• Title/Summary/Keyword: hydro-mechanical

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Stiffness loss in enzyme-induced carbonate precipitated sand with stress scenarios

  • Song, Jun Young;Sim, Youngjong;Yeom, Sun;Jang, Jaewon;Yun, Tae Sup
    • Geomechanics and Engineering
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    • v.20 no.2
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    • pp.165-174
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    • 2020
  • The enzyme-induced carbonate precipitation (EICP) method has been investigated to improve the hydro-mechanical properties of natural soil deposits. This study was conducted to explore the stiffness evolution during various stress scenarios. First, the optimal concentration of urea, CaCl2, and urease for the maximum efficiency of calcite precipitation was identified. The results show that the optimal recipe is 0.5 g/L and 0.9 g/L of urease for 0.5 M CaCl2 and 1 M CaCl2 solutions with a urea-CaCl2 molar ratio of 1.5. The shear stiffness of EICP-treated sands remains constant up to debonding stresses, and further loading induces the reduction of S-wave velocity. It was also found that the debonding stress at which stiffness loss occurs depends on the void ratio, not on cementation solution. Repeated loading-unloading deteriorates the bonding quality, thereby reducing the debonding stress. Scanning electron microscopy and X-ray images reveal that higher concentrations of CaCl2 solution facilitate heterogeneous nucleation to form larger CaCO3 nodules and 11-12 % of CaCO3 forms at the interparticle contact as the main contributor to the evolution of shear stiffness.

TECHNIQUES FOR INTERGRANULAR CRACK FORMATION AND ASSESSMENT IN ALLOY 600 BASE AND ALLOY 182 WELD METALS

  • LEE, TAE HYUN;HWANG, IL SOON;KIM, HONG DEOK;KIM, JI HYUN
    • Nuclear Engineering and Technology
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    • v.47 no.1
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    • pp.102-114
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    • 2015
  • Background: A technique developed to produce artificial intergranular stress corrosion cracks in structural components was applied to thick, forged alloy 600 base and alloy 182 weld metals for use in the qualification of nondestructive examination techniques for welded components in nuclear power plants. Methods: An externally controlled procedure was demonstrated to produce intergranular stress corrosion cracks that are comparable to service-induced cracks in both the base and weld metals. During the process of crack generation, an online direct current potential drop method using array probes was used to measure and monitor the sizes and shapes of the cracks. Results: A microstructural characterization of the produced cracks revealed realistic conformation of the crack faces unlike those in machined notches produced by an electrodischarge machine or simple fatigue loading using a universal testing machine. Conclusion: A comparison with a destructive metallographic examination showed that the characteristics, orientations, and sizes of the intergranular cracks produced in this study are highly reproducible.

Fluid flow profile in the "orthotropic plate+compressible viscous fluid+rigid wall" system under the action of the moving load on the plate

  • Akbarov, Surkay D.;Huseynova, Tarana V.
    • Coupled systems mechanics
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    • v.9 no.3
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    • pp.289-309
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    • 2020
  • The paper studies the fluid flow profile contained between the orthotropic plate and rigid wall under the action of the moving load on the plate and main attention is focused on the fluid velocity profile in the load moving direction. It is assumed that the plate material is orthotropic one and the fluid is viscous and barotropic compressible. The plane-strain state in the plate and the plane flow of the fluid is considered. The motion of the plate is described by utilizing the exact equations of elastodynamics for anisotropic bodies, however, the flow of the fluid by utilizing the linearized Navier-Stokes equations. For the solution of the corresponding boundary value problem, the moving coordinate system associated with the moving load is introduced, after which the exponential Fourier transformation is employed with respect to the coordinate which indicates the distance of the material points from the moving load. The exact analytical expressions for the Fourier transforms of the sought values are obtained, the originals of which are determined numerically. Presented numerical results and their analyses are focused on the question of how the moving load acting on the face plane of the plate which is not in the contact with the fluid can cause the fluid flow and what type profile has this flow along the thickness direction of the strip filled by the fluid and, finally, how this profile changes ahead and behind with the distance of the moving load.

