• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.773-782
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• 2002

In this study, a series of fatigue tests are performed in order to estimate quantitatively the characteristics of fatigue crack growth rate according to the base metal, heat affected zone(HAZ) and weld metal, and the welding method and grade of strength of object steels, and the influence on fatigue crack growth rate according to the direction of welded line for high strength steels of SM570, POSTEN60, and POSTEN80 steels. From the fatigue test results, the retardations of fatigue crack growth rate are remarkable in case that the direction of notch is parallel to welded line than in case that the direction of notch is perpendicular to welded line because of compresive residual stress in weld metal & HAZ. And the characteristics of fatigue crack growth rate according to welding method are that the dispersion of fatigue crack growth rate in case of FCAW method is smaller than that of SAW method. Also, it knows that the fatigue crack growth rate converges in high stress intensity factor range. Meanwhile, fatigue safety is guaranteed sufficiently in the object steels because the fatigue crack growth rate in the range of fatigue crack propagation has a similar tendency to the test results & existing results.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.2025-2036
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• 2000

A physicochemical process called ultra rapid coagulation(URC) was applied as a pilot scale to recover eutrophicated lake water at Inkyung Lake located on-campus in Inha university. The URC was uniquely designed to completely remove the presence of phosphorus up to 95%, which in turn leading to lessen the level of eutrophication of lake. For a pilot test of period, the lake was restored showing Carlson's Trophic State Index(TSI) of mesotrophic state which accounts for the reduction of total phosphorus and chlorophyll-a down to approximately 55 from 70 and 73, respectively. A residual presence of aluminum and additional coagulants in the effluent was tested for their potential effects on Photobacterium phosphoreum. The effect concentration ($EC_{50}$-15 min) observed in the effluent revealed that the bioactivity of Photobacterium phosphoreum was not influenced by the residual presence of coagulants. After the pilot test of period, the lake was consequently restored as a mesotrophic state in obtaining the second grade of lake water quality. The URC may be further applied for restoration of greater scale of lake in eutrophication.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.165-172
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• 2013

Power generating unit structures are designed and built to meet standard to secure its safety for expected life time. As the structures have been exposed to combined environment, degradation of structure material is accelerated and it can cause unexpected damage; evaluating precise mechanical properties of weak site like welded area is an essential research area as it is directly connected to safety issues. Existing measuring technique like tensile test requires specific size in testing specimen yet it is destructive method which is hard to apply on running structures. To overcome above mentioned limitation, IIT is getting limelight as it is non-destructive and simple method. In this study, latest technique is introduced to evaluate tensile property and residual stress by analyzing stress field occurs under the indenter while IIT is performed. Test on welded area, the weak site of nuclear structures have been practiced and confirmed that IIT can be usefully applied to evaluate integrity in industry.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.217-223
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• 2017

This research was planned to evaluate the structural performance of post tensioned(PT) concrete member subjected to fire. Prime objective was to suggest some techniques to evaluate the performance of post tensioned concrete beam and slab exposed to high temperature through experiment. To accomplish this objective, the following two scopes have been proceeded to verify the strength reducing ratio of strands and find out the difference of resisting force at the PT concrete members exposed to high temperature through the fire test. The properties of prestressing steel(tendon) in PT concrete beam and slab under variable temperatures were reviewed. The test of this study was shown that stress relaxation occurred at high temperature, and some restoration of tensional force appeared as it got cooling down. The residual tension of the post tensioned beams at 4 hours after reaching the target temperature were 70% at $400^{\circ}C$, 10% at $600^{\circ}C$ and 2% at $800^{\circ}C$. The post tensioned slabs were 94% at $400^{\circ}C$, 84.5% at $600^{\circ}C$ and 62% at $800^{\circ}C$. The reason why the residual tension loss of the post tensioned slab was relatively small was considered to be that the slab was exposed just one side to high temperature and the strength of the strand was restored larger than that of beam. Also, it was confirmed that the post tensioned member inevitably experienced the loss of strength by fire damage, and restoration design of the member should be required to compensate for the value as much as lost strength.

