• Journal of Korean Society of Transportation
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• v.20 no.5
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• pp.67-79
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• 2002

In this paper, observed trajectories of a vehicle platoon are viewed as one realization of a finite sequence of random trajectories. In this point of view, we develop novel and mathematically rigorous concept of traffic flow variables such as local traffic density, instantaneous traffic flow, and velocity field and investigate their nature on a general probability space of a sequence of random trajectories which represent vehicle trajectories. We present a simple model of random trajectories as an illustrative example and, derive the values of traffic flow variables based on the new definitions in this model. In particular, we construct the model for the sequence of random vehicle trajectories with a system of stochastic differential equations. Each equation of the system nay represent microscopic random maneuvering behavior of each vehicle with properly designed drift coefficient functions and diffusion coefficient functions. The system of stochastic differential equations nay generate a well-defined probability space of a sequence of random vehicle trajectories. We derive the partial differential equation for the expected cumulative plot with appropriate initial conditions. By solving the equation with numerical methods, we obtain the values of expected cumulative plot, local traffic density, and instantaneous traffic flow. In addition, we derive the partial differential equation for the expected travel time to a certain location with appropriate initial and/or boundary conditions, which is solvable numerically. We apply this model to a case of single vehicle trajectory.

• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.386-395
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• 2016

In trajectory-based navigation systems, a huge amount of trajectory data is needed for efficient route explorations. However, it would be very hard to collect trajectories from all the possible start and destination combinations. To provide a practical solution to this problem, we suggest a method combining collected GPS trajectories data into additional generated trajectories with new start and destination combinations without road information. We present a trajectory combination algorithm and its implementation with Scala programming language on Spark platform for big data processing. The experimental results proved that the proposed method can effectively populate the collected trajectories into valid trajectory paths more than three hundred times.

• Korean Journal of Child Studies
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• v.36 no.3
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• pp.77-92
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• 2015

The purpose of this study was to employ the Latent Growth Curve Model to investigate the developmental trajectories of maternal depressive symptoms and to identify predictors that might have an effect on change and the level of developmental trajectories. The results of this study indicated that the maternal depressive levels of a high risk group had increased significantly over the past 5 years. The predictors for these developmental trajectories of maternal depressive symptoms were as follows; birth order, maternal prenatal depressive levels, self-esteem, marital satisfaction, parenting stress and the level of family crisis experienced by the high risk group.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10c
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• pp.83-87
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• 2006

Similarity search in moving object trajectories is an active area of research. In this paper, we introduce a new concept of measure that computes spatial distance (similarity) between two trajectories of moving objects on road networks. In addition, we propose an algorithm that generates a sequence of matching edge pairs for two trajectories that ate to be compared and computes spatial distance between them which is non Euclidian in nature. With an example, we explain how our algorithm works to show spatial similarity between trajectories of moving objects in spatial network.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.109-118
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• 2022

Workers' anomalous trajectories allow us to detect emergency situations in the workplace, such as accidents of workers, security threats, and fire. In this work, we develop a scheme to detect abnormal trajectories of workers using the edit distance on real sequence (EDR) and density method. Our anomaly detection scheme consists of two phases: offline phase and online phase. In the offline phase, we design a method to determine the algorithm parameters: distance threshold and density threshold using accumulated trajectories. In the online phase, an input trajectory is detected as normal or abnormal. To achieve this objective, neighbor density of the input trajectory is calculated using the distance threshold. Then, the input trajectory is marked as an anomaly if its density is less than the density threshold. We also evaluate performance of the proposed scheme based on the MIT Badge dataset in this work. The experimental results show that over 80 % of anomalous trajectories are detected with a precision of about 70 %, and F1-score achieves 74.68 %.

• Journal of Advanced Information Technology and Convergence
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• v.9 no.2
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• pp.65-74
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• 2019

In this paper, we describe a new swing analysis system. We design this system to provide various information about golf swings and to help to correct wrong swings. We visualize three-dimensional skeletal information obtained from Kinect through various views. Golfers can see their swing behavior through these views. This system can calculate the similarity between the two trajectories obtained from Kinect to determine the similarity of swing trajectories of different golfers. Input trajectories are resampled to have equal spacing and are performed scaling and translation for accurate trajectory comparison. We have verified the usefulness of the proposed system through various analyzes.

