• The Journal of Korean Academy of Prosthodontics
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• v.40 no.2
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• pp.131-139
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• 2002

There have been many studies about marginal discrepancy of single restorations made by various systems and materials. But many of statistical inferences are not definite because of sample size, measurement number, measuring instruments. etc. The purpose of this study was to compare the marginal adaptations of the anterior single restorations made by different systems and to consider more desirable statistical methods in analysing the marginal fit. The in vitro marginal discrepancies of three different all-ceramic crown systems (Celay In-Ceram. Conventional In-Ceram. IPS Empress 2 layering technique) and one control group (PFM) were evaluated and compared. The crowns were made from one extracted maxillary central incisor prepared with a 1mm shoulder margin and $6^{\circ}$ taper walls by milling machine. 10 crowns per each system were fabricated. Measurements or a crown were recorded at 50 points that were randomly selected for marginal gap evaluation. Non-parametric statistical analysis was performed for the results. Within the limits of this study, the following conclusions were drawn: 1 Mean gap dimensions and standard deviations at the marginal opening for the maxillary incisor crowns were $98.2{\pm}40.6{\mu}m$ for PFM, $83.5{\pm}18.7{\mu}m$ for Celay In-Ceram, $104.9{\pm}44.1{\mu}m$ for conventional In-Ceram, and $45.5{\pm}11.5{\mu}m$ for IPS Empress 2 layering technique. The IPS Empress 2 system showed the smallest marginal gap (P<0.05). The marginal openings of the other three groups were not significantly different (P<0.05). 2 The marginal discrepancies found in this study were all within clinically acceptable standards ($100\sim150{\mu}m$). 3. When the variable is so controlled that the system may be the only one, mean value is interpreted to be the marginal discrepancy of a restoration which is made by each system and standard deviation is to be technique-sensitivity of each one. 4. From the standard deviations. the copy-milling technique (Celay/In-Ceram) was not considered to be technique-sensitive in comparison with other methods. 5. Parametric analysis is more reliable than non-parametric one in interpretation of the mean and standard deviation. The sample size of each group has to be more than 30 to use parametric statistics. The level of clinically acceptable marginal fit has not been established. Further studies are needed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1120-1128
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• 2022

In the event of a marine accident, the longer the exposure time to the sea increases, the faster the chance of survival decreases. However, because the search area of the sea is extremely wide compared to that of land, marine object detection technology based on the sensor mounted on a satellite or an aircraft must be applied rather than ship for an efficient search. The purpose of this study was to rapidly detect an object in the ocean using a hyperspectral image sensor mounted on an aircraft. The image captured by this sensor has a spatial resolution of 8,241 × 1,024, and is a large-capacity data comprising 127 spectra and a resolution of 0.7 m per pixel. In this study, a marine object detection model was developed that combines a seawater identification algorithm using DBSCAN and a density-based land removal algorithm to rapidly analyze large data. When the developed detection model was applied to the hyperspectral image, the performance of analyzing a sea area of about 5 km² within 100 s was confirmed. In addition, to evaluate the detection accuracy of the developed model, hyperspectral images of the Mokpo, Gunsan, and Yeosu regions were taken using an aircraft. As a result, ships in the experimental image could be detected with an accuracy of 90 %. The technology developed in this study is expected to be utilized as important information to support the search and rescue activities of small ships and human life.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.3
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• pp.150-160
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• 1994

