• Journal of the Korean Society of Safety
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• v.34 no.6
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• pp.7-12
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• 2019

Flux Cored Arc Welding (FCAW), which has been widely used in many industries, was developed in the 1950s to supplement shortcomings of the Shielded Metal Arc Welding (SMAW). FCAW has an advantage in that it can weld regardless of postures and give good quality results in the filed with many different working conditions. In this study, SM490A (rolled steel for welding structural purpose) with different thicknesses (L:25T+R:30T) were welded using FCAW. Then the mechanical properties (tension test, bending test, hardness test, impact test and macro test) were analyzed and the following conclusions were drawn. In the tensile test, it exceeds the KS standard tensile strength range (400~510) in all welding positions, which means there is a problem in the tensile force transmission performance. In the bending test, it was found that most of the specimens did not exhibit surface rupture or other defects during bending test and they exhibit sufficient toughness even after plastic deformation. In the hardness test, all the results were lower than the standard value of 350 Hv of KS B 0893, which means they have good hardness. In the impact test, all results were larger than the KS reference value of 27J. In the macro test, they showed uniform structure state by the shape of the weld, and there was risk of lamination because no internal defects, bubbles, or impurities were found on the surface of the weld.

• Restorative Dentistry and Endodontics
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• v.19 no.1
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• pp.159-168
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• 1994

The purpose of this study was to evaluate the shear bond strength of the porcelain laminate specimens according to the surface roughness of the cut enamel of human anterior teeth. Flat enamel surfaces were prepared in 30 extracted human anterior teeth with diamond disc which were divided into two groups. Group 1 Coarse enamel surface group prepared with LVS-3 bur. Group 2 Fine enamel surface group prepared with superfine diamond bur. 30 teeth specimens of two group were stored in normal saline during 24 hours. 30 disk - type porcelain laminate specimens with diameter 4mm and thickness 1mm were made and sand - blasted on internal surface which were to cemented on enamel surface. Porcelain laminate specimens were cemented on enamel surface with Choice Veneer System (Bisco Dental, U.S.A) according to manufacture's instructions. All teeth specimens of two groups were manipulated with same method and stored In normal saline before testing. An Universal Testing machine (Model No.UTM-4206,Instron, U.S.A) was used to apply shear loads in the vertical directed, and the force required for separation was recorded with a cross head speed of 3mm/min and 500kg in full scale. The results were as follow ; 1. The mean shear bond strength of coarse surface group was 36.30kg and that of fine surface group was 44.39 kg, but there was no significant difference in breaking strength of two groups(p>0.05).

• Journal of the Korea Institute of Building Construction
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• v.10 no.6
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• pp.67-75
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• 2010

In this paper, by using steel fiber, polypropylene fiber and these two hybrid fibers, the fire resistance performance and explosive properties of High Strength Concrete (HSC) with specified compressive strength of 40MPa are discussed. The paper also examines the bending resistance of the beam and the shearing resistance properties of non-reinforced HSC beam. This research helps to clarify the fire resistance of fiber HSC and its anti-explosion methods. The test results show that crack generation, explosion and carbonization can be effectively restrained when HSC is mixed with hybrid fibers under high temperature; furthermore, the maximum internal force and ductility are increased and the initial cracking can be restrained in the mechanical test.

• Archives of Craniofacial Surgery
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• v.12 no.1
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• pp.12-16
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• 2011

Purpose: This study examined the biomechanical stability of four different plating techniques in the experimental model of mandibular subcondyle fracture. Methods: Twenty standardized bovine tibia bone samples ($7{\times}1.5{\times}1.0cm$) were used for this study. Each of the four sets of tibia bone was cut to mimic a perpendicular subcondyle fracture in the center area. The osteotomized tibia bone was fixed using one of four different fixation groups (A,B,C,D). The fixation systems included single 2.0 mm 4 hole mini adaption plate (A), single 2.0 mm 4 hole dynamic compression miniplate (B), double fixation with 2.0 mm 4 hole mini adaption plate (C), double fixation with a 2.0 mm 4 hole mini adaption plate and 2.0 mm 4 hole dynamic compression miniplate (D). A bending force was applied to the experimental model using a pressure machine (858 table top system, $MTS^{(R)}$) until failure occurred. The load for permanent deformation, maximum load of failure were measured in the load displacement curve with the chart recorder. Results: Double fixation with a 2.0 mm 4 hole mini adaption plate and a 2.0 mm 4 hole dynamic compression miniplate (D) applied to the anterior and posterior regions of the subcondyle experimental model showed the highest load to failure. Conclusion: From this study, double fixation with an adaption plate and dynamic compression miniplate fixation technique produced the greatest biomechanical stability. This technique may be considered a useful means of fixation to reduce the postoperative internal maxillary fixation period and achieve early mobility of the jaw.

• Journal of the Korean Chemical Society
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• v.36 no.4
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• pp.523-535
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• 1992

The conformations of hexapeptides, their complexation with alkali cations and the inhibition of the cation transport by 5,5-diphenylhydantoin(DPH) were studied theoretically using ECEPP/2 and MM2 force field. Several low energy conformations of uncomplexed cyclic hexapepides are obtained, and they adopt compact conformations in which most amide hydrogens form intramolecular hydrogen bond to amide carbonyl oxygens. The complexation energy of the peptide with $Na^+$ ion and DPH is -60 kcaal/mol and -18 kcal/mol, respectively. However, no suitable cavity to bind metal cation exists for the local minima of the peptide, and the internal energy of the uncomplexed hexapeptide having cavity is higher than that of the uncomplexed global minimum of this work by 10 kcal/mol. Also, one of the most important amino acid residue to bind DPH is Glycine, and this can explain experimental observation that the replacement of Gly by Sarcosine (N-methyl Glycine) reduce the inhibition ability of the cation transport.

