• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.134-141
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• 2010

Small PEM (Proton Exchange Membrane) fuel cell systems do not require humidification and have great commercialization possibilities. However, methods for controlling small PEM fuel cell stacks have not been clearly established. In this paper, a control method for small PEM fuel cell systems using a dual closed loop with a static feedforward structure is defined and realized using a DSP (Digital Signal Processor). The fundamental elements that need to be controlled in fuel cell systems include the supply of air and hydrogen, water management inside the stack, and heat management of the stack. For small PEM fuel cell stacks operated without a separate humidifier, fans are essential for air supply, heat management, and water management of the stack. A purge valve discharges surplus water from the stack. The proposed method controls the fan using double control loops to quicken transient response of the fan thereby improving the supply rate of air. Feedback control to compensate for the voltage change in fuel cell stack improves the response characteristics in fuel cell to load variations. The feasibility of proposed method was proved by the experiments with a 60W small PEM fuel cell system and operation of a notebook computer using this system.

• Smart Structures and Systems
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• v.13 no.2
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• pp.219-233
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• 2014

In a companion paper, Pasala and Nagarajaiah analytically and experimentally validate the Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) on a primary structure (2 story steel structure) whose frequencies are time invariant (Pasala and Nagarajaiah 2012). In this paper, the ALP-STMD effectiveness on a primary structure whose frequencies are time varying is studied experimentally. This study experimentally validates the ability of an ALP-STMD to adequately control a structural system in the presence of real time changes in primary stiffness that are detected by a real time observer based system identification. The experiments implement the newly developed Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) which was first introduced and developed by Nagarajaiah (2009), Nagarajaiah and Pasala (2010) and Nagarajaiah et al. (2010). The ALP-STMD employs a mass pendulum of variable length which can be tuned in real time to the parameters of the system using sensor feedback. The tuning action is made possible by applying a current to a shape memory alloy wire changing the effective length that supports the damper mass assembly in real time. Once a stiffness change in the structural system is detected by an open loop observer, the ALP-STMD is re-tuned to the modified system parameters which successfully reduce the response of the primary system. Significant performance improvement is illustrated for the stiffness modified system, which undergoes the re-tuning adaptation, when compared to the stiffness modified system without adaptive re-tuning.

• Korean System Dynamics Review
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• v.10 no.2
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• pp.103-120
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• 2009

Using various data derived from the regional innovation projects in the IT and BT-sectors within Chungbuk Province, this study tries to observe formation processes of network connecting structure and their spill-over effects. Considering the dynamic nature of key issues, it applies both social network analysis and causal loop methods. After a series of simulation exercises, we find that so-called extroverted regional innovation projects, that is, ones financially supported by the central government, reveal a higher tendency in the centrality, heavily depending on a handful of well reputed organizations. It is quite similar to the reinforcing mechanism, resulting in the rich-get-richer and the poor-get-poorer. Compared with the existing documents, nonetheless, it shows relatively weak in the mechanism strength, implying the fact that regional innovation projects have significantly contributed to ameliorating the unequal distribution of innovation organizations within Chungbuk Province. On the other hand, this study concludes that all the brokerage organizations related to the regional innovation projects have settled in Chungbuk Province. Whereas the Capital Region-based organizations present a higher tendency in the knowledge-network, it seems that the regional innovation projects have significantly contributed to upgrading direct and indirect competitiveness of the local organizations.

• Asian-Australasian Journal of Animal Sciences
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• v.24 no.2
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• pp.173-180
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• 2011

Osteocalcin (OC), a marker of bone turnover, displays patterns in relation to physiological and genetic factors. Here, we present an association study in a population of Chinese Holstein cattle (n = 24) with OC serum concentration as a phenotypic trait. We hypothesised that OC status is associated with phylogeny, vitamin D serum level and single nucleotide polymorphisms (SNPs). Mitochondrial DNA (mtDNA) was used as an unlinked marker to examine phylogeny and linkage to measured phenotypic traits of vitamin D and OC status. Following an association study with OC serum variability as the trait, genotyping of SNPs (n = 27) in OC-related genes was performed. Candidate SNPs were chosen in genes with an emphasis on the vitamin D and vitamin K pathways. Multivariant factor analysis revealed a correlation between vitamin D serum concentration and a SNP in the gene GC (rs43338565), which encodes a vitamin D-binding protein, as well as between a SNP in NFATc1 (rs42038422) and OC concentration. However, univariate analysis revealed that population structure, vitamin D serum levels and SNPs were not significant determinants of OC status in the studied group.

• Fibers and Polymers
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• v.7 no.3
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• pp.295-304
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• 2006

High-bulk worsted yams with different shrinkable and non-shrinkable acrylic fibers blend ratios are produced and then single jersey weft knitted fabrics with three different structures and loop lengths are constructed. The physical properties of produced yams and compression properties of produced fabrics at eight pressure values (50, 100, 200, 500, 1000, 1500 and $2000 g/cm^2$) were measured using a conventional fabric thickness tester. Then, weft-knitted fabric compression behavior was analyzed using a two parameters model. It is found that at 40 % shrinkable fibre blending ratio the maximum yam bulk, shrinkage, abrasion resistance and minimum yarn strength are obtained. It is also shown that high-bulk acrylic yarn has the highest elongation at 20 % shrinkable fibre blend ratio. The statistical regression analysis revealed that the compression behavior of acrylic weft-knitted fabrics is highly closed to two parameter model proposed for woven fabrics. It is also shown that for weft-knitted structure, there is an incompressible layer (V') which resists against high compression load. Acrylic weft-knitted fabrics with knit-tuck structure exhibit higher compression rigidity and lower softness than the plain and knit-miss structures. In addition, at 20 % shrinkable fibre blend ratio, the high-bulk acrylic weft-knitted fabrics are highly compressible.