• The Korean Journal of Pesticide Science
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• v.16 no.2
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• pp.131-136
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• 2012

This study was carried out to elucidate residual characteristics of azoxystrobin and difenoconazole in fresh ginseng. Test pesticides were sprayed onto ginseng both in 2009 for 3-year-old ginseng and in 2010 for 4-year-old ginseng according to their pre-harvest intervals (PHIs). Limit of quantitation (LOQ) of both azoxystrobin and difenoconazole was 0.003 mg/kg. Analytical methods set up for the test pesticides were considered to be suitable for the analysis of their residues in fresh ginseng, considering that their recoveries ranged from 87.58 to 112.79%. Concentration of azoxystrobin in 3-year-old ginseng ranged from 0.004 to 0.011 mg/kg and that in 4-year-old ginseng ranged from 0.007 to 0.016 mg/kg. Amounts of difenoconazole in 3- and 4-year-old ginsengs were from 0.003 to 0.007 and from 0.007 to 0.01 mg/kg, respectively, representing no accumulation effect observed in residue amount between them.

• Korean Journal of Veterinary Service
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• v.24 no.1
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• pp.31-41
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• 2001

This study was carried out to identify causative agents from california mastitis test(CMT) positive mastitic milk, and to examine the antimicrobial susceptibility of 50 heads in Seongju and Chilgok area of Gyeongbuk province. Sulfadimethoxine sodium(SMS) was intramuscularly administered once to four mastitis Infected dairy cattle at the rate of 10mg/kg body weight. After injection of SMS, the depletion rate of serum and milk from the cattle were periodically measured for five days. The CMT positive number from 50 heads showed 46% and that of 200 quarters was 47(23.5%). From 39 quarters of 47 heads 39 different microorganisms were identified. These organisms were classified into 12 species : Staphylococcus aureus 8(20.5%), Sta hemolyticus 6(15.4%), Streptococcus bovis 4(10.3%), Sta hyicus 3(7.7%), Sta epidemidis. Sta xylosus, Sta sciuri 2(5.1%), Str agalactiae 2(5.1%), Escherichia coli(10.3%), three Enterobacter cloacae(7.7%), two Ent aerogenes(5.1%) and one Salmonella spp(2.6%). As the results of antibiotic susceptibility test, gentamicin(Gm, 11 species 27 strains, 69.5%), cephalotin(Cf, 9 species 24 strains, 61.5%), sulfamethoxazole(Stx, 8 species 14 strains, 43.6%), tetracycline(Tc, 8 species 14 strains, 35.9%), and streptomycin(Sm), lincomycin(Lm), cefoperazon(Cp) and penicillin(Pc) have a highly resistance(7.7% ～5.1%). However, carbenicillin (Cb), amikacin(Ah) have no susceptible for all drugs. The mean residual concentration of SMS in serum according to the time lapsed were showed 33.964 $\pm$ 4.435ppm at the 4 hours after intramuscularly injection(AII). It was significantly(p<.05) decreased to 6.596 $\pm$ 3.402, 0.217 $\pm$ 0.119 and 0.005 $\pm$ 0.004ppm at the 1st, 3rd and 5th day AII. The mean concentration of SMS in milk was significantly(p<.05) decreased from 0.920 $\pm$ 0.42ppm to 0.084 $\pm$ 0.016ppm between 8 hours and 1 day AII. As the results of this experiments, sulfadimethoxine was residued at the level of no less than 0.01ppm in milk on the 2nd day AII. Thus, this results would be able to be used the basic index for prevention of sulfonamides residue in milk after treatment of dairy mastitis.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.3
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• pp.45-54
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• 2000

