• Research in Plant Disease
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• v.14 no.1
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• pp.21-25
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• 2008

This study was conducted to decide disease incidence level of rice leaf blast required for reasonable fungicide application in paddy field. We induced the disease development by inoculating rice blast pathogens on rice seedlings (Jinmibyeo) in the greenhouse and transplanting the infected seedlings in the field two weeks after rice plants were transplanted. We scored the disease incidence, grouped and marked according to degree of percentage of diseased leaf area at maximum stage of disease development. The percent diseased leaf area (PDLA) had negative correlations with panicle number per hill, ripened grain (%), and total yield; their correlation coefficients (r), $-0.97^{**}$, $-1.00^{**}$ and $-0.96^{**}$, respectively. However, it had positive correlations with spikelets per panicle and thousand grain weight; their correlation coefficients (r), $0.98^{**}$ and $0.98^{**}$, respectively. Gain threshold (GT) calculated based on control cost and market price was estimated to be 8.35. Economic injury level (EIL) obtained based on GT and coefficient of damage of regression equation between disease incidence and the different yield components; panicle number per hill, spikelets per panical, ripened grain(%), thousand grain weight and yield were 41.8, 9.7, 19.1, 291.1 and 3.4%, respectively. Economic threshold (ET) for yield was 2.7% ($3.4%(EIL){\times}0.8$) on PDLA. These results suggest that application of fungicide is necessary when two under leaves are almost covered with lesions or contained more than twenty large lesions under leaves at maximum tillering stage.

• Korean journal of applied entomology
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• v.48 no.2
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• pp.237-243
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• 2009

This study was conducted to develop economic injury level (ElL) and economic threshold (ET) of Cabbage armyworm, Mamestra brassicae L. on cabbage (Brassica oleracea L. var). The changes of cabbage biomass and M. brassicae density were investigated after introduction of larval M. brassicae (2nd instar) at different densities: 0, 1, 2, 4, 8, and 16 larvae per plant at 40 d after planting for an open field experiment, and 0, 2, 5, 8 and 12 larvae per plant at 25 d after planting for a glass house experiment. In the field experiment, the yield loss of cabbage was not significantly different among treated-plots at 30 d after the larval introduction, showing an over-compensatory response of cabbage plants to M. brassicae attack. In the glasshouse experiment, however, the biomass of cabbage at 15 d after the larval introduction significantly decreased with increasing the initial introduced number of M. brassicae, resulting in 38.3, 36.7, 21.7, 23.3 and 16.7g in above treated-plots, respectively. The relationship between cumulative insect days (CID) and yield loss (%) of cabbage was well described by a nonlinear logistic equation. Using the estimated equation, ElL of M. brassicae on cabbage was estimated at 44 CID per plant based on the yield loss 14%, which take into account of an empirical gain threshold 5% and marketable rate 91% of cabbage. Also, ET was calculated at 80% of the EIL: 35 CID per plant. Until a more elaborate EIL-model is developed, the present result may be useful for M. brassicae management at early growth stage of cabbage.

• Weed & Turfgrass Science
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• v.1 no.4
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• pp.13-17
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• 2012

A field experiment was conducted to investigate the effect of Acalypha australis occurrence on the growth and yield of soybean, to predict the reduction rate of soybean yield caused by competing with A. australis and to establish the economic threshold of A. australis for soybean cultivation. As the density of A. australis increase, the height and stem length of soybean were not affected by the competition with A. australis, however, the yield of soybean was decreased as 11~51% as compared with weed-free condition. The relationship between weed density and soybean yield was established as Y=415.5 / (1+0.003356X) and the reduction rate of soybean yield were predicted from this equation. Compared with the weed-free condition, the reduction rate of soybean yield were calculated as 0.3~9%, 17~29%, and 40~46% when the density of A. australis were 1~30, 60~120, and 200~250 plants $m^{-2}$, respectively. The economic threshold level of A. australis for soybean cultivation was established as 6.3 plants $m^{-2}$ from the Cousens' equation.

• Journal of Korean Society of Forest Science
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• v.83 no.4
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• pp.450-459
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• 1994

The damage by the black-tipped sawfly, Acantholyda posticalis posticalis Matsumura, has been increasing at several locations in central part of the Korean peninsula. This study was undertaken at selected plots in Kapyung-gun, Kyunggi Province and Hongchon-gun, Kangwon Province from 1984 to 1987. The purpose of this study was to provide basic information for integrated control of this pest and to determine the economic threshold by investigating the pest host interactions with special reference to damage analysis. The results obtained were as follows ; 1. The damage was more severe at upper part than at lower part of the crown. The vertical distribution of dry weight of damaged trees above ground showed L-type distribution, whereas that of healthy trees showed C-type distribution. 2. The needle loss by sawfly reduced both of height and the diameter growth of the main stem. The growth reduction occurs when the needle loss is 50% or higher. About 10% of tree growth was reduced at 50% of needle loss. 3. The reduction of diameter growth was more severe at upper part than at lower part of the main stem. 4. Volume growth was reduced when more than 50% of the needles were damaged after three years of the sawfly infestation. Reductions of total volume increment at the levels 70% and 90% of needle damage were 9% and 20%, respectively.

