• 한국광학회지
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• 제17권5호
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• pp.437-446
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• 2006

본 연구에서는 레이저유도 에칭기술을 이용한 스테인레스강의 고세장비 미세채널 제조에 대하여 기술한다. 공정 변수 최적화와 반복에칭을 통하여 높은 세장비를 갖는 미세채널을 제조하였으며 제조된 미세채널은 레이저출력과 에칭용액의 농도를 적절하게 조절함으로써 U 형상과 V 형상 사이의 단면 구조를 가지며 열변형이 없는 우수한 표면 형상을 보였다. 채널과 채널 사이의 간격은 $150{\mu}m$ 또는 그 이하이며 $15{\sim}50{\mu}m$ 범위의 폭을 갖는 10 이상의 고세장비 미세채널이 제조되었다. 레이저출력, 레이저초점의 이송속도, 에칭용액의 농도 등의 공정 변수들이 제조된 채널의 폭, 깊이 그리고 단면 형상에 미치는 영향에 대하여 자세히 보고한다.

• 대한의용생체공학회:의공학회지
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• 제37권5호
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• pp.178-185
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• 2016

Tear is a promising biological fluid for non-invasive health monitoring. It has been studied in the past to be a possible candidate for the diagnosis of certain systemic diseases, such as breast cancer, multiple sclerosis, prostate cancer, and diabetes. However, currently existing methods for collecting and extracting tear from the human eye causes inconsistencies in the biomolecule concentrations of the tear sample due to the irritating nature of the process. In response, we designed and fabricated a microfluidic system embedded soft contact-lens for the purpose of tear sampling. The lens was then tested with artificial tear for its tear sampling capability, and found to be able to find concentration equilibrium within 50 minutes. Additionally, simulation was carried out to further optimize the design so that tear sampling rate matched the natural tear turn-over rate of 1 microliter per minute.

• 대한기계학회논문집B
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• 제31권3호
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• pp.248-255
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• 2007

Thermal bubble formation is a fundamental process in nucleate boiling heat transfer and many microelectromechanical thermal systems. One of the established facts is that heterogeneous nucleation is originated from vapors trapped inside cavities. Based on this, we performed an experimental study on the formation of thermal bubbles from microcavity fabricated by microfabrication technology on a copper plate. The cavity was filled with aluminum particles to enhance thermal bubble formation. We observed the thermal bubble behaviors, such as bubble incipience, diameter, frequency and coalescence during nucleate boiling. The experimental data showed that the superheat required to trigger the bubble formation was significantly reduced when the cavity was filled with microparticles. We found that the initial increase of superheat led to the increase of both the departure diameter and frequency while the further increase of superheat caused multiple bubbles to coalesce resulting in the decrease of departure frequency.

• 한국표면공학회지
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• 제51권6호
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• pp.387-392
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• 2018

Nanopatterning is one of the essential nanotechnologies to fabricate electronic and energy nanodevices. Therefore, many research group members made a lot of efforts to develop simple and useful nanopatterning methods to obtain highly ordered nanostructures with functionality. In this study, in order to achieve pattern formation of three-dimensional (3D) hierarchical nanostructures, we introduce a simple and useful patterning method (nano-transfer printing (n-TP) process) consisting of various linewidths for diverse materials. Pt and $WO_3$ hybrid line structures were successfully stacked on a flexible polyimide substrate as a multi-layered hybrid 3D pattern of Pt/WO3/Pt with line-widths of $1{\mu}m$, $1{\mu}m$ and 250 nm, respectively. This simple approach suggests how to fabricate multiscale hybrid nanostructures composed of multiple materials. In addition, functional hybrid nanostructures can be expected to be applicable to various next-generation electronic devices, such as nonvolatile memories and energy harvesters.

• International Journal of Contents
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• 제17권4호
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• pp.62-78
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• 2021

This ethnographic multiple case study, based on Zappa-Hollman and Duff's construct of individual networks of practice (INoPs), explored English as a second language (L2) competence development and socialization process of a group of English-major undergraduates through their social connections and interactions at a public university located in an underdeveloped city in Northwest China. The study lasted for one academic semester and three students were selected as primary participants. Semi-structured interviews, student observations in English-related micro-settings, and associated texts were used to collect data. These data were coded to identify the thematic categories, and then data triangulation and member checking were conducted to select the most representative evidence to provide an in-depth description of students' perspective about mediating their English L2 socialization by their INoPs. Findings showed that factors in the formation of students' INoPs, including intensity, density, and nature, played significant roles in their academic or affective returns from their English learning, both of which had a substantial influence on the students' English L2 socialization. Considering that the macro-setting was a non-English, underdeveloped monolingual society, both educational institutions and individual students need to seek and create more English-mediated interactional opportunities to develop their English proficiency and adapt to local English learning communities.

