We investigated the microstructure of an FeCrMnNiCo alloy fabricated by spark plasma sintering under different sintering temperatures (1000–1100°C) and times (1–600 s). All sintered alloys consisted of a single face-centered cubic phase. As the sintering time or temperature increased, the grains of the sintered alloys became partially coarse. The formation of Cr7C3 carbide occurred on the surface of the sintered alloys due to carbon diffusion from the graphite crucible. The depth of the layer containing Cr7C3 carbides increased to ~110 μm under severe sintering conditions (1100°C, 60 s). A molten zone was observed on the surface of the alloys sintered at higher temperatures (>1060°C) due to severe carbon diffusion that reduced the melting point of the alloy. The porosity of the sintered alloys decreased with increasing time at 1000°C, but increased at higher temperatures above 1060°C due to melting-induced porosity formation.

작은뿌리파리는 시설하우스에 발생하여 심각한 경제적 피해를 주고 있는 중요한 해충이다. 때문에 이를 방제하기 위한 다양한 연구 진행을 위해서는 간단하고 효과적인 대량 사육 방법이 요구된다. 본 연구는 시중에서 저렴하게 구입 가능한 기주인 강낭콩을 이용하여 작은뿌리파리의 대 량 사육 방법을 개발하고자 수행하였다. 시험은 강낭콩의 불린 기간 및 개수에 대한 작은뿌리파리의 산란수를 조사하였으며, 그 결과 3일 불린 강낭 콩에서 산란수가 108.2개로 가장 많았고, 강낭콩의 개수가 많을수록 산란수가 증가하였다. 또한 작은뿌리파리의 산란수가 가장 높게 나타난 3일 불 린 강낭콩배지와 기존에 사육배지로 보고된 감자디스크배지에서 산란수, 부화율, 용화율, 우화율, 생존수 및 알에서 성충까지 발육 기간을 비교하였 으며, 강낭콩배지에서 감자디스크배지보다 산란수가 8.5배 이상 높았고 용화율, 우화율, 생존수도 높게 나타났다. 알에서 성충까지 발육 기간은 강 낭콩배지에서 11.7일로 감자디스크배지보다 7일정도 빨리 우화하였다.

본 연구는 한국의 인구구조 변화가 주택가격에 미치는 영향을 분석하 기 위해, 7개 시(1개 특별시 및 6개 광역시)와 9개 도의 패널데이터를 기초로, 인구자연구조, 인구공간구조, 인구사회경제구조의 세 가지 인구 구조 변화요인별로 주택가격 변동에 미치는 영향을 실증적으로 분석하였 다. 첫째, 인구자연구조의 경우, 고령화로 인한 생산가능인구의 감소와 소년 및 노년 인구 비율의 증가가 주택가격에 미치는 영향을 분석하였 다. 둘째, 인구공간구조는 도시화율과 인구 이동이 주택가격에 미치는 영 향을 살펴보았으며, 셋째, 인구사회경제구조는 소득수준, 노동시장 조건 등이 주택시장에 미치는 영향을 분석하였다. 본 연구의 결과는 다음과 같다. 첫째, 인구자연구조에서는 고령화가 진행됨에 따라 생산가능인구의 감소가 주택가격에 부정적인 영향을 미치는 반면, 노년 인구 비율 증가 는 긍정적인 영향을 미친다는 것을 확인하였다. 둘째, 인구공간구조에서 는 도시화율의 증가가 주택가격을 상승시키는 반면, 인구 유출이나 유입 은 각기 다른 영향을 미친다는 결과를 도출하였다. 셋째, 인구사회경제구 조에서는 소득수준의 증가가 주택가격에 긍정적인 영향을 미치지만, 실 업률 상승은 부정적인 영향을 미친다는 것을 발견하였다. 이러한 분석 결과는 한국의 지역별 주택가격 차이를 설명하고, 미래 주택시장 정책 결정에 중요한 교훈을 제공할 수 있으며, 향후 인구 구조 변화가 주택 시장에 미치는 영향을 예측하는 데 기여할 수 있을 것이다.