• Korean Journal of Materials Research
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• v.25 no.8
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• pp.376-385
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• 2015

The effects of Nb and Cr addition on the microstructure, corrosion and oxide characteristics of Zr based alloys were investigated. The corrosion tests were performed in a pressurized water reactor simulated-loop system at $360^{\circ}C$. The microstructures were examined using OM and TEM, and the oxide properties were characterized by low-angle X-ray diffraction and TEM. The corrosion test results up to 360 days revealed that the corrosion rates were considerably affected by Cr content but not Nb content. The corrosion resistance of the Zr-xNb-0.1Sn-yCr quaternary alloys was improved by an increasing Nb/Cr ratio. The crystal structure of the precipitates was affected by a variation of the Nb/Cr ratio. The Zr-Nb beta-enriched precipitates were mainly formed in the high Nb/Cr ratio alloy while $Zr(NbCr)_2$ precipitates were frequently observed in the low Nb/Cr ratio alloy. The studies of oxide characteristics revealed that the corrosion resistance was related to the crystal structure of the precipitate.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.359-369
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• 2020

In this paper, we proposed a charge pump (CP) circuit that has a wide operating range while reducing the current mismatch for the PLL that generates the main clock of the CMOS X-Ray detector. The operating range and current mismatch of the CP circuit are determined by the characteristics of the current source circuit for the CP circuit. The proposed CP circuit is implemented with a wide operating current mirror bias circuit to secure a wide operating range and a cascode structure with a large output resistance to reduce current mismatch. The proposed wide operating range cascode CP circuit was fabricated as a chip using a 350nm CMOS process, and current matching characteristics were measured using a source measurement unit. At this time, the power supply voltage was 3.3 V and the CP circuit current ICP = 100 ㎂. The operating range of the proposed CP circuit is △VO_Swing=2.7V, and the maximum current mismatch is 5.15 % and the maximum current deviation is 2.64 %. The proposed CP circuit has low current mismatch characteristics and can cope with a wide frequency range, so it can be applied to systems requiring various clock speed.

• Korean Journal of Microbiology
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• v.32 no.3
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• pp.177-181
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• 1994

The sequences of the cytoplasmic 5S rRNAs(EMBL accession number X73589 and X73890) from two polupores, Ganoderma applanatum and Schizopora paradoxa, were determined by the direct chemical method for sequencing RNA and compared to the sequences of 9 reported mushrooms. 5S rRNAs of Ganoderma applanatum and Schizopora paradoxa consisted of 118 bases and fit the secondary structure model of the 5S rRNAs of basidiomycetes proposed by Huysmans et al. Based on Kimura’s K_nuc values, the closest fungus to Ganoderma applanatum was Ceratobasidium cornigerum and the one to Schizopora paradoxa was Bjerkandera adusta. When the secondary structures of 5S rRNAs of 11 mushrooms were compared the base substitution occurred at helix regions more than at loop regions. When a phylogenetic tree was constructed using the Neighbor program of the PHYLIP package, it partially discriminated and separated the mushrooms of the Hymenomycetes by the order.

• Toxicological Research
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• v.26 no.3
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• pp.171-175
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• 2010

The human genome contains approximately 13 orphan cytochrome P450 (P450, CYP) genes, of which the apparent function or substrate has not been identified. However, they seem to possess their own biological relevance in some tissues or developmental stages. Here, we characterized the heterologously expressed CYP2W1, an orphan P450 enzyme. The recombinant CYP2W1 protein containing a $6{\times}$(His)-tag at Nterminus has been expressed in Escherichia coli and purified. Expression level of CYP2W1 holoenzyme was around 500 nmol P450 holoenzyme per liter culture medium. The reduced CO difference spectrum of CYP2W1 showed a maximum absorption at 449 nm. CYP2W1 indicated the significant induction to bioactivate Trp-P-1, MeIQ, and IQ in E. coli DJ701 tester strain. However, the bioactivation of B[$\alpha$]P, and NNK by CYP2W1 was relatively low. The model structure of CYP2W1 suggested the characteristic P450 folds with the lengths and orientations of the individual secondary elements. The F-G loop is situated on the distal side of heme to accommodate the flexibility of active site of CYP2W1. These studies can provide useful information for the finding of its biological roles and structure-function relationships of an orphan CYP2W1 enzyme.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.2
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• pp.189-195
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• 2005

This paper presents a new velocity estimation strategy for a non-salient permanent magnet synchronous motor drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system, which contains the rotor position error information. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error at zero. For zero and low speed operation, the PI gain of the rotor position tracking controller has a variable structure according to the estimated rotor velocity. Then, at zero speed, the rotor position and velocity have sluggish dynamics because the varying gains are very low in this region. In order to boost the bandwidth of the PI controller during zero speed, the loop recovery technique is applied to the control system. The PI tuning formulas are also derived by analyzing this control system by frequency domain specifications such as phase margin and bandwidth assignment.