• Corrosion Science and Technology
• /
• v.19 no.2
• /
• pp.66-74
• /
• 2020

In this paper, the author's team has carried out a comparative experimental study on the corrosion characteristics of Q235 steel commonly used in large-scale storage tanks under the specific bottom water environment found with Russian and Daqing crude oil. It was found that there is a certain degree of uniform or local corrosion on the tank floor depending on the kind of bottom water. The bottom water corrosion of Daqing crude oil is a uniform corrosion caused by carbon dioxide. While the Russian crude oil bottom water corrosion is clearly local corrosion caused by co-corrosion of carbon dioxide and hydrogen sulfide, here the corrosion rate is obviously higher than that caused by Daqing crude oil. There are two modes of storage tank inspection and maintenance that have been currently adopted by Chinese refining and chemical enterprises: a regular inspection mode and a API581-2016 risk-based detection mode. These modes have been effectively combined to form an intelligent tank inspection and maintenance mode, software tools to support this intelligent inspection and maintenance management have been developed.

• Earthquakes and Structures
• /
• v.14 no.6
• /
• pp.505-523
• /
• 2018

Static pushover analyses of typical existing reinforced concrete frames, designed according to the previous generations of design codes in Greece, have established these structures' inelastic characteristics, namely overstrength, global ductility capacity and available behaviour factor q, under planar response. These were compared with the corresponding demands at the collapse limit state target performance point. The building stock considered accounted for the typical variability, among different generations of constructed buildings in Greece, in the form, the seismic design code in effect and the material characteristics. These static pushover analyses are extended, in the present study, in the time history domain. Consequently, the static analysis predictions are compared with Incremental Dynamic Analysis results herein, using a large number of spectrum compatible recorded base excitations of recent destructive earthquakes in Greece and abroad, following, for comparison, similar conventional limiting failure criteria as before. It is shown that the buildings constructed in the 70s exhibit the least desirable behaviour, followed by the buildings constructed in the 60s. As the seismic codes evolved, there is a notable improvement for buildings of the 80s, when the seismic code introduced end member confinement and the requirement for a joint capacity criterion. Finally, buildings of the 90s, designed to modern codes exhibit an exceptionally good performance, as expected by the compliance of this code to currently enforced seismic provisions worldwide.

• Journal of Institute of Control, Robotics and Systems
• /
• v.18 no.2
• /
• pp.149-155
• /
• 2012

This paper provides an efficient model predictive control for the output voltage control of three-phase inverter system which includes output LC filters. Use of SVPWM (Space Vector Pulse-Width-Modulation) and the rotating d-q frame is made to obtain an input constrained dynamic model of the inverter system. From the measured/estimated output current and reference output voltage, corresponding equilibrium values of the inductor current and the control input are computed. Derivation of a feasible and invariant set around the equilibrium state is made and then a receding horizon strategy which steers the current state deep into the invariant set is proposed. In order to remove offset error, use of disturbance observer is made in the form of state estimator. The efficacy of the proposed method is verified through simulations.

• Journal of Institute of Control, Robotics and Systems
• /
• v.15 no.2
• /
• pp.148-154
• /
• 2009

In this paper, an embedded Kalman filter for a time-delayed controller is designed on an FPGA to estimate accelerations of the robot arm. When the time-delayed controller is used as a controller, the inertia estimation along with accelerations is needed to form the control law. Although the time-delayed controller is known to be robust to cancel out uncertainties in the nonlinear systems, performances are very much dependent upon estimating the acceleration term ${\ddot{q}}(t-{\lambda})$ along with inertia estimation ${\hat{D}}(t-{\lambda})$. Estimating accelerations using the finite difference method is quite simple, but the accuracy of estimation is poor specially when the robot moves slowly. To estimate accelerations more accurately, various filters such as the least square fit filter and the Kalman filter are introduced and implemented on an FPGA chip. Experimental studies of following the desired trajectory are conducted to show the performance of the controller. Performances of different filters are investigated experimentally and compared.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.86-89
• /
• 2004

To estimate a electrical performance of the extra high voltage XLPE cable the discharge properties due to shift of void position were investigated. The ${\phi}-q-n$ properties have been measured at room temperature by rising voltage ratio of 0.5[kV]. An obtained data was stored to personal computer through A/D converter. The period of applied wave form and discharge values were divided into 64 parts and discharge values generated during 10 seconds were accumulated by phases. As a result, it was confirmed that the charge, phase angle and counts of discharge changed due to void position.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.256-257
• /
• 2005

