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This study examined the relationship between living up to parental expectations (LPE) and life satisfaction as well as the moderating effect of psychological separation on this relationship among South Korean college students. The participants ( N = 343) completed an online survey measuring the study variables. We divided psychological separation into conflictual independence (CI) and general independence (GI) and performed multiple regression analysis. The results revealed a positive association between LPE and life satisfaction. Our analysis also indicated that GI moderated the relationship between LPE and life satisfaction. Specifically, the positive association between LPE and life satisfaction was significant for participants with lower levels of GI. We discussed the significance of these findings and explained their implications for counseling settings in terms of cultural considerations.

Background: Nonalcoholic fatty liver disease dramatically improves after bariatric surgery, primarily due to improvements in hepatic insulin sensitivity. Since the procedure for gastric cancer surgery is very similar to that for bariatric surgery, we investigated changes in fatty liver following gastrectomy for gastric cancer according to the type of surgery.Methods: We evaluated hepatic steatosis in 212 early gastric cancer patients using Hounsfield units (HUs) on non-contrast computed tomography preoperatively and 6, 12, and 24 months after surgery. We compared the preoperative and postoperative liver-to-spleen HU ratio according to the type of surgery: Billroth I, Billroth II, and total gastrectomy with Roux-en-Y reconstruction. Results: The initial results (liver/spleen HUs and the liver-to-spleen HU ratio) did not significantly differ according to surgical group. After surgery, only patients who underwent total gastrectomy with Roux-en-Y exhibited significant changes in the liver-to-spleen HU ratio at 6 months. In 26 patients who had higher initial HU levels of the spleen than the liver, the liver-to-spleen HU ratio significantly increased from 0.836 to 1.115 at 6 months, 1.109 at 12 months, and 1.102 at 24 months (P

Cast-in-place anchors are being increasingly used in many applications including building construction, bridge, and power plants. The anchorage to concrete systems are subjected to tensile, shear and combined loads from a variety of loading circumstances including static, dynamic, and shock loading. Despite extensive studies on these systems, reliable numerical models for predicting the behavior of these anchors are still limited. Therefore, this paper investigated the tensile behaviour of cast-in-place anchorage to concrete systems, to propose an effective model for reproducing anchorage behavior using finite element (FE) methods. Experiments and code-based models for the anchorage system in tension were used to evaluate the numerical models for cast-in-place anchors in concrete, and the most suitable model, with advantages in accuracy and saving analysis time, was chosen. Finally, the FE model was used to study the tensile capacity and related dynamic increase factor (DIF) for various strain rates, anchor diameters, and embedment depths.

It is very important to ensure reliable performance of deep learning model for future dataset for healthcare. This is more pronounced in the case of patient generated health data such as patient reported symptoms, which are not collected in a controlled environment. Since there has been a big difference in influenza incidence since the COVID-19 pandemic, we evaluated whether the deep learning model can maintain sufficiently robust performance against these changes. We have collected 226,655 episodes from 110,893 users since June 2020 and tested the influenza screening model, our model showed 87.02% sensitivity and 0.8670 of AUROC. The results of COVID-19 pandemic are comparable to that of before COVID-19 pandemic.

As the number of cases for COVID-19 continues to grow unprecedentedly, COVID-19 screening is becoming more important. In this study, we trained machine learning models from the Israel COVID-19 dataset and compared models that used surveillance indices of COVID-19 and those that did not. The AUC scores were 0.8478±0.0037 and 0.8062±0.005 with and without surveillance information, respectively, and there was significant improvement when the surveillance information was used.

It is very important to ensure reliable performance of deep learning model for future dataset for healthcare. This is more pronounced in the case of patient generated health data such as patient reported symptoms, which are not collected in a controlled environment. Since there has been a big difference in influenza incidence since the COVID-19 pandemic, we evaluated whether the deep learning model can maintain sufficiently robust performance against these changes. We have collected 226,655 episodes from 110,893 users since June 2020 and tested the influenza screening model, our model showed 87.02% sensitivity and 0.8670 of AUROC. The results of COVID-19 pandemic are comparable to that of before COVID-19 pandemic.

