• Title/Summary/Keyword: Polytechnic analysis

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Analysis of characteristics of sediment transport in sewers by densimetric Froude number (밀도프루드수에 의한 하수관로 침전물 이송 특성 분석)

  • Park, Kyoohong;Lee, Taehoon;Yu, Soonyu;Kang, Byongjun;Hyun, Kirim
    • Journal of Korean Society of Water and Wastewater
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    • v.34 no.1
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    • pp.45-52
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    • 2020
  • Even though sewers have been conventionally designed to prevent from sediment deposition using a specified minimum velocity or shear stress at a particular depth of flow or with a particular frequency of occurrence, it was appreciated that these methods do not consider the characteristics and concentration of the sediment and the specific hydraulic conditions of the sewer with sediment. In this study, a densimetric Froude number formula was suggested considering particle diameter and volumetric concentration of the sediment as well as flow depth and flowrate, based on several domestic field inspections, which was compared with other formulas proposed by previous investigators. When the sediment concentration was not considered, the calibration coefficient of 0.125-1.5 to the densimetric Froude numbers of this study was needed to obtain the similar ones with previous investigators'. For the densimetric Froude number formula obtained with consideration of sediment concentration, the exponent value of term Cv was almost the same as that of previous results and that of d50/Rh was similar for Fr < 2.2.

A Study of a Wideband Acoustic Transducer for Underwater Communication Using 1-3 Type Piezoelectric Transducer (1-3형 압전 복합체를 이용한 광대역 수중 통신용 음향 트랜스듀서에 관한 연구)

  • Lee, Kyung-Woo;So, Hyoung-Jong;Lim, Sil-Mook;Kim, Won-Ho;Cho, Wun-Hyun
    • Journal of Ocean Engineering and Technology
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    • v.22 no.2
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    • pp.65-71
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    • 2008
  • Recently, many researches in relation to data transmission with faster speed and greater volume, many researches have been carried out on sonar systems for underwater communication. According to these researches, an acoustic transducer for underwater communication requires wide bandwidth properties. In domestic researches for underwater communication sonar, an operating frequency in the range of $20{\sim}40\;kHz$ is used. In this paper, we propose anon-resonance type acoustic transducer for underwater communication. The TVR (transmitting voltage response) characteristics increased linearly as the frequency increased, and the RVS (receiving voltage sensitivity) characteristics were constant as the frequency increased. Traditional techniques for wide bandwidth transducershave a limit and a transmission loss difference at lower and higher frequency operating ranges. In this paper, the new transducer proposed decreased the transmission loss under some conditions. It was optimized with the FE analysis tool (ATILA) and evaluated using the TVR and the RVS characteristics in the range of $10{\sim}90\;kHz$. The value of TVR was 138 dB at 20 kHz and 148 dB at 40 kHz, and the differences was 12 dB. The value of RVS was $195{\pm}2\;dB$ and nearly constant. From theseresults, it is certain that the developed transducers can be used for an underwater communication network in the 1.3 km range with both a 20 kHz bandwidth and 30 kHz center frequency.

Accuracy Analysis of Magnetic Resonance Angiography and Computed Tomography Angiography Using a Flow Experimental Model

  • Heo, Yeong-Cheol;Lee, Hae-Kag;Park, Cheol-Soo;Cho, Jae-Hwan
    • Journal of Magnetics
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    • v.20 no.1
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    • pp.40-46
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    • 2015
  • This study investigated the accuracy of magnetic resonance angiography (MRA) and computed tomography angiography (CTA) in terms of reflecting the actual vascular length. Three-dimensional time of flight (3D TOF) MRA, 3D contrast-enhanced (CE) MRA, volume-rendering after CTA and maximum intensity projection were investigated using a flow model phantom with a diameter of 2.11 mm and area of $0.26cm^2$. 1.5 and 3.0 Tesla devices were used for 3D TOF MRA and 3D CE MRA. CTA was investigated using 16 and 64 channel CT scanners, and the images were transmitted and reconstructed by volume-rendering and maximum intensity projection, followed by conduit length measurement as described above. The smallest 3D TOF MRA measure was $2.51{\pm}0.12mm$ with a flow velocity of 40 cm/s using the 3.0 Tesla apparatus, and $2.57{\pm}0.07mm$ with a velocity of 71.5 cm/s using the 1.5 Tesla apparatus; both images were magnified from the actual measurement of 2.11 mm. The measurement with the 16 channel CT scanner was smaller ($3.83{\pm}0.37mm$) than the reconstructed image on maximum intensity projection. The images from CTA from examination apparatus and reconstruction technique were all larger than the actual measurement.

