• Journal of Digital Convergence
• /
• v.8 no.2
• /
• pp.103-114
• /
• 2010

People generally focus on the supply side when conducting a study on the movie industry. However, to understand the movie industry better, one needs to analyze both sides - the demand and supply of movies. This paper analyzes demand-side factors that have long been taken for granted in Korea's movie industry. The study used data for 1991~2008 on the following demand-factors : the average ticket prices, the number of working days and hours, the average personal income, the number of spectators for the two major professional sports, cable TV, the number of movies released each year and the number of movie screens. This study shows that ticket prices do not conform to the law of demand. According to the law of demand, increasing price leads to a decline in demand. However, in reality, the number of viewers went up along with ticket prices. The study found that demand for movies was correlated to income levels and leisure time. An increase in the number of leisure hours and income levels pushed up demand. Contrary to general belief, a growth in the availability of substitutes, such as professional sports(soccer and baseball), did not result in a fall in demand for movies. The audiences for both sports and movies grew simultaneously as the amount of leisure time increased. Contrary to the general expectations that more diversified genres of movies will draw larger audiences by satisfying different individual tastes, the diversification had little impact, but the number of movie screens was positively correlated with audience size. In sum, changes in ticket prices and the quantity of substitutes had little influence on demand in the movie industry. Rather, it was the supply side of the industry that induced demand.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.2
• /
• pp.121-141
• /
• 2017

The thermal analysis of an underground power conduit for electrical cables is essential to determine their current capacity with an increasing number of demands for high-voltage underground cables. The temperature rises around a buried cable, caused by excessive heat dissipation, may increase considerably the thermal resistance of the cables, leading to the danger of "thermal runaway" or damaging to insulators. It is a key design factor to develop the mechanism on thermal behavior of backfilling materials for underground power conduits. With a full-scale field test, a numerical model was developed to estimate the temperature change as well as the thermal resistance existing between an underground power conduit and backfill materials. In comparison with the field test, the numerical model for analyzing thermal behavior depending on density, moisture content and soil constituents is verified by the one-year-long field measurement.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.4
• /
• pp.325-330
• /
• 2004

Several kinds of low voltage cables have been used in nuclear power plants for the supply of electric power, supervision, and the propagation of control signals. These low voltage tables must be inspected for safe and stable operation of nuclear power plants. In particular, the degradation diagnosis to estimate the integrity of low voltage rabies has recently been emphasized according to the long use of nuclear power plants. In order to evaluate their degradation, the surrounding temperature, hardness of insulation material, elongation at breaking point (EAB), etc. have been used. However, the measurement of temperature or hardness is not useful because of the absence of quantitative criteria; the inspection of a sample requires turning off of the power plant power; and, the electrical inspection method is not sufficiently sensitive from the initial through the middle stage of degradation. In this research, based on the theory that the ultrasonic velocity changes with relation to the degradation of the material, we measured the ultrasonic velocity as low voltage cables were degraded. To this end, an ultrasonic degradation diagnosis device was developed and used to measure the ultrasonic velocity with the clothing on the cable, and it was confirmed that the ultrasonic velocity changes according to the degradation of low voltage cables. The low voltage cables used in nuclear power plants were degraded at an accelerated rate, and EAB was measured in a tensile test conducted after the measurement of ultrasonic velocity. With the increasing degradation degree, the ultrasonic velocity decreased, whose potential as a useful parameter for the quantitative degradation evaluation was thus confirmed.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.32 no.4
• /
• pp.381-392
• /
• 2022

Objectives: Objective of this study is to review briefly exposure characteristics, monitoring instruments and threshold limit values for extremely low frequency-magnetic field (ELF-MF) methods. This study was undertaken through brief literature review. We performed a literature search in PubMed to identify ELF-MF studies conducted in workplaces. Initial search keywords such as 'extremely low frequency-magnetic field (ELF-MF)' and 'electromagnetic fields (EMF)' combined or singly. We limited our review to occupational rather than general nonworkplace environmental exposures. Methods: The contents we reviewed: key industry and occupations generating ELF-MF, several direct-reading instruments monitoring ELF-MF and threshold limit values (TLV) preventing health effects may be caused by the exposure to ELF-MF. Results: The industries related to the generation and supply of electricity, electrolytic installations, welding, and induction heating and more were regarded as high ELF-MF exposure industries. All jobs handling or employed performed in power cable lines, electrical wiring, and electrical equipment are found to be exposed to ELF-MF. Threshold or ceiling limit, 1,000 µT, is established to prevent acute effects of exposure to low-frequency EMFs on the nervous system: the direct stimulation of nerve and muscle tissues and the induction of retinal phosphenes. The International Agency for Research on Cancer (IARC) has classified ELF-MF as possibly carcinogenic to humans chiefly based on epidemiological studies on childhood leukemia. However, a causal relationship between magnetic fields and several types of cancer including childhood leukemia has not been established nor has any other long-term effects. Risk management using precautionary measures, has been initiated by the US and EU to prevent chronic health effects related to ELF-MF exposure in workplaces. Conclusion: This study recommends the implementation of various measures such as theestablishment of occupational exposure limit values for ELF-MF and precautionary principle to prevent potential chronic occupational health effects may be caused by ELF-MF in Korea.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.3A
• /
• pp.297-307
• /
• 2010