As the number of cases for COVID-19 continues to grow unprecedentedly, COVID-19 screening is becoming more important. In this study, we trained machine learning models from the Israel COVID-19 dataset and compared models that used surveillance indices of COVID-19 and those that did not. The AUC scores were 0.8478±0.0037 and 0.8062±0.005 with and without surveillance information, respectively, and there was significant improvement when the surveillance information was used.

In this study, a gappy proper orthogonal decomposition (POD) method was applied to a steam reformer model with combustion, flow, and catalysis to determine the optimal number and placement of sensors. The dominant POD modes were identified based on a limited number of snapshots obtained from a spatial domain simulation, and the POD modal content was calculated from the corresponding gappy data. This information was used to estimate the differences between the sensor measurements and actual fields. The estimation results were utilized to verify the accuracies of gappy POD projections of 20 snapshots of the positions of six, three, and two sensors, and the sensor arrangements determined by using a proposed objective function were compared to those resulting from applying the conventional method. In addition, reconstructions based on gappy data were evaluated in four validation cases, and the accuracy and robustness of the sensor positions in various situations were confirmed. Consequently, this paper optimized sensor placement for the steam reformer in terms of temperature prediction and proposed modified the objective function which maintains orthogonality of the mask matrix.

The combination of steam reforming and HT-PEMFC has been considered as a proper set up for the efficient hydrogen production. Recycling anode off-gas is energy-saving strategy, which leads to enhance the overall efficiency of the HT-PEMFC. Thus, the recycling effect of anode off-gas on steam-reforming performance needs to be further studied. This paper, therefore, investigated that the combustion of anode off-gas recycled impacts on the steam reformer, which consists of premixed-flame burner, steam reforming and water-gas shift reactors. The temperature rising of internal catalyst was affected by lower heating value of fuels when the distance between catalyst and burner is relatively short, while by the flow rate of fuels and the steam to carbon ratio when its distance is long. The concentration of carbon monoxide was the lowest at 180 °C of LTS temperature, while NG and AOG modes showed the highest thermal efficiency at LTS temperature of 220–300 °C and 270–350 °C, respectively. The optimum condition of thermal efficiency to maximize hydrogen production was determined by steam reforming rather than water gas shift reaction. It was confirmed that the condition to obtain the highest thermal efficiency is about 650 °C of steam reforming temperature, regardless of combustion fuel and carbon monoxide reduction. The difference of hydrogen yield between upper and lower values is up to 1.5 kW as electric energy with a variation of thermal efficiency. Hydrogen yield showed the linear proportion to the thermal efficiency of steam reformer, which needs to be further increased through proper thermal management.

In this work, we applied and evaluated modified inferential proper orthogonal decomposition (POD)/machine learning (ML) to a steam reformer for 5-kW high-temperature proton-exchange membrane fuel cells (HT-PEMFC) involving heterogeneous chemical reactions, combustion, and fluid flow. The number of snapshots is limited by the inverse problem of a steam reformer yielding an intractable computational burden, and a limited number of snapshots and modes can yield unfavorable POD subspace projection results. In order to solve this problem, characteristic vectors are derived from the residual after POD projection and employed to the feature. We analyzed the details and distribution of the characteristic vector and investigated the extent of its influence on the inferential POD. Consequently, inferential POD/ML is improved by adding the characteristic vector of observation to the feature for ML.

We report the gas-sensing properties of pristine and SnS2 functionalized TeO2 nanowires (NWs). TeO2 NWs were synthesized by a vapor–liquid–solid growth method, and SnS2 functionalization was performed using an atomic layer deposition technique followed by thermal treatment. Structural and morphological analyses verified the formation of pristine and SnS2 functionalized TeO2 NWs with desired composition, phase, and morphology. Interestingly, sensing results showed that the pristine TeO2 NW gas sensor had better sensing properties relative to the SnS2 functionalized TeO2 NW gas sensor. An underlying sensing mechanism is explained in detail, and reasons for the decrease of sensing performance with the SnS2 functionalized TeO2 NW sensor was attributed to the coverage of TeO2 surface by the SnS2 nanoparticles.

An inverse transient analysis technique for detecting leaks in water pipe systems through proper orthogonal decomposition (POD) with a radial basis function network (RBFN) is proposed. To verify it...

