• Title/Summary/Keyword: Helmholtz

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Acoustic Modeling in a Gas Turbine Combustor with Backflow Using a Network Aproach (역류형 가스터빈 연소기에서 네트워크 접근법을 이용한 음향장 모델링)

  • Son, Juchan;Hong, Sumin;Hwang, Jeongjae;Kim, Min Kuk;Kim, Daesik
    • Journal of the Korean Society of Propulsion Engineers
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    • v.25 no.5
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    • pp.18-26
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    • 2021
  • In this work, we have developed a 1D network model aimed at predicting eigenvalues for resonance frequency analysis in a lab-scale industrial gas turbine single nozzle combustion system. Modern industrial gas turbines generally adopt combustors with very complex geometry and flow path to meet various design requirements simultaneously. The current study has developed a network model for combustion systems with backflow at the same axial location. The modeling results of resonance frequencies and mode distributions for a given system using the network model were validated from comparisons with prediction results using a 3D Helmholtz solver.

The effect of UV-C irradiation and EDTA on the uptake of Co2+ by antimony oxide in the presence and absence of competing cations Ca2+ and Ni2+

  • Malinen, Leena;Repo, Eveliina;Harjula, Risto;Huittinen, Nina
    • Nuclear Engineering and Technology
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    • v.54 no.2
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    • pp.627-636
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    • 2022
  • In nuclear power plants and other nuclear facilities the removal of cobalt from radioactive liquid waste is needed to reduce the radioactivity concentration in effluents. In liquid wastes containing strong organic complexing agents such as EDTA cobalt removal can be problematic due to the high stability of the Co-EDTA complex. In this study, the removal of cobalt from NaNO3 solutions using antimony oxide (Sb2O3) synthesized from potassium hexahydroxoantimonate was investigated in the absence and presence of EDTA. The uptake studies on the ion exchange material were conducted both in the dark (absence of UV-light) and under UV-C irradiation. Ca2+ or Ni2+ were included in the experiments as competing cations to test the selectivity of the ion exchanger. Results show that UV-C irradiation noticeably enhances the cobalt sorption efficiency on the antimony oxide. It was shown that nickel decreased the sorption of cobalt to a higher extent than calcium. Finally, the sorption data collected for Co2+ on antimony oxide was modeled using six different isotherm models. The Sips model was found to be the most suitable model to describe the sorption process. The Dubinin-Radushkevich model was further used to calculate the adsorption energy, which was found to be 6.2 kJ mol-1.

Modeling and numerical simulation of electrostrictive materials and structures

  • Pechstein, Astrid;Krommer, Michael;Humer, Alexander
    • Smart Structures and Systems
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    • v.30 no.3
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    • pp.221-237
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    • 2022
  • This paper is concerned with nonlinear modeling and efficient numerical simulation of electrostrictive materials and structures. Two types of such materials are considered: relaxor ferroelectric ceramics and electrostrictive polymers. For ceramics, a geometrically linear formulation is developed, whereas polymers are studied in a geometrically nonlinear regime. In the paper, we focus on constitutive modeling first. For the reversible constitutive response under consideration, we introduce the augmented Helmholtz free energy, which is composed of a purely elastic part, a dielectric part and an augmentation term. For the elastic part, we involve an additive decomposition of the strain tensor into an elastic strain and an electrostrictive eigenstrain, which depends on the polarization of the material. In the geometrically nonlinear case, a corresponding multiplicative decomposition of the deformation gradient tensor replaces the additive strain decomposition used in the geometrically linear formulation. For the dielectric part, we first introduce the internal energy, to which a Legendre transformation is applied to compute the free energy. The augmentation term accounts for the contribution from vacuum to the energy. In our formulation, the augmented free energy depends not only on the strain and the electric field, but also on the polarization and an internal polarization; the latter two are internal variables. With the constitutive framework established, a Finite Element implementation is briefly discussed. We use high-order elements for the discretization of the independent variables, which include also the internal variables and, in case the material is assumed incompressible, the hydrostatic pressure, which is introduced as a Lagrange multiplier. The elements are implemented in the open source code Netgen/NGSolve. Finally, example problems are solved for both, relaxor ferroelectric ceramics and electrostrictive polymers. We focus on thin plate-type structures to show the efficiency of the numerical scheme and its applicability to thin electrostrictive structures.

