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Magnesium(Mg) alloys have been evaluated as replacements for steel or aluminum parts in the automobile industry because of the fuel economy they can provide through reducing weight. The application of Mg alloys has been limited due to its low formability at room temperature, which results from a small number of active slip systems. In the current study, an extruded TAZ711(Mg-7Sn-1Al-1Zn) alloy was warm forged into an automotive control arm to evaluate its formability at various forging temperature. Warm forging was conducted at temperatures of 200, 250, 350 and 450°C. Static strength evaluation was performed on the as-forged specimen at 250°C . The results showed good static strength. Key Words : TAZ711 As-extruded, Warm Forging, Control Arm, Formability Evaluation, Static Strength Evaluation 1. 서 론 최근 자동차 산업의 발달함에 따라 연비 개선 및 환경규제에 대응하기 위하여 경량 마그네슘 합금 적용에 관한 연구가 활발히 이루어지고 있다. 마그네슘 합금은 저밀도, 비강도와 비강성 등의 많은 장점이 있다. 현재 적용되고 있는 철계류 자동차 부품을 알루미늄과 마그네슘 합금으로 대체되는 적용하는 비율이 증대되고 있으며 소재 측면에서 고강도 가공재 개발연구가 이루어지고 있다[1~4]. 하지만 조밀육방구조(HCP)를 갖는 마그네슘 합금은 낮은 성형성과 강한 인장과 압축의 소성 비대칭으로 철계나 알루미늄을 대체 적용하기 어려움이 있다[5~7]. 이러한 마그네슘 합금의 비저면 슬립을 활성화 시키기 위하여 단조 성형 시 온간 및 열간단조로 성형하고 있으며 성형성 향상에 관한 연구가 확발히 이루어지고 있다. Yoon은 마그네슘 합금 AZ80압출재를 적용한 자동차의 조향장치 부품인 컨트롤암, 타이로드 및 변속기 부품인 차동기어 케이스를 성형온도 250~350°C에 대하여 온간단조(warm forging) 적용하여 기계적 특성 분석에 관한 연구가 이루어 졌다[1, 2]. Yoon과 Lee는 AZ80압출재를 적용하여 스크롤 압축기의 핵심 부품인 선회 스크롤을 배압장치를 이용하여 성형온도 350°C에서 온간단조에 관한 연구가 이루어졌다[3, 4]. 그 외 다양한 마그네슘 합금 압출재를 이용하여 성형온도 별 성형성 평가에 연구가 이루어 졌다[8]. Liu은 성형해석 결과를 바탕으로 마그네슘 합금을 적용한 슈퍼 베벨기어 성형에 관한 연구를 수행하였다[9]. Jiang는 오토바이용 실린더 바디를 마그

Our objective of this study was to explore the bacterial microbiome in fresh or fresh-frozen adult Amblyomma maculatum (Gulf Coast ticks) using extracts enriched for microbial DNA. We collected 100 questing adult A. maculatum, surface disinfected them, and extracted DNA from individual ticks collected the same day or after storage at −80 °C. Because only extracts with microbial DNA concentrations above 2 ng/μL were considered suitable for individual analysis, we expected fewer samples to meet these requirements. Of individual ticks extracted, 48 extracts met this minimum concentration. We pooled 20 additional extracts that had lower concentrations to obtain seven additional pools that met the minimum DNA concentration. Libraries created from these 55 samples were sequenced using an Illumina MiSeq platform, and data sets were analyzed using QIIME to identify relative abundance of microorganisms by phylum down to genus levels. Proteobacteria were in greatest abundance, followed by Actinobacteria, Firmicutes, and Bacteroidetes, at levels between 1.9% and 6.4% average relative abundance. Consistent with the Francisella-like endosymbiont known to be present in A. maculatum, the genus Francisella was detected at highest relative abundance (72.9%; SE 0.02%) for all samples. Among the top ten genera identified (relative abundance ≥ 0.5%) were potential extraction kit contaminants, Sphingomonas and Methylobacterium, the soil bacterium Actinomycetospora, and the known A. maculatum-associated genus, Rickettsia. Four samples had Rickettsia at greater than 1% relative abundance, while nine additional samples had Rickettsia at low (0.01–0.04%) relative abundance. In this study, we used the entire microbe-enriched DNA extract for whole ticks for microbiome analysis. A direct comparison of the microbiome in microbe-enriched DNA and total genomic DNA extracts from halves of the same tick would be useful to determine the utility of this extraction method in this system. We anticipate that future tick microbiome studies will be valuable to explore the influence of microbial diversity on pathogen maintenance and transmission, and to evaluate niche-specific microbiomes within individual tick tissues.

