• Korean Journal of Community Nutrition
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• v.25 no.1
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• pp.1-12
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• 2020

Objectives: This study investigates the current state of consuming breakfast among elementary school students residing in Malang, East Java, Indonesia, and to identify factors that influence breakfast behavior. Methods: The research model was set up as per the health belief model, and slightly modified by adding the subjective normative factors of the theory of planned behavior. The survey was conducted from July 17 to August 15, 2017 using a questionnaire, after receiving the permission PNU IRB (2017_60_HR). Results: The subjects were 77 boys (49.4%) and 79 girls (50.6%) suffering from malnutrition with anemia (21.2%) and stunting ratio of Height for Age Z Score (HAZ) (11.5%). Furthermore, moderate weakness (14.8%) and overweight and obesity (12.3%) by Body Mass Index for Age Z Score (BMIZ) were coexistent. According to the results obtained for breakfast, 21.8% did not eat breakfast before school, with 18.8% of the reasons for skipping breakfast being attributed to lack of food. Even for subjects partaking breakfast, only about 10% had a good balanced diet. The average score of behavioral intention on eating breakfast was 2.60 ± 0.58. The perceived sensitivity, perceived severity, perceived benefits, and self-efficacy of the health belief model correlated with breakfast behavior. Of these, self-efficacy (β=0.447, R²=0.200) and perceived sensitivity (β=0.373, R²=0.139) had the greatest effect on breakfast behavior. Mother was the largest impact person among children. Conclusions: In order to increase the level of breakfast behavior intention among children surveyed in Indonesia, we determined the effectiveness by focus on education which helps the children recognize to be more likely to get sick when they don't have breakfast, and increase their confidence in ability to have breakfast on their own. We believe there is a necessity to seek ways to provide indirect intervention through mothers, as well as impart direct nutrition education to children.

• Journal of Korean Society of Steel Construction
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• v.24 no.6
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• pp.693-700
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• 2012

In this study, the Charpy impact test along with metallurgical observation was conducted to evaluate low temperature impact toughness of structural steel welds with different welding processes to find out the optimal welding process to guarantee the required impact toughness at low temperatures. The welding processes employed are shield metal arc welding (SMAW) and flux cored arc welding(FCAW), which are commonly used welding methods in construction. The Charpy impact test is a commercial quality control test for steels and other alloys used in the construction of metallic structures. The test allows the material properties for service conditions to be determined experimentally in a simple manner with a very low cost. To investigate the impact toughness at low temperatures of the steel welds, specimens were extracted from the weld metal and the heat affected zone. Standard V-notch Charpy specimens were prepared and tested under dynamic loading condition. The low temperature impact performance was evaluated based on the correlation between the absorbed energy and the microstructure. Analysis of the results showed that the optimal welding process to ensure the higher low temperature impact toughness of the HAZ and the weld metal is SMAW process using the welding consumable for steels targeted to low temperature use.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.42-50
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• 2016

Overlay welding affects the chemical components and weld hardness by dilution of the lamination layer thickness, which determines the surface properties. This study experimentally investigates different numbers of layers for overlay welding monel materials, which are anti-corrosion materials. The Fe content, weldability of the base metal and monel materials, hardness, and surface flatness were examined. Each evaluation was carried out after overlay welding with three layers on the base material and pipe base material of the plate. The Fe content was evaluated by analyzing the constituents of each layer. The Fe content was satisfactory in the three layers. The weldability of the laminate specimens was evaluated by a bending test. The hardness and bead flatness of the laminate specimens were evaluated by micro Vickers and 3D measurements. The hardness was highest in the heat-affected zone with one layer, and it decreased with increasing lamination. In the case of bead flatness, there is a sharp difference in the deviation with increasing numbers of laminations, which should be considered carefully.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.122-128
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• 2005

A feasibility study on the application of self?shielded flux cored arc welding to the on-site SM520 steel bridge box fabrication for express trains and high way construction instead of gas-shield flux cored arc welding was conducted in terms of weld soundness, mechanical properties, toughness and microstructures. All welded specimens made with the self?shielded FCAW process were tested by magnetic particle and ultrasonic techniques and they were found to be sound. All multipass weld specimens made with both self-shielded and gas-shielded FCAW processes showed yield and tensile strengths of $462{\sim}549\;MPa$ and $548{\sim}640\;MPa$, respectively. The impact values of Charpy V-Notch weld specimens also met with the required value of 40J at $-20^{\circ}C$. The hardness values of the top area of weldments were higher than those of the bottom area because of higher residual stresses in the near surface. It was found that welding characteristics of SM520 steel by the on-site welding conditions with self-shielded FCAW showed almost equivalent to those by gas-shielded FCAW in terms of sound welds, mechanical properties and microstructure.

