• Bulletin of the Korean Chemical Society
• /
• v.17 no.3
• /
• pp.245-253
• /
• 1996

A topological theory has been introduced to explain and evaluate the fractional volumes of system materials, the change of the weight and concentration of monomer molecules, molecular weight distribution, and interaction functions of polymer-polymer and polymer-oligomer, etc. for dispersion polymerization. The previous theory of Lu et al. has offered only an incomplete simulation model for dispersion polymer systems, whereas our present one gives a general theoretical model applicable to all the polymerization systems. The theory of Lu et al. considered only the physical property term caused by interaction between matters of low molecular weight (i.e., diluent, monomer, and oligomer) and polymer particles without dealing with physical properties caused by the structure of polymer networks in polymer particles, while our theory deals with all physical effect possible, caused by the displacement of not only entangled points but also junction points in polymer particles. The theoretically predictive values show good agreement with the experimental data for dispersion polymerization systems.

• Educational Technology International
• /
• v.24 no.1
• /
• pp.1-27
• /
• 2023

This study aimed to examine an augmented reality-based teaching simulation in a mobile application. We examined how AR-enabled interactions affect users' perceived scenario usefulness and avatar realism. The participants were forty-six undergraduate students. We randomly grouped them into two conditions: AR and Non-interactive video groups with equal sample sizes. This study employed an experimental design approach with a one-way multivariate analysis of variance with repeated measures. The independent variable is the presence/absence of AR interaction with a mobile application. The dependent variables were avatar realism and scenario usefulness. The measures explored how the student avatar's emotional intensity in a scenario influences user perception. The results showed that participants in the AR-interaction group perceived avatar realism significantly higher than those in the non-interactive video group. Also, participants perceived the high emotional intensity scenario (aggression toward peers) to be significantly higher usefulness than the low emotional intensity scenario (classroom disruption).

• Educational Technology International
• /
• v.18 no.2
• /
• pp.73-99
• /
• 2017

The learning analytics dashboard (LAD) is a supporting tool for teaching and learning in its personalized, automatic, and visual aspects. While several studies have focused on the effect of using dashboard on learning achievement, there is a research gap concerning the impacts of learners' characteristics on it. Accordingly, this study attempted to verify the differences in learning achievement depending on learning motivation level (high vs. low) and dashboard intervention (use vs. non-use). The final participants were 231 university students enrolled in a basic statistics course. As a research design, a 2 × 2 factorial design was employed. The results showed that learning achievement varied with dashboard intervention and the interaction effect was significant between learning motivation and dashboard intervention. The results imply that the impact of LAD may vary depending on learner characteristics. Consequently, this study suggests that the dashboard interventions should be offered after careful consideration of individual students' differences, particularly their learning motivation.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2023.11a
• /
• pp.489-490
• /
• 2023

기계 학습에서 데이터 및 기능은 기계 학습의 상한을 결정한다.이러한 기능은 산업 생산에서 과도한 데이터 양과 유형으로 인해 상당한 추가 비용이 발생할 수 있다. 따라서 적절한 특징 처리 방법이 매우 중요해졌다. 대부분의 기존 특징 처리 방법은 특징 엔지니어링을 기능 검색 문제, 즉 모델 성능을 최적화할 수 있는 기능 변환 작업을 검색하는 것으로 추상화한다. 그러나 자동 특징 엔지니어링의 경우 검색량과 변환 조합의 수가 매우 많기 때문에 요인 분해 기반 모델을 사용하여 벡터 곱셈을 통해 상호 작용을 측정하면 조합 특징의 패턴을 자동으로 학습하는 방법이 특히 효율적이다. xDeepFM 은 명확한 방식으로 특징적인 상호작용을 생성하도록 설계된 새로운 Compressed Interaction Network (CIN)를 제안한다. 여기에 제시된 Low-rank Compressed Interaction Network(LRCIN )은 xDeepFM 접근 방식에서 CIN 네트워크의 단순화된 개선을 기반으로 하며 xDeepFM 에 주의 메커니즘을 추가하여 보다 정확하게 예측된다. 실험 결과에 따르면 모델은 계산 복잡성을 단순화할 뿐만 아니라 예측 정확도도 다른 모델보다 훨씬 우수한다.

