• Journal of Internet Computing and Services
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• v.24 no.5
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• pp.107-120
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• 2023

The public bicycle of Seoul, Ttareungyi, was launched at October 2015 to reduce traffic and carbon emissions in downtown Seoul and now, 2023 Oct, the cumulative number of user is upto 4 million and the number of bike is about 43,000 with about 2700 stations. However, super growth of Ttareungyi has caused the several problems, especially demand/supply mismatch, and thus the Seoul citizen has been complained about out of stock. In this point, this study conducted a real time demand forecasting model to prevent stock out bike at stations. To develop the model, the research team gathered the rental·return transaction data of 20,000 bikes in whole 1600 stations for 2019 year and then analyzed bike usage, user behavior, bike stations, and so on. The forecasting model using machine learning is developed to predict the amount of rental/return on each bike station every hour through daily learning with the recent 90 days data with the weather information. The model is validated with MAE and RMSE of bike stations, and tested as a prototype service on the Seoul Bike Management System(Mobile App) for the relocation team of Seoul City.

• Information Systems Review
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• v.25 no.3
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• pp.121-138
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• 2023

The advancement in mobile technology brought disruptive innovation in media industry. The introduction of mobile devices broke spatial and temporal restrictions in media consumption. This study investigates the impact of mobile channel adoption on video viewing behavior, using real-world dataset obtained from a particular on-demand service provider in South Korea. We find that the adoption of a mobile channel significantly increases the total viewing time of video-on-demand via TV and the number of contents viewed. Our results suggest that the mobile channels act as a complement channel to conventional TV channels. We provide theoretical and practical insights on consumer usage in the emerging over-the-top market.

• Journal of Internet of Things and Convergence
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• v.10 no.2
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• pp.25-41
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• 2024

For the scenario of open pit mining, at present, manual periodic verification is mainly carried out in China with the help of video surveillance, which requires continuous investment in labor cost and has poor timeliness. In order to solve this difficult problem of early warning and monitoring, this paper researches a spatialized algorithmic model and designs an early warning system for open-pit mine transboundary mining, which is realized by calculating the coordinate information of the mining and extracting equipments and comparing it with the layer coordinates of the approval range of the mines in real time, so as to realize the determination of the transboundary mining behavior of the mines. By taking the Pingxiang area of Jiangxi Province as the research object, after the field experiment, it shows that the system runs stably and reliably, and verifies that the target tracking accuracy of the system is high, which can effectively improve the early warning capability of the open-pit mines' overstepping the boundary, improve the timeliness and accuracy of mine supervision, and reduce the supervision cost.

• Asia pacific journal of information systems
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• v.24 no.4
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• pp.611-635
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• 2014

Information systems (IS) have become ubiquitous and changed every aspect of how people live their lives. While some IS have been successfully adopted and widely used, others have failed to be adopted and crowded out in spite of remarkable progress in technologies. Both the technology acceptance model (TAM) and the IS Success Model (ISSM), among many others, have contributed to explain the reasons of success as well as failure in IS adoption and usage. While the TAM suggests that intention to use and perceived usefulness lead to actual IS usage, the ISSM indicates that information quality, system quality, and service quality affect IS usage and user satisfaction. Upon literature review, however, we found a significant void in theoretical development and its applications that employ either of the two models, and we raise research questions. First of all, in spite of the causal relationship between intention to use and actual usage, in most previous studies, only intention to use was employed as a dependent variable without overt explaining its relationship with actual usage. Moreover, even in a few studies that employed actual IS usage as a dependent variable, the degree of actual usage was measured based on users' perceptual responses to survey questionnaires. However, the measurement of actual usage based on survey responses might not be 'actual' usage in a strict sense that responders' perception may be distorted due to their selective perceptions or stereotypes. By the same token, the degree of system quality that IS users perceive might not be 'real' quality as well. This study seeks to fill this void by measuring the variables of actual usage and system quality using 'fact' data such as system logs and specifications of users' information and communications technology (ICT) devices. More specifically, we propose an integrated research model that bring together the TAM and the ISSM. The integrated model is composed of both the variables that are to be measured using fact as well as survey data. By employing the integrated model, we expect to reveal the difference between real and perceived degree of system quality, and to investigate the relationship between the perception-based measure of intention to use and the fact-based measure of actual usage. Furthermore, we also aim to add empirical findings on the general research question: what factors influence actual IS usage and how? In order to address the research question and to examine the research model, we selected a mobile campus application (MCA). We collected both fact data and survey data. For fact data, we retrieved them from the system logs such information as menu usage counts, user's device performance, display size, and operating system revision version number. At the same time, we conducted a survey among university students who use an MCA, and collected 180 valid responses. A partial least square (PLS) method was employed to validate our research model. Among nine hypotheses developed, we found five were supported while four were not. In detail, the relationships between (1) perceived system quality and perceived usefulness, (2) perceived system quality and perceived intention to use, (3) perceived usefulness and perceived intention to use, (4) quality of device platform and actual IS usage, and (5) perceived intention to use and actual IS usage were found to be significant. In comparison, the relationships between (1) quality of device platform and perceived system quality, (2) quality of device platform and perceived usefulness, (3) quality of device platform and perceived intention to use, and (4) perceived system quality and actual IS usage were not significant. The results of the study reveal notable differences from those of previous studies. First, although perceived intention to use shows a positive effect on actual IS usage, its explanatory power is very weak ($R^2$=0.064). Second, fact-based system quality (quality of user's device platform) shows a direct impact on actual IS usage without the mediating role of intention to use. Lastly, the relationships between perceived system quality (perception-based system quality) and other constructs show completely different results from those between quality of device platform (fact-based system quality) and other constructs. In the post-hoc analysis, IS users' past behavior was additionally included in the research model to further investigate the cause of such a low explanatory power of actual IS usage. The results show that past IS usage has a strong positive effect on current IS usage while intention to use does not have, implying that IS usage has already become a habitual behavior. This study provides the following several implications. First, we verify that fact-based data (i.e., system logs of real usage records) are more likely to reflect IS users' actual usage than perception-based data. In addition, by identifying the direct impact of quality of device platform on actual IS usage (without any mediating roles of attitude or intention), this study triggers further research on other potential factors that may directly influence actual IS usage. Furthermore, the results of the study provide practical strategic implications that organizations equipped with high-quality systems may directly expect high level of system usage.

