• Advances in aircraft and spacecraft science
• /
• 제6권6호
• /
• pp.479-495
• /
• 2019

Periodic cellular core structures included in sandwich panels possess good stiffness while saving weight and only lately their potential to act as passive vibration filters is increasingly being studied. Classical homogeneous honeycombs show poor vibracoustic performance and only by varying certain geometrical features, a shift and/or variation in bandgap frequency range occurs. This work aims to investigate the vibration filtering properties of the AUXHEX "hybrid" core, which is a cellular structure containing cells of different shapes. Numerical simulations are carried out using two different approaches. The first technique used is the harmonic analysis with commercially available software, and the second one, which has been proved to be computationally more efficient, consists in the Wave Finite Element Method (WFEM), which still makes use of finite elements (FEM) packages, but instead of working with large models, it exploits the periodicity of the structure by analysing only the unit cell, thanks to the Floquet-Bloch theorem. Both techniques allow to produce graphs such as frequency response plots (FRF's) and dispersion curves, which are powerful tools used to identify the spectral bandgap signature of the considered structure. The hybrid cellular core pattern AUXHEX is analysed and results are discussed, focusing the investigation on the possible spectral bandgap signature heritage that a hybrid core experiences from their "parents" homogeneous cell cores.

• 한국멀티미디어학회논문지
• /
• 제23권4호
• /
• pp.588-594
• /
• 2020

This study analyzes the current status of drone journalism in Korean broadcasting industry, with a case study of TV Chosun Company's drone use for news gathering. It analyzes TV Chosun's record of drone logs between 2014 and 2018. The log consists of date, time, news content, users, machine and on-air date. In 2014, the total of 31 cases of using drones for news gathering is identified, while in 2018, the frequency increases to 60, with a gradual, annual increase, making the total frequency of 160, during the period between 2014 and 2018. This means that the broadcasting company used the drone news gathering system every week. The analysis also reveals that the company used this drone news gathering system mostly in the metropolitan area in Korea, amounting to more than 76 per cent of its total use: 31.3 per cent in Seoul, 36.9 per cent in Kyunggi, and 8.1 percent in Incheon. The system was more frequently used in the summer and autumn than the winter and spring. Interestingly, it was first popularly used for disaster related news, but the use of drone for social and other issues is increasing every year, which may imply its diverse use in the future.

• 복식
• /
• 제57권6호
• /
• pp.46-61
• /
• 2007

The analysis of exotic style in domestic fashion brand items aims to offer the ideas necessary for the style and item developments and to analyze exotic images and styles accepted in domestic fashion market. Therefore this study analyzed the domestic fashion brand items and categorized the main exotic factors and styles so that would catch on to its characters and appearance frequency. As for the research method of this study, the frequency and content multi-dimensional analysis were used in the investigation of the exotic images appearing in the domestic fashion brands. The styles of exotic image in domestic fashion brand items are 'natural' style, 'primitive' style, 'ethnic' style, and 'maximalism' style. Also, the main exotic factors in each exotic style were composed of a few exotic images such as 'natural', 'primitive', 'ethnic', 'romantic', 'elegance', 'splendid', 'seductive', 'retro', 'traditional', 'classical', 'bohemian', 'vintage', 'kidult', 'artistic', 'extreme compromise', and 'modern'.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
• /
• pp.232-233
• /
• 2005

In this paper, disk-type ultrasonic motor using a combination of radial and bending vibration modes is newly designed and fabricated. The characteristics of the test motor are also measured. By means of travelingelastic wave induced at the surface of circumference of the elastic disk, a steel bar in contact with the surface of circumference of elastic disk bonded onto the piezoelectric ceramic disks is driven inboth directions by changing the sine and cosine voltage inputs. The stator of the motor is composed of two sheets of piezoelectric ceramic disk to bond onto both surfaces of a elastic disk, respectively. As the results, the diameter of elastic body is increased, the resonant frequency is decreased. The resonant frequency of the stator is about 92 kHz, which is composed with piezoelectric ceramic disks of 28 mm in diameter and 2 mm in thickness, and an elastic body of 32 mm in diameter and 2 mm in thickness. A driving voltage of 20 Vpp produces 200 rpm with a torque of 1Nm and an efficiency of about 10 %.

• 센서학회지
• /
• 제23권3호
• /
• pp.165-169
• /
• 2014

An existing infrared (IR) analysis system is generally composed of infrared source, IR focusing lenses, IR detector, and optical chopper. An optical chopper is widely used in combination with lock-in amplifier to improve the signal-to-noise ratio by periodically interrupting incident light beam. During recent years, a few researches on miniaturized optical chopper have been reported to apply to micro-scaled optical systems. In this paper, a micro optical chopper operated by electromagnetic actuation is proposed and applied to a miniaturized micro-scaled optical system operating in IR spectral range. Additionally, the fabrication method of the proposed micro chopper is demonstrated. The proposed micro optical chopper is composed of the polydimethylsiloxane (PDMS) membrane, solenoid, and permanent magnet. The permanent magnet is bonded on the PDMS membrane using an ultraviolet-activated adhesive. The operation of the chopper is based on the attractive and repulsive forces between permanent magnet and solenoid induced by an electrical current flowing through the solenoid. The fabricated micro optical chopper could operate up to 200 Hz of frequency. The maximum operating distance of the chopper with 7mm diameter membrane was $750{\mu}m$ at 100 Hz of frequency.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 춘계학술대회 논문집
• /
• pp.535-544
• /
• 2008

