• 한국산림과학회지
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• 제110권4호
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• pp.648-657
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• 2021

본 연구는 국가산림자원조사를 활용하여 임상별 및 주요 수종별 재적생장량을 추정하고, 연평균생장량(MAI)과 연년생장량(CAI) 등을 도출하여 벌기령을 제시하고자 수행하였다. 재적생장 추정을 위하여 Chapman-Richards 모델을 적용하였다. 도출된 임상별 재적추정식에서는 침엽수림이 가장 높은 생장을 하는 것으로 나타났다. 주요 수종별 추정식은 침엽수종(3종) 중에서는 일본잎갈나무가, 그리고 활엽수종(3종)에서는 굴참나무가 가장 높은 생장이 예측되었다. 그리고 이들 추정식은 적합도지수가 일본잎갈나무 0.32, 굴참나무가 0.21 등으로 대체적으로 낮게 나타났다. 그러나 재적 추정식의 적용 가능성을 알 수 있는 잔차도 분석에 있어서는, 일부 30년 이상의 임령에서 추정식의 추정치가 과소 추정되는 경향을 보였으나, 대부분 0을 중심으로 잔차가 고르게 분포하고 있었다. 따라서 이들 식이 우리나라 현실림의 수종들에 대한 재적을 추정할 수 있을 것으로 판단된다. 추정된 재적을 이용하여 연평균생장량을 계산한 결과, 침엽수림 중 중부지방 소나무 34년, 일본잎갈나무 35년, 리기다소나무 31년일 때 MAI가 최대시기에 도달하는 것으로 나타났다. 그리고 활엽수림에 있어서는 굴참나무 32년, 상수리나무 30년, 신갈나무 29년일 때가 최대시기임을 알 수 있었다. 또한 MAI와 CAI를 계산하여, 이들이 만나는 지점을 재적수확 최대 벌기령으로 결정하였다. 그 결과는 현재 산림청이 제시한 기준 벌기령과 큰 차이를 보이지 않아 정책자료로 활용이 가능할 것으로 판단된다.

• Transactions on Electrical and Electronic Materials
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• 제7권1호
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• pp.42-50
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• 2006

Co-Fe-Al-O nano-granular thin films with high electrical resistivity, fabricated by radio frequency magnetron sputtering under an $Ar+O_2$ atmosphere, are found to show good soft magnetic properties in the GHz frequency range. The real part value of the relative permeability is 260 at low frequencies and this value is maintained up to the GHz frequency range. A non-integrated type noise filter on a coplanar waveguide transmission line is demonstrated by using the Co-Fe-Al-O nano-granular thin film with the dimensions of $4\;mm(l){\times}4\;mm(w){\times}0.1\;{\mu}m(t)$. The insertion loss is very low being less than 0.3 dB and this low value is maintained up to 2 GHz. At a ferromagnetic resonance frequency of 3.3 GHz, the degree of noise suppression is measured to be 3 dB. This level of noise attenuation is small for real applications, but there is much room for further improvement by increasing the magnetic volume and integrating the magnetic thin film into the CPW transmission line.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1385-1397
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• 2024

Bentonite is a recommended material for the multiple barriers in the final disposal of low-level radioactive waste (LLW) to prevent groundwater intrusion and nuclear species migration. However, after drying-wetting cycling during the repository construction stage and ion exchange with the concrete barrier in the long-term repository, the bentonite mechanical behaviors, including swelling capacity and hydraulic conductivity, would be further influenced by the groundwater intrusion, resulting in radioactive leakage. To comprehensively examine the factors on the mechanical characteristics of bentonite, this study presented scenarios involving MX-80 and KV-1 bentonites subjected to drying-wetting cycling and accelerated ion migration. The experiments subsequently measured free swelling, swelling pressure, and hydraulic conductivity of bentonites with intrusions of seawater, high pH, and low pH solutions. The results indicated that the solutions caused a reduction in swelling volume and pressure, and an increase in hydraulic conductivity. Specifically, the swelling capability of bentonite with drying-wetting cycling in the seawater decreased significantly by 60%, while hydraulic conductivity increased by more than three times. Therefore, the study suggested minimizing drying-wetting cycling and preventing seawater intrusion, ensuring a long service life of the multiple barriers in the LLW repository.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.149-152
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• 2009

