• Information and Communications Magazine
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• v.30 no.10
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• pp.79-85
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• 2013

By interacting with external wireless sensors, smartphones can gather high-fidelity data on the surrounding environment to develop various environment-aware, personalized applications. In this work we introduce the sensor virtualization module (SVM), which virtualizes external sensors so that smartphone applications can easily utilize a large number of external sensing resources. Implemented on the Android platform, our SVM simplifies the management of external sensors by abstracting them as virtual sensors to provide the capability of resolving conflicting data requests from multiple applications and also allowing sensor data fusion for data from different sensors to create new customized sensors elements. We envision our SVM to open the possibilities of designing novel personalized smartphone applications.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.23-24
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• 2015

In this talk, we will present what we believe is the state-of-the-art of the numerical modeling and simulation of the combustion processes as they relate to typical scramjet engines. The free-stream Mach number is hypersonic, but the speed is not sufficiently decelerated at the inlet/isolator, as in ramjets, so that combustion takes place under supersonic conditions. This creates some difficulties for most turbulence-combustion models. We delve into the details of these problems, by discussing the software programs that have a long track record for scramjet combustion simulation; with a focus on the accuracy of the baseline numerical methods used, the turbulence modeling/simulation approach, the comparative fidelity of the turbulence-combustion interaction models, ability to simulate premixed/non-premixed/partially-premixed, quenching/re-ignition capabilities, the numerical spark-plug method, Damkholer number regimes supported, and the effects of variable Prandtl, Schmidt, and Lewis numbers. Validation results from high-speed and low-speed combustion applications will also be presented.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.123-126
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• 2013

Combustor development requires high fidelity simulation capable of predicting recirculation zone (RZ), temperature field, and pollutant emission. Swirling flow is widely used in combustor for its benefits in efficient mixing and flame stabilization by RZ. Large eddy simulation (LES) is used to calculate swirling flow in an expanding pipe [1], and shows higher accuracy than RANS. Reactive flow modeling using LES and flamelet model is validated with experiments by Barlow et al. [4] and Masri et al. [3]. Finally, heat transfer simulation of Samsung Techwin's combustor liner is presented.

• Nuclear Engineering and Technology
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• v.49 no.6
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• pp.1189-1198
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• 2017

Computer-aided design (CAD)-based Monte Carlo radiation transport is of value to the nuclear engineering community for its ability to conduct transport on high-fidelity models of nuclear systems, but it is more computationally expensive than native geometry representations. This work describes the adaptation of a rendering data structure, the signed distance field, as a geometric query tool for accelerating CAD-based transport in the direct-accelerated geometry Monte Carlo toolkit. Demonstrations of its effectiveness are shown for several problems. The beginnings of a predictive model for the data structure's utilization based on various problem parameters is also introduced.

• Advances in aircraft and spacecraft science
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• v.4 no.2
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• pp.125-144
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• 2017

This paper summarises the design of a gust generator and the comparison between high fidelity numerical results and experimental results. The gust generator has been designed for a low subsonic wind tunnel in order to perform gust response experiments on wings and assess load alleviation. Special attention has been given to the different design parameters that influence the shape of the gust velocity profile by means of CFD simulations. Design parameters include frequency of actuation, flow speed, maximum deflection, chord length and gust vane spacing. The numerical results are compared to experimental results obtained using a hot-wire anemometer and flow visualisation by means of a tuft and smoke. The first assessment of the performance of the gust generator showed proper operation of the gust generator across the entire range of interest.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.326-328
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• 2018

최근 4K/8K 급 초고품질 콘텐츠의 서비스에 관심이 집중되는 만큼 스트리밍 서비스에 대한 연구도 활발히 이루어지고 있다. 하지만 단일 PC 성능의 한계로 인해 SW 기반 영상 처리에 어려움을 겪고 있다. 본 논문에서는 분산 처리를 통해 실시간 영상 처리가 가능하도록 시스템을 제안한다. 제안한 시스템은 영상 패킷 분석 및 분할, 분산 트랜스코딩, 패킷 통합 단계로 이루어지며 Hadoop 과 Spark 를 이용하여 실시간 분산 처리를 지원한다. 실험 결과는 초고품질 입력 영상($3840{\times}2160@60Hz$, YCbCr 4:2:2, 10-bit)에 대해 평균 74.47fps 의 트랜스코딩 속도를 보인다.

• Korean Journal of Metals and Materials
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• v.48 no.2
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• pp.163-168
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• 2010

We here describe the laser-direct patterning of nanostructured metal thin films. This method involves light-matter interaction in which a pulsed laser beam impinging on the film generates a thermoelastic force that plays a role to detach the film from the substrate or underlying layers. A moderate cohesion of the nanostructured film enables localized desorption of the material upon irradiation by a spatiallymodulated laser beam, giving good fidelity with the transfered pattern. This photoresist-free process provides a simple high-resolution scheme for patterning metal thin films.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.30-43
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• 2021

In the 2D/1D method, a global adjoint CMFD based on the generalized equivalence theory is built to synthesize the 2D radial MOC adjoint and 1D axial NEM adjoint calculation and also to accelerate the iteration convergence of 3D whole-core adjoint transport calculation. Even more important, an advanced yet accurate two-level (TL) CMFD acceleration technique is proposed, in which an equivalent one-group adjoint CMFD is established to accelerate the multi-group adjoint CMFD and then to accelerate the 3D whole-core adjoint transport calculation efficiently. Based on these method, a new code is developed to perform 3D adjoint neutron flux calculation. Then a set of VERA and C5G7 benchmark problems are chosen to verify the capability of the 3D adjoint calculations and the effectiveness of TL CMFD acceleration. The numerical results demonstrate that acceptable accuracy of 2D/1D adjoint calculations and superior acceleration of TL CMFD are achievable.

• International Journal of Contents
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• v.18 no.1
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• pp.85-97
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• 2022

Students' perceptions of generosity and fairness in lecture evaluation and grades, communication with professors, and self-fidelity and satisfaction during the COVID-19 situation were statistically analyzed by surveying students at M university in Daejeon. These data were analyzed in the context of parameters that might impact online class lecture evaluations, namely gender and school year. Descriptive analysis shows students' perceptions of online lectures are significantly high. As for differences by gender and school year, the t-test results indicate female students generally have better perceptions of online classes than male students. However, there is no statistical difference between male and female students regarding the generosity of lecture evaluation. Also, ANOVA test results show that as the school year increases, the general perceptions for online classes become negative. However, there is no statistical difference by school year regarding the generosity of lecture evaluation. Regression analysis shows that the "perceptual generosity of grades" most significantly influenced the "perceptual generosity of lecture evaluation."

• Advances in aircraft and spacecraft science
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• v.10 no.6
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• pp.521-543
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• 2023

Reynolds-averaged Navier-Stokes (RANS) models are extensively employed in industrial settings for the purpose of simulating intricate fluid flows. However, these models are subject to certain limitations. Notably, disparities persist in the Reynolds stresses when comparing the RANS model with high-fidelity data obtained from Direct Numerical Simulation (DNS) or experimental measurements. In this work we propose an approach to mitigate these discrepancies while retaining the favorable attributes of the Menter Shear Stress Transport (SST) model, such as its significantly lower computational expense compared to DNS simulations. This strategy entails incorporating an explicit algebraic model and employing a neural network to correct the turbulent characteristic time. The imposition of realizability constraints is investigated through the introduction of penalization terms. The assimilated Reynolds stress model demonstrates good predictive performance in both in-sample and out-of-sample flow configurations. This suggests that the model can effectively capture the turbulent characteristics of the flow and produce physically realistic predictions.