• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.1
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• pp.134-145
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• 2021

It is common to optimize the propulsion control system through a so-called tuning process that modifies the parameter values of the propulsion control software during a ship commissioning. However, during this process, if the error of the initial setting value is large, the tuning time may take too long, or the propulsion equipment can be seriously damaged. Therefore, we conducted research on the design of a propulsion controller that applied a Processor lever controller even for inexperienced people with relatively little experience in tuning propulsion control software to be able to reduce the tuning time while protecting the propulsion system. Through simulation, by comparing the execution result of propulsion control lever commands through the PI controller without applying the Processor lever controller. We analyzed the improvement of the Overshoot and propulsion performance. The simulation results showed that the safety of the propulsion system increased because Overshoot of approximately 9.74%, which occurred when the Processor lever function was not applied.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.1
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• pp.59-66
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• 2022

In order to solve the problem of urban traffic congestion, Urban Air Mobility (UAM) concept using Electric Vertical Take-off and Landing (eVTOL) aircraft has been gaining popularity, and many domestic and international studies are underway. However, since these aircraft inevitably fly over densely populated areas, it is essential to ensure safety, which starts with accurately analyzing the crash risk. In this paper, the locations and impact speeds of crash are computed using six degree-of-freedom simulations of an eVTOL aircraft in a fixed-wing mode. System malfunction was modeled by a sudden loss of thrust with control surfaces being stuck during cruise. Because most of these eVTOL aircraft are still under development, a methodology of constructing a six degree-of-freedom dynamics model from generic specification is also developed. The results show that the crash locations are highly concentrated right under the aircraft within a square that has an edge length similar to the cruise altitude. Speed distribution is more complicated because almost identical crash locations can be achieved by two very different paths resulting in a large variation in the speeds.

• Journal of the Korean Electrochemical Society
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• v.25 no.4
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• pp.184-190
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• 2022

Spinel LiMn₂O₄ (LMO) and layered LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) are widely used as positive electrode materials for lithium-ion batteries. LMO and NCM positive electrode materials have a complementary properties. LMO has low cost and high safety and NCM materials show a relatively high specific capacity and better cycle life even at elevated temperature. Therefore, the LMO and NCM active materials are blended and used as a positive electrode in large-size batteries for electric vehicles (xEV). In this study, the cycle performance of a blended electrode prepared by simply mixing LMO and NCM and a bi-layer electrode in which two electrode layers aree sequentially coated are compared. The bi-layer electrode prepared by composing the same ratio of both active materials has similar capacity and cycle performance to the blend electrode. However, the LN electrode coated with LMO first and then NCM is the best in the full cell cycle performance at elevated temperature, and the NL electrode, in which NCM is first coated with LMO has a faster capacity degradation than the blended electrode because LMO is mainly located on the top of the electrode adjacent to electrolyte and graphite negative electrode. Also, the LSTA (linear sweep thermmametry) analysis results show that the LN bi-layer electrode in which the LMO is located inside the electrode has good thermal stability.

• The Korean Journal of Nuclear Medicine Technology
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• v.27 no.1
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• pp.47-54
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• 2023

Purpose PET-CT imaging require an appropriate quality assurance system to achieve high efficiency and reliability. Quality control is essential for improving the quality of care and patient safety. Currently, there are performance evaluation methods of UN2-1994 and UN2-2001 proposed by NEMA and IEC for PET-CT image evaluation. In this study, we compare phantom images with the same experiments before and after PET-CT 3D normalization and well counter correction and evaluate the usefulness of quality control. Materials and methods Discovery 690 (General Electric Healthcare, USA) PET-CT equiptment was used to perform 3D normalization and well counter correction as recommended by GE Healthcare. Based on the recovery coefficients for the six spheres of the NEMA IEC Body Phantom recommended by the EARL. 20kBq/㎖ of ¹⁸F was injected into the sphere of the phantom and 2kBq/㎖ of ¹⁸F was injected into the body of phantom. PET-CT scan was performed with a radioacitivity ratio of 10:1. Images were reconstructed by appliying TOF+PSF+TOF, OSEM+PSF, OSEM and Gaussian filter 4.0, 4.5, 5.0, 5.5, 6.0, 6,5 mm with matrix size 128×128, slice thickness 3.75 mm, iteration 2, subset 16 conditions. The PET image was attenuation corrected using the CT images and analyzed using software program AW 4.7 (General Electric Healthcare, USA). The ROI was set to fit 6 spheres in the CT image, RC (Recovery Coefficient) was measured after fusion of PET and CT. Statistical analysis was performed wilcoxon signed rank test using R. Results Overall, after the quality control items were performed, the recovery coefficient of the phantom image increased and measured. Recovery coefficient according to the image reconstruction increased in the order TOF+PSF, TOF, OSEM+PSF, before and after quality control, RCmax increased by OSEM 0.13, OSEM+PSF 0.16, TOF 0.16, TOF+PSF 0.15 and RCmean increased by OSEM 0.09, OSEM+PSF 0.09, TOF 0.106, TOF+PSF 0.10. Both groups showed a statistically significant difference in Wilcoxon signed rank test results (P value<0.001). Conclusion PET-CT system require quality assurance to achieve high efficiency and reliability. Standardized intervals and procedures should be followed for quality control. We hope that this study will be a good opportunity to think about the importance of quality control in PET-CT