Drift gillnet fishery for neon flying squid in the North pacific was one of the major pelagic fisheries of Korea until 1992, its annual catch was 79, 000M/T as average during 1988-1992, but moratoriumed since 1993 according to the decision of UN. Therefore, for the developing of the new fishing gear for the squid, the seven types of rip hook by automatic squid jigging machine were experimented by the korean research vessel Pusan 851 (G/T 1.126, 2.600 PS) in the North Pacific (38 $^{\circ}$30'-43 $^{\circ}$N, 152 $^{\circ}$E-178 $^{\circ}$W) from July 6. 1993 to August 31. 1993. The investigation on catch rate, dropout rate, and catch condition of the rip hooks related to the fishing lamp power for aggregating the squid were carried out during the period. The results obtained are as follows: The composition of catch by automatic squid jigging machine was 83.9% for neon flying squid. 15.5% for boreopacific gonate squid. 0.6% for boreal clubhook squid, and 0.01% for luminous flying squid. The catch rate of neon flying squid was 94.6% in 13.6-18.3$^{\circ}C$ of surface water temperature and 5.4% in others. The higher catch rate of neon flying squid was made in the range 13.6-18.3$^{\circ}C$ of temperature at the surface and about 1$0^{\circ}C$ of temperature at the 100m layer. The CPUE of neon flying squid in the 13.6-18.3$^{\circ}C$ of surface water temperature was ranged 0.8-11.8kg (8.7kg as average). The mantle length and body weight of neon flying squid caught in the experiment were ranged 18.3-51.3 cm, 140-3, 980g and mean mantle length and mean body weight were 29.4cm, 972g respectively. The catch rate of neon flying squid was the highest at dawn with a value of 25.0% of the total catch. The body weight of neon flying squid caught by the D type hooks was 1.7 times more than that of the A type hooks. The dropout rate of neon flying squid caught by the seven types hooks was 7.9-57.5% (19.0% as average), and dropout rate of the D type hooks was 7.9% with 2.7 times decrease than that of the A type hooks. The catch efficiency of small sized neon flying squid in case of using on-off switch method on fishing lamp in 15 minutes intervals was 2.6 times higher than that of the on-switch method with same fishing lamp power.

• Restorative Dentistry and Endodontics
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• v.28 no.3
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• pp.203-208
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• 2003

The purpose of this study was to evaluate the effect of salivary contamination of teeth on bonding efficacy of self-priming and self-etching DBSs. The materials used were Single Bond(SB, self-priming system, 3M), Unifil Bond(UB, self-etching system, GC), and Scotchbond Multi-Purpose Plus(SM, 3M) as control. Forty five human molars randomly allocated to three groups as dentin bonding systems tested and embedded in epoxy resin. Then the specimens were wet-ground to expose flat buccal enamel surface or flat occlusal dentin surface and cut bucco-lingually to form two halves with slow speed diamond saw. One of them was used under non-contamination, other under contamination with saliva. The bonding procedure was according to the manufacturer's directions and resin composite(Z-100, 3M Dental Products, St. Paul, MN) was built-up on the bonded surface 5mm high. The specimens were ground carefully at the enamel-composite interface with fine finishing round diamond bur to create an hour-glass shape yielding bonded surface areas of $1.5{\pm}0.1\textrm{mm}^2$. The specimens were bonded to the modified microtensile testing apparatus with cyanoacrylate, attached to the universal testing machine and stressed in tension at a CHS of 1mm/min. The tensile force at failure was recorded and converted to a tensile stress(MPa). Mean values and standard deviations of the bond strength are listed in table. One-way ANOVA was used to determine significant difference at the 95% level. The bond strength of SBMP and SB were not affected by salivary contamination, but that of UB was significantly affected by salivary contamination. These results indicate that DBSs with total etch technique seems less likely affected by salivary contamination in bonding procedure.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.441-453
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• 2016

This study aimed to develop a two-component TSL suitable for reducing dust and guaranteeing homogeneous qualities during its spraying. Its performance was evaluated by a series of laboratory and field tests. High ductility of two-component TSL prototypes resulted in increasing their elongation at break even though their tensile strengths were slightly lower than those of one-component powder TSLs. One prototype of the two-component TSLs developed in this study was verified to satisfy every criterion specified by EFNARC (2008). Especially, it increased the average compressive strength of mortar specimens by 50% even when it coated them only with the thickness of 3 mm. From a preliminary spraying test, a spraying machine suitable for the developed TSL prototype was derived and modified. After its field application, dust and rebound generated during its spraying works were found to be very minimal. Its spraying rate was recorded to be approximately $60m^2/hr$. In addition, it showed a very rapid hardening characteristic compared with general sprayable waterproofing membranes.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.1
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• pp.45-53
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• 2001

