• Title/Summary/Keyword: dynamic prediction method

Search Result 549, Processing Time 0.025 seconds

Characteristics of Dynamic Load Transfer for Vertically Vibrating Pile (연직진동말뚝의 동적 하중전이 특성)

  • Lee, Seung-Hyun;Kim, Eung-Seok;Yoon, Ki-Yong
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.15 no.6
    • /
    • pp.3872-3878
    • /
    • 2014
  • In this study, the dynamic load transfer function, which is necessary for analyzing a pile installed by a vibro hammer, was determined by comparing the results of the analyses and instrumented tests. The static load transfer function was modeled by the Ramberg-Osgood model through an analytical method before determining the dynamic load transfer curve. The parameters of the Ramberg-Osgood model were correlated with the N value of the standard penetration test and average values of the correlation coefficient were 0.97 for the shaft load transfer and 0.98 for the base load transfer. The dynamic load transfer function was simulated using the modified Ramberg-Osgood model. The results showed that there were little differences in the characteristics of dynamic load transfer between the results of the measurement and prediction.

Predicting Ability of Dynamic Balance in Construction Workers Based on Demographic Information and Anthropometric Dimensions

  • Abdolahi, Fateme H.;Variani, Ali S.;Varmazyar, Sakineh
    • Safety and Health at Work
    • /
    • v.12 no.4
    • /
    • pp.511-516
    • /
    • 2021
  • Background: Difficulties in walking and balance are risk factors for falling. This study aimed to predict dynamic balance based on demographic information and anthropometric dimensions in construction workers. Methods: This descriptive-analytical study was conducted on 114 construction workers in 2020. First, the construction workers were asked to complete the demographic questionnaire determined in order to be included in the study. Then anthropometric dimensions were measured. The dynamic balance of participants was also assessed using the Y Balance test kit. Dynamic balance prediction was performed based on demographic information and anthropometric dimensions using multiple linear regression with SPSS software version 25. Results: The highest average normalized reach distances of YBT were in the anterior direction and were 92.23 ± 12.43% and 92.28 ± 9.26% for right and left foot, respectively. Both maximal and average normalized composite reach in the YBT in each leg were negatively correlated with leg length and navicular drop and positively correlated with the ratio of sitting height to leg length. In addition, multiple linear regressions showed that age, navicular drop, leg length, and foot surface could predict 23% of the variance in YBT average normalized composite reach of the right leg, and age, navicular drop, and leg length could predict 21% of that in the left leg among construction workers. Conclusion: Approximately one-fifth of the variability in the normalized composite reach of dynamic balance reach among construction workers using method YBT can be predicted by variables age, navicular drop, leg length, and foot surface.

ESTIMATION OF FATIGUE LIFE BY LETHARGY COEFFICIENT USING MOLECULAR DYNAMIC SIMULATION

  • Song, J.H.;Noh, H.G.;Yu, H.S.;Kang, H.Y.;Yang, S.M.
    • International Journal of Automotive Technology
    • /
    • v.5 no.3
    • /
    • pp.215-219
    • /
    • 2004
  • A vehicle structure needs to be more precisely analyzed because of complexities and varieties. Structural fatigue which is generated by fluctuations of stresses during the service life of a mechanical system is the primary concern in the structural design for safety. A fatigue life is difficult to obtain in structural components during the service life of mechanical systems since the fluctuating stress contributes to fatigue. This study introduces new procedures to measure the lethargy coefficient and to predict the fatigue life of a mechanical structure by using molecular dynamic simulation. A lethargy coefficient is the total defect-estimating coefficient, which was obtained by using the results of a simple tensile test in this study. With this lethargy coefficient, fatigue life was estimated. The proposed method will be useful in predicting the fatigue life of a structurally-modified vehicle design. The effectiveness of the proposed method using lethargy coefficient measurement to predict the fatigue life of a structure was examined by applying this method to predict the fatigue life of SS41 steel, used extensively as material of vehicle structures. Two types of specimen such as pre-cracked plate and simple plate is discussed. equation of fatigue life using the lethargy coefficient and failure time, both obtained from a simple tensile test, will be useful in engineering. This measurement and prediction technology will be extended for use in analysis of any geometric shapes of modified automotive structures.

A study on electricity demand forecasting based on time series clustering in smart grid (스마트 그리드에서의 시계열 군집분석을 통한 전력수요 예측 연구)

  • Sohn, Hueng-Goo;Jung, Sang-Wook;Kim, Sahm
    • The Korean Journal of Applied Statistics
    • /
    • v.29 no.1
    • /
    • pp.193-203
    • /
    • 2016
  • This paper forecasts electricity demand as a critical element of a demand management system in Smart Grid environment. We present a prediction method of using a combination of predictive values by time series clustering. Periodogram-based normalized clustering, predictive analysis clustering and dynamic time warping (DTW) clustering are proposed for time series clustering methods. Double Seasonal Holt-Winters (DSHW), Trigonometric, Box-Cox transform, ARMA errors, Trend and Seasonal components (TBATS), Fractional ARIMA (FARIMA) are used for demand forecasting based on clustering. Results show that the time series clustering method provides a better performances than the method using total amount of electricity demand in terms of the Mean Absolute Percentage Error (MAPE).

