• Journal of Positioning, Navigation, and Timing
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• v.2 no.2
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• pp.115-121
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• 2013

For the auto-landing operation of an air vehicle, the possibility of auto-landing operation should be first evaluated by testing the navigation performance through a flight test. In general, navigation performance is tested by analyzing north/east/down (NED) errors relative to reference equipment whose precision is about 8~10 times higher than that of a navigation system. However, to evaluate the auto-landing operation of an air vehicle, whether the air vehicle approaches a glide path aligned with the runway, within a specific error, needs to be examined rather than examining the north/east errors of the navigation system. Therefore, the longitudinal/lateral errors of air vehicle heading need to be analyzed. In this study, a method for analyzing the longitudinal/lateral errors of a navigation system was proposed as the navigation performance test method for evaluating the safety during the auto-landing of an air vehicle. Also, flight tests were performed six times, and the safety of auto-landing was examined by analyzing the performance using the proposed method.

• Asia pacific journal of information systems
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• v.25 no.4
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• pp.746-762
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• 2015

This study developed a conceptual model that integrated psychological and physical reactions resulting from online tourism reviews through a longitudinal trust-satisfaction model (LSTM) developed based on the extended valence framework and expectation-confirmation theory. Online reviews are essential factor of consumer's purchase decision. This phenomenon is well applied in a tourism context. However, investigations on online reviews in a longitudinal approach in a tourism context are quite limited. Therefore, this study suggests a conceptual model based on LTSM and several propositions about how online tourism reviews, which are divided into factual and experiential reviews, influence the future travelers' perceptions and attitudes, such as expectation, confirmation, and destination loyalty, in a longitudinal format by examining previous related studies. Finally, expected results were discussed and several implications were described theoretically and practically.

• Asia pacific journal of information systems
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• v.15 no.2
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• pp.121-148
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• 2005

This study focuses on MRO e-Marketplace and attempts to research how companies select the structure of e-Marketplace governance and how it influences purchasing performance. Furthermore, a longitudinal study is conducted to analyze the dynamic relationship between variables in our research model. The research gives the following results. First, as the utilization level of e-Marketplace increases, the level of relational exchange between purchasing company and e-Marketplace increases. The increased utilization level enhances purchasing efficiency rather than reducing purchasing price. Secondly, as the level of relational exchange between purchasing companies and e-Marketplace increases, system integration increases, whereas supply externality decreases. Accordingly, system integration improves purchasing efficiency, whereas the low supply externality does not help lower purchasing price. Third, compared to the initial growth stage, the stable stage of e-Marketplace has the significantly increased level of relational exchange and purchasing efficiency through system integration, rather than the reduction of purchasing price by supply externality.

• Transactions of Materials Processing
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• v.23 no.6
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• pp.369-375
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• 2014

Flexible roll forming allows profiles to have variable cross-sections. However, the profile may have some shape errors, such as, warping which is a major defect. The shape error is induced by geometrical deviations in both the concave zone and the convex zone. In the current study, flexible roll forming was modeled with FE simulations to analyze the shape error and the longitudinal strain distribution along the flange section over the profile. A distribution of analytically calculated longitudinal strains was used to develop relationships between the shape error and the longitudinal strain distribution as a function of the defined shape parameters for the profile. The FE simulations showed that the shape error is primarily affected by the deviations between the distribution of analytically calculated longitudinal strain and the longitudinal strain distribution of the profile. The results show that the shape error can be controlled by designing the shape parameters to control the geometrical deviations at the flange section in the transition zones.

• Korean Journal of Culture and Social Issue
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• v.28 no.3
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• pp.331-352
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• 2022

This study used a latent growth curve models(LGCM) to examine longitudinal changes in youth's game usage, self-control and the longitudinal mediation effect of adaptive game use in the relationship between game usage and self-control. A four-year longitudinal data of 863 adolescents from the Game User Panel Survey, provided through participation in the 2019 Game User Panel Research Conference hosted by the Korea Creative Contents Agency, was used to verify the longitudinal mediation effect of adaptive game use. SPSS 21 was used to verify the normality of variables from each wave, and to conduct correlation analysis. Mplus 6.12 was used to verify the longitudinal mediation effect. The results are as follows. First, game usage, self-control and adaptive game yielded linear temporal growth. Second, latent growth curve models showed that the direct effect of game usage on self-control was insignificant, but game usage had a significant indirect effect on self-control through adaptive game use. Continuous adaptive gaming increased self-control. Third, sobel test results showed that both the initial value and change rate of adaptive game use had a full-mediation effect, confirming the longitudinal mediation effect. This study verified the longitudinal change of self-control affected by change in game usage and adaptive game use.