• The Journal of Aerospace Industry
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• s.68
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• pp.80-94
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• 2006

유효경쟁시장은 사업자의 수와 시장구조 측면에서는 독과점적인 시장이더라도 기존사업자간 경쟁이 상당히 치열하거나 잠재적 진입에 의한 경쟁압력이 커서 특정사업자가 시장지배력을 보유하거나 이를 행사하기 어려운 시장상태를 말하며, 항공산업의 경우 일반적인 네트워크 산업과 마찬가지로 대규모 설비투자가 필요하고 높은 고정비용과 규모의 경제가 뚜렷한 특성을 갖고 있으며 네트워크효과도 강하게 나타나 비대칭적 규제가 필요한 대표적인 산업이라고 할 수 있다. 우리나라 경제당국은 평균비용이 장기적으로 하락하는 대규모 자본산업에서 자연독점이 발생할 경우, 그 피해는 자연히 소비자에게 돌아 갈 것이며, 미국과 EC의 경쟁법상의 유효경쟁의 개념으로 제시되고 있는 요소들을 보면 주로 어느 한 기업이 시장지배력을 행사하는 시장상황을 나열하여 규제함으로써 최대의 이익이 소비자에게 돌아가도록 규제하고 있다. 항공운송사업은 자본집약적 서비스산업으로 일반서비스 산업에 비해 상대적으로 일정수준까지 자본투자가 전제되어야 하는 자본집약적 특성을 지닌다. 따라서 항공운송산업의 성패는 대규모 자본을 통한 운송능력에 대한 효율화 정도에 따라 결정된다. 여기에 시장에 진입 시기와 독점 유지기간도 중요한 역할을 한다. 또한 항공운송산업은 정부의 면허사업으로 선발항공사가 수익노선을 선점하여 운항할 경우, 정부의 별도 허가에 의하여 복수취항이 이루어진다고 하더라도 운항편수 및 고객 선호 시간대를 미리 선점할 수가 있어 후발항공사에 비해 우월적 지위를 갖게 되어 공정경쟁이 극히 어렵다고 할 수 있는데, 이는 수십년간 아시아나의 압도적인 서비스/안전에 대한 높은 평가에도 불구 대한항공과 아시아나의 격차는 2000년 이후 일정하게 유지되고 있다는 점에서 확인할 수 있다. 국내 항공운송산업은 면허산업으로, 운수권의 확보에 따라 항공사의 매출 차이가 결정되는 바, 항공운송산업에서의 유효경쟁을 확보는 1차적으로는 정부의 운수권 배분을 통하여 실현되며 양사의 운수권 배분내역에 의하면 선발사업자에 대한 유효경쟁정책이 실현되지 않고 있다고 할 수 있다. 대부분의 노선에서 복수취항이 허용된다고 하더라도 강력한 스케줄, 가격(운임) 경쟁력, 선발항공사의 이점, 고객 선호도의 미반영 등으로 인하여 공정한 경쟁이 이루어지지 않을 가능성이 매우 높다. 이처럼 평균비용이 장기적으로 하락하는 항공산업에서 선발항공사에 대한 쏠림 현상이 가중된다면 향후 10년내에 국내 항공운송산업에 자연 독점이 발생할 가능성은 매우 크며 그 피해는 소비자에게 돌아갈 것이 자명하다. 결국 우리나라의 항공운수산업에서의 유효경쟁환경을 조성하기 위해서는 운수권 배분 절차에서의 비대칭규제의 원리가 상당기간 적용되어야 하며, 복수취항이 허용된 노선에서도 후발사업자가 공정하게 경쟁할 수 있도록 비대칭규제방안이 강구되어야 한다. 뿐만아니라 보충적으로 공정거래법상의 시장지배적 지위의 남용규제와 같은 비대칭규제도 강력하게 집행되어야 할 것으로 판단된다.

• Research in Plant Disease
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• v.14 no.2
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• pp.117-121
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• 2008