Experimental analysis with a scale-reduction model enables data measurements and analysis of physical phenomena that could not be performed in a real model because of numerous constraining conditions and environmental regulations. In the present study, experimental analysis of a D-top model HRSG was conducted using a 1/12 scale-down model to simulate inlet duct flow behavior and pressure drop phenomena, and to evaluate numerical results. For a more accurate and reasonable study, the cold flow test was performed and pressure drop values of each section was adjusted considering geometric and dynamic similarities. Specifically, Euler and swirl numbers were considered as dynamic similitude procedures, and the log-Tchebycheff method was applied for effective data measuring. The flow uniformity at the rear section of the inlet duct and pressure drop values were measured, analyzed, compared with numerical results. Consequently, the experimental analysis rigorously evaluated the numerical results of the optimized model, which was proposed in the previous study.

The reactors designed for 5-kW high-temperature polymer electrolyte fuel cells are able to evaluate the performance of the steam reformer and each water–gas shift reactor independently. The goal of the experiments is to obtain the best overall performance for steam reforming while minimizing the CO concentration and maximizing the hydrogen yield. For this purpose, the performance of the steam reforming reactor unit with two types of flow paths was evaluated while evaluating the performance of various series of component combinations of the high-, middle-, and low-temperature shifts. Via experiment, thermal control followed by the appropriate heating and cooling mechanism is key to successful reaction performance. In addition to an individual unit-based experiment, numerical analyses were executed to understand the local chemical performance inside a reactor unit. These numerical analyses show good agreement with the experimental data measured at the outlet and provide a comprehensive detailed internal reaction mechanism such as the thermal conditions and CO concentration effect. Both experiments and numerical analyses can fundamentally improve the reaction performance by finding the optimal values of many control parameters.

A natural gas-based steam reformer for a domestic polymer electrolyte membrane fuel cell (PEMFC) system is thermodynamically analyzed with a special focus on the heat supply mechanism, which is critical to the endothermic steam reforming process. The interdependence of the reforming and combustion processes is evaluated through a characteristic study of heat transfer from the heat source to the reforming zone. Premixed combustion patterns may be affected by the inclusion of controlling means such as a metal fiber screen or burner placement. In this study, we attempted to enhance reforming performances of a reformer embedded in a 5 kW in-house PEMFC through modification of the combustion pattern by varying the type and placement of the burner and other operating conditions. Reforming input conditions such as steam-carbon ratio (SCR) and fuel distribution ratio (FDR) are also analyzed to quantify the overall performance such as thermal efficiency and fuel conversion rate. In our experiments involving three types of combustors—cylindrical metal fiber burner, flat type metal fiber burner and nozzle-mixing burner—the operating conditions are set so that the SCR and FDR are in the range 3.0–4.0 and 0.4–0.7, respectively. It is found that the cylindrical metal fiber burner at an appropriate location could improve thermal efficiency up to 79% by 10%, compared to other devices. This maximum thermal efficiency output is obtained with 0.63 FDR, which eventually yields 99% hydrogen conversion rate when using a cylindrical metal fiber burner, while the other burners produce 95% conversion. These outputs substantiate that the overall efficiency is strongly affected by an appropriate control for uniform temperature distribution on the catalyst layer.

In this study, the performance evaluation of a cylindrical natural-gas steam reformer is experimentally and numerically performed with a special focus on thermal operation conditions. The evaluation system is configured to probe the thermal and chemical characteristics of a steam reformer that does not employ a high temperature shift and a low temperature shift. The acquired experimental data is used to validate the proposed numerical model. A combination of experimental and numerical data provides detailed information leading to a better understanding of the internal reaction. An appropriate control of the heat source in the steam reformer is extremely important because the endothermic process is dominant throughout the catalyst layer. The results indicate that the thermal efficiency is enhanced by appropriately managing combustor heat, reactant concentration, and inflow rates as implemented by inlet gas control into the main reactor and combustor. A parametric study of operation control variables, such as Steam to carbon ratio (SCR) and combustible reactant ratio, could determine the optimal values for the highest thermal performance.