Reducing underwater radiated noise from a ship is a critical issue for ensuring the survivability of the vessel. As high-speed signal processing and interlocking algorithms become more sophisticated, the heat intensity of shipboard equipment is increasing per unit volume. When designing shipboard equipment, it is necessary to consider the trade-off between heat dissipation and noise reduction. Following an analysis of the trade-offs, it was determined that the arrangement of Fan Ass'y A and B exhibited excellent noise and heat dissipation characteristics. Based on this, PWM control operating zones were derived. It was determined that the placement of Fan Ass'y A and B in the operating zone would increase the PWM duty cycle from 33% to 58% using a signal frequency of 25kHz band with guaranteed reliability. This would increase the noise by approximately 9dB(A) but reduce the internal board reference temperature by up to 15℃.

The effects of annealing on the microstructure and mechanical properties of Al–Zn–Mg–Cu–Si alloys fabricated by high-energy ball milling (HEBM) and spark plasma sintering (SPS) were investigated. The HEBM-free sintered alloy primarily contained Mg2Si, Q-AlCuMgSi, and Si phases. Meanwhile, the HEBM-sintered alloy contains Mg-free Si and θ-Al2Cu phases due to the formation of MgO, which causes Mg depletion in the Al matrix. Annealing without and with HEBM at 500oC causes partial dissolution and coarsening of the Q-AlCuMgSi and Mg2Si phases in the alloy and dissolution of the θ-Al2Cu phase in the alloy, respectively. In both alloys, a thermally stable α-AlFeSi phase was formed after long-term heat treatment. The grain size of the sintered alloys with and without HEBM increased from 0.5 to 1.0 μm and from 2.9 to 6.3 μm, respectively. The hardness of the sintered alloy increases after annealing for 1 h but decreases significantly after 24 h of annealing. Extending the annealing time to 168 h improved the hardness of the alloy without HEBM but had little effect on the alloy with HEBM. The relationship between the microstructural factors and the hardness of the sintered and annealed alloys is discussed.

PURPOSES : Demonstrated performance degradation of LiDAR for vehicle and pedestrian dummy in rainy and foggy road conditions. METHODS : In real-scale rain and fog road conditions, adjust the distance between LiDAR and the measurement target from 10m to 70m (in 10m interval), measure LiDAR NPC (number of point cloud) and intensity, and compare the resulting numerical values. RESULTS : LiDAR's NPC and Intensity showed statistically significant differences by overall weather condition (normal, rain, fog), and the values were found to be larger in the order of normal>rainfall>fog. In the case of vehicles, sunder rain conditions, NPC and intensity are recognized even at 70m as in normal conditions, but under fog conditions, NPC and intensity are measured only up to 30m. In the case of pedestrians, the reflective area size is smaller than that of vehicles, so they are recognized only up to 30m in rainy conditions, and NPC and intensity are measured only up to 20m in fog conditions. CONCLUSIONS : It was confirmed that LiDAR performance deteriorates in rain and fog compared to normal.