Stochastic vibration suppression analysis of an optimal bounded controlled sandwich beam with MR visco-elastomer core

  • Ying, Z.G.;Ni, Y.Q.;Duan, Y.F.
    • Smart Structures and Systems
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    • v.19 no.1
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    • pp.21-31
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    • 2017
  • To control the stochastic vibration of a vibration-sensitive instrument supported on a beam, the beam is designed as a sandwich structure with magneto-rheological visco-elastomer (MRVE) core. The MRVE has dynamic properties such as stiffness and damping adjustable by applied magnetic fields. To achieve better vibration control effectiveness, the optimal bounded parametric control for the MRVE sandwich beam with supported mass under stochastic and deterministic support motion excitations is proposed, and the stochastic and shock vibration suppression capability of the optimally controlled beam with multi-mode coupling is studied. The dynamic behavior of MRVE core is described by the visco-elastic Kelvin-Voigt model with a controllable parameter dependent on applied magnetic fields, and the parameter is considered as an active bounded control. The partial differential equations for horizontal and vertical coupling motions of the sandwich beam are obtained and converted into the multi-mode coupling vibration equations with the bounded nonlinear parametric control according to the Galerkin method. The vibration equations and corresponding performance index construct the optimal bounded parametric control problem. Then the dynamical programming equation for the control problem is derived based on the dynamical programming principle. The optimal bounded parametric control law is obtained by solving the programming equation with the bounded control constraint. The controlled vibration responses of the MRVE sandwich beam under stochastic and shock excitations are obtained by substituting the optimal bounded control into the vibration equations and solving them. The further remarkable vibration suppression capability of the optimal bounded control compared with the passive control and the influence of the control parameters on the stochastic vibration suppression effectiveness are illustrated with numerical results. The proposed optimal bounded parametric control strategy is applicable to smart visco-elastic composite structures under deterministic and stochastic excitations for improving vibration control effectiveness.

A Study on Establishment Method of Smart Factory Dataset for Artificial Intelligence (인공지능형 스마트공장 데이터셋 구축 방법에 관한 연구)

  • Park, Youn-Soo;Lee, Sang-Deok;Choi, Jeong-Hun
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.21 no.5
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    • pp.203-208
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    • 2021
  • At the manufacturing site, workers have been operating by inputting materials into the manufacturing process and leaving input records according to the work instructions, but product LOT tracking has been not possible due to many omissions. Recently, it is being carried out as a system to automatically input materials using RFID-Tag. In particular, the initial automatic recognition rate was good at 97 percent by automatically generating input information through RACK (TAG) ID and RACK input time analysis, but the automatic recognition rate continues to decrease due to multi-material RACK, TAG loss, and new product input issues. It is expected that it will contribute to increasing speed and yield (normal product ratio) in the overall production process by improving automatic recognition rate and real-time monitoring through the establishment of artificial intelligent smart factory datasets.

PR-Management and Branding of Media Channels with the Application of Social Networks

  • Shalman, Tatiana;Dobrianska, Viktoriia;Kokhan, Marianna;Pletsan, Khrystyna;Humenchuk, Anatolii
    • International Journal of Computer Science & Network Security
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    • v.21 no.7
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    • pp.70-76
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    • 2021
  • The relevance of intelligence involves the definition of such communication systems of PR-management and branding of media channels with the use of social networks, which are already implemented in practice by modern representatives of professional PR product. The purpose of the investigation is to determine the system of implementation of technologies of PR-management and branding of media channels with the use of social networks based on a survey of PR and brand of different media channels on the basis of a survey of brand managers and PR. 980 respondents from Ukraine took part in the survey. The survey was conducted on the Google-forms platform. The results outline a list of the most popular social networks and messengers for the implementation of PR management and branding technologies, including Facebook, Twitter, Google, LinkedIn, Tumblr; Telegram, WhatsApp, Viber, Skype. It is determined that the criteria of branding analysis are informativeness, centralization/distribution, content, feedback intensity. Identified 2 prospects for the development of branding in an interactive media environment (creation of a presentation system; integration of websites of social media and companies in universal centers). The criteria of general importance of the factors influencing the behavioral intention of consumers to use social media channels are presented (satisfaction, accessibility, perceived usefulness, trust, ease of use, attitude, social influence, self-efficacy). The meaning of the content of social media channels (public, informational and communication) is indicated. The practical significance of the study was to present the links between the criteria, development prospects and the values of branding factors.