A Survey of Distributed Engine Control Technology for Aircraft Gas Turbine Engine (항공용 가스터빈 엔진의 분산제어기술 발전 동향)

  • Jung, Chihoon;Park, Iksoo;Kim, JungHoe;Min, Seongki
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.1127-1134
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    • 2017
  • Gas turbine engine control was originated from a single hydro-mechanical governor for fuel metering and changed to 1970s' DEEC and then today's centralized FADEC. In order to attain the goal of improvement of control performance, application of PHM technology, and reduction of system weight, it is necessary to make a transition to distributed engine control. This paper describes the concept and roadmap of distributed control, collaborative efforts of government and industry for successful development of the system, and technical challenges for the system.

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Study on the pressure self-adaptive water-tight junction box in underwater vehicle

  • Huang, Haocai;Ye, Yanying;Leng, Jianxing;Yuan, Zhuoli;Chen, Ying
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.4 no.3
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    • pp.302-312
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    • 2012
  • Underwater vehicles play a very important role in underwater engineering. Water-tight junction box (WJB) is one of the key components in underwater vehicle. This paper puts forward a pressure self-adaptive water-tight junction box (PSAWJB) which improves the reliability of the WJB significantly by solving the sealing and pressure problems in conventional WJB design. By redundancy design method, the pressure self-adaptive equalizer (PSAE) is designed in such a way that it consists of a piston pressure-adaptive compensator (PPAC) and a titanium film pressure-adaptive compensator (TFPAC). According to hydro-mechanical simulations, the operating volume of the PSAE is more than or equal to 11.6 % of the volume of WJB liquid system. Furthermore, the required operating volume of the PSAE also increases as the gas content of oil, hydrostatic pressure or temperature difference increases. The reliability of the PSAWJB is proved by hyperbaric chamber tests.

A Study on the Output Stabilization of the Nd:YAG Laser by the Monitoring of Capacitor Charging Voltage

  • Noh, Ki-Kyong;Song, Kum-Young;Park, Jin-Young;Hong, Jung-Hwan;Park, Sung-Joon;Kim, Hee-Je
    • KIEE International Transactions on Electrophysics and Applications
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    • v.4C no.3
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    • pp.96-100
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    • 2004
  • The Nd: YAG laser is commonly used throughout many fields such as accurate material processing, IC marking, semiconductor annealing, medical operation devices, etc., due to the fact that it has good thermal and mechanical properties and is easy to maintain. In materials processing, it is essential to vary the laser power density for specific materials. The laser power density can be mainly controlled by the current pulse width and pulse repetition rate. It is important to control the laser energy in those fields using a pulsed laser. In this paper we propose the constant-frequency current resonant half-bridge converter and monitoring of capacitor charging voltage. This laser power supply is designed and fabricated to have less switching loss, compact size, isolation with primary and secondary transformers, and detection of capacitor charging voltage. Also, the output stabilization characteristics of this Nd: YAG laser system are investigated. The test results are described as a function of laser output energy and flashlamp arc discharging constant. At the energy storage capacitor charges constant voltage, the laser output power is 2.3% error range in 600[V].

Primary Water Stress Corrosion Crack Growth Rate Tests for Base Metal and Weld of Ni-Cr-Fe Alloy (니켈 합금 모재 및 용접재의 일차수응력부식균열 균열성장속도 시험)

  • Lee, Jong Hoon
    • Corrosion Science and Technology
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    • v.18 no.1
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    • pp.33-38
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    • 2019
  • Alloy 600/182 with excellent mechanical/chemical properties have been utilized for nuclear power plants. Although both alloys are known to have superior corrosion resistance, stress corrosion cracking failure has been an issue in primary water environment of nuclear power plants. Therefore, primary water stress corrosion crack (PWSCC) growth rate tests were conducted to investigate crack growth properties of Alloy 600/182. To investigate PWSCC growth rate, test facilities including water chemistry loop, autoclave, and loading system were constructed. In PWSCC crack growth rate tests, half compact-tension specimens were manufactured. These specimens were then placed inside of the autoclave connected to the loop to provide primary water environment. Tested conditions were set at temperature of $360^{\circ}C$ and pressure of 20MPa. Real time crack growth rates of specimens inside the autoclave were measured by Direct Current potential drop (DCPD) method. To confirm inter-granular (IG) crack as a characteristic of PWSCC, fracture surfaces of tested specimens were observed by SEM. Finally, crack growth rate was derived in a specific stress intensity factor (K) range and similarity with overseas database was identified.

