• Journal of Advanced Marine Engineering and Technology
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• 제19권2호
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• pp.1-9
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• 1995

The processing paper has devoted to the theory of the flow equations, the basic derivative procedure, the meaning of a valve flow coefficient $C_v$, the valve Reynolds R$R_{ev}$ and its application for liquid control valves, which applicable under the condition of a non-critical flow and the case of piping geometry factor $F_p$=1.0. However there is no information on the effects of fittings, a critical flow and the flow resistance coefficient of a valve equivalent to that of pipe which is conveniently used in the piping design. Since the piping systems of plants or ships generally contain various fittings such as expanders and reducers due to different size between pipes and valves and there may occur a critical flow, that a mass flowrate is maintained to be constant, due to the pressure drop in a piping when a liquid is initially maintainder ar a saturated temperature or at nearby corresponding to upstream pressure, system designer should have a knowledge of the effect to flow due to fittings and the critical flow phenomenon of a liquid. This study is performed to inform system designers with the critical flow phenomenon of a liquid, a valve resistance coefficient, a valve geometry factor and their applications.

• Korean Journal of Pharmacognosy
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• 제39권3호
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• pp.260-264
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• 2008

Eight compounds were isolated from the EtOAc soluble fraction of Euphorbia supina MeOH extract as the radical scavengers for antioxidant activity. Their structures were identified as kaempferol (1), quercetin (2), juglanin (3), avicularin (4), astragalin (5), isoquercitrin (6), hyperin (7), and nicotiflorin (8) by spectroscopic analysis. The antioxidant activity was evaluated by the ORAC (oxygen radical absorbance capacity) assay, which measures scavenging activity against peroxy radicals induced by 2,2'-azobis (2-methylpropionamidine) dihydrochloride, and the ORAC value is expressed as relative trolox equivalent. Compounds 4, 6, and 7 exhibited potent antioxidant activity, whereas the other compounds showed weaker activity than trolox.

• Journal of Fisheries and Marine Sciences Education
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• 제15권2호
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• pp.135-144
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• 2003

1. The appearance of fisheries animals and plants of investigation areas were fishes, 20 species; algae, 9 species; molluska, 6 species; arthropod, 12 species; echinoderm, 5 species by confirmed appearance species. 2. The C.P.U.E by trap(1pcs of trap) were 3.95 species and weight of 2,098g, mainly catching species are greenling and jacopever(94.16%). The C.P.U.E by long liner(long liner 1coil, 100pcs) were 11.7species and weight of 6,418g, It occupied jacopever(35.63%) greenling(20.78%), bastard halibut(20.31%). The C.P.U.E of appearance species gill net(ipcs of gill net) were 5.05species and weight of 3,050g, It occupied jacopever(39.63%) greenling(29.83%), bastard halibut(17.47%). 3. The results of comparative analysis and natural species and stocked species, in case of bastard halibut, jacopever species were occupied species(83.33~92%), weight(86.86~96%). The stocked species were occupied species of 8.00~16.67%, weight of 4.00~13.14%. Provided the stocked projets were enacted effectively in future. The density of dwelling of stocked species were increase. Also, it will be contribute to the increase of fishermens income.

• Journal of Ocean Engineering and Technology
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• 제32권4호
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• pp.253-260
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• 2018

Recently, the application of non-steel materials in ships and offshore plants is increasing because of the development of various nonlinear materials and the improvement of performance. Especially, hyper-elastic materials, which have a nonlinear stress-strain relationship, are used mainly in marine plant structures or ships where impact relaxation, vibration suppression, and elasticity are required, while elasticity must be maintained, even under high strain conditions. In order to simulate and evaluate the behavior of the hyperelastic material, it is very important to select an appropriate material model according to the strain of the material. This study focused on the selection of material models for hyperelastic materials, such as rubber used in the marine and offshore fields. Tension and compression tests and finite element simulations were conducted to compare the accuracy of the nonlinear material models due to variations in the stretch ratio of hyper-elastic material. Material coefficients of nonlinear material models are determined based on the curve fitting of experimental data. The results of this study can be used to improve the reliability of nonlinear material models according to stretch ratio variation.

• Journal of Advanced Marine Engineering and Technology
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• 제28권8호
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• pp.1299-1312
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• 2004

This paper suggests the simple form of a fuzzy PID controller and describes the design principle, tracking performance, stability analysis and changes of parameters of a suggested fuzzy PID controller. A fuzzy PID controller is derived from the design procedure of fuzzy control. It is well known that a fuzzy PID controller has a simple structure of the conventional PID controller but posses its self-tuning control capability and the gains of a fuzzy PID controller become nonlinear functions of the inputs. Nonlinear calculation during fuzzification, defuzzification and the fuzzy inference require more time in computation. To increase the applicability of a fuzzy PID controller to digital computer, a simple form of a fuzzy PID controller is introduced by the backward difference mapping and the analysis of the fuzzy input space. To guarantee the BIBO stability of a suggested fuzzy PID controller, ‘small gain theorem’ which proves the BIBO stability of a fuzzy PI and a fuzzy PD controller is used. After a detailed stability analysis using ‘small gain theorem’, from which a simple and practical method to decide the parameters of a fuzzy PID controller is derived. Through the computer simulations for the linear and nonlinear plants, the performance of a suggested fuzzy PID controller will be assured and the variation of the gains of a fuzzy PID controller will be investigated.

