• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.85-94
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• 2004

Experimental study on combustion characteristics of double swirl coaxial injectors has been conducted for the assessment of critical injector design parameters. A reusable, unielement thrust chamber has been fabricated with a water-cooled copper nozzle. Two principal design parameters. a swirl angle and a recess length, have been investigated through hot firing tests for the understanding of their effects on high pressure combustion. Clearly, both parameters considerably affect the combustion efficiency, dynamics and hydraulic characteristics of an injector. Internal mixing of propellants in a recess region increases combustion efficiency along with the increase of a pressure drop required for flowing the same amount of mass flow rates. It is concluded that pressure buildup due to flame can be released by the increase of LOx flow axial momentum or the reduction of a recess length. Dynamic pressure measurements of the thrust chamber show varied dynamic behaviors depending on injector configurations.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.1
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• pp.95-105
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• 2016

Spray-dried NiO-based oxygen carriers developed for chemical looping combustion required high calcination temperatures above $1300^{\circ}C$ to obtain high mechanical strength applicable to circulating fluidized-bed process. In this study, the effect of CBB ($CaO{\cdot}BaO{\cdot}B_2O_3$) addition, as a binder, on the physical properties and oxygen transfer reactivity of spray-dried NiO-based oxygen carriers was investigated. CBB addition resulted in several positive effects such as reduction of calcination temperature and increase in oxygen transfer capacity and porosity. However, oxygen transfer rate was considerably decreased. This was more apparent when a higher amount of CBB was added and MgO was added together. From the experimental results, it is concluded that CBB added NiO-based oxygen carriers are not suitable for chemical looping combustion and a new method to reduce calcination temperature while maintaining high oxygen transfer rate of NiO-based oxygen carriers should be found out.

• Research in Plant Disease
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• v.18 no.1
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• pp.40-44
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• 2012

Xanthomonas arboricola pv. pruni is the causal agent of bacterial black spot disease on some stone fruits, e.g. peach, plum and apricot. To evaluate pathogenicity of Xanthomonas arboricola pv. pruni strain from plum, inoculum of the isolated strain was spray inoculated to fruits and leaves of apricot, Japanese apricot and plum. Apricot and Japanese apricot showed severe black spot symptoms on fruits and shot hole symptoms on leaves. In case of apricot, about fifty percent of fruits did not grow and dropped by hypersensitive reaction to spray infection. Plum, cv. Formosa was very susceptible, showing severe black injury lesions on fruits and cankers on leaves and new twigs. On the other hand, plum cv. Daesukjosaeng, was highly resistant. Fruits of several plum cultivars such as Formosa and Chuhee were severely infected at natural infected orchards by X. arboricola pv. pruni. Where as those of Daesukjosaeng, Taeyang, Soldam and Hongrogen were moderately infected.

• Research in Plant Disease
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• v.15 no.3
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• pp.187-192
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• 2009

Pepper powdery mildew, Leveillula taurica is one of the most important pathogens of pepper in the greenhouses and fields in Korea and is becoming a worldwide disease. These experiments were carried out to investigate the optimal germination, disease development conditions, disease incidence and effective inoculation methods of pepper powdery mildew. The incidence of powdery mildew was investigated throughout the country based on the major pepper growing areas in 2009. The average rate of infected leaves ranged from 15.3% to 81.8% in greenhouses and fields. Powdery mildew incidences were more severe in greenhouses than those of fields. The optimal temperature for conidial germination was $25^{\circ}C$ and showed the highest germination at 6 hs after treatment. The range of temperature for germination was $10^{\circ}C$ to $35^{\circ}C$. Temperature of greater than $30^{\circ}C$ and below $20^{\circ}C$ affected the abnormal germination and germ tube elongation. The optimal relative humidity for germination and germ tube elongation was 85% and germination increased as relative humidity increased. Disease development started 8 days after inoculation and showed the highest disease severity at 15 days in greenhouse and field regardless of varieties. Among three different inoculation methods tested the spore dropping method was better than touching with infected leaves and spraying with spore suspension. However, the method has limitation in mass inoculation due to the amount of time consumed.

• Research in Plant Disease
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• v.19 no.3
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• pp.188-195
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• 2013

This study was carried out for the downy mildew resistant test between 2010 and 2012. A set of 22 accessions belonging to 2 wild species and 20 varieties of the genus Cucumis, originating mainly from the Asian Vegetable Research and Development Center (AVRDC) Gene Centre, was evaluated for resistance to Pseudoperonospora cubensis, causal agent of cucumber downy mildew. The youngest fully expanded true leaves were found suitable for in vitro screening. Both leaf discs and full leaves could be kept fresh longer when applying 0.2 ${\mu}g/ml$ of gibberellin acid (GA). The incubation temperature of $20^{\circ}C$ was found to be the most suitable temperature for symptom development comparing with 15 and $25^{\circ}C$. Symptom development was faster when contact diseased leaf discs (2 weeks after inoculation) on to fresh leaf samples comparing with using conidia suspension ($10^5$ spores/ml). The numbers of spots in 'C-19' were lower than other varieties. 'C-19' variety was also showed the highest level of downy mildew resistant at $20^{\circ}C$ chamber in 6 days after inoculating with pathogen and displayed 0.90 (under 10%) of the infected rate. However, other varieties displayed susceptible in the pathogen sprayed plots. 'C-19' was the most resistant variety and no lesion was observed. Based on all data, 'C-19' can be a useful variety for the prevention of downy mildew.