Multi-player Contents for Upper Limb Rehabilitation based on VR (VR 기반의 상지 재활 훈련용 멀티플레이 콘텐츠)

  • Shin, Sung-Wook;Lee, Hyeok-Min;Moon, Ho-Sang;Chung, Sung-Taek
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.19 no.3
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    • pp.115-120
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    • 2019
  • Hemiplegic patients who suffered from a stroke struggle with a deterioration in upper limb functions, which can both be psychologically and physically discomforting; this can also limit patients' daily tasks involving any upper limb motions. In this study, we developed an assistive device for hemiplegic patients to improve their upper limb functions. It was manufactured to train patients by using their grip strength and the range of motion of the arm. Furthermore, we produced game contents in virtual reality to induce users' immersion and interaction. It was configured as a multi-player game to help ease the mental burden of receiving the training alone, hence allowing the patient and the caregiver to join the rehabilitation training simultaneously. The assistive device and game contents developed in this study enables patients and caregivers to easily check the degree of improvements in upper limb function by viewing quantitative analysis and visualized results.

Numerical Study on the Thermal Design of Lunar Terrain Imager System Loaded on the Korea Pathfinder Lunar Orbiter (시험용 달 궤도선의 광학탑재체 시스템 열설계에 대한 수치해석적 연구)

  • Kim, Taig Young;Chang, Su-Young;Heo, Haeng-Pal
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.4
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    • pp.309-318
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    • 2019
  • The thermal design of the Lunar Terrain Imager (LUTI) on the Korean Pathfinder Lunar Orbiter (KPLO) was performed and the soundness of the thermal design was verified by thermal analysis. The thermal environment of the lunar mission orbit should be reflected in the thermal design because the IR radiation of the lunar surface is important, unlike the earth orbit. The components or modules exposed to the outside of the satellite are insulated with MLI as much as possible, but the camera tube and the radiator are functionally exposed, so the thermal shield using the concept of radiation shape factor is mounted on the front to mitigate IR radiation. The IR emissivity is important in the front side of the radiator that receives little solar radiation, and components that are susceptible to thermal deformation such as the tube use a radiation heater to minimize the temperature gradient. Through the investigation of computational results, it was confirmed that the thermal design of LUTI is stable in various situations.

Current Control for an AFE Rectifier Using Space Vector PWM (공간벡터변조방식에 의한 AFE정류기의 전류제어)

  • Jeon, Cheol-Hwan;Hur, Jae-Jung;Yoon, Kyoung-Kuk;Yoo, Heui-Han;Kim, Sung-Hwan
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.25 no.4
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    • pp.498-503
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    • 2019
  • Electric propulsion ships are gaining widespread interest in the marine industry owing to extreme air pollution concerns. Consequently, several studies are actively being conducted for improving the power quality. Various methods have been developed that incorporate passive filters, notch filters, and active filters for reducing the harmonic content in the input current of a conventional diode front end rectifier. Among such filters, the active front end (AFE) rectifier is considered as an excellent technology. In this paper, current control for an AFE rectifier employing space vector PWM (Pulse Width Modulation) is proposed. Conventional current control methods for the AFE rectifier, hysteresis, SPWM (Sinusoidal Pulse Width Modulation), and SVPWM (Space Vector Pulse Width Modulation) were simulated by employing the PSIM software tool for analysis and comparisons. The results corroborate that SVPWM has the simplest structure and provides the best performance.

Analysis and Training Contents of Body Balance Ability using Range of Motion of Lumbar Spine and Center of Body Pressure (요추 관절가동범위와 신체압력중심을 이용한 신체균형능력 분석 및 훈련 콘텐츠)

  • Goo, Sejin;Kim, Dong-Yeon;Shin, Sung-Wook;Chung, Sung-Taek
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.19 no.1
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    • pp.279-287
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    • 2019
  • In this paper, we attempted to analyze the balance ability of the body by measuring changes in body motion and plantar pressure distribution. So we developed a program that can measure and analyze range of motion and center of body pressure using inertial measurement unit(IMU) and FSR(Force Sensing Resistor) sensor, we also produced a contents that can help improve the balance ability. The quantitative values of range of motion and center of body pressure measured by this program are visualized in real time so that the user can easily recognize the results. In addition, the contents were designed to be adjusted according to the direction of improving the balance ability by adjusting the difficulty level based on the measured balance information. This can be achieved by increasing the concentration and participation will by using visual feedback method that proceeds while watching moving objects according to the user's motion.