• Bulletin of the Korean Mathematical Society
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• v.52 no.4
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• pp.1069-1076
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• 2015

In this paper, a two species competitive model with stage structure and harvesting is investigated. By using the differential inequality theory, some new sufficient conditions which ensure the permanence of the system are established. Our result supplements the main results of Song and Chen [Global asymptotic stability of a two species competitive system with stage structure and harvesting, Commun. Nonlinear Sci. Numer. Simul. 19 (2001), 81-87].

• Kyungpook Mathematical Journal
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• v.47 no.1
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• pp.31-56
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• 2007

In this paper, we consider a delay differential equation model of two competing species with harvesting of the mature and immature members of each species. The time delay in the model represents the time from birth to maturity of that species, which appears in the adults recruitment terms. We study the dynamics of our model analytically and we present results on positivity and boundedness of the solution, conditions for the existence and globally asymptotically stable of equilibria, a threshold of harvesting, and the optimal harvesting of the mature populations of each species.

• Horticultural Science & Technology
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• v.31 no.5
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• pp.573-579
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• 2013

This study was conducted to investigate optimal harvesting stage and the effects on cut roses of Korean cultivar harvested at different stages. Cut roses are harvested at three different flowering stages. The optimal harvesting stage of cut roses was different depending on varieties. The vase life of standard type 'Pink Song' and spray type 'Peace One' was extended when they were harvested in one and three stages, respectively. The vase life was generally increased when the cut roses were pretreated with a solution containing 2% sucrose + $200mg{\cdot}L^{-1}$ aluminum sulfate + $200mg{\cdot}L^{-1}$ $Mg(NO_3)_2$ + $50mg{\cdot}L^{-1}$ $CaCl_2$ as compared to the control regardless of the harvesting stage. And this pretreatment solution improved the flower quality of cut roses bred in Korea. But the effects of pretreatment were varied depending on the harvesting stage.

• Korean Journal of Agricultural Science
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• v.31 no.2
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• pp.149-160
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• 2004

This study had carried out an analysis of leaf tobacco production cost by cost items, growing stages, and farm sizes per 10a to provide the basic data for determination of the purchasing price of leaf tobacco by KT&G. Considering the survey results of 12 tobacco farm households, the composition rates of production cost by items revealed as 7-10% for land service, 5-22% for depreciation, 13-25% for material costs, 50-65% for labour cost respectively. The production cost of leaf tobacco by growing stages were shown as 15.3% in nursery bed period, 32.3% in main growing period in field, 30.8% in harvesting period and 21.6% in packing period. The magnitude of wage expenditure was appeared as harvesting stage, packing stage, growing stage on main field and nursery bed stage in order. The amount of material costs were revealed as the growing stage in main field, harvesting stage, nursery bed stage and packing stage respectively. The production costs of leaf tobacco per 10a by farm sizes were shown as 1,615,879won for small farm, 1,446,896won for medium farm and 1,454,408won for large farm respectively. The production cost of leaf tobacco had shown decreasing tendency according to increasing farm sizes. To promote the international market competitiveness of leaf tobacco producing farms, labour saving production technologies and cost effective farm size to decrease tobacco production cost should be developed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.429-432
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• 2017

In this paper, a full - wave rectifying harvesting circuit with a high-performance comparator is designed. Designed circuits are divided into Negative Voltage Converter and Active Diode stages. The comparator included in the active diode stage is implemented as a 3-stage type and divided into pre-amplification, decision circuit, and output buffer stages. The main purpose of this comparator is to reduce the propagation delay and improve the voltage and power efficiency of the harvesting circuit. The proposed circuit is designed with magna $0.35{\mu}m$ CMOS process and its operation is verified by simulation. The chip area of the designed energy harvesting circuit is $900{\mu}m{\times}712{\mu}m$.

• The Research Journal of the Costume Culture
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• v.26 no.4
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• pp.503-518
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• 2018

The purpose of this study is to illustrate the design of safety suits based on energy-harvesting technology, particularly targeting street cleaners who must work at night with high mobility. The design focuses on applying lightweight energy-harvesting tools and illuminant into the wear. The design development reflects feedback from testers collected via survey constituting a key methodology. The development process has two main stages. Each stage uses a process of design prototyping, internal examination, test sampling, test wearing, and wearers' feedback via survey that consists of questions on visibility, wearing convenience, and washability. The first stage results show the design of safety suits with energy-harvested LED illuminant inserted and the survey results collected from street cleaners dressed in 4 sample and 80 actual suits in total. Improved based on the first-stage survey results, the second stage designs the suits with detachable energy-harvested EL tape. From these 5 sample and 30 actual second-stage suits, the additional survey indicates that this second-stage design facilitates more visibility and convenience in washing and wearing than the first-stage design. Accordingly, one can expect that this new design can apply not only to safety suits for night workers but also to handicapped or outdoor sportswear applications in the future.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.4
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• pp.243-250
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• 2020

Energy harvesting is a recent technology involving the harvest and utilization of extremely small surrounding energy. Energy harvesting research is conducted in various fields. Triboelectric nanogenerators (TENGs) are energy harvesting technologies that use static electricity generated by physical movement or friction. Although TENGs generate output power in microwatt levels, they experience high internal impedance compared with other energy harvesting generators, thereby making the continuous transfer of electric power to loads difficult. This study proposes a power management system for TENGs that consists of three stages, that is, an AC/DC rectifier, an impedance coupler switch with a capacitor bank, and a DC/DC converter. In addition, the selection method of the AC/DC rectifier and DC/DC converter is proposed to maximize the amount of power transferred from energy harvesting areas. Furthermore, the impedance coupler switch and capacitor bank are discussed in detail. The validity and performance of the proposed three-stage power management system for TENGs are verified using a prototype system.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.144-144
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• 2022

