• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.04a
• /
• pp.588-593
• /
• 2011

The Main design parameters of ship HVAC systems are pressure drop and noise analysis of ducts. The Noise prediction for HVAC(Heating, Ventilating and Air Conditioning) systems are normally performed by empirical method suggested by NEBB(National Environmental Balancing Bureau, 1994), but NEBB's method is not suitable for the ship HVAC systems. In this paper, numerical analysis methods are used to develop a noise prediction method for the ship HVAC systems, especially for large ducts. To develop regression formula of attenuation of sound pressure level in large duct, Boundary Element Method(BEM) is used. Using dynamic loss coefficient which is suggested by ASHRAE fitting data base and numerical methods of HVAC noise analysis, integrated HVAC noise analysis of Program is developed. The developed program can present pressure drop and noise analysis of the ship HVAC systems. To verify the accuracy and convenience of the developed program, prediction of HVAC system for Semi-Submersible Drilling RIG is carried out and the results are compared with measurement of noise level during sea trial.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.807-812
• /
• 2011

Fuel-side cold-flow tests were performed on the technology demonstration model of a 75 ton-class liquid rocket engine combustion chamber for the first stage of the Korea space launch vehicle II. Pressure drop in the cooling channels of the combustion chamber was measured by changing fuel mass flow rate through a pressure regulating system. Pressure drop in each segment of the chamber could be obtained and a lot of pressure drop was caused by high flow velocity in the nozzle throat segment. The accuracy of a hydraulic analysis method for calculating a pressure loss in cooling channels could be verified by applying it to the cold-flow test conditions.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1367-1372
• /
• 2008

A plate type supporting structure of a tube bundle in axial flow generates a certain band of a high frequency periodic excitation of a vortex shedding and/or a flow separation due to sharp edge of the plate thickness and a severe pressure drop due to a cross-sectional area of the supports. With a design consideration of the low vibration and a small flow resistance, the analysis method is uniquely confined to an experimental approach because a complex geometry of a cylindrical tube bundle and/or physical phenomena related to the fluid-structure interaction of tube bundle in a flow impede a theoretical or a numerical approach. A 5x5 cylindrical tube bundle with 5 supports which were discretely located along the bundle's axis was tested in the FIVPET hydraulic test loop for a design evaluation and an analysis perspectives. A high frequency flow-induced vibration of the supporting structures of the cylindrical tube bundle was measured at a outer surface of a supporting structure through a transparent flow housing by the laser dopper vibrometer. Pressure drop in-between three measurement distances was measured by the differential pressure transmitter. High frequency vibration and pressure drop fairly depends on the geometric design of supporting structure. So, these two parameters would be used as a qualitative design variables for design evaluation and analysis.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.16 no.6
• /
• pp.56-61
• /
• 2012

Fuel-side cold-flow tests were performed on the technology demonstration model of a 75 ton-class liquid rocket engine combustion chamber for the first stage of the Korea space launch vehicle II. Pressure drop in the cooling channels of the combustion chamber was measured by changing fuel mass flow rate through a pressure regulating system. Pressure drop in each segment of the chamber could be obtained and a lot of pressure drop was caused by high flow velocity in the nozzle throat segment. The accuracy of a hydraulic analysis method for calculating a pressure loss in cooling channels could be verified by applying it to the cold-flow test conditions.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.163.2-163.2
• /
• 2005

• Proceedings of the Korea Institute of Convergence Signal Processing
• /
• 2000.08a
• /
• pp.73-76
• /
• 2000

본 논문에서는 다중접속 프로토콜인 PRMA의 변형된 모델에 대해서 다뤘다. 기존의 PRMA에서는 초기 엑세스시 얻은 슬롯을 휴지기에 잃게 되므로 매 활성기마다 다시 슬롯을 엑세스함으로써 추가적인 패킷의 drop이 발생하는 반면, 변형된 모델에서는 슬롯예약을 유지하기 위한 제어미니슬롯을 사용함으로써 초기 엑세스 이후의 추가적인 패킷 drop이 발생하지 않는다.