• Phonetics and Speech Sciences
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• v.1 no.3
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• pp.65-72
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• 2009

Formant values are the most important acoustic correlates of English vowels. Classical studies on English vowels reported the first three formant values measured at a single timepoint on a sustained vowel segment. However, many recent studies revealed that partial onset or offset segments with information of dynamic spectral changes may contribute to the exact identification of English vowels with an accuracy almost comparable to that by the whole vowel segment or word. The purpose of this study was to examine formant trajectories of nine English vowels collected by Hillenbrand et al.(1995). Acoustic analysis was systematically made by a Praat script at six equidistant timepoints over the vowel segment. Results showed that the first formant trajectories played an important role in distinguishing each vowel within the front- or back-vowel groups. The second formant trajectories of the back vowels varied more drastically than those of the front vowels. The third formant value was similar except the high vowel /i/. From the vowel space on F1 by F2 axes, the formant trajectories of each vowel clearly showed a transition toward the locus of the following consonant /d/. Other acoustic data revealed that there were some vowel inherent duration or pitch values. From this study we can conclude that the dynamic spectral changes are very important in specifying acoustic characteristics of the English vowels. Further studies on vowels and diphthongs in different contexts are desirable.

• Advances in aircraft and spacecraft science
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• v.4 no.3
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• pp.237-267
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• 2017

Automatic trajectory re-planning is an integral part of unmanned aerial vehicle mission planning. In order to be able to perform this task, it is necessary to dispose of formulas or tables to assess the flyability of various typical flight segments. Notwithstanding their importance, there exist such data only for some particularly simple segments such as rectilinear and circular sub-trajectories. This article presents an analysis of a new, very efficient, way for an airplane to fly on an inclined circular trajectory. When it flies this way, the only thrust required is that which cancels the drag. It is shown that, then, much more inclined trajectories are possible than when they fly at constant speed. The corresponding equations of motion are solved exactly for the position, the speed, the load factor, the bank angle, the lift coefficient and the thrust and power required for the motion. The results obtained apply to both types of airplanes: those with internal combustion engines and propellers, and those with jet engines. Conditions on the trajectory parameters are derived, which guarantee its flyability according to the dynamical properties of a given airplane. An analytical procedure is described that ensures that all these conditions are satisfied, and which can serve for producing tables from which the trajectory flyability can be read. Sample calculations are shown for the Cessna 182, a Silver Fox like unmanned aerial vehicle, and an F-16 jet airplane.

• Phonetics and Speech Sciences
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• v.10 no.4
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• pp.31-37
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• 2018

Pitch trajectories reflect a continuous variation of vocal fold movements over time. This study examined the pitch trajectories of English vowels produced by 139 American English speakers, statistically analyzing their trajectories using the Generalized Additive Mixed Models (GAMMs). First, Praat was used to read the sound data of Hillenbrand et al. (1995). A pitch analysis script was then prepared, and six pitch values at the corresponding time points within each vowel segment were collected and checked. The results showed that the group of men produced the lowest pitch trajectories, followed by the groups of women, boys, then girls. The density line showed a bimodal distribution. The pitch values at the six corresponding time points formed a single dip, which changed gradually across the vowel segment from 204 to 193 to 196 Hz. The normality tests performed on the pitch data rejected the null hypothesis. Nonparametric tests were therefore conducted to discover the significant differences in the values among the four groups. The GAMMs, which analyzed all the pitch data, produced significant results among the pitch values at the six corresponding time points but not between the two groups of boys and girls. The GAMMs also revealed that the two groups were significantly different only at the first and second time points. Accordingly, the methodology of this study and its findings may be applicable to future studies comparing curvilinear data sets elicited by experimental conditions.

• Human Ecology Research
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• v.58 no.3
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• pp.333-341
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• 2020

This study examined the trajectories of the marital satisfaction among middle and old aged couples for 8 years. This study focused on middle and old aged couples who were relatively uninterested in family research. Using the 1-5 Waves of Korean Longitudinal Study of Ageing (KLoSA) 2006-2014, the study included 635 middle and old aged couples whose husbands were 65-74 years old at baseline. First, a latent growth model indicated that a husband's and wife's marital satisfaction trajectories decreased over time. Second, a parallel latent growth model indicated that a husband's marital satisfaction trajectories decreased more quickly, when the initial level of their own marital satisfaction was higher (husband's actor-effect); in addition, a wife's marital satisfaction trajectories also decreased more quickly, when the initial level of their own marital satisfaction was higher (wife's actor-effect). Wife's marital satisfaction trajectories decreased more slowly, when the initial level of their husband's marital satisfaction was higher (husband's partner-effect); however, the husband's slope was not associated with the initial level of their wife's. The methodological value of this work shows the application of a parallel latent growth model that includes the actor and partner effect of APIM. The findings extend our understanding of longitudinal marital dynamics between couples and promote a study on the trajectories of marital satisfaction at stages of the family life cycle.