Particle-motion-tracking Algorithm for the Evaluation of the Multi-physical Properties of Single Nanoparticles (단일 나노입자의 다중 물리량의 평가를 위한 입자 모션 트랙킹 알고리즘)

  • Park, Yeeun;Kang, Geeyoon;Park, Minsu;Noh, Hyowoong;Park, Hongsik
    • Journal of Sensor Science and Technology
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    • v.31 no.3
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    • pp.175-179
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    • 2022
  • The physical properties of biomaterials are important for their isolation and separation from body fluids. In particular, the precise evaluation of the multi-physical properties of single biomolecules is essential in that the correlation between physical and biological properties of specific biomolecule. However, the majority of scientific equipment, can only determine specific-physical properties of single nanoparticles, making the evaluation of the multi-physical properties difficult. The improvement of analytical techniques for the evaluation of multi-physical properties is therefore required in various research fields. In this study, we developed a motion-tracking algorithm to evaluate the multi-physical properties of single-nanoparticles by analyzing their behavior. We observed the Brownian motion and electric-field-induced drift of fluorescent nanoparticles injected in a microfluidic chip with two electrodes using confocal microscopy. The proposed algorithm is able to determine the size of the nanoparticles by i) removing the background noise from images, ii) tracking the motion of nanoparticles using the circular-Hough transform, iii) extracting the mean squared displacement (MSD) of the tracked nanoparticles, and iv) applying the MSD to the Stokes-Einstein equation. We compared the evaluated size of the nanoparticles with the size measured by SEM. We also determined the zeta-potential and surface-charge density of the nanoparticles using the extracted electrophoretic velocity and the Helmholtz-Smoluchowski equation. The proposed motion-tracking algorithm could be employed in various fields related to biomaterial analysis, such as exosome analysis.

Design for the Reflection Free Zone with the Adequate Initial Time Delay Gap at the Control Room (음향조정실에서 적절한 초기지연시간을 갖는 무반사지역의 설계연구)

  • Rhee, Esther
    • The Journal of the Acoustical Society of Korea
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    • v.26 no.1
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    • pp.32-41
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    • 2007
  • The control room has been usually designed by the consideration of only one listening position for the sound engineer. By this study. many listening positions with the very similar acoustical condition were located in the specific region, so-called 'the reflection free zone', where the several engineer could evaluate the quality of sound at the same time. For constructing the reflection free zone, the control room has been designed by the concept of the $LEDE^{TM}$, and the initial time delay gap has been controled by the structure of control room and the properties of sound-absorbing materials. diffuser, Helmholtz resonator and image source of sound. The occurrence of any harmful phenomena like the standing wave, acoustic focusing. coloring. Hass effect and flutter echo, has greatly reduced in the reflection free zone.

A Study on the Efficient Germination of Acacia(Robinia pseudoacacia) Seeds using Electromagnetic Fields Energy (전자기장 에너지를 이용한 아까시 종자의 효율적 발아에 관한 연구 )

  • Park Donghee;Kwak Yoonsik;Ko, Kyunbyoung;Kim Hagwone;Mun Cheol;Park Manbok;Song Seokil;Song Changick;Lim Sungmuk;Jung Hogi
    • Journal of Platform Technology
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    • v.12 no.1
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    • pp.119-127
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    • 2024
  • This paper utilized electromagnetic field energy as an external stimulus to enhance the germination rate of acacia(Robinia pseudoacacia) seeds. Electromagnetic field energy comprises three types: static magnetic field(SMF) energy, static electric field(SEF) energy, and microwave(MW) energy. When SMF energy was applied to seeds through a dry method for 90 minutes, the germination rate increased by more than 10% compared to the control group. Similarly, SEF energy applied through a dry method for 90 minutes resulted in an improvement of over 20% in the germination rate. Furthermore, when MW energy at 2.45 GHz was applied to the seeds through a wet method for 3 minutes, the germination rate increased by over 25%. Experimental results showed that seeds treated with MW energy exhibited the highest germination rate and the greatest sprout growth. Consequently, this paper confirms that treating seeds with MW energy through a wet method yields the most superior germination rate and seedling growth.

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Numerical Analysis and Verification of Sound Absorbing Properties of Perforated Plate (타공판의 등가 흡음 물성치 유도와 공명기로서의 흡음성능 해석)

  • Yoon, Gil-Ho;Kim, Ki-Hyun;Choi, Jung-Sik;Yun, Su-Hwan
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.2
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    • pp.139-144
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    • 2015
  • Recently, to realize sound-absorbing structures, we have to insert sound-absorbing materials into wall. These shapes are taken limitations because sound-absorbing materials should be fixed. Therefore, the sound absorption is changed by environment that used the sound-absorbing materials. On the other hand, we will take same effect without sound-absorbing material, if we change the shape of wall to sound absorbing structure. If we use this sound absorbing structure, we can get benefits by removing limitation of materials. Therefore we suggest perforated plate for effective sound-absorbing structure. We confirmed the function of sound-absorption of this structure using equivalent property. Then, we found the similarity between perforated plate and resonator. Also, we verify these theories through computer simulation by FEM(Finite Element Method). Finally, we validated that perforated plate has function of sound absorption without sound-absorbing material. This perforated plate is used for sound-absorbing material of buildings and transportations such as vehicle, train etc. Also, these results could be further used basic tool for design of sound-absorption structure.

