최근에는 다양한 중량의 구조물을 지진으로부터 보호하기 위해 지반으로부터 분리하는 면진장치로써 지반 격리용 받침이 활용된다. 지진의 피해를 저감시키는 설계방법 중에서 면진 설계는 구조물과 지반이 만나는 부분에 면진받침을 사용하는 방식으로 다른 내진/제진 설계 방법과 비교하면 가격대비 효율과 성능이 가장 우수하다. 본 연구에서는 지진 발생 이후 지속적으로 사용 가능한 새로운 개념의 자동복원 면진받침 시스템을 제안하고자 한다. 이러한 면진받침에 대한 성능을 검증하기 위하여 이론 적립 및 설계를 수행하고 실험체를 제작하여 실제 지진 데이터가 적용된 진동대 실험을 수행하였다. 기본특성실험, 면압의존성 실험, 속도의존성 실험, 변위의존성 실험에서 강도하중이 설계 목표치와 유사하였고, 거동 또한 설계값과 유사함을 확인하였고 이를 바탕으로 면진받침의 성능 검증을 분석하였다.

PURPOSES : The purpose of this study is to analyze not only the strength but also the durability and abrasion resistance of concrete pavements as increasing the cases of domestic concrete pavement damage which do not meet the service years. METHODS: The bottom layer of a two-lift concrete pavement was paved with original Portland cement (OPC) with 20~23 cm thickness. On the other hand, the top-layer, which is directly exposed to the environment and vehicles, was paved with high-performance concrete (HPC) with 7~10 cm thickness. For the optimal mixed design of the top-layer material of a two-lift concrete pavement, silica fume and polymer powder were mixed. Furthermore, it analyzes abrasion resistance of concrete as follow‘ ASTM C 779’which is dressing wheel abrasion test method. RESULTS : As a result, abrasion resistance is improved with increasing the silica fume ratio. When the polymer powder is mixed, abrasion resistance of concrete is much improved. However, the effect of mixing ratio is not significant. It is very effective that adding both silica fume and polymer powder occur 20~40% of abrasion comparing with OPC variables. CONCLUSIONS : The concrete strength and durability increased with silica fume and polymer powder. In particular, it is significant increasing strength of polymer powder under the flexural strength. In the abrasion resistance side, it is also significant when the silica fume and polymer powder used together.

Anion exchange membrane (AEM) with fixed charged cationic groups can selectively transport anionic molecules such as hydroxide anions. The AEM materials have been widely used in the wide range of applications such as polymer electrolyte fuel cells, water electrolysis, and reverse electrodialysis and electrodialysis. Commercially available AEM materials show high electrochemical resistance owing to their chemical architectural features leading to less separated hydrocarbon morphologies. Very low solubility to casting solvents and weak chemical durability to alkaline atmosphere of the AEM materials also makes it difficult to make thin and tough AEM membranes. In this study, AEM materials composed of perfluorinated architectures with improved chemical durability and intrinsically well separated morphologies were developed and evaluated.

Perfluorinated sulfonic acid (PFSA) ionomers have been commonly used as representative polymer electrolyte membrane (PEM) materials for fuel cell electric vehicles owing to their fast proton transport and excellent chemical resistance. However, PFSA materials still have weakness associated with chemical degradation occurring as a result from radical attacks, which induce membrane thickness reduction, leading to hydrogen crossover, and/or reduced electrochemical performances. In this study, cerium derivative radical scavengers were designed as functional additives to enhance the chemical durability of PFSA PEM. Their optimum content was suggested, comprehensively considering their radical resistance as well as other fundamental characteristics associated with long-term durability and electrochemical performance.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a food-borne bacterial pathogen that causes various diseases in both humans and animals such as hemorrhagic colitis and hemolytic uremic syndrome. Because cattle are the main reservoir of this microorganism, undercooked meat and meat byproducts contaminated with EHEC O157:H7 are most commonly associated with epidemic disease outbreaks. As an enteric pathogen, EHEC O157:H7 enters the body via a fecal-oral route and must survive passage through the gastric stomach at pH 1.5 to 3.5 to establish an infection within the gastrointestinal tracts. Therefore, the ability to resist such acidic environments is important to the pathogenesis of EHEC O157:H7 during a host infection. In this review, we will discuss on the acid resistance (AR) mechanisms induced by EHEC O157:H7 when E. coli encounters acidic environments.

Poultry play an important role in meeting the protein demand through the supply of chicken meat and eggs, and antimicrobial-resistant bacteria can be transmitted from poultry to humans through the food chain. In this study, 716 E. coli isolates were collected from poultry industry in Korea during the period from 2016-2018. Among the cephalosporin antimicrobial, the rate of resistance to first-cephalosporins (cefazolin and cephalexin) was more than 18.0% but secondcephalosporins (cefoxitin and cefuroxime) and four-cephalosporins (cefepime) was less than 10.0%, without any differences based on the poultry. In quinolone antimicrobial, the rate of resistance to nalidixic acid was more than 46.0% in all poultry but ciprofloxacin was more than 44.0% in broiler farm and chicken meat and less than 18.0% in layer farm and egg. In addition, the rate of resistance to ampicillin and tetracycline was more than 30.0% without any differences in poultry, but the rate of resistance to amoxicillin - clavulanate, trimethoprim - sulfamethoxazole, imipenem and gentamicin was higher in broiler farm and chicken meat than in layer farm and egg. MDR was detected in 120 (60.6%), 113 (79.6%), 80 (37.0%), and 75 (46.9%) isolates from broiler farm, chicken meat, layer farm, and egg, respectively, with an overall prevalence of 54.2% (388/716).