• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.1
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• pp.1-5
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• 1984

The author carried out an experiment for the dynamical swimming force of crusian carp, Carassius carassius. The experimental water tank was made of 4mm thick transparent acryl board in the right hexahedral shape (400L$\times$240W$\times$800H mm). The water temperature in the tank ranged 20.6$^{\circ}C$ to 21.2$^{\circ}C$. The water level in the tank was maintained 70cm high from the bottom. The measurement of the swimming force was carried out by use of strain gauge. The results obtained can be summarized as follows: 1) The momentary maximum swimming force F sub(M) (g) and the sustainable maximum swimming force F sub(s) (g) can be expressed as a function of the body weight W(g). F sub(M) =1.45W, F sub(s) =0.29W where the momentary maximum swimming force means the highest value, and the sustainable maximum swimming force means the mean high value sustained for 4 to 5 seconds presented in the recording paper. 2) F sub(M) and F sub(s) can be expressed as a function of the body length L(cm). F sub(M) =0.11L super(2.63), F sub(s) =0.15L super(1.77) 3) The coefficient of hydraulic resistance for crusian carp was derived as 0.287.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.3
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• pp.214-222
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• 2010

The paper presents investigations on to which degree the sinking speed of longlines is influenced by type of bait, bait sinking orientations and anchor weights. The main aim of this study is to obtain further insight in the ocean current displacement phenomena in demersal longlining. The sinking speed is one of the main factors deciding the current displacement. In an ongoing project, sinking speed experiments with longlines with 6 kg and 10 kg anchor weights have been carried out in the Trondheim fjord. The longlines used in the first experiments were rigged without bait and hook. The results of these experiments with two different anchor weights have revealed only a slight difference in the sinking speed, except for the part near to the anchors, even though the sinking speed of longlines in general is supposed to be much influenced by the anchor weights. The reason for the obtained result is supposed to be that the experiments have been carried out at relative shallow waters. Further studies have included bait sinking experiments in the flume tank. The experiments showed that the drag coefficient of "fillet type (flat)" bait varied from 0.763 to 1.735, while it for "elliptic type" bait varied from 0.62 to 1.483. Other activities have included calculation of the sinking speed of longlines as a function of the established resistance coefficients of bait of various shape and size for commercial longlining. The calculated sinking speed of a longline with the fillet type bait was found to be 12.4 to 16.5% lower than for a longline without bait.

• Journal of the Korean institute of surface engineering
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• v.36 no.5
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• pp.357-363
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• 2003

The aim of this work is the synthesis of a-C:H films from methane gas using surface spark discharge at the atmospheric pressure. Properties of these films have been investigated as functions of energy W delivered per a methane molecule in the discharge. The method enables the coatings to be deposited with high growth rates (up to $100 \mu\textrm{m}$/hour) onto large-area substrates. It is shown that the films consist of spherical granules with diameter of 20∼50 nm formed in the spark channel and then deposited onto the substrate. The best film characteristics such as minimum hydrogen-to-carbon atoms ratio H/C=0.69, maximum hardness $H_{v}$ =3 ㎬, the most dense packing of the granules and highest scratch resistance has been obtained under the condition of highest energy W of 40 eV. The deposited a-C:H coatings were found to be more soft and hydrogenated compared to the diamond-like hydrogenated (a-C:H) films which obtained by traditional plasmaenhanced chemical vapor deposition methods at low pressure (＜10 Torr). Nevertheless, these coatings can be potentially used for scratch protection of soft plastic materials since they are of an order harder than plastics but still transparent (the absorption coefficient is about $10^4$∼$10^{5}$ $m^{-1}$ At the same time the proposed method for fast deposition of a-C:H films makes this process less expensive compared to the conventional techniques. This advantage can widen the application field of. these films substantially.y.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.212-212
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• 2014

