• Journal of Drive and Control
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• v.19 no.1
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• pp.51-61
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• 2022

This paper presents a model-free system based on a framework of a backstepping sliding mode control (BSMC) with a radial basis function neural network (RBFNN) and adaptive mechanism for electro-hydraulic systems (EHSs). First, an EHS mathematical model was dedicatedly derived to understand the system behavior. Based on the system structure, BSMC was employed to satisfy the output performance. Due to the highly nonlinear characteristics and the presence of parametric uncertainties, a model-free approximator based on an RBFNN was developed to compensate for the EHS dynamics, thus addressing the difficulty in the requirement of system information. Adaptive laws based on the actor-critic neural network (ACNN) were implemented to suppress the existing error in the approximation and satisfy system qualification. The stability of the closed-loop system was theoretically proven by the Lyapunov function. To evaluate the effectiveness of the proposed algorithm, proportional-integrated-derivative (PID) and improved PID with ACNN (ACPID), which are considered two complete model-free methods, and adaptive backstepping sliding mode control, considered an ideal model-based method with the same adaptive laws, were used as two benchmark control strategies in a comparative simulation. The simulated results validated the superiority of the proposed algorithm in achieving nearly the same performance as the ideal adaptive BSMC.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.01a
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• pp.443-445
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• 2023

Following the global financial crisis, the global value chain contracted, and characteristics of "reverse globalization" of the economy and trade gradually emerged. This is due to the term "reverse globalization" referring to a shift away from globalization. Within a short period of time, the phenomenon known as "reverse globalization" developed as an inescapable obstacle, coinciding with the development and dissemination of the COVID-19 virus. At some time in the distant future, the "reverse globalization" of economic trade and the "globalization" of the digital economy will co-dominate the shifting trend of the global economic landscape. This will happen gradually over time. The goal of this research is to look at the minor changes that happened in the methods and techniques used by the economic mechanism known as "globalization against the flow." It employs Chinese smart manufacturing companies as a model and proposes a digital drive model to investigate the prospects and constraints of smart manufacturing technology enterprise innovation development under "reverse globalization," with the goal of establishing a digital innovation development path. The theoretical insights given in this study have the potential to serve as a reference for China as it attempts to build a new growth pattern based on a double-cycle and promote a new type of globalization.

• IMMUNE NETWORK
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• v.21 no.2
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• pp.16.1-16.8
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• 2021

Patients with severe coronavirus disease 2019 (COVID-19) demonstrate dysregulated immune responses including exacerbated neutrophil functions. Massive neutrophil infiltrations accompanying neutrophil extracellular trap (NET) formations are also observed in patients with severe COVID-19. However, the mechanism underlying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced NET formation has not yet been elucidated. Here we show that 2 viral proteins encoded by SARS-CoV-2, the nucleocapsid protein and the whole spike protein, induce NET formation from neutrophils. NET formation was ROSindependent and was completely inhibited by the spleen tyrosine kinase inhibition. The inhibition of p38 MAPK, protein kinase C, and JNK signaling pathways also inhibited viral protein-induced NET formation. Our findings demonstrate one method by which SARSCoV-2 evades innate immunity and provide a potential target for therapeutics to treat patients with severe COVID-19.

• Journal of Microbiology and Biotechnology
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• v.28 no.1
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• pp.115-121
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• 2018

Upon sensing of microbial infections or endogenous danger signals in macrophages, inflammasome signaling plays a significant role in triggering inflammatory responses via producing interleukin (IL)-$1{\beta}$. Recent studies revealed that active caspase-1, a product of the inflammasome complex, causes maturation of inactive pro-IL-$1{\beta}$ into the active form. However, the underlying mechanism by which this leaderless cytokine is secreted into the extracellular space remains to be elucidated. In this study, we demonstrated that prolonged lipopolysaccharide (LPS) treatment to macrophages could trigger the unexpected maturation and extracellular release of IL-$1{\beta}$ through a nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 (NLRP3)-independent manner. Short-term treatment (less than 6 h) of LPS induced robust production of the IL-$1{\beta}$ precursor form inside cells but did not promote the maturation and secretion of IL-$1{\beta}$ in bone marrow-derived macrophages or peritoneal macrophages. Instead, prolonged LPS treatment (more than 12 h) led to a significant release of matured IL-$1{\beta}$ with no robust indication of caspase-1 activation. Intriguingly, this LPS-triggered secretion of IL-$1{\beta}$ was also observed in NLRP3-deficient macrophages. In addition, this unexpected IL-$1{\beta}$ release was only partially impaired by a caspase-1 and NLRP3 inflammasome inhibitor. Collectively, our results propose that prolonged exposure to LPS is able to drive the maturation and secretion of IL-$1{\beta}$ in an NLRP3 inflammasome-independent manner.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.483-490
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• 1999

In this paper, the cost-effective design of output reactor which is USCD to suppress the over-voltage at the m motor terminal in the Adjustable Speed Drives(ASD) application is proposed. In the elevator drive svstem. the R IXlwer cable length is relatively shorter than other ASD applications and then the over voltage at the motor terminal depends on the frequency characteristics of the output reactor at the over voltage operating frequency. The over-voltage suppression mechanism of output reactor in ASD application is analyzed and the dominant parameters of output reactor for the over-voltage supression are extracted. Using these as the design values and considering the high frequency characteristics of iron core in the reactor. a new c cost-effective structure of output reactor is proposed. Experimental results of the conventional reactor and the p proposed reactor with a l5kW induction motor are given to verify the propoSLD scheme.

