• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.2 s.308
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• pp.40-47
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• 2006

This paper proposes a multitoning method using threshold modulation of MJBNM(Modified Jointly Blue Noise Mask) for banding artifacts reduction. As banding artifacts in multitoning appear as uniform dot distributions around the intermediate output levels, such multitone output results in discontinuity and visually unpleasing patterns in smooth transition regions. Therefore, to reduce these banding artifacts, the proposed method rearranges the dot distribution by introducing pixels in the neighborhood of output levels that occurs banding artifacts. First of all principal cause of banding artifacts are analyzed using mathematical description. Based on this analytical result, a threshold modulation technique of MJBNM which takes account of chrominance error and correlation between channels is applied. The original threshold range of MJBNM is first scaled linearly sot that the minimum and maximum of the scaled range include two pixel more than adjacent two output levels that cover an input value. In an input value is inside the vicinity of any intermediate output levels produce banding artifacts, the output is set to one of neighboring output levels based on the pointwise comparison result according to threshold modulation parameter that determines the dot density and distribution. In this case, adjacent pixels are introduced at the position where the scaled threshold values are located between two output levels and the minimum and maximum threshold values. Otherwise, a conventional multitoning method is applied. As a result, the proposed method effectively decreased the appearance of banding artifacts around the intermediate output levels. To evaluate the quality of the multitone result, HVS-WRMSE according to gray level for gray ramp image and S-CIELAB color difference for color ramp image are compared with other methods.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.131-139
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• 2014

Infra-gravity waves (IGWs) with a period of 1~3 minutes are a factor that directly influences the motion analysis of moored ships inside a harbor and longshore sediment transport analysis. If significant levels of IGWs from far seas are transferred to a harbor and amplified, they may cause downtime of large ships and induce economic loss. In this study, transfer characteristics of the IGWs intruding from outside to inside Pohang New Harbor were analyzed using statistical analysis and transfer function of wave data measured at both outside and inside the harbor for around 5 years. Transfer characteristic analysis was limited to events where IGWs had wave heights above 0.1 m. The wave height distribution of inside the harbor was similar to that of outside the harbor, while the wave period variance of the former was larger than that of the latter. The parameters of the transfer function was optimally estimated according to each event. The estimated average RMS error of the wave height inside the harbor was around 0.013 m. The estimated parameters had a strong correlation with the linear combination information of IGW wave height, period, and direction (R = 0.95). The transfer function suggested in this study can quickly and easily estimate information on IGWs inside the harbor using IGW information predicted beforehand, and is expected to reduce damage due to unexpected restrictions on harbor usage.

• Journal of Korea Water Resources Association
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• v.44 no.2
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• pp.135-144
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• 2011

Direct parameter estimation method is verified with various models based on Neyman-Scott rectangular pulse model (NSRPM). Also, newly modified NSRPM (NMSRPM) that uses normal distribution is developed. Precipitation data observed by Korea Meteorological Administration (KMA) for 47 years is applied for parameter estimation. For model performance verification, we used statistics, wet ratio and precipitation accumulate distribution of precipitation generated. The comparison of statistics indicates that absolute relative error (ARE)s of the results from NSRPM and modified NSRPM (MNSRPM) are increasing on July, August, and September and ARE of NMNSRPM shows 10.11% that is the smallest ARE among the three models. NMNSRPM simulates the characteristics of precipitation statistics well. By comparing the wet ratio, MNSRPM shows the smallest ARE that is 16.35% and by using the graphical analysis, we found that these three models underestimate the wet ratio. The three models show about 2% of ARE of precipitation accumulate probability. Those results show that the three models simulate precipitation accumulate probability well. As the results, it is found that the parameters of NSRPM, MNSRPM and NMNSRPM are able to be estimated by the direct parameter estimation method. From the results listed above, we concluded that the direct parameter estimation is able to be applied to various models based on NSRPM. NMNSRPM shows good performance compared with developed model-NSRPM and MNSRPM and the models based on NSRPM can be developed by the direct parameter estimation method.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.3
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• pp.1-5
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• 2007

