• Industrial Engineering and Management Systems
• /
• 제8권4호
• /
• pp.257-263
• /
• 2009

Focusing on the idea that the equation of exponential smoothing method (ESM) is equivalent to (1, 1) order ARMA model equation, new method of estimation of smoothing constant in exponential smoothing method is proposed before by us which satisfies minimum variance of forecasting error. Theoretical solution was derived in a simple way. Mere application of ESM does not make good forecasting accuracy for the time series which has non-linear trend and/or trend by month. A new method to cope with this issue is required. In this paper, combining the trend removal method with this method, we aim to improve forecasting accuracy. An approach to this method is executed in the following method. Trend removal by a linear function is applied to the original shipping data of consumer goods. The combination of linear and non-linear function is also introduced in trend removal. For the comparison, monthly trend is removed after that. Theoretical solution of smoothing constant of ESM is calculated for both of the monthly trend removing data and the non monthly trend removing data. Then forecasting is executed on these data. The new method shows that it is useful especially for the time series that has stable characteristics and has rather strong seasonal trend and also the case that has non-linear trend. The effectiveness of this method should be examined in various cases.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.793-798
• /
• 2004

The vibration of a curved pipe conveying fluid is studied when the pipe is clamped at both ends. To consider the geometric nonlinearity, this study adopts the Lagrange strain theory for large deformation and the extensible dynamics based on the Euler-Bernoulli beam theory for slenderness assumption. By using the extended Hamilton principle, the non-linear partial differential equations are derived for the in-plane motions of the pipe. The linear and non-linear terms in the governing equations are compared with those in the previous study, and some significant differences are discussed. To investigate the vibration characteristics of the system, the discretized equations of motion are derived from the Galerkin method. The natural frequencies varying with the flow velocity are computed from the two cases, which one is the linear problem and the other is the linearized problem in the neighborhood of the equilibrium position. From these results, we should consider the geometric nonlinearity to analyze the dynamics of a curved pipe conveying fluid more precisely.

• 드라이브 ㆍ 컨트롤
• /
• 제14권4호
• /
• pp.9-16
• /
• 2017

In this study, the force tracking performance of the single-rod and double-rod type EHAs (Electro-Hydrostatic Actuators) was compared by computer simulation and experiments. The force-controlled EHAs exhibit non-linear behavior that are significantly dependent on operation conditions. The investigation focused on localizing the parameters that provide significant rise to the non-linearity. For this, the single-rod and double-rod type EHAs were mathematically expressed to derive their linear models. In parallel, they were modeled by a commercial simulation program including non-linear properties based on experimental results. It was shown that the dependency of the bulk modulus of oil with entrapped air on working pressure dominated the non-linearity in force control performance in case of the double-rod type EHA. The force control of the single-rod type EHA was influenced by much more elements. Besides the asymmetrical piston geometry and the non-linear bulk modulus of oil, its pilot-operated check valves made it dependent not only on the magnitude of reference input but also on its direction.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
• /
• pp.43-48
• /
• 2006

This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system. Under the combination operation of single & three phase load, voltage unbalance will be generated and current unbalance will be more severe by the dropped voltage quality. All power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. Moors may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration.

• 대한음성학회:학술대회논문집
• /
• 대한음성학회 2000년도 7월 학술대회지
• /
• pp.312-320
• /
• 2000

This presentation aims to explore some possibility of non-segmental phonetics usually ignored in phonetics education. In pedagogical phonetics, especially ESL/EFL oriented phonetics speech sounds tend to be classified in two criteria 1) 'pronunciation' which deals with segments and 2) 'prosody' or 'suprasegmentals', a criterion that deals with non-segmental elements such as stress and intonation. However, speech involves more dynamic processing. It is non-linear and multi-dimensional in spite of the linear sequence of symbols in phonetic/phonological transcriptions. No word is without pitch or voice quality apart from segmental characteristics whether it is spoken in isolation or cut out from continuous speech. This simply tells the dichotomy of pronunciation and prosody is merely a useful convention. There exists some room to consider dynamic non-segmental phonetics. Examples of non-segmental phonetic investigation, some of the analyses conducted within the frame of Firthian Prosodic Analysis, especially of the relation between vowel variants and foot types, are examined and we see what kind of auditory phonetic training is required to understand impressionistic transcriptions which lie behind the non-segmental phonetics.

• 한국실내디자인학회논문집
• /
• 제14권3호
• /
• pp.181-190
• /
• 2005

In accordance with the rapid growth of digital media in 1990s, the state of indetermination that is found in digital process has been emphasized in the field of natural science and philosophy. Digitalized space design has been dramatically developed and it raised heated debate and comment on 'folded space' The purpose of this thesis is to explore how the cognitive-ecological factors constitute fold structures in space design of the late 20th century. Syntax of space structure and geometric composition were analyzed to define what types of cognitive-ecological factors are contrived in the process of visual information. In particular, I put higher theoretical emphasis on what characteristics are ensued in the process of structuring spaces than any other subjects. Through theses analyses and discussions, I raised questions on what principles are operating to create new space design that counts on non-linear structure and its formational process. And I also observed what influences these structural principles of design could fundamentally bring to human beings. First, I proposed that we could overcome reductionist space design through cognitive-ecological approach. Some key concepts such as affordance, parallel processing, and redundancy were adopted as defining elements of non-linear structures. As a result of analyses, I found that the cognitive-ecological approach could substitute the reductionist space design of the past. What is also found is that the three variables are the ultimate ecological elements. In addition, as a methodological concept of fold structures, the form of 'topology' was highlighted because it could be a supporting idea to the cognitive-ecological factors. Second, I claimed that non-linear design is more experiential than rational linear design, and it is more efficiently correspondent to human being than any other forms. What is intended and implied in non-linear structure is also indicated.

