• Research in Plant Disease
• /
• v.19 no.4
• /
• pp.300-307
• /
• 2013

This study was conducted to determine the occurrence of leaf rot and leaf ring spot, caused by Rhizoctonia solani in Chinese cabbage under seedling nursery and cultivation greenhouses. Symptoms of leaf rot and leaf ring spot were found in three Chinese cabbage cultivars, Brassica campestris subsp. pekinensis, 'Ryeokgwang', 'Daetong', and 'CR mat'. In Hwacheon, the disease incidence was 73.8% in the seedling stage of the Chinese cabbage. In Icheon, the symptoms were observed on the upper leaves of the Chinese cabbage cultivar, 'Norangmini' with 20.5% of disease incidence. The symptoms appeared as primary lesions consisting of small, circular necrotic ring spots with gray color, 1.4-3.0 mm in diameter, accompanied by secondary rot lesions with large irregular borders of leaves. The color of mycelial mat of 20 isolates was dark brown and light brown. The average hyphal diameter of all the isolates was within 5.01-11.12 ${\mu}m$. Among the 20 strains isolated from Chinese cabbage, 16 isolates and four isolates anastomosed with the AG-1 (IB) and AG-1 (IC), respectively. Twenty isolates tested were only virulent on foliage parts of Chinese cabbage leaves but were avirulent on stem parts of the plants. Based on the mycological characteristics and pathogenicity test on host plants, the fungus was identified as Rhizoctonia solani.

• Research in Plant Disease
• /
• v.10 no.2
• /
• pp.121-125
• /
• 2004

An epidemic of target leaf spot of cucumber (Cucumis sativus) occurred in commercial greenhouses in Korea in 2000/2001. The early symptoms on the leaves were small brown spots with yellow halos. These lesions became irregular enlarging in diameter and eventually defoliation resulted. The causal agent was a fungus with morphological characteristics matching Corynespora cassiicola. The sequence of the ITS region of C. cassiicola CM2000-1 was identical to that of an authentic strain of Corynespora cassiicola. Optimal germination of spores and mycelial growth on plate was at 3$0^{\circ}C$. A long dew period on the leaf surface and high temperatures were the main contributing factors for disease development and the greenhouse epidemic. Artificial inoculation of the Korean isolate of C. cassiicola revealed resistance in some Korean cucumber cultivars.

• Research in Plant Disease
• /
• v.16 no.1
• /
• pp.86-89
• /
• 2010

Brown leaf spot caused by Phyllosticta cruenta from 2007 to 2009 occurred severely in an herbs exhibition on Doonggulle (Polygonatum odoratum) at Gangju pond in Jeongchon-myon, Jinju city, Gyeongnam province, Korea. The typical symptoms of this disease were appeared on the brown leaf spot of leaves. Lesions on the leaves were appeared elliptical or irregular with 2~8 mm in size. Infected leaves were wilted, blighted and eventually died. Pycnidiospores and pycnidia of the fungus were abundantly formed on PDA. The optimum temperature for mycelial growth was $20{\sim}{25^{\circ}C}$. Pycnidiospores were not readily formed on PDA, colorless in color, globose~subglobose in shape, $10{\sim}18{\times}5{\sim}12{\mu}m$ in size and appendage hanged $4{\sim}15{\mu}m$ in size. Pycnidia were globose~subglobose in shape, dark brown in color and $60{\sim}162{\times}70{\sim}174{\mu}m$ in size. On the basis of mycological characteristics and pathogenicity test on host plants, the fungus was identified as Phyllosticta cruenta (Kunze: Fries) Kickx. This is the first report on the brown leaf spot of Doonggulle caused by P. cruenta in Korea.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.951-954
• /
• 2003

Generally, for the burrs formed in machining are irregular and very sharp in shape, it is usually very difficult to measure burr accurately. But, it is proved that precision measurement for micro burr using the conoprobe sensor by conoscopic holography method is possible. We developed 3D burr measurement system using this sensor. The system is composed of Conoscopic laser Sensor, X-Y table, controller and 3D measurement program. Some measurements using the developed system are applied to burrs formed in micro drilling and piercing.

• Journal of the Korean Institute of Navigation
• /
• v.25 no.3
• /
• pp.247-256
• /
• 2001

This study aims to develop the information service system of integrated seakeeping performance for seagoing vessels. It has been successful in developing the intended system which has made possible to provide the following functions and capabilities. o immediate computation of the dynamic motions of a ship against the present and future weather conditions; o evaluation of the integrated seakeeping performance of a ship on a real time basis and providing the navigators with the seakeeping informations on the spot enabling them to take the most appropriate countermeasures; and o supporting the navigators in the selection of a safe sailing route by providing the integrate seakeeping performance.

