• Transactions of Materials Processing
• /
• v.19 no.4
• /
• pp.236-241
• /
• 2010

The frictional behavior of bare steel sheet highly depends on surface roughness. It was investigated that the change of surface roughness of bare steel sheet due to deformation for each forming mode. The flat type friction test was done to check the effect of surface roughness change on frictional characteristics of bare steel sheet. As increasing the deformation, the Ra value was increased at stretching forming mode and drawing forming mode, however the change of Pc showed different trends. The Pc was decreased as increasing stretch deformation but increased at compression deformation. At drawing forming mode, the friction coefficient was increased as deformation was increased after initial big drop with drawing oil. As deformation was increased, the friction coefficient was decreased with drawing oil at stretching forming mode. The results show that the deformation changes the surface roughness and frictional characteristics of steel sheet but the effect depends on the forming mode.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.49 no.2
• /
• pp.116-119
• /
• 2000

A hybrid SOI bipolar-mode field effect transistor (BMFET) is proposed to improve the current gain. The device characteristics are analyzed and verified numerically for BMFET mode, DMOS mode, and hybrid mode by MEDICI simulation. The proposed SOI BMFET exhibits 30 times larger current gain in hybrid-mode operation by connecting DMOS gate to the p+ gate of BMFET structure as compared with the conventional structure without sacrifice of breakdown voltage and leakage current characteristics. This is due to the DMOS-gate-induced hybrid effect that lowers the barrier of p-body and reduces the charge in p-body.

• Educational Technology International
• /
• v.24 no.1
• /
• pp.29-51
• /
• 2023

This study examined the moderating effect of course satisfaction with class on the relationship between the mode of course delivery and learning presence and performance in university settings. Results showed that there was a moderating effect of the course satisfaction on the relationship between course delivery mode and learning presence. Specifically, higher satisfaction with instructor's teaching activities was associated with improved learning presence in face-to-face, blended, and online learning, in that order. However, there was no significant moderating effect on academic performance. These findings suggest that universities should consider not only the mode of course delivery and highlight the importance of systematic course design by instructors.

• The Research Journal of the Costume Culture
• /
• v.22 no.1
• /
• pp.99-111
• /
• 2014

This study looked into the scarcity effect based on the consumers' self-regulatory modes and determined the effect that such a regulatory mode and that quantity-scarcity messages would have on evaluations of fashion products. To that end, the study used a 2 (regulatory mode: assessment mode/locomotion mode)${\times}2$ (message type: quantity-scarcity message/non-scarcity message) between-subjects factorial design in which buying impulsiveness was presented as a mediator variable that showed differences in product evaluations depending on the message type and on the presence of a self-regulatory mode. The results of this study showed that locomotion-oriented consumers evaluated products more positively compared to assessment-oriented consumers when the quantity-scarcity message was presented. When a non-scarcity message was presented, no significant difference was observed in product evaluations based on the consumers' self-regulatory modes. In addition, buying impulsiveness in consumers served a mediator role in the evaluations of fashion products. The results of this study imply that a clear understanding of consumers is a prerequisite for maximizing the scarcity effect and that companies need to differentiate in terms of the way they use scarcity messages based on consumers' self-regulatory modes.

• Journal of the Korean Ceramic Society
• /
• v.35 no.7
• /
• pp.671-678
• /
• 1998

Hertzian indentation tests with sphere indenters were used to study the mechanical properties of glass-in-filtrated alumina and spinel composites and evaluated the effect of preform microstructure and evaluated the effect of preform microstructure and glass con-tents on contanct damage and strength. The spinel composite showed more brittle behavior than the alumina composite which is verified from indentation stress-strain curve cone cracks and quasi-plastic deformation developed at subsurface. Failure originated from either cone cracks(brittle mode) or deformation zone(quasi-plastic mode) above critical load for cracking(Pc) and yield ({{{{ {P }_{Y } }}) with the brittle mode more dominant in the spinels and the quasi-plastic mode more dominant in the aluminas. Even though brittle mode was dominant in the spinel composites the strength degradation from accumulation of damage above these critical loads was conspicuously small suggesting that the glass-infiltrated composites should be highly damage tolerant to the blunt contacts.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.7
• /
• pp.966-975
• /
• 2002

