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Herein, hydraulic model experiments and numerical simulations were performed to understand the self-burial mechanism of subsea pipelines with spoilers under steady flow conditions. First, scour characteristics and self-burial functions according to the spoiler length-to-pipe diameter ratio (S/D) were investigated through hydraulic experiments. Further, the Navier-Stokes solver was verified. The experimental values of the velocity at the bottom of the pipeline with a spoiler and the pressure on the sand foundation where the pipeline rested were represented with the degree of conformity. Scour characteristics of a sand foundation were investigated from the numerical analysis results of the velocity and vorticity surrounding the pipelines with spoilers. The compilation of results from the hydraulic experiment and numerical analysis showed that the projected area increased when a spoiler was attached to the subsea pipes. This consequently increased the velocity of fluid leaving the top and bottom of the pipe, and high vorticity was formed within and above the sand foundation. This aggravated scouring at the pipe base and increased the top and bottom asymmetry of the dynamic pressure field, which developed a downward force on the pipeline. These two primary effects acting simultaneously under steady flow conditions explained the self-burial of pipelines with a spoiler attachment.

Although several techniques have been proposed to remove fiber-reinforced composite (FRC) post, no safe and efficient technique has been established. Recently, a guided endodontics technique has been introduced in cases of pulp canal obliteration. This study describes 2 cases of FRC post removal from maxillary anterior teeth using this guided endodontics technique with a dental operating microscope. Optically scanned data set from plaster cast model was superimposed with the data set of cone-beam computed tomography. By implant planning software, the path of a guide drill was selected. Based on them, a customized stent was fabricated and utilized to remove the FRC post. Employing guided endodontics, the FRC post was removed quickly and safely with minimizing the loss of the remaining tooth structure. The guided endodontics was a useful option for FRC post removal.

The pollution of particulate matter (PM) is considered one of the hot socioenvironmental issues at present time. In this study, we investigated the distribution of fine particulate matter (PM 2.5 ) in Wangsimni commercial areas in Seoul, Korea to learn more about its environmental behavior in an urban area. Our analysis of PM 2.5 was made to distinguish the PM 2.5 pollution levels between three different types of site characteristics: (1) densely populated area, (2) thinly populated area, and (3) traffic roadside. Moreover, to assess the temporal trends in our study, the concentration levels of PM 2.5 were also compared between weekdays and weekends and between early in the afternoon and evening. The average concentration of PM 2.5 from densely and thinly populated areas were measured as 36.0±13.1 and 32.3±11.2 μg/m 3 , respectively. If the results are compared between different time bands, there were apparent differences between weekdays (29.6±10.8 μg/m 3 ) and weekends (36.9±12.1 μg/m 3 ). Such difference was also evident between noon (27.8±5.8 μg/m 3 ) and evening (38.3±13.7 μg/m 3 ). According to our research, concentration of PM 2.5 in the study area was affected more sensitively by time zone rather than the population density. The measurement data was also analyzed by drawing concentration map of PM 2.5 in the Wangsimni commercial areas based on data contouring method.