• The Korean Journal of Nuclear Medicine
• /
• v.38 no.4
• /
• pp.318-324
• /
• 2004

Purpose: Philips GEMINI is a newly introduced whole-body GSO PET/CT scanner. In this study, performance of the scanner including spatial resolution, sensitivity, scatter fraction, noise equivalent count ratio (NECR) was measured utilizing NEMA NU2-2001 standard protocol and compared with performance of LSO, BGO crystal scanner. Methods: GEMINI is composed of the Philips ALLEGRO PET and MX8000 D multi-slice CT scanners. The PET scanner has 28 detector segments which have an array of 29 by 22 GSO crystals ($4{\times}6{\times}20$ mm), covering axial FOV of 18 cm. PET data to measure spatial resolution, sensitivity, scatter fraction, and NECR were acquired in 3D mode according to the NEMA NU2 protocols (coincidence window: 8 ns, energy window: $409[\sim}664$ keV). For the measurement of spatial resolution, images were reconstructed with FBP using ramp filter and an iterative reconstruction algorithm, 3D RAMLA. Data for sensitivity measurement were acquired using NEMA sensitivity phantom filled with F-18 solution and surrounded by $1{\sim}5$ aluminum sleeves after we confirmed that dead time loss did not exceed 1%. To measure NECR and scatter fraction, 1110 MBq of F-18 solution was injected into a NEMA scatter phantom with a length of 70 cm and dynamic scan with 20-min frame duration was acquired for 7 half-lives. Oblique sinograms were collapsed into transaxial slices using single slice rebinning method, and true to background (scatter+random) ratio for each slice and frame was estimated. Scatter fraction was determined by averaging the true to background ratio of last 3 frames in which the dead time loss was below 1%. Results: Transverse and axial resolutions at 1cm radius were (1) 5.3 and 6.5 mm (FBP), (2) 5.1 and 5.9 mm (3D RAMLA). Transverse radial, transverse tangential, and axial resolution at 10 cm were (1) 5.7, 5.7, and 7.0 mm (FBP), (2) 5.4, 5.4, and 6.4 mm (3D RAMLA). Attenuation free values of sensitivity were 3,620 counts/sec/MBq at the center of transaxial FOV and 4,324 counts/sec/MBq at 10 cm offset from the center. Scatter fraction was 40.6%, and peak true count rate and NECR were 88.9 kcps @ 12.9 kBq/mL and 34.3 kcps @ 8.84 kBq/mL. These characteristics are better than that of ECAT EXACT PET scanner with BGO crystal. Conclusion: The results of this field test demonstrate high resolution, sensitivity and count rate performance of the 3D PET/CT scanner with GSO crystal. The data provided here will be useful for the comparative study with other 3D PET/CT scanners using BGO or LSO crystals.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.31 no.2
• /
• pp.142-152
• /
• 1995

The combined bottom trawl and hydroacoustic survey was conducted by using the training ship Oshoro Maru belong to Hokkaido University in November 1989-1992 and the training ship Nagasaki Maru belong to Nagasaki University in April 1994 in the East China Sea, respectively. The aim of the investigations was to collect the target strength data of fish school in relation to the biomass estimation of fish in the survey area. The hydroacoustic survey was performed by using the scientific echo sounder system operating at three frequencies of 25, 50 and 100kHz with a microcomputer-based echo integrator. Fish samples were collected by bottom trawling and during the trawl surveys, the openings of otter board and net mouth were measured. The target strength of fish school was estimated from the relationship between the volume back scattering strength for the depth strata of bottom trawling and the weight per unit volume of trawl catches. A portion of the trawl catches preserved in frozon condition on board, the target strength measurements for the defrosted samples of ten species were conducted in the laboratory tank, and the relationship between target strength and fish weight was examined. In order to investigate the effect of swimbladder on target strength, the volume of the swimbladder of white croaker, Argyrosomus argentatus, sampled by bottom trawling was measured by directly removing the gas in the swimbladder with a syringe on board. The results obtained can be summarized as follows: 1.The relationship between the mean volume back scattering strength (, dB) for the depth strata of trawl hauls and the weight(C, $kg/\textrm{m}^3$) per unit volume of trawl catches were expressed by the following equations : 25kHz : = - 29.8+10Log(C) 50kHz : = - 32.4+10Log(C) 100kHz : = - 31.7+10Log(C) The mean target strength estimates for three frequencies of 25, 50 and 100 kHz derived from these equations were -29.8dB/kg, -32.4dB/kg and -31.7dB/kg, respectively. 2. The relationship between target strength and body weight for the fish samples of ten species collected by trawl surveys were expressed by the following equations : 25kHz : TS = - 34.0+10Log($W^{\frac{2}{3}}$) 100kHz : TS = - 37.8+10Log($W^{\frac{2}{3}}$) The mean target strength estimates for two frequencies of 25 and 100 kHz derived from these equations were -34.0dB/kg, -37.8dB/kg, respectively. 3. The representative target strength values for demersal fish populations of the East China Sea at two frequencies of 25 and 100 kHz were estimated to be -31.4dB/kg, -33.8dB/kg, respectively. 4. The ratio of the equivalent radius of swimbladder to body length of white croaker was 0.089 and the volume of swimbladder was estimated to be approximately 10% of total body volume.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.37 no.3
• /
• pp.163-173
• /
• 2001

