• International Journal of Fuzzy Logic and Intelligent Systems
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• v.5 no.4
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• pp.316-321
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• 2005

We designed and implemented fish robots for various purposes such as autonomous navigation, maneuverability control, posture balancing and improvement of quick turns in a tank of 120 X 120 X 180cm size. Typically, fish robots have 30-50 X 15-25 X 10-20cm dimensions; length, width and height, respectively. It is essential to have the ability of quick and smooth turning to avoid collision with obstacles or walls of the water pool at a close distance. Infrared distance sensors are used to detect obstacles, magneto-resistive sensors are used to read direction information, and a two-axis accelerometer is mounted to compensate output of direction sensors. Because of the swing action of its head due to the tail fin movement, the outputs of an infrared distance sensor contain a huge amount of noise around true distances. With the information from accelerometers and e-compass, much improved distance data can be obtained by fuzzy logic based estimation. Successful swimming and smooth turns without collision demonstrated the effectiveness of the distance estimation.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.5
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• pp.435-442
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• 2014

This paper describes an improved design model that can be used to configure a non-contact pneumatic device to turn a large sheet at the in-line system. For rotational moving in the conveyor system, the conventional method is to turn the system itself. The improved non-contact pick-up system mainly uses 8 pairs of L-shaped latches and 12 swirl type heads. It is positioned above the upward air flow table. This system performs the non-contact gripping and side-edge contact support in the vertical and rotational directions to hold the self-weight of a large flat sheet. A non-contact air head can exert a sufficient gripping ability at 4N lower than the standard working pressure. The side latches support 60% of the lifting force required. Through structural and flow analysis, the working conditions were simultaneously considered in accordance with the deflection and flatness of the glass.

• Proceedings of the Korean Society of Crop Science Conference
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• 1998.10a
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• pp.210-232
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• 1998

Tong-il, the high-yielding rice variety bred on early 1970, effected a turning point in modern rice production in Korea. As rice production reached the highest record yield in 1978 with HYV, Korea achieved self-sufficiency in domestic supply of rice (or the first time in (her own) history, HYV required high input of fertilizers and pesticides for proving its yielding ability and needed new techniques such as early nursery-planting to prevent chilling damage. But, farm economy did not follow the successful achievement of rice production because of increased farming cost and inflation.'Tong-il variety has been replaced by new high-yielding Japonica varieties from 1980 when record-low-temperature during summer months had persisted. Also, the cooked rice of Tong-il variety did not agree with the appetite of Korean people. Though the hectarage of Tong-il rice did reduce, farmers applied the same high-input cultural techniques for new Japonica cultivars as did for Tong-il variety. Heavy application of nitrogen fertilizer contaminated surface and ground water with nitrate ions while phosphorous fertilizer was blamed for algae pollution. Frequent spray of pesticide and herbicide reduced significantly the biotic population in paddy ecosystems including insects and soil microorganisms. The new technologies of the 21st century must be directed to produce safe food, to save natural resources, and to preserve a clean environment for human welfare. We need low-input sustainable farming techniques to provide high-yielding crops and to preserve a healthy ecosystem.

• International conference on construction engineering and project management
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• 2017.10a
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• pp.153-158
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• 2017

Procurement system of public construction projects in Japan is changing with diversity in rapid pace. The quality assurance and risk management of construction projects should be more certain as the projects are turning into larger scale and more complexed. The clients in the public sector will want to make the relation of responsibility among the client, the designer (architects and engineers), and contractor clearer in terms of role and risk. Public-Private Partnership (PPP) is one of the methods for collaboration of the public sector and the private sector in public construction projects where the public utilizes the ability and suggestion of the private. Private Finance Initiative (PFI), Design-Build-Operate (DBO), market testing, designated manager system, outsourcing of tasks in local governments are well-known as examples of PPP in Japan. Indeed, there is an obvious trend that Design-Build (DB) is adopted in public construction projects in many countries including Japan. In this paper, the public construction projects in various procurement systems are surveyed and analyzed. They are not limited within the traditional procurement, Design-bid-Build, a separate order system of design and construction. Design-Build or PFI are adopted. In particular, contract by wide range including maintenance of equipment can be found. On the other hand, modification from originally typical PFI is taking place, such as concept design and project finance are removed from the roles and the tasks of the special purpose company (SPC) in PFI. Standard roles and tasks in a construction project are modeled in this paper.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.4_2
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• pp.825-832
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• 2024