0.04% Gd-duplex stainless steels (Gd-DSTSs) for neutron absorbing materials were inert arc-melted and poured into a Y-shape block with the size of $100{\times}100{\times}20[mm]$. The Gd-DSTS was hot rolled at $1200^{\circ}C$ followed by cold rolling to have 33% reduction. The average grain sizes of the rolling (RD), transverse (TD) and short transverse (ST) directions were 6, 7, $11{\mu}m$, respectively. The micro-hardnesses of the RD, TD and ST directions were 258.5, 292.3, 314.7 $H_V$, respectively. Corrosion potential and corrosion rate of the cold rolled Gd-duplex stainless steel in aerated artificial sea water and 0.1M $H_2SO_4$ solution were $0.2216V_{SHE}$, $0.0106A/cm^2$, $-0.0825V_{SHE}$, $0.0168A/cm^2$ for RD, $0.2210V_{SHE}$, $0.0077A/cm^2$, $0.0817V_{SHE}$, $0.0092A/cm^2$ for TD, $0.1056V_{SHE}$, $0.0059A/cm^2$, $0.0475V_{SHE}$, $0.0069A/cm^2$ for ST, respectively. The corrosion behavior depended on the texture, which were due to mainly grain boundary and minorly crystallographic texture. Friction coefficient and wear resistance were 2.07 and 0.48 mm, respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.805-812
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• 2009

Permeation water resulting in the reclaimed land of waste can possibly cause the second pollution, such as the underground water and environmental pollution. Accordingly, Liner layer has been installed in the reclaimed land of waste to block and purify permeation water and prevent this second pollution. The material used as Liner layer is the one for water resistance and that of less than permeability coefficient $1{\times}10^{-7}cm/sec$ is widely used. As it is very difficult to secure in bulk this natural clay with low permeability around the field, the suitable way to secure low permeable material is that we use blend with good watertighness by mixing it with natural soil which is spread in the site. While this mixed soil which can resist water is commonly used in the site, bentonite mixed soil which is widely used as Liner layer in the reclaimed land of waste is recognized in Liner and durability. In this study, the engineering characteristics of soil-bentonite mixed liner are investigated using the laboratory hydraulic conductivity and uni-axial strength tests. The soil used for the liner is the clay soil located near the site. Mixing ratio of the bentonite which satisfies the requirement of hydraulic conductivity is determined and the optimum mixing ratio of bentonite is recommended for the landfill. After the mixed liner is constructed using the optimum mixing ratio of bentonite, the block samples of the constructed liner are obtained and the strength tests were performed. The hydraulic and strength properties of the liner for construction of the waste landfill were both satisfactory.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.479-481
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• 2000

The effect of $Al_{2}O_{3}+Y_{2}O_{3}$ additives on fracture toughness of $\beta-SiC-TiB_2$ composites by hot-pressed sintering were investigated. The f$\beta-SiC-TiB_2$ ceramic composites were hot-presse sintered and annealed by adding 16, 20, 24wt% $Al_{2}O_{3}+Y_{2}O_{3}$(6 : 4wt%) powder as a liquid forming additives at low temperature($1800^{\circ}C$) for 4h. In this microstructures, the relative density is over 95.88% of the theoretical density and the porosity increased with increasing $Al_{2}O_{3}+Y_{2}O_{3}$ contents because of the increasing tendency of pore formation. The fracture toughness showed the highest of $5.88MPa{\cdot}m^{1/2}$ for composites added with 20wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature. The electrical resistivity showed the lowest of $5.22{\times}10^{-4}\Omega{\cdot}cm$ for composite added with 20wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature and is all positive temperature coefficient resistance (PTCR) against temperature up to $700^{\circ}C$.

• Steel and Composite Structures
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• v.35 no.4
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• pp.475-494
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• 2020

Presented are experimental results from 24 full-scale push test specimens to study the behaviour of composite beams with trapezoidal profiled sheeting laid transverse to the beam axis. The tests use a single-sided horizontal push test setup and are divided into two series. First series contained shear loading only and the second had normal load besides shear load. Four parameters are studied: the effect of wire mesh position and number of its layers, placing a reinforcing bar at the bottom flange of the deck, normal load and its position, and shear stud layout. The results indicate that positioning mesh on top of the deck flange or 30 mm from top of the concrete slab does not affect the stud's strength and ductility. Thus, existing industry practice of locating the mesh at a nominal cover from top of the concrete slab and Eurocode 4 requirement of placing mesh 30 mm below the stud's head are both acceptable. Double mesh layer resulted in 17% increase in stud strength for push tests with single stud per rib. Placing a T16 bar at the bottom of the deck rib did not affect shear stud behaviour. The normal load resulted in 40% and 23% increase in stud strength for single and double studs per rib. Use of studs only in the middle three ribs out of five increased the strength by 23% compared to the layout with studs in first four ribs. Eurocode 4 and Johnson and Yuan equations predicted well the stud strength for single stud/rib tests without normal load, with estimations within 10% of the characteristic experimental load. These equations highly under-estimated the stud capacity, by about 40-50%, for tests with normal load. AISC 360-16 generally over-estimated the stud capacity, except for single stud/rib push tests with normal load. Nellinger equations precisely predicted the stud resistance for push tests with normal load, with ratio of experimental over predicted load as 0.99 and coefficient of variation of about 8%. But, Nellinger method over-estimated the stud capacity by about 20% in push tests with single studs without normal load.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.286-294
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• 2018

