• ETRI Journal
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• v.30 no.1
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• pp.81-88
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• 2008

The security threat posed by worms has steadily increased in recent years. This paper discusses the application of the optimal and sub-optimal Internet worm control via Pontryagin's maximum principle. To this end, a control variable representing the optimal treatment strategy for infectious hosts is introduced into the two-factor worm model. The numerical optimal control laws are implemented by the multiple shooting method and the sub-optimal solution is computed using genetic algorithms. Simulation results demonstrate the effectiveness of the proposed optimal and sub-optimal strategies. It also provides a theoretical interpretation of the practical experience that the maximum implementation of treatment in the early stage is critically important in controlling outbreaks of Internet worms. Furthermore, our results show that the proposed sub-optimal control can lead to performance close to the optimal control, but with much simpler strategies for long periods of time in practical use.

• Korean Journal of Environmental Biology
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• v.33 no.2
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• pp.153-159
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• 2015

The oligochaete worms in the genus Nais are common to freshwater habitats. These worms have a highly-developed prostomium and pigmented eye spots. All species have hair chaetae, bifid or single pointed needle chaetae on the dorsal side and ventral chaetae beginning in II with bifid crotchets. Most species of Nais genus live in areas where bottom is covered by sand, gravel or organic matter in aquatic plants. Currently, 26 species of Nais have been recorded worldwide. From the recent faunal studies, 3 species of Nais have been newly reported in Korea. Here, we newly report 6 species of Nais with diagnosis, illustrations and identification keys to Korean Nais species: N. behningi, N. pseudobtusa, N. simplex, N. bretscheri, N. stolci and N. elinguis.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.4
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• pp.252-263
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• 2001

Nematode infections compromise human health and reduce agricultural productivtiy. Experiments that exploit the powerful molecular genetics of the free-living nematode Caenorhabdl - elegans have contributed to our understanding of how the major classes of anthelmintic nema-tocides kill worms and how worms might evolve resistance to these drugs In C. elegans, as in parasites, benzimidixoles interfere with microtubule polyumerization the imidazothiazoles/tetra-hydropyrimidines activate nicotinic acetylcholine receptors, and the macrocyclic la ctones activate qlutamate-gate chloride chanels. Mutant alleles of genes that encode drug targes often confer resistance in C. elegans. Preliminary evidence suggests that alleles of homologous genes in parasites will, in many cases, also play a role in resistance. Thus information acquired from C. elegans can be usefully applied to understand the mechanisms of drug sensitivity and the genetics of resis-tance in parasites.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.10
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• pp.44-51
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• 2006

According to global trend of the expanding need of high-quality automobiles, the usage of small precise worm consisting of gearing part for motors to actuate convenience modules has increased rapidly. Precision of those worms has very sensitive characteristic to motor performance and noise. Forming process has been generally used to manufacture worms because of its mass productivity. However, it has problems such as deformation due to residual stress and wear of dies. Planetary milling and side milling are among alternatives using cutting tools. To overcome those problems the two machining methods have some contrast features in the sense of tool numbers and cutting mechanism. In this paper, machinability of both methods was compared in terms of cutting force, precision and cycle time.

• Korean Journal of Environmental Biology
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• v.21 no.1
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• pp.42-44
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• 2003

The study of the gill infection of rockfishes, Sebastes spp. by monogenetic trematodes conducted during March 2002 to June 2002 are presented. Three species are reported krom examination of 23 rockfishes collected from Oregon Coast Aquarium and Newport fish market, Oregon. Ten rockishes belonging to three species showed an infection rate of 43.5%. A total of 135 monogenetic trematodes was found in the gills of Sebastes spp. Of 135 worms recovered from the gills of 4 harbor rockfishes, two were Sebastes maliger, 14 S. melanops, 110 S. pinniger, and 9 S. crameri. Prevalence and intensity in Microcotyle seba.fis were 11.9％ and 4.0, and for Trochopus trituba they were 81.5% and 55.0, and for Trochopus australis, they were 6.7% and 2.3, respectively. These worms are mainly found firmly attached to the primary lamellae of the gills of the rockfishes.

• Fisheries and Aquatic Sciences
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• v.1 no.1
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• pp.79-81
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• 1998

To investigate the influence of originated host and water temperature on the infectivity and growth of Microcotyle sebastis, juveniles of Schlegel's black rockfish (Sebastes schlegeli) were exposed to the eggs of M. sebastis originated from. Schlegel's black rockfish and black rockfish (Sebastes inermis) at $10^{\circ}C$ and $10^{\circ}C$. There were significant differences between the two isolates in the infectivity of eggs, and the growth of worms. The growth of M. sebastis was significantly affected by water temperature, and worms grew faster in $20^{\circ}C$ than in $10^{\circ}C$.

• Proceedings of the Korea Information Assurance Society Conference
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• 2004.05a
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• pp.181-185
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• 2004

In these days, many reports noticed that the Internet worms spread out and have done considerable damage to all over the world network within a few days. The worms, which is infected from various route such as e-mail, can spread very fast with common property, self replication. But, there is not prepare for the way effectively to interrupt internet worm. Therefore, to prevent our network resource, internet hosts and user clients, the systemic categorization and automatic defense mechanism is required in the Internet worm research. Hence, in this paper, we describe internet worm propagation and defense model.

• Parasites, Hosts and Diseases
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• v.46 no.1
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• pp.41-43
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• 2008

The ruddy turnstone, Arenaria interpres interpres, a migratory Korean bird, was proved to be a natural definitive host for Gynaecotyla squatarolae (Digenea: Microphallidae). The ruddy turnstone was found dead at the seashore of Okgu-eup, Gunsan-si, Jeollabuk-do. The intestinal tract was examined, and 98 unknown flukes were recovered. The worms were $600{\times}284{\mu}m$ in size, and had 2 ventral suckers. The seminal vesicle was large, the genital atrium was prominent, and the average egg size was $20{\times}12.5{\mu}m$. Based on these results, the worms were identified as G. squatarolae. This is the first report on the ruddy turnstone as a natural definitive host of G. squatarolae in the Republic of Korea.

• Parasites, Hosts and Diseases
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• v.54 no.6
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• pp.809-812
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• 2016

Adult specimens of Oswaldotrema nacinovici (Digenea: Philophthalmidae) have been first identified in Korea from 2 migratory birds (whimbrels, Numenius phaeopus) which were found dead at a western seashore area near Gunsan. The worms were recovered in the intestine of these birds. The worms were morphologically characterized by a large ventral sucker in comparison to the oral sucker, an external seminal vesicle extending beyond the posterior margin of the ventral sucker, and conspicuous uterine seminal receptacle. It was noteworthy that metacercariae-like bodies were contained within the inflated regions of 2 ceca. Other intestinal trematode species found in whimbrels included Spelotrema pygmeum, Gynaecotyla squatarolae, Maritrema obstipum, and Himasthla megacotyle. Zoonotic potential of these trematode species should be taken into considerations.

• Parasites, Hosts and Diseases
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• v.56 no.4
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• pp.375-378
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• 2018

A total of 44 adult or juvenile nutrias were necropsied for disease survey. A large nodule was found in the liver of a nutria. The histopathological specimen of the hepatic nodule was microscopically examined, and sectional worms were found in the bile duct. The worms showed a tegument with spines, highly branches of vitelline glands and intestine. Finally, we histopathologically confirmed fascioliasis in a wild nutria. In the present study, a case of fascioliasis in a wild nutria is first confirmed in Korea.