• Tuberculosis and Respiratory Diseases
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• v.52 no.2
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• pp.156-165
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• 2002

Background: A tracheal stenosis is caused by mucosal ischemic injury related to a high cuff pressure ($P_{cuff}$) of the endotracheal tube. In contrast, aspiration of the upper airway secretion and impaired gas exchange due to cuff leakage is related to a low $P_{cuff}$. To prevent these complications, the $P_{cuff}$ should be kept appropriately because the appropriate $P_{cuff}$ appears to change according to the patient's daily respiratory mechanics. However, the constant cuff volume($V_{cuff}$) has frequently been instilled to the cuff balloon on a daily basis to maintain the optimal $P_{cuff}$ instead of monitoring the $P_{cuff}$ directly at the patients' bedside. To address the necessity of continuous $P_{cuff}$ monitoring, the change in the $P_{cuff}$ was evaluated at various $V_{cuff}$ levels on a daily basis in patients with long-term mechanical ventilation. The utility of mercury column sphygmomanometer for the continuous monitoring $P_{cuff}$ was also investigated. Method: The change in $P_{cuff}$ according to the increase in $V_{cuff}$ was observed in 17 patients with prolonged endotracheal intubation for mechanical ventilation for 2 week or more. This maneuver measured the change in $P_{cuff}$ daily during the mechanical ventilation days. In addition, the $P_{cuff}$ measured by mercury column sphygmomanometer was compared with the $P_{cuff}$ measured by an automatic cuff pressure manager. Results : There were no statistically significant changes of $P_{cuff}$ during more than 14 days of intubation for mechanical ventilation. However the $V_{cuff}$ required to maintain the appropriate $P_{cuff}$ varied from 1.9 cc to 9.6 cc. In addition, the intra-individual variation of the $P_{cuff}$ was observed from 10 $cmH_2O$ to 46 $cmH_2O$ at constant 3 cc $V_{cuff}$. The $P_{cuff}$ measured by the bedside mercury column sphygmomanometer is well coincident with that measured by the automatic cuff pressure manager. Conclusion: Continuous monitoring and management of the $P_{cuff}$ to maintain the appropriate $P_{cuff}$ level in order to prevent cuff related problems during long-term mechanical ventilation is recommended. For this purpose, mercury column sphygmomanometer may replace the specific cuff pressure monitoring equipment.

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.59-64
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• 2009

This study investigated the surface characteristics of polylactic acid (PLA) film after one atmospheric pressure plasma treatment. We used de-ionized water and diiodomethane as polar and non-polar solvents, respectively, for measuring contact angles, and subsequently calculated the surface free energy of PLA film. The contact angle and free energy of PLA surface were optimized at the treatment time of 30 sec, RF-power of 70 W, Ar gas flow rate of 6 lpm and air exposure time of 5 min. We analyzed the change of chemical functional groups on the surface of PLA film through XPS and were able to observe the change of polar functional groups such as -C=O, -CO, -COO on the surface of PLA film after one atmospheric pressure plasma treatment.

• Journal of the Korean Applied Science and Technology
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• v.40 no.1
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• pp.71-80
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• 2023

Silver paste is a valuable electrode material for electronic device applications because it is easy to handle with relatively low heat treatment. This study treated the electrode surface using an atmospheric-pressure plasma jet on the silver-paste electrode. This plasma jet was generated in an argon atmosphere using a high voltage of 5.5 to 6.5 kV with an operating frequency of 11.5 kHz. Plasma-jet may be more beneficial to the printing process by performing it at atmospheric pressure. The electrode surface becomes hydrophilic quickly and contact angle variation is observed on the electrode surface as a function of plasma treatment time, applied voltage, and gas flow rate. Also, there was no deviation in the contact angle after the plasma treatment in the large-area sample, that means a uniform result could be obtained regardless of the substrate size. The outcomes of this study are expected to be very useful in forming a stacked structure in the manufacture of large-area electronic devices and future applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.206-206
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• 2016

플라즈마(plasma)란 전자와 이온이 분리된 제 4의 물질 상태이다. 이 연구의 핵심인 플라즈마 제트(plasma jet)로 재생과 출아를 하는 히드라(Hydra)를 처리하여 플라즈마가 히드라의 출아 정도에 어떠한 영향을 미치는지에 대해 연구를 진행하였다. 히드라는 자포동물문 히드로충강 히드로충목 히드라과 히드라속에 속하며 무척추동물이다. 몸의 길이는 약 5-15mm정도이며 촉수가 6-8개가 있다. 먹이 섭취는 촉수로 먹이를 마비시켜 입을 통해 먹는다. 히드라는 못이나 늪 등의 풀잎이나 물속에 떨어진 낙엽과 썩은 나뭇가지에 붙어 산다. 특히 히드라는 영양 상태의 좋고 나쁨에 따라 무성생식을 하거나 유성생식을 한다. 또한 약 1/200의 아주 작은 단위에서도 재생을 하는 특성을 가지고 있다. 이러한 히드라에 플라즈마 처리를 함으로써 플라즈마가 히드라의 출아 특성에 어떠한 영향을 미치는지에 대해 연구를 수행하였다. 실험에서 사용한 플라즈마 소스는 대기압 플라즈마 제트(Atmospheric pressure plasma jet)이며 Ar(아르곤) 가스를 이용하여 플라즈마를 발생시켰다. 플라즈마가 발생되면 생체용액과 반응을 하면서 ROS(reactive oxygen species)와 RNS(reactive nitrogen species)가 생성되는데 이 활성 종들이 플라즈마의 주요한 특성이라고 할 수 있다. ROS와 RNS에 의해서 세포가 사멸을 하거나 활성화되기도 한다. 또한, ROS와 RNS가 생체 시스템에 영향을 주는 것은 매우 잘 알려져 있다. 이 점을 이용하여 히드라를 1분, 5분, 10분 동안 플라즈마 처리하여 히드라의 출아 특성을 관찰하였다. 관찰한 결과 1분 처리한 히드라 Group과 5분 처리한 히드라 Group이 가장 개체 수 변화가 뛰어났고 10분 처리한 히드라Group은 오히려 개체 수가 감소하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.331.1-331.1
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• 2016