Hot-press forming(HPF) steel can be applied successfully to auto parts because of its superior mechanical properties. However, its resistances to aqueous corrosion and the subsequent hydrogen embrittlement(HE) decrease significantly when the steel is exposed to corrosive environments. Considering that the resistances are greatly dependent on the properties of coating materials formed on the steel surface, the characteristics of the corrosion and hydrogen diffusion behaviors regarding the types of coating material should be clearly understood. Electrochemical polarization and impedance measurements reveal a higher corrosion potential and polarization resistance and a lower corrosion current of the Al-coating compared with Zn-coating. Furthermore, it was expected that the diffusion kinetics of the hydrogen atoms would be much slower in the Al-coating, and this would be due mainly to the much lower diffusion coefficient of hydrogen in the Al-coating with a face-centered cubic structure. The superior surface inhibiting effect of the Al-coating, however, is degraded by the formation of local cracks in the coated layer under severe stress conditions, and therefore further study will be necessary to gain a clearer understanding of the effect of cracks formed on the coated layer on the subsequent corrosion and hydrogen diffusion behaviors.

• Computers and Concrete
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• v.15 no.2
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• pp.259-277
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• 2015

The lack of experimental studies on the mechanical behavior of reinforced concrete (RC) haunched beams leads to difficulties in statistical and reliability analyses. This study performs stochastic and reliability analyses of the ultimate shear capacity of RC haunched beams based on nonlinear finite element analysis. The main aim of this study is to investigate the influence of uncertainty in material properties and geometry parameters on the mechanical performance and shear capacity of RC haunched beams. Firstly, 65 experimentally tested RC haunched beams and prismatic beams are analyzed via deterministic nonlinear finite element method by a special program (ATENA) to verify the efficiency of utilized numerical models, the shear capacity and the crack pattern. The accuracy of nonlinear finite element analyses is verified by comparing the results of nonlinear finite element and experiments and both results are found to be in a good agreement. Afterwards, stochastic analyses are performed for each beam where the RC material properties and geometry parameters are assigned to take probabilistic values using an advanced simulating procedure. As a result of stochastic analysis, statistical parameters are determined. The statistical parameters are obtained for resistance bias factor and the coefficient of variation which were found to be equal to 1.053 and 0.137 respectively. Finally, reliability analyses are accomplished using the limit state functions of ACI-318 and ASCE-7 depending on the calculated statistical parameters. The results show that the RC haunched beams have higher sensitivity and riskiness than the RC prismatic beams.

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.439-443
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• 2010

Nano sized SiC particles (270 nm) are easily agglomerated in nickel sulfamate electrolytic bath during a composite electrodeposition process. The agglomeration of nano particles in composite coatings can significantly reduce the mechanical properties of the composite coatings. In this study, Ni-SiC nano composite coatings were fabricated using a conventional electrodeposition process with the aid of ultrasound. Nano particles were found to be distributed homogeneously with reduced agglomeration in the ultrasonicated samples. Substantial improvements in mechanical properties were observed in the composite coatings prepared in presence of ultrasound over those without ultrasound. Ni-SiC composite coatings were prepared with variable ultrasonic frequencies ranging from 24 kHz to 78 kHz and ultrasonic powers up to 300 watts. The ultrasonic frequency of 38 kHz with ultrasonic power of 200 watt was revealed to be the best ultrasonic conditions for homogeneous dispersion of nano SiC particles with improved mechanical properties in the composite coatings. The microstructures, phase compositions, and mechanical properties of the composite coatings were observed and evaluated using SEM, XRD, Vickers microhardness, and wear test. The Vickers microhardness of composite coatings under ultrasonic condition was significantly improved as compared to the coatings without ultrasound. The friction coefficient of the composite coating prepared with an ultrasonic condition was also smaller than the pure nickel coatings. A synergistic combination of superior wear resistance and improved microhardness was found in the Ni-SiC composite coatings prepared with ultrasonic conditions.