• 제목/요약/키워드: Air Contact Control

검색결과 91건 처리시간 0.028초

압전 액추에이터를 이용한 DMFC의 공기 공급 시스템 (Air Supplying System for DMFC using Piezo Actuators)

  • 홍철호;김동진;윤효진
    • 한국산학기술학회논문지
    • /
    • 제11권5호
    • /
    • pp.1585-1591
    • /
    • 2010
  • DMFC는 산소를 반응물질로 사용하기 때문에 캐소드 전극이 외부 공기와 직접 접촉해야 한다. 그러나 휴대기기에 사용하는 경우에 사용자의 신체에 의해 공기의 흡입구가 가려져 산소공급이 되지 않는 현상이 발생할 수 있다. DMFC에 공기를 공급하기 위해 냉각팬을 사용하는데 냉각팬은 유로의 압력 손실 및 변동에 따라 출력의 변동이 심하다. 본 논문에서는 냉각팬의 문제점을 해결하기 위해 압전 액추에이터를 이용하여 공기 공급 시스템을 설계하였다. 설계된 공기 공급 시스템의 성능을 평가하기 위해 DMFC 평가 시스템을 구현하였고, 구현된 시스템을 통해 MP3 플레이어를 동작 시켰다.

코로나 바이러스 대유행에 따른 치과 의료 관리 가이드라인 (Guidelines for dental clinic infection prevention during COVID-19 pandemic)

  • 김진
    • 대한치과의료관리학회지
    • /
    • 제8권1호
    • /
    • pp.1-7
    • /
    • 2020
  • Dental settings have unique characteristics that warrant specific infection control considerations, including (1) prioritizing the most critical dental services and provide care in a way that minimizes harm to patients due to delayed care, or harm to personnel from potential exposure to persons infected with the COVID-19 disease, and (2) proactively communicate to both personnel and patients the need for them to stay at home if sick. For health care, an interim infection prevention and control recommendation (COVID-19) is recommended for patients suspected of having coronavirus or those whose status has been confirmed. SARS-CoV-2, which is the virus that causes COVID-19, is thought to be spread primarily between people who are in close contact with one another (within 6 feet) through respiratory droplets that are produced when an infected person coughs, sneezes, or talks. Airborne transmission from person-to-person over long distances is unlikely. However, COVID-19 is a new disease, and there remain uncertainties about its mode of spreads and the severity of illness it causes. The virus has been shown to persist in aerosols for several hours, and on some surfaces for days under laboratory conditions. COVID-19 may also be spread by people who are asymptomatic. The practice of dentistry involves the use of rotary dental and surgical instruments, such as handpieces or ultrasonic scalers, and air-water syringes. These instruments create a visible spray that can contain particle droplets of water, saliva, blood, microorganisms, and other debris. While KF 94 masks protect the mucous membranes of the mouth and nose from droplet spatter, they do not provide complete protection against the inhalation of airborne infectious agents. If the patient is afebrile (temperature <100.4°F)* and otherwise without symptoms consistent with COVID-19, then dental care may be provided using appropriate engineering and administrative controls, work practices, and infection control considerations. It is necessary to provide supplies for respiratory hygiene and cough etiquette, including alcohol-based hand rub (ABHR) with 60%~95% alcohol, tissues, and no-touch receptacles for disposal, at healthcare facility entrances, waiting rooms, and patient check-ins. There is also the need to install physical barriers (e.g., glass or plastic windows) in reception areas to limit close contact between triage personnel and potentially infectious patients. Ideally, dental treatment should be provided in individual rooms whenever possible, with a spacing of at least 6 feet between the patient chairs. Further, the use of easy-to-clean floor-to-ceiling barriers will enhance the effectiveness of portable HEPA air filtration systems. Before and after all patient contact, contact with potentially infectious material, and before putting on and after removing personal protective equipment, including gloves, hand hygiene after removal is particularly important to remove any pathogens that may have been transferred to the bare hands during the removal process. ABHR with 60~95% alcohol is to be used, or hands should be washed with soap and water for at least 20 s.

