• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.1
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• pp.25-34
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• 1976

The purpose of the present study on the radula of Korean marine gastropods is to determine the systematic position of the species by the radula features. The radula features of 9 Families based on the observation of specimens consisting of 31 species are described briefly as follows. 1. Naticidae; Radula formula 2-1-C-1-2. Rachidian is 3-cusped. All cusps are strong and pointed. The lateral tooth is massive and strong with a huge triangula cusp. Two marginal teethare slender, long and strong. 2. Cymatidae; Radula formula 2-1-c-1-2. Fachidian, 1-cusped. Cusp is strong and acute. The basal margin is toothed with a number of small denticles. The lateral tooth is beak-like and strong with groove inside. The marginal teeth are slender and pointed. 3. Tonnidae; Radula Formula 2-1-C-1-2. Rachidian, 3 cusped. Central cusp is huge, strong and abruptly pointed. Lateral cusp is blunt and relatively small. The lateral tooth and maginal teeth are identical to that of the preceding one. 4. Muricidae; Radula formula 1-C-1. Rachidian has 3 to 5 cusps. Central cusp, long, thick, strong and pointed. Lateral cusps are rather shorter than central, thick, strong and well cut with several minute denticles along outer margin. The lateral tooth is falciform. 5. Pyrenidae; Radula formula 1-c-1 Rachidian lacks of cusp. The base is thin, narrow, small and rectangular. Lateral tooth has 2 cusps with a crescent shaped base. 6. Buccinidae; Radula formula 1-C-1. Rachidian has 3 to 7 cusps. The base is massive and broadened laterally. The lateral tooth is large-and has 2 to 4 cusps. The central cusp is the shortest, and become longer towards the each side. 7. Busyconidae ; Radula formula 1-C-1. Rachidian, 3-cusped with a massive base. All cusps are pointed and strong. Centeral cusp is rather shorter than lateral one. Lateral tooth, 2-cusped. Inner cusp short about one half the length of outer one. 8. Fasciolariidae; Radula formula 1-C-1. Rachidian, 3 to 4-cusped. Very small in size. Lateral tooth broadened laterally with about 10 thin, long, sharp cusps. 9. Volutidae ; Only the rachidian exists. Rachidian, 3-cusped. All cusps are strong and sharply pointed. Central cusp is narrower than lateral ones. Anterior basal margin is concave.

• The korean journal of orthodontics
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• v.29 no.4 s.75
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• pp.491-501
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• 1999

Precise and accurate measuring of tooth size is essential procedure in orthodontic diagnosis. The purpose of this study was to evaluate the reproducibility and accuracy of tooth size measurements with regard to tooth and investigator. Five investigators measured the size of one side of teeth, from central incisor to first molar, on 20 sets of casts that show a moderate degree of crowding. Mesio-distal width was measured with digital vernier calipers in each tooth and this procedure was repeated three times at two weeks interval. To obtain a standard measurement for each tooth, dental casts were cut into individual tooth, and its width was measured with micrometer. The difference between the measurement from dental cast and the standard measurement was defined as the measurement error. Through various statistical analyses, following results were obtained. 1. The reproducibility did not show significant differences with regard to tooth or investigator. 2. The measurement error showed some difference with regard to tooth and investigator. 3. The magnitude of the measurement error showed increasing tendency from anterior to posterior teeth with maximum value in the first molar. 4. While the measurements obtained on study casts generally showed smaller number compared to standard measurements, the direction of the difference showed variability according to tooth or investigator. 5. The measurement errors did not show significant correlations with the degree of crowding. The results of the present study indicate that the possibility of tooth size measurement error should be taken into consideration when diagnosing an orthodontic case.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1229-1238
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• 2005

OFDM(Orthogonal Frequency Division Multiplexing) communications system is very attractive for the high data rate wireless transmission. However, it may be distorted in the nonlinear HPA(High Power Amplifier) since OFDM signal has hish PAPR(Peak-to-Average Power Ratio). In this paper, a new method using control tone is studied for reducing the PAPR and we call it PCT(PAPR Control Tone) method. This proposed PCT method is to assign control tones for PAPR reduction at the predefined sub-carriers. After IFFT(Inverse Fast Fourier Transform) and PAPR calculation, the OFDM data signal of the lowest PAPR is selected to transmit. Unlike the conventional method, it can cut down the computational complexity because it does not require the transmission and demodulation process of side information about the phase rotation. Furthermore, if this method is made up in parallel configuration, it can solve the time delay problem so that it can be processed in real time processing. This proposed method is compared with the conventional selected mapping(SLM) technique. We find out the PAPR reduction performance and BER when the number of control tone is 6 and nonlinear HPA is considered.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.731-740
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• 2008