To estimate a electrical performance of the extra high voltage XLPE cable the discharge properties due to shift of void position were investigated. The $\Phi-q-n$ properties have been measured at room temperature by rising voltage ratio of 0.5[kV]. An obtained data was stored to personal computer through A/D converter. The period of applied wave form and discharge values were divided into 64 parts and discharge values generated during 10 seconds were accumulated by phases. As a result, it was confirmed that the charge, phase angle and counts of discharge changed due to void position.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.32 no.3
• /
• pp.256-261
• /
• 2019

The use of military lithium batteries in this field accelerates the generation of internal pressure because the active materials, lithium and the electrolyte, react to form sulfur dioxide gas. This also reduces the amount of electrolyte. In this condition, batteries can 'vent' or 'explode' especially when completely discharged. Such venting and explosion can be regarded as a safety accident, as toxic gases and shrapnel are ejected from the batteries which can harm the user. A DTaQ was carried out in 2017 as a quality problem solution project to solve this safety issue. A protection circuit was thereby developed, which included a micro controller unit (MCU) which can stop battery usage when in an over-discharging state by sensing its low-voltage condition. In 2018, this concept was expanded to lithium batteries for the remote controlled ammunition system. This paper reports results of the improved performance.

• Geosystem Engineering
• /
• v.21 no.6
• /
• pp.344-351
• /
• 2018

It is reported that the flooding rate in low permeability sandstones is low and the oil recovery is hard to increase after water breakthrough. Understanding characteristics of waterflood is hence important for the recovery improvement. In this work, flooding tests on low permeability sandstones were conducted. The corresponding flooding characteristics were investigated by means of CT scanning and Nuclear Magnetic Resonance. Effects of irreducible water and different rates were also discussed in detail. Experimental results reveal a piston-like displacement at a low rate in low permeability samples. The saturation profile is steep and almost vertical to the forward direction. The results at a low rate confirm that once water broke through, increasing the flooding rate or flooding time can hardly reduce the remaining oil inside the sample. It is probably due to the high pore-throat ratio proven by rate-controlled mercury. Results also confirm that the presence of initial water enhanced sweep efficiency substantially. On one hand, because water had previously occupied the small pores, the subsequent oil can only invade relatively large pores and became more movable. On the other hand, stable collars can not form due to the steep front, which may suppress the snap-off.

• The Journal of Asian Finance, Economics and Business
• /
• v.8 no.2
• /
• pp.973-979
• /
• 2021

The purpose of this paper is to examine the effect of tax planning on firm value of the non-financial firms listed in Vietnam, moderated by the state ownership. In this paper, effective tax rate is used to measure the tax planning; the state ownership is measured by the percentage of state equity holdings, and the firm value is measured by Tobin's Q. The data research is collected from audited financial statements and other statistical documents of 513 firms in the period of 2015-2019, provided by The FiinGroup (Vietnam). According to that, this paper uses quantitative research methods for the panel data. Regression analysis with GLS shows that the tax planning has a negative effect on firm value. In more detail, the association is not a variable in its direction when state ownership takes the role of a moderator. That means, in the perspective of principal-principal conflict, government should improve institutional environment to prevent firms form breaking the rules, especially accounting standards and principles. Assets allocation in tangible assets or making use of large size advantage should be taken into account. In the long run, firms should concentrate on the deployment of resources and the experience of knowledgeable practitioners to produce effective results.

• Journal of Information Science Theory and Practice
• /
• v.11 no.1
• /
• pp.1-13
• /
• 2023

This study determines how social media users (SMUs) verify the information they come across on the Internet. It determines SMUs' perception of online fact-checking services in terms of their ease of use, usefulness, and trust. By conducting a focus group discussion and key informant interviews, themes were derived in determining fact-checking practices while a survey was further conducted to determine such perceived ease of use, usefulness, and trust in fact-checking services. The thematic analysis revealed major information verification practices, such as cross-checking and verifying with other sources, inspecting comments and reactions, and confirming from personal and social networks. The results showed that SMUs considered fact-checking services easy to use. However, a concern was raised about their usefulness stemming from the delayed action in addressing the information issues that need to be verified. As to perceived trust, it was found that SMUs have reservations about fact-checking services. Finally, it is believed that fact-checking services are expected to be credible and need to be promoted to mitigate any form of fake news, particularly on social media platforms.