• Journal of Ocean Engineering and Technology
• /
• v.19 no.5 s.66
• /
• pp.16-25
• /
• 2005

The effect of vertical riser support system on the dynamic behaviour of a classical spar platform is investigated. Spar platform generally uses buoyancy-can riser support system, but as water depth gets deeper the alternative riser support system is required due to safety and cost issues. The alternative riser support system is to hang risers off the spar platform using pneumatic cylinders rather than the buoyancy-can. The existing numerical model for hull/mooring/riser coupled dynamics analysis treats riser as an elastic rod truncated at the keel (truncated riser model), thus, in this model, the effect of riser support system can not be modeled correctly. Due to this reason, the truncated riser model tends to overestimate the spar pitch and heave motion. To evaluate more realistic global spar motion, mechanical coupling among risers, guide frames and support cylinders inside of spar moon-pool should be modeled. In the newly developed model, the risers are extended through the moon-pool by using nonlinear finite element methods with realistic boundary condition at multiple guide frames. In the simulation, the vertical tension from pneumatic cylinders is modeled by using ideal-gas equation and the vertical tension from buoyancy-cans is modeled as constant top tension. The different dynamic characteristics between buoyancy-can riser support system and pneumatic riser support system are extensively studied. The alternative riser support system tends to increase spar heave motion and needs damper system to reduce the spar heave motion.

• Journal of Energy Engineering
• /
• v.24 no.1
• /
• pp.69-77
• /
• 2015

The PMV regression analysis was conducted for this model based on a database of the PMV variables. PMV regression model simplification was completed through sensitivity and data analysis. The simplified PMV regression model's and Fanger PMV model was confirmed through MAE and RMSE. And the EMS in EnergyPlus was used to establish a simplified PMV regression analysis-based thermal comfort control. Also, the thermal comfort controls based on simplified PMV model and the Fanger PMV model were applied to the building model, it was confirmed that both controls met the thermal comfort range in more than 90% of cases during the air conditioning period.

• Environmental Analysis Health and Toxicology
• /
• v.27
• /
• pp.8.1-8.10
• /
• 2012

Objectives: The goal was to model and quantify the atmospheric concentrations of volatile organic compounds (VOCs) as the result of the Hebei Spirit oil spill, and to predict whether the exposure levels were abnormally high or not. Methods: We developed a model for calculating the airborne concentration of VOCs that are produced in an oil spill accident. The model was applied to a practical situation, namely the Hebei Spirit oil spill. The accuracy of the model was verified by comparing the results with previous observation data. The concentrations were compared with the currently used air quality standards. Results: Evaporation was found to be 10- to 1,000-fold higher than the emissions produced from a surrounding industrial complex. The modeled concentrations for benzene failed to meet current labor environmental standards, and the concentration of benzene, toluene, orthometa- para-xylene were higher than the values specified by air quality standards and guideline values on the ocean. The concentrations of total VOCs were much higher than indoor environmental criteria for the entire Taean area for a few days. Conclusions: The extent of airborne exposure was clearly not the same as that for normal conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.29 no.10
• /
• pp.73-82
• /
• 2015

This paper proposes an ripple reduction algorithm and analyzes the effects of offset and scale errors generated by voltage sensor while measuring grid voltage in grid-tied single-phase inverters. Generally, the grid-connected inverter needs to detect the phase angle information by measuring grid voltage for synchronization, so that the single-phase inverter can be accurately driven based on estimated phase angle information. However, offset and scale errors are inevitably generated owing to the non-linear characteristics of voltage sensor and these errors affect that the phase angle includes 1st harmonic component under using SRF-PLL(Synchronous Reference Frame - Phase Locked Loop) system for detecting grid phase angle. Also, the performance of the overall system is degraded from the distorted phase angle including the specific harmonic component. As a result, in this paper, offset and scale error due to the voltage sensor in single-phase grid connected inverter under SRF-PLL is analyzed in detail and proportional resonant controller is used to reduce the ripples caused by the offset error. Especially, the integrator output of PI(Proportional Integral) controller in SRF-PLL is selected as an input signal of the proportional resonant controller. Simulation and experiment are performed to verify the effectiveness of the proposed algorithm.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.3
• /
• pp.827-834
• /
• 2010

We have performed numerical simulations of the electrical characteristics for multi-layer organic light emitting diode devices with doped emitting layer using a commercial simulation program. In this paper, the basic structure consists of the ITO/NPB/$Alq_3$:C545T(%)/$Alq_3$/LiF/Al, four devices that were composed of $Alq_3$ as the host and C545T as the green dopant with different concentration, were studied. As the result, the variations of the doping concentration rate of C545T have a effect on the voltage-current density characteristics. The voltage-current characteristics are quite consistent with the results which were experimentally determined in a previous reference paper. In addition, the voltage-luminance characteristics were greatly improved, and the luminous efficiency was improved three times. In order to analyze these driving mechanism, we have investigated the distribution of electric field, charge density of the carriers, and recombination rates in the inner of the OLED devices.

