• International Journal of Fluid Machinery and Systems
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• v.10 no.2
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• pp.164-175
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• 2017

Francis turbines are often operated over a wide load range due to high flexibility in electricity demand and penetration of other renewable energies. This has raised significant concerns about the existing designing criteria. Hydraulic turbines are not designed to withstand large dynamic pressure loadings on the stationary and rotating parts during such conditions. Previous investigations on transient operating conditions of turbine were mainly focused on the pressure fluctuations due to the rotor-stator interaction. This study characterizes the synchronous and asynchronous pressure and velocity fluctuations due to rotor-stator interaction and rotating vortex rope during load variation, i.e. best efficiency point to part load and vice versa. The measurements were performed on the Francis-99 test case. The repeatability of the measurements was estimated by providing similar movement to guide vanes twenty times for both load rejection and load acceptance operations. Synchronized two dimensional particle image velocimetry and pressure measurements were performed to investigate the dominant frequencies of fluctuations, vortex rope formation, and modes (rotating and plunging) of the rotating vortex rope. The time of appearance and disappearance of rotating and plunging modes of vortex rope was investigated simultaneously in the pressure and velocity data. The asynchronous mode was observed to dominate over the synchronous mode in both velocity and pressure measurements.

• Journal of Information Technology Services
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• v.21 no.3
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• pp.73-87
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• 2022

As the COVID-19 pandemic continues to prolong, non face-to-face, online classes has become the new normal in education. To examine the effect of course types and course delivery modes on student course satisfaction, the study analyzed survey data collected from 2,743 students enrolled in a 4-year university located in a metropolitan area. Basic Frequency analysis as well as keyword network analysis were used to analyze student survey data. The main results and implications of the study are as follows. First, the survey results indicated that students preferred asynchronous classes over synchronous online classes. This tendency was consistent regardless of student grades and majors as well as the course type. However, students majoring in more practice-oriented disciplines tend to prefer synchronous online classes and blended classes, and this tendency gets stronger with courses in major. Second, the keyword network analysis results further indicated that interactivity may play an important role in both synchronous and asynchronous online course satisfaction.

• English Language & Literature Teaching
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• v.13 no.4
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• pp.33-58
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• 2007

The present paper aims at comparing the two modes of CMC - synchronous and asynchronous - in terms of discourse markers used in turn-initial positions. It further attempts to examine the viability and limitations of these two modes of CMC in fostering EFL learners' face-to-face conversation skills. For these purposes, the present study analyzed 33 Korean EFL learners' Web chat and E-mail exchange data. Discourse markers in the participants' Web chat transcripts and those in their E-mail transcripts were identified and then compared in terms of their frequency and functions. The analysis revealed that the participants show difference in their preference for discourse markers depending on the modes of CMC. Also, the functions of discourse markers used for Web chat showed were strikingly different from those for e-mail. Especially, e-mail discourse markers revealed greater discrepancy from the markers in face-to-face conversation. The differences were found to be attributable to the time factor involved with the turn-taking systems of the two modes of CMC, especially the degree of instantaneousness in their turn-taking. Findings suggest that the turn taking skills and discourse marker use in CMC is not applicable to face-to-face conversation contexts. Pedagogical implications are discussed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.4
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• pp.85-94
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• 2003

The asynchronous design methods proved to have the higher performance in power consumption and execution speed than synchronous ones because it just needs to activate the required module without feeding clock in the system. Despite the advantage of CISC machine providing the variable addressing modes and instructions, its execution scheme is hardly suited for a synchronous Pipeline architecture and incurs a lot of overhead. This paper proposes a novel asynchronous pipeline architecture, A80sl, whose instruction set is fully compatible with that of Intel 80C51, an embedded micro controller. We classify the instructions into the group keeping the same execution scheme for the asynchronous pipeline and optimize it eliminating the bubble stage that comes from the overhead of the multi-cycle execution. The new methodologies for branch and various instruction lengths are suggested to minimize the number of states required for instructions execution and to increase its parallelism. The proposed A80C51 architecture is synthesized with 0.35${\mu}{\textrm}{m}$ CMOS standard cell library. The simulation results show higher speed than that of Intel 80C51 with 36 MHz and other asynchronous counterparts by 24 times.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.772-775
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• 1997

A high speed tracking control for 6-6 Stewart platform manipulator is performed by employing the joint-axis sliding mode control based on dynamics. Because of the complex dynamics and kinematics of Stewart platform manipulator, two computer systems, consisting of a PC and a DSP, are adopted, so that real time tasks are run in synchronous and asynchronous modes. It is experimentally proven that the proposed control system leads to an easy to implement and effective control task, and it can achieve the high performance tracking control under the high speed and severe payload condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.903-911
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• 1999

A high speed tracking control system for 6-6 Stewart platform manipulator is designed for performing the model based joint-axis sliding mode control. Because of the complex dynamics and kinematics of the Stewart platform manipulator, two computer systems, consisting of a PC and a DSP, are adopted, so that real time tasks are run in synchronous and asynchronous modes. It is experimentally proven that the proposed control system makes the convenience in implementation of model based tracking control, so that it can achieve effective tracking control under relatively high speed and additional payload conditions.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.357-362
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• 2003

The pathway producing imide ring closure during the thermal imidization of poly(amic acid) (PAA) was investigated in detail using a new analytical method, two-dimensional (2D) Raman correlation spectroscopy. The signs of the cross peaks in synchronous spectra provided evidence of the thermal imidization of PAA into PI as the heating temperature increased. The signs of the cross peaks in asynchronous spectra suggested that the imide-related modes changed prior to the amide or carboxylic mode, which indicates that cyclization occurred before the amide proton was abstracted.

• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.262-267
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• 2006

For growing need for the multimedia application in the vehicles, the MOST protocol has been focused on. The MOST protocol supports three kinds of communication modes; short control message, asynchronous packets, and reserved synchronous stream data. Because of a variety of transportation, the MOST is suitable for various applications in vehicle environment. In this paper, we implemented embedded system which is MOST-enabled AMS platform and tested the network communication operation through the control port and the synchronous channel of the source port. We implemented the prototype platforms which communicate each other on the MOST's POF network. Moreover we implemented the DivX decoder attached AMS platform and verified the operation by transferring the video stream and the control messages through the MOST network.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.245-251
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• 2022

In the context of the pandemic, educational institutions had to ensure an instant transition to remote technological models of communication within the new conditions of the educational environment. The purpose of the academic paper lies in determining the role of the communicative model of educational transformations in the realities of (post) modernity. The research methodology is based on a survey of 120 students from 10 higher educational institutions (HEIs) of Ukraine through an online form regarding the importance of live communication during a pandemic. Results. The communicative model changed significantly during the pandemic - the interaction was mainly due to technologies. The research has identified four communication models of educational transformations under the conditions of the pandemic, depending on learning models. The first traditional model of distance learning involves distance learning; the second model involves contact remote training using remote educational technologies; the third model is blended learning, which combines remote and traditional learning formats, synchronous and asynchronous modes of interaction; the fourth model is traditional contact training. The empirical study of the effectiveness of communication models proves that live communication remains extremely important for learning and understanding of educational materials by students, and technology has provided support for such communication. Along with this, seminars and video lectures with presentations combining live communication and communication technologies are as important as digital learning tools. The most effective teaching method for mastering and memorizing educational material was a live dialogue with a teacher at seminars in ZOOM, followed by individual written assignments on the studied topic.