To determine the economic threshold level of Meloidogyne incognita on cucumber in greenhouse conditions, cucumber seedlings(Cucumis sativa L. cv. 'Super Manchon') grafted on 'Jangsushintozoa'(Cucurbita maxima x Cu. moschata) were planted in wooden boxes($30{\times}40{\times}15cm,\;L{\times}W{\times}D$) under a plastic house in August 01 and harvested from Sep. 01-Oct. 30, 2006. The initial nematode population densities(Pi) in the wooden boxes were adjusted to 0, 10, 30, 100, 300, and 600 second-stage juveniles(J2)/100 $cm^3$ soil. The relationship of total fruit yield to Pi level could be adequately described by a linear regression equation, $Y=0.82-0.04{\cdot}Log_{10}$(Pi+1). Initial nematode densities(Pi) before planting in excess of 5 J2/1,000 $cm^3$ soil caused in total yields loss that is equivalent to the costs of granular nematicide application; Pi level in excess of 25 J2/1,000 $cm^3$ soil caused in total yields loss that exceed the costs for application of fumigants at current control costs. We propose two different management strategies depending on nematode densities, (i) application of non-fumigant granular nematicides for M. incognita Pi level of 5 J2/1,000 $cm^3$ soil and (ii) fumigant treatment with Pi level over 25 J2/1,000 $cm^3$ soil. Soil samples to determine population density of Meloidogyne spp. for advisory purposes should be taken several months before planting time, which allows a period of time enough for implementing management procedures.

• Journal of Korean Society of Forest Science
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• v.87 no.3
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• pp.328-333
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• 1998

To obtain basic information for establishing a pest control strategy for insect pest management system, changes in the population densities of the black-tipped sawfly(Acantholyda posticalis posticalis Matsumura) and damage patterns in tree growth were investigated in national forests in Hoigok-ri, Kapyung-gun, Kyunggi-do, where the pest control measures were taken. The results obtained were as follows ; 1. The larval density in the soil of the forests where the insecticides were applied have been kept below economic threshold for about 7 years. The density was the highest in the middle of slopes and similar to the level of the early stage of the insect outbreak. 2. After the pest control by insecticides, reduction in tree height and diameter growth lasted for 2-3 years in trees defoliated by over 70%. 3. The diameter growth of the trees damaged by black-tipped sawfly recovered faster in upper stem than in the lower. 4. volume growth of the trees defoliated over 70% by the insect decreased for three to four years. The volume loss of trees defoliated by 70% and 90% was 19.6% and 54.0%, respectively. 5. Maintaining the rate of defoliation below 50%, which is the economic threshold, by chemical control measures had an effect of reducing the tree volume loss by $40m^2/ha$ as compared with a stand defoliated by 90%.

• Korean journal of applied entomology
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• v.45 no.3 s.144
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• pp.333-337
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• 2006

The damage aspects of soybean by common cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) at different larval density and different growth stage of soybean were studied in soybean field. The percent yield reduction(Y) of soybean infested by different densities of S. litura (X, no. of larvae/plant) under outdoor conditions for a three week period were estimated by the following equations: (1) Y = 1.655X - 6.025 ($R^{2}=0.952$) for the R1 (flowering stage); (2) Y = 0.725X - 0.475 ($R^{2}=0.986$) for the R3 (beginning pod stage); and (3) Y = 0.635X - 1.325 ($R^{2}=0.986$) for the R5 (beginning seed stage). Based on the relationships between the densities of S. litura larvae and the yield index of soybean, the number of larvae (2nd-3rd instar) which caused 5% loss of yield (Tolerable injury level) was estimated to as approximately 6.7 for the R1, 7.5 for the R5, and 10.0 per plant for the R5, respectively. Average soybean leaf areas consumed by 1st, 2nd, 3rd, 4th, 5th and 6th larvae of Spodoptera litura during 24 hr at $28^{\circ}C$ was 0.3, 0.7, 2.6, 4.0, 20.1, and $55.8\;cm^{2}$, respectively.

• Explosives and Blasting
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• v.31 no.1
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• pp.11-22
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• 2013

This study compared and analysed ground vibration, size of underwater background noise in fish farms and underwater object noise of blasting and obtained ground vibration prediction equation through a regression analysis and correlation equation between underwater object noises in order to predict degrees of underwater noise in blasting and organize underwater noise control regulations. Before the study, when background noise of fish and shellfish farms with different conditions was measured, levels of background noise were different according to environmental characteristics of each farm. Ground vibration which causes underwater noise was measured to obtain a correlation equation between ground vibration and underwater object noise. Therefore, if underwater noise is predicted for each construction with a use of a correlation and permissible standards appropriate for each condition are applied for design and construction, financial loss from damages to fish and shellfish caused by development of insufficient technological and engineering logic can be prevented and successful construction with safety of underwater creatures guaranteed can be achieved.

• KEPCO Journal on Electric Power and Energy
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• v.3 no.2
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• pp.107-111
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• 2017

The reliability on high cycle fatigue damage mechanism for new blades manufactured by reverse-engineering is demonstrated by success-run test. Turbine blades always experience various dynamic loads in turbine operation, as well as being in resonance condition and forced by fluid-induced vibrations mostly during run-up/down, which may accumulate high cycle damage to the blades. The accidents caused by blade failure especially incur not only a lot of troubles to the machinery but also huge financial losses. Therefore it is necessary to verify the reliability of blades in advance for the safe use. The success run test for the reliability demonstration is designed and performed for the new blades using the technique known as resonant high cycle fatigue testing.