• Korean Journal of Materials Research
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• v.23 no.1
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• pp.41-46
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• 2013

The microstructural evolution of AA1050/AA6061 complex aluminum alloy, which is fabricated using an accumulative roll-bonding (ARB) process, with the proceeding of ARB, was investigated by electron back scatter diffraction (EBSD) analysis. The specimen after one cycle exhibited a deformed structure in which the grains were elongated to the rolling direction for all regions in the thickness direction. With the proceeding of the ARB, the grain became finer; the average grain size of the as received material was $45{\mu}m$; however, it became $6.3{\mu}m$ after one cycle, $1.5{\mu}m$ after three cycles, and $0.95{\mu}m$ after five cycles. The deviation of the grain size distribution of the ARB processed specimens decreased with increasing number of ARB cycles. The volume fraction of the high angle grain boundary also increased with the number of ARB cycles; it was 43.7% after one cycle, 62.7% after three cycles, and 65.6% after five cycles. On the other hand, the texture development was different depending on the regions and the materials. A shear texture component {001}<110> mainly developed in the surface region, while the rolling texture components {011}<211> and {112}<111> developed in the other regions. The difference of the texture between AA1050 and AA6061 was most obvious in the surface region; {001}<110> component mainly developed in AA1050 and {111}<110> component in AA6061.

• Transactions of Materials Processing
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• v.14 no.1 s.73
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• pp.71-77
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• 2005

Thermal stability and dry sliding wear behavior of ultra-fine grained 6061 Al alloy fabricated by an accumulative roll-bonding (ARB) process have been investigated. After 4 ARB cycles, an ultra-fine grained microstructure of the 6061 Al alloy composed of grains with average size of 500nm, and separated mostly by high-angle boundaries was obtained. Though hardness and tensile strength of the ARB processed Al alloy increased with ARB cycles up to 4 cycles, the processed alloy exhibited decreased ductility and little strain hardening. Thermal stability of the ARB-processed microstructure was studied by annealing of the severely deformed alloy at $423K{\sim}573K$. The refined microstructure of the alloy remained stable up to 473K, and the peak aging treatment of the alloy at 450K for 8 hrs increased the thermal stability of the alloy. Sliding-wear rates of the alloy increased with the number of ARB cycles in spite of the increased hardness with the cycles. Wear mechanisms of the ultra-fine grained alloy were investigated by examining worn surfaces, wear debris, and cross-sections by a scanning electron microscopy (SEM).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1527-1528
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• 2011

• Journal of Microbiology and Biotechnology
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• v.33 no.3
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• pp.277-287
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• 2023

Since the first discovery of antibiotics, introduction of new antibiotics has been coupled with the occurrence of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Rapid dissemination of ARB and ARGs in the aquatic environments has become a global concern. ARB and ARGs have been already disseminated in the aquatic environments via various routes. Main hosts of most of ARGs were found to belong to Gammaproteobacteria class, including clinically important potential pathogens. Transmission of ARGs also occurs by horizontal gene transfer (HGT) mechanisms between bacterial strains in the aquatic environments, resulting in ubiquity of ARGs. Thus, a few of ARGs and MGEs (e.g., strA, sul1, int1) have been suggested as indicators for global comparability of contamination level in the aquatic environments. With ARB and ARGs contamination, the occurrence of critical pathogens has been globally issued due to their widespread in the aquatic environments. Thus, active surveillance systems have been launched worldwide. In this review, we described advancement of methodologies for ARGs detection, and occurrence of ARB and ARGs and their dissemination in the aquatic environments. Even though numerous studies have been conducted for ARB and ARGs, there is still no clear strategy to tackle antibiotic resistance (AR) in the aquatic environments. At least, for consistent surveillance, a strict framework should be established for further research in the aquatic environments.

• Advances in Computational Design
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• v.7 no.2
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• pp.129-137
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• 2022

Compo-casting method is one of the popular technique to produce metal based matrix composites. But, one of the main challenges in this process is un-uniform spreading of reinforced subdivisions (particles) inside the metallic matrix and the lack of desirable mechanical properties of the final produced composites due to the low bonding strength among the metal matrix and reinforcement particles. To remove these difficulties and to promote the mechanical properties of these kind of composites, the WARM ARB technique was utilized as supplementary technique to heighten the mechanical and microstructural evolution of the casted Al/Al₂O₃ composite strips. The microstructure evolution and mechanical properties of these composites have been considered versus different WARM ARB cycles by tensile test, average Vickers micro hardness test, wear test and scanning electron microscopy (SEM). The SEM results revealed that during the higher warm- ARB cycles, big alumina clusters are broken and make a uniform distribution of alumina particles. It was shown that cumulating the forming cycles improved the mechanical properties of composites. In general, combined compo-casting and ARB process would consent making Al/Al₂O₃ composites with high consistency, good microstructural and mechanical properties.

