• Corrosion Science and Technology
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• 제20권2호
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• pp.45-51
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• 2021

In this work, we describe the effect of pulse anodizing duty ratio on the corrosion resistance of anodic films in magnesium AZ31B. The process involves the application of square pulse potential for a constant period with a duty ratio varying from 40, 60 and 80%. In several samples, a sealing treatment for 30 minutes was conducted after anodization in order to seal the pores available in the anodic layer. After anodizing, the surface morphology of the anodic layer was examined using a scanning electron microscope (SEM Hitachi SU3500). The corrosion characteristics of the sample were evaluated through an open circuit potential (OCP) and potentiodynamic polarization test using potentiogalvanostat. SEM observation shows that the increase of anodization duty ratio (α) results in a more uniform anodic layer, with fewer pores and cracks. The increase of duty ratio (α) decreases the OCP value from approximately -1.475 to about -1.6 Volt, and significantly improves the corrosion resistance of the anodic coating by 68%. The combination of anodization and sealing treatment produces an anodic coating with a very low corrosion rate of 4.4 mpy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권6호
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• pp.1849-1876
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• 2022

Wireless Sensor Network (WSN) is considered as an integral part of the Internet of Things (IoT) for collecting real-time data from the site having many applications in industry 4.0 and smart cities. The task of nodes is to sense the environment and send the relevant information over the internet. Though this task seems very straightforward but it is vulnerable to certain issues like energy consumption, delay, throughput, etc. To efficiently address these issues, this work develops a cross-layer model for the optimization between MAC and the Network layer of the OSI model for WSN. A high value of duty cycle for nodes is selected to control the delay and further enhances data transmission reliability. A node measurement prediction system based on the Kalman filter has been introduced, which uses the constraint based on covariance value to decide the scheduling scheme of the nodes. The concept of duty cycle for node scheduling is employed with a greedy data forwarding scheme. The proposed Duty Cycle-based Greedy Routing (DCGR) scheme aims to minimize the hop count, thereby mitigating the energy consumption rate. The proposed algorithm is tested using a real-world wastewater treatment dataset. The proposed method marks an 87.5% increase in the energy efficiency and reduction in the network latency by 61% when validated with other similar pre-existing schemes.

• 대한의용생체공학회:의공학회지
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• 제35권3호
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• pp.62-67
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• 2014

The purpose of the study was to identify the effect of laser parameters on photocoagulation to maximize safety and efficacy during varicose vein treatment. CW and pulsed modes at 1470 nm were initially compared as a function of power on bovine liver tissue. In the pulsed mode, various parameters including repetition rate, duty cycle, and irradiation time were compared to evaluate tissue response during thermal treatment. The results demonstrated that CW and pulsed modes yielded almost similar coagulation development possibly due to shorter irradiation time of 5 sec. Regardless of laser mode, both repetition rate and duty cycle presented constant coagulation rate whereas longer irradiation time facilitated coagulation process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2374-2376
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• 2005

본 연구에서 제안한 microfluidic system은 열공압 방식으로 구동되고 indium tin oxide (ITO) 및 polydimethylsiloxane(PDMS)로 제작하여 공정이 간단하고 비용이 저렴하여 일회용으로 사용이 가능하며 투명한 장점을 갖는다. 또한 마이크로 펌프는 인-채널 구조의 마이크로 밸브와 동일한 공정으로 제작하였다. 제안된 마이크로 펌프는 인-채널 구조의 마이크로 밸브와 같은 기판 위에 쉽게 집적하여 제작할 수 있다. 마이크로 펌프의 pumping rate는 인가 펄스 전압의 주파수와 duty비를 변화시켜 최적화하였다. Duty 비가 1%이고 주파수가 2 Hz일 때 최대 pumping rate를 보였으며 이때 pumping rate는 26.18nl/min이였다. 마이크로 밸브는 ITO 히터에 전력을 인가함으로서 유량의 on/off 제어가 잘 됨을 확인할 수 있었고 유체를 closing하기 위해 필요한 전력은 100mW이다.

• 한국간호교육학회지
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• 제13권2호
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• pp.169-176
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• 2007

Purpose: The purpose of this study was to verify the effect of aromatherapy hand massage on stress responses and serum Immunity of RN's before the night duty. Method: The data were collected during the period from Oct. 10 to Nov. 15, 2005 at S-Hospital in Seoul. There were forty-eight subjects, 24 for the experimental and 24 for the control group. A Pre & post test were conducted to measure pulse rate, perceived stress(level and score) and a blood sample for cortisol and IgA. In the experimental group, lavender and geranium were used. Data were analyzed by descriptive statistics, $x^2$-test and t-test with SPSS program. Result: The pulse rate was reduced but there were no significant differences between the two groups. Scores of subjective stress(VAS) decreased significantly after aromatherapy hand massage and the level of serum Cortisol was reduced significantly. The level of serum IgA was elevated significantly. Conclusion: Aromatherapy hand massage could be a useful intervention to reduce stress and elevate the immunity of nurses during the night duty.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 춘계종합학술대회
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• pp.254-260
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• 1999

