material were evaluated. And special attention was given to lateral behavior of Pile-Bent structures depending on reinforcing effect of materials and ground conditions. Based on the parametric study, it is shown that the maximum bending moment is located within a depth (plastic hinge) approximately 1~3D (D: pile diameter) below ground surface when material non-linearity and P-${\Delta}$ effect are considered. And distribution of the lateral deflections and bending moments on a pile are highly influenced by the effect of yielding. It is also found that this method considering material yielding behavior and P-${\Delta}$ effect can be effectively used to perform the preliminary design of Pile-bent structures.

Analyzing Time in Port and Greenhouse Gas Emissions of Vessels using Duration Model (생존분석모형을 이용한 선박의 재항시간 및 온실가스 배출량 분석)

  • Shin, Kangwon;Cheong, Jang-Pyo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.4D
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    • pp.323-330
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    • 2010
  • The time in port for vessels is one of the important factors for analyzing the operation status and the capacity of ports. In addition, the time in port for vessels can be directly used for estimating the greenhouse gas emissions resulted from vessels in port. However, it is unclear which variables can affect the time in port for vessels and what the marginal effect of each variable is. With these challenges in mind, the study analyzes the time in port for vessels arriving and departing port of Busan by using a parametric survival model. The results show that the log-logistic accelerated failure time model is appropriate to explain the time in port for 19,167 vessels arriving and departing port of Busan in 2008, in which the time in port is significantly affected by gross tonnage of vessels, service capacity of terminal, and vessel type. This study also shows that the greenhouse gas emission resulted from full-container vessels, which accounted for about 61% of all vessels with loading/unloading purpose arriving and departing port of Busan in 2008, is about "17 ton/vessel" in the boundary of port of Busan. However, the hotelling greenhouse gas emissions resulted from non-container vessels (3,774 vessels; 20%) are greater than those from the full-container vessels. Hence, it is necessary to take into account more efficient port management polices and technologies to reduce the service time of non-container vessels in port of Busan.