• Journal of Institute of Control, Robotics and Systems
• /
• v.8 no.2
• /
• pp.89-96
• /
• 2002

A new chattering free PD-sliding mode hybrid control scheme is proposed for robot manipulators. This hybrid controller is composed of a PD controller and a semi-continuous sliding mode controller. It has a good robust performance in reaching mode which does not possess invariance property of sliding mode, and has chattering free characteristics in sliding mode. Thus, the PD-sliding mode hybrid controller has a good robust performance in the whole region. It is shown that the proposed control has a good transient response and trajectory tracking performance for a 2-link SCARA robot manipulator.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.194.2-194.2
• /
• 2012

Korea Aerospace Research Institute has developed an earth observation satellite and it was launched into its orbit in 2012 by using a foreign commercial launch vehicle. The launch site authority has imposed safety requirements to the spacecraft developer to ensure the safety of the personnel and to protect launch vehicle, spacecraft and facilities from accidents associated with the satellite operation at the launch site. This paper describes the range safety activities implemented for the satellite and supporting equipments during the whole phase of their design, manufacturing/test and operation at the launch site. To ensure the integrated requirements for safety management and design, system safety program plan has been developed. And based upon the plan, spacecraft developer conducted hazard analysis to identify and establish safety requirements to reflect in designs, procedures, operations. The result of the hazard analysis has been complied into safety data packages and it was reviewed by launch site review board at the safety reviews and finally it was approved to launch.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.2
• /
• pp.379-389
• /
• 2014

Low frequency oscillations (LFOs) are load angle oscillations that have a frequency between 0.1-2.0 Hz. Power system stabilizers (PSSs) are very effective controllers in improvement of the damping of LFOs. PSSs are designed by linearized models of the power system. This paper presents a new model of the power system that has the advantages of the Single Machine Infinite Bus (SMIB) system and the multi machine power system. This model is named a single machine normal-bus (SMNB). The equations that describe the proposed model have been linearized and a lead PSS has been designed. Then, particle swarm optimization technique (PSO) is employed to search for optimum PSS parameters. To analysis performance of PSS that has been designed based on the proposed model, a few tests have been implemented. The results show that designed PSS has an excellent capability in enhancing extremely the dynamic stability of power systems and also maintain coordination between PSSs.

• Steel and Composite Structures
• /
• v.30 no.2
• /
• pp.141-147
• /
• 2019

Fire is one of the environmental parameters affecting the structure causing element internal forces to change, as well as reducing the strength of the materials. One of the common types of floors in tall steel structures is the steel concrete composite slab. Shear connectors are used in steel and concrete composite beam in various shapes also has played significant role in a burning fire event of building with a steel concrete composite beam. The current study has reviewed the effects of temperature raising on the angle connector behavior through the use of push out tests and monotonic static force. The results have shown (1) the ductility of the samples is acceptable based on EC4 standard; (2) temperature raising has reduced the stiffness; (3) the shear ductility increment; and (4) the shear capacity reduction. Also, the amount of angle shear connector resistance has been decreased from 18.5% to 41% at ambient temperature up to $850^{\circ}C$.

• Animal Systematics, Evolution and Diversity
• /
• v.38 no.2
• /
• pp.83-90
• /
• 2022

Ovigerous crab of Sphaerozius nitidus of the family Menippidae was collected from Geojedo, Gyeongsangnamdo and hatched in the laboratory. Digital imaging of live zoeas of the first zoea stage of S. nitidus has been reported for the first time in the world, and its morphology has been redescribed and illustrated. This study is different from former study in that it has three unequal setae with exopod of antenna, 5+4 setae with basial endite of maxilla, and dorsomedial spine and lateral minute spine with fork of telson. The first zoea of S. nitidus has black pigments occurring behind the eyes, on the dorsal spine medially and on the basis of lateral carapace spines, on basal of basis of maxillipeds 1, 2, and posterior margins of somites 1-5, and yellowish green chromatophores on the dorsal spine.

• Journal of Smart Tourism
• /
• v.3 no.2
• /
• pp.5-13
• /
• 2023

Because of increasing anxiety about infectious diseases and the demand for contactless service caused by the COVID-19 pandemic, it has become crucial for the tourism and hospitality sector to understand customers' psychological mechanism of contactless service during and post COVID-19. Thus, this paper proposes a conceptual model by integrating trust in the framework of the behavioral immune system. Interestingly, our study found that anxiety about infectious diseases during the COVID-19 pandemic has not only increased hotel customers' desire for contactless service and changed their behavioral intentions, but it has also impacted customers' trust in hotel service robots. Therefore, irrespective of how the hotel service environment changes, trust in technology has become the most fundamental factor for hotel customers' attitudes toward adopting technology. Based on the results, this paper provides salient theoretical and practical implications.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.10
• /
• pp.1485-1490
• /
• 2014

$SF_6$ gas has been used for power transformers or gas insulated switchgears, because it has the superior insulation property and the stable structure chemically. It has been, however, one of global warming gases and required to reduce the its amount. Some papers have reported that its amount could be reduced by mixing with other gases, such as $N_2$, $CF_4$, $CO_2$ and $C_4F_8$ and their mixture gases would cause the synergy effect. In this paper, we investigated the characteristics of DC plasmas on $SF_6$ mixture gases with $N_2$ at atmospheric pressure. $N_2$ gas is one of cheap gases and has been reported to show the synergy effect with mixing $SF_6$ gas, even though $N_2$ plasmas have electron-positive characteristics. 38 kinds of $SF_6/N_2$ plasma particles, which consisted of an electron, two positive ions, five negative ions, 30 excitation and vibration particles, were considered in a one dimensional fluid simulation model with capacitively coupled plasma chamber. The results showed that the joule heating of $SF_6/N_2$ plasmas was mainly caused by positive ions, on the other hand electrons acted on holding the $SF_6/N_2$ plasmas stably. The joule heating was strongly generated near the electrodes, which caused the increase of neutral gas temperature within the chamber. The more $N_2$ mixed-ratio increased, the less joule heating was. And the power consumptions by electron and positive ions increased with the increase of $N_2$ mixed-ratio.