Unlike MS(Magnetic Stripe), SMART CARD is equipped with COS(Chip Operating System) consisting of the Microprocessor and Memory where information can be stored and processed, and there are two types of cards according to the contact mode; the contact type that passes through a gold plated area and the contactless one that goes through the radio-frequency using an antenna embedded in the plastic card. the contactless IC card used for the transportation card was first introduced into local area buses in Seoul, and expanded throughout the country so that it has removed the inconvenience such as possession of cash, fare payment and collection. Focusing on the Seoul metropolitan area in 2004, prepaid and pay later cards were adopted and have been used interchangeably between a bus and subway. The card terminal compatible between a bus and subway is Proximity Integrated Circuit Card(PICC) as international standards(1443 Type A,B), communicates in the 13.56MHz dynamic frequency modulation-demodulation system, and adopts the Multi Secure Application Module(SAM). In the second half of 2009, the system avaliable nationwide will be built when the payment SAM standard is implemented.

• Journal of Korean Biological Nursing Science
• /
• 제17권2호
• /
• pp.211-217
• /
• 2015

Purpose: The purpose of this study is to identify factors influencing the pregnancy rate among unexplained infertile couples who received treatments of assisted reproductive technology (ART) and intra-uterine inseminations (IUI). Methods: The medical records of 24,201 cases of unexplained infertility among a total of 31,684 intrauterine insemination treatment cases, (which benefited by 'National Medical-aid Program for ART in 2011') were used for this analysis. Results: Woman's age (OR=0.94), frequency of IUI (OR=0.86), and treatment type (OR=1.54) were significant factors on pregnancy rates in the logistic regression analysis. Conclusion: Factors, such as the age of the infertile woman, frequency of IUI, and treatment type used to induce ovulation were shown to positively influence pregnancy rate. However, the age of the spouse was not a significant variable. Infertile couples having unprotected sexual intercourse with unexplained infertility had priority. The results demonstrated that about 70% of infertile Korean couples had unexplained infertility. This was a higher rate of unexplained infertility than that of the clinical standard. Therefore, we should assess for causes through future studies. In addition, affective or emotional factors influencing unexplained infertility need to be researched further.

• 한국전자통신학회논문지
• /
• 제6권5호
• /
• pp.731-737
• /
• 2011

본 연구는 인터넷 이용자들을 대상으로 개인정보 유출 가능성에 따른 심리적 불안에 대해서 논의하였다. 성별, 인터넷 이용량, 사이트 가입 수, 전자상거래 빈도에 따라 개인정보 유출 가능성에 대한 심리적 불안이 어떠한 차이를 나타내는지 알아보았다. 분석 결과 여성이 남성보다 심리적 불안이 더 크게 나타났으며, 인터넷을 많이 이용할수록 심리적 불안이 크게 나타났다. 하지만 사이트 가입 수나 한 달 평균 전자 상거래 빈도에 따른 개인정보 유출 가능성에 대한 심리적 불안에는 차이가 나타나지 않았다.

• Steel and Composite Structures
• /
• 제23권6호
• /
• pp.691-714
• /
• 2017

Rotating fluid induced vibration and instability of embedded piezoelectric nano-composite separators subjected to magnetic and electric fields is the main contribution of present work. The separator is modeled with cylindrical shell element and the structural damping effects are considered by Kelvin-Voigt model. Single-walled carbon nanotubes (SWCNTs) are used as reinforcement and effective material properties are obtained by mixture rule. The perturbation velocity potential in conjunction with the linearized Bernoulli formula is used for describing the rotating fluid motion. The orthotropic surrounding elastic medium is considered by spring, damper and shear constants. The governing equations are derived on the bases of classical shell theory (CST), first order shear deformation theory (FSDT) and sinusoidal shear deformation theory (SSDT). The nonlinear frequency and critical angular fluid velocity are calculated by differential quadrature method (DQM). The detailed parametric study is conducted, focusing on the combined effects of the external voltage, magnetic field, visco-Pasternak foundation, structural damping and volume percent of SWCNTs on the stability of structure. The numerical results are validated with other published works as well as comparing results obtained by three theories. Numerical results indicate that with increasing volume fraction of SWCNTs, the frequency and critical angular fluid velocity are increased.

• 한국안전학회지
• /
• 제18권4호
• /
• pp.98-104
• /
• 2003

Various nondestructive evaluation (NDE) techniques have been studied to locate steel rebars of dowel, and to detect invisible damage such as voids and cracks inside concrete and debonding between rebars and concrete caused by corrosions and earthquakes. In this study, the aurhors developed 3-dimensional (3D) electromagnetic (EM) imaging technology to detect such damage and to identify exact location of steel rebars of dowel. The authors have developed sub-surface two-dimensional (2D) imaging technique using tomographic antenna array in previous works. In this study, extending the earlier analytical and experimental works on 2D image reconstruction, a 3D microwave imaging system using tomographic antenna array was developed, and multi-frequency technique was applied to improve quality of the reconstructed image and to reduce background noises. This paper presents the analytical expressions of numerical focusing procedures for 3D image reconstruction and numerical simulation to study the resolution of the system and the effectiveness of multi-frequency technique. Also, the design of 4?4 antenna array with switching devices is introduced as a preliminary study for the final design of whole array.