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.6
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• pp.853-861
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• 2018

This paper proposes the application of harmonic constraints to address the problems caused by abnormal voltage increases when electric railway vehicles are running. The AC line that supplies the train with power during operation is used to provide electricity of 25kV/60 Hz, but gradually the size and frequency of harmonics involved in the line are varied with the technological evolution of the railroad vehicle electrical equipment. An increase in heat losses due to the failure of the instrument transformer (PT), the main circuit device, which is a serious problem with the recent train safety operation, or to the main displacement voltage. When high frequency components are introduced through low frequency Transformers of the main circuit device, the high intensity of the components is caused by the high intensity of the core and the current flow of the parasitic core is increased, thus generating heat. To solve this problem, the recent adjustment of the sequence has applied artificial NOTCH OFF of the power converter. However, the method of receiving and controlling the OFF signal operates by interaction between the ground and the vehicle's devices, thus it is invalid in the event of failure, and an actual accident is occurring. Therefore, the harmonic currents were required to prevent possible flow of harmonics, and conducted a study to prevent accidental occurrence of train accidents and to verify feasibility of the device through the simulations of the train's experimental analysis and the simulations of the train for safe operation.

• Advanced Industrial SCIence
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• v.2 no.2
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• pp.9-15
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• 2023

Since silicone rubber heaters are flexible, they can be directly attached or installed in objects to be heated even in flat, curved or three-dimensional shapes. Since the current heating method heats the entire object to be heated and raises it to a required temperature, ignoring areas or positions where heat is not required, partial intensive heating cannot be performed. When using multi-heating zones, rather than heating the entire object to be heated, only the parts that need heat are intensively heated according to the process, so it is possible to heat quickly by local location by applying different amounts of heat with a small amount of electric capacity to each place that needs heat, and heat energy can reduce. In this study, the temperature and heating time of the partially concentrated region in the multi-heating region structure are measured so that a uniform temperature or temperature difference occurs in the region requiring thermal fusion. In order to determine the optimal power density range and reduce capacitance, the safety of a silicon rubber heater manufactured with a multi-heating zone structure is investigated. If the silicon rubber heater is manufactured in a multi-heating method, the multi-intensive heating technology can be ideally applied to all heating processes.

• Fire Science and Engineering
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• v.28 no.3
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• pp.10-19
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• 2014

The fast evacuation from fire floors to evacuation floors in high-rise building fires can minimize the human damage. In this study, an evacuation instrument, which are applicable to the high-rise buildings of adaptable escape mechanisms by the current NFSC 301 (national fire safety code 301), were selected to analyze the applicability in the high-rise buildings over 11th floor through the site adaptability test. The results of the site test were as follows. The elevator type evacuation instrument of new concept developed as a new technology by compensating the defect of evacuation instrument limiting in the high-rise buildings over 11th floor had completed the stability test and the performance certification test in fire stations, which there were no problems in the introduction of the elevator type evacuation instrument as an escape mechanism in the high-rise buildings. The elevator type evacuation instrument using escapers' weight without using electric power was an escape mechanism that many people could evacuate in a short period of time when a fire broke out in the high-rise buildings. In particular, The elevator type evacuation instrument operated by nonpower had the adaptability as a customized escape mechanism considering user characteristics in the buildings for the disabled or patients with an advanced disease.

