• Journal of Power Electronics
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• v.17 no.3
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• pp.704-715
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• 2017

For three-phase synchronization applications, the synchronous reference frame phase-locked loop (SRF-PLL) is probably the most widely used technique due to its ease of implementation and satisfactory phase tracking performance under ideal grid conditions. However, under unbalanced and distorted grid conditions, its performance tends to worsen. To deal with this problem, a variety of filtering stages have been proposed and used in SRF-PLLs for the rejection of disturbance components at the cost of degrading the dynamic performance. In this paper, to improve dynamic performance without compromising the filtering capability, an effective hybrid filtering stage is proposed and incorporated into the inner loop of a quasi-type-1 PLL (QT1-PLL). The proposed filtering stage is a combination of a moving average filter (MAF) and a modified delay signal cancellation (DSC) operator in cascade. The time delay caused by the proposed filtering stage is smaller than that in the conventional MAF-based and DSC-based PLLs. A small-signal model of the proposed PLL is derived. The stability is analyzed and parameters design guidelines are given. The effectiveness of the proposed PLL is confirmed through experimental results.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1480-1482
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• 2005

The major causes of power quality deterioration are harmonic current through semiconductor switching device, due to use of nonlinear loads such as diodes rectifier or thyristor rectifiers. In response to this concerns, this paper presents a new control method of single-phase active power filter(APF) for the compensation of harmonic current components in nonlinear loads. In order to make the complex calculation to be possible, the single-phase system that has two phases was made by constructing a imaginary second-phase giving time delay to load currents. In the conventional method, a imaginary-phase lagged to the load current T/4(here T is the fundamental cycle) was made. But in this proposed method, the new signal, which has the delayed phase through the filter, using the phase-delay property of low-pass filter, was used as the second phase. As this control method is applied to the system of single phase, an instantaneous calculation was done rather by using the rotating reference frames that synchronizes with source-frequency than by applying instantaneous reactive power theory that uses the conventional fixed reference frames.

• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1127-1134
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• 2002

The effects of pressure and temperature on the autoignition of propane and n-butane blends were investigated using a rapid compression machine (RCM) , which is widely used to examine the autoignition characteristics. The RCM was designed to be capable of varying the compression ratio between 5 and 20 and minimize the vortex formation on the cylinder wall using a wedge-shaped crevice. The initial temperature and pressure of the compressed gas were varied in range of 720∼900 K and 1.6∼ 1.8 MPa, respectively, by adjusting the ratio of the specific heat of the mixture by altering the ratio of the non-reactive components (N$_2$, Ar) under a constant effective equivalence ratio (ø$\_$f/= 1.0) The gas temperature after the compression stroke could be obtained from the measured time-pressure record. The results showed a two-stage ignition delay and a Negative Temperature Coefficient (NTC) behavior which were the unique characteristic of the alkane series fuels. As the propane concentration in the blend were increased from 20% and 40% propane, the autoignition delay time increased by approximately 41 % and 55% at 750 K. Numerical reduced kinetic modeling was performed using the Shell model, which introduced some important chemical ideas, represented by the generic species. Several rate coefficients were calibrated based on the experimental results to establish an autoignition model of the propane and n-butane blends. These coefficients can be used to predict the autoignition characteristics in LPG fueled Sl engines.

• Journal of the Korean Institute of Gas
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• v.7 no.3 s.20
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• pp.32-43
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• 2003

As this paper is observed the phase equilibrium diagram of mono- (methane) and multi-component(natural gas) hydrates, and the hydrate growth behavior is analysed and compared by the experiments during the reaction. The difference of mono and multi-component hydrates is an induction delay time and a plateau region. And the concentration of component of gases is changed during the reaction in multi-component hydrates and the concentration of components is changed during the decomposition of hydrate according to each decomposing rates of gases. At 6 MPa, 276.65 K and 600 rpm, the induction delay time of multi-component hydrate formation is observed shorter than that of mono-component hydrate formation because the hydrate nuclei of gases except methane form faster than those of methane. And the plateau region of mono-component hydrate is observed distinctly at 0.055 mole of $CH_4$/mole of water and that of multi-component hydrate is observed at 0.04 mole of $CH_4$/mole of water.

• Journal of IKEEE
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• v.12 no.1
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• pp.1-7
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• 2008

With the recent development of portable system such as mobile communication and multimedia. Full adders are important components in applications such as digital signal processors and microprocessors. Thus It is important to improve the power dissipation and operating speed for designing a full adder. We propose a new adder with modified version of conventional Ratioed logic and Pass Transistor logic. The proposed adder has the advantages over the conventional CMOS, TGA, 14T logic. The delay time is improved by 13% comparing to the average value and PDP(Power Delay Product) is improved by 9% comparing to the average value. Layouts have been carried out using a 0.18um CMOS design rule for evaluation purposes. The physical design has been evaluated using HSPICE.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.518-525
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• 2016