Traditional cars have a structure that steers the front wheels to change their direction so they have difficulties in performing parking motion, especially in a narrow space. As electric vehicles developed, robotics technology especially omni-directional mobile robot technology began to be incorporated into the automobile field. Omni-directional mobility and special turning movements are particularly useful for parking cars. In this paper, we propose a four-wheeled mobile robot. The proposed robot has a structure that can combine or separate robot body and robot wheel parts by using electric brakes. The proposed robot has omni-directional mobility and has the ability to rotate around an arbitrary point. Due to these omnidirectional and rotational characteristics, the proposed robot allows for various types of movements when applied to a car. In particular, parking is performed in a simple and intuitive manner that does not require complicated path planning. We implemented the proposed four-wheeled robot and showed its effectiveness by conducting several parking experiments.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.1
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• pp.13-24
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• 1994

Purse seiner detects a fish school navigating in full speed with the aid of fish finder, sonar, helicopter, etc., and casts a net quickly to enclose the fish school in purse seine net according to the movement of the fish school, wind, and current. At this moment, if the time of casting a net, direction, speed, and turning circle are net suitable, it is unavoidable to lose fish school founded with hard efforts and we only consume our efforts of casting and hauling the net. Therefore, in order to enclose the fish school to enhance the amount of fish for each casting, the author investigated the type of ships equipped with purse seiners and examined maneuvering tests so that we provide some basic information to figure out the ability of steerage correctly. The results obtained are summarized as follows: 1. Block coefficients of pelagic tuna purse seiners with gross tonnage between 500 and 1500 tons are recorded between 0.50 and 0.55 which are greater than those of off shore purse seiners recorded as between 0.44 and 0.54 and less than those of various cargo ships recorded as between 0.56 and 0.84. 2. L/B, L/D, B/D, B/T, and T/D of the class of gross tonnage between 75 and 130 tons are respectively 4.49, 11.00, 2.45, 2.85 and 0.86 as their average and those of the class of between 500 and 1500 tons are 4.89, 10.53, 2.15, 2.73 and 0.75 respectively, which are quite different from those of various cargo ships recorded as 6.0~7.5, 11.0~12.0, 1.6~2.0, 2.2~2.8 and 0.65~0.75 respectively. 3. Rudder area ratio of purse seiners of the class of between 75 and 130 tons is 1/24~1/31 and that of the clase of between 500 and 1500 tons is 1/36~1/42 which is greater than that of various cargo ships recorded as 1.45~1.75. 4. On speed-length ratio of purse seiners. 111 Dong-a has the biggest value 2.94 the class of 130 tons has 2.52 the class of between 75 and 100 tons has 2.30~2.35 and the class of between 500 and 1500 tons has 1.99~2.05. 5. Turning circle of stern trawlers Pusan 404 and Haelim 3 are measured as below according to rudder angles 5$^{\circ}$, 15$^{\circ}$, 25$^{\circ}$ and 35$^{\circ}$ respectively. Advances are 11.3~13.6, 6.0~7.1, 3.6~4.8 and 2.5~3.5 times of LPP respectively. Tactial diameters are 15.2~18.6, 6.9~8.0, 4.2~4.9 and 2.9~3.5 times of LPP. Purse seiner 111 Dong-a with rudder angle 35$^{\circ}$ has a good yaw with quick responsibility since its advance is 2.2~2.3 times of LPP and since its tactial diameter is 2.0~2.1 times of LPP. 6. In full ahead going of purse seiner 111 Dong-a, it takes about 2 minutes and 10.6 times of LPP from the reverse turning its engine into full astern to the ship speed 0. In its full astern going, it takes about 1 minute and 5.1 times of LPP from the reverse turning its engine into full ahead to the ship speed 0. In its full ahead going, it takes about 2 minutes and 50 seconds and 12.3 times of LPP from stopping its engine to the dead slow ahead speed 3.2 knots.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.851-860
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• 2020

With an increase in the aging population and a rising social interest in health and welfare, studies to improve healthcare in the elderly are being actively conducted. This study attempted to improve the current design and manufacture of elevating electric wheelchairs to enhance user safety and convenience. Seat design based on the user's body shape, convenience while boarding or alighting, caster turning radius and, safety and stability features that prevent shaking when the user gets up or sits down were improved. A driving experiment was conducted to evaluate the operation of the indoor electric wheelchair designed and manufactured with these additional functionalities. During the test, the performance parameters evaluated were continuous driving time, turning radius, maximum lifting and lowering load, maximum lifting height, noise level, minimum distance sensing by the driving auxiliary sensor, ability to interact with server and app programs, and the duty cycle maximum error rate. The test confirmed that this improved electric wheelchair successfully met target parameters. In a future study, we will evaluate this improved electric wheelchair from a user's perspective for its usability parameters, such as satisfaction, convenience and stability.