The HRSG extensively affects all performance of CCPPs. The inlet duct geometry of an HRSG is the most essential part for determining heat exchange in the main body, in terms of flow uniformity. In the present study, numerical analysis of the HRSG flow characteristics and design optimization of inlet duct geometry for improving flow uniformity at the front section of the main body were performed to meet the trend requirements. A new inlet duct geometry, which has maximum flow uniformity, was proposed through design optimization procedures using a genetic algorithm. Specifically, the actual operating condition of the D-top model HRSG was applied and the pressure recovery coefficient and diffuser efficiency were considered. In the optimized design, a recirculation area was formed at the top internal wall of the second expansion stage. Results indicate that the forming of the recirculation area improves flow uniformity by rotating movement and spreading the high-speed flow.

The synthesis of copper-reduced graphene oxide (RGO) sheets was investigated in order to control the agglutination of interfaces and develop a manufacturing process for copper-based composite materials based on spark plasma sintering. To this end, copper-GO (graphene oxide) composites were synthesized using a hydrothermal method, while the copper-reduced graphene oxide composites were made by hydrogen reduction. Graphene oxide-copper oxide was hydrothermally synthesized at 80 °C for 5 h, and then annealed at 800 °C for 5 h in argon and hydrazine rate 9:1 to obtain copper-RGO flakes. The morphology and structure of these copper-RGO sheets were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. After vibratory mixing of the synthesized copper-RGO composites (0-2 wt%) with copper powder, they were sintered at 600 °C for 5 min under100 MPa of pressure by spark plasma sintering process. The thermal diffusivity of the resulting sintered composite was characterized by the laser flash method at 150 °C.

This article presents the design and the development of a system composed of multiple FPGA components for autonomous robot cars. In the FPT'19 FPGA design competition, there are several tasks for image recognition such as driving lane, traffic signal, human or object on the road. To promote team development, component-oriented FPGA development is employed. In this paper, we describe the whole system design by integrating FPGA components for autonomous driving, the design of each FPGA component and its development process.

The prediction of combustion instability is important to avoid an obvious threat to the structural safety and the motor performance because it affects the apparent response function of the propellant, the burning rate, and a mean flow Mach number at the local surface. The combustion instability occurs in case acoustic waves were coupled with the combustion/flow dynamic frequency. In this paper, an acoustic instability model is derived from the nonlinear wave equation for analysing acoustic dynamics in solid rocket motors. The chamber pressure and burning rate effects on combustion instability have been investigated.

The thermal characteristics of a natural-gas based cylindrical steam reformer coupled with a combustor are investigated for the use with a 5 kW polymer electrolyte membrane fuel cell. A reactor unit equipped with nickel-based catalysts was designed to activate the steam reforming reaction without the inclusion of high-temperature shift and low-temperature shift processes. Reactor temperature distribution and its overall thermal efficiency depend on various inlet conditions such as the equivalence ratio, the steam to carbon ratio (SCR), and the fuel distribution ratio (FDR) into the reactor and the combustor components. These experiments attempted to analyze the reformer’s thermal and chemical properties through quantitative evaluation of product composition and heat exchange between the combustor and the reactor. FDR is critical factor in determining the overall performance as unbalanced fuel injection into the reactor and the combustor deteriorates overall thermal efficiency. Local temperature distribution also influences greatly on the fuel conversion rate and thermal efficiency. For the experiments, the operation conditions were set as SCR was in range of 2.5–4.0 and FDR was in 0.4–0.7 along with equivalence ratio of 0.9–1.1; optimum results were observed for FDR of 0.63 and SCR of 3.0 in the cylindrical steam reformer.

The thermal performance of a natural-gas based cylindrical steam reformer coupled with a combustor is investigated for the practical usage of a prototype fuel cell under development (KETEP project). In this study, thermal characteristics of internal combustor are analyzed that includes the effect of flame pattern on local heat release and heat transfer mechanism from combustor to reforming zone. Overall performances are found to depend on various inlet conditions such as fuel distribution ratio and steam carbon ratio. These experiments could guide how to manage efficiently the reformer’s fuel calorie and achieve high hydrogen production along with high thermal efficiency.

The motion of birds and insects have been studied and applied to MAV(Micro Air Vehicle) and AUV(Autonomous Underwater Vehicle). Most of AUV research is focused on shape and motion of single hydrofoil. However, double hydrofoil system is mostly used in real physics. This system shows completely different hydrodynamic characteristic to single hydrofoil because of wake interaction. The goal of this study is define the trajectory of wake interaction in double hydrofoil system. Moreover, trust and efficiency of various combined motion will be demonstrated. Symmetry airfoil is used for analysis an hydrodynamic characteristic. Forward wing`s plunging and pitching motion is fixed, hide wing`s Heaving ratio, Pitch phase shift from forward plunging and Heaving shift is changed. This study provide necessary basic data of motion optimization for double hydrofoil system.