Acoustic behavior in baffled combustion chambers is numerically investigated by adopting linear acoustic analysis. Partial blade baffle, which is a variant of blade baffle, and hub-blade baffle with six blades are employed as baffle models. Through modal analysis, natural frequencies of each acoustic mode in baffled chambers are calculated and the reduction in natural frequencies caused by baffle installation is examined. Through harmonic analysis, acoustic pressure responses of each chamber to acoustic oscillating excitation are shown. The first tangential mode is found to be most sensitive to acoustic oscillation. Acoustic damping effect of baffle is quantified by damping factor. Damping effect of hub-blade baffle is the most appreciable and damping factor of partial blade baffle is much lower than that of blade baffle. Damping effect of six-blade baflle on the second tangential mode is as much as on the first tangential mode and hub-blade baffle can damp out appreciably the first tangential as well as the first radial mode with the aid of hub.

• Journal of Power Electronics
• /
• v.19 no.3
• /
• pp.727-743
• /
• 2019

This paper presents a pulse-width modulation strategy to eliminate the common mode voltage (CMV) with reduced CMV spikes in multilevel inverters since a high CMV magnitude and its fast variations dv/dt result in bearing failure of motors, overvoltage at motor terminals, and electromagnetic interference (EMI). The proposed method only utilizes the zero CMV states in a space vector diagram and it is implemented by a carrier-based pulse-width modulation (CBPWM) method. This method is generalized for odd number levels of inverters including neutral-point-clamped (NPC) and cascaded H-bridge inverters. Then it is extended to the over-modulation mode. The over-modulation mode is implemented by using the two-limit trajectory principle to maintain linear control and to avoid look-up tables. Even though the CMV is eliminated, CMV spikes that can cause EMI and bearing current problems still exist due to the deadtime effect. As a result, the deadtime effect is analyzed. By taking the deadtime effect into consideration, the proposed method is capable of reducing CMV spikes. Simulation and experimental results verify the effectiveness of the proposed strategy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.195-199
• /
• 2004

Recently, optical disc drives are required to have high density and capacity in according with development of high definition images and rapid increase of various informations. Consequently, the numerical aperture becomes larger, the wavelength of laser is coming to be short. However, it deteriorates rolling mode effect on an optical pickup actuator. Therefore, this paper proposes new design and optimization of tracking coils for reducing it. First, we verify that discord between the center of force and the center of mass by restrictions of design condition is an important factor of rolling mode effect. Then, in order to reduce it, we propose new design parameters of tracking coils. Finally, we reduce rolling mode effect through optimization of tracking coils using Taguchi method and response surface method.

• Journal of radiological science and technology
• /
• v.40 no.2
• /
• pp.213-218
• /
• 2017

Recently, as the number of high-risk pregnancies increases, the use of new techniques such as Doppler, which have higher acoustic power than in the past, has been increasingly used in prenatal diagnosis and guidelines have been set up by various organizations to prevent excessive exposure. Therefore, in this study, we tried to investigate the temperature change of the body surface for each test mode according to the long time ultrasound examination and to examine the exposure time which is not influenced by the thermal effect. B mode, C mode, and PD mode according to time, and the temperature difference between exposed and unexposed sites were compared. As a result, the B mode showed a significant difference in the temperature change from 10 minutes, 50 minutes after exposed, 20 minutes from the C mode, and 30 minutes from the PD mode (p<0.01). In all three modes, the temperature difference was different (p<0.000), and PD mode was the most sensitive to temperature change. Also, it was found that the temperature rise time was shortened with the increase of the ultrasonic exposure time. Therefore, it is recommended that ultrasonography to observe the embryo or fetus should be used only for diagnostic purposes, avoiding excessive test time.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2002.04a
• /
• pp.261-265
• /
• 2002

In the machining tool avoid vibration problem have an effect on high precision as well as statical and thermal characteristics. Therefore overcome this problem is essential to advance of machine tool and machining skill. Even though vibration arises owing to a variety of causes, in this paper vibration analysis of column as a major part of machine tool structures is presented. At this procedure vibration analysis applied to mode synthesis method using a attachment mode .