• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.1
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• pp.1-8
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• 1997

To find the tooth selectivity of the dredge for catching the ark shell Scapharca broughtonii, the probabilities of the ark shells which are not sifting through the gaps between teeth were calculated for the various shell lengths. Considering that these probabilities are in proportion to the relative catching efficiencies, selectivity curves for the ark shell dredge were estimated for the various gaps between teeth. The ratio of the shell length of ark shell to the distance between teeth indicating the relative catching efficiencies of 0%, 50%, 100% respectively, were calculated by using these selectivity curves, and the values were 1.00, 1.32, 1.54 in the distance of 4.0cm between teeth and then, the ratios showed a slight tendency to decrease as the distance between teeth increased in the relative catching efficiency of 100%, In addition, the range of shell length for catching, that is, the range of selective shell length by the distance between teeth was 0.54 in the distance of 4.0cm between teeth.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.4
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• pp.366-376
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• 1999

In order to examine the catching selectivity of the ark shell(Scapharca broughtonii) dredge, the various factors affecting the selective action of the dredge are analyzed, and the probabilities of the ark shell not shifting through the gaps between the teeth, and the mesh of the netting bag, are calculated for the various shell lengths, using the relation between the posture and the length when the shell passes through these parts.Considering that the probability of making catch is the product of the both probabilities described above, and that this probability is proportional to the relative catching efficiency, the selectivity curves for the ark shell dredge were estimated for various gaps between the teeth and for the various mesh sizes of the netting bag. The obtained results are summarized as follows :1. The ratios of the shell length of ark shell to the distance between teeth indicating the relative catching efficiency of 0%, 50, 100% respectively were 1.0, 1.26~1.28, 1.47~1.44, and that the selection ranges of selective shell length by the distance between teeth were 0.47~0.44, where the distances between teeth were 3.2cm, 3.6cm, 4.0cm, 4.4cm and 4.8cm. 2. The ratios of the shell length of ark shell to the mesh size indicating the relative catching efficiency of 0%, 50%, 100% respectively were 0.67, 0.84, 0.97 and that the selection range of shell length for catching, that in the range of selective shell length by the mesh size was 0.31, where the distance of 4.0cm between teeth, mesh size of 6.0 cm and the smaller mesh angle of $60^{\circ}$3. Where the distance between teeth is 4.0 cm and the smaller mesh angle is $60^{\circ}$, the selection range of shell length for catching of the ark shell dredge is decreased according to the mesh size, and it is minimized by 0.20 in the mesh size of 9.0~10.0 cm, but increased in the mesh size of over 11.0 cm. 4. Where the distance between teeth is 4.0 cm, the selective action by the mesh size of netting bag is begun with the mesh size of over 10.0 cm.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.1
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• pp.49-54
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• 2005

Shell teeth, a rare dysplastic condition of dentin, was first described by Rushton in 1954. It is characterized by normal enamel, extremely thin dentin, correspondingly large pulp chambers, and shortened roots. This case report is of a male 3 years old. He is refered to the Chosun University dental hospital Pediatric Dentistry because of dental caries and dentin hypoplasia. Intra-oral examination showed attrition of all primary teeth. Radiographic examination showed that the pulps were extremely large with only a shell of surrounding hard tissue. The permanent premolars were missed congenitally. The diagnosis was shell teeth. Because of behavior problem, all dental treatment was undertaken with general anaesthesia. Extration, endodontic treatment and SS crown were performed. The patient has now been wearing the space maintainer and manages it well. The patient is seen intervals for supervision and follow-up care.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.14 no.1
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• pp.31-35
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• 2018

Dentinogenesis imperfecta is a hereditary disorder that causes abnormal dentin formation and tooth morphology. Affected teeth show very thin dentin and large pulp chamber. Immediately after their eruption, the teeth tend to be destroyed rapidly. Early dental intervention is recommended to improve the feeding capacity and quality of life for the child, to maintain vertical dimension, and to promote healthy and functional dentition. This case report describes a treatment for a 4-year-2-month-old girl whose primary and permanent dentition were affected by Dentinogenesis Imperfecta. Shell teeth were observed in the entire primary dentition. The pulp of most teeth was exposed and the patient complained of pain. Most paternal family members were transferred to the Dentinogenesis Imperfecta. She needed an extensive dental treatment, but her compliance could not be expected because she was very young and anxious. So we decided to treat her under general anesthesia. All molar teeth are restored with Stainless Steel crown. Maxillary anterior teeth were extracted and mandibular anterior teeth are restored with composite resin. The patient's pain disappeared and masticatory function was restored.