The dynamic behavior characteristics of a small fishing crane for inshore and coastal fishing vessels was experimentally analyzed in order to improve the fishing operation and to reduce considerably manual work of fisherman. The small fishing crane was designed to be controlled electro-hydraulically by means of proportional valves and solenoid valves, and also to be controlled the speed of each operation. The dynamic behavior characteristics was investigated by measuring the changes of parameters such as oil pressure, swing angle of load, load tension, the lifting angle and the swing angle of crane arm when the arms extended in a side way was given a test load. The results obtained are summarized as follows: 1. The designed small fishing crane can be proportionally controlled by means of proportional valves and rapidly by operating the solenoid valves, respectively. The capacity, turning angle, maximum reach of crane were 2 T-M, $180^\circ$, 3.7m, respectively. 2. The vertical change of crane arm on the extension of lifting cylinder was $1.2^\circ$/cm, and the swing speed of crane arm due to the extension of swing cylinder by on/off operations of solenoid valves was $15^\circ$/sec, with the swing period of 1.4 sec and the angle fluctuation of $\pm$11.0$^{\circ}$. 3. When changing simultaneously the horizontal and vertical positions of the lifting load by on/off operations of solenoid valves, the swing and lifting speeds of crane arm were $4.46^\circ$/sec and $6.4^\circ$/sec, respectively. 4. The movements of the designed crane were particularly smooth as they are controlled with the aid of proportional valves than by means of solenoid valves.

• Journal of Korean Ophthalmic Optics Society
• /
• v.15 no.2
• /
• pp.145-150
• /
• 2010

Purpose: In this study we investigated the correlation between the effect of myopia correction and the change of corneal eccentricity using reverse geometry lens. Methods: The 23 students (46 eyes) continuously wearing reverse geometry lens during 3 months were divided into Group I and Group II by different parameter fitting methods of wearing Reverse Geometry Lens. We measured a corneal eccentricity for Group I and Group II at $10^{\circ}$, $20^{\circ}$, and $30^{\circ}$ positions from corneal apex before wearing reverse geometry lens, 1 week, 1 month, and 3 months after wearing reverse geometry lens. We also measured an uncorrected visual acuity, a spherical equivalent, and a corneal radius and analyzed the correlation between them and the change of corneal eccentricity using statistical significance test. Results: There were the statistical significances of a change of corneal eccentricity (p=0.03, t=-2.29) for Group I and Group II at 10 position from corneal apex in a week after wearing reverse geometry lens, but were not those (p>0.05) in 1 month, and 3 months after wearing reverse geometry lens. There were the statistical significances of correlation between the change of corneal eccentricity and a corrected visual acuity, and a corneal radius, respectively. Particularly, the high correlation between the change of corneal eccentricity and a corrected visual acuity (r=-0.36, p=0.00, t=6.5), and a spherical equivalent (r=-0.72, p=0.00, t=-70.5) for Group II in a week after wearing reverse geometry lens showed. Conclusions: We knew from these results that the high correlation between the effect of myopia correction and the change of corneal eccentricity in a week after wearing reverse geometry lens represented.

