• Journal of the Korean Society of Propulsion Engineers
• /
• v.25 no.5
• /
• pp.65-72
• /
• 2021

700 W class laboratory model Hall thruster, which can be used for the orbit control or station keeping of small satellites, was developed. The size of the discharge channel was determined using a scaling law, and the magnetic field was designed to be symmetric with respect to the midline of the discharge channel and to be maximized outside the discharge channel. Base pressure of a vacuum chamber was maintained below 2.0×10^-5 Torr during experiments, and the thrust was measured by a thrust stand. The anode flow rate and coil current were varied with the fixed anode voltage at 300 V. Under the operation condition at 2.36 mg/s anode flow rate and 2.4 A coil current, performance was optimized as 38 mN thrust, 1,540 s total specific impulse, and 50 % anode efficiency at 620 W anode power.

• Journal of Aerospace System Engineering
• /
• v.16 no.5
• /
• pp.26-34
• /
• 2022

The propulsion system of geostationary orbiting satellites is typically used to raise the orbit into a transfer orbit, maintain the orbital position in the south/north, east/west direction in regular operation, and accumulate momentum in the south/north and east/west direction. Recently, when an electric propulsion system is used in a geostationary orbit satellite, the payload capacity can be increased by about 40% compared to a chemical propulsion system. However, despite these advantages, using an electric propulsion system has several limitations that should apply to all geostationary orbiting satellites. This paper discusses the operational constraints to consider when developing an indigenous geostationary satellite using a fully electric propulsion, radiation exposure, and control mechanism design due to unit displacement and floating ground-design. A high-voltage control unit for electric drives were analyzed.

• The Korean Journal of Emergency Medical Services
• /
• v.13 no.1
• /
• pp.19-33
• /
• 2009

Purpose : To check the legal relation between rescue team and patient as well as legal responsibility for patient's damage intentionally or erroneously caused by rescue member, a public official, in the performance of relevant job ; to prevent legal dispute over rescue team and to present program for fair settlement of dispute and equitable and feasible burden of damage. Method : First, the legal principle of Civil Law, Criminal Law and Administrative Law related to the theme of this research will be investigated around research by literature. Second, the case of dispute related to rescue team will be introduced. Result: 1. If 119 rescue members as a public official intentionally or erroneously cause damage to patient in the performance of job, they shall bear civil, criminal and administrative responsibility. They shall bear civil responsibility for indemnity for damage due to default or tort. The typical criminal responsibility includes accidental homicide arising out of duty, preparing falsified official document, dereliction of duty, etc. In the administrative side, the state is responsible for indemnity for peculiar status of the rescue member, public official. 2. Though raising civil petition or legal dispute over unsatisfactory rescue service may be reasonable to guarantee the right of nation, such action may cause stress to rescue member as well as may lead to mental shrinking and defensive attitude only to take the basic first aid treatment which has low possibility of mistake instead of active first aid treatment so as to avoid legal responsibility. 3. The program that may prevent legal dispute over 119 rescue team includes expansion of manpower specialized in first aid treatment, enhancement of education on legal environment, development and application of standard job guideline, formation of mutual trust with patient, detailed explanation, preparing and keeping minute record, improvement of the rescue members' ability of first aid treatment and development of medical instruction mode. Conclusion : The best policy is to prevent legal dispute. If it is impossible to basically exclude the possibility of dispute, however, we need to make effort to minimize the occurrence, settle fairly and divide damage equitably and feasibly. To improve the preventible death rate of our first aid system to the level of advanced country, 119 rescue team which is in charge of the stage before hospital needs to positively enforce special first aid by improving the qualitative level of rescue service and to strive to prevent legal dispute that may occur in the process.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.8
• /
• pp.939-944
• /
• 2014

Traffic accidents caused by the attention dispersion are increasing and the behavior of the attention dispersion affects the front-observing rate, road keeping ability, and reaction time for a dangerous situation. Many drivers listen to a radio broadcast and they have to change the frequency for continuously listening a radio broadcast of the specific broadcasting station in case of crossing a boundary of the particular area. In this situation, the possibility of a car accident increases, because the attention dispersion of a driver might be occurred. Especially, the risk of a car accident caused by changing the frequency of a radio is more serious in the highway, due to the high speed of a vehicle. In order to reduce the risk of a car accident caused by handling a radio during driving car, in this paper, we propose an automatic frequency conversion algorithm for vehicle radio, which saves normal system frequencies of primary broadcasting stations in a database and determines new frequency of the changed area using the location information obtained from a navigation system in a boundary of the specific area. After determining new frequency, the proposed algorithm selects a frequency with better receiving rate comparing signal-to-noise ratios (SNRs) of two signals corresponding previous and new frequencies.