This paper presents the characteristics of non-fundamental multi-mode combustion instability and the effects of high-harmonic components on the Rayleigh criterion. Phenomenological observations of multi-harmonic-mode dynamic pressure waves regarding the intensity of harmonic components and the source of wave distortion have been explained by introducing examples of second- and third-order harmonics at various amplitudes. The amplitude and order of the harmonic components distorted the wave shapes, including the peak and the amplitude, of the dynamic pressure and heat release, and consequently the temporal Rayleigh index and its integrals. A cause-and-effect analysis was used to identify the root causes of the phase delay and the amplification of the Rayleigh index. From this analysis, the skewness of the dynamic pressure turned out to be a major source in determining whether multi-mode instability is driving or damping, as well as in optimizing the combustor design, such as the mixing length and the combustor length, to avoid unstable regions. The results can be used to minimize errors in predicting combustion instability in cases of high multi-mode combustion instability. In the future, the amount of research and the number of applications will increase because new fuels, such as fast-burning syngases, are prone to generating multi-mode instabilities.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1029-1039
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• 2013

To avoid undesirable disconnection of healthy wind generators (WGs) or a wind power plant, a WG protection relay should discriminate among faults, so that it can operate instantaneously for WG, connected feeder or connection bus faults, it can operate after a delay for inter-tie or grid faults, and it can avoid operating for parallel WG or adjacent feeder faults. A WG protection relay based on the positive- and negative-sequence fault components is proposed in the paper. At stage 1, the proposed relay uses the magnitude of the positive-sequence component in the fault current to distinguish faults requiring non-operation response from those requiring instantaneous or delayed operation responses. At stage 2, the fault type is first determined using the relationships between the positive- and negative-sequence fault components. Then, the relay differentiates between instantaneous operation and delayed operation based on the magnitude of the positive-sequence fault component. Various fault scenarios involving changes in position and type of fault and faulted phases are used to verify the performance of the relay. This paper concludes by implementing the relay on a hardware platform based on a digital signal processor. Results indicate that the relay can successfully distinguish the need for instantaneous, delayed, or non-operation.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.1
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• pp.13-18
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• 2000

Low temperature co-fired ceramics on metal (LTCC-M) is efficient for embedding passive components with good tolerance in a module due to the dimensional stability in x and y directions by the constraint of metal core during the firing. In addition, the radiation noise can be reduced by metal core. In this paper, embedded passive components were introduced and a power amplifier module (PAM) fabricated by using the passive components was explained. The embedded passive components in test patters showed the tolerance of 10~20% and the good repeatability in tolerance of embedded passives was maintained in module fabrication. The shortened traces in multi chip modules (MCMs) make the signal delay time decreased and the embedded passives simplify the packaging processes owing to the less solder points, which enhance the electrical performance and increase the reliability of the modules. The LTCC-M technology is one of the promising candidates for RF application and is expected to expand its applications to power and high performance devices.

• Journal of Life Science
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• v.19 no.1
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• pp.138-146
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• 2009

Garlic (Allium sativum) are an agronomically important genus because of their sulfur flavour components. The majority of the volatiles flavour principles are generated through the enzymatic hydrolysis of the non-volatile organosulfur compounds. However, these compounds may be possible sources of new novel bioacuve and therapeutic principles. Garlic has strong antioxidant activity, and epidemiological studies support the fad that diets rich of garlic may prevent some of the chronic diseases. The health cares of garlic likely arise from a wide variety of components, which may work synergistically. The chemical changes of garlic composition makes it plausible that a variation in processing can lead to acquisition of differential chemical compositions of garlic products. Especially highly unstable allicin can easily disappear during processing and are quickly transformed into a various organosulfur compounds. Various supplements of garlic, particularly aged garlic extract (AGE), are known to possess a promising antioxidant potential and are effective in prevention of chronic diseases because of the bioactive constituents. Although all of active ingredients of AGE are not elucidated, water-soluble components of AGE, including S-allylcysteine, S-allylmercaptane, steroid saponins, tetrahydro-${\beta}$-carboline derivatives, and fructosyl-arginine, appears to be associated with the pharmacological effects of AGE. Consequently, the allicin free garlic components such as S-allylcysteine, S-allylmercaptane, steroid saponins, tetrahydro-${\beta}$-carboline derivatives, and fructosyl-arginine can be applicable to standardization of the quality of commercial garlic products. This review provides an insight into garlic's biomarkers and presents evidence that they may either prevent or delay chronic disease associated with aging.

• Plant Breeding and Biotechnology
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• v.5 no.3
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• pp.237-242
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• 2017

AT-hook proteins of plant have shown to be involved in growth and development through the modification of chromatin architecture to co-regulate transcription of genes. Recently, many genes encoding AT-hook protein have been identified and their involvement in senescence delay is investigated. In this study, soybean transgenic plants overexpressing chromatin architecture-controlling ATPG7 gene was produced by Agrobacterium-mediated transformation and investigated for the positive effect on the important agronomic traits mainly focusing on yield-related components. A total of 27 transgenic soybean plants were produced from about 400 explants. $T_1$ seeds were harvested from all transgenic plants. In the analysis of genomic DNAs from soybean transformants, ATPG7 and Bar fragments were amplified as expected, 975 bp and 408 bp in size, respectively. And also exact gene expression was confirmed by reverse transcriptase-PCR (RT-PCR) from transgenic line #6, #7 and #8. In a field evaluation of yield components of ATPG7 transgenic plants ($T_3$), higher plant height, more of pod number and greater average total seed weight were observed with statistical significance. The results of this study indicate that the introduction of ATPG7 gene in soybean may have the positive effect on yield components.