Improving Collaborative Filtering with Rating Prediction Based on Taste Space (협업 필터링 추천시스템에서의 취향 공간을 이용한 평가 예측 기법)

  • Lee, Hyung-Dong;Kim, Hyoung-Joo
    • Journal of KIISE:Databases
    • /
    • v.34 no.5
    • /
    • pp.389-395
    • /
    • 2007
  • Collaborative filtering is a popular technique for information filtering to reduce information overload and widely used in application such as recommender system in the E-commerce domain. Collaborative filtering systems collect human ratings and provide Predictions based on the ratings of other people who share the same tastes. The quality of predictions depends on the number of items which are commonly rated by people. Therefore, it is difficult to apply pure collaborative filtering algorithm directly to dynamic collections where items are constantly added or removed. In this paper we suggest a method for managing dynamic collections. It creates taste space for items using a technique called Singular Vector Decomposition (SVD) and maintains clusters of core items on the space to estimate relevance of past and future items. To evaluate the proposed method, we divide database of user ratings into those of old and new items and analyze predicted ratings of the latter. And we experimentally show our method is efficiently applied to dynamic collections.

Context Prediction Using Right and Wrong Patterns to Improve Sequential Matching Performance for More Accurate Dynamic Context-Aware Recommendation (보다 정확한 동적 상황인식 추천을 위해 정확 및 오류 패턴을 활용하여 순차적 매칭 성능이 개선된 상황 예측 방법)

  • Kwon, Oh-Byung
    • Asia pacific journal of information systems
    • /
    • v.19 no.3
    • /
    • pp.51-67
    • /
    • 2009
  • Developing an agile recommender system for nomadic users has been regarded as a promising application in mobile and ubiquitous settings. To increase the quality of personalized recommendation in terms of accuracy and elapsed time, estimating future context of the user in a correct way is highly crucial. Traditionally, time series analysis and Makovian process have been adopted for such forecasting. However, these methods are not adequate in predicting context data, only because most of context data are represented as nominal scale. To resolve these limitations, the alignment-prediction algorithm has been suggested for context prediction, especially for future context from the low-level context. Recently, an ontological approach has been proposed for guided context prediction without context history. However, due to variety of context information, acquiring sufficient context prediction knowledge a priori is not easy in most of service domains. Hence, the purpose of this paper is to propose a novel context prediction methodology, which does not require a priori knowledge, and to increase accuracy and decrease elapsed time for service response. To do so, we have newly developed pattern-based context prediction approach. First of ail, a set of individual rules is derived from each context attribute using context history. Then a pattern consisted of results from reasoning individual rules, is developed for pattern learning. If at least one context property matches, say R, then regard the pattern as right. If the pattern is new, add right pattern, set the value of mismatched properties = 0, freq = 1 and w(R, 1). Otherwise, increase the frequency of the matched right pattern by 1 and then set w(R,freq). After finishing training, if the frequency is greater than a threshold value, then save the right pattern in knowledge base. On the other hand, if at least one context property matches, say W, then regard the pattern as wrong. If the pattern is new, modify the result into wrong answer, add right pattern, and set frequency to 1 and w(W, 1). Or, increase the matched wrong pattern's frequency by 1 and then set w(W, freq). After finishing training, if the frequency value is greater than a threshold level, then save the wrong pattern on the knowledge basis. Then, context prediction is performed with combinatorial rules as follows: first, identify current context. Second, find matched patterns from right patterns. If there is no pattern matched, then find a matching pattern from wrong patterns. If a matching pattern is not found, then choose one context property whose predictability is higher than that of any other properties. To show the feasibility of the methodology proposed in this paper, we collected actual context history from the travelers who had visited the largest amusement park in Korea. As a result, 400 context records were collected in 2009. Then we randomly selected 70% of the records as training data. The rest were selected as testing data. To examine the performance of the methodology, prediction accuracy and elapsed time were chosen as measures. We compared the performance with case-based reasoning and voting methods. Through a simulation test, we conclude that our methodology is clearly better than CBR and voting methods in terms of accuracy and elapsed time. This shows that the methodology is relatively valid and scalable. As a second round of the experiment, we compared a full model to a partial model. A full model indicates that right and wrong patterns are used for reasoning the future context. On the other hand, a partial model means that the reasoning is performed only with right patterns, which is generally adopted in the legacy alignment-prediction method. It turned out that a full model is better than a partial model in terms of the accuracy while partial model is better when considering elapsed time. As a last experiment, we took into our consideration potential privacy problems that might arise among the users. To mediate such concern, we excluded such context properties as date of tour and user profiles such as gender and age. The outcome shows that preserving privacy is endurable. Contributions of this paper are as follows: First, academically, we have improved sequential matching methods to predict accuracy and service time by considering individual rules of each context property and learning from wrong patterns. Second, the proposed method is found to be quite effective for privacy preserving applications, which are frequently required by B2C context-aware services; the privacy preserving system applying the proposed method successfully can also decrease elapsed time. Hence, the method is very practical in establishing privacy preserving context-aware services. Our future research issues taking into account some limitations in this paper can be summarized as follows. First, user acceptance or usability will be tested with actual users in order to prove the value of the prototype system. Second, we will apply the proposed method to more general application domains as this paper focused on tourism in amusement park.