Performance analysis of the passive safety features of iPOWER under Fukushima-like accident conditions

  • Kang, Sang Hee;Lee, Sang Won;Kang, Hyun Gook
    • Nuclear Engineering and Technology
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    • v.51 no.3
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    • pp.676-682
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    • 2019
  • After the Fukushima Daiichi accident, there has been an increasing preference for passive safety features in the nuclear power industry. Some passive safety systems require limited active components to trigger subsequent passive operation. Under very serious accident conditions, passive safety features could be rendered inoperable or damaged. This study evaluates (i) the performance and effectiveness of the passive safety features of iPOWER (innovative Power Reactor), and (ii) whether a severe accident condition could be reached if the passive safety systems are damaged, namely the case of heat exchanger tube rupture. Analysis results show that the reactor coolant system remains in the hot shutdown condition without operator actions or electricity for over 72 h when the passive auxiliary feedwater systems (PAFSs) are operable without damage. However, heat exchanger tube rupture in the PAFS leads to core damage after about 18 h. Such results demonstrate that, to enhance the safety of iPOWER, maintaining the integrity of the PAFS is critical, and therefore additional protections for PAFS are necessary. To improve the reliability of iPOWER, additional battery sets are necessary for the passive safety systems using limited active components for accident mitigation under such extreme circumstances.

Detection and Analysis of Discharge Pulses by Failure Mechanisms of the Separator inside Lithium-Ion Batteries (리튬이온 배터리의 분리막 손상 요인별 방전펄스의 검출과 분석)

  • Lim, Seung-Hyun;Lee, Gyeong-Yeol;Kim, Nam-Hoon;Kim, Dong-Eon;Kil, Gyung-Suk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.34 no.5
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    • pp.327-332
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    • 2021
  • Lithium-ion batteries (LIBs) have become a main energy storage device in various applications, such as portable appliances, renewable energy facilities, and electric vehicles. However, the poor thermal stability of LIBs may cause explosion or fire. The thermal runaway is the result of a failure of the separator inside LIB. Damages like tearing, piercing, and collapsing of the separator were simulated in a mechanical, an electrical, and a thermal way, and small discharge pulses of a few mV were detected at the time of separator damages. From the experimental results, this paper provided a method that can identify the separator failure before thermal runaway in the aspect of a potential explosion and fire prevention measures.

The importance of applying an appropriate approach to modelling wastewater treatment plants

  • Dzubur, Alma;Serdarevic, Amra
    • Coupled systems mechanics
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    • v.11 no.2
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    • pp.121-132
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    • 2022
  • Wastewater treatment plants (WWTPs) are designed and built to remove contaminants from wastewater. WWTPs are composed of various facilities equipped with hydro-mechanical and electrical equipment. This paper presents a comparison of two different approaches for WWTPs modelling. Static modelling is suitable for determining the dimensions of facilities and equipment capacity. The special significance of this approach is for the design of new plants, i.e., when a very small number of input data on the quantities and composition of the influent wastewater is available. Dynamic modelling is expensive, time consuming and requires great expertise in the use of simulators, models and very good understanding of the treatment processes. Also, dynamic modelling is very important to use for optimization, consideration of future scenarios and also possible scenarios on the plant. The comparison of two approaches was made on the input data from the biggest and most important plant in Bosnia and Herzegovina (B&H)-WWTP Butila (Sarajevo). The main idea is to show the differences between two demanding accesses. It is important to know how to apply an adequate approach to research and solve the set task. The II phase of the plant Butila, which includes the removal of nutrients, is planned in several years and therefore the importance of research has increased.