• Korean Security Journal
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• no.31
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• pp.25-45
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• 2012

Based on the results of preceding researches that the uncertainty perceived by the private security guards about their roles exerts direct effects on the business performance of the security industry, it needs to preferentially examine the degree of authority that the private security guards have. The suitability of the psychological empowerment criteria for measuring this for private security guards, however, has not yet been established up to the present, so it can be said that the validity of the information has not yet been established. Accordingly, as the psychological empowerment criteria of private security guards, this research examined the suitability of items, reliability of items, the level of difficulty of items, and the item goodness of fit from the viewpoint of the appropriateness of category of responses, and it is summarized as follows. First, in the self-determinism factor of the psychological empowerment criteria, Item 11 was found to be an unsuitable item, so it is proper that Item 11 should be deleted when examining the psychological empowerment of private security guards from now on. Second, the item reliability of the psychological empowerment criteria was high, so the consistency of the results is shown even if the data are collected from the other private security guards. Third, they feel that it is hard to respond to Item 12 while they perceive that Item 1 is the easiest, and the level of items of the psychological empowerment criteria is evenly distributed. Fourth, it was established that the 5-point categories of the psychological empowerment criteria were suitable to the private security guards.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.82-82
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• 2010

We measure the topology of the galaxy distribution using the Seventh Data Release of the Sloan Digital Sky Survey (SDSS DR7), examining the dependence of galaxy clustering topology on galaxy properties. The observational results are used to test galaxy formation models. A volume-limited sample defined by Mr<-20.19 enables us to measure the genus curve with amplitude of G=378 at 6h-1Mpc smoothing scale, with 4.8% uncertainty including all systematics and cosmic variance. The clustering topology over the smoothing length interval from 6 to 10h-1Mpc reveals a mild scale-dependence for the shift and void abundance (A_V) parameters of the genus curve. We find strong bias in the topology of galaxy clustering with respect to the predicted topology of the matter distribution, which is also scale-dependent. The luminosity dependence of galaxy clustering topology discovered by Park et al. (2005) is confirmed: the distribution of relatively brighter galaxies shows a greater prevalence of isolated clusters and more percolated voids. We find that galaxy clustering topology depends also on morphology and color. Even though early (late)-type galaxies show topology similar to that of red (blue) galaxies, the morphology dependence of topology is not identical to the color dependence. In particular, the void abundance parameter A_V depends on morphology more strongly than on color. We test five galaxy assignment schemes applied to cosmological N-body simulations to generate mock galaxies: the Halo-Galaxy one-to-one Correspondence (HGC) model, the Halo Occupation Distribution (HOD) model, and three implementations of Semi-Analytic Models (SAMs). None of the models reproduces all aspects of the observed clustering topology; the deviations vary from one model to another but include statistically significant discrepancies in the abundance of isolated voids or isolated clusters and the amplitude and overall shift of the genus curve. SAM predictions of the topology color-dependence are usually correct in sign but incorrect in magnitude.

• Journal of Radiation Protection and Research
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• v.45 no.2
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• pp.76-80
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• 2020

Background: To improve the measurement accuracy of liquid-scintillation counting for activity standardization, it is necessary to significantly reduce the background caused by thermal noise or after-pulses. We have therefore improved a movable 3 photomultiplier (3PM)-γ coincidence-counting method using the logical sum of three double coincidences for β events. Materials and Methods: We designed a new data-acquisition system in which β events are obtained by counting the logical sum of three double coincidences. The change in β-detection efficiency can be derived by moving three photomultiplier tubes sequentially from the liquid-scintillation vial. The validity of the method was investigated by activity measurement of ¹³⁴Cs calibrated at the Korea Research Institute of Standards and Science (KRISS) with 4π(PC)β-γ(NaI(Tl)) coincidence counting using a proportional counter (PC) for the β detector. Results and Discussion: Measurements were taken over 14 counting intervals for each liquidscintillation sample by displacing three photomultiplier tubes up to 45 mm from the sample. The dead time in each β- and γ-counting channel was adjusted to be a non-extending type of 20 ㎲. The background ranged about 1.2-3.3 s^-1, such that the contributions of thermal noise or after-pulses were negligible. As the β-detection unit was moved away from the sample, the β-detection efficiencies varied between 0.54 and 0.81. The result obtained by the method at the reference date was 396.3 ± 1.7 kBq/g. This is consistent with the KRISS-certified value of 396.0 ± 2.0 kBq/g within the uncertainty range. Conclusion: The movable 3PM-γ method developed in the present work not only succeeded in reducing background counts to negligible levels but enabled β-detection efficiency to be varied by a geometrical method to apply the efficiency extrapolation method. Compared with our earlier work shown in the study of Hwang et al. [2], the measurement accuracy has much improved. Consequently, the method developed in this study is an improved method suitable for activity standardization of β-γ emitters.