• Journal of the Mineralogical Society of Korea
• /
• v.21 no.1
• /
• pp.37-44
• /
• 2008

This study was performed to synthesize Na-A type zeolite with melting slag from the Mapo incineration site and recycle the zeolite as an environmental remediation agent. The melting slag used had a favorable composition containing 26.6% $SiO_2$, 10.9% $Al_2O_3$ and 2.7% $Na_2O$ for zeolite synthesis although there were high contents of iron oxides, including 19.6% $Fe_2O_3$ and 18.9% FeO, which had been used as a flux for the melting. It was confirmed that the Na-A type zeolite could be successfully synthesized at $80^{\circ}C$ and $SiO_2/Al_2O_3\;=\;0.80{\sim}1.96$. The cation exchange capacities (CEC) of the zeolites was determined to be about 220 cmol/kg leveled off at the synthetic time more than 10hrs. The adsorption capacities of zeolite to heavy metals (Cd, Cu, Mn and Pb) were high except for As arid Cr. It was also confirmed through the Eh and pH analysis that As and Cr existed in the forms of $HAsO_4^{2-}$ and $CrO_4^{2-}$. The low absorption rates of zeolite for As and Cr are attributed to the fact that the pore size ($4\;{\AA}$) of Na-A type is smaller than those of $HAsO_4^{2-}$ and $CrO_4^{2-}$ ions ($4\;{\AA}$ ionic radii and $8\;{\AA}$ diameter).

• Restorative Dentistry and Endodontics
• /
• v.34 no.5
• /
• pp.424-429
• /
• 2009

This study aimed to assess the influence of different cross-sectional area on the cyclic fatigue fracture of Ni-Ti rotary files using a fatigue tester incorporating cyclical axial movement. Six brands of Ni-Ti rotary files (ISO 30 size with. 04 taper) of 10 each were tested: Alpha system (KOMET), HeroShaper (MicroMega), K3 (SybronEndo), Mtwo (VDW), NRT (Mani), and ProFile (Dentsply). A fatigue-tester (Denbotix) was designed to allow cyclic tension and compressive stress on the tip of the instrument. Each file was mounted on a torque controlled motor (Aseptico) using a 1:20 reduction contra-angle and was rotated at 300 rpm with a continuous, 6 mm axial oscillating motion inside an artificial steel canal. The canal had a $60^{\circ}$ angle and a 5 mm radius of curvature. Instrument fracture was visually detected and the time until fracture was recorded by a digital stop watch. The data were analyzed statistically. Fractographic analysis of all fractured surfaces was performed to determine the fracture modes using a scanning electron microscope. Cross-sectional area at 3 mm from the tip of 3 unused Ni-Ti instruments for each group was calculated using Image-Pro Plus (Imagej 1.34n, NIH). Results showed that NRT and ProFile had significantly longer time to fracture compared to the other groups (p < .05). The cross-sectional area was not significantly associated with fatigue resistance. Fractographycally, all fractured surfaces demonstrated a combination of ductile and brittle fracture. In conclusion, there was no significant relationship between fatigue resistance and the cross-sectional area of Ni-Ti instruments under experimental conditions.

• Korean Journal of Environmental Agriculture
• /
• v.38 no.1
• /
• pp.54-60
• /
• 2019

BACKGROUND: Hydrogen fluoride is one of the 97 accident preparedness substances regulated by the Ministry of Environment (Republic of Korea) and chemical accidents should be managed centrally due to continual occurrence. Especially, hydrogen fluoride has a characteristic of rapid diffusion and very toxic when leaking into the environment. Therefore, it is important to predict the impact range quickly and to evaluate the residual contamination immediately to minimize the human and environmental damages. METHODS AND RESULTS: In order to estimate the accident impact range, the off-site consequence analysis (OCA) was performed to the worst and alternative scenarios. Also, in order to evaluate the residual contamination of hydrogen fluoride in crop, the samples in accident site were collected from 15-divided regions (East direction from accident sites based on the main wind direction), and the concentration was measured by fluoride ($F^-$) ion-selective electrode potentiometer (ISE). As a result of the OCA, the affected distance by the worst scenario was estimated to be >10 km from the accident site and the range by the alternative scenario was estimated to be about 1.9 km. The residual contamination of hydrogen fluoride was highest in the samples near the site of the accident (E-1, 276.82 mg/kg) and tended to decrease as it moved eastward. Meanwhile, the concentrations from SE and NE (4.96~28.98 mg/kg) tended to be lower than the samples near the accident site. As a result, the concentration of hydrogen fluoride was reduced to a low concentration within 2 km from the accident site (<5 mg/kg), and the actual damage range was estimated to be around 2.2 km. Therefore, it is suggested that the results are similar to those of alternative accident scenarios calculated by OCA (about 1.9 km). CONCLUSION: It is difficult to estimate the chemical accident-affecting range/region by the OCA evaluation, because it is not possible to input all physicochemical parameters. However simultaneous measurement of the residual contamination in the environment will be very helpful in determining the diffusion range of actual chemical accident.