• Journal of Aerospace System Engineering
• /
• v.17 no.5
• /
• pp.11-18
• /
• 2023

The architecture of the Fuel Thermal Management System (FTMS) in a commercial aircraft engine was built to model and simulate the fuel system. The study shows the thermal interactions between the fuel and engine lubrication oil through the mission profile of a high bypass ratio, two-spool turbofan engine. Fuel temperature was monitored as it flowed through each sub-component of the fuel system during the mission. The heat load in the fuel system strongly depended on the fuel flow rate, and was significantly increased for the periods of cruise and descent with decrease of fuel flow rate, rather than for the periods of take-off. Due to the thermal interaction in the pump housing, the fuel temperature at the outlet of the low-pressure pump was increased (4.0, 9.2, and 30.0) % over the case without thermal interaction for take-off, cruise, and descent, respectively.

• Journal of Astronomy and Space Sciences
• /
• v.32 no.4
• /
• pp.289-295
• /
• 2015

By adopting a 2D time-dependent wave code, we investigate how mode-converted waves at the Ion-Ion Hybrid (IIH) resonance and compressional waves propagate in 2D density structures with a wide range of field-aligned wavenumbers to background magnetic fields. The simulation results show that the mode-converted waves have continuous bands across the field line consistent with previous numerical studies. These waves also have harmonic structures in frequency domain and are localized in the field-aligned heavy ion density well. Our results thus emphasize the importance of a field-aligned heavy ion density structure for ultra-low frequency wave propagation, and suggest that IIH waves can be localized in different locations along the field line.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.5 no.2
• /
• pp.10-15
• /
• 2006

An introduction to orthogonal cutting model by FEM is given, followed by a review of similar work. The cutting process is treated as quasi-static and strain rate insensitive, so the model is applicable only to low speed cutting operation. Chip separation is accomplished along a predefined cutting path by means of an element death procedure. Contact elements with friction capability are used to model the interaction between the tool and the workpiece. FEM results are compared with cutting experiments with low speed for brass, and good correlations are found.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.9
• /
• pp.814-821
• /
• 2007

A hybrid method is presented for efficient computation of turbulent flow noise at low Mach numbers. In this method, the turbulent flow field is computed by incompressible large eddy simulation (LES), while the acoustic field is computed with the linearized perturbed compressible equations (LPCE) derived in this study. Since LPCE is computed on the rather coarse acoustic grid with the flow variables and source term obtained by the incompressible LES, the computational efficiency of calculation is greatly enhanced. Furthermore, LPCE suppress the instability of perturbed vortical mode and therefore secure consistent and stable acoustic solutions. The proposed LES/LPCE hybrid method is applied to three low Mach number turbulent flow noise problems: i) circular cylinder, ii) isolated flat plate, and iii) interaction between cylinder wake and airfoil. The computed results are closely compared with the experimental measurements.

• Wind and Structures
• /
• v.15 no.3
• /
• pp.263-283
• /
• 2012

This paper presents a framework of nonlinear dynamic analysis of a low-speed moving maglev (magnetically levitated) vehicle subjected to cross winds and controlled using a clipped-LQR actuator with time delay compensation. A four degrees-of-freedom (4-DOFs) maglev-vehicle equipped with an onboard PID (Proportional-Integral-Derivative) controller traveling over guideway girders was developed to regulate the electric current and control voltage. With this maglev-vehicle/guideway model, dynamic interaction analysis of a low-speed maglev vehicle with guideway girders was conducted using an iterative approach. Considering the time-delay issue of unsynchronized tuning forces in control process, a clipped-LQR actuator with time-delay compensation is developed to improve control effectiveness of lateral vibration of the running maglev vehicle in cross winds. Numerical simulations demonstrate that although the lateral response of the maglev vehicle moving in cross winds would be amplified significantly, the present clipped-LQR controller exhibits its control performance in suppressing the lateral vibration of the vehicle.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.53 no.3
• /
• pp.133-136
• /
• 2004

Low-Pressure inductively coupled RF discharge sources have important industrial applications mainly because they can provide a high-density electrodeless plasma source with low ion energy and low power loss. In an inductive discharge, the RF power is coupled to the plasma by an electromagnetic interaction with the current flowing in a coil. In this paper, the experiments have been focussed on the electric characteristic and carried out using a single Langmuir probe. The internal electric characteristics of inductively coupled Ar RF discharge at 13.56(MHz) have been measured over a wide range of power at gas pressure ranging from 1∼70(mTorr).