This is a succeeding article of J. Korean Optalmic Optics Society vol. 11(2) pp. 121-129(2006) [Research about the distribution of refractive errors in distinction of gender and at age of Kyonggi province's partial area]. The former article showed age-specific distribution of myopia, hyperopia and astigmatism which generally appears in refractive errors. This paper aimed to investigate the change of refractive power and prevalence of refractive errors by age. Total 928 subjects were sampled and their refractive errors were determined using auto refractometer. As the results, change of refractive power of subjects appeared at the age about 40, and suddenly reduced over 46 years resulting in (+)refractive power at their fifties. Relative risks of refractive errors of myopia increased in younger subjects but the risks decreased in older subjects (over 46 years). On the other hand, the risks of hyperopia decreased as the age of subjects increase, but could increase to 0.24 (95% CI: 0.07-0.88) after 36 years. This results showed that presbyopia might progress more early when people were before 40 years.

• Journal of Astronomy and Space Sciences
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• v.24 no.1
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• pp.69-78
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• 2007

The international EARTHSHINE mission is to measure 1% anomaly of the Earth global albedo and total solar irradiance using Amon-Ra instrument around Lagrange point 1. We developed a new ray truing based integrated end-to-end simulation tool that overcomes the shortcomings of the existing end-to-end performance simulation techniques. We then studied the in-orbit radiometric performance of the breadboard Anon-Ra visible channel optical system. The TSI variation and the Earth albedo anomaly, reported elsewhere, were used as the key input variables in the simulation. The output flux at the instrument focal plane confirms that the integrated ray tracing based end-to-end science simulation delivers the correct level of incident power to the Amon-Ra instrument well within the required measurement error budget of better than ${\pm}0.28%$. Using the global angular distribution model (ADM), the incident flux is then used to estimate the Earth global albedo and the TSI variation, confirming the validity of the primary science cases at the L1 halo orbit. These results imply that the integrated end-to-end ray tracing technique, reported here, can serve as an effective and powerful building block of the on-line science analysis tool in support of the international EARTHSHINE mission currently being developed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.434-441
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• 2016

Friction Stir Welding (FSW) is a solid-state joining process involving the frictional heat between the materials and tools. The amount of heat conducted into the workpiece determines the quality of the welded zone. Excessive heat input is the cause of oxides and porosity defects, and insufficient heat input can cause problems, such as tunnel defects. Therefore, analyzing the temperature history and distribution at the center of the Friction Stir Welded zone is very important. In this study, the temperature distribution of the friction stir welding region of an AZ61 magnesium alloy was investigated. To achieve this goal, the temperature and metal flow was predicted using the finite element method. In FE analysis, the welding tool was simplified and the friction condition was optimized. Moreover, the temperature measuring test at the center of the welding region was performed to verify the FE results. In this study, the tool rotation speed was a more dominant factor than the welding speed. In addition, the predicted temperature at the center of the welding region showed good agreement with the measurement results within the error range of 5.4% - 7.7%.

• Korean Journal of Veterinary Service
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• v.39 no.1
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• pp.13-20
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• 2016

This study is aimed to find out distribution status of online-market livestock products by purchasing and examining 120 cases of livestock products (seasoned meat: 17, 33 cases of packaged meat, 23 cases of ground meat, 19 cases of ham, 11 cases of sausage, 4 cases of bacon, 1 case of meat processing, 8 cases of Meat extract processed, and 4 cased of Dry storage of meat) at 17 On-line markets from April to August. 2015. We checked the weight of them first, and carried out ingredients test for each of processed meats. And we performed gene screening test on the products which were labelled 'Hanwoo' to investigate that the products were made of Korean native cattle. we also carried out test of identifying domestic animal species on ham, sausage and ground processed products. After weighing all products, we could know that all of them were delivered more than labelled weight or in allowable error. The result values of test which measured level of preservatives, Nitrite, Volatile Basic Nitrite (VBN), and tar Color by the type of processed meat products were in permissible range or not detected. Also, 17 beefs inspected Korean native cattle gene test were confirmed that they were made by real korean native cattle. But 2 cases of Ham, sausage, and ground processed products had difference between label and goods. In this study, we could make a decision that livestock products, distributed in On-line markets, were safe and expect to make higher degrees of hygiene for livestock products seller. Futhermore, we hoped result of this study could be used by basic data for progressive national policy decisions.

