• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.549-558
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• 2012

A topology optimization method for phononic crystals is developed for the design of sound barriers, using the level set approach. Given a frequency and an incident wave to the phononic crystals, an optimal shape of periodic inclusions is found by minimizing the norm of transmittance. In a sound field including scattering bodies, an acoustic wave can be refracted on the obstacle boundaries, which enables to control acoustic performance by taking the shape of inclusions as the design variables. In this research, we consider a layered structure which is composed of inclusions arranged periodically in horizontal direction while finite inclusions are distributed in vertical direction. Due to the periodicity of inclusions, a unit cell can be considered to analyze the wave propagation together with proper boundary conditions which are imposed on the left and right edges of the unit cell using the Bloch theorem. The boundary conditions for the lower and the upper boundaries of unit cell are described by impedance matrices, which represent the transmission of waves between the layered structure and the semi-infinite external media. A level set method is employed to describe the topology and the shape of inclusions. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in the level set function, which facilitates to handle complicated topological shape changes. Through several numerical examples, the applicability of the proposed method is demonstrated.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.396-403
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• 2018

In this paper, a high-performance and low-noise centrifugal fan is developed for cooling automotive seats which provide a driver with pleasant driving environment. First, the flow characteristics of the existing fan unit was analyzed using a fan performance tester and CFD (Computational Fluid Dynamics) simulations. The analysis of the predicted flow field indicated vortex flow near the tip of fan hub and stagnation flow on the top of fan hub. Two design points are devised to reduce the vortex flow and the stagnation flow observed in the existing fan unit. First, the cut-off clearance which is the minimum distance between the fan blade and the fan housing is increased to reduce the vortex strength and, as a result, to reduce the overall sound pressure level. Second, the hub shape is more modified to eliminate the stagnation flow. The validity of proposed design is confirmed through the numerical analysis. Finally, a prototype is manufactured with a basis on the numerical analysis result and its improved flow and noise performances are confirmed through the P-Q curves measured by using the Fan Tester and the SPL (Sound Pressure Level) levels measured in the anechoic chamber.

• Journal of Korea Water Resources Association
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• v.37 no.3
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• pp.249-255
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• 2004

To investigate the return flow ratio of irrigation water, lots of observations were made during the irrigation periods in 2003 crop year. This Area is a portion of Dae-Am pumping station basin which is located in Changryung-gun, Gyeongnam province. A water balance analysis was performed for a paddy field in Dae-Am pumping station in the Nakdong river basin, which is constructed for irrigation water supply. Daily rainfall data in the this area were collected and irrigation water flow rate, drainage water flow rate, infiltration and evaportranspiration were measured in field area. Irrigation water flow rate and drainage water flow rate were continuously observed by water level logger(GTDL-L10) during the growing season. The infiltration and evaportranspiration were measured by cylindrical 300mm depletion meter and cylindrical 200mm infiltrometer, respectively. Total irrigation and drainage flows were 654.7mm and 281.2mm in 2003. Total infiltration and evaportranspiration were 36.0mm and 160.0mm respectively. The mean of the daily evaportranspiration rate was 4.3mmm/d. The prompt return flow and retard return flow ratio were 43.0％ and 5.5％, respectively. Total return flow ratio was 48.5％. Therefore, it can be concluded that the amount of irrigation water was much higher than design standard or reference in this study. It means that this was caused by the inadequate water management practice in the area where water was oversupplied on farmers' request rather than following sound water management principles, and design standard should be changed in the future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.382-390
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• 2013

The efforts for improving 'Maritime Traffic Safety Assessment Scheme(MTSA scheme)' have continued to the present. At this point, it needs to establish sound MTSA scheme to proceed acceleration step through the comprehensive review and systematic approach. In this study, it aimed to design of Metaevaluation Model for the comprehensive analysis of MTSA scheme with applying theory of the Metaevaluation, that is the evaluation of evaluation. To put it concretely, This research draw a basic model by using Metaevaluation methods like as literature studies, expert reviews, surveys and etc. and proposed a available 'PIP'OU' Metaevaluation Model through verified validity and reliability. This PIP'OU Model is the first proposed Metaevaluation Model in maritime field and it is expected to be used as framework to draw up improvement measure with deriving problem for the MTSA scheme.

• Tunnel and Underground Space
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• v.25 no.3
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• pp.255-263
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• 2015

Explosive blasting is a very useful tool for mining and civil engineering applications. It, however, may cause severe environmental hazards on adjacent structures due to blasting impact. Blast engineers try to make optimum blast design to provide efficient performance and to minimize the environmental impact as well. It requires a pre-assessment of the impacts resulting from the blasting operation in design stage. One of the common procedures is to evaluate the proposed blast pattern through a series of test blasting in the field. Another approach is to evaluate the possible environmental effects using the numerical methods. There are a number of input parameters to be prepared for the numerical analysis. Some of them are well understood, while some are not. This paper presents some results of sensitivity analysis of the basic input parameters in numerical modelling of blasting problems so as to provide sound understanding of the parameters and some guidelines for input preparation.

• Journal of Sensor Science and Technology
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• v.11 no.3
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• pp.171-182
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• 2002

The differential electromagnetic transducer for IME(implantable middle ear) system, which have two small permanent magnets glued with the same pole facing each other in the coil, has high vibration efficiency and does not influenced by external magnetic field. In this paper, using finite element method, highly efficient structure of the transducer was proposed and vibration force of the transducer was calculated by electromagnetic theory. And the necessary vibration force of transducer to transmit the sound signal to inner ear when the transducer is attached at stapes was calculated and the design parameters of the transducer were investigated. Using the parameters, the differential electromagnetic transducer was manufactured in small size to implant in confined human middle ear. And it was examined by unloaded and loaded vibration experiment using temporal bone sampled from cadaver.