• Journal of agriculture & life science
• /
• v.50 no.5
• /
• pp.251-255
• /
• 2016

In year of 2013, anthracnose disease symptoms were observed on stem of stonecrop in a plant resource field, Southern Forest Resource Research Center, Jinju, South Korea. The disease symptoms were appeared 2-5 cm smudged irregular black spot color on the plant stems. Suspected pathogen was isolated from the lesion with surface sterilization method and identified it as Colletotrichum gloeosporioides by morphological characteristics and phylogenetic analyses. Artificially inoculated the isolated pathogen led to the similar disease symptom as originally observed in the field. The fungal pathogen was re-isolated from the inoculated lesion and it exhibited the same characteristics compared to the original isolate. This is the first report of anthracnose of stonecrop grown in open fields, caused by Colletotrichum gloeosporioides in Korea.

• Research in Plant Disease
• /
• v.8 no.1
• /
• pp.63-65
• /
• 2002

Red spot disease was found on broad bean (Vicia faba) in several farmer's field located in Changseon-myon, Namhae-gun, Gyeongnam provice in Korea. The typical symptoms of the disease were appeared on leaves and stems. The infection rates of the disease in the surveyed area were ranged from 16.4 to 84.6%. Lesions on the leaves were round with 1~4.2 mm in size and on the stem were narrow long fusiform with 1~15 mm in size. Conidia and conidiaphores were not readily farmed on PDA, however, a few conidia were formed on PDA added in extracts of 10 g of broad bean leaves. Conidia were light yellow green in color, globose or obovoid in shape, and 10~24$\times$8~22 $\mu$m in size. Conidiophores were cylindrical in shape, light brown in color and 3.6~12.8 $\mu$m in wide. Sclerotia of the fungus were readily formed in artificial media such as PDA. They were ellipsoid to irregular in shape, 1.2~11.8 mm in size and dark in color, The optimum temperature far growth of the fungus was about 2$0^{\circ}C$. On the basis of mycological characteristics, the fungus was identified as Botrytis fabae. This is the first report on the red spot of broad bean caused by Botrytis fabae in Korea.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.16 no.8
• /
• pp.719-731
• /
• 1991

This paper introduces a relatively simple computer simulation method for analyzing trajectory of electron beam in cylindrical electrode of the CRT, which outputs the cutoff voltag, beam current, spot size and plots out the trajectory, rom the input data on physical construction and applied voltages of electron gun. In order to improve computing speed in obtaining potential distibution, the authors have ivided the space into seveal setos and allocated different mesh sizes epending on the acuracy required to each sector and applied the finite difference method in calculation. The plot of trajectoy obtained from the simulation provided useful insight into the focusing mechanism of the CRT. The computed and measured result including beam curent. spot sizs and cutoff voltages for several model guns have ageed within eperimental error. The simulation program enables the designer to compare the effects of varied electrode shpe without the epense of building an actual gun and may be appli in esigning and implementing the electron gun assemply.

• Journal of the Korean Vacuum Society
• /
• v.7 no.2
• /
• pp.77-81
• /
• 1998

The eptiaxial growth of Ge on the clean and surfactant (Sn) adsorbed surface of Ge(111) was studied by the intensity oscillation of a RHEED specular spot. In the case of epitaxial growth without the adsorbed surfactant, the RHEED intensity oscillation was stable and periodic up to 24 ML at the substrate temperature of $200^{\circ}C$. Therefore the optimum temperature for the epitaxial growth of Ge on clean Ge(111) seems to be $200^{\circ}C$. However, in the case of epitaxial growth with the adsorbed surfactant, the irregular oscillations are observed in the early stage of the growth. The RHEED intensity osicillation was very stable and periodic up to 38 ML, and the d2$\times$2 structure was not charged with continued adsorption of Ge at the substrate temperature of 2002$\times$2. These results may be explained by the fact that the diffusion length of Ge atoms is increased by decreasing the activation energy of the Ge surface diffusion, resulted by segregation of Sn toward the growing surface.

• Research in Plant Disease
• /
• v.13 no.1
• /
• pp.66-70
• /
• 2007

During 1997 and 1998, a new disease of lettuce (Lactuca sativa) was observed on greenhouse-grown plants in Kwangju and Kwangmyung. Lesions on leaves were irregular, small, pale green to black, water-soaked, and 2 to 5 mm in diameter, Coalescing lesions sometimes caused defoliation of older leaves. Isolations made from diseased leaves on yeast extract dextrose calcium carbonate agar yielded nearly pure cultures of a yellow pigmented bacterium typical of a xanthomonad. Two bacterial strains (SL0246 and SL1352) were purified and used for further tests. Pathogenicity of strains was confirmed on 5-week-old lettuce plants injected with bacterial suspensions containing $10^8$ cfu/ml of phosphate buffered saline. The representative Xanthomonas strains isolated from lettuce were compared with a reference strain X. campestris pv, vitians for fatty acid profiles and metabolic fingerprints using GN2 microplate, showing that all outcomes were indistinguishable between the representative and reference strains. This is the first report of bacterial leaf spot and dry rot of lettuce in Korea.