• Journal of Korean Society of Forest Science
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• v.106 no.2
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• pp.111-120
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• 2017

The best source of information on the conservation status of species at a global scale is the IUCN Red List of Threatened Species. Until now, 236 vascular plants from Korean peninsula have been evaluated using the IUCN red list categories and criteria. It indicated that five taxa were considered as critically endangered, 20 as endangered and nine as vulnerable species as a threatened status. On the other hand, the rest (189 taxa) were assessed as a least concern, which did not qualify for threatened species categories. Korea Ministry of Environment published a revised version of 57 species list by re-classifying endangered species with idiosyncratic qualitative criteria for two levels (I and II) followed by status reviews in 2011. However, two thirds species proposed by Ministry of Environment do not qualify as threatened. The major difficulties found in applying IUCN Red List criteria at the global scale was a lack of knowledge on the status of species at broader geographic scales and the perceived difficulty the causes. The lack of consistency between two lists constrains the prioritization of species-based conservation work at the national level. Due to a lack of centralized monitoring data for most species, this status is largely qualitatively and so it carries a high level of uncertainty. This is reflected in the high number of species with an unknown population trend. The current list of endangered species of flora and fauna by the Ministry of Environment should be recognized as the national list (local and population extinction), which is different from the IUCN Red list due to the different geographical contexts. Also, it is necessary to improve the quality of evaluation and conservation management system rather than presenting massive number of endangered species list.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1039-1049
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• 2015

The inflow estimation at large multipurpose dam reservoir is carried out by considering the water balance among the discharge, the storage change during unit time interval obtained from the observed water level near dam structure and area-volume curve. This method can be ideal for level pool reservoir but include potential errors when the inflow is influenced by the water level slope due to backwater effects from upstream flood inflows and strong wind induced by typhoon. In addition, the other uncertainties arisen from the storage reduction due to sedimentation after the dam construction and water level noise due to mechanical vibration transmitted from the electric power generator. These uncertainties impedes the accurate hydraulic inflow measurement requiring exquisite hydrometric data arrangement for reservoir waterbody. In this study, the distributed hydrologic model using UBC-3P boundary setting was applied and its feasibility was evaluated. Finally, the modeling performance has been verified since the calculated determination coefficient has been in between 0.96 to 0.99 after comparing with observed peak inflow and total inflow at Namgang dam reservoir.

• Progress in Medical Physics
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• v.16 no.3
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• pp.116-124
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• 2005

Absorbed dose dosimetry protocols of high energy photon and electron beams, which are widely used and based on an air kerma calibration factors, have somewhat complex formalism and limitations for improving dosimetric accuracy due to uncertainty of the physical parameters used. Recently the IAEA and the AAPM published the absorbed dose to water-based dosimetry protocol. In this work web-based dose calibration program for IAEA TRS-398 and AAPM TG-51 protocols were developed. This program developed using the Visual C$\#$ language can be used in the internet. User selectable dosimetry protocol on the web allows the absorbed dose to water data of the two protocols at a reference point to be easily compared, and enables to conveniently manage and understand the current status of the dosimetry calibration performed at participating institutions in korea. This program and the resultant database from the web-based calibration can be useful in developing new dosimetry protocols in Korea.