ATmega128 소자를 이용한 자기베어링 제어(실험을 중심으로) (Control of Magnetic Bearing using ATmega128(Focused on experiments))

  • 양주호;최교호;정광교
    • 동력기계공학회지
    • /
    • 제17권4호
    • /
    • pp.139-146
    • /
    • 2013
  • Because the magnetic bearing supports levitating body without contact, wear, noise and vibration, it is very useful to high revolution machinery. In this paper we selected ATmega 128, a less expensive and widely used micro controller, for control the magnetic bearing system. And we selected the sampling time and the control gain of PID controller through trial-and-error. The control program of the one board controller utilized lookup table to reduce calculation time, and bit shifting for the integer calculation in instead of floating point calculation. As the results, the controller carried out relatively high speed PID control on sampling time 0.25 ms. At last the rotation test for the magnetic bearing system was carried out by 3 phase induction motor and air turbine.

비접촉 동력 전달을 위한 마그네트 기어 기반 감속기의 속도 제어에 관한 연구 (Speed Control Of The Magnet Gear-Based Speed Reducer For Non-contact Power Transmission)

  • 정광석
    • 한국산학기술학회논문지
    • /
    • 제17권7호
    • /
    • pp.380-388
    • /
    • 2016
  • 마그네트 기어를 이용하면 기계적인 접촉없이 동력을 전달할 수 있다. 마그네트 기어 기반 감속 시스템에서 종동축은 구동축으로부터 분리되어있기 때문에 시스템은 제한된 공극 강성으로 부하 변화에 대응해야하는 2관성 공진 시스템이다. 종동축 즉, 저속측은 구동축 인가 토크만으로 제어되고 갑작스런 외란에 따라 일반적인 기계식 기어 시스템과 달리 과도한 진동이나 슬립이 발생할 수 있다. 따라서 저속측에 인가되는 부하 등의 외란은 실시간으로 측정되거나 추정되어야 한다. 본 논문에서는 고조파 조절기 일체형 마그네트 기어를 이용한 감속 시스템의 저속측 속도 제어를 위한 전상태 되먹임 제어기를 제안하고 이를 전산 모의 시험과 실험을 통해 검증하였다. 저속측 부하를 추정하기 위해 새로운 상태변수를 도입하여 관측기를 설계하였으며 이를 기반으로 하는 전상태 제어기를 통한 외란에 대한 강건성은 2자유도 PI 속도 제어기와 비교하였다. 상대적으로 짧은 시간안에 극의 슬립이 보정되는 것을 확인하였으며 추정된 변수는 실제 측정 결과와 유사한 경향을 나타내었다. 이러한 결과는 마그네트 기어 감속기의 서보 시스템으로의 응용 가능성을 담보해주는 결과인 것으로 판단된다.

레이저 회절 측정기를 이용한 벤츄리 캐비테이션에서의 마이크로버블 발생 특성 연구 (Study on Micro-bubble Generation Characteristics in Venturi Cavitation using Laser Diffractometer)

  • 임윤규;양해정;김영일
    • 드라이브 ㆍ 컨트롤
    • /
    • 제16권1호
    • /
    • pp.1-6
    • /
    • 2019
  • The use of micro bubbles in industrial fields has been increasing in the recent years., particularly micro-bubble sterilization and water purification effects. Various methods have been developed for the generation of micro-bubbles. Depending on the method of generating bubbles, the micro-bubbles can be roughly classified into saturation molding, cavitation and rotation flow types. The objective of this study was to use ventilated tube type as a method of generating micro-bubbles in order to purify large amount of water quality such as lakes and reservoirs. This method shows a difference in efficiency in which micro-bubbles are generated depending on the contact ratio of gas to liquid. The study also investigated the optimal gas liquid contact ratio by applying various orifice methods and investigated the optimum condition of micro-bubble generation by gas Based on this, a technology to develop a micro-bubble generator with a venturi type nozzle shape that has a high water purification effect was developed.