• Childhood Kidney Diseases
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• v.27 no.2
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• pp.121-126
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• 2023

The administration of angiotensin type 2 receptor blockers (ARBs) during pregnancy is known to cause ARB fetopathy, including renal insufficiency. We aimed to analyze the outcomes of two patients who survived ARB fetopathy and perform an accompanying literature review. Case 1 was exposed antenatally from a gestational age of 30 weeks to valsartan because of maternal pregnancy-induced hypertension. The patient presented with oliguria immediately after birth, and renal replacement therapy was administered for 24 days. Seven years after birth, renal function was indicative of stage 2 chronic kidney disease (CKD) with impaired urinary concentration. Case 2 had a maternal history of hypertension and transient ischemic attack and was treated with olmesartan until 30 weeks of pregnancy. Renal replacement therapy was performed for 4 days since birth. After 8 years, the patient is with CKD stage 2, with intact tubular function. Recent reports suggest that ARB fetopathy might manifest as renal tubular dysgenesis and nephrogenic diabetes insipidus, in contrast to mild alterations of glomerular filtration. Tubular dysfunction may induce CKD progression and growth retardation. Patients with ARB fetopathy should be monitored until adulthood. The ARB exposure period might be a critical factor in determining the severity and manifestations of fetopathy.

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.05a
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• pp.16-16
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• 2002

• YAKHAK HOEJI
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• v.58 no.2
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• pp.141-149
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• 2014

Background: Oriental lifestyle for treating diseases has been developed and well-accepted for a long time among Koreans. Sasang Constitution theory, originated from Korean traditional medicine, suggests that medication treatment should be differentiated by each patient's body classification (So-yang [SY], So-eum [SE], Tae-yang [TY], and Tae-eum [TE]), in contrary to western medicine's theory that medication should be applied equally by disease indication without such classification. However, the pharmacotherapeutic outcomes of these theories have not been compared to date. In this study, we aimed to compare the two theories by evaluating blood pressure (BP), which is lowered as a therapeutic outcome, among hypertensive patients taking angiotensin II receptor blockers (ARBs) or calcium channel blockers (CCBs), two most commonly used antihypertensive classes in Korea. Methods: From April 2006 to June 2012, we retrospectively collected data on hypertensive patients with Sasang Constitution classification at Kyunghee University Hospital at Gangdong, one of the East-West collaborative medical centers in Korea. We collected information on age, gender, underlying diseases, antihypertensive drugs (ARB, CCB, ARB+CCB), and BP by reviewing the electronic medical records. We excluded patients with missing blood pressure at baseline or follow-up, or those who had a change in their antihypertensive drug class during follow-up. Results: We selected a total of 573 patients (SY: 165, SE: 158, TY: 0, TE: 250). Baseline BPs were on average 139.0/82.0 mmHg for SY, 137.8/78.5 mmHg for SE, and 138.7/79.2 mmHg for TE. In all three groups, CCBs were the most prescribed, followed by combination therapy with ARB+CCB, then ARBs. BP reduction after 1 month of initial medication was significantly different among the drug classes, but not in Sasang constitutional classification (ARB [SY: -12.4/-4.7, SE: -12.3/-2.5, TE: -8.6/-1.8], CCB [SY: -12.3/-5.4, SE: -13.0/-2.3, TE: -10.8/-6.0], ARB+CCB [SY: -15.6/-6.7, SE: -18.4/-8.1, TE: -20.2/-6.7], drug [$P{\leq}0.05$/P>0.05], constitutional type [P>0.05/P>0.05]). Conclusion: We observed significant differences in reduction of blood pressure by classes of drugs (ARB+CCB>CCB>ARB) but not by Sasang constitutional classification. Therefore, current approach of antihypertensive pharmacotherapy assisted by Western medicine is appropriate for treatment of hypertension. However, further larger scale or prospective studies are required in order to confirm these results.

• Korean Journal of Materials Research
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• v.17 no.7
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• pp.361-365
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• 2007

A deoxidized low-phosphorous copper processed by eight cycles of accumulative roll-bonding (ARB) was annealed at various temperatures ranging from 100 to $400^{\circ}C$. The annealed copper was characterized by transmission electron microscopy (TEM) and tensile & hardness test. TEM observation revealed that the ultrafine grains developed by the ARB still remained up to $350^{\circ}C$, however above $400^{\circ}C$ they were replaced by equiaxed and coarse grains due to an occurrence of the static recrystallization. The hardness of the copper decreased slightly with the annealing temperature up to $350^{\circ}C$, however they dropped largely above $400^{\circ}C$. Annealing characteristics of the copper were compared with those of an oxygen free copper processed by ARB and subsequently annealed.

• Korean Journal of Materials Research
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• v.19 no.8
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• pp.432-436
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• 2009

A Cu-Fe-P copper alloy was processed by accumulative roll-bonding (ARB) for ultra grain refinement and high strengthening. Two 1mm thick copper sheets, 30 mm wide and 300 mm long, were first degreased and wire-brushed for sound bonding. The sheets were then stacked on top of each other and roll-bonded by about 50% reduction rolling without lubrication at ambient temperature. The bonded sheet was then cut into two pieces of the same dimensions and the same procedure was repeated for the sheets up to eight cycles. Microstructural evolution of the copper alloy with the number of the ARB cycles was investigated by optical microscopy (OM), transmission electron microscopy(TEM), and electron back scatter diffraction(EBSD). The grain size decreased gradually with the number of ARB cycles, and was reduced to 290 nm after eight cycles. The boundaries above 60% of ultrafine grains formed exhibited high angle boundaries above 15 degrees. In addition, the average misorientation angle of ultrafine grains was 30 degrees.