In this study, DC (Direct current) type steam plasma igniter is developed for effective ignition of high-energy density metal aluminum and gas temperature is measu red by emission spectrum of OH radical. Because of the ultra-high gas temperature, the DC plas ma jet is measured by Boltzmann plot method which is the non-contact optical technique and spectrum comparison-analysis. And both methods were applied to experiment after accurate verification. As a result, we could identify that plasma jet temperature is 2900 K ~ 5800 K in the 30 mm range fr om the nozzle tip.초 록 본 연구에서 고에너지 금속 알루미늄의 효과적인 점화를 위해 개발한 직류 방식의 스팀 플라즈마 점화기 가스온도를 OH radical의 방출 스펙트럼을 사용하여 측정하였다. 플라즈마 제트온도는 초고온이므로 비접촉식 광학 계측 방법인 볼츠만 기울기법과 스펙트럼 비교 분석법을 이용하여 측정하였으며 각각의 방법은 정밀하게 검증 후 실험에 적용되었다. 플라즈마 점화기의 노즐 팁으로부터 30 mm 범위에서의 제트온도 측정결과 두 방법 모두 알루미늄의 점화온도(≈2400 K) 이상의 2900 K ~ 5800 K 를 확인할 수 있었다.Key Words: Steam Plasma Igniter(스팀 플라즈마 점화기), High Temperature Measurement(고온측정법), Emission Spectroscopy(방출분광법), Aluminum Ignition(알루미늄 점화)Received 2 June 2013 / Revised 3 January 2014 / Accepted 11 Jan uary 2014

SUMMARY A multi-resolution analysis (MRA) is proposed for efficient flow computation with preserving the high-order numerical accuracy of a conventional solver. In the MRA process, the smoothness of a flow pattern is assessed by the difference between original flow property values, and the values approximated by high-order interpolating polynomial in decomposition. Insignificant data in smooth region are discarded, and flux computation is performed only where crucial features of a solution exist. The reduction of expensive flow computation improves the overall computational efficiency. In order to maintain the high-order accuracy, modified thresholding procedure restricts the additional error introduced by the thresholding below the order of accuracy of a conventional solver. The practical applicability of the MRA method is validated in various continuous and discontinuous flow problems. The MRA stably computes the Euler equations for continuous and discontinuous flow problems and maintains the accuracy of a conventional solver. Overall, it substantially enhances the computational efficiency of the conventional third-order accurate solver. Copyright © 2014 John Wiley & Sons, Ltd.

The electrical sintering characteristics of inkjet-printed line patterns on a paper substrate were investigated by varying initial pattern resistance, input voltage, sintering time, and input voltage profile. The initial resistance was controlled by preheating the patterns, and its range was between 500 Ω and 5 MΩ. Depending on the input voltage and initial resistance, there exist three different regions: sintering, no change, and blowout. While no sintering is observed for too high initial resistance, blowout of printed lines occurs for a larger input voltage. For the initial resistance lower than ~ 100 kΩ and the input voltage ranging from 20 V to 40 V, all the printed lines are electrically sintered within a short time without damaging the underlying paper substrates. When using the two-step voltage profile, the final resistance of lines becomes five times smaller than the resistance with the one-step voltage profile due to the increase in the grain size and the reduction in the void area, and no burning or blowout occurs in the lines. Due to its many advantages, the electrical sintering can provide a fast, reliable and effective way to fabricate high quality inkjet-printed conductive patterns for various printed electronics applications.