유성버스트 통신방식은 1000 km 이상의 장거리 VHF NLOS 데이터 통신 시스템을 가장 경제적인 방법으로 구현 시켜줄 수가 있다. 그러나 이 방식은 도통율이 열화 함으로 본질적으로 실용에는 부적합한 것으로 알려져 있다. 송, 수신안테나의 빔 패턴이 공간의 hot-spot을 완전히 포용할 수 있도록 함으로서 버스트의 발생빈도를 증가시키는 동시에 안테나에 유도하는 지상 잡음 전계를 효과적으로 차단함으로서 수신기의 실효 차단전압을 낮추어 시스템의 도통율(duty rate)을 개선 할수 있다. 소개구형 공동형 안테나를 개발하였다. 이 안테나는 지하에 매설하여 사용하는데 이렇게 함으로서 수직방향의 지향성이 개선되고 지상으로부터의 잡음 혼입이 효과적으로 차단된다. 이 안테나는 3dB 빔 폭이 90$^{\circ}$ 에 달하여 앙각 8-90$^{\circ}$ 로서 근거리의 hot-spot를 효과적으로 조사(illuminate) 할 수가 있다. 지표방향으로의 지향성은 최소로 억제되어 이 방향으로부터 인공잡음의 혼입을 효과적으로 차단하는데 재래식의 Yagi 보다 평균 3 dB 이상 억제된다. 이 안테나를 수신안테나로 사용하여 100 km 경로에서 시험통신을 실시한 결과 동일한 조건하에서 4 소자 Yagi 안테나를 사용한 경우에 비하여 버스트의 발생빈도와 지속시간이 각각 10%와 20% 이상 증가한 것을 확인할 수 있었다.

• Journal of Electrical Engineering and Technology
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• 제1권1호
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• pp.110-113
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• 2006

A high rate deposition sputtering process of magnesium oxide thin film in oxide mode has been developed using a 20 kW unipolar pulsed power supply. The power supply was operated at a maximum constant voltage of 500 V and a constant current of 40 A. The pulse repetition rate and the duty were changed in the ranges of $10\sim50$ kHz and $10\sim60%$, respectively. The deposition rate increased with rising incident power to the target. Maximum incident power to the magnesium target was obtained by the control of frequency, duty and current. The deposition rate of a moving state was 9 nm m/min at the average power of 1.5 kW. This result shows higher deposition rate than any other previous work involving reactive sputtering in oxide mode. The thickness uniformities over the entire substrate area of $982mm{\times}563mm$ were observed at the processing pressure of $2.8\sim9.5$ mTorr. The thickness distribution was improved at lower pressure. This technique is proposed for application to a high through-put sputtering system for plasma display panels.

• 한국정밀공학회지
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• 제14권9호
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• pp.80-89
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• 1997

Die sinking electrical discharge machining(EDM) was conducted for ceramic composite of 33 weight percent TiC based on AI$_{2}$O$_{3}$ ceramic matrix according to the change of current and duty factor(DF). Material removal rate(MRR) was increased as the current and the duty factor increased, but better surface mor-pholoty was obtained in the region of lower current and duty factor. From the scanning electron microscopy(SEM) photographs and the energy dispersive X-ray spectroscopy(EDX) of the EDMed surface, EDM trace formed by one discharge spark was analyzed. Although the bending strength after EDM was highly decreased, reliability obtained by weibull analysis was increased twice. The bending strength was recovered or more by barrel polishing after EDM. From the FEM analysis of temperature for one spark, the possible melting region of AI$_{2}$O$_{3}$and TiC was obtained.

• 한국대기환경학회지
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• 제16권3호
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• pp.285-291
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• 2000

EGR(Exhaust Gas Recirculation) is known as the technique reducing the NOx emissions from diesel engine. Low pressure roote and high pressure roote are applied for heavy-duty diesel engine are. In this study, as research for the heavy duty diesel engine equipped with EGR, reduction characteristic of CO, THC, NOx, and PM in HD diesel engines are investigated by applying EGR device. Also, through the experiments using 11 liters, turbocharged diesel engine with EGR valve and intercooler, exhaust gas reduction characteristics were measured as changing in EGR rate according to D-13 mode.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.593-594
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• 2015

In wireless sensor networks (WSNs), due to the very low data rate, the sleeping schedule is usually used to save consumed energy and prolong the lifetime of nodes. However, duty-cycled approach can cause a high end-to-end (E2E) delay. In this paper, we study a node scheduling algorithm in WSNs such that E2E delay meets bounded delay with a given probability. We have applied the probability theory to spot the relationship between E2E delay and node interval. Simulation result illustrates that we can create the network to achieve given delay with prior probability and high energy use efficient as well.