This paper deals with the fatigue behavior and strength of a new-type of steel-concrete composite bridge deck. The new-type composite bridge deck consists of corrugated steel plate, welded T-beams, stud-type shear connectors and reinforced concrete filler. A total of eight composite bridge deck specimens were fabricated, the fatigue tests were conducted under four-point bending test with three different stress ranges in constant amplitude. According to the test results, the fatigue crack generated at the welding part of the corrugated steel plate, progressed down to the bottom of the steel plate and encountered the crack, which came out from the opposite side at the same position. After the two cracks were connected at the bottom of the steel plate, the lower flange was cut off and the fatigue crack developed up to the T-beam. And the displacements and strains of fatigue test specimens were increasing with cyclic loading number, these were changed sharply at the fatigue failure. The fatigue results are compared with the design S-N curves specified in the Korea Highway Bridge Design Specifications and data in NCHRP 102 and NCHRP 147 report. The new-type composite bridge deck has a stress category of C, which means that new-type composite bridge deck can be designed by the current fatigue design specifications provided for steel members.

• Journal of Biosystems Engineering
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• v.43 no.3
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• pp.237-246
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• 2018

Purpose: This study (a) investigated the effect of microwave power intensity and sample thickness on microwave drying characteristics of radish strips, and (b) determined the best-fit drying model for describing experimental drying data, effective moisture diffusivity ($D_{eff}$), and activation energy ($E_a$) for all drying conditions. Methods: A domestic microwave oven was modified for microwave drying and equipped with a small fan installed on the left upper side for removing water vapor during the drying process. Radishes were cut into two fixed-size strip shapes (6 and 9 mm in thickness). For drying experiments, the applied microwave power intensities ranged from 180 to 630 W at intervals of 90 W. Six drying models were evaluated to delineate the experimental drying curves of both radish strip samples. The effective moisture diffusivity ($D_{eff}$) was determined from Fick's diffusion method, and the Arrhenius equation was applied to calculate the activation energy ($E_a$). Results: The drying time was profoundly decreased as the microwave power intensity was increased regardless of the thickness of the radish strips; however, the drying rate of thicker strips was faster than that of the thinner strips up to a certain moisture content of the strip samples. The majority of the applied drying models were suitable to describe the drying characteristics of the radish strips for all drying conditions. Among the drying models, based on the model indices, the best model was the Page model. The range of estimated $D_{eff}$ for both strip samples was from $2.907{\times}10^{-9}$ to $1.215{\times}10^{-8}m^2/s$. $E_a$ for the 6- and 9-mm strips was 3.537 and 3.179 W/g, respectively. Conclusions: The microwave drying characteristics varied depending on the microwave power intensity and the thickness of the strips. In order to produce high-quality dried radish strips, the microwave power intensity should be lower than 180 W.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1239-1247
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• 2003

OFDM(orthogonal frequency division multiplexing) communications system is very attractive for the high data rate transmission in the frequency selective lading channel. Since OFDM has high PAPR(peak-to-average power ratio), OFDM signal may be distorted by the nonlinear HPA(high power amplifier). In this paper, we propose the DSI(dummy sequence insertion) method for OFDM communication system. Some sub-carriers are inserted for PAPR reduction. They carry the specified dummy data sequence which are used for only PAPR reduction and do not work as side information like the conventional PTS(partial transmit sequence) or SLM(selected mapping) method. We use the complementary sequence and the combination of the correlation sequence as the dummy sequence. Flipping technique is used for the DSI method to get the effective PAPR reduction. It is important that BER of the proposed method is independent of the damage of the dummy data sequence. And DSI method has better spectral efficiency than the conventional block coding. On the other hand, threshold PAPR method is applied to cut down the processing time. However, this DSI method is not better than the conventional PTS method in the respect of the PAPR reduction performance. The DSI method includes the threshold PAPR lower than the PAPR of the OFDM signal, reduces the processing time and improves the BER performance.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.10
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• pp.1009-1015
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• 2006

The elcetrodewatering filter press(EDFP) which had anode and cathod plates to be set between filter plates was built for reducing the waterworks sludge and improving performance of dewatering equipment. Several tests to compare the dewaterability with conventional mechanical filter press dewatering(MDEP) and EDFP was conducted through this equipment. As test results, filtration amount discharged from EDFP measured 43.2 kg which increased against MDFP, and cake weight measured 4 kg which was two times against MDFP. The water content of dewatered cake from EDFP was 55wt% and dewatering velocity was 2.3 $kg/m^2{\cdot}cycle$. This water content decrease 20% and dewatering velocity increased 30% with compare to the MDFP. That is to say, EDFP constructed from electrodewatering mechanism increase filtrate discharging amount, which make dewatering velocity increase and produce the low water content dewatered cake against MDFP. Energy consumption of EDFP is analysed to 400 kwh/DS ton. The results to analysis the economical aspect considering the power consumption and the handling cost decline as sludge volume reduction due to producing the low water content cake showed that expenses to handle sludge of 1 ton by dry solid base cut down on 20,000 won. If considering several test aspects, it was analysed that EDFP was excellent in the side of performance as well as economical suitability.