We have obtained a wide range of surface wettabilities of PI substrate for inkjet printing by combining hydrophobic solution coating and O 2 or Ar plasma treatments. Experiments were conducted to investigate the variation in inkjet-printed dot diameters with different surface treatments. The change in chemical and physical characteristics of treated surfaces was evaluated using static contact angle measurements, field emission scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Only hydrophobic coated surface produces the smallest dot diameter and the largest contact angle. Dot diameter increases and contact angle decreases as the plasma treatment time increases. Since the removal of hydrophobic layer from the surface occurs due to the etching effect of O 2 and Ar plasma during the plasma treatments, F/C ratio decreases with increasing the plasma treatment time. Surface roughness variations are also observed after plasma treatments. The ranges of printed dot sizes for O 2 and Ar plasma treatments are 38 μm–70 μm and 38 μm–92 μm, respectively. Ar plasma treatment shows a wider range of surface wettability because of higher removal rate of the hydrophobic layer. This combination of hydrophobic coating and plasma treatment can offer an effective way to obtain a wide range of surface wettabilities for high quality inkjet-printed patterns.

Corresponding author. E-mail: hjmoon@kau.ac.krABSTRACT Linear stability analysis for combustion instability within a cylindrical port of solid rocket motor has been conducted. The analysis of acoustic energy has been perfor med by a commercial COMSOL code to obtain the mode function associated to each acoustic mode pr ior to the calculation of stability alpha. An instability diagnosis based on the linear stability a nalysis of Culick is performed where special interests have been focused on 5 stability factors(alph a) such as pressure coupling, nozzle damping, particle damping and additionally, flow turning effect and viscous damping to take into account the flow and viscosity effect near the fuel surface. The instability decay characteristics depending on the particle size is also analyzed.초 록 본 연구에서는 고체로켓 모터의 연소 불안정성을 예측하고 분석 할 수 있는 해석도구의 개발을 위해 음향에너지의 분석과 선형 안정성 해석을 수행하였다. 음향 해석의 경우 상용 프로그램인 COMSOL을 이용하여 단면적이 일정한 실린더 형상의 연소실 음향 해석 및 모드 해를 도출하였다. Culick에 의해 정립된 고체추진 로켓의 선형 안정성 해석에 기초하여 연소 불안정성을 진단하였으며 압력결합, 노즐감쇠, 입자감쇠의 안정성 요소(stability alpha) 외에 유동방향변환(flow turning) 요소와 점성감쇠(viscous loss) 요소를 추가하여 연료 표면 근처의 유동 및 점성효과를 포함하는 연소 불안정의 경향을 파악하였다. 또한 입자의 크기에 따른 주파수 영역별 연소 불안정 감쇠 특성을 파악하였다.Key Words: Solid Rocket(고체로켓), Acoustic(음향학), Combustion Instability(연소 불안정), Linear Stability Analysis(선형 안정성 해석), Stability Alpha(안정성 요소)Nomenclature : speed of sound

Corresponding author. E-mail: wsyoon@yonsei.ac.krABSTRACT In this study, In order to develop the measurement method of high energy density metal aluminum dust cloud combustion, flame temperature and emission spectrum was measured using spectrometer. Because of the ultra high ㎛-sized aluminum flame temperature more than 2400 K, it was meas ured by non-contact optical technique which is the modified two wavelength pyrometry with 520, 640 nm and spectrum comparison method. These methods were applied to e xperiment after accurate verification. As a result, we could identify that flame tempera ture is more than 2400 K in bottom of combustor in both methods. And on the emission spectrum analysi s, we could measure AlO radical which is occurred dominantly in aluminum combustion.초 록 본 연구에서는 고에너지 금속 알루미늄 군입자 연소 화염 분석을 위한 측정기법 개발 연구로서 스펙트로메터를 사용하여 화염 온도와 자발광 스펙트럼을 측정하였다. 마이크로 크기의 알루미늄 군입자 연소 반응시 발생하는 화염온도는 약 2400 K 이상의 초고온이므로 비접촉식 광학 계측 방법을 사용하였으며, 측정을 위해 개발된 기법은 520 nm, 640 nm를 사용하는 이색법을 응용한 방법과 광대역 파장 비교법으로서 각각의 방법은 정밀하게 검증 후 실험에 적용되었다. 연소실 하단에서 화염온도 측정결과 두 방법 모두 2400 K 이상의 화염온도를 확인할 수 있었으며 자발광 측정 결과 알루미늄 연소 반응시 가장 지배적으로 발생하는 화학종인 AlO를 확인할 수 있었다.Key Words: High Temperature Measurement(고온측정법), Emission Spectroscopy(방출분광법)Received 14 June 2013 / Revised 11 September 2013 / Accepted 18 September 2013