직접분사방식 추력기 노즐오리피스로부터 분사되는 분무입자의 발달특성을 연구하기 위해 분무의 다양한 위치에서 평균속도, 직경, 그리고 부피유속과 같은 분무특성인자들을 측정한다. 실험 결과로부터, 고속의 큰 직경을 갖는 분무 입자들이 주변 공기로의 운동량 손실로 인해 하류로 이동함에 따라 저속의 작은 입자로 분열한다. 또, 분무 확산 및 분산에 의해 높은 부피유속의 영역이 반경방향으로 넓게 확장된다.

• 한국레이저가공학회지
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• 제16권2호
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• pp.1-6
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• 2013

Picosecond lasers are a very effective tool for micromachining metals, especially when high accuracy, high surface roughness and no heat affected zone are required. However, low productivity has been a limit to broadening the spectrum of their industrial applications. Recently it was reported that in the micromachining of copper with a 1064nm picosecond laser, there exist the optimal pulse energy and repetition rate to achieve the maximum volume ablation rate. In this paper, we used a 515nm picosecond laser, which is more efficient for micromachining copper in terms of laser energy absorption, to obtain its optimal pulse energy and repetition rate. Theoretical analysis based on the experimental data on copper ablation showed that using a 515nm picosecond laser instead of a 1064nm picosecond laser is more favorable in that the calculated threshold fluence is 75% lower and optical penetration depth is 50% deeper.

• 전기화학회지
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• 제25권1호
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• pp.13-21
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• 2022

There is an increasing interest in monitoring of specific biomarker for determining progression of a disease or efficacy of a treatment. Conventional method for quantification of specific biomarkers as enzyme linked immunosorbent assay (ELISA) has high material costs, long incubation periods, requires large volume of samples and involves special instruments, which necessitates clinical samples to be sent to a lab. This paper reports on the development of an electrochemical biosensor to measure total immunoglobulin E (IgE), a marker of asthma disease that varies with age, gender, and disease in concentrations from 0.3-1000 ng/mL with consuming 20 µL volume of whole blood sample. The sensor provides rapid, accurate, easy, point-of-care measurement of IgE, also, sequential monitoring of total IgE with ovalbumin (OVA) induced mice is another application of sensor. Taken together, these results provide an alternative way for detection of biomarkers in whole blood with low volumes and long-term ex-vivo assessments for understanding the progression of a disease.

• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1965-1968
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• 2008

The effects of carbon-coated silicon/graphite (Si/Gr.) composite anode on the electrochemical properties were investigated. The nanosized silicon particle shows a good cycling performance with a reasonable value of the first reversible capacity as compared with microsized silicon particle. The carbon-coated silicon/graphite composite powders have been prepared by pyrolysis method under argon/10 wt% propylene gas flow at $700{^{\circ}C}$ for 7 h. Transmission electron microscopy (TEM) analysis indicates that the carbon layer thickness of 5 nm was coated uniformly onto the surface silicon powder. It is confirmed that the insertion of lithium ions change the crystalline silicon phase into the amorphous phase by X-ray diffraction (XRD) analysis. The carbon-coated composite silicon/graphite anode shows excellent cycling performance with a reversible value of 700 mAh/g. The superior electrochemical characteristics are attributed to the enhanced electronic conductivity and low volume change of silicon powder during cycling by carbon coating.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1436-1442
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• 2020

Nuclear infrastructure systems play an important role in national security. The functions and missions of nuclear infrastructure systems are vital to government, businesses, society and citizen's lives. It is crucial to design nuclear infrastructure for scalability, reliability and robustness. To do this, we can use machine learning, which is a state of the art technology used in various fields ranging from voice recognition, Internet of Things (IoT) device management and autonomous vehicles. In this paper, we propose to design and develop a machine learning algorithm to perform predictive maintenance of nuclear infrastructure. Support vector machine and logistic regression algorithms will be used to perform the prediction. These machine learning techniques have been used to explore and compare rare events that could occur in nuclear infrastructure. As per our literature review, support vector machines provide better performance metrics. In this paper, we have performed parameter optimization for both algorithms mentioned. Existing research has been done in conditions with a great volume of data, but this paper presents a novel approach to correlate nuclear infrastructure data samples where the density of probability is very low. This paper also identifies the respective motivations and distinguishes between benefits and drawbacks of the selected machine learning algorithms.