• The Korean Journal of Malacology
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• v.27 no.2
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• pp.91-97
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• 2011

This study examines the morphological features of larval and postlarval shells of the paedomorphic bivalve Crenella decussata Montagu, 1808 from the Sea of Japan. During the early morphogenesis of the shell of C. decussata the following characteristics appear: prodissoconch I -the anterior and posterior provincular teeth, a broad primary ligament pit located on the chondrophore; nepioconch - the anterior and posterior juvenile teeth,primary lateral teeth, fine commarginal and radial sculpture. Larvae of C. decussata distinctly differ from other mytilid larvae by a D-shaped shell, absence of umbo, astraight hinge margin, and homogeneous fine-grained sculpture without co-marginal lines of growth. These shell characters indicate lecithotrophic development of this species. Some morphostructures are revealed which might be used in crenellin taxonomy.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.4
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• pp.267-273
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• 2000

The tooth selectivity of the dredge for catching venus clam (Gomphina melanaegis) was described in which the teeth penetrated the bottom and lifted the shell into the bag. Some factors affecting the selection action of the teeth of the dredge were analyzed related to shell length and shell height. The retention probability of venus clam not sifting through the gaps between the teeth was calculated for various shell lengths and was fitted to two parameter logistic selection curve. The formula obtained is as follows: $P= \frac{1}{1+exp[8.24](\frac{d}{L_1}-0.649)}$, where d is distance between teeth and $L_1$ is a shell length. For biological minimum size(25mm) of venus clam to be catchability 50% the distance between teeth was estimated 16.2mm from the logistic curve. Therefore it is desirable to extend that current spacing between teeth from 12mm to 16mm for the venus clam dredge. That space increasing enables fuel oil of vessel to drag a dredge to be reduced and also man power to sift through sifter smaller venus clams on boards to be reduced.

• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.4
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• pp.23-29
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• 2005

In order to improve the efficiency of hydraulic gear pumps or motors especially for high operating pressure, power losses due to viscous friction and leak flow through gear teeth end-gaps are considered in this paper. Optimal gaps minimizing the power loss for pumps and motors with uniform heights of gaps are analysed first. And the effect of the shapes of gaps with unequal heights on the power loss are studied and discussed by simulation. Considering that the outer shell lacing gear teeth may expand due to high internal pressure or thermal stress, the results drawn in this paper can be used for the design of high efficiency pumps and motors.

• The Korean Journal of Malacology
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• v.23 no.2
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• pp.155-164
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• 2007

A new species, Arca koumaci Lutaenko et Maestrati n. sp. (Bivalvia: Arcidae), is described from New Caledonia. The species is characterized by the small size, the convex shell with a strong posterior umbonal ridge covered by spikes, the widely curved ventral margin, and presence of cancellate sculpture and convergent marginal teeth. Presence of spikes on the posterior ridge is a unique morphological feature recorded for the first time in the genus. It is proposed that the only subgenus, namely Pliocene A. (Arcoptera) Heilprin, 1887, apart from nominative, can be recognized in the genus. Three morphological types are distinguished within the genus based on shell shape and sculpture. Bathymetric analysis shows that representatives of Arca inhabit water depths down to 175 m, and more than half of Recent species were found below 50 m. Types of A. bouvieri P. Fischer, 1874, Arca boucardi Jousseaume, 1894, Arca avellana Lamarck, 1819, and Arca retusa Lamarck, 1819 are illustrated.

• Parasites, Hosts and Diseases
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• v.21 no.1
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• pp.118-124
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• 1983

The distribution, external morphology, radula, chromosome numbers of Planorbidae snails were studied. 1. The specimens were collected at four stations in Nonsangun, Kongjugun, and Daedukgun which are located around Geum river. Three genera and three species of Planorbidae, Hippeutis cantorir Segmentina hemisphaerula and Gyraulus cenvexiusculus, were collected. H. cantori was the most abundant species among the three species. G. convexiusculus was the least abundant one. 2. Each species could be identified on the basis of its external characteristic, since the periphery of each species has a peculiar shape. H. cantori was the largest one among the three species. 3. The radula formula of each species was very similar to other species. The size of radula was proportional to the size of shell. The radula formulae of H. cantori, S. hemisphaerula, and G. convexiusculus were 29 : 1 : 29, 23 : 1 : 23, and 16 : 1 : 16 respectively. The difference of radula formula could be found in the total numbers of laternal and marginal teeth. 4. The haploid chromosome number of H. cantori was eighteen (n=18), S. hemisphaerula and G. convesiusculus were assumed to be same in their chromosome numbers (n: 18).