• Journal of the Society of Disaster Information
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• v.15 no.4
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• pp.548-559
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• 2019

Purpose: Analysis method of V2I data driven motorway service area usage behavior to cope with manpower survey. Method: Segmentation of traveling state group and boundary using the distribution characteristics of traveling speed data of individual vehicles. Result: As a result of the verification, the use rate of resting places in lunchtime surged, and the boundary between the distribution status of the traffic speed data was clearly or unclear. Conclusion: The effect of the cost reduction is big because it can cope with the use of rest area survey by manpower and there is no limit in the time and space range of investigation. The dynamic utilization rate of each time sequence, such as a service area/drowsiness shelter/simple service area, with a V2I system, can be calculated. Identify illegal parking on highway section. Identify the unexpected situation in the road section. Identify the real-time service area utilization rate and congestion information.

• Management & Information Systems Review
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• v.34 no.3
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• pp.125-140
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• 2015

KOSDAQ market reorganized their division system from two types to four types of division departments such as blue chip, venture, medium, and technology development departments in 2011. However, under the current new division system, financially unhealthy firms attempting to take advantage of the classifying opportunity of blue chip department are likely to engage in pernicious earnings management. The objective of this study is to investigate the earnings management behavior surrounding the time of KOSDAQ firms entering the blue chip department via new division system. More specifically, we test whether the firms classified blue chip department tend to engage in upward earnings management using accruals and real activities before and after they achieve blue chip status. In this study, we analyzed 111 firms classified blue chip department in 2011 according to new division system in KOSDAQ market. Major test results indicate that firms entering the blue chip department according to current KOSDAQ division system in general, tend to inflate reported earnings by means both of accruals and real activities right before the entering year. This result suggests that the firms classified blue chip department engage in opportunistic earnings management with a view to uplifting their market values. Our study is expected to provide clues useful for searching policy directions which intend to ameliorate adverse side effects of the current KOSDAQ division system. In sum, the regulatory authorities and enforcement bodies need to exercise caution in deliberating more stringent review procedures so that financially healthy and promising candidates are properly segregated from their poor and risky counterparts, thus enhancing the beneficial effects, while mitigating adverse side effects of the system.

• Journal of the Korea Computer Graphics Society
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• v.26 no.3
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• pp.9-19
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• 2020

With the recent development of various kinds of virtual reality devices, there has been an active research effort to increase the sense of reality by recognizing the physical behavior of users rather than by classical user input methods. Among such devices, the Leap Motion controller recognizes the user's hand gestures and can realistically trace the user's hand in a virtual reality environment. However, manipulating an object in virtual reality using a recognized user's hand often causes the hand to pass through the object, which should not occur in the real world. This study presents a way to build a visual feedback system for enhancing the user's sense of interaction between hands and objects in virtual reality. In virtual reality, the user's hands are examined precisely by using a ray tracing method to see if the virtual object collides with the user's hand, and when any collision occurs, visual feedback is given through the process of reconstructing the user's hand by moving the position of the end of the user's fingers that enter the object through sign distance field and reverse mechanics. This enables realistic interaction in virtual reality in real time.