• Korean Journal of Hydrosciences
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• v.8
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• pp.19-30
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• 1997

The hydraulics of flow within the covered reach of urban streams is very complicated due to the accumulation and interference effect of eddies around the multipli piers supporting the covering slab. An extensive experimental study is done to quantitatively estimate the backwater rise effect caused by various arrays of multiple piers. The factors governing the backwater rise are found out to be the contraction ratio due to the piers. Foude number of the flow, longitudinal pier spacing, and the length of the covered reach. For a single section of lateral pier arralyzed and a multiple regression equation derived. The effect of multiple piers, arrayed in both lateral and longitudinal directions. on the backwater rise is analyzed in terms of the contraction ratio. Froude number, longitudinal pier spacing and the total length of the covered reach. A multiple regression equation for the backwater rise estimation is proposed based on the experimental data collected in this study.

• Electrical & Electronic Materials
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• v.8 no.5
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• pp.572-579
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• 1995

Most of conventional ultrasonic transducers are constructed to generate either longitudinal or shear waves, but not both of them. We investigate the mechanism of dual mode transducers that generate both of the longitudinal and shear waves simultaneously with single PZT element. The study is aimed to find the optimally desired cut by examining the anisotropic piezoelectric properties. Theory predicts that a mixed P/S mode transducer can be constructed using a rotated Z-cut of PZT piezoelectric ceramics. We study the performance of a PZT element as a function of its rotation angle so that its efficiency is optimized to excite the two waves as much as equally strong. The results are verified by the waveform in pulse-echo computer simulation and experiments. When the transducer is subjected to impedance analysis, it shows two thickness mode resonances, each of which being a mixed P/S thickness mode. By examining wave speeds on E transmitter delay line receiver setup, it is confirmed that the transducer can transmit and detect both longitudinal and shear wave simultaneously.

• Journal of the Korean Wood Science and Technology
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• v.44 no.5
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• pp.677-684
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• 2016

This study was carried out to confirm the effects of the knife-incising and longitudinal kerfing treatment on high-temperature drying characteristics of red pine square timber with dimensions of thickness 15 cm. The range of final moisture content was investigated 5.6% to 7.5% after drying. The differences did not exist in the moisture content and distribution according to the pretreatment condition. In the case of longitudinal kerfing treatment, the surface check occurrence was reduced than the control. In addition, the twist had a tendency to decrease due to the longitudinal kerfing treatment. The knife-incising and longitudinal kerfing treatment were investigated to be ineffective on internal checks and drying shrinkage.

• Communications for Statistical Applications and Methods
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• v.24 no.3
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• pp.255-269
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• 2017

This article explores the analysis of longitudinal surveys in which same units are investigated on several occasions. Multivariate exponential ratio type estimator has been proposed for the estimation of the finite population median at the current occasion in two occasion longitudinal surveys. Information on several additional auxiliary variables, which are stable over time and readily available on both the occasions, has been utilized. Properties of the proposed multivariate estimator, including the optimum replacement strategy, are presented. The proposed multivariate estimator is compared with the sample median estimator when there is no matching from a previous occasion and with the exponential ratio type estimator in successive sampling when information is available on only one additional auxiliary variable. The merits of the proposed estimator are justified by empirical interpretations and validated by a simulation study with the help of some natural populations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3369-3376
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• 1994

A finite element program for elastic stress wave propagation is developed in order to investigate the shape of stress field and analysis the magnitude of stress wave intensity at time increment. Accuracy and reliance of the finite element analysis are acquired when the element size is smaller than the product of the stress wave speed and the critical value of increasing time step. In the finite element analysis and theoretical solution, the longitudinal stress wave is propagated to the similar direction of impact load, and the stress wave intensity is expressed in terms of the ratio of propagated area. The direction of shear wave is declined at an angle of 45 degrees compared with longitudinal stress wave and the speed of shear wave is half of the longitudinal stress wave.