• Tribology and Lubricants
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• 제38권4호
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• pp.121-127
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• 2022

This study presents the development of an integrated oil purification system consisting of moisture removal, oil flushing, and oil filtering devices. In this system, the oil flushing device is combined with a micro-bubble generator. Oil purification is necessary for ensuring the high performance of the lubricant through the efficient removal of contaminants and thus enables good maintenance of mechanical systems. The developed purification system removes moisture, varnish, and solid particles. Moreover, during oil purification, the oil flushing device separates foreign materials and contaminants remaining in the lubricating oil piping or mechanical systems. The microbubble generator, which is combined with the oil flushing device, can separate harmful contaminants, such as sludge, wear particles, and rust, from piping or lubrication systems through the cavitation effect. Moisture is removed using a double high-vacuum chamber, while sludge and varnish are removed via electro-absorption using a high-voltage generator. Additionally, the total maintenance cost of the system is reduced through the use of domestically fabricated cartridge filters composed of glass fiber and cellulose. The heater, which maintains the temperature of the lubricant at 60℃, can process 41,000 L of lubricant simultaneously. Multiple tests confirmed that the proposed integrated purification system exhibits good performance in oil flushing and removal of water and varnish.

• Smart Structures and Systems
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• 제30권2호
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• pp.183-193
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• 2022

Structural health monitoring and structural vibration control are multidisciplinary and frontier research directions of civil engineering. As intelligent materials that integrate sensing and actuation capabilities, shape memory alloys (SMAs) exhibit multiple excellent characteristics, such as shape memory effect, superelasticity, corrosion resistance, fatigue resistance, and high energy density. Moreover, SMAs possess excellent resistance sensing properties and large deformation ability. Superfine NiTi SMA wires have potential applications in structural health monitoring and micro-drive system. In this study, the mechanical properties and electrical resistance sensing characteristics of superfine NiTi SMA wires were experimentally investigated. The mechanical parameters such as residual strain, hysteretic energy, secant stiffness, and equivalent damping ratio were analyzed at different training strain amplitudes and numbers of loading-unloading cycles. The results demonstrate that the detwinning process shortened with increasing training amplitude, while austenitic mechanical properties were not affected. In addition, superfine SMA wires showed good strain-resistance linear correlation, and the loading rate had little effect on their mechanical properties and electrical resistance sensing characteristics. This study aims to provide an experimental basis for the application of superfine SMA wires in engineering.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권2호
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• pp.353-368
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• 2023

The four wing unmanned aerial vehicle owns the characteristics of small size, light weight, convenient operation and well stability. But it is easily disturbed by external environmental factors during flight with these disadvantages of short endurance and poor attitude solving ability. For solving these problems, a microprocessor based on STM32 chip is designed and the overall development is completed by the resources such as built-in timer and multi-function mode general-purpose input/output provided by the master micro controller unit, together with radio receiver, attitude meter, barometer, electronic speed control and other devices. The unmanned aerial vehicle can be remotely controlled and send radio waves to its corresponding receiver, control the analog level change of its corresponding channel pins. The master control chip can analyze and process the data to send multiple sets pulse signals of pulse width modulation to each electronic speed control. Then the electronic speed control will transform different pulse signals into different sizes of current value to drive the motor located in each direction of the frame to generate different rotational speed and generate lift force. To control the body of the unmanned aerial vehicle, so as to achieve the operator's requirements for attitude control, the PID controller based on Kalman filter is used to achieve quick response time and control accuracy. Test results show that the design is feasible.

• 한국콘텐츠학회논문지
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• 제16권11호
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• pp.488-498
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• 2016

많은 정보가 데이터로 저장되면서, 데이터를 분석하거나 특수 상황을 예측하기 위한 연구들이 진행되고 있다. 특히, 전력 데이터의 경우 환경적 요인에 의한 예측 연구 및 신재생 에너지를 활용하는 스마트그리드와 마이크로그리드 연구들이 진행 중이다. 본 논문에서는 전력 데이터의 예측을 위해 주변 환경에서 나타나는 데이터를 활용하고자 한다. 이때, 단순 기상 데이터가 아닌 이전 시간에 따른 여러 인자를 반영하여 데이터 예측이 올바르게 이루어지는지를 검증하고자 한다. 검증 과정에서는 유사 기온을 가지는 전력 데이터 선별 예측 결과와 전력 데이터의 길이에 따른 전력 수요 예측 결과를 비교군으로 두고, 기상 정보를 추가 활용하였을 때의 전력 수요 예측 결과를 비교 분석한다. 실험 결과를 통해 기상 정보를 이용할 경우 평균 15% 이내의 최대 오차율 감소 효과를 확인할 수 있다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권3호
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• pp.1105-1109
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• 2015

Chemoresistance is the most common cause of chemotherapy failure during breast cancer (BCA) treatment. It is generally known that the mechanisms of chemoresistance in tumors involve multiple genes and multiple signaling pathways,; if appropriate drugs are used to regulate the mechanisms at the gene level, it should be possible to effectively reverse chemoresistance in BCA cells. It has been confirmed that chemoresistance in BCA cells could be reversed by ginsenoside Rh2 (G-Rh2). Preliminary studies of our group identified some drugresistance specific miRNA. Accordingly, we proposed that G-Rh2 could mediate drug-resistance specific miRNA and corresponding target genes through the gene regulatory network; this could cut off the drug-resistance process in tumors and enhance treatment effects. G-Rh2 and breast cancer cells were used in our study. Through pharmaceutical interventions, we could explore how G-Rh2 could inhibit chemotherapy resistance in BCA, and analyze its impact on related miRNA and target genes. Finally, we will reveal the anti-resistance molecular mechanisms of G-Rh2 from a different angle in miRNA-mediated chemoresistance signals among cells.