• Journal of Korea Water Resources Association
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• v.51 no.8
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• pp.655-664
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• 2018

The riverbed material survey is to investigate the particle size distribution, specific gravity, porosity, etc. as basic data necessary for river channel plan such as calculation of sediment transport and change of river bed. In principle, the survey spots are 1 km interval in the longitudinal direction of the river and 3 points or more in the 1 cross section. Therefore, depending on longitudinal length of the river to be investigated, the number of surveyed sites is very large, and the time and cost for the investigation are correspondingly required. This study is to compare the particle size analysis method with the volumetric method and the image analysis method in work efficiency and cost and to examine the applicability of the image analysis method. It was confirmed that the diameter of the equivalent circle converted by the image analysis method can be applied to the analysis of bed material particle size. In the gravel stream with a particle size of less than 10 cm and a large shape factor, the analytical result of the bed material by the image analysis method is accurate. However, when the shape factor decreases as the particle size increases, the error increases. In addition, analysis results of the work efficiency and cost of the volume method and the image analysis method showed a reduction of about 80%.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.2
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• pp.22-34
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• 2011

This paper presents the investigation results of a research on how engineers can analyze the economic effect of the ETCS(Electronic Toll Collection System) installed to minimize the vehicle delays on freeway tollgates during toll payments. This research considered this economic effect to occur in the form of vehicle passing time reductions at the ETCS, and the multi-service queuing theory was applied to estimate these values. This research found: 1) When vehicles approaching tollgates show Poisson distribution and the service time of the ETCS shows Exponential distribution, the multi-service queuing theory would be applicable for estimating vehicle passing times at toll-gates, 2) Despite the ETCS placement, exit sections of tollgates give a greater reduction of vehicle passing times than entering sections due to more delays at conventional toll payments, and 3)The ETCS would not guarantee vehicle passing time reductions all the time, because in such a case as many vehicles were queuing at the ETCS, the total delay level for a toll gate would increase greatly. In addition, in order to examine the accuracy of the estimated vehicle passing values, this research compared the values from the multi-service queuing theory with the observed values from a set of field survey values at freeway toll-gates, and found that the two values were in a good agreement with a very low error range of 1-3 seconds per vehicle. Based on this result, the multi-service queuing theory was recommended for practice.

• Progress in Medical Physics
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• v.10 no.1
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• pp.23-32
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• 1999

Combined MRI and Relaxogram approach was introduced as a very useful tool for fat study. The phantoms simulating homogeneous mixture of fat and non-fat environments were measured with spin echo pulse sequence on a 0.15 T whole body imager. From 45 scans, the Tl values were obtained by fitting the data to continuous distribution (CONTIN) of relaxation time. This relaxogram gives broad distributions of relaxation time, which are characterized by a number of peaks with characteristic T1 values. Two distinct peaks in relaxogram were observed and identified as signals from com oil and gelatin gel. This model system can be served as simulating the distribution of fat in muscle. Also the relative ratio of two components, which is proportional to the area under the peak, is estimated and compared to nominal values. Based on the good agreement between two predictions, the values from our proposed method agreed with nominal values within $\pm$7 % error. The effects of different concentration of contrast agent and different region of interest are presented. To optimize total scan times, the minimum required data points and so further reduction in total scan times are discussed.