• Journal of Navigation and Port Research
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• v.40 no.6
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• pp.353-360
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• 2016

The International Maritime Organization (IMO) has issued international standards for ship maneuverability and stability. These have been established to improve marine safety and influence the direction of research. The previous literature has been researched, but there are few studies on the relationship between ship maneuverability and stability. This study carried out a fundamental experiment to quantitatively evaluate that relationship. Radius of turn and maximum heel angle depending on changing were analyzed through a turning test using a free running model ship. The test results show the change tendency of decreasing turn radius and increasng maximum heel angle according to a GM decrease. A rough estimate equation is proposed to predict the change tendency on radius of turn and angle of maximum heel as GM decreases. Many ships can suddenly experience reduced GM due to unexpected reasons during sailing. The results in this study can be used as fundamental data to estimate a ship's tactical turn diameter and variable heel angle for steering as GM decreases.

• Journal of the Korean Society for Precision Engineering
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• v.3 no.2
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• pp.62-75
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• 1986

An experimental investigation of the machining characteristics such as cutt- ing resistance, surface roughness and tool wear in turning the test pieces of SM45C steel with both coated and uncoated carbide tool tips under various cutting conditions was conducted. Also a specially designed simple vibration damping device was experimentally evaluated for its effectiveness on machined surface roughness and a vibration test was conducted to confirm its ability to reduce the amplitude. Based on these tests finding, the following conclusions are made; 1. The cutting resistance($\textrm{p}_{1}$) increases as the depth of cut(d) increases at fixed feed rate(f) over the cutting speed(v) range of 43-226 m/min and p decreses about 18% average when V is increased for fixed d and f. At V= 226m/min, $\textrm{p}_{1}$/for A, C tips are about the same level but $\textrm{p}_{1}$ for B tip is 15% less than A, C tips. 2. The specific cutting resistance(Ks) at V=226 m/min was derived for A, B, C tips respectively and the value of Ks for B rip is about 20% less than A, C tips. 3. The surface roughness(Ra) improves significantly as the cutting speed(V) is increased and this effect was greater when V>100 m/min. On the other hand, Ra deteriorates as the feed rate(f) is increased and this trend was accelerated when f>0.3 mm/rev. With regard to the difference of Ra values among A, B, C tips, at V=226m/min, d=0.4mm, and f=0.31-0.61mm/rev, Ra values for B.C tips are about 17% less than tip A. 4. The experimental tool wear equations were derived for A, B, C tips and from these equations, the tool life($\textrm{T}_{\textrm{L}}$) baced on the I.S.O. criteria was calculated to be $\textrm{T}_{\textrm{L}}$<$\textrm{T}_{\textrm{LB}}$<$\textrm{T}_{\textrm{LC}}$ for both flank wear($\textrm{V}_{\textrm{B}}$) and boundary wear($\textrm{V}_{\textrm{N}}$). Hence, the coated tips are superior to the uncoated tip and tip C is considered to be the best. 5. The cutting resistance may be slightly reduced and the surface rounghness improved when the damper is used especially when V>100 m/min. Therefore this damping device is considered to be effective and practical. The experimental surface roughness equations were also derived. Based on the vibration test, it is established that the surface roughness improvement was the result of amplitude reduction made possible by the damper.

• Korean Journal of Poultry Science
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• v.26 no.1
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• pp.43-50
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• 1999

The features of special brand eggs are growing more and more diverse and it is hard to draw a clear distinction between these and ordinary (no-brand) eggs. Special brand eggs range from those with objectively recognizable characteristics to those given only an unsubstantial product image and price differentials are among them great, too. The relation between product features and prices is unclear. Special brand eggs are the commodity whose characteristics are the vaguest of all livestock products. Farm's brand eggs produce a high profitability to producers is they are directly sold to consumers, by, for example, home-delivery service. But if they are sold to supermarkets, etc., producer's (poultry farmer's) income becomes lower by the amount of distributors' margin, reducing the profitability substantially. Thus how to increase the ration of retailing is important for farmers to secure a high profit. The sales strategies of poultry are the combination of two elements, that is, new product development (product differentiation) and creation of new market. But it is difficult for special brand egg producers to develop products with clear characteristics (use value) distinct form ordinary eggs and so these producers depend on the factors of appearance, such as the color of egg shells and package. Special brand eggs manage to keep their marketable value by the combination of the few product features and product image. Thus NB eggs from feed producers have a great market-ability since they can take advantage of the power of patents and TV commercials. However, market differentiation affects profitability much more than product features and price gaps are very wide between directly sold and wholesaled eggs. The producers of special brand eggs have come to the turning point where they have to decide whether they will content with being the subcontractors for NB and PB eggs or they will continue to keep their independence in production and marketing.