This study was conducted to determine the effects of dietary supplementation of Korean aged garlic extract (AGE) by Leukonostoc citreum SK2556 on growth performance, hematological status, meat quality, cecal microbiota and excreta gas emission in broilers. A total of 765-day old mixed sex ROSS 308 broiler chicks (body weight of 36.65 ± 0.10 g) were randomly allotted to five treatments with nine replications per treatment and 17 chicks per pen. The experiment lasted for 5 weeks and dietary treatments were as follows: (1) NC (negative control, basal diet without antibiotics); (2) PC (positive control, basal diet + 5 ppm enramycin); (3) AGE1 (basal diet + 0.5 g aged garlic extract/kg basal diet); (4) AGE2 (basal diet + 1 g aged garlic extract/kg basal diet); (5) AGE3 (basal diet + 2 g aged garlic extract/kg basal diet). Broilers fed with AGE2 treatment showed higher (linear, P=0.02) body weight gain (BWG) compared with NC treatment (910 vs. 842 g) from day 15 to day 28. During this time, feed conversion ratio (FCR) was higher (linear, P

Effects of rolling and cooling conditions on microstructures and mechanical properties of high-deform- able pipeline steels were investigated in this study. Six kinds of pipeline steels were fabricated by varying rolling and cooling conditions, and their microstructures were analyzed by scanning electron microscopy, electron back- scattered diffraction, and transmission electron microscopy. Tensile and Charpy impact tests were conducted on the steels in order to examine the mechanical properties. The steels rolled in the two-phase region showed bet- ter low-temperature toughness than those in the single-phase region due to the larger amount of ferrites having high-angle boundaries, although they have lower strength and absorbed energy. The steel rolled in single-phase and finish-cooled at higher temperature showed a good combination of high strength and good low-temperature toughness as well as excellent deformability of the lowest yield ratio and the highest uniform elongation because of the presence of fine ferrite and a mixture of various low-temperature transformation phases. (Received August 8, 2014; Revised August 21, 2014; Accepted August 28, 2014)

Half channel angular extrusion(HCAE) is the integration of equal channel angular extrusion(ECAE), which is a wellknown severe plastic deformation(SPD) method, with conventional forward extrusion in order to increase the strain per pass and effectiveness of the grain refinement. In the current study, the effects of processing routes during HCAE(Routes A, B, and C) on the strain distribution of the specimens have been investigated for an AZ61 Mg alloy by using three-dimensional finite element analysis. Comparisons with the results from a multi-pass of ECAE are made.

High-nitrogen Fe-18Mn-18Cr-N austenitic steels with higher yield strength have been recently devel-oped and used for generator retaining rings because they have non-magnetic, high strength, high ductility, andgood corrosion resistance. In the present study, a high-nitrogen Fe-18Mn-18Cr-0.61N austenitic steel was fabri-cated and then tensile and Charpy impact tests were conducted on them in order to investigate the effect of coldworking on the mechanical properties. Although the yield and tensile strengths usually increased with cold work-ing, the ductility and impact toughness significantly decreased after cold working. On the other hand, the high-nitrogen austenitic steel exhibited a ductile-brittle transition due to unusual brittle fracture at low temperaturesdespite having a face-centered cubic structure. The ductile-brittle transition temperature obtained from Charpyimpact tests could be remarkably increased by 60 o C after 20% cold working because of the enhanced cleavage-like brittle fracture. (Received February 27, 2014; Revised March 5, 2014; Accepted March 12, 2014)Keywords : Austenitic steel, High-nitrogen, Strength, Impact toughness, Cold working

The KSTAR (Korea Superconducting Tokamak Advanced Research) superconducting magnet system which consists of 16 TF coils and 14 PF coils adopts a superconducting CICC (Cable-In-Conduit Conductor) type conductor. The KSTAR magnet system uses two different types of CICCs-Nb/sub 3/Sn cable with Incoloy 908 conduit and NbTi cable with 316LN stainless-steel conduit. A continuous CICC jacketing system is developed for the KSTAR CICC fabrication and the jacketing system uses the tube-mill process. It consists of forming, welding, sizing and squaring procedures. The welding condition of CICCs and the fabrication process is described. The repair of the CICC is also discussed.

The induced voltage in the Samsung Superconducting Test Facility (SSTF) is analyzed according to the calculation of self-inductance and mutual inductance. The voltage induced by blip and compensating coils in the main coils is about 6.4 V. In order to charge the main coils, the power supply must provide the minimum voltage of 1.1 kV. The compensating coils have an influence on the field distribution. The compensating coils result in the decreasing center field about 2.67%. AC losses that include the coupling, hysteresis and eddy losses are calculated in the main, blip and compensating coils. It leads to the temperature rise of about 8 K in main coils.

In order to investigate whether the iron acquisition mechanisms of Staphylococcus aureus are induced by iron restriction in vitro, we examined S. aureus ATCC 6538 for production of siderophore and expression of transferrin-binding protein (SA-tbp) in normal or deferrated brain heart infusion broth (BHI). Siderophore production was earlier and greater in the deferrated BHI. The SA-tbp, detected by ligand blot assay, was expressed only in the deferrated BHI. When human transferrin was added to the deferrated BHI, siderophore production was later and lower than when transferrin was not present. In conclusion, both iron acquisition mechanisms of S. aureus were found to be iron-repressible and via both of them, human transferrin-bound iron was utilized for growth under iron-restricted condition.