• Korean Journal of Plant Tissue Culture
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• v.25 no.5
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• pp.289-293
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• 1998

We investigated the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity in methanol extracts of 64 cultured cell lines, which were derived from various plant species, and the ascorbate content in cell lines, which showed a high radical scavenging activity. Thirteen cell lines revealed the antioxidative activity ($IC_{50}$) by methanol extracts of less than 50 mg in cell fresh wt. Of them, six cell lines showed the same Rf value as ascorbate on the DPPH sprayed silica gel TLC. The ascorbate content in cell lines of Rosa multiflora, Scutellaria baicalensis, and Achyranthes japonica showed 48.5, 30.3, and $16.8\;\mu\textrm{g}$ per g cell fresh wt by HPLC analysis, respectively. In callus cultures of S. baicalensis, the concentration of ascorbate reached a maximun ($39{\pm}3.4\;\mu\textrm{g}/g$ cell fresh wt) on 30 days after subculture, which corresponded to the stationary growth phase, and subsequently decreased by successive culturing.

• KSBB Journal
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• v.22 no.4
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• pp.234-238
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• 2007

We used electrospary ionization ion trap tandem mass spectrometry (ESI-IT tandem MS) to structural elucidation of three different biantennary-type glycans having zero, one, two galactoses (G0, G1, G2). The highest fragment ion in the MS/MS spectra of three glycans was produced by 0,2-ring cleavage of fucose-linked N-acetylglucosamine (GlcNAc) in reducing end. The fragment ions both from precursor ions and 0,2-ring cleaved ions ($^{0.2}An$; n=5 for G0, n=6 for G1 and G2) were not overlapped each other. As results of $MS^n$ analyses, tandem fragmentation trees of each glycans were generated and 2,4-ring cleavages ($^{2.4}A_6$) were occurred in GlcNAc linked to reducing end GlcNAc. This structural elucidation and fragmentation study of N-linked glycans by tandem mass spectrometry can be applied to structural analysis of more complicated glycans.

• The Journal of the Acoustical Society of Korea
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• v.16 no.2
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• pp.89-94
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• 1997

A new type SO$_2$ gas sensor with a particular inorganic thin film on SAW devices was developed. The sensor consisted of twin SAW oscillators of the center frequency of 54 MHz fabricated on the LiTaO$_3$ piezoelectric single crystal. One delay line of the sensor was coated with a CdS thin film that selectively adsorbed and desorbed SO$_2$, while the other was uncoated for use as a stable reference. Deposition of the CdS thin film was carried out by the spray pyrolysis method using an ultrasonic nozzle. The sensor could measure the concentration in air less than 0.25 parts per million of SO$_2$. Stability of the sensor turned out to be as good as less than 20ppm, recovery time after each measurement was as short as 5 minutes. Repeatability of the measurement was confirmed through so many reiterated experiments. Hence, the SAW sensor developed through this work showed promising performance as a microsensing tool of SO$_2$. Further work required to improve the performance of the sensor includes enhancement of the reactivity of the CdS thin film with SO$_2$ through appropriate dopant addition, an increase of the center frequency of the SAW device.

• Tuberculosis and Respiratory Diseases
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• v.46 no.2
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• pp.251-259
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• 1999

Background: Even though the necessity for premedication has been questioned, some combinations of antisialogogues, sedatives and analgesics are usually employed by most bronchoscopists. The goal of this study was to determine whether fiberoptic bronchoscopy(FOB) could be performed safely and effectively without premedication while using a standardized topical anesthetic. Method: Eighty outpatients were randomized in a double-blind manner into group I(n=20) with 1 ml normal saline, group II(n=20) with 0.5mg of atropine, group III(n=20) with 0.5mg of atropine plus 5mg of midazolam, and group IV(n=20) with 0.5mg of atropine plus 50mg of meperidine, given intramuscularly 30 minutes before FOB as premedication Topical anesthetics administered were same in each group. Each patient was given 5ml(200mg) of 4% nebulized lidocaine and additional intratracheobronchial 2% lidocaine. Oxygen saturation, pulse rate and electrocardiogram were monitored and recorded before, during, just after and 2 minutes after FOB. Immediately after FOB, the bronchoscopists answered four questions such as ease of procedure, extent of coughing, extent of secretion, and overall impression. Before leaving bronchoscopy suite, patients completed similar questions on discomfort during procedure, and willingness to return for a repeat procedure. Results: Age, gender, baseline pulmonary function, dose of 2% lidocaine used for topical anesthesia, and duration of FOB were not significantly different. There was no statistical difference among group I to IV with regard to extent of coughing answered by bronchoscopist. But extent of secretion was significantly different between group I without atropine and group II-IV with atropine. And there was also significant difference in ease of procedure and overall impression among groups. There was no statistical difference in patient's willingness and level of discomfort among the groups. Thirteen patients(16%) showed hypoxemia(arterial oxygen saturation: <90%), and 3 patients(4%) showed significant tachyarrhythmia(heart rate: > l60/min), but the rate of complication was not statistically different among the groups. Conclusion: These results suggest that the value of premedication is questionable for outpatient FOB, although it may be necessary in excessively anxious patient.