• Journal of Wetlands Research
• /
• v.25 no.4
• /
• pp.306-314
• /
• 2023

Stream sediments are an important component of water quality management because they are receptors of various pollutants such as heavy metals and organic matters emitted from upland sources and can be secondary pollution sources, adversely affecting water environment. To effectively manage the stream sediments, identification of primary sources of sediment contamination and source-associated control strategies will be required. We evaluated the performance of machine learning models in identifying primary sources of sediment contamination based on the physico-chemical properties of stream sediments. A total of 356 stream sediment data sets of 18 quality parameters including 10 heavy metal species(Cd, Cu, Pb, Ni, As, Zn, Cr, Hg, Li, and Al), 3 soil parameters(clay, silt, and sand fractions), and 5 water quality parameters(water content, loss on ignition, total organic carbon, total nitrogen, and total phosphorous) were collected near abandoned metal mines and industrial complexes across the four major river basins in Korea. Two machine learning algorithms, linear discriminant analysis (LDA) and support vector machine (SVM) classifiers were used to classify the sediments into four cases of different combinations of the sampling period and locations (i.e., mine in dry season, mine in wet season, industrial complex in dry season, and　industrial complex in wet season). Both models showed good performance in the classification, with SVM outperformed LDA; the accuracy values of LDA and SVM were 79.5% and 88.1%, respectively. An SVM ensemble model was used for multi-label classification of the multiple contamination sources inlcuding landuses in the upland areas within 1 km radius from the sampling sites. The results showed that the multi-label classifier was comparable performance with sinlgle-label SVM in classifying mines and industrial complexes, but was less accurate in classifying dominant land uses (50~60%). The poor performance of the multi-label SVM is likely due to the overfitting caused by small data sets compared to the complexity of the model. A larger data set might increase the performance of the machine learning models in identifying contamination sources.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.2
• /
• pp.193-204
• /
• 1998

The single crystal of the $LiTaO_3$has large electro-optic effects, so it is applied to optical switch, acousto-optic deflector, and optical memory device as hologram using photorefractive effect. In this study, optic-grade undoped $LiTaO_3$and Fe:LiTaO$LiTaO_3$single crystals were grown by the Czochralski method and optical transmission and absorption spectrums were measured in the wavelength of UV-VIS range. The curie temperature was determined with DSC and by measuring capacitance for the grown undoped crystal and ceramic powder samples of various Li/Ta ratio. In case of having a 48.6 mol% $Li_2O$ as a starting Li/Ta ratio, the results of concentration variations were below 0.01 mol% $Li_2O$ all over the crystal, so it was confirmed that $LiTaO_3$single crystals were grown under congruent melting composition having optical homogeneity. The curie temperature of the Fe:$LiTaO_3$crystal was increased with increased with increased doped Fe concentrations;by the ratio of $7.5^{\circ}C$ increase per Fe 0.1 wt%. Also, the optical transmittance was about 78 %, which was sufficient for optical device.

• Journal of Korean Ophthalmic Optics Society
• /
• v.13 no.4
• /
• pp.65-73
• /
• 2008

Purpose: The purpose of this study is to investigate the effect of age in the response to long-term overnight orthokeratology (OK) lens wearing. Methods: Among volunteers, ninety-five healthy subjects who had no eye diseases and could wear OK contact lens at least for 8 hours every day were divided into three groups children, youngsters and young adults. Unaided logMAR visual acuity, refractive error, apical corneal radius, corneal asphericity and central corneal thickness were measured with different period; before and after one day, one week, two weeks, one month, three months and six months of OK lens wear. Paired student t-test, ANOVA analysis and Pearson correlation were used with a critical p value of 0.05 for statistical analysis. Results: All groups showed statistically significant (p<0.001) improvement in unaided visual acuity, a trend for flattening in the apical corneal radius, decrease in central corneal thickness and less prolate after OK lens wear. The child group showed significantly rapid change (p<0.001) in visual acuity, and apical corneal radius showed that they reached the targeted refractive change earlier compared with youngster and adult groups. The visual effect of OK lens was significantly related with the change in central corneal thickness after long-term OK lens wear, especially in child and youngster group, and central corneal thickness were highly correlated with the targeted refractive change. Conclusions: Visual acuity change is statistically correlated with the central corneal thickness change, which is highly correlated with targeted refractive change in the long-term orthokeratology and younger lens wearers showed a rapid response to OK lens wear, suggesting a reduced epithelial response with increasing age. The results found this study extends our understanding and development in the long-term orthokeratology.