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Power Transmission from a Vibrating Mass to a Supporting Elate through Isolators (능동 및 수동격리기를 적용한 진동계에 있어서 힘의 전달에 관한 연구)

  • Jin-Woo Lee;Colin H. Hansen
    • Journal of the Korean Society of Safety
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    • v.16 no.4
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    • pp.200-207
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    • 2001
  • The transmission of harmonic vibratory power form a vibrating rigid body into a supporting plate through passive and active isolators is investigated theoretically and experimentally. The theoretical model allows for the transmission of vertical and horizontal harmonic forces and moments about all three coordinate sun. The experiment is to use vibration actuators attached to the intermediate mass of the two-stage mount to minimize the rotational and translational vibration of the intermediate mass. The performance is done by measuring the vibration at the error sensors due to the primary vibration source and measuring the transfer functions from the control sources to the error sensors. Results show that over a frequence range from 1 to 100Hz, transmission into the supporting plate can be reduced substantially by employing in parallel with existing passive isolators, active isolators adjusted to provide appropriate control force amplitudes.

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Closed-form optimum tuning formulas for passive Tuned Mass Dampers under benchmark excitations

  • Salvi, Jonathan;Rizzi, Egidio
    • Smart Structures and Systems
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    • v.17 no.2
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    • pp.231-256
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    • 2016
  • This study concerns the derivation of optimum tuning formulas for a passive Tuned Mass Damper (TMD) device, for the case of benchmark ideal excitations acting on a single-degree-of-freedom (SDOF) damped primary structure. The free TMD parameters are tuned first through a non-linear gradient-based optimisation algorithm, for the case of harmonic or white noise excitations, acting either as force on the SDOF primary structure or as base acceleration. The achieved optimum TMD parameters are successively interpolated according to appropriate analytical fitting proposals, by non-linear least squares, in order to produce simple and effective TMD tuning formulas. In particular, two fitting models are presented. The main proposal is composed of a simple polynomial relationship, refined within the fitting process, and constitutes the optimum choice. A second model refers to proper modifications of literature formulas for the case of an undamped primary structure. The results in terms of final (interpolated) optimum TMD parameters and of device effectiveness in reducing the structural dynamic response are finally displayed and discussed in detail, showing the wide and ready-to-use validity of the proposed optimisation procedure and achieved tuning formulas. Several post-tuning trials have been carried out as well on SDOF and MDOF shear-type frame buildings, by confirming the effective benefit provided by the proposed optimum TMD.

Enhancement of Downward-Facing Saturated Boiling Heat Transfer by the Cold Spray Technique

  • Sohag, Faruk A.;Beck, Faith R.;Mohanta, Lokanath;Cheung, Fan-Bill;Segall, Albert E.;Eden, Timothy J.;Potter, John K.
    • Nuclear Engineering and Technology
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    • v.49 no.1
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    • pp.124-133
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    • 2017
  • In-vessel retention by passive external reactor vessel cooling under severe accident conditions is a viable approach for retention of radioactive core melt within the reactor vessel. In this study, a new and versatile coating technique known as "cold spray" that can readily be applied to operating and advanced reactors was developed to form a microporous coating on the outer surface of a simulated reactor lower head. Quenching experiments were performed under simulated in-vessel retention by passive external reactor vessel cooling conditions using test vessels with and without cold spray coatings. Quantitative measurements show that for all angular locations on the vessel outer surface, the local critical heat flux (CHF) values for the coated vessel were consistently higher than the corresponding CHF values for the bare vessel. However, it was also observed for both coated and uncoated surfaces that the local rate of boiling and local CHF limit vary appreciably along the outer surface of the test vessel. Nonetheless, results of this intriguing study clearly show that the use of cold spray coatings could enhance the local CHF limit for downward-facing boiling by > 88%.