본 논문은 동아시아불교문화권에서 중요하게 여기고 있는 경전인 『법화경』 의 여성관에 대하여 알아본 논문이다. 『법화경』은 다양한 비유와 상징, 쉬운 표 현으로 대중적으로 널리 퍼져 신앙과 사상적으로 널리 알려진 경전이다. 본 논문에서는 『법화경』의 여성관을 알아보기 위하여 먼저 불교의 여성관을 부정적인 측면과 긍정적인 측면으로 나누어 살펴보았다. 경전에서 여성을 부정 적으로 보는 것은 비구니 팔경계, 여인오장설, 여인불성불설 등이 나타나는 부 분이다. 하지만 여성의 긍정적인 사회적 역할, 깨달음에는 성별의 차이가 없다 는 점, 여성의 몸에 보살의 지혜와 자비가 갖추어져 있다는 점, 여성이 설법하 는 점에서 긍정적으로 여성을 바라보고 있음을 알 수 있다. 여성관에 대한 이러 한 차이는 당시 인도의 사회상황과 연관되어 있으며, 수행자로서 여성을 인정 하고 깨달음을 얻을 수 있다고 한 점은 당시의 여성의 지위를 높인 것이라고 할 수 있다. 『법화경』에서는 여성에 대한 부정적인 인식도 있지만, 부처가 될 수 있는 수기를 받는다는 점에서 성불의 가능성을 볼 수 있다는 점에서 긍정적인 측면 도 보이고 있다. 경전에서는 여성의 성불에 대하여 용녀의 변성성불을 이야기 하고 있는데, 이는 종교적으로 힌두교와의 대립을 피하기 위한 것으로 생각된 다. 또한 경전에서 붓다가 이야기하는 본래 의미를 파악한다면 ‘여성의 변성성 불’이라는 글자에 얽매이지 않고 본래의 불성을 수행을 통해 드러내야 한다는 적극적인 수행방법론으로 이해해야 할 것이다. 불교에서는 일체중생의 본성은 본래 평등한 것으로서 차별이 없다고 한다. 즉, 여성도 깨달음을 얻을 수 있다는 것으로서 당시의 남성우월주의에서 벗어 나고자 한 것이다. 『법화경』의 여성관은 힌두교와의 종교적 다툼에서 벗어나기 위하여 여성성을 부정하지만 반대로 불교수행을 통한 여성의 성불가능성을 열 어주었다.

PURPOSES : LED based Variable Message Signs(VMS) have been widely used to inform safety messages to the drivers in advance. Legibility Distance of VMS is the most important factor to provide the safety messages to drivers in timely and effective way. However, current National Standards on legibility distance design considers letter size only even there is a difficulty to read the signs at adverse weather conditions such as heavy fog. So, this study examined the legibility issue under fog by evaluating the legibility distance with two design factors such as letter size and luminance. METHODS : Two foggy weather conditions, intermediate and heavy fog, were simulated at real-road-scale Proving Ground. Legibility distance at daytime and nighttime was evaluated by test subjects. Subjects were asked to fill the legible distance on the test sheet and statistical significant was analysed at the lab. RESULTS : The legibility distance(LD) under fog was observed only 22 to 41% of LD observed under normal weather condition at daytime, and 26 to 45% at nighttime condition. Study results showed a consistent increase in LD with higher luminance even at same letter size and vice versa conditions, However, statically significant difference between groups was only revealed when both letter size and luminance level increased conditions. In order to apply the test results in terms of engineering benefits, LD results from significantly different groups was evaluated with relative to Stopping Sight Distance(SSD) within conceptual frame suggested in this study. CONCLUSIONS : From the study results, current National Standard on legibility distance design needs to consider letter size and luminance simultaneously to response the legibility issue in adverse weather conditions.

In this study, machine learning models are proposed to predict the Vickers hardness of AlSi10Mg alloys fabricated by laser powder bed fusion (LPBF). A total of 113 utilizable datasets were collected from the literature. The hyperparameters of the machine-learning models were adjusted to select an accurate predictive model. The random forest regression (RFR) model showed the best performance compared to support vector regression, artificial neural networks, and k-nearest neighbors. The variable importance and prediction mechanisms of the RFR were discussed by Shapley additive explanation (SHAP). Aging time had the greatest influence on the Vickers hardness, followed by solution time, solution temperature, layer thickness, scan speed, power, aging temperature, average particle size, and hatching distance. Detailed prediction mechanisms for RFR are analyzed using SHAP dependence plots.

This study assessed the measurement technique of odorous substances using a GC/MOS system with MOS sensor at the detector and the method detection limits were determined for odorous substances such as hydrogen sulfide, acetaldehyde, toluene, m,pxylene, and o-xylene. The portable GC/MOS system was able to separate and measure about 16 out of 22 odorous substances including sulfur compounds, aldehydes, and VOCs. The peak values for hydrogen sulfide, acetaldehyde, toluene, m,p-xylene, and o-xylene showed a nonlinear relationship with concentration and a correlation coefficient of 0.95 or higher was confirmed. The method detection limits for hydrogen sulfide, acetaldehyde, toluene, m.pxylene, and o-xylene using the portable GC/MOS system were determined to be 0.005, 0.023, 0.016, 0.004, and 0.051 ppm, respectively. It is expected that the system can measure odor samples with concentrations of least 50 ppb without additional pretreatment or concentration processes.

