• Journal of Welding and Joining
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• v.26 no.6
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• pp.4-7
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• 2008

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.8 no.2
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• pp.209-223
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• 1998

The aim of this study was to evaluate welders' exposure to hexavalent chromium (Cr(VI)) and nickel (Ni) during welding operations in a Korean shipyard. The airborne Cr(VI) and Ni concentrations were measured during metal inert gas (MIG) welding on mild and stainless steel, and manual metal arc (MMA) welding on mild steel. The geometric mean (GM) of Cr(VI) concentrations inside the welding helmet during MIG welding on mild steel were $0.0018mg/m^3$ inside a ship section, and $0.0015-0.0026mg/m^3$ at the welding shops. All of the personal breathing zone air samples were below the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value ($TLV^{(R)}$) of $0.01mg/m^3$. Conversely, eighty-eight percent(21 of 24) of the personal breathing zone air samples exceeded the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit of $0.001mg/m^3$. Ni was not detected on 20 of 23 air samples collected during MIG welding on mild steel. The three Ni samples above the limit of detection ranged from 0.015 to $0.044mg/m^3$. The GM of Cr(VI) concentrations during MMA welding on mild steel were $0.0013mg/m^3$, but Ni was not detected in the air samples during this operation. It is assumed that the airborne Cr(VI) and Ni during mild steel welding were derived from the base metals which contained about 0.03% Cr and 0.03% Ni. The GM of airborne total Cr, Cr(VI) and Ni concentrations during MIG welding on stainless steel were 4.02, 0.13 and $0.86mg/m^3$, respectively, and the levels of Cr(VI) and Ni were above the ACGIH-$TLV^{(R)}$. Cr(VI) comprised about 35.5% of the total chromium(Cr) from MIG welding on mild steel, and about 8.4% of total Cr from MIG welding on stainless steel. The ratios of Cr(VI) to total Cr were significantly different among welding shops. It was concluded that welders were exposed to high levels of Cr(VI) and Ni during welding on stainless steel, and were exposed to low levels of Cr(VI) even during welding on mild steel.

• Journal of Trauma and Injury
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• v.35 no.4
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• pp.248-254
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• 2022

Purpose: To analyze the data of trauma patients with undetected injuries at the time of initial resuscitation during the primary and secondary surveys. Methods: We retrospectively reviewed the medical records of 807 patients who were hospitalized at the National Trauma Center, Seoul, Korea from June 1, 2019 to June 30, 2021. Results: In trauma patients with an Injury Severity Score ≥16 accounted for 27.5% in the non-missed injury group (non-MIG), but this rate was considerably higher at 71.2% in MIG. The mean hospitalization longer in MIG (50.90±39.56) than in non-MIG (24.74±26.11). The proportion of patients with missed injuries detected through tertiary trauma survey (TTS) was 28 patients (23.5%) within 24 hours, 90 patients (75.6%) after 24 hours to before discharge. The majority of missed injuries were fractures (82.4%) and ligament tears (8.4%), which required consultation with the orthopedic department. The final diagnoses of missed injuries were confirmed by computed tomography (44.5%), magnetic resonance imaging (19.3%), X-ray (19.3%), bone scan (11.8%), and physical examination (5.0%). Conclusions: TTS is considered a useful process for detecting missed injuries that were not identified at the time of initial resuscitation in the primary and secondary surveys. In the future, to detect missed injuries quickly, it is necessary to develop a suitable TTS program for each trauma center. In addition, further research is needed to verify the effectiveness of the protocolized TTS and survey chart to improve the effectiveness of TTS.