내부지름이 2.0 mm 이하인 PTFE와 PE 튜브에 진공장치를 이용하여 튜브 내부의 압력을 감압하여 진공상태를 형성하였다. 진공기밀 후에 반응성 가스를 인입하여 튜브 외부에 장착된 전극을 통하여 고전압의 AC 전압을 인가하여 튜브 내부에 선택적으로 유전체 장벽 방전을 유도하였다. 본 연구에서는 유전율이 3.0 이하로 낮은 PTFE와 PE 튜브에 유전체 장벽방전이 유도될 때 나타나는 전압과 전류의 파형을 분석하여 방전의 개시와 방전의 형태를 조사하였다. 주파수 40 kHz인 AC 전원(PEII, Advanced Energy)과 Loadmatch 모듈을 이용하여 4 kV 이하의 전압을 인가하여 플라즈마 방전 유도하였다. 튜브에 인가고전압 프로브와 전류 프로브를 이용하여 오실로스코프를 I-V 분석을 실시하였고, 실험 결과 대기압 방전에서 유도되는 유전체 장벽방전의 I-V 특성과 달리 방전의 형태가 유전체장벽방전과 글로우방전이 혼합된 형태로 나타났다. 또한 유전체 장벽방전을 통해 튜브 내부에 형성되는 플라즈마에 대한 분석으로 OES 광분석을 실시하여, 방전 시간과 전압 변화에 따른 고분자 표면으로부터 방출되는 활성종에 대한 분석을 실시하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.164-167
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• 2003

In generally, Gas fill & drain valve is used in filling Gases to tank on high pressure in launcher The valve is quick coupling type and is separated by manual or remote control. In KSR-III, He gas fill & drain valve separated by remote control is used. In this paper, that are explained about the design specification, the test procedure, the autonomous test result and the flight test result.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.519-524
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• 2003

In this paper we discuss the dynamic characteristics of the in-arm type hydropneumatic suspension unit(ISU). For this, two accurate models are introduced. The first one is the Benedict-Webb-Rubin equation which is adopted for the spring behavior of a real gas. This equation is applicable for the high pressure of the nitrogen gas which acts as a spring in ISU system. The second one describes the behavior of a damper, which is divided into four parts - jounce-loading, jounce-unloading, rebound-loading and rebound-unloading. This approach gives a good approximation of the real damper system. For the comparison purpose, the numerical results of the dynamic behavior of ISU system using a real gas and an ideal gas are given in the paper.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2538-2539
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• 2000

송배전 system에서 모선관리 및 운용에 있어 초고압 차단기는 매우 중요한 역할을 담당하고 있다. 선로의 운전상태와 차단기의 투입 상황 인식 및 확인은 필수요건이다. 이러한 차단기의 운전상태를 전자적인 신호성분을 검지하여 비접촉식 개폐 확인 unit가 필수적으로 대두되고 있다. 이 unit는 고신뢰성, 고안정성을 요구하며 정확한 표시가 필요하다. 송배전의 모든 System에 적용 가능하며 적용시 선로와 차단기의 운전 및 보수에 절대적인 안정성을 제공한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1184-1187
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• 2017

The space launch vehicle needs the verification of each stage's propulsion system. The Propulsion System Test Complex(PSTC) is constructed for developing KSLV-II in the Naro space center. Hydraulic and pneumatic system of PSTC should supply propellants and various gases to propulsion system module according to required condition. This paper introduces liquid oxygen filling system of PSTC.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.1038-1047
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• 2009

The development process of a gas generator for a 30-tonf pump-fed space liquid rocket engine is described. Starting from the development of an injector, followed by subscale and full-scale test specimens, the development of LOx/kerosene fuel-rich gas generator has been concluded successfully. Various analytical methods have been utilized in the course of design and the performance requirements have been verified experimentally through ignition tests, combustion performance and stability assessment tests and duration tests. The gas generator has proven its workability and stability within a defined operation window of varying chamber pressure and mixture ratio and demonstrated compliance to the performance and life time requirements.