Recently some studies have shown that low light intensity followed by final cure at high light intensity may result in a smaller marginal gap and may be no negative effect on material properties. The purpose of this study was to evaluate the influence of the initial cure with low intensity on the shear bond strength of dentin and the microhardness of composite resin. Twenty intact bovine teeth were prepared for shear bond strength test and each tooth sectioned to three specimens. The specimens were randomly divided into three groups according to the light intensity and curing time as follows; Group I. $450mmW/cm^2$ 40sec Group II. $300mmW/cm^2$ 20sec and $600mmW/cm^2$ 20sec Gropu III. $250mmW/cm^2$ 20sec and $450mmW/cm^2$ 20sec. Samples of each group were restored with light-cured composite resin after dentin bonding and then the shear bond strength of each specimen were measured using universal testing machine. Ten resin specimens per group were prepared. After 24 hours, the Vickers microhardness value was measured at the top and bottom surfaces. The result are as follows; 1. Mean value of low initial intensity groups(II, III) were higher than the control group(I) in shear bond strength, but no significant difference could be found. 2. No significant difference could be found between three groups in microhardness.

• Korean Journal of Medicinal Crop Science
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• v.5 no.2
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• pp.95-101
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• 1997

This study was conducted to investigate how a labor saving for conventional hand sowing and respond to major agronomic traits under different planting density in 1993 and 1994. Each trial was a randomized block split plot with row spacing as the main plots and hill spacing as subplots. Sowing rate appeared lower in 20 or 25cm hill spacing using machine seeder than in hand sowing. Sowing time required reduced more 121 hours per hectare in 60cm row, 20cm hill spacings using machine seeder than in hand sowing. Increasing row and hill spacings reduced number of seedling stand per unit $area(m^2)$. Both number of pods per plant and grain weight per plant and showed highly increase in wide planting. Best yield obtained in 60cm row, 20cm hill spacing using machine seeder. Accumulative mean air temperature was positively correlated with stem height, number of pods per plant and yield, otherwise accumulative rainfall was negatively correlated with ones. A highly significant negative correlation was showed between number of seedling stand per unit $area(m^2)$ and number of branches, number of pods per plant, grain weight per plant and yield. Yield was positively correlated with number of branches, number of pods per plant and grain weight per plant.

• Fire Science and Engineering
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• v.27 no.1
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• pp.39-45
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• 2013

This study analyzes the explosion hazard of dry cleaning solvent recovery machine in laundry shop in two aspects, i.e. combustible and ignition source, and determines the explosive conditions of this machine by conducting mockup explosion tests repeatedly, varying conditions and using real dry cleaning solvent recovery machines. As to combustibles, two kinds of combustibles used widely in Korea have been selected and tested. The flash points, LEL's, and saturation vapor pressures of those combustibles have been measured, and their explosion specific curves have been drawn, based on the results of the measurements, so that the explosion risks of those materials may be determined, depending on the temperatures. Potential voltages generated from materials for laundry and foreign materials of metals have been assumed to be the ignition sources in this application, and their potential voltages have been measured, depending on temperature, humidity, and antistatic agent, by using real materials for laundry and a potential voltage measuring device. Tests have been conducted, varying the quantities, concentrations, and operating temperatures of materials for laundry. As a result, explosions have not been generated with potential voltages of materials for laundry, but explosions have been observed when applying artificial spark energy of 2.0 mJ.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.2
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• pp.93-99
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• 1986