• Tuberculosis and Respiratory Diseases
• /
• v.83 no.1
• /
• pp.89-95
• /
• 2020

Background: Same-day sputum microcopy is recommended in areas where sputum smear microscopy external quality assessment (EQA) is effectively implemented and sturdy. In Addis Ababa, the status of EQA and drop-out of same-day sputum smear microcopy has not yet been assessed. The objective of this study was to assess the quality of same-day sputum smear microscopy and diagnostic drop-out of presumptive tuberculosis (TB) patients in health facilities (HFs) across Addis Ababa, Ethiopia. Methods: Amulti-analysis was conducted from September 2016 to July 2017 to determine the status of external quality assessment and diagnostic drop-out of presumptive TB patients registered for same-day sputum smear microscopy. Data was coded and entered in Microsoft Excel, and subsequently transferred and analyzed using SPSS version 20.0. Results: The drop-out of same-day sputum smear microscopy was 209 (6.2%). More than 33% of the specimens collected for purposes of same-day sputum smears were of poor quality. Among the selected HFs for the study: 13 (46.4%) used filter reagents prior to sputum smear staining while 75% of the selected HFs for the study used smear microscopy services interruption in a year. The sensitivity and specificity of the HFs participating in regional quality assessment scheme for the diagnosis of TB was 97.4% and 99.6%, respectively. Conclusion: The diagnostic drop-out of same-day sputum smear microscopy was high in Addis Ababa. Strengthening EQA, competency-based laboratory professionals training on sputum smear microscopy might reduce the reading errors in sputum smear. Awareness creation of the community on the benefits gained from completion of specimen provision for the same-day approach decreases diagnostic drop-out and enhances TB control program.

• Korean Journal of Applied Biomechanics
• /
• v.20 no.1
• /
• pp.67-73
• /
• 2010

The purpose of this study was to compare the differences in kinematic and kinetic parameters of the ankle and knee joint according to three landing direction(central, left, right). Fifteen collegiate male athletes(age: $22.7{\pm}3.5$ years, height: $174.9{\pm}7.1\;cm$, weight: $69.4{\pm}6.7\;kg$) with the right leg as dominant were chosen. The subjects performed series of drop landings in three directions. In terms of the three different landing directions, plantar flexion was the greatest during the central drop landings. For each initial contact of the landing direction, plantar flexion of the ankle was greatest at the central drop landing, inversion of the ankle was greatest at the right landing and valgus of the knee was greatest at the left drop landing. Regarding the peak force, the greatest was at the 1st peak force during the central drop landing. For the time-span of the 2nd peak force and the 2-1 peak force, both right sides resulted as the greatest. Therefore, with the appropriate training in landing techniques and developing neuromuscular training for proprioception by taking the injury mechanisms on ankle and knee during drop landings into account, it will assist in preventing such injuries.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.15 no.5
• /
• pp.411-416
• /
• 2010

A voltage drop characteristics of a transformer-based voltage disturbance generator with series transformers is analysed. It is well known that a voltage disturbance generator with series transformer is cost-effective and reliable compared with other types. The voltage drop depends on the %Z of the transformer, power rating, and output power factor. A wrong design of the transformer results in a severe voltage drop, which can not guarantee the proper performance of the generator. The voltage drop is analysed under the condition of 10kVA output power rating and 4% of %Z with the variation of power factor. It is found through simulations and experiments that the drop increases as the power factor decreases in lagging mode, and the drop is 4% of the rated voltage in case of 0.85 lagging power factor.

• Journal of the Korean Electrochemical Society
• /
• v.3 no.4
• /
• pp.241-245
• /
• 2000

The objective of this work Is to design, fabricate, and characterize pseudo-capacitor using amorphous $MnO_2\;nH_2O$ electrode material. The cyclic voltammogram under 100mV/s scan rate of the material shows the electrochemically stable potential window of 1V and the specific capacitance of 250F/g. The TDMA pulse test result indicates that the TDMA system (2 parallel-pseudo-capacitor systems) has the ohmic voltage drop of 0.22V and the capacitor voltage drop of 0.38V. The total voltage drop of the TDMA system is 0.60V and less than 1V of which value is the maximum voltage drop requirement or the TDMA satellite phone. Also, the TDMA system had the ESR of $55m{\Omega}$ and the capacitance of 105mF. Therefore, it is confirmed that the TDMA system has the application feasibility as load-leveling capacitor for the satellite phone.