• Metals and materials international
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• v.24 no.6
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• pp.1346-1358
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• 2018

A novel additive manufacturing method with TIG-MIG hybrid heat source was applied for fabricating 5356 aluminum alloy component. In this paper the microstructure evolution, mechanical properties and fracture morphologies of both as-deposited and heat-treated component were investigated, and how these were affected by different heat-treated temperature. The as-deposited microstructure showed dominant equiaxed grains with second phase, and the size of them is coarse in the bottom region, medium in the middle region and fine in the top region owing to different thermal cycling conditions. Compared with as-deposited microstructure, the size of grain becomes large and second phases gradually dissolve in the matrix as heat-treated temperature increase. Different microstructures determine the mechanical properties of component. Results show that average ultimate tensile strength enhances from 226 to 270 MPa and average microhardness increases from 64.2 to 75.3 HV0.1 but ductility decreases from 33 to 6.5% with heat-treated temperature increasing. For all components, the tensile properties are almost the same in the vertical direction (Z) and horizontal direction (Y) due to equiaxed grains, which exhibits isotropy, and the mechanisms of these are analyzed in detailed. In general, the results demonstrate that hybrid arc heat source has the potential to fabricate aluminum alloy component.

• Journal of Welding and Joining
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• v.15 no.1
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• pp.92-100
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• 1997

Weld repair of ASTM A-470 class 8 high pressure (HP) steam turbine rotor steel has been performed to extend the service life of older fossil units. Microhardness measurements were conducted across the weldment from unaffected base metal (BM) to weld metal (WM). The hardness of the BM was VHN 253, however it dropped up to VHN 227 at the heat affected zone (HAZ) close to unaffected BM for multipass SAW. This area of hardness drop is called "siftening zone" and has a width of 0.5-0.6mm. During creep rupture test, failure occurred around the softening zone and rupture time was 772.4hr at 19Ksi (132 Mpa) and 593.deg. C. Multipass MIG and TIG welding have been employed to reduce the softening zone width. The softening zone width for MIG was 0.3-0.4mm and for TIG was zero-0.4mm depending on heat inputs. However creep rupture time was decreased as softening zone width reduced. Creep rupture time also showed a close relationship with heat inputs in TIG process. The higher heat input, the longer rupture time. Most failure occurred at intercritical HAZ (ICHAZ), however rupture location was shifted to coarse grained HAZ (CGHAZ) as heat input decreased. The rupture surface showed tearing and dimple which indicated transgranular fracture. fracture.

• BMB Reports
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• v.53 no.3
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• pp.133-141
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• 2020

The epidermal growth factor receptor (EGFR), a member of the ErbB family (EGFR, ErbB2, ErbB3 and ErbB4), plays a crucial role in regulating various cellular responses such as proliferation, differentiation, and survival. As a result, aberrant activation of EGFR, mostly mediated through different classes of genomic alterations occurring within EGFR, is closely associated with the pathogenesis of numerous human cancers including lung adenocarcinoma, glioblastoma, and colorectal cancer. Thus, specific suppression of oncogenic activity of mutant EGFR with its targeted drugs has been routinely used in the clinic as a very effective anti-cancer strategy in treating a subset of tumors driven by such oncogenic EGFR mutants. However, the clinical efficacy of EGFR-targeted therapy does not last long due to several resistance mechanisms that emerge in the patients following the drug treatment. Thus, there is an urgent need for the development of novel therapeutic tactics specifically targeting mutant EGFR with the focus on the unique biological features of various mutant EGFR. Regarding this point, our review specifically emphasizes the recent findings about distinct requirements of receptor dimerization and autophosphorylation, which are critical steps for enzymatic activation of EGFR and signaling cascades, respectively, among wildtype and mutant EGFR and further discuss their clinical significance. In addition, the molecular mechanisms regulating EGFR dimerization and enzymatic activity by a key negative feedback inhibitor Mig6 as well as the clinical use for developing potential novel drugs targeting it are described in this review.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.94-100
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• 2002