A longline is made of many snoods with baited hooks which are connected to mainline at constant intervals. Hauling the mainline, removing the unused baits and the hooked fish, and the arrangement of hooks are dependent on mainly manual labour as compared with mechanized other fishing gear in fishing operation. The mechanization for longline operation is needed in order to eliminate the manual handling and to shorten the labour time. The magnetic hook splitting apparatus which consists of the hook separator and the guide leading to storage magazine rail was devised for the mechanization of hauling operation. The experiments were carried out in order to measure the splitting rate of hooks in accordance with the hauling speed of mainline and magnetic flux density of splitting apparatus from February to November, 1985. The splitting rate was $94\%$ for the Alaska pollack (Theragra chalcogramma) hook and $96\%$ for the halibut (Paralichthys olivaceus) hook at the hauling speed 24 m/min and magnetic flux density 482 gauss. The unsplitting of hooks was caused by entangling snood in the mainline and low magnetic flux density. The rate is greater the faster hauling speed and the lower magnetic flux density, with an average of about $6\%$, The magnetic flux density needed to hook splitting becomes increased with the increasing hauling speed. When the practical hauling speed is from 20 to 35m/min, the magnetic flux density is needed from 400 to 850 gauss.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.27 no.2
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• pp.27-47
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• 1997

The purpose of this study was to evaluate the accuracy and usefulness of spiral tomography through the comparison and analysis of SCANORA cross-sectional tomographs and DentaScan computed tomographic images of dry mandibles taken by a SCANORA spiral tomographic machine and a computed tomographic machine. Thirty-one dry mandibles with full or partial edentulous areas were used. To evaluate the possible effect of location in the edentulous area, it was divided into 4 regions of Me (region of mental foramen), MI (the midportion between Me and M2), M2 (the midportion between mental foramen and mandibular foramen) and S (the midportion of the mandibular symphysis). A ZPC column (sized 4 mm x 5 mm) was seated on the edentulous regions of Me, MI, M2 and S using the acrylic stent. Then SCANORA spiral tomography and computed tomography were taken on the edentulous regions which contained the ZPC column. The ZPC columns and cross-sectional images of the mandible were measured in the radiographs by three observers and the differences between the two imaging modalities were analysed. The results were as follows: 1. In comparing the actual measurements of the ZPC column and measurements in the radiographs, the mean error of the DentaScan computed tomography was 0.07 mm in vertical direction and -0.06 mm in horiwntal direction, while the mean error of the SCANORA spiral tomography was 0.06 mm in vertical direction and -0.12 mm in horizontal direction. There was a significant difference between the two radiographic techniques in the horizontal measurement of the ZPC column of the symphysis region (p<0.05). But there was no significant difference in the measurements of other regions (p>0.05). 2. In measurements of the distance from the alveolar crest to the inferior border of the mandible (H), and of the distance from the alveolar crest to the superior border of the mandibular canal (Y), there was no significant difference between the two radiographic techniques (p>0.05). 3. In measurements of the distance from the lingual border of the mandible to the buccal border of the mandible (W), and of the distance from the lingual border of the mandible to the lingual border of the mandibular canal (X), there was a significant difference between the two radiographic techniques in measurements of the midportion between the mental foramen and the mandibular foramen (M2) (p<0.05). But there were no significant differences in measurements of the other regions of symphysis (S), mental foramen (Me), the first one-fourth portion between the mental foramen and the mandibular foramen (M1) (p>0.05). 4. Considering the mean range of measurements between observers, the measurements of SCANORA spiral tomography showed higher value than those of DentaScan computed tomography, except in measurements of symphysis (S). 5. On the detectability of the mandibular canal, there was no significant difference between the two radiographic techniques (p>0.05). In conclusion, SCANORA spiral tomography demonstrated a higher interobserver variance than that of DentaScan computed tomography for implant site measurements in the posterior edentulous area of the mandible. These differences were mainly the result of difficulty in the detection of the border of the mandible in SCANORA spiral tomography. But considering the cost and the radiation exposure, SCANORA spiral tomography can be said to be a relatively good radiographic technique for implant site measurement.