Recently, maintenance engineering and technology for civil and building structures have begun to draw big attention and actually the number of structures that need to be evaluate on structural safety due to deterioration and performance degradation of structures are rapidly increasing. When stiffness is decreased because of deterioration of structures and member cracks, dynamic characteristics of structures would be changed. And it is important that the damaged areas and extent of the damage are correctly evaluated by analyzing dynamic characteristics from the actual behavior of a structure. In general, typical measurement instruments used for structure monitoring are dynamic instruments. Existing dynamic instruments are not easy to obtain reliable data when the cable connecting measurement sensors and device is long, and have uneconomical for 1 to 1 connection process between each sensor and instrument. Therefore, a method without attaching sensors to measure vibration at a long range is required. The representative applicable non-contact methods to measure the vibration of structures are laser doppler effect, a method using GPS, and image processing technique. The method using laser doppler effect shows relatively high accuracy but uneconomical while the method using GPS requires expensive equipment, and has its signal's own error and limited speed of sampling rate. But the method using image signal is simple and economical, and is proper to get vibration of inaccessible structures and dynamic characteristics. Image signals of camera instead of sensors had been recently used by many researchers. But the existing method, which records a point of a target attached on a structure and then measures vibration using image processing technique, could have relatively the limited objects of measurement. Therefore, this study conducted shaking table test and field load test to verify the validity of the method that can measure multi-point displacement responses of structures using image processing technique.

• Journal of the Society of Disaster Information
• /
• v.10 no.4
• /
• pp.583-597
• /
• 2014

Fire caused by heater has various causes as many as the types of heater. also, lots of damage of human life and property loss are caused, since annually continuous fire accident by heater in traditional market is frequently occurring. There are not many cases of fire due to heater in most of residential facilities such as general house, apartments, etc., because they are supplied with heating boiler, however the restaurant, store and office of the market, sports center, factory, workplace, etc. still use heater, e.g. oilstove, electric heater, etc., so that they are exposed to fire hazard. Also, when investigating the number of fire due to heater, it was analyzed to occur in order of home boiler, charcoal stove, oilstove, gas heater/stove, electric stove/heater, the number of fire per human life damage was analyzed in order of gas heater/stove, oil heater/stove, electric heater/stove, briquette/coal heater. Also, gas and oil related heater were analyzed to have low frequency, however, with high fire intensity. Therefore, this research aimed at considering more scientific fire inspection and identification approach by reenacting and reviewing fire outbreak possibility caused by combustibles' contact and conductivity under the normal condition and abnormal condition in respect of ignition hazard, i.e. minimum ignition temperature, carbonization degree and heat flux along with it, due to oilstove and electric stove, which are still frequently used in public use facility, traditional market, and, of which actual fire occurrence is the most frequent. As the result of reenact test, ignition hazard appeared very small, as long as enough heat storage condition is not made in both test objects(oilstove/electric stove), however carbonization condition was analyzed to be proceeded per each part respectively. Eventually, transition to fire is the ignition due to heat storage, so that it was analyzed to ignite when minimum heat storage temperature condition of fire place is over $500^{\circ}C$. Particularly, in case of quartz pipe, the heating element of electric stove, it is rapidly heated over the temperature of $600^{\circ}C$ within the shortest time(10sec), so that the heat flux of this appears 6.26kW/m2, which was analyzed to result in damage of thermal PVC cable and second-degree burn in human body. Also, the researcher recognized that the temperature change along with Geometric View Factor and Fire Load, which display decrease of heat, are also important variables to be considered, along with distance change besides temperature condition. Therefore, the researcher considers that a manual of careful fire inspection and identification on this is necessary, also, expects that scientific and rational efforts of this research can contribute to establish manual composition and theoretical basis on henceforth fire inspection and identification.

• Geophysics and Geophysical Exploration
• /
• v.11 no.2
• /
• pp.127-136
• /
• 2008

To identify the potential area of gas hydrate in the Ulleung Basin, 2-D and 3-D seismic surveys using R/V Tamhae II were conducted in 2005 and 2006. Seismic survey equipment consisted of navigation system, recording system, streamer cable and air-gun source. For reliable velocity analysis in a deep sea area where water depths are mostly greater than 1,000 m and the target depth is up to about 500 msec interval below the seafloor, 3-km-long streamer and 1,035 $in^3$ tuned air-gun array were used. During the survey, a suite of quality control operations including source signature analysis, 2-D brute stack, RMS noise analysis and FK analysis were performed. The source signature was calculated to verify its conformity to quality specification and the gun dropout test was carried out to examine signature changes due to a single air gun's failure. From the online quality analysis, we could conclude that the overall data quality was very good even though some seismic data were affected by swell noise, parity error, spike noise and current rip noise. Especially, by checking the result of data quality enhancement using FK filtering and missing trace restoration technique for the 3-D seismic data inevitably contaminated with current rip noises, the acquired data were accepted and the field survey could be conducted continuously. Even in survey areas where the acquired data would be unsuitable for quality specification, the marine seismic survey efficiency could be improved by showing the possibility of noise suppression through onboard data processing.