• Journal of Welding and Joining
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• v.34 no.2
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• pp.1-10
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• 2016

The use of materials for modern lightweight auto-bodies is becoming more complex than hitherto assemblies. The high strength materials nowadays frequently used for more specific fields such as the front and rear sub frames, seat belts and seats are mounted to the assembled body structure using bolt joints. It is desirable to use nuts attached to the assembled sheets by projection welding to decrease the number of loose parts which improves the quality. In this study, nut projection welding was carried out between a nut of both boron steel and carbon steel and ultra-high strength hot-stamped steel sheets. Then, the joints were characterized by optical and scanning electron microscope. The mechanical properties of the joints were evaluated by microhardness measurements and pullout tests. An indigenously designed sample fixture set-up was used for the pull-out tests to induce a tensile load in the weld. The fractography analysis revealed the dominant interfacial fracture between boron steel nut weld which is related to the shrinkage cavity and small size fusion zone. A non-interfacial fracture was observed in carbon steel nut weld, the lower hardness of HAZ caused the initiation of failure and allowed the pull-out failure which have higher in tensile strengths and superior weldability. Hence, the fracture load and failure mode characteristics can be considered as an indication of the weldability of materials in nut projection welding.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.768-773
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• 2016

Engine valve seat and face, which are the important factors affecting engine performance, are required to have wear, heat and corrosion resistance. In order to produce surface layer with these characteristics, PTA(plasma transferred arc) surfacing procedure is generally employed, but problems, such as large HAZ and high dilution etc., frequently occurr. Laser cladding, which overcomes the drawbacks of conventional technologies, can be employed to create a superior clad layer with low dilution, small heat affected zone, and minimal distortion. However, in case cladding is to be applied to a large area, it is necessary to overlap 1 pass clad layer because of limited clad layer width. Two criteria for the overlapping ratio-beam size and clad layer width-have been considered thus far. Upon inspection of multi pass clads, produced by different overlapping criteria, it was observed that the greater the increase in overlapping ratio, the greater was the decrease in clad layer width and increase in clad layer height regardless of the criterion used. However, a multi pass clad overlapped by the beam size criterion demonstrated a higher hardness value than a clad overlapped by the clad layer width owing to decreasing dilution of the substrate. In conclusion, the beam size was defined as the criterion for the overlapping, because the clad layer width increased or decreased depending upon process parameters.

• Journal of Welding and Joining
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• v.25 no.6
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• pp.53-58
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• 2007

The present study examined the mechanical properties of the friction welding of shaft made of SKH51 and SM45C, of which the diameter is 12mm. Friction welding was done at welding conditions of 2,000rpm, friction pressure of 104MPa, upset pressure of 134MPa, friction time of 0.5sec to 2.5sec by increasing 0.5sec, upset time of 2 seconds. Under these conditions, a tensile test, a bending test, a shear test, a hardness test and a microstructure of weld interface were studied. When the friction time was 1.0 second under the conditions, the maximum tensile strength of the friction weld observed to be 963MPa, which is 89% the tensile strength of SKH51 base metal and 101% of the tensile strength of SM45C base metal. When the friction time was 1.0 seconds under the conditions, the maximum bending strength of the friction weld happened to be 1,647MPa, which is 78% the bending strength of SKH51 base metal(2,113MPa) and 87% of the bending strength of SM45C base metal(1,889MPa). When the friction time was 1.0 seconds under conditions, the maximum shear strength of the friction weld was observed to be 755MPa, which is 92% the shear strength of SKH51 base metal and 122% of the shear strength of SM45C base metal. According to the hardness test, the hardness distribution of the weld interface varied from Hv282 to Hv327. HAZ was formed from the weld interface to 1.2mm of SKH51 and 1.6mm of SM45C. Upon examination it was found that the microstructure became finer along with increase of friction revolution radius.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.1
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• pp.49-59
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• 1984

Optimizing investigation of characteristics of underwater welding by a gravity type arc welding process was experimentally carried out by using six types of domestic coated welding electrodes for welding of domestic marine structural steel plates (KR Grade A-1, SWS41A, SWS41B,) in order to develop the underwater welding techniques in practical use. Main results obtained are summarized as follows: 1. The absorption speed of the coating of domestic coated lime titania type welding-electrode became constant at about 60 minutes in water and it was about 0.18%/min during initial 8 minutes of absorption time. 2. Thus, the immediate welding electrode could be used in underwater welding for such a short time in comparison with the joint strength of in-atmosphere-and on-water-welding by dry-, wet-or immediate-welding-electrode. 3. By bead appearance and X-ray inspection, ilmenite, limetitania and high titanium oxide types of electrodes were found better for underwater-welding of 10 mm KR Grade A-1 steel plates, while proper welding angle, current and electrode diameter were 6$0^{\circ}C$, above 160A and 4mm respectively under 28cm/min of welding speed. 4. The weld metal tensile strength or proof stress of underwater-welded-joints has a quadratic relationship with the heat input, and the optimal heat input zone is about 13 to 15KJ/cm for 10mm SWS41A steel plates, resulting from consideration upon both joint efficiency of above-100% and recovery of impact strength and strain. Meanwhile, the optimal heat input zone resulting from tension-tension fatigue limit above the base metal's of SWS41A plates is 16 to 19KJ/cm. Reliability of all the empirical equations reveals 95% confidence level. 6. The microstructure of the underwater welds of SES41A welded in such a zone has no weld defects such as hydrogen brittleness with supreme high hardness, since the HAZ-bond boundary area adjacent to both surface and base metal has only Hv400 max with the microstructure of fine martensite, bainite, pearlite and small amount of ferrite.