• Structural Engineering and Mechanics
• /
• 제22권2호
• /
• pp.197-222
• /
• 2006

In this paper, the non-linear time-dependent closed-form, discrete and combined solutions for the post-elastic response of a geometrically and physically non-linear suspended cable to a uniformly distributed load considering the creep effects, are presented. The time-dependent closed-form method for the particularly straightforward determination of a vertical uniformly distributed load applied over the entire span of a cable and the accompanying deflection at time t corresponding to the elastic limit and/or to the elastic region, post-elastic and failure range of a suspended cable is described. The actual stress-strain properties of steel cables as well as creep of cables and their rheological characteristics are considered. In this solution, applying the Irvine's theory, the direct use of experimental data, such as the actual stress-strain and strain-time properties of high-strength steel cables, is implemented. The results obtained by the closed-form solution, i.e., a load corresponding to the elastic limit, post-elastic and failure range at time t, enable the direct use in the discrete non-linear time-dependent post-elastic analysis of a suspended cable. This initial value of load is necessary for the non-linear time-dependent elastic and post-elastic discrete analysis, concerning incremental and iterative solution strategies with tangent modulus concept. At each time step, the suspended cable is analyzed under the applied load and imposed deformations originated due to creep. This combined time-dependent approach, based on the closed-form solution and on the FEM, allows a prediction of the required load that occurs in the post-elastic region. The application of the described methods and derived equations is illustrated by numerical examples.

• 한국컴퓨터정보학회논문지
• /
• 제23권12호
• /
• pp.21-26
• /
• 2018

As the large amount of data can be efficiently stored, the methods extracting meaningful features from big data has become important. Especially, the techniques of converting high- to low-dimensional data are crucial for the 'Data visualization'. In this study, principal component analysis (PCA; linear dimensionality reduction technique) and Isomap (non-linear dimensionality reduction technique) are introduced and applied to neural big data obtained by the functional magnetic resonance imaging (fMRI). First, we investigate how much the physical properties of stimuli are maintained after the dimensionality reduction processes. We moreover compared the amount of residual variance to quantitatively compare the amount of information that was not explained. As result, the dimensionality reduction using Isomap contains more information than the principal component analysis. Our results demonstrate that it is necessary to consider not only linear but also nonlinear characteristics in the big data analysis.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2002년도 총회 및 춘계학술발표회
• /
• pp.122-126
• /
• 2002

Contaminant transport in porous media is characterized by solving an advection-dispersion equation(ADE). The ADE can cover equilibrium phenomena of interest, which include sorption, decay, and chemical reactions. Among these phenomena, sorption mechanism is described by several types of sorption isotherm. If we assume the sorption isotherm as linear, the solution of ADE can be easily procured. However, if we consider the sorption isotherm as non-linear isotherm like a Dual Reactive Domain Model (DRDM), the resulting differential equation becomes non-linear. In this case, the solution of ADE cannot be easily acquired by an analytic method. In this paper, we present the numerical analysis of ADE using a DRDM. The results reveal that even if sorption data may be fitted well using linear or non-linear isotherm, the characteristics of contaminant transport of the two cases are different from each other. To be concrete, the retardation of linear isotherm has stronger effect than that of the DRDM. As the non-linearity of sorption isotherm increases, the difference of retardation effects of the two cases becomes larger. For a pulse source, the maximum concentration of the linear model is higher than that of the DRDM, but the plume of the DRDM moves faster than that of the linear model. Behaviors of contaminant transport using the DRDM are consistent with common features of a linear model. For instance, biodegradation effect becomes larger as time goes by The faster the seepage velocity is, the faster the plume of contaminant moves. The plume of the contaminant is distributed evenly over overall domain in the event of high dispersion coefficient.

• 한국지반공학회지:지반
• /
• 제13권5호
• /
• pp.125-132
• /
• 1997

토석류는 다양한 크기의 흙 입자와 물이 고루 섞여 점성을 가진 유체처럼 하방향으로 이동한다는 사실이 관찰되었다. 이 관찰로부터 토석류를 비선행적인 점도를 가진 비뉴톤 유체처럼 거동하는 것으로 간주할 수 있다. 이 논문에서는 토석류의 레올로지적 특성을 규명하기 위해 산사태 현장에서 채취한 시료를 가지고 점도계를 사용하여 일련의 점도시험을 수행하였다. 그 결과, 토석류는 비뉴톤 유체 중 빙함 소성 모델로 거동한다는 사실이 밝혀졌다. 이 모델을 이용하면 토 석류의 이동을 예측할 수 있다.