• International journal of advanced smart convergence
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• 제9권4호
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• pp.16-25
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• 2020

The operation of a wastewater treatment plant (WWTP) is a complex task which requires to consider several aspects: adapting to always changing influent composition and volume, ensuring treated effluents quality complies with local regulations, ensuring dissolved oxygen levels in biological reaction tanks are sufficient to avoid anoxic conditions etc. all of it while minimizing usage of chemicals and power consumption. The traditional way of managing WWTPs consists in having employees on the field measure various parameters and make decisions based on their judgment and experience which holds various concerns such as the low frequency of data, errors in measurement and difficulty to analyze historical data to propose optimal solutions. In the case of activated sludge WWTPs, parts of the treatment process can be automated and controlled in order to satisfy various control objectives. The models developed by the International Water Association (IWA) have been extensively used worldwide in order to design and assess the performance of various control strategies. In this work, we propose to review most recent WWTP automation initiatives around the world and identify most currently used control parameters and control architectures. We then suggest a framework to select WWTP model, control parameters and control scheme in order to develop and benchmark control strategies for WWTP automation.

• 대한방사선치료학회지
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• 제34권
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• pp.43-50
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• 2022

목 적: 총 두피 방사선치료 시 정상 뇌 조직을 최대한 보호할 수 있도록 접선조사를 극대화하는 치료계획 및 장비를 선정하고자 하였다. 대상 및 방법: 인체 모형에 총 두피를 구획하여 치료 부위를 설정하고, 나선형 토모테라피(Helical TomoTherapy, HT) 계획, Complete Block을 이용한 나선형 토모테라피(Helical TomoTherapy with Complete Block, HTCB) 계획 그리고 체적조절호형방사선치료(Volumetric Modulated Arc Therapy, VMAT) 계획을 수립하였다. 모든 치료계획은 처방 선량(40 Gy)의 95%가 들어가는 치료계획 용적이 체적의 95% 이상이 될 수 있도록, Dmax가 처방 선량의 110%를 넘지 않게 하였다. 치료계획은 뇌를 포함한 손상 위험 장기의 선량 비교를 실시하였으며 뇌 선량의 경우 Emami 등의 연구 결과의 정상조직 평가기준 체적을 참고하여 뇌 조직의 선량을 평가하였다. 결 과: HT, HTCB, VMAT 각각 뇌 조직 선량 D_33%는 21.68 Gy, 13.75 Gy, 20.89 Gy, D_67%는 7.06 Gy, 3.21 Gy, 7.84 Gy, D100%는 3.14 Gy, 1.75 Gy, 3.84 Gy, D_mean은 16.64 Gy, 11.78 Gy, 16.64 Gy로 HTCB plan에서 전반적으로 선량이 낮았으며, 저선량은 5 Gy를 기준으로 체적을 구하였을 때 V_5Gy는 각각 87%, 49%, 96%로 나타났다. 이외의 시신경을 제외한 나머지(뇌줄기, 해마, 양측 안구)의 최대선량은 HTCB에서 가장 낮았다. 결 론: 토모테라피에서 Complete Block을 적용하였을 때 전체 뇌 조직의 선량 감소와 더불어 뇌에 포함된 양쪽 해마 등의 손상 위험 장기의 선량을 가장 최소화해 방사선 유도 뇌 손상의 발생과 그로 인한 신경인지 기능 감소 등에 대한 부작용의 확률을 줄일 수 있는 치료계획임을 확인하였다. 향후에는 총 두피 조사 이외에도 다양한 부위에 치료되는 고리 형태의 표적(Ring Target)에 대한 추가적인 연구를 진행하여 접선 조사에 대한 이점을 확립하게 된다면 치료계획 시 접선조사 극대화를 위해 Complete Block을 사용한 토모테라피를 적용함으로써 선량적으로 유용한 결과를 얻을 수 있을 것으로 사료된다.