This paper presents performance evaluation of natural gas based steam reformer with special attention on the operating conditions of internal combustor. In steam reformer in which strong endothermic process is involved, appropriate control of heat source is highly important that enables the efficient hydrogen production. In this study, experimental measuring device was setup to evaluate the performance of steam reformer for 5 kW PEMFC. The objective of the study is to investigate the dependence of the performance such as hydrogen reforming efficiency on the operation conditions such as inflowing mixed gas ratio and heat transfer through main reforming reactor and auxiliary combustor. Experimental results showed that the hydrogen conversion rate can be improved through the temperature distribution control based on (1) main reactor inlet gases ratio such as steam to carbon ratio (SCR) and (2) air-fuel ratio at the auxiliary combustor. With the increment of the amount of fuel in the combustor, the overall internal temperature could increase generally, but the thermal efficiency does not always increase. The study shows that the thermal efficiency and the fuel conversion rate of steam reformer could be improved by the effective heat transfer design and optimized parameter setup such as appropriate inlet gas mixed ratios.

The design of a biomimetic micro air vehicle with flapping wings is an essential challenge in the military/civilian field to conduct various missions. The success of a micro-air-vehicle flight is strongly related to the maneuverability and sustainability of an unsteady aerodynamic performance of the flapping motion. Appropriate flapping kinematics need to be established that are amenable to various flight purposes under a fluctuating environment. In this research, kinematics of flapping motion are determined by the study of aerodynamic performance of a flapping airfoil for appropriate maneuverability and sustainability. The flapping motion of an airfoil is formulated by a combined sinusoidal plunging and pitching motion in various angles of the stroke plane. The optimization process is carried out to determine the efficient motions based on a well-defined surrogate model that is made from the results of two-dimensional computational-fluid-dynamics analysis. The kriging method and genetic algorithm are use...

This paper describes the results of study on reaction of insensitive igniter in which a pyrosensor is automatically sensing the rate of risk of fire or explosion of solid rocket motor exposed to an unexpected fire and makes the rocket motor burn itself safely. The Slow Cook Off(SCO) test following the regulation of MIL-STD-2105D was carried out with a rocket motor loaded with HTPB propellant, in which a thermal pyrosensor igniter was installed. The auto-ignition temperature measured was approximately and it corresponded to Type V(Burning) reaction in SCO test, while the temperature by Kissinger equation was calculated to be .

The study considers the high maneuverability flight and path optimization is conducted to investigate the appropriate generation of the lift and thrust considering the angle of the stroke plane. The path optimization problem is defined according to the various purposes of the high maneuverability flight. The flying purposes are to maximize thrust force, lift force and both lift and thrust forces. The flapping motion of the airfoil is made by a combined sinusoidal plunging and pitching motion in each problem. The optimization process is carried out by using well-defined surrogate models. The surrogate model is determined by the results of two-dimensional computational fluid dynamics analysis. The Kriging method is used to make the surrogate model and a genetic algorithm is utilized to optimize the surrogate model. The optimization results show the flapping motions for the high maneuverable flight. The effects on the generation of lift and thrust forces are confirmed by analyzing the vortex.

The study is to analyze the chemical and heat-flow reactions in the hydrogen generation unit(autothermal reformer), using computational numerical tools. Autothermal reformer(ATR) is involved in complex chemical reaction, mass and heat transfer due to exothermic and endothermic reactions. Therefore it is necessary to reveal the effects of various operation parameters and geometries on the ATR performance by using numerical analysis. Numerical analysis needs to dominant chemical reactions that includes Full Combustion(FC) reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction and Direct Steam Reforming(DSR) reaction. The objective of the study is to improve theoretically the reformer design capability for the goal of high hydrogen production in the autothermal reformer using methane. Hydrogen production reached maximum in a certain value of Oxygen to Carbon Ratio(OCR) or Steam to Carbon Ratio(SCR). When the longitudinal distance to dimeter ratio(L/D) is increased, hydrogen production increases.

In this study, an experiment was performed to obtain the optimum design of a passive micromixer for effective mixing by using a microsized device and rectangular obstacles; a low Reynolds number was maintained in the microchannel. The experiment was carried out by varying the number, size, and location of the rectangular obstacles. Further, the Y-channel's shape was optimized for maximizing the mixture ratio, which has limit qualification that an allowed value of pressure drop. The increase in the efficiency of mixing was observed to be greater than that in the case of circular obstacles by approximately 2.5%.