• Wind and Structures
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• v.38 no.1
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• pp.15-42
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• 2024

A flexible-base coupled-two-beam (CTB) discrete model with equivalent tuned mass dampers is used to assess the effect of soil-structure interaction (SSI) and different types of lateral resisting systems on the design of passive dynamic absorbers (PDAs) under the action of along-wind and across-wind loads due to vortex shedding. A total of five different PDAs are considered in this study: (1) tuned mass damper (TMD), (2) circular tuned sloshing damper (C-TSD), (3) rectangular tuned sloshing damper (R-TSD), (4) two-way liquid damper (TWLD) and (5) pendulum tuned mass damper (PTMD). By modifying the non-dimensional lateral stiffness ratio, the CTB model can consider lateral deformations varying from those of a flexural cantilever beam to those of a shear cantilever beam. The Monte Carlo simulation method was used to generate along-wind and across-wind loads correlated along the height of a real shear wall-frame building, which has similar fundamental periods of vibration and different modes of lateral deformation in the xz and yz planes, respectively. Ambient vibration tests were conducted on the building to identify its real lateral behavior and thus choose the most suitable parameters for the CTB model. Both alongwind and across-wind responses of the 144-meter-tall building were computed considering four soil types (hard rock, dense soil, stiff soil and soft soil) and a single PDA on its top, that is, 96 time-history analyses were carried out to assess the effect of SSI and lateral resisting system on the PDAs design. Based on the parametric analyses, the response significantly increases as the soil flexibility increases for both type of lateral wind loads, particularly for flexural-type deformations. The results show a great effectiveness of PDAs in controlling across-wind peak displacements and both along-wind and across-wind RMS accelerations, on the contrary, PDAs were ineffective in controlling along-wind peak displacements on all soil types and different kind of lateral deformation. Generally speaking, the maximum possible value of the PDA mass efficiency index increases as the soil flexibility increases, on the contrary, it decreases as the non-dimensional lateral stiffness ratio of the building increases; therefore, there is a significant increase of the vibration control effectiveness of PDAs for lateral flexural-type deformations on soft soils.

• Reproductive and Developmental Biology
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• v.32 no.2
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• pp.117-121
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• 2008

Our previous study showed that transgenic (TG) pigs harboring human EPO (hEPO) gene have been shown to have reproductive disorders, including low pregnancy rates, irregular estrus cycle and low little size. To investigate these reasons, we assessed estrus behavior (standing response) and plasma $17{\beta}$-estradiol ($E_2$) level, which partly reflect reproductive function, during the estrus cycles after synchronization and superovulation by hormone treatments. Then, we analysed blood composition and expression of hEPO gene in TG pigs. Pigs were injected with PG600. After 10 days, pigs were fed with Regumate porcine for 6 days. Blood samples were collected from jugular vein. Analysis of blood composition and $E_2$ level were measured by Hemavet 950 and $E_2$ ELISA kit, respectively. And, the expression of hEPO gene in reproductive organs was quantitated by real-time RT-PCR. The percentage of estrus behavior in TG was significantly decreased. Hematocrit (HCT), hemoglobin (Hb) concentration and red blood cell (RBC) number were significantly higher in TG than wild type (WT). On the other hand, high expression of hEPO gene in TG was observed in the mammary gland as well as in the uterus. Moreover, plasma $E_2$ level was significantly higher in TG than WT. These results suggest that nonspecific expression of hEPO gene in the other organs of TG may affect blood composition and plasma $E_2$ level, thereby causing reproductive disorders.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1A
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• pp.25-33
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• 2011

The impact damage behavior of steel-strengthened concrete panels exposed to explosive loading is investigated. Since real explosion experiments require the vast costs to facilities as well as the blast and impact damage mechanisms are too complicated, numerical analysis has lately become a subject of special attention. However, for engineering problems involving blast wave and fragment impact, there is no single numerical method that is appropriate to the various problems. In order to evaluate the retrofit performance of a steel-strengthened concrete panel subject to blast wave and fragment impact loading, an explicit analysis program, AUTODYN is used in this work. The multi-solver coupling methods such as Euler-Lagrange and SPH-Lagrange coupling method in order to improve efficiency and accuracy of numerical analysis is implemented. The simplified and idealized two dimensional and axisymmetric models are used in order to obtain a reasonable computation running time. As a result of the analysis, concrete panels subject to either blast wave or fragment impact loading without the steel plate are shown the scabbing and perforation. The perforation can be prevented by concrete panels reinforced with steel plate. The numerical results show good agreement with the results of the experiments.