최근 선박용 연료유에 대한 황 함유량 규제를 준수하기 위해 저유황유의 수요가 증가하고 있다. 그러나 저유황유를 공급하는 시기, 지역, 회사 별로 그 품질이 상이함에 따라 선내 연료유 저장탱크에서는 과도한 슬러지가 발생하는 등 혼합 안정성에 대한 문제가 제기되고 있다. 따라서 본 연구는 초음파의 캐비테이션 현상을 이용하여 저유황유의 품질 향상을 하고자 하였다. 선내 저장 탱크에서 이종의 연료유가 혼합되는 상황을 모사하기 위해 두 가지 종류의 저유황유(황 함유량 0.5 % 이하 MGO, MDO)를 혼합하여 시료유로 사용하였다. 원료유와 50 wt.% 씩 혼합한 시료유를 120분 동안 초음파 처리하였으며, 40분 주기로 채취된 샘플은 GC/MS 분석을 수행하여 초음파 조사 시간에 따른 시료유의 조성 변화를 분석하였다. 연구결과, 초음파의 캐비테이션 효과로 인하여 화학결합이 깨지면서 MGO 내 존재하는 고분자량 화합물의 감소와 저분자량의 화합물 증가가 관찰되었다. MDO와 혼합유의 경우, 초음파 조사 후 저분자 화합물에 대한 상대 존재 비의 부분적 증가가 관찰되었지만 시간과 상대 존재비 사이의 상관관계는 관찰되지 않았다.

The 20-kHz ultrasonic irradiation was applied to investigate bacterial inactivation and antibiotic susceptibility changes over time. Applied intensities of ultrasound power were varied at 27.7 W and 39.1 W by changing the amplitude 20 to 40 to three bacteria species (Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus). By 15-min irradiation, E. coli, a gram-negative bacterium, showed 1.2- to 1.6-log removals, while the gram-positive bacteria, Enterococcus faecalis and Staphylococcus aureus, showed below 0.5-log removal efficiencies. Antibiotic susceptibility of penicillin-family showed a dramatic increase at E. coli, but for other antibiotic families showed no significant changes in susceptibility. Gram-positive bacteria showed no significant differences in their antibiotic susceptibilities after ultrasound irradiation. Bacterial re-survival and antibiotic susceptibility changes were measured by incubating the ultrasound-irradiated samples. After 24-hour incubation, it was found that all of three bacteria were repropagated to the 2- to 3-log greater than the initial points, and antibiotic inhibition zones were reduced compared to ones of the initial points, meaning that antibiotic resistances were also recovered. Pearson correlations between bacterial inactivation and antibiotic susceptibility showed negative relation for gram-negative bacteria, E. coli., and no significant relations between bacterial re-survival and its inhibition zone. As a preliminary study, further researches are necessary to find practical and effective conditions to achieve bacteria inactivation.

Membrane distillation (MD) is a novel separation process that have drawn attention as an affordable alternative to conventional desalination processes. However, membrane fouling and pore wetting are issues to be addressed prior to widespread application of MD. In this study, the influence of ultrasonic irradiation on fouling and wetting of MD membranes was investigated for better understanding of the MD process. Experiments were carried out using a direct contact membrane distillation apparatus Colloidal silica was used as a model foulants in a synthetic seawater (35,000 mg/L NaCl solution). A vibrator was directed attached to membrane module to generate ultrasonic waves from 25 kHz (the highest energy) to 75 kHz (the lowest energy). Flux and TDS for the distillate water were continuously monitored. Results suggested that ultrasonic irradiation is effective to retard flux decline due to fouling only in the early stage of the MD operation. Moreover, wetting occurred by a long-term application of ultrasonic rradiation at 75 kHz. These results suggest that the conditions for ultrasonic irradiation should be carefully optimized to maximize fouling control and minimize pore wetting.

폐식용유를 원료로 한 바이오 디젤의 제조 과정에 초음파 에너지를 조사하여 폐식용유의 전이에스테르 화반응 특성을 조사하였다. 초음파 조사는 두 가지 효과가 있는데 촉매의 대체역할과 공동현상이다. 실험의 매개 변수는 메탄올의 몰비, 반응온도, 촉매량이며 이를 변수로 최적공정조건을 구명한 결과 최적의 공정조건은 몰비가 1:7, 온도가 55 ℃, 촉매량은 1 wt％로 나타났다. 또한 초음파 에너지를 조사하는 실험의 매개변수는 초음파에너지 조사시간과 초음파에너지의 세기로서 이를 변수로 하여 초음파에너지조사가 바이오디젤 성능에 미치는 영향을 비교 하였다. 그 결과 최적의 초음파에너지 조사시간은 30분, 초음파에너지의 세기는 500 W로 나타났다. 또한 초음파에너지의 촉매 대체 가능성을 알아보기 위해 최적공정조건에서 촉매를 넣지 않고 초음파에너지를 30분간 조사하였을 때는 초음파에너지를 조사하지 않은 일반공정보다 바이오디젤의 성능은 BD(BioDiesel)수율이 2.4 %, FAME (Fatty Acid Methyl Ester)함량이 1.3 % 증가한 것으로 나타나, 초음파에너지가 촉매를 대체 할 수 있다는 것을 알 수 있었다.

In this study, ultrasonic detection device was applied to investigate connection part of concrete structure. Result of test, the internal void of connection part can be detected and it was possible to adopt the ultrasonic detection method to the maintenance of concrete structure.

Diethyl phthalate (DEP) is widely spread in the natural environment as an endocrine disruption chemicals (EDs). Therefore, in this study, ultrasound (US) and ultraviolet (UVC), including various applied power density (10-40 W/L), UV wavelengths (365 nm, 254 nm and 185 nm) and frequencies (283 kHz, 935 kHz) were applied to a DEP contaminated solution. The pseudo-first order degradation rate constants were in the order of 10-1 to 10-4 min-1 depending on the processes. Photolytic and sonophotolytic DEP degradation rate also were high at shortest UV wavelength (VUV) due to the higher energy of photons, higher molar absorption coefficient of DEP and increased hydroxyl radical generation from homolysis of water. Sonolytic DEP degradation rate increased with increase of applied input power and the dominant reaction mechanism of DEP in sonolysis was estimated as hydroxyl radical reaction by the addition of t-BuOH, which is a common hydroxyl radical scavenger. Moreover, synergistic effect of were also observed for sonophotolytic degradation with various UV irradiation.