• The KIPS Transactions:PartA
• /
• v.15A no.6
• /
• pp.301-308
• /
• 2008

The crossed cube has received great attention because it has equal or superior properties to the hypercube that is widely known as a versatile parallel processing system. It has been known that a mesh of size $2{\times}2^m$ can be embedded into a crossed cube with dilation 1 and expansion 1 and a mesh of size $4{\times}2^m$ with dilation 1 and expansion 2. However, as we know, it has been a conjecture that a mesh with more than eight rows and columns can be embedded into a crossed cube with dilation 1. In this paper, we show that a mesh of size $2^n{\times}2^m$ can be embedded into a crossed cube with dilation 1 and expansion $2^{n-1}$ where $n{\geq}1$ and $m{\geq}3$.

• Bulletin of the Korean Chemical Society
• /
• v.21 no.10
• /
• pp.969-972
• /
• 2000

[Fe II Fe III $BPLNP(OAc)_2](BPh_4)_2$ (1), a new model for the reduced form of the purple acid phosphatases, has been synthesized by using a dinucleating ligand, 2,6-bis[((2-pyridylmethyl)(6-methyl-2-pyridylmethyl)ami-no)methyl]-4-nitrophenol (HBPLNP) . Complex 1 has been studied by electronic spectral, NMR, EPR, SQUID, and electrochemical methods. Complex 1 exhibits two strong bands at 498 nm $(\varepsilon=$ 2.6 ${\times}10^3M-^1cm-^1)$ and 1363 nm $(\varepsilon=$ 5.7 ${\times}10^2M-^1cm-^1)$ in $CH_3CN.$ These are assigned to phenolate-to-FeIII and intervalence charge-transfer transitions, respectively. NMR spectrum of complex 1 exhibits sharp isotropically shifted resonances, which number is half of those expected for a valence-trapped species, indicating that electron transfer between FeⅡ and FeⅢ centers is faster than NMR time scale at room temperature. Complex 1 undergoes quasireversible one-electron redox processes. The $FeIII_2/FeIIFeIII$ and $FeIIFeIII/FeII_2$ redox couples are at 0.807 and 0.167 V ver-sus SCE, respectively. It has Kcomp = 5.9 ${\times}$10 1s(acetato) ligand combination sta-bilizes a mixed-valence FeIIFeIII complex in the air. Interestingly, complex 1 exhibits intense EPR signals at g = 8.56, 5.45, 4.30 corresponding to mononuclear high-spin FeⅢ species, which suggest a very weak magnetic coupling between the iron centers. Magnetic susceptibility study shows that there is a very weak antiferromag-netic coupling (J = $-0.78cm-^1$, H = $-2JS_1${\times}$S_2)$ between FeII and FeIII centers. Thus, we can suggest that complex 1 has a very weak antiferromagnetic coupling between the iron centers due to the electronic effect of the nitro group in the bridging phenolate ligand.

• Food Science and Industry
• /
• v.50 no.2
• /
• pp.12-26
• /
• 2017

Processing steps such as washing and cutting, involved in preparing fresh-cut produce causes tissue damage, leading to rapid quality deterioration. Major defects of fresh-cut produce are discoloration, softening, off-odor development, and microbial growth. Packaging of fresh-cut produce has been changed to reduce these quality problems. Flexible packaging film is widely used to pack fresh-cut produce. Vacuum packaging was the popular packaging method in the beginning of fresh-cut industry in Korea. Vacuum packaging creates high $CO_2$ and low $O_2$ levels to control browning of fresh-cut produce. However, these conditions induce some visual defects and off-odor development. Discoloration problem was also found when fresh-cut produce was packaged with conventional packaging film or plastic tray. Modified atmosphere (MA) packaging is effective for prolonging shelf-life of fresh-cut produce by decreasing $O_2$ and increasing $CO_2$ concentration in the package. Retail MA packaging using different oxygen transmission rate (OTR) film and micro-perforated film has started to be applied to fresh-cut produce in Korea. Proper MA package design that provides optimum range of $O_2$ and $CO_2$ partial pressures is one of the major challenges in the industry. An initial package flushing with $N_2$ or an low $O_2$/high $CO_2$ atmosphere is also used to more rapidly establish steady-state MA condition. Film OTR and $O_2$ flushing affects the fermentative volatile production, off-odor development, electrolyte leakage, discoloration, $CO_2$ injury, microbial population of fresh-cut produce. There is also a demand for convenient packaging to attract consumers. Rigid fresh-cut produce container for retail market has increased since the packaging provides excellent protection from physical damage during transport. Rigid tray used as actual serving vessel for the consumer is increasing in Korea. The tray with flexible lid to wrap or seal fresh-cut produce is more and more gaining popularity. Further practical technology to control quality change and microbial growth for each fresh-cut product has been studied since various fresh-cut items were required. The fresh-cut industry also focuses on searching for more convenient and environmentally friendly packaging.