• The Korean Journal of Emergency Medical Services
• /
• v.19 no.2
• /
• pp.7-17
• /
• 2015

Purpose: This study aimed to compare the effects of rescue ventilation maneuvers on the quality of two-rescuer cardiopulmonary resuscitation (CPR). Methods: We implemented mouth to mouth (MMV), mouth to pocket mask (MPV) and bag-valve mask ventilation (BMV) maneuvers. Each team of two-nurses was randomized to perform three consecutive sessions of two-rescuer CPR by using three artificial ventilation maneuvers. Results: The subjects were 26 teams of nurses (female: 96.2%, male: 3.8%, age: 26.6 years). Failed ventilation was more frequent in BMV ($2.23{\pm}2.21$, p <.001) than MMV ($0.31{\pm}0.74$) and MPV ($0.38{\pm}0.64$). BMV had more compressions per minute ($93.7{\pm}5.7$) than MMV ($87.0{\pm}7.2$, p = .001) and shorter total compression pause time ($46.1{\pm}5.8sec$) and compression pause fraction ($23.3{\pm}2.2%$) than MMV ($54.8{\pm}10.3sec$, p = .001, $25.5{\pm}3.5%$, p = .001, respectively) and MPV ($53.1{\pm}7.1sec$, p =. 006 and $25.8{\pm}2.6%$, p = .006, respectively). Conclusion: In our simulation study, BMV reduced the compression pause time and increased the number of compressions per minute, thus indicating CPR provided to patients was effective. However, considering the high rate of ventilation failure, we recommend periodic training.

• Women's Health Nursing
• /
• v.16 no.2
• /
• pp.166-176
• /
• 2010

Purpose: The study was done to examine the effects of cognition-behavior integrated breast cancer prevention education, in which a breast model with interchangeable nodules was utilized, on the self-competency of nursing students in performing breast cancer education. Methods: A nonequivalent control group non-synchronized design was used. A traditional lecture intervention was provided for 49 3rd year college of nursing students (control group) while the integrated breast cancer prevention education was given to 47 3rd year students in the same college one year later (experimental group). The integrated breast cancer prevention education was developed by the research team to strengthen the competency of cognitive and behavioral components in education on breast cancer. Results: Effects of the intervention were found to be significant through all study variables: knowledge about breast cancer (t=7.79, p <.001), breast cancer risk awareness (t=2.05, p <.05), self-competency of breast self-exam (t=8.27, p <.001), and intention to teach breast self-exam (t=3.87, p <.001). Conclusion: The integrated breast cancer prevention education was useful to improve not only knowledge about breast cancer but competency in performing breast examination for nursing students who acquired technical skills from various simulation nodules. As the program helped the students to be prepared as confident educators, future application of the module is recommended for academic curricula.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.4
• /
• pp.10-15
• /
• 2013

For design optimization, engineers should require the accurate information of design space and then explore the design space and carry out optimization. Recently, the total design framework, based on design of experiments and optimization, is widely used in industry areas to explore the design space above all. For optimizing turbofan engine design point, the response surface model is constructed by using the 7 level orthogonal array which satisfies the statistical uniformity and orthogonality and gets the dense design space information. The multi-objective genetic algorithm is used to find the optimal solution within the given constraints for finding global optimal one in response surface model. The optimal solution from response surface model is verified with GasTurb simulation result.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.5
• /
• pp.399-405
• /
• 2021

In the present study, ground tests and CFD simulations for a ducted fan system were performed to verify the hovering performance of the ducted fan system designed by KARI rotorcraft team. Six blades were composed for the ducted fan, and target rotating speed of the fan was decided to 4,000 RPM. Collective pitch angles were considered from 20 degrees to 36 degrees. The test data were obtained by increasing the rotating speed up to 4,000 RPM in 1,000 RPM increments. The CFD simulations were considered only 4,000 RPM of rotating speed. The hovering performance was represented by thrust, power, duct thrust ratio, and FM(Figure of Merit). Reliability of the performance results was ensured through the test and simulation results, and it was found that the target performance was achieved under conditions above 31 degrees of the pitch angle.

• Composites Research
• /
• v.32 no.2
• /
• pp.113-119
• /
• 2019

The objective of this research is to study the mechanical and vibration characteristics of vibration damping aluminum panels for automotive parts. For this purpose, the test and simulation results of aluminum-resin hybrid materials and aluminum sheet materials were compared. Tensile strength and elastic modulus of the hybrid material were approximately 10% lower than aluminum sheet. Also, it was showed that the hybrid material have lower natural frequency than aluminum sheet, and it was confirmed that loss factor increases as the thickness of resin increases. Finally, it is confirmed that the test results and the analysis results are similar with each other and the performance prediction of the materials are possible by FEA.