Air abrasive technique을 이용한 복합레진 수복 증례 (TREATMENT OF COMPOSITE RESIN RESTORATION WITH THE AIR ABRASIVE TECHNIQUE)

  • 이창우;장기택;이상훈;한세현
    • 대한소아치과학회지
    • /
    • 제24권4호
    • /
    • pp.763-770
    • /
    • 1997
  • The air abrasive technique is a non-mechanical method by which teeth are treated before restoration and stains and calculi are removed from tooth surfaces using the kinetic energy of small particles. The air abrasive technique in dentistry was first introduced in the 1950's with as instrument called 'Airdent'. But, as the main restorative materials of the period were amalgam and gold, and the instrument's inability to control the flow of particles caused the particles to be spread throughout the clinics, widespread use was not possible. In the 1990's, as these techincal problems were solved and more interest in new restorative materials rose in an effort to preserve sound tooth structure, new developements took place in instruments related to the air abrasive technique. The air abrasive technique produces less pressure, vibration and heat that might cause patient discomfort and facilitates the preservation of sound tooth structure. It also reduces the need for anesthesia and is less harmful to the pulp. Other advantages include increase in dentin bonding strength of composite resin, lower possibility of saliva contamination and maintenance of a dry field. But there is not direct contact between the nozzle and the tooth, the operator cannot use his or her tactile sense and must rely solely upon visual input. Other disadvantages are: the tooth preparation depends on the operator's ability; alpha-alumina particles, after bouncing off the tooth surface, cause damage to dental mirrors; the equipment is expensive and takes up a certain amount of space in the clinic. The author conducted case report using the air abrasive technique on patient visiting the Department of Pediatric Dentistry at Seoul National University Dental Hospital and arrived at the following conclusions. 1. The tooth preparation capability of different air abrasive devices varied widely among manufacturers. 2. It was more effective in treating early caries lesions and stains compared to lesions where caries had already progressed to produce soft dentin. 3. The cold stream and noise caused by the evacuation system was a major cause of discomfort to pediatric patients. 4. As there is no direct contact with tooth surface when using the air abrasive technique for tooth preparation, considerable experience and skill is required for proper tooth preparation.

  • PDF

수직 온도구배를 갖는 공기 흡입 덕트의 기계적 격리기법 (Mechanical Isolation Method for an Air Intake Duct with Vertical Temperature Gradient)

  • 정치훈
    • 한국추진공학회지
    • /
    • 제20권4호
    • /
    • pp.87-93
    • /
    • 2016
  • 직접 연결식(DC) 고도모의 엔진시험 수행 시, 공기 흡입 덕트와 항공용 엔진 사이에 래버린스 씰이 설치된다. 래버린스 씰은 이 둘을 기계적으로 격리시킴으로써 주추력 및 측추력을 보다 정확하게 측정할 수 있도록 돕는다. 하지만 덕트 내부 공급공기에 높은 수직 온도구배가 발생할 경우, 래버린스 씰의 격리가 파괴되어버린다. 본 논문에서는 이러한 접촉 문제를 해결하기 위한 노력의 일환으로 래버린스 씰 온도 제어장치를 제작/설치하였다. 본 장치를 실제 항공용 엔진시험에 적용한 결과, 높은 수직 온도구배가 생성되어도 래버린스 씰의 격리가 잘 유지되는 것을 확인할 수 있었다.