• Journal of Advanced Marine Engineering and Technology
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• 제21권4호
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• pp.393-403
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• 1997

In this paper, we proposed an optimal identification method of identifying the membership func¬tions and the fuzzy rules for the stabilization controller of the nonlinear system by RVEGA( Real Variable Elitist Genetic Algo rithm l. Although fuzzy logic controllers have been successfully applied to industrial plants, most of them have been relied heavily on expert's empirical knowl¬edge. So it is very difficult to determine the linguistic state space partitions and parameters of the membership functions and to extract the control rules. Most of conventional approaches have the drastic defects of trapping to a local minima. However, the proposed RVEGA which is similiar to the processes of natural evolution can optimize simulta¬neously the fuzzy rules and the parameters of membership functions. The validity of the RVEGA - based fuzzy controller was proved through applications to the stabi¬lization problems of an inverted pendulum system with highly nonlinear dynamics. The proposed RVEGA - based fuzzy controller has a swing -. up control mode(swing - up controller) and a stabi¬lization one(stabilization controller), moves a pendulum in an initial stable equilibrium point and a cart in an arbitrary position, to an unstable equilibrium point and a center of the rail. The stabi¬lization controller is composed of a hierarchical fuzzy inference structure; that is, the lower level inference for the virtual equilibrium point and the higher level one for position control of the cart according to the firstly inferred virtual equilibrium point. The experimental apparatus was imple¬mented by a DT -- 2801 board with AID, D/A converters and a PC - 586 microprocessor.

• Journal of Advanced Marine Engineering and Technology
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• 제39권10호
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• pp.1011-1016
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• 2015

Gas piping systems in power plants and factories are always influenced by the mechanical vibrations of rotational machines such as pumps, blowers, and compressors. Unusual vibrations in a gas piping system influence possible leakages of liquids or gases, which can lead to large explosive accidents. Real-time measurements of unusual vibrations in piping systems in situ prohibit them from being possible leakages owing to the repeated fatigue of vibrations. In this paper, a non-contact 3-dimensional measurement system that can detect the vibrations of a solid body and monitor its vibrational modes is introduced. To detect the displacements of a body, a stereoscopic camera system is used, through which the major vibration types of solid bodies (such as X-axis-major, Y-axis-major, and Z-axis-major vibrations) can be monitored. In order to judge the vibration types, an artificial neural network is used. The measurement system consists of a host computer, stereoscopic camera system (two-camera system, high-speed high-resolution camera), and a measurement target. Through practical application on a flat plate, the measured data from the non-contact measurement system showed good agreement with those from the original vibration mode produced by an accelerator.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제48권1호
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• pp.76-81
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• 2015

The effects of temperature, photon irradiance, and photoperiod on the growth of Sargassum horneri embryos were examined for female plants collected at Chokpo in Tongyeoung, Gyeongnam Prefecture, Korea on 27 December 2011. Mature plant receptacles were detached, and fertilized eggs were cultured in the laboratory at temperatures of $5-25^{\circ}C$ with photon irradiances of $10-80{\mu}mol\;m^{-2}s^{-1}$ under 14L:10D and 10L:14D photoperiods. Germination and embryo growth were rapid at $20-25^{\circ}C$ and $40{\mu}mol\;m^{-2}s^{-1}$ under 14L:10D. The number of rhizoids in the germinated young thalli was high at high photon irradiances ($40-80{\mu}mol\;m^{-2}s^{-1}$) and $15-20^{\circ}C$. At $20^{\circ}C$ and 14L:10D, vigorous growth of main and lateral branches was observed; however, at $5^{\circ}C$ under both photoperiods, plant growth decreased markedly. In the present study, S. horneri grew well at high temperatures ($20-25^{\circ}C$) and high photon irradiances ($40-80{\mu}mol\;m^{-2}s^{-1}$) with a 14L:10D photoperiod.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• 제4권1호
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• pp.25-32
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• 1999

In order to examine the degree of heavy metal pollutions around Samcheonpo and Youngkwang power plants, marine sediment samples were analyzed to determine heavy metal contents. Some of these sediment samples were also analyzed by using of a sequential extraction technique to know geochemical forms of the metals. The results showed that the spatial distribution of heavy metals coincided very well with those of mean grain size, carbonates and organic matters. The chemical speciation data using sequential extraction analysis also showed that a considerable amount of heavy metals except for Mn were bounded in the residual fraction, which mode of occurrence of heavy metals was generally interpreted as being the result of the lithogenic origin.

• Journal of the Korean Institute of Navigation
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• 제17권1호
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• pp.61-78
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• 1993

Large offshore structure are to be considered for oil storage facilities , marine terminals, power plants, offshore airports, industrial complexes and recreational facilities. Some of them have already been constructed. Some of the envisioned structures will be of the artificial-island type, in which the bulk of structures may act as significant barriers to normal waves and the prediction of the wave intensity will be of importance for design of structure. The present study deals wave scattering problem combining reflection and diffraction of waves due to the shape of the impermeable rigid upright structure, subject to the excitation of a plane simple harmonic wave coming from infinity. In this study, a finite difference technique for the numerical solution is applied to the boundary integral equation obtained for wave potential. The numerical solution is verified with the analytic solution. The model is applied to various structures, such as the detached breakwater (3L${\times}$0.1L), bird-type breakwater(318L${\times}$0.17L), cylinder-type and crescent -type structure (2.89L${\times}$0.6L, 0.8L${\times}$0.26L).The result are presented in wave height amplification factors and wave height diagram. Also, the amplification factors across the structure or 1 or 2 wavelengths away from the structure are compared with each given case. From the numerical simulation for the various boundary types of structure, we could figure out the transformation pattern of waves and predict the waves and predict the wave intensity in the vicinity of large artificial structures.