• Fire Science and Engineering
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• v.31 no.3
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• pp.63-72
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• 2017

This study fabricated a low-voltage 10 circuit distribution board based on the KEMC (Korea Electrical Manufacturers Cooperative) 2102-610 standard and performed a characteristics assessment of the developed 10 circuit distribution board to secure product stability. The developed 10 circuit distribution board is designed to have the characteristics of insulation materials, as well as resistance to corrosion ultraviolet radiation and mechanical impact. The developed distribution board is fabricated to have an appropriate protection class of enclosure, electric shock prevention and protection circuits, switchgear and its components, internal electrical circuits and connectors, external conduct terminal, insulation characteristics, temperature rise test, heat resistance, etc. The developed 10 circuit distribution board consists of a single phase circuit and 3-phase circuits. It is possible to measure in real time the leakage current generated from the load distribution line by installing a sensor module at the load side of each of the branched switchgears. In addition, it is possible to increase a circuit according to the use and purpose of the load and to also manage and check the load in real time. Temperature rise tests were performed on the developed 10 circuit distribution board at 18 places including the inlet connection, main circuit and distribution circuit bus bars and bus bar supports, etc. The highest temperature of $65.3^{\circ}C$ was measured at the R-Phase of the connection of the MCCB power supply for the branch circuit bus bar and a temperature rise of $61.6^{\circ}C$ was measured at the T-Phase of the load side. When applying thermal stress to an MCCB for 6 hours at $180^{\circ}C$ using a heat resistant experimental device, it was found that the actuator lever was transformed and moved in the tripped state.

• Korean Journal of Oriental Medicine
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• v.16 no.3
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• pp.85-93
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• 2010

The aim of this review is to investigate clinical studies on oriental medicine treatment for obesity in Korean literature and to propose for the better method of clinical studies in order to seek more effective treatment. Electric searches were performed with NDSL, National assembly library, RISS4U, DBPIA, KISS, KMBASE, KoreaMed, Korean traditional knowledge portal and Oasis. Also, 21 major journals associated with oriental medicine in Korea were searched manually. Eighty three studies were included and analyzed in terms of study design, subjects, interventions, results and evaluation of safety. The numbers of controlled, non-controlled and case studies are respectively 26(31%), 43(52%) and 14(17%). Studies using sample size less than 30 accounts for 49% and studies using subjects diagnosed as obese or overweight by specific criteria were 35(42%). Studies which used more than 2 interventions or co-interventions were 76%. Clinical studies which used single herbal medicine were few and clinically studied single herbal medicine were limited to ephedra. More than half of 83 studies were studied for 8 weeks and less. 12% of 69 studies(except case studies) were not statistically analyzed and studies which evaluated safety of intervention were 22(27%) and reported adverse events were 9(11%). To improve the quality of clinical studies on oriental medicine treatment for obesity, studies need to use restricted number of interventions and subjects need to specifically diagnosed as overweight or obese. In addition, various kinds of single herbs need to be clinically studied based on experimental studies and herbalogy.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.18 no.4
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• pp.310-317
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• 2008

The objective of the survey is to define and judge exposure profiles semi-qualitative data in high risk processes using styrene. The survey was conducted on 98 factories out of 229 factories based on data from periodic working environment monitoring for styrene. Styrene is widely utilized as a raw material for PS and co-polymers such as ABS, SAN, SBR, SBL, unsaturated polyester resins(UPR) and others. An approximate breakdown of styrene's markets in Korea is PS 30%, expandable PS 17%, ABS 33%, SAN 5%, SBL 4%, SBR 3%, UPR 1% and other 7%. Although UPR accounts for 1% of total amount of styrene, workers dealing with it are exposed to very high concentrations up to 64 ppm. Especially styrene is widely used in the laminating process of fiberglass reinforced plastics(FRP) manufacturing industry. The Applications using styrene are largely classified into two sections which are applied to styrene monomer(SM) and UPR. SM is utilized for a raw material of resins, surfactant and adhesive. UPR is employed for FRP and non-FRP. For SM control targets are mixing colors and packing in the gelcoat resins manufacturing industry(MI), for UPR control targets out of works using UPR are 1) laminating in the MI of plastics, automobile parts and boats, 2) mixing and packing in the SMC/BMC MI, 3) molding and cutting in the other specific plastics MI, 4) mixing and coating in artificial marble product MI, 5) dipping in the electric motors & transformers MI, 6) molding in the button MI, 7) painting in the musical instrument MI. Findings from the study have given the information for the high risk processes and working practices so that occupational health professionals could focus on targeted workplaces to prevent occupational diseases. It is also useful to develop a control strategies and specific controls for high risk processes and facilities using styrene.