A straightforward and accurate method was developed to verify the delivery of intensity-modulated radiation therapy (IMRT) and to reconstruct the dose in a patient. The method is based on a computational algorithm that linearly describes the physical relationship between beamlets and dose-scoring voxels in a patient and the dose image from an electronic portal imaging device (EPID). The relationship is expressed in the form of dose response functions (responses) that are quantified using Monte Carlo (MC) particle transport techniques. From the dose information measured by the EPID the received patient dose is reconstructed by inversely solving the algorithm. The unique and novel non-iterative feature of this algorithm sets it apart from many existing dose reconstruction methods in the literature. This study presents the algorithm in detail and validates it experimentally for open and IMRT fields. Responses were first calculated for each beamlet of the selected fields by MC simulation. In-phantom and exit film dosimetry were performed on a flat phantom. Using the calculated responses and the algorithm, the exit film dose was used to inversely reconstruct the in-phantom dose, which was then compared with the measured in-phantom dose. The dose comparison in the phantom for all irradiated fields showed a pass rate of higher than 90% dose points given the criteria of dose difference of 3% and distance to agreement of 3 mm.

Mixing between two or more reagents is one of important processes in biochemical microfluidics. In efficient micromixer design, it is essential to analyze flow pattern and evaluate mixing efficiency with good precision. In this work, mixing efficiency for Y-channel micromixer is measured by fluorescence intensity using LIF(Laser Induced Fluorescence) Confocal Microscope. The Y-channel micromixers are fabricated with polydimethylsiloxane(PDMS) and those are bonded to glass plate through Plasma bonding. Nile Blue A is injected into the micromixer as a fluorescence dye for measuring of fluorescence intensity by He/Ne laser. For visualization of the flow pattern, dynamic image capturing is carried out using CAM scope. For the comparison with computer simulation, modified SIMPLE algorithm for incompressible flow equation is solved for the same geometry as in the experiment. Throughout the experiments and computer simulation, accurate mixing efficiency evaluation process for a PDMS Y-channel micromixer is established.

Supercompact wavelets are extended to hybrid-type applications for practical fluid dynamics data management. Beam and Warming's supercompact multiwavelet method is regarded as one proper tool for representing fluid simulation data because of its compact support. This wavelet compactness significantly reduces storage requirements as well as data processing time, and can prevent unnecessary interaction with closely located data across singularities such as shocks and vortices. For effective domain subdivision, a hybrid method that combines 3-D, 2-D, and 1-D versions of supercompact multiwavelets is developed. The hybrid 3-D type of supercompact multiwavelet shows high data compression ratio in practical fluid simulation data because the mother wavelets are highly effective and encompass subdivision methods. With the present method, efficient data management for datasets of huge size is enabled without losing important features. Several numerical tests substantiate large data compression for flow fi...

A Sparse Point Representation(SPR) based on interpolation wavelets is presented. The SPR is implemented for the purpose of CFD data compression. Unlike conventional wavelet transformation, the SPR relieves computing workload in the similar fashion of lifting scheme that includes splitting and prediction procedures in sequence. However, SPR skips update procedure that is major part of lifting scheme. Data compression can be achieved by proper thresholding method. The advantage of the SPR method is that, by keeping even point physical values, low frequency filtering procedure is omitted and its related unphysical thresholing mechanism can be avoided in reconstruction process. Extra singular feature detection algorithm is implemented for preserving singular features such as shock and vortices. Several numerical tests show the adequacy of SPR for the CFD data. It is also shown that it can be easily extended to nonlinear adaptive wavelets for enhanced feature capturing.

This paper presents a supercompact multi-wavelet scheme and its application to fluid simulation data. Beam and Warming’s Supercompact wavelet method is an appropriate wavelet for fluid simulation data in the sense that it can provide compact support and avoid unnecessary interaction with remotely located data (e.g. across a shock discontinuity or vortices). Thresholding for data compression is applied based on a covariance vector structure of multi-wavelets. The extension of this scheme to three dimensions is analyzed. The numerical tests demonstrate that it can provide not only analytic advantages but actually result in large data compression ratios.