• Journal of Periodontal and Implant Science
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• v.31 no.3
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• pp.581-595
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• 2001

In performing implant procedures in the anterior portion of the maxilla, many difficulties exist because of anatomical reasons, such as the proximity of the nasal floor, lateral extension of the incisive canal, and labial concavity. On the other hand, in the posterior region of the maxilla, there is often insufficient recipient bone between the maxillary sinus and alveolar ridge due to alveolar ridge resorption and pneumatization of the maxillary sinus. In order to perform implants in such regions, ridge augmentation procedures such as onlay bone graft, guided bone regeneration, and maxillary sinus grafting are performed. In studies of Caucasians, use of autograft from mandibular symphysis has been reported to be highly successful in maxillary sinus grafting. However, in a clinical study of Koreans, autograft of mandibular symphysis has been reported to have significantly low success rate. It has been hypothesized that this is because of insufficient cancellous bone due to thick cortical bone. In order to test this hypothesis, bone quality and morphology of Koreans can be compared with those of Caucasians. In this study, the bone density and morphology of the cortical bone and cancellous bone in the mandibular symphysis of 35 Korean cadavers were evaluated. The following results were obtained: 1. In terms of bone density, type I, type II, and type III consisted of 1.4%(3/213), 72.3%(154/213), and 26.3%(56/213) of the cross-sectioned specimens, respectively. In general, the bone density tended to change from type II to type III, as cross-sectioned specimens were evaluated from the midline to the canine. Type IV wasn't observed in this study. 2. The distance between the root apex and the lower border of the cancellous bone was 18.34mm-20.59mm. Considering that the bone has to be cut 5mm below the root apex during the procedure, autografts with about 15mm of vertical thickness can be obtained. 3. The thickness of cortical bone on the labial side increased from the root apex to the lower border of the mandible. The average values ranged from 1.43mm to 2.36mm. 4. The labio-lingual thickness of cancellous bone ranged from 3.43mm to 6.51mm. The thickness tended to increase from the apex to the lower border of the mandible and decrease around the lower border of cancellous bone. From the above results, the anatomic factors of the mandibular symphysis (bone density, thickness, quantity and length of the cortical bone and cancellous bone) didn't show any difference from Caucasians, and it cannot be viewed as the cause of failure in autografts in the maxillary sinus for implants.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.4
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• pp.558-563
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• 2000

The lasers have been used in dentistry for more than 30 years and the application of lasers for drilling dental hard tissue has been investigated since the early developement of lasers. Recently, the Er:YAG laser was invented for hard tissue ablation. The Er:YAG laser, having a wavelength of 2.94um, is highly absorbed in both water and hydroxiapatite, leading to a very effective material for hard tissue removal by bursting off the solid tissue component that is, enamel and dentin are removed by the Er :YAG laser by water vaporization and microexplosion, without any melting of inorganic tissues. Therefore, the Er:YAG laser produced round craters with well defined margins and the surrounding tissues had no cracks and no charring. When used for cavity preparation, pulpal damage should not occur if hear buildup is minimized by careful selection of exposure parameters and by use of a water spray. The present study demonstrated that the Er:YAG laser cut the tooth substance adequately for composite resin restoration, without having undesirable side effects such as harmful effects on the pulp, discoloration or cracking etc. Also, the child patients were well cooperative during laser treatment mainly because of little noise, lesser vibration and minimal pain compared to conventional means of cavity preparation.

• Food Science and Preservation
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• v.21 no.4
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• pp.581-586
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• 2014

With the current consumer trend toward health and wellbeing, the demand for consumption of fresh cut vegetables has been increasing. As a popular vegetable with functional components, sedum (Sedum sarmentosum) is widely used in Korea as a side dish that needs no cooking. In this study, to provide a hurdle technology for postharvest sedum, the effects of combined treatment of 1% acetic acid for washing and $10kJ/m^2$ UV-C irradiation on the microbial growth and quality of sedum were examined. After the treatment, the sedum samples were stored at $10^{\circ}C$ for six days, and the results of their microbial analysis as well as their color, vitamin C content, and antioxidant activity were analyzed. The combined treatment with acetic acid and UV-C irradiation reduced the initial populations of the total aerobic bacteria and the yeast and molds in the sedum by 3.28 and 4.22 log CFU/g, respectively, compared to those in the control. The Hunter L, a, and b values of the sedum did not significantly differ across the treatments. In addition, the vitamin C content and the antioxidant activity decreased significantly during the storage, regardless of the treatment. These results suggest that the combined treatment with 1% acetic acid and $10kJ/m^2$ UV-C irradiation can be useful as a hurdle technology for retaining the microbiological safety and quality of sedum during its storage.