Case Study on Groß Schönebeck EGS Project Research in Germany (독일 그로스 쉐네벡 EGS 실증 프로젝트 연구사례)

  • Min, Ki-Bok;Park, Sehyeok;Zimmermann, Gunter
    • Tunnel and Underground Space
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    • v.25 no.4
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    • pp.320-331
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    • 2015
  • This paper presents a case study of an enhanced geothermal system(EGS) demonstration project conducted in $Gro{\ss}$ $Sch{\ddot{o}}nebeck$, Northerm Germany, focusing on hydraulic stimulation. The project was conducted with doublet system in sandstone and volcanic formations at 4 - 4.4 km depth. Under normal faulting to strike-slip faulting stress regime, hydraulic stimulations were conducted at injection and production wells by massive waterfrac and gel-proppant fracturing. Injectivity index increased from $0.97m^3/(hr^*MPa)$ to $7.5m^3/(hr^*MPa)$ and productivity index increased from $2.4m^3/(hr^*MPa)$ to $10.1m^3/(hr^*MPa)$ by a series of hydraulic stimulations at both wells. After circulation tests through injection and production wells, however, productivity index decreased from $8.9m^3/(hr^*MPa)$ to $0.6m^3/(hr^*MPa)$ in two years. Slip tendency analysis for the stimulation in volcanic layer estimated the required pressure for shear slip and its preferred orientations and it showed reasonable match with actual stimulation results. Through the microseismicity observation for the stimulation of volcanic formation, only 80 seismic events with its moment magnitudes in -1.8<$M_W$<-1.0 were observed, which are unexpectedly low for EGS hydraulic stimulation.

Electrokinetic Studies on Nylon and Wool/Acid Dye System (나일론과 양모/산성염료계에 대한 계면동전위적 연구)

  • 박병기;김진우;김찬영
    • Textile Coloration and Finishing
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    • v.1 no.1
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    • pp.19-25
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    • 1989
  • In past, dye diffusion and dyeing rate in fibers have been emphasized in dyeing phenomena. However, in the light of the properties of colloids in the surface of disperse phase and dispersion, there exist specific characters such as adsorption or electric double layer, which seems to play important roles in determining the physiochemical properties in the dyeing system. Electrostatic bonding, hydrogen bonding and Van der Waals adsorption are common in dyeing as well as covalent bonding. Particularly, electrostatic bonding is premised on the existance of ionic radicals in fibers. The present study was aimed to clarify the electrokinetic phenomena of dyeing through the role of electric double layer by ion in amphoteric fibers with different ionic effects under different pH. Spectrophotometric analysis method was used to compare dyeing condition of surface, which can be detected by electrokinetic phenomena and the inner of fibers after deceleration of dyed fibers. Nylon and wool, the typical amphoteric fibers were dyed with monoazo acid dyes such as C.I. Acid Orange 20, and C.I. Acid Orange 10. Various combinations were prepared by combining pH, temperature and dye concentration, in order to generate streaming electric potential which were measured by microvolt meter and specific conductivity meter. The results were transformed to zeta potential by Helmholtz-Smoluchowski formular and to surface electric charge density by Suzawa formular, surface dye amount, and effective surface area of fibers. The amount of dyes of inner fibers were also measured by the Lambert-Beer’s law. The main results obtained are as follows. 1. By measuring zeta pontential, it was possible to detect the dyeing mechanism, surface charge density, surface dye amount and effective surface area concerning dye adsorption of the amphoteric fibers. 2. Zeta pontential increases in negative at low pH and high dye concentration in the process of dyeing. This implied that there existed ionic bond formation in the dyeing mechanism between acid dyes and amphoteric fibers. 3. Dibasic acid dye had little changing rate in zeta potential due to the difference in solubility of dye and in number of dissociated ions per dye molecule to bond with amino radicals of amphoteric fibers. The dye adsorption of mono basic acid dye was higher than that of dibasic acid dye. 4. The effective surface areas concerning dyeing were $6.3E+05\;cm^2/g$ in nylon, $1.6E+07\;cm^2/g$ in wool fiber being higher order of wool then nylon.

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The Vibration Effect by Induced Pulsation Pressure to the Fatigue Crack of the Dampener Fitting Welding Zone (항공기용 유압 펌프의 맥동 압력에 의한 감쇄기 용접부위 균열 개선 연구)

  • Shin, Jae Hyuk;Kim, Tae Hwan;Kang, Gu Heon;Ha, Do Jun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.7
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    • pp.677-687
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    • 2017
  • Aircraft can often be exposed to a variety of environments and vibrations such as engine, hydraulic pump, aerodynamic force. These may cause cracking and destruction of the mechanical structure and sub-components by high-cycle fatigue. The axial piston type pump which is usually applied to the aircraft hydraulic pump can be necessarily accompanied by the fluid pulsation by continuous rotation of the axial piston. The fatigue crack was identified at the dampener fitting welding zone to prevent vibration damping during the running of aircraft equipped with this type of pulsation hydraulic pump. In order to understand the root cause of this matter, fracture and component analyses were carried out and also integral type dampener fitting was applied to prevent recurrence of the crack as a subject of design improvements. Structural integrity stress analysis, fatigue analysis, qualification test and aircraft system equipped test was conducted to verify the design validity in application to integral type dampener fitting. The test results were sufficiently satisfactory with the demand lifetime of the material from the various types of test as conducted and the subject of design improvement in this study could be objectively evaluated that shall be applied to the operational aircraft.