• 한국기계가공학회지
• /
• 제20권6호
• /
• pp.59-69
• /
• 2021

Directed energy deposition (DED) is an additive manufacturing technology involving a focused high-power laser or electron beam propagating over the substrate, resulting in melt pool formation while simultaneously supplying metal powder to the melt pool area to deposit the material. DED is performed to repair and strengthen parts in various applications, as it can be easily integrate local area cladding and cross-material deposition. In this study, we characterize stainless steel 316 L parts fabricated via DED based on various deposition conditions and geometries to widen the application of DED. The deposition characteristics are investigated by varying the laser power and powder feed rate. Multilayer deposition with a laser power of 362 W and a powder feed rate of 6.61 g/min indicate a height closest to the design value while affording high surface quality. The microhardness of the specimen increases from the top to the bottom of the deposited area. Tensile tests of specimens with two different deposition directions indicate that horizontally long specimens with respect to a substrate demonstrate a higher ultimate tensile strength and yield strength than vertically long specimens with lower elongation.

• Journal of Information Technology Applications and Management
• /
• 제19권2호
• /
• pp.149-179
• /
• 2012

This study explores the reporting tendencies of project managers when sending a status reports to their respective senior managers in information systems development project. It also examines the effect of selective reporting on report quality and systems development performance. The research model is proposed based on literature survey as well as key points from Iacovou et al. [2009] which is an extension of selective reporting in information systems project. Analysis of responses from 257 project managers in information systems industry indicates that pessimistic reporting by project managers has negative effect on both report quality (mediator variable) and systems development performance, while optimistic reporting has no significant effect on systems development performance. The CEO interest has an impact on the senior manager's power, which in turn leads to optimistic reporting by project managers. The senior manager's character has an impact on the senior manager's leadership, which in turn leads to pessimistic reporting. No direct relationship exists either between CEO interest and optimistic reporting or between senior manager's character and pessimistic reporting. In addition, trust toward the senior managers is significantly related to pessimistic reporting. Finally, report tendencies are also found to be affected by the active/passive characteristics of project managers.

• Nuclear Engineering and Technology
• /
• 제31권6호
• /
• pp.572-585
• /
• 1999

The characteristics of two-phase flow instability in a vertical boiling channel connecting with an unheated riser are investigated through the linear stability analysis model. Various two-phase flow models, including thermal non-equilibrium effects, are taken into account for establishing a physical model in the time domain. A classical approach to the frequency response method is adopted for the stability analysis by employing the D-partition method. The adequacy of the linear model is verified by evaluating experimental data at high quality conditions. It reveals that the flow-pattern-dependent drift velocity model enhances the prediction accuracy while the homogeneous equilibrium model shows the most conservative predictions. The characteristics of density wave oscillations under low-power and low-quality conditions are investigated by devising a simple model which accounts for the gravitational and frictional pressure losses along the channel. The necessary conditions for the occurrences of type-I instability and flow excursion are deduced from the one-dimensional D-partition analysis. The parametric effects of some design variables on low quality oscillations are also investigated.

• 소성∙가공
• /
• 제22권6호
• /
• pp.334-339
• /
• 2013

Direct Laser Melting is a prototyping process whereby a 3-D part is built layer wise by melting the metal powder with laser scanning. This process is strongly influenced by the shielding gas and the laser operating parameters such as laser power, scan rate, layering thickness, and rescanning. The shielding gas is especially important in affecting the microstructure and mechanical properties. In the current study, fabrication experiments were conducted in order to analyze the effect of shielding gas on the forming characteristics of direct laser melting. Cylindrical parts were produced from a Fe-Ni-Cr powder with a 200W fiber laser. Surface quality, porosity and hardness as a function of the layering thickness and shield gas were evaluated. By decreasing the layering thickness, the surface quality improved and porosity decreased. The selection of which shield gas, Ar or $N_2$, to obtain better surface quality, lower porosity, and higher hardness was examined. The formability and mechanical properties with a $N_2$ atmosphere are better than those parts formed under an Ar atmosphere.

• 동아시아식생활학회지
• /
• 제27권1호
• /
• pp.69-77
• /
• 2017

This study investigated the quality characteristics and antioxidant activities of Yanggaeng prepared with different ratios of Pleurotus eryngii powder: 0, 3, 6, and 9%. According to the results, the moisture content and pH increased with the addition of Pleurotus eryngii powder, but the Brix decreased. As the amount of Pleurotus eryngii powder increased, the lightness (L) increased, while the redness (a) and yellowness (b) decreased. The hardness of the control groups was lower than the Pleurotus eryngii powder groups. The total polyphenol content was influenced by the addition of Pleurotus eryngii powder. As the amount of Pleurotus eryngii powder increased, DPPH, reducing power, and metal chelating effect increased significantly. The results of a consumer acceptance test showed no significant differences in color between the controls and two groups (3% and 6%), and no significant differences in smell, taste, and overall acceptability between the controls and groups with 3% Pleurotus eryngii powder. Therefore, up to 3% Pleurotus eryngii powder can be incorporated into Yanggaeng to improve the quality and antioxidant potential.