The effect of electropolishing far stamped leadframe on the removal of the edge burr and residual stress relief was examined. The present study showed that the electropolishing could be used for enhanced surface quality of stamped leadframes. The electropolishing was performed at the condition of 60% phosphoric acid electrolyte, 5 ampere of current and 3 cm electrode gap at $70^{\circ}C$ for 2 minutes for Alloy42 type leadframe, and $50^{\circ}C$ for 1.5 minutes for C-194 type leadframe. The FWHM values from X-ray diffraction showed that residual stress of electropolished leadframe recovered to the level of as-received raw materials and surface roughness measured by using AFM tuned out to be improved by 0.079 $\mu\textrm{m}$ and 0.014 $\mu\textrm{m}$ ($R_{rms}$) far alloy 42 and C-194 type leadframes, respectively. The plated thickness using XRF showed the improved uniformity in thickness variation by 0.4~0.5 $\mu\textrm{m}$ and grain growth, which is favorable for interface adhesion, was also observed from the bake test samples. We could certify dimensional stability of leadframe with inspection by means of 3D-topography and hardness measurements.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.109-120
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• 2011

This paper presents an experimental study results on the crack control of flexure-dominant reinforced concrete beams repaired with strain-hardening cement composite (SHCC). Five RC beams were fabricated and tested until failure. One unrepaired RC beam was a control specimen (CBN) and remaining four speciemens were repaired with SHCC materials. The test parameters included two types of SHCC matrix ductility and two types of repair method (patching and layering). Test results demonstrated that RC beams repaired with SHCC showed no concrete crushing or spalling until final failure, but numerous hair cracks were observed. The control specimen CBN failed due to crushing. It is important to note that SHCC matrix can improve crack-damage mitigation and flexural behavior of RC beams such as flexural strength, post peak ductility, and energy dissipation capacity. In the perspective of crack width, crack widths in RC beams repaired with SHCC had far smaller crack width than the control specimen CBN under the same deflection. Especially, the specimens repaired with SHCC of PVA0.75%+PE0.75% showed a high durability and ductility. The crack width indicates the residual capacity of the beam since SHCC matrix can delay residual capacity degradation of the RC beams.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.325-332
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• 2020

In the safety diagnosis of fire-damaged concrete structures, it is difficult to evaluate the strength and changes in materials due to high temperatures with the existing durability analysis method. In particular, the compressive strength of specimen with different damage levels by thickness is used as a representative value for reducing the compressive strength of the structural member. In this study, a heating experiment was performed with only top face heating and fully heating conditions at 400℃ to 800℃. After heating, splitting tensile test and color analysis were performed to sliced specimens with a thickness of 20mm accompanied by the compressive test of a fully heated specimen. As a result of the experiment, the compressive strength reduction rate calculated from the splitting tensile strength of every sliced specimen appeared to be within 10% of the fully heated specimen on aver age, and the hue value analysis showed consistent color values were observed by red at 400℃-600℃ and gray at 700℃ or above. It follows that the techniques proposed in this study are reasonably assessable to estimate heated temperature and residual compressive strength and damage depth of concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.311-318
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• 2018

When reinforced concrete structures are exposed to fire, their mechanical properties such as compressive strength, elasticity coefficient and rebar yield strength, are degraded. Therefore, the structure's damage assessment is essential in determining whether to dismantle or augment the structure after a fire. In this study, the confinement effect of lateral reinforcement of RC column according to the numbers of fire exposure face and stirrup was verified by fire resistant test with the heating temperatures of $400^{\circ}C$, $600^{\circ}C$ and $800^{\circ}C$. The test results showed that the peak stress decreases and peak strain increases as the temperature is getting higher, also transverse ties are helpful in improving the compressive resistance of concrete subjected to high temperature. Based on the results of this study, the residual stress of confined concrete under thermal damage is higher at the condition of more lateral reinforcement ratio and less fire exposure faces. The decreasing ratio of elastic modulus of more confined and less exposure faces from the relationship of load and displacement was also smaller than that of opposite conditions.