• Educational Technology International
• /
• v.18 no.1
• /
• pp.27-47
• /
• 2017

Smart devices have a variety of affordances to foster meaningful learning in elementary school. For the design of smart learning environments, more research is needed to understand students' smart device usage and their perception of learning with smart devices. In order to capture smart device usage profiles among elementary school students in South Korea, this study carried out Latent Profile Analysis with three constructs: information search, communication, and study. Participants (n=253), who ranged from the fourth to the sixth grade students, were classified into three profiles of smart device usage: low-activity, communication, and high-activity groups. The smart device usage profiles varied depending on smartphone usage experience, and the profiles were significantly related with smart device addiction, not with smart device usage ability. Perceptions of smart education were also significantly associated with the profiles. The high-activity group showed more positive attitudes toward smart education than the others, but no significant difference was found in regard to negative attitudes. Based on the findings, this study discussed implications for the use of smart devices in elementary school.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2007.08a
• /
• pp.356-356
• /
• 2007

• Journal of Magnetics
• /
• v.19 no.2
• /
• pp.197-204
• /
• 2014

A transcranial magnetic stimulation device is a complicated appliance that employs a switching power device designed for discharging and charging a capacitor to more than 1 kV. For a simple transcranial magnetic stimulation device, this study used commercial power and controlled the firing angle using a Triac power device. AC 220V 60 Hz, the power device was used directly on the tanscranial magnetic stimulation device. The power supply device does not require a current limiting resistance in the rectifying device, energy storage capacitor or discharge circuit. To control the output power of the tanscranial magnetic stimulation device, the pulse repetition rate was regulated at 60 Hz. The change trigger of the Triac gate could be varied from $45^{\circ}$ to $135^{\circ}$. The AVR 182 (Zero Cross Detector) Chip and AVR one chip microprocessor could control the gate signal of the Triac precisely. The stimulation frequency of 50 Hz could be implemented when the initial charging voltage Vi was 1,000 V. The amplitude, pulse duration, frequency stimulation, train duration and power consumption was 0.1-2.2T, $250{\sim}300{\mu}s$, 0.1-60 Hz, 1-100 Sec and < 1 kW, respectively. Based on the results of this study, TMS can be an effective method of treating dysfunction and improving function of brain cells in brain damage caused by ischemia.

• Human Ecology Research
• /
• v.59 no.2
• /
• pp.157-168
• /
• 2021

The purpose of this study was to examine the pathways between mothers' inappropriate smart device usage habits, preschoolers' immersion tendency and self-regulation, and children's cognitive ability. The subjects of the study were 308 preschoolers aged 4 and 5 years and their mothers in Seoul, Gyeonggi-do, Incheon, Gangwon-do, Daejeon, Busan, and Mokpo. Data were analyzed with descriptive statistics, t-test, one-way ANOVA, and Pearson correlation using the SPSS 25 program. A sequential mediation model was analyzed using the AMOS 22 program. Mothers' inappropriate smart device usage habits were found to have a negative effect on the preschoolers' self-regulation, and this association was mediated by the preschoolers' smart device immersion tendency. These findings show the mechanisms through which mothers' inappropriate smart device usage habits negatively affect preschoolers' smart device immersion and self-regulation which, in turn, has a negative impact on cognitive ability

• Journal of Biosystems Engineering
• /
• v.41 no.1
• /
• pp.21-33
• /
• 2016

Purpose: In order to ensure that vegetable seedlings (with a soil block around their roots) are planted in an upright orientation after metering in a vegetable transplanter, they need to be dropped freely from a certain height. The walk-behind hand-tractor-powered machines do not have sufficient space to drop the seedlings from that height. In the present work, a hopper-type planting device was developed for the walk-behind hand-tractor-powered vegetable transplanter to ensure that the soil block seedlings are planted in an upright orientation. Methods: Various dimensionless terms were developed based on the dimensional analysis approach, and their effect on the planting of soil block seedlings in an upright orientation (planting efficiency) was studied. The optimum design dimensions of the hopper-type planting device were identified by the Taguchi method of optimization. Results: The ratio of the height of free fall to the sliding distance of the seedling on the surface of the hopper had the highest influence on planting efficiency. The planting efficiency was highest for plants with a height $15{\pm}2cm$. The plant handling Froude number, in interaction with the design of the hopper-type planting device, also significantly affected the planting efficiency. Of the hopper design factors, the length of the slide of the seedlings on the surface of the hopper was most important, and induced sufficient velocity and rotation to cause the seedling to fall in an upright orientation. An evaluation of the performance of the planting device under actual field conditions revealed that the planting efficiency of the developed planting device was more than 97.5%. Conclusions: As the seedlings were fed to the metering device manually, an increase in planting rate increased missed plantings. The planting device can be adopted for any vegetable transplanter in which the seedlings are allowed to drop freely from the metering device.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2008.06a
• /
• pp.112-113
• /
• 2008