• International Journal of Computer Science & Network Security
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• v.21 no.12
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• pp.269-279
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• 2021

In the current conditions of world socio-economic development, the strategic support of the process of managing the development of universities has become a particularly important area. Strategic management requires reliable information and analytical support in the form of sound descriptions of strategic directions of development, assumptions, and forecasts. The purpose of the study is to substantiate and elaborate the crucial causes in the strategic management of university's development and to suggest the coherent prospects for advancements. The data analysis was performed using descriptive methods to identify the most significant causes that affect the university's strategic development; the expert assessment was used to rank the factors, ultimately to assess each factor that affects to some extent the university's strategic development; the abstract-logical method was used to ground the positive impact of computer technologies and e-learning on the strategic development of a university and to formulate proposals for its further progress. The main results provided in the given paper showed that significant and most important strategic cause of university's development lies in the field of improving the quality of education, expanding access to educational services based on computer technology and its functionality. In turn, its widespread use at all stages of the educational process allows providing a number of advancements for universities in strategic prospects.

• Fashion & Textile Research Journal
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• v.25 no.3
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• pp.366-378
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• 2023

Recently, the use of one-person broadcast content for special makeup videos has gained momentum. This study aims to analyze the factors preferred by various age groups as the total number of clicks increase on special makeup videos. It also aims to provide beauty creators with useful data to help them create videos that generate more clicks based on the derived elements. We analyzed previous studies and divided the subjective indicators into place & accessories, editing, model (Y/N), contents and field, and characteristics of the creators. We analyzed top 5 videos from among 257 videos uploaded before July 1, 2020. The subjective indicators were analyzed through a questionnaire survey attempted by 60 respondents in their 10-30s from Jeollanam-do and Gwangju between July 20 to August 31, 2020. The questions majorly focused on intimacy, attractiveness, professionalism, informativity, and playfulness. We analyzed the collected data using SPSS 21.0, and obtained the following results: Informativity, professionalism, attractiveness, and playfulness were considered to be more influential by those aged 10 to 30 years. In particular, factors like visual elements, linguistic characteristics, experts, background music and sound effects, celebrities, product information, and knowhow were most preferred. In fact, it was easy to make videos using these elements. The above results confirmed the utility of such data for beauty-creators-to-be in creating videos that generate more clicks.

• Fashion & Textile Research Journal
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• v.26 no.3
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• pp.279-288
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• 2024

Fingernail-related content on YouTube is gaining popularity. This study aimed to present a new direction for nail content marketing and video production by identifying the current status of nail-related content on YouTube and factors affecting views. As for the research method, the study used the YouTube website, and the elements under analysis were classified into YouTuber characteristics (verbal characteristics, age group, gender, professional status, and celebrity status) and content characteristics (nail field, editing elements, and content). The results showed that standard language and terminology were generally used, and the proportion of YouTubers in their 30s was high. All nail-related content creators on YouTube were women, and they were found to be experts who worked as nail artists and nail content creators. As for the content characteristics, the proportion of art videos was high, and the video length was found mostly to be between 10 and 20 minutes. The editing elements included images, videos, and subtitles, and sound effects and background music were used frequently. Finally, it was found that the proportion of videos providing nail tips and know-how, product information, and procedures was high. This study identified factors that influence the number of views for nail videos. As a result, the study was able to present video production ideas for newcomers starting a nail-content YouTube channel, and this will be helpful in the development of nail content.

• Journal of the Korean Institute of Landscape Architecture
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• v.50 no.2
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• pp.64-75
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• 2022

The purpose of this study is to illuminate the meaning of the soundscapes of two bells, Daeheung-dong Cathedral and Sungsimdang in Eunghang-dong, which are landmarks and attractions in the historic downtown of Daejeon. The study was conducted through field research and recordings, as well as literature studies of related documents and soundscape theory. Daejeon city was developed along with Daejeon Railway Station during the Japanese colonial period in the early 20th century. As the Chungnam Provincial Office moved to Daejeon, Daeheung-dong and Eunhang-dong in Jung-gu, located near Daejeon Station, developed significantly and formed the city centre. As major administrative agencies moved to Seo-gu in the 1990s, the downtown area of Daejeon was on a path of decline, and the decline accelerated with the development of Sejong city. Meanwhile, Daeheung-dong Cathedral and Sungsimdang, founded by refugees during the Korean War, firmly protected the historic downtown area of Daejeon, where the natives left. Daeheung-dong Cathedral, established during the Japanese colonial period, is a local landmark with a history of 100 years in 2019. Sungsimdang, which was created with the backdrop of the Korean War, is also a historical and cultural asset with a history of 60 years and a local landmark selected as the No. 1 tourist attraction in Daejeon. This research, which started from the sound of the bells of Daeheung-dong Cathedral, heard even in the neighboring residential areas, led to the discovery of the bells of Sungsimdang in Eunhang-dong, located across the street. In this paper, the bells of Daeheung-dong Cathedral and Eunhang-dong Sungsimdang have characteristics of soundmarks according to R. Murray Schafer's soundscape sound category. Furthermore, this paper attempted to analyze the meaning of the two bells according to the relatively recent EU soundscape definition. These two bells are signal sounds at the surface level, but are the sound marks of the historic downtown area of Daejeon at the deep level. Although there are outward differences in size, scale, frequency, and famousness, these two bells share a meaning in terms of locality and good influence with the historicity and spatiality of a special relationship. The implication of this study is that the two places should be preserved as local historical and cultural assets not only as visual landmarks but also as sound marks in the urban regeneration or urban development of Jung-gu, Daejeon.