Passive and Cost Effective People Indoor Location Tracking System for Ubiquitous Healthcare (유비쿼터스 헬스케어를 위한 저비용, 수동형 실내 위치추적 시스템)

  • Chung Wan-Young;Singh Vinay Kumar;Lim Hyo-Taek
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2006.05a
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    • pp.430-433
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    • 2006
  • Wireless sensor network plays a prominent role in tracking the location of the target outdoor and indoor. This paper describes the implementation of the passive indoor location tracking system using ultrasonic and RF technologies that provides accurate location in the form of user space and position in three dimensions. Our system used a combination of RF and ultrasonic technologies to provide a location-support service to users and applicants. Ceiling-mounted beacons were spread through the building, publishing location information on an RF signal. The person carried a listener and the listener determined the location by calculating the distance from three beacons using triangulation algorithm.

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Passive and Cost Effective People Indoor Location Tracking System for Ubiquitous Healthcare (유비쿼터스 헬스케어를 위한 저비용, 수동형 실내 위치추적 시스템)

  • Chung Wan-Young;Singh Vinay Kumar;Lim Hyo-Taek
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.6
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    • pp.1119-1123
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    • 2006
  • Wireless sensor network plays a prominent role in tracking the location of the target outdoor or indoor. This paper describes the implementation of the passive indoor location tracking system using ultrasonic and RF technologies that provides accurate location in the form of user space and position in three dimensions. Our system used a combination of RF and ultrasonic technologies to provide a location-support service to users and applicants. Ceiling-mounted beacons were spread through the building, publishing location information on an RF signal. The person carried a listener and the listener determined the location by calculating the distance from three beacons using triangulation algorithm.

Development and validation of diffusion based CFD model for modelling of hydrogen and carbon monoxide recombination in passive autocatalytic recombiner

  • Bhuvaneshwar Gera;Vishnu Verma;Jayanta Chattopadhyay
    • Nuclear Engineering and Technology
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    • v.55 no.9
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    • pp.3194-3201
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    • 2023
  • In water-cooled power reactor, hydrogen is generated in case of steam zirconium reaction during severe accident condition and later on in addition to hydrogen; CO is also generated during molten corium concrete interaction after reactor pressure vessel failure. Passive Autocatalytic Recombiners (PARs) are provided in the containment for hydrogen management. The performance of the PARs in presence of hydrogen and carbon monoxide along with air has been evaluated. Depending on the conditions, CO may either react with oxygen to form carbon dioxide (CO2) or act as catalyst poison, reducing the catalyst activity and hence the hydrogen conversion efficiency. CFD analysis has been carried out to determine the effect of CO on catalyst plate temperature for 2 & 4% v/v H2 and 1-4% v/v CO with air at the recombiner inlet for a reported experiment. The results of CFD simulations have been compared with the reported experimental data for the model validation. The reaction at the recombiner plate is modelled based on diffusion theory. The developed CFD model has been used to predict the maximum catalyst temperature and outlet species concentration for different inlet velocity and temperatures of the mixture gas. The obtained results were used to fit a correlation for obtaining removal rate of carbon monoxide inside PAR as a function of inlet velocity and concentrations.

Environmental Modeling and Thermal Comfort in Buildings in Hot and Humid Tropical Climates

  • Muhammad Awaluddin Hamdy;Baharuddin Hamzah;Ria Wikantari;Rosady Mulyadi
    • Architectural research
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    • v.25 no.4
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    • pp.73-84
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    • 2023
  • Indoor thermal conditions greatly affect the health and comfort of humans who occupy the space in it. The purpose of this research is to analyze the influence of water and vegetation elements as a microclimate modifier in buildings to obtain thermal comfort through the study of thermal environment models. This research covers two objects, namely public buildings and housing in Makassar City, South Sulawesi Prov-ince - Indonesia. Quantitative methods through field surveys and measurements based on thermal and personal variables. Data analysis based on ASHRAE 55 2020 standard. The data was processed with a parametric statistical approach and then simulated with the Computational Fluid Dynamics (CFD) simulation method to find a thermal prediction model. The model was made by increasing the ventilation area by 2.0 m2, adding 10% vegetation with shade plant characteristics, moving water features in the form of fountains and increasing the pool area by 15% to obtain PMV + 0.23, PPD + 8%, TSV-1 - +0, Ta_25.7℃, and relative humidity 63.5 - 66%. The evaluation shows that the operating temperature can analyze the visitor's comfort temperature range of >80% and comply with the ASHRAE 55-2020 standard. It is concluded that water elements and indoor vegetation can be microclimate modifiers in buildings to create desired comfort conditions and adaptive con-trols in buildings such as the arrangement of water elements and vegetation and ventilation systems to provide passive cooling effects in buildings.