• Atmosphere
• /
• v.15 no.4
• /
• pp.191-202
• /
• 2005

This study was conducted to estimate how vertically high and horizontally long a sea breeze occurred around Gangneung of the Korean peninsula would be reached to an inland. Geographically, gangneung is located on the center of the east coast shaping an arc, and a coastal line around gangneung has a form extending northwestward and southeastward, respectively. Therefore, an inflow of the northerly has similar effects of the sea breeze since a deep valley of Daegwallyeong, which is one of main ridges of the Taebaek mountains, not only reaches northeastward up to this region but also plays the part of the steering gear changing a wind direction from northerly to easterly, this is, the wind from sea. First of all, the study had defined the sea breeze as a wind blown from NNE to ESE, clockwise. And then, we analyzed characteristics of the sea breeze occurred around gangneung in view of the maximum wind speed and the wind direction for October 1st, 2003 through September 30th, 2004, the upper air database for May through June of 2004, and the wind vector database of AWS (Automatic Weather System). All meteorological information is collected at the weather station of gangneung and by the AWS which is being scattered around this region. Finally, the study figures out that how horizontally long a sea breeze would be reached depends on a level of the easterly inflow. At the first step of the inflow of the sea breeze, the wind from NNW blows into this region by keeping up the speed $3m{\cdot}s^{-1}$, and effects of the northerly are dominated with time and the wind at the inland blows out southwestward cause of the surface friction at the next step. On the other hand, there is no change of wind direction in the inflow at Daegwallyeong because a surface friction of there is smaller than around gangneung, relatively. In other word, the easterly blows toward Daegwallyeong. However, the wind speed is not higher than that of the coast around gangneung.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.10
• /
• pp.791-799
• /
• 2020

Launched in October 2019, Northrop Grumman's MEV-1 was the world's first unmanned mission demonstrating the practical feasibility of on-orbit servicing. Although the concept of on-orbit servicing was proposed several decades ago, it has been developed to various mission concepts providing services such as orbit change, station keeping, propellant and equipment supply, upgrade, repair, on-orbit assembly and production, and space debris removal. The historical success of MEV-1 is expected to expand the market of on-orbit servicing for government agencies and commercial sectors worldwide. The on-orbit servicing essentially requires the utilization of a highly propellant efficient electric propulsion system due to the nature of the mission. In this study, the space mission analysis for a simple on-orbit mission involving Hall thruster is conducted, which is life extension mission for geostationary orbit satellites. In order to analyze the mission, design space exploration for various Hall thruster design variable combinations is performed. The values of design variables and operational parameters of Hall thruster suitable for the mission are proposed through design space analysis and optimization, and mission performance is derived. In addition, the direction of further improvement for the current on-orbit mission analysis process and space mission analysis involving Hall thruster is reviewed.

• The Korean Journal of Emergency Medical Services
• /
• v.13 no.3
• /
• pp.77-90
• /
• 2009