During the last years, great progress has been made in the fields of welding power sources and filler materials for the MIG-welding of magnesium alloys. This advice resulted in a better welding process, md, therefore, in highly improved welding results. Furthermore the gap between short-circuiting- and spray-arc-trunsfer could be closed by the triggered short-circuiting- and the short-circuiting-arc with pulse overlay. A crucial contribution to the welding process is the energy input into the filler material. Many problems result from the physical properties of magnesium, for instance its narrow interval between melting point 600$^{\circ}C$ and vaporization point 1100$^{\circ}C$. The energy input into the filler material has to be regulated in such a way that the wire will melt but not vaporize. For th is reason, special characteristics of power sources hue been examined and optimized with the help of high-speed-photographs of the welding process with particular consideration of the drop detachment. An important improvement of the weld seam profile has been achieved by using filler material of only 1.2 mm in diameter. The experiments hue been made with 2.5 mm thick extruded profiles of AZ31 and AZ6l. The results of tensile testing showed strength values of 80 to 100% of the base metal. B ending angles up to 60$^{\circ}$ have been reached. The fatigue strength under reversed bending of the examined magnesium alloys after welding reaches 50% of the strength of the base metal. When the seam reinforcement is ground of the fatigue strength can be raised up to 75% of the base metal.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.28-33
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• 2014

In this paper, I-butt welding with 6mm thickness using Plasma-GMA welding was carried out. And weld characteristics of the Al-5083 aluminium alloy for Plasma-GMA hybrid welding was evaluated. The orthogonal experimental design was used to investigate the influence of plasma-MIG welding parameters such as plasma current, wire feeding rate, MIG-welding voltage and welding speed on the weld bead geometry and tensile strength using the ANOVA(Analysis of Variation). Then we conducted evaluation of contribution for process parameters. ANOVA results show that bead dimensions are affected by wire feeding speed, welding voltage and welding speed and tensile strength is mainly affected by welding speed and plasma arc current. Tensile strength was decreased by rise in plasma welding current because GMA welding current was decreased by plasma arc.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.6
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• pp.548-555
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• 2014

As a considerable, experimental approach, an Auto-carriage type of $CO_2$ welding machine and a MIG(Metal Inert Gas) welding robot under inert gas atmosphere were utilized in order to realize Al 5083 welding applied to hull and relevant components of green Al leisure ships. This study aims at investigating the effect of welding conditions(current, voltage, welding speed, etc) on thermal deformation that occurs as welding operation and tensile characteristics after welding, by using Al 5083, non-ferrous material, applied to manufacturing of co-environmental Al leisure ships. With respect to welding condition to minimize the thermal deformation, 150A and 16V at the wire-feed rate of 6mm/sec were acquired in the process of welding Al 5083 through an auto carriage type of $CO_2$ welding feeder. As to tensile characteristics of Al 5083 welding through a MIG welding robot, most of tensile specimens showed the fracture behavior on HAZ(Heat Affected Zone) located at the area joined with weld metal, except for some cases. Especially, for the case of the Al specimen with 5mm thickness, 284.62MPa of tensile strength and 11.41% of elongation were obtained as an actual allowable tensile stress-strain value. Mostly, after acquiring the optimum welding condition, the relevant welding data and technical requirements might be provided for actual welding operation site and welding procedure specification(WPS).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.26-33
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• 2008

This paper presents a new full-bridge soft switching PWM DC-DC converter circuit topology that adding one switcher, one lossless snubber quasi-resonance capacity to power source for general welding machine This full-bridge soft switching DC-DC convoter· topology can applicable 600[V] switching device (IGBT)incase of AC 400[V] common power source because the voltage of active switcher is 1/2 of DC bus line voltage. And low voltage hight current out)ut that first coil current is smaller than second coil current in high frequency transformer can be obtained with decreasing path loss in conventional DC bus line switcher. As it operate ZCS/ZVS in full range, high frequency, high efficiency and high output are implemented at low voltage and high DC current switching power supplies. All of this items are got from simulation and the result of experiment. If make up for the weak points of this proposed circuit, it will be used more easily for next generation TIG, MIG and MAG type of arc-welding machine.