Surface and Corrosion Properties of Electrolytic Polished 316L Stainless Steel by Double Melting (VIM and VAR)

  • Hyunseung Lee;Gangsan Kim;Seungho Han;Man-Sik Kong;Jung-Yeul Yun;Si Young Chang
    • Journal of Korea Foundry Society
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    • v.43 no.5
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    • pp.223-229
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    • 2023
  • In this study, STS316L produced by a double-melting process involving vacuum induction melting (VIM) and vacuum arc remelting (VAR) was subjected to extrusion and drawing to form a tube and was subsequently electrolytic polished (EP). The grain size of the obtained STS316L without EP was approximately 55 ㎛, with no difference found after EP. The thickness of the EP layer was measured by AES and TEM, showing values of approximately 10 nm and 15 nm, respectively. After EP, the Cr/Fe and CrO/FeO ratios of the passive layer increased from 1.48 to 1.62 and from 2.15 to 2.26, respectively, while the surface roughness decreased significantly from 0.255 to 0.024 ㎛. Consequently, the corrosion rate decreased in both NaCl and HCl solutions after the EP process. Additionally, the amounts of eluted Cr and Fe ions were reduced from 1.2 to 0.8 ppb and 10.3 to 0.8 ppb, respectively. Furthermore, polarization tests revealed that STS316L treated with EP required a lower current density to reach a passive state, indicating that corrosion behavior was retarded.

Analysis of Two Moving Platform Passive Emitter Location with Continuously Measurable Parameters (2개의 이동하는 수신기를 이용한 측정 정보별 고정 신호원의 위치 추정 성능 분석)

  • Park, Jin-Oh;Lee, Moon Seok;Park, Young-Mi
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.9
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    • pp.157-164
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    • 2014
  • The accuracy of instantaneous passive emitter localization varies with sensing platforms and measurable parameters. Appropriate combination of instantaneous measurable parameters have more accurate localization performance than a single parameter based localization in general. Emitter localization is preferred to use a small number of receivers as possible for the efficiency of strategic management in the field of modern electronic warfare support. For this reason, we compare CRLB (Cramer-Rao lower bound) of two moving platform with various measurable parameters to search a appropriate choice of parameters for the better localization performance through the x-y axis CEP (circular error probable) derived form CLRB. In addition, we present the relation of the localization performance and accuracy of measurable parameters.

Lateral Earth Pressures Acting on Passive Piles (수동(受動)말뚝에 작용(作用)하는 측방토압(側方土壓))

  • Hong, Won Pyo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.4 no.2
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    • pp.77-88
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    • 1984
  • By investigating the characteristics of various factors about soil and pile containing in the theoretical equations of lateral earth pressures acting on a row of passive piles which have been already presented in the previous. papers, the equations are arranged as a simple form which is convenient to use. The simplified equation is examined so as to be also utilized to single passive pile. And a discussion is carried out on the method how to apply the equations to field. As the result of this study, the equations can be arranged as a simple linear equation with the coefficients of lateral force Kp1 and Kp2. And the simple linear equation is composed of cohesion c and earth pressures σH acting on backside of pile's row against the direction of soil deformation. In order to apply this equation to field, the active earth pressure can be considered as the earth pressure σH. The validity of this consideration is justified by comparing the theoretical values of lateral earth pressures acting on piles with the values observed in field.

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