The amount of required forage is increasing by 20% every year in South Korea, but the cultivation area for forage production is limited. The yield ability of triticale forage is the highest among the winter forage crops including rye and the crop has cold tolerance within the average low temperature of -10℃ in January. Therefore, this study analyzed effects of sowing and harvesting times on feed value and quality for efficiently using and supplying triticale as livestock feed. Seed of the triticales, 'Joseong' was sown in 2021 fall (October) and 2022 spring (March). The triticales were harvested according to growth stages: seedling stage, booting stage, heading stage, 10 days after heading, and 20 days after heading. Moisture contents of each harvested triticales were adjusted to about 60%, and then the triticales were fermented for 40 days at room temperature under anaerobic conditions as silage. We have analyzed pH and organic acid to determine the feed value and quality of each silage. The contents of lactic acid in silage ofthe triticale harvested at the seedling stage of both fall and spring-sown (1.61%, 1.63%) were the highest among all of the silages; the booting stage (0.75%, 1.33%), the heading stage (0.50%, 0.69%), 10 days after the heading stage (0.31%, 0.42%), and 20 days after heading stage (0.22%, 0.40%). Such as the contents of lactic acid in the silages, and the pH value of the silages The pH value in both the fall- and spring-sown became lower as the triticale was grown up: seedling stage (7.05, 6.85), booting stage (6.21, 6.75), heading stage (6.18, 6.28), 10 days after heading stage (6.22, 6.17), and 20 days after heading stage (6.15, 5.81). Taken together, the results showed that the feed value and quality of triticale silage were more affected by harvesting time than sowing time.

• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.311-319
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• 2018

Purpose: The aim of this study is to develop a small combine for harvesting miscellaneous cereal crops. Methods: A prototype small combine was designed and constructed. Its specifications and basic performance were investigated. Results: The prototype small combine for harvesting miscellaneous cereal crops was designed and constructed to reflect similar specifications as those of the conventional combine. The prototype small combine comprises a diesel engine with the rated power/speed of 22.0 kW/2,600 rpm, three-stage primary and two-stage speed range transmission shifts, and a double acting threshing part. The maximum travel speeds of the prototype combine are approximately 0.72 m/s, 2.50 m/s, 0.30 m/s at the low, high speed range shifts in the forward direction, and while traversing in the reverse direction, respectively. The minimum radius of turning was approximately 1.50 m. In a static lateral overturning test, the prototype combine overturned neither to the right nor to left on a $30^{\circ}$ slope. The results of an oilseed rape harvesting test included the maximum operating speed of 0.32 m/s, the grain loss ratio of approximately 9.0%, and the effective field capacity of approximately 10.3 a/h. Additionally, among the outputs in grain outlet, the whole grains, damage grains, and materials other than grain (MOG) ratios accounted for 97.4%, 0.0%, and 2.6%, respectively. Conclusions: The prototype small combine for harvesting miscellaneous cereal crops indicates good driving ability and stability. The results of the oilseed rape harvesting test reveal that the harvesting performance must be enhanced such that the separating and cleaning parts are more suitable for each type of crop, thus reducing grain loss and foreign substances among the outputs in grain outlet. An improved small prototype combine could be used effectively to mechanize the harvesting of miscellaneous cereal crops in small family farms or semi-mountainous areas.

• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.320-330
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• 2018

Purpose: The aim of this study was to investigate the harvesting performance of a prototype small combine for buckwheat and adlay. Methods: The prototype small combine was designed and constructed. Its ratio of grain loss, ratio of output components in the grain outlet, and field capacity for harvesting buckwheat and adlay were analyzed through field tests. Results: The prototype small combine required a working width of about 0.6 to 0.7 m to harvest buckwheat. The maximum travel speed was about 0.36 m/. The total ratio of grain loss was about 21.6%, which consisted of 8.8% at the header and 12.8% at the dust outlet. The grain and the material other than grain (MOG) ratios at the grain outlet were 94.1% and 5.9% respectively. In the case of adlay harvest, the maximum working width was about 1.2 m, that is, two rows. The range of maximum travel speed was about 0.45 to 0.46 m/s. When adlay was harvested in one row, the total ratio of grain loss ranged from 36.3 to 42.8% according to the cutting height. The cutting height of 30 cm resulted in a higher total ratio of grain loss than 60 cm and 90 cm. When the cutting height was 60 cm, there was no significant change in the total ratio of grain loss according to the number of working rows and the stage of the primary transmission shift. The total ratio of grain loss ranged from 35.2 to 37.7%. The grain and the MOG ratios at the grain outlet ranged from 93.1 to 95.8% and from 4.2 to 6.9%, respectively. No significant difference was observed in relation to cutting height, number of working rows, and the stage of the primary transmission shift. Conclusions: The prototype small combine for harvesting miscellaneous cereal crops showed good potential for the efficient harvesting of buckwheat and adlay. However, to improve the harvesting performance, there seems to be a need to develop new crop varieties suitable for machine-based harvesting and improve the transmissions, reels, separation/cleaning systems.