Civil complaints and lawsuits filed in the process of providing emergency medical service include fall accident on the way of carrying the patient, transfer consent, refusal and rejection of rescue request, range and behavior restriction of emergency medical technicians, false registry of logbook, neglect of duty and emergency patient, and violation of traffic laws on the way of dispatch to the scene of accident. This study suggested the measures by cases as follows. 1. The accidents on the way of carrying a patient could be divided into fall of patient and fall by paramedic's mistake. In the former case, damages caused by the ambulance's shaking must be notified to the patient and guardian and recommended to fasten seat belt, in the latter case, the plan of patient's posture, route of transport, rescue and equipments should be comfirmed before fixing the patient. 2. Transfer consent must be made as implied when the patient is unconscious under delusion and was not able to consent physically, and paramedic must take an action by his judgment and record details of services on logbook. 3. When a patient refused to transfer, get 'confirmation of transfer refusal' and inform him of refusal. Paramedic should receive the signature. In addition, in case of refusal, transfer request should be made after hearing doctor's opinion and it should be notified to transfer request and superintendent of fire station after making 'confirmation of transfer refusal'. 4. Emergency medical technicians should perform their duties within the range of services prescribed by Article 41 of Law of Emergency Medical Service and Article 33 of Its Enforcement Regulations and shall not make announcement of death. In case of reporting the death to guardian, it is desirable to use record data like ECG results. 5. The best way to have protection from legal problems is making and keeping the exact records of accident and patient. Paramedic should not mention his subjective opinion about the accident-related matter. He must record correctly and keep the original medical records. 6. As emergency medical technicians are responsible for taking care of emergency patients, they must contact a briefing room when they meet a difficult situation suddenly due to vehicle stop or treatment of other patients and then must have support from neighboring hospital and other safety centers. 7. Since the ambulance operator is responsible for safety and careful driving of ambulance, he must be careful when he violates traffic regulations unavoidably. The operator should drive slowly below 10km/h at an intersection and pass it after getting way from general vehicles driving from all directions.

• Journal of Bio-Environment Control
• /
• v.23 no.3
• /
• pp.212-220
• /
• 2014

This study was conducted to investigate the effect of 1-methylcyclopropene (1-MCP), a known ethylene action inhibitor, on fruit quality and incidence of physiological disorders during simulated marketing period in Asian pears (Pyrus pyrifolia Nakai) of early-season cultivar 'Hanareum' and mid-season cultivar 'Manpungbae'. Flesh firmness was decreased abruptly at 15 days after shelf-life in untreated fruit of early-season cultivar 'Hanareum' which showed less than 19N, although those of 1-MCP-treated fruits were kept high value (>28N) during 15 days of shelf-life. However, there were no distinct firmness changes during 30 days of shelf-life in mid-season cultivar 'Manpungbae' pear. Two pear cultivars did not show any considerable differences in quality indices such as soluble solids content, titratable acidity and skin color during the shelf-life regardless of 1-MCP treatment. The reduction of ethylene production level by 1-MCP treatment did not appeared in 'Hanareum' pear. Meanwhile, 1-MCP treated 'Hanareum' pears showed significantly low respiration rate during shelf-life. On the other hand, the inhibitory effect of 1-MCP was not remarkable in mid-season 'Manpungbae' pears. 1-MCP treatment completely blocked the incidence of physiological disorders including core browning and mealiness symptom during shelf-life only in early-season 'Hanareum' pears, and reduced considerably the pithiness disorder regardless of 1-MCP concentration. Consequently, we concluded that the treatment efficacy of 1-MCP is largely cultivar-dependent and the use of $1{\mu}L{\cdot}L^{-1}$ 1-MCP was recommended for the keeping quality and the prevention of physiological disorders only in early-season Asian pear 'Hanareum'.

• Journal of Bio-Environment Control
• /
• v.20 no.4
• /
• pp.399-405
• /
• 2011

In this study, we evaluated the fruit quality indices and the incidence of physiological disorders of Korean new pear cultivar 'Whasan' to determine appropriate harvest time for exportation and to enhance storability and shelf-life of the fruits during simulated exportation and extending market environment under different temperature conditions. In the experiment of simulated exportation headed for North America including Canada and U.S.A., the fruits transported at $1^{\circ}C$ showed less weight loss than those of $5^{\circ}C$. Market temperature appeared as a key factor for keeping freshness of exported pear fruits rather than transportation temperature. Quality factors such as high flesh firmness and low incidence of fruit rot and physiological disorders including core breakdown and pithiness were attained at the fruits maintained at $18^{\circ}C$ when we compared with $25^{\circ}C$. The fruits of harvested early maturity at 135 day after full bloom showed 28.6 N of flesh firmness when the fruits stored at $1^{\circ}C$ of transportation and $18^{\circ}C$ of market temperature, while the fruits progressed $5^{\circ}C$ of transportation and $25^{\circ}C$ of market temperature dropped to 24.2 N during 30 days of shelf life. Also, a high incidences of physiological disorders and of fruit decay rates were obvious in the fruits distributed at $25^{\circ}C$ were observed approximately two times higher than the those of $18^{\circ}C$. Therefore, temperature management during marketing resulted as an important point for maintaining fruits quality in the process of pear fruit exportation.