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.112-112
• /
• 2012

Graphene has been considered as one of the potential post Si-materials due to its high mobility. [1] However, since graphene is semi-conductor with zero band gap, it is difficult to achieve high Ion/Ioff ratio, one of the most important requirements for commercial devices. There have been many attempts to open its band gap for high Ion/Ioff ratio, but most of them end up lowering the mobility. [2-5] Thus, we proposed and demonstrated a new device structure for graphene transistor based on one of the unique properties of graphene for high Ion/Ioff: using this approach, we were able to achieve the ratio over $10^5$. [6] Our device has several major advantages over previously proposed graphene based electronic devices. Since our device does not alter the given properties of graphene, such as opening the band gap, it has no fundamental issues on mobility degradations. In addition, our device is fully compatible with current Si technology and we were able to fabricate the devices with 6 inch wafer scale with CVD (Chemical Vapor Deposition) grown graphene. In this presentation, we will discuss about the details of our graphene device including the device structure and the detailed understanding of working mechanism. We will present device characteristics including I-V curves with $10^5$ on/off ratio. We will also present the performance of an inverter based on our devices. Finally, we will discuss the current issues and their potential solutions.

• Proceedings of the IEEK Conference
• /
• 2003.07b
• /
• pp.751-754
• /
• 2003

Metamorphic HEMTs (MHEMTs) have emerged as excellent challenges for the design and fabrication of high-speed HEMTs for millimeter-wave applications. Some of improvements result from improved mobility and larger conduction band discontinuity in the channel, leading to more efficient modulation doping, better confinement, and better device performance compared with pseudomorphic HEMTs. We have studied the calibration on the DC and RF characteristics of the MHEMT device using I $n_{0.53}$G $a_{0.47}$As/I $n_{0.52}$A1$_{0.48}$As modulation-doped heterostructure on the GaAs wafer. For the optimized device performance simulation, we calibrated the device performance of 0.1-${\mu}{\textrm}{m}$ $\Gamma$-gate MHEMT fabricated in our research center using the 2D ISE-DESSIS device simulator. With this calibrated parameter set, we have obtained very good reproducibility. The device simulation on the DC and RF characteristics exhibits good reproducibility for our 0.1-${\mu}{\textrm}{m}$ -gate MHEMT device compared with the measurements. We expect that our calibration result can help design over-100-GHz MHEMT devices for better device performance.ormance.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.1
• /
• pp.21-26
• /
• 2012

Haptic device is regarded as the human machine interface technology for easier, more accurate, and intuitive operation. The purpose of this study is to define driver's affection on the haptic device in terms of its design factor : the color of haptic lighting as independent factor. This paper is studied to improve the cognitive ability of existing vehicle haptic device used by only a tactile feedback. On the color feedback usability evaluation, the lmino haptic device is used by adding color feedback to the existing vehicle haptic device. The emotional factor that driver has on the haptic device is extracted by the sensibility analysis. As a result, it is possible to suggest the design direction that satisfies the driver.

• The Journal of the Korea Contents Association
• /
• v.13 no.5
• /
• pp.19-27
• /
• 2013

This paper implements the standby power control system composed of a master device and slave devices. The standby power is managed by cutting power supply after controlling the relay of a slave device based on the authentication of master device's RFID card. RFID interface and wireless communication module are embedded in a master device, and one master device is linked with many slave devices in wireless. Each slave device executes the operation needed in power control independently. We implements the function of manual power on/off system in a slave device, and the function of user ID enrollment by switch manipulation in a master device. Also this system can communicate bidirectionally in wireless and runs on TinyOS. The result of experiment shows that the user authentication is executed in a master device and this authenticated information is transmitted to a slave device in wireless, and standby power is cutted by controlling the relay of a slave device. Installing this system in a building or an office, we can expect energy saving.