• Smart Structures and Systems
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• v.2 no.2
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• pp.115-126
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• 2006

The Terra-Scope system is an affordable 4-D down-hole seismic monitoring system based on independent, microprocessor-controlled sensor Pods. The Pods are nominally 50 mm in diameter, and about 120 mm long. They are expected to cost approximately $6000 each. An internal 16-bit, extremely low power MCU controls all aspects of instrumentation, eight programmable gain amplifiers, and local signal storage. Each Pod measures 3-D acceleration, tilt, azimuth, temperature, and other parametric variables such as pore water pressure and pH. Each Pod communicates over a standard digital bus (RS-485) through a completely web-based GUI interface, and has a power consumption of less than 400 mW. Three-dimensional acceleration is measured by pure digital force-balance MEMS-based accelerometers. These accelerometers have a dynamic range of more than 115 dB and a frequency response from DC to 1000 Hz with a noise floor of less than $30ng_{rms}/{\surd}Hz$. Accelerations above 0.2 g are measured by a second set of MEMS-based accelerometers, giving a full 160 dB dynamic range. This paper describes the system design and the cooperative shared-time scheduler implemented for this project. Restraints accounted for include multiple data streams, integration of multiple free agents, interaction with the asynchronous world, and hardened time stamping of accelerometer data. The prototype of the device is currently undergoing evaluation. The first array will be installed in the spring of 2006.

• Wind and Structures
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• v.16 no.6
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• pp.579-601
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• 2013

Interference effects are of considerable concern for group hyperboloidal cooling towers, but evaluation methods and results are different from each other because of the insufficient understanding on the structure behavior. Therefore, the mechanical performance of hyperboloidal cooling tower shell under wind loads was illustrated according to some basic properties drawn from horizontal rings and cantilever beams. The hyperboloidal cooling tower shell can be regarded as the coupling of horizontal rings and meridian cantilever beams, and this perception is beneficial for understanding the mechanical performance under wind loads. Afterwards, the mean external latitude wind pressure distribution, CP(${\theta}$), was artificially adjusted to pursue the relationship between different CP(${\theta}$) and wind-induced responses. It was found that the maximum responses in hyperboloidal cooling tower shell are primarily dominated by the non-uniformity of CP(${\theta}$) but not the local pressure amplitude CP or overall resistance/drag coefficient CD. In all the internal forces, the maximum amplitude of meridian axial tension shows remarkable sensitivity to the variation of CP(${\theta}$) and it's also the controlling force in structure design, so it was selected as an indicator to evaluate the influence of CP(${\theta}$) on responses. Based on its sensitivity to different adjustment parameters of CP(${\theta}$), an comprehensive response influence factor, RIF, was deduced to assess the meridian axial tension for arbitrary CP(${\theta}$).

• Journal of the Society of Naval Architects of Korea
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• v.58 no.1
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• pp.49-57
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• 2021

In the production power transmitting of a floating production system like a wind offshore floating, the power cable should be connected from the surface system into the subsea system. The connection between the surface and the subsea system will make the power cable get a dynamic load like current and wave forces. Based on this condition, a dynamic power cable is required to endure external physical force and vibration in the long-term condition. It needs more requirements than static power cable for mechanical fatigue properties to prevent failures during operations in marine environments where the external and internal loads work continuously. As a process to verify, the durability test of dynamic power cables under the marine operation environment condition was carried out by using domestic technology development.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.41-45
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• 2018

We have investigated the effect of $Y_2O_3$ nanoparticles on the pinning properties of $Y_2O_3$-doped $GdBa_2Cu_3O_{7-{\delta}}$ (GdBCO) films. Both undoped and $Y_2O_3$-doped GdBCO films were grown on $CeO_2$-buffered MgO (100) single crystal substrates by pulsed laser deposition (PLD) using KrF (${\lambda}=248nm$) laser. The $Y_2O_3$ doping contents were controlled up to ~ 2.5 area% by varying the internal angles of $Y_2O_3$ sectors put on the top surface of GdBCO target. Compared with the $Gd_2O_3$-doped GdBCO films previously reported by our group [1], the $Y_2O_3$-doped GdBCO films exhibited less severe critical temperature ($T_c$) drop and thus slightly enhanced critical current densities ($J_c$) and pinning force densities ($F_p$) at 65 K for the applied field parallel to the c-axis of the GdBCO matrix (B//c) with increasing the doping content. Below 40 K, the in-field $J_c$ and $F_p$ values of all $Y_2O_3$-doped GdBCO films exhibited higher than those of undoped GdBCO film, suggesting that $Y_2O_3$ inclusions might act as effective pinning centers.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.137-144
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• 2019

In coupon test of carbon fiber reinforced polymers (CFRP) as brittle materials, the converted strain derived from total deformation and effective length was introduced and its advantages were described. In general, measured value from strain gauge is used for determining the tensile properties of material, but it is not quite effective in CFRP because brittle material can not redistribute its stress and it only represents local behavior. For this reason, the converted strain response can be utilized effectively as a supplementary indicator, which evaluated the average value of tensile properties in brittle material and confirmed the strain measured by strain gauge. In addition, the converted strain clearly visualized 1) the effect of initial internal strain caused by fabrication errors and setup misalignment when applying gripping force and 2) post-response of partial rupture of CFRP caused by non-uniform strain distribution. non-uniform strain distribution.