• Nuclear Engineering and Technology
• /
• 제51권3호
• /
• pp.719-722
• /
• 2019

Gamma-ray images generally suffer from a lot of noise because of low photon detection in the gamma camera system. The purpose of this study is to improve the image quality in gamma-ray images using a gamma camera system with a fast nonlocal means (FNLM) noise reduction algorithm with an acceleration function. The designed FNLM algorithm is based on local region considerations, including the Euclidean distance in the gamma-ray image and use of the encoded information. To evaluate the noise characteristics, the normalized noise power spectrum (NNPS), contrast-to-noise ratio (CNR), and coefficient of variation (COV) were used. According to the NNPS result, the lowest values can be obtained using the FNLM noise reduction algorithm. In addition, when the conventional methods and the FNLM noise reduction algorithm were compared, the average CNR and COV using the proposed algorithm were approximately 2.23 and 7.95 times better than those of the noisy image, respectively. In particular, the image-processing time of the FNLM noise reduction algorithm can achieve the fastest time compared with conventional noise reduction methods. The results of the image qualities related to noise characteristics demonstrated the superiority of the proposed FNLM noise reduction algorithm in a gamma camera system.

• 드라이브 ㆍ 컨트롤
• /
• 제19권2호
• /
• pp.17-26
• /
• 2022

Recently, automatic transmissions caused a good improvement in the shift quality of a forklift. An advanced shift control algorithm, which was based on TCU firmware, was applied with embedded control technology and microcontrollers. In the clutch-to-clutch shifting, one friction element is released and the other friction element is activated. During this process, if the release and application timings are not synchronized, an overrun or tie-up occurs and ultimately leads to a shift shock. The TCU, which measures only the speed of the forklift, inevitably applies the open-loop shift control. In this situation, the speed ratio does not change during the clutch fill. The torque phase occurs until the clutch is disengaged. In this study, an offline shift logic of the learning control was proposed. It induced a synchronous shift when the learning control progressed. During this process, the reference current trajectory of the release clutch was corrected and applied to the next upshift. We considered the results of the overrun/tie-up characteristics of the upshift performed immediately before. The vehicle test proved that the deviation in shift quality, which was caused by the difference in the mechanical characteristics of the clutch, could be improved by the learning control.

• 한국식품저장유통학회지
• /
• 제31권2호
• /
• pp.245-255
• /
• 2024

The proximate composition, quality characteristics, antioxidant activity, and sensory evaluation scores of yakgwa added with mealworm powder (MP) were examined. MP contained 5.83 wt% moisture, 55.70 wt% crude protein, 35.96 wt% crude fat, 3.70 wt% crude ash, and 2.43 wt% carbohydrate and feature total polyphenol and flavonoid contents of 406.52 mg GAE/100 g and 21.18 mg NE/100 g, respectively. The DPPH and ABTS^•+ radical scavenging activities and the reducing power of MP were determined as 90.25%, 44.06%, and 1.74, respectively. Except for moisture and carbohydrate content, the proximate composition of mealworm yakgwa (MY) increased with the amount of MP increased. The pH of the dough increased with the addition of MP, whereas the expansion degree tended to decrease. Sugar content was highest at MP contents of 0 wt% and 12 wt% (FM4 group), and hardness was lowest in the FM4 group. With the increasing MP content, the L, b values and antioxidant activity increased, whereas a value decreased. The sensory evaluation scores for the overall preference, appearance, color, and taste were lowest in the FM4 group. These results suggested that MP contents of 6-9 wt% were optimal for mealworm-based yakgwa.

• 동아시아식생활학회지
• /
• 제25권4호
• /
• pp.672-680
• /
• 2015

본 연구는 항산화능이 우수한 음나무 잎을 쌀쿠키에 첨가하여 대조군과 실험군 간 항산화 활성과 품질 특성을 비교 분석하였다. 음나무 잎의 총 페놀 함량은 50.74 mg GAE/g, DPPH radical 소거활성 $IC_{50}$은 $41.09{\mu}g/mL$, 환원력은 1 mg/mL의 농도에서 흡광도 1.55로 음나무 잎의 우수한 항산화능을 확인할 수 있었다. 쌀쿠키의 경우, 음나무잎 분말의 첨가량이 증가할수록 수분함량, 퍼짐성, 팽창률, 색도 b값은 증가하는 경향을 나타내었다. 쌀쿠키의 항산화 활성 물질인 총 페놀 함량을 정량한 결과, 음나무 잎 첨가량이 증가할수록 페놀함량이 증가하는 경향을 보였으며, 쌀쿠키의 DPPH radical 소거능, 환원력 측정 결과, 음나무 잎 분말의 첨가량이 증가할수록 항산화능이 증가하는 경향을 보였다. 관능검사 결과에서는 음나무 잎 분말을 3% 첨가한 쌀쿠키가 가장 높은 점수를 받았으며, 5% 이상 첨가 시는 전반적인 기호도가 감소하는 것으로 나타났다. 이상의 결과를 종합하여 볼 때 음나무 잎 분말을 첨가한 쌀쿠키는 대조군에 비해 우수한 항산화 활성을 보였으며, 관능적으로도 우수한 것으로 평가되었다. 따라서 기능성과 기호도 측면을 모두 고려하였을 때 쌀쿠키에 3% 음나무 잎 분말 첨가는 기능성과 기호성을 갖춘 식품으로서 적합하다고 판단된다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.244-246
• /
• 2006

This paper deals with an analysis of SCR thyristor switching pattern for a power quality disturbance generator with phase jump function. The proposed generator can be applied to the performance test of custom power devices. Voltage sag, swell, outage, unbalance and phase jump after outage are provided by the generator. The phase jump operating principle of the generator is described and analysed. Especially, a proper switching of the SCR thyristors for the proposed generator is important to guarantee the system reliability. Therefore the switching patterns for the thyristors in each made were analysed.