• Progress in Medical Physics
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• v.9 no.4
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• pp.259-266
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• 1998

To achieve the 2D dose distribution around the designed high dose rate Ir-192 source substitution for Co-60 brachytherapy source, we determined the exposure rate constant and tissue attenuation factors as a large depth as a 20 cm from source center. The exposure rate constant is used for apparent activity in designed source with self-absorption and encapsulation steel wall. The tissue dose delivered from the 4401 segments of 2.5 mm in a diameter and 2.5 mm height of disk-type source layer. In the experiments, the tissue attenuation factors include the tissue attenuation and multiple scattering in a medium surrounding the source. The fitted the polynomial regression with 4th order for the tissue attenuation factors are very closed to the experimental measurement data within ${\pm}$1% discrepancy. The Meisberger's constant showed the large uncertainty in large distance from source. The exposure rate constant 4.69 Rcm$^2$/mCi-hr was currently used for determination of apparent activity of source and air kerma strength was obtained 0.973 for tissue absorbed dose from the energy spectrum of Ir-192 source. In our experiments with designed high dose rate brachytherapy source, the apparent activity of Ir-192 source was delivered from the 54.6 % of actual physical source activity through the self-absorption and encapsulation wall attenuations. This paper provides the 2-dimensional dose tabulation from unit apparent activity in a water medium for dose planning includes the multiple scattering, source anisotropy effect and geometric factors.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.1
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• pp.81-87
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• 2010

The coverage ability is one of essential techniques for the Robotic Vacuum Cleaner (RVC). Most of the RVCs rely on random or regular pattern movement to cover a target space due to the technical difficulties to implement localization and map and constraints of hardwares such as controller and sensors. In this paper, we consider two main issues which are low computational load and using sensors with very limited sensing capabilities. First, in our approach, computing procedures to build map and detect the RVC's position are minimized by simplifying data obtained from sensors. To reduce computational load, it needs simply presenting an environment with objects of various shapes. Another isuue mentioned above is regarded as one of the most important problems in our approach, because we consider that many RVCs use low-cost sensor systems such as an infrared sensor or ultrasonic sensor with limited capabilities in limited range, detection uncertainty, measurement noise, etc. Methods presented in this paper are able to apply to general RVCs equipped with these sensors. By both simulation and real experiment, we evaluate our method and verify that the proposed method guarantees a complete coverage.

• The Korean Journal of Community Living Science
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• v.20 no.3
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• pp.397-411
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• 2009

The use of local product foods and fresh-cut products, the dietitian's recognition, the required items and the quality for school foodservice was investigated to increase the consumption of high-quality agricultural products. Data from 578 elementary schools, 228 middle schools and 116 high schools were collected by school foodservice personnels in each regional Education Administration in Gyeong-gi province. The first criteria of buying food materials was reliability/safety for all school foodservice. The second criteria were the origin of the product and freshness/ripeness for elementary and middle schools and high school, respectively. The most important consideration for selecting a supplier was the quality of the material. The appearance/status of the food was the first factor for buying food materials. The origin and the seasonality were very important for buying farm products. Dietitians in Gyeong-gi province recognized the local products, and used them weekly. The advantages of using local products were the quick supply, freshness and safety. On the other hand, the disadvantages were the lack of information and the uncertainty of supply. Sixty eight percent of the subjects had experienced the high-quality agricultural products in school meals, but the frequency was low. The main reasons for not servicing high-quality agricultural products were the high cost and the lack of trust on the quality. Among fresh-cut products, seasonings and root vegetables were purchased most frequently, but leaf vegetables was 5.7% only. The purchase of fresh-cut products was not frequent, but usually satisfied. The advantages of fresh-cut products were the reduced workload and waste, but the reason for not using them were poor hygiene and the high price. The diverse supply system and the promotion of the local product foods would be necessary since the most food materials were purchased through suppliers. In addition, the problems related to the high cost and distrust should be resolved to expand the consumption of the high-quality agricultural products and the fresh-cut vegetables. The institutions for certifying the quality should be needed to increase the confidence of these products.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.3
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• pp.599-606
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• 2015

Damage of landslide due to earthquake covers a considerable part of total damage due to earthquake. Landslide due to earthquake affects direct damage of human lives and structures, and social system can be paralyzed by losing functions of roads, basic industries, and so on. Therefore, systematic and specialized research examining the factors affecting the slope stability by earthquakes should be needed. However, method of evaluation of slope stability problems due to earthquake contains somewhat uncertainty since many soil properties are predicted or assumed. In this study, influences of change of soil properties such as degree of saturation and cohesion value are analyzed in factor of safety and displacement using seismic landslide hazard maps based on GIS. As the degree of saturation increases or cohesion decreases, it is found that seismic landslide hazard area marked with factors of safety or displacements tends to increase. Therefore, to draw more exact landslide hazard map during earthquake, it is necessary to obtain accurate soil property information preferentially from site investigation data in the field.