Transition of Rivulet Flow from Linear to Droplet Stream

  • Kim, Ho-Young;Kim, Jin-Ho;Kang, Byung-Ha;Lee, Seung-Chul;Lee, Jae-Heon
    • International Journal of Air-Conditioning and Refrigeration
    • /
    • 제10권3호
    • /
    • pp.147-152
    • /
    • 2002
  • When a liquid is supplied through a nozzle onto a relatively non-wetting inclined solid surface, a narrow rivulet forms. There exist several regimes of rivulet flow depending on various flow conditions. In this paper, the fundamental mechanism behind the transition of a linear rivulet to a droplet flow is investigated. The experiments show that the droplet flow emerges due to the necking of a liquid thread near the nozzle. Based on the observation, it is argued that when the retraction velocity of a liquid thread exceeds its axial velocity, the bifurcation of the liquid thread occurs, and this argument is experimentally verified.

IoT 센서를 이용한 공기 자동조절 스마트 에어카시트 제어 시스템 개발 (Development of Smart Air Car Seat Control System for Automatic Air Conditioning using IoT Sensor)

  • 김대훈;정수은;박수현
    • 한국정보통신학회:학술대회논문집
    • /
    • 한국정보통신학회 2021년도 추계학술대회
    • /
    • pp.208-210
    • /
    • 2021
  • 인터넷에 연결되는 사물의 수가 급격히 증가함에 따라 센서와 통신 기능을 포함해서 단순 모니터링 기능을 하거나, 서버로 전달하는 기능에서 벗어나 점점 인간에게 직접 가치를 제공하는 지능형 디바이스 개발 사업이 확장되고 있다. 따라서 디바이스가 주변 센싱 정보를 분석해서 주변 환경을 사용자들의 기호나 안전을 고려해서 변경하는 기술을 개발할 전망으로. 공기를 이용하여 다양한 효과를 가져올 수 있는 개발 제품에 생체신호 측정 시스템을 구축함으로써, 착좌 시 압력 분포의 변화 패턴을 통해 사용자의 상태를 파악할 수 있게 할 예정이다. 온도측정 센서와 사용자의 접촉을 통해 에어카시트 사용에 쾌적함을 높이고, 본 논문에서는 생체신호 측정 데이터에 의한 에어펌프 제어 시스템을 연계하여 구축하여 측정된 생체신호는 스마트폰 애플리케이션을 통해 보호자가 확인 및 조절을 할 수 있도록 하여 효과적으로 관리가 가능한 구축 시스템을 제안한다.

  • PDF

Effects of cementless fixation of implant prosthesis: A finite element study

  • Lee, Hyeonjong;Park, Soyeon;Kwon, Kung-Rock;Noh, Gunwoo
    • The Journal of Advanced Prosthodontics
    • /
    • 제11권6호
    • /
    • pp.341-349
    • /
    • 2019
  • PURPOSE. A novel retentive type of implant prosthesis that does not require the use of cement or screw holes has been introduced; however, there are few reports examining the biomechanical aspects of this novel implant. This study aimed to evaluate the biomechanical features of cementless fixation (CLF) implant prostheses. MATERIALS AND METHODS. The test groups of three variations of CLF implant prostheses and a control group of conventional cement-retained (CR) prosthesis were designed three-dimensionally for finite element analysis. The test groups were divided according to the abutment shape and the relining strategy on the inner surface of the implant crown as follows; resin-air hole-full (RAF), resin-air hole (RA), and resin-no air hole (RNA). The von Mises stress and principal stress were used to evaluate the stress values and distributions of the implant components. Contact open values were calculated to analyze the gap formation of the contact surfaces at the abutment-resin and abutment-implant interfaces. The micro-strain values were evaluated for the surrounding bone. RESULTS. Values reflecting the maximum stress on the abutment were as follows (in MPa): RAF, 25.6; RA, 23.4; RNA, 20.0; and CR, 15.8. The value of gap formation was measured from 0.88 to 1.19 ㎛ at the abutment-resin interface and 24.4 to 24.7 ㎛ at the abutment-implant interface. The strain distribution was similar in all cases. CONCLUSION. CLF had no disadvantages in terms of the biomechanical features compared with conventional CR implant prosthesis and could be successfully applied for implant prosthesis.