We investigate the austenite stability in nanocrystalline Fe-7%Mn-X%Mo (X = 0, 1, and 2) alloys fabricated by spark plasma sintering. Mo is known as a ferrite stabilizing element, whereas Mn is an austenite stabilizing element, and many studies have focused on the effect of Mn addition on austenite stability. Herein, the volume fraction of austenite in nanocrystalline Fe-7%Mn alloys with different Mo contents is measured using X-ray diffraction. Using a disk compressive test, austenite in Fe–Mn–Mo alloys is confirmed to transform into strain-induced martensite during plastic deformation by a disk d. The variation in austenite stability in response to the addition of Mo is quantitatively evaluated by comparing the k-parameters of the kinetic equation for the strain-induced martensite transformation.

Changes in the mechanical properties and microstructure of an IN 939 W alloy according to the sintering heating rate were evaluated. IN 939 W alloy samples were fabricated by spark plasma sintering. The phase fraction, number density, and mean radius of the IN 939W alloy were calculated using a thermodynamic calculation. A universal testing machine and micro-Vickers hardness tester were employed to confirm the mechanical properties of the IN 939W alloy. X-ray diffraction, optical microscopy, field-emission scanning electron microscopy, Cs-corrected-field emission transmission electron microscopy, and energy dispersive X-ray spectrometry were used to evaluate the microstructure of the alloy. The rapid sintering heating rate resulted in a slightly dispersed γ' phase and chromium oxide. It also suppressed the precipitation of the η phase. These helped to reinforce the mechanical properties.

A typical trade-off relationship exists between strength and elongation in face-centered cubic metals. Studies have recently been conducted to enhance strength without ductility reduction through surface-treatment-based ultrasonic nanocrystalline surface modification (UNSM), which creates a gradient microstructure in which grains become smaller from the inside to the surface. The transformation-induced plasticity effect in Fe-Mn alloys results in excellent strength and ductility due to their high work-hardening rate. This rate is achieved through strain-induced martensitic transformation when an alloy is plastically deformed. In this study, Fe-6%Mn powders with different sizes were prepared by high-energy ball milling and sintered through spark plasma sintering to produce Fe-6%Mn samples. A gradient microstructure was obtained by stacking the different-sized powders to achieve similar effects as those derived from UNSM. A compressive test was performed to investigate the mechanical properties, including the yielding behavior. The deformed microstructure was observed through electron backscatter diffraction to determine the effects of gradient plastic deformation.

Novel Ni- and Fe-based alloys are developed to impart improved mechanical properties and corrosion resistance. The designed alloys are manufactured as a powder and deposited on a steel substrate using a high-velocity oxygen-fuel process. The coating layer demonstrates good corrosion resistance, and the thus-formed passive film is beneficial because of the Cr contained in the alloy system. Furthermore, during low-temperature heat treatment, factors that deteriorate the properties and which may arise during high-temperature heat treatment, are avoided. For the heattreated coating layers, the hardness increases by up to 32% and the corrosion resistance improves. The influence of the heat treatment is investigated through various methods and is considered to enhance the mechanical properties and corrosion resistance of the coating layer.

An alternative fabrication method for carburizing steel using spark plasma sintering (SPS) is investigated. The sintered carburized sample, which exhibits surface modification effects such as carburizing, sintered Fe, and sintered Fe–0.8 wt.%C alloys, is fabricated using SPS. X-ray diffraction and micro Vickers tests are employed to confirm the phase and properties. Finite element analysis is performed to evaluate the change in hardness and analyze the carbon content and residual stress of the carburized sample. The change in the hardness of the carburized sample has the same tendency to predict hardness. The difference in hardness between the carburized sample and the predicted value is also discussed. The carburized sample exhibits a compressive residual stress at the surface. These results indicate that the carburized sample experiences a surface modification effect without carburization. Field emission scanning electron microscopy is employed to verify the change in phase. A novel fabrication method for altering the carburization is successfully proposed. We expect this fabrication method to solve the problems associated with carburization.