• Journal of Biosystems Engineering
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• v.34 no.5
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• pp.315-324
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• 2009

Various types of vibration are transmitted to operators of agricultural tractors while working in the field. Most harmful vibration to human body is ride vibrations with low frequency ranging from 1 to 10 Hz, caused by rough terrain. These ride vibration has vertical and rotational components. This study was conducted to develop an active seat suspension system with two degrees of freedoms, enabling effectively reduce vibrations in vertical and pitch motions. Therefore, a mechanism for the active seat suspension was developed, and an electro-hydraulic servo system and a controller to drive the active seat suspension system were also developed in this study. A simulation model was developed to evaluate how the active seat suspension system effectively reduce the vibrations transmitted to the base of seat. Active seat suspension was optimized to enhance the performance using the developed simulation model. The performance of the seat suspension system was evaluated according to the test codes described in EEC78/764 in order to investigate the feasibility of application to agricultural tractors. The result showed that the developed active seat suspension system could reduce the magnitude of vertical vibration up to 80% for the input vibrations according to the test codes described in EEC78/764. The system could reduce the rotational displacement of ${\pm}\;2.5$ degrees up to 50% for the pitch vibration on the average in the frequency range of 1 to 2 Hz.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.12
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• pp.807-814
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• 2015

A control rod drive mechanism(CRDM) is a reactor regulating system, which inserts, withdraws or maintains a control rod containing a neutron absorbing material within a reactor core to control the reactivity of the core. The top-mounted CRDM for Jordan Research and Training Reactor(JRTR) with 5 MW power has been designed and fabricated based on the HANARO's experience through KAERI and DAEWOO consortium project. This paper describes the performance qualification test results to demonstrate the operability of a prototype and four production CRDMs during the reactor lifetime. The driving performance, the drop performance and the endurance tests for CRDM are carried out at a test rig simulating the actual reactor conditions. A vibration of internal components due to the coolant flow is also measured using a laser vibrometer. As a result, the CRDMs are driven having a good driving performance without a malfunction between command and output signals for the stepping motor. Also, the pure drop time and the impact acceleration are within 0.72 s and 4.2 g to meet the design requirements, and the vibrational displacement of control rod is measured as maximum $5.2{\mu}m$.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.166-173
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• 2006

In this study, a probe array has been developed for use in a data storage device that is based on scanning probe microscope (SPM) and MEMS technology. When recording data bits by poling the PZT thin layer and reading them by sensing its piezoresponse, commercial probes of which the tip heights are typically shorter than $3{\mu}m$ raise a problem due to the electrostatic forces occurring between the probe body and the bottom electrode of a medium. In order to reduce this undesirable effect, a poly-silicon probe with a high aspect-ratio tip was fabricated using a molding technique. Poly-silicon probes fabricated by the molding technique have several features. The tip can be protected during the subsequent fabrication processes and have a high aspect ratio. The tip radius can be as small as 15 nm because sharpening oxidation process is allowed. To drive the probe, electrostatic actuation mechanism was employed since the fabrication process and driving/sensing circuit is very simple. The natural frequency and DC sensitivity of a fabricated probe were measured to be 18.75 kHz and 16.7 nm/V, respectively. The step response characteristic was investigated as well. Overshoot behavior in the probe movement was hardly observed because of large squeeze film air damping forces. Therefore, the probe fabricated in this study is considered to be very useful in probe-based data storages since it can stably approach toward the medium and be more robust against external shock.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.11
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• pp.1848-1853
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• 2016

Control Rod Position Indicator in nuclear reactor vessel has developed for small reactor in Korea. Because of severe environment in reactor vessel, target of this study is to develop the suitable position indicator. In this study, solenoid type position indicator made of Mineral Insulated Cable(MI Cable) was introduced to adapt in severe environment. And inductance of the solenoid was used to indicate the rod position for high precision. But problem of this concept is that a linear slope of inductance is changed by temperature effect. To resolve this problem, two sensing coils were introduced for temperature compensation. A role of the sensing coil is to make reference linear equation about certain temperature. To confirm this concept, also, inductance of solenoid and sensing coils were measured at room and high temperature (${\sim}300^{\circ}C$). The results of measurement show that the position error of sensing coil between room and high temperature was about 2%. But it was identified that this error was resulted from insufficient test environment (temperature error between solenoid and sensing coils was about 2% at high temperature condition). Therefore, solenoid type position indicator shows that it is very suitable in reactor vessel as a high precision rod position indicator.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.463-468
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• 2017

For transdermal drug delivery, needless injection system is composed of laser and microjet injector. Main mechanism of microjet injector is the laser-induced bubble. Nd:YAG and Er:YAG laser are used as a power source. Laser parameters such as pulse duration and wavelength are considered, which are core parameters to control the bubble motion. The Nd:YAG laser, pulse duration is short than bubble life time making cavitation like bubble while in Er:YAG laser, long pulse duration and high absorption in water drive bubble as a boiling bubble. Detailed motion of bubble and microjet is captured by the high speed camera. So it is observed that microjet characteristics are determined by the bubble behavior. The performance of drug delivery system is evaluated by fluorescent staining of guinea pig skin.