A Semi-Implicit Integration for Rate-Dependent Plasticity with Nonlinear Kinematic Hardening (비선형 이동경화를 고려한 점소성 모델의 내연적 적분)

  • Yoon, Sam-Son;Lee, Soon-Bok
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.27 no.9
    • /
    • pp.1562-1570
    • /
    • 2003
  • The prediction of the inelastic behavior of the structure is an essential part of reliability assessment procedure, because most of the failures are induced by the inelastic deformation, such as creep and plastic deformation. During decades, there has been much progress in understanding of the inelastic behavior of the materials and a lot of inelastic constitutive equations have been developed. The complexity of these constitutive equations generally requires a stable and accurate numerical method. The radial return mapping is one of the most robust integration scheme currently used. Nonlinear kinematic hardening model of Armstrong-Fredrick type has recovery term and the direction of kinematic hardening increment is not parallel to that of plastic strain increment. In this case, The conventional radial return mapping method cannot be applied directly. In this investigation, we expanded the radial return mapping method to consider the nonlinear kinematic hardening model and implemented this integration scheme into ABAQUS by means of UMAT subroutine. The solution of the non-linear system of algebraic equations arising from time discretization with the generalized midpoint rule is determined using Newton method and bisection method. Using dynamic yield condition derived from linearization of flow rule, the integration scheme for elastoplastic and viscoplastic constitutive model was unified. Several numerical examples are considered to demonstrate the efficiency and applicability of the present method.

Finite Element Model Updating of Simple Beam Considering Boundary Conditions (경계조건을 고려한 단순보의 유한요소모델개선)

  • Kim, Se-Hoon;Park, Young-Soo;Kim, Nam-Gyu;Lee, Jong-Jae
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.22 no.2
    • /
    • pp.76-82
    • /
    • 2018
  • In this present study, in order to update the finite element model considering the boundary conditions, a method has been proposed. The conventional finite element model updating method, updates the finite element model by using the dynamic characteristics (natural frequency, mode shape) which can be estimated from the ambient vibration test. Therefore, prediction of the static response of an actual structure is difficult. Furthermore, accurate estimation of the physical properties is relatively hard. A novel method has been proposed to overcome the limitations of conventional method. Initially, the proposed method estimates the rotational spring constant of a finite element model using the deflection of structure and the rotational displacement of support measurements. The final updated finite element model is constructed by estimating the material properties of the structure using the finite element model with updated rotational spring constant and the dynamic characteristics of the structure. The proposed finite element model updating method is validated through numerical simulation and compared with the conventional finite element model updating method.

A Study on Reliability Design of Fracture Mechanics Method Using FEM (유한요소법을 이용한 파괴 역학적 방법의 신뢰성설계기술에 관한 연구)

  • Baik, Seung-Yeb;Lee, Bong-Gu
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.16 no.7
    • /
    • pp.4398-4404
    • /
    • 2015
  • Stainless steel sheets are widely used as the structural material for dynamic machine structures, These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding, For fatigue design of gas welded joints such as various type joint. It is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of gas welded joints. Thus in this paper, ${\Delta}P-N_f$ curves were obtained by fatigue tests. and, ${\Delta}P-N_f$ curves were rearranged in the ${\Delta}{\sigma}-N_f$ relation with the hot spot stresses at the gas welded joints. Using these results, the accelerated life test(ALT) is conducted. From the experiment results, an life prediction model is derived and factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of welded joints and data analysis by statistic reliability method, to save time and cost, and to develop optimum accelerated life prediction plans.

Motion Flow Analysis using Bi-directional Prediction-Independent Framework in MPEG Compressed Domain (압축 영역에서의 양방향 예측 구조를 이용한 움직임 흐름 분석)

  • 김낙우;김태용;최종수
    • Journal of the Institute of Electronics Engineers of Korea SP
    • /
    • v.41 no.5
    • /
    • pp.13-22
    • /
    • 2004
  • Because video sequence consists of dynamic objects in nature, the object motion in video is an effective feature in describing the contents of video sequence and motion feature plays an important role in video retrieval. In this paper, we propose a method that converts motion vectors (MVs) to a uniform set on MPEG coded domain, independent of the frame type and the direction of prediction, and utilizes these normalized MVs (N-MVs) as motion descriptor to understand video contents. We describe a frame-type independent representation of the various types of frames presented in an MPEG video in which all frames can be considered equivalently, without full-decoding. In the experiments, we show that the proposed method is better than the conventional one in terms of performance.