• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.481-484
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• 2006

Pitch period detection algorithms are applied to various speech signal processing fields such as speech recognition, speaker identification, speech analysis and synthesis. Furthermore, many pitch detection algorithms of time and frequency domain have been studied until now. AMDF(average magnitude difference function) ,which is one of pitch period detection algorithms, chooses a time interval from the valley point to the valley point as the pitch period. AMDF has a fast computation capacity, but in selection of valley point to detect pitch period, complexity of the algorithm is increased. In order to apply pitch period detection algorithms to the real world, they have robust prosperities against generated noise in the subway environment etc. In this paper we proposed the modified AMDF algorithm which detects the global minimum valley point as the pitch period of speech signals and used speech signals of noisy environments as test signals.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.672-678
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• 2019

The electrochemical properties of pitch-coated natural graphite(NG) were investigated as an anode for lithium-ion batteries. The anode materials were prepared by heat-treatment of mixture of NG and petroleum pitch at $1000^{\circ}C$. The pitches with various softening points were used as carbon precursor. The physical properties of anode materials were analyzed by TGA, SEM, PSA and BET. As the softening point increased, the thickness of the coating layer increased and the specific surface area decreased. The electrochemical performances were investigated by initial charge/discharge efficiency, cycle stability, cyclic voltammetry, rate performance and electrochemical impedance spectroscopy. The carbon-coated NG using pitch with softening points of $250^{\circ}C$ showed an initial discharge capacity of 361 mAh/g and a coulombic efficiency of 92.6%. Also, the rate performance(5 C/0.2 C) was 1.6 times higher than that of NG, and it had a capacity retention (90%) after 50 cycles at 0.5 C.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.6
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• pp.21-26
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• 2020

In this paper, we investigated the characteristics of SF-MPAA depend on the structures of radiators when they were embroidered for realizing embroidered SF-MPAA. As increasing pitches by decreasing numbers of grids in length-direction and width-direction of the embroidered radiator the antenna gain and resonance frequency were trendingly decreased. However the characteristics of antenna were affected very much by the pitch in width-direction but affected relatively less by the pitch in length-direction. Therefore it was beneficial to decrease number of grids in length-direction to decrease conductor ratio. SLL was affected by the combination of length-direction pitch and width-direction pitch. The conductor ratio of embroidered radiator was determined by the ratio of pitch to embroidered thread thickness. When the ratio was less than 5 the conductor ratio was decreased rapidly. But when the ratio was larger than 5 the conductor ratio was decreased slowly and saturated.

• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.42-48
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• 2021

In this study, a sensor for detection of nitric oxide (NO) gas was developed using petroleum pitch-based activated carbon which was synthesized from pyrolysis fuel oil (PFO). Polyethylene terephthalate (PET) was added to increase molecular weight by stimulating a polymerization of components in PFO during the pitch synthesis process. The increase in the molecular weight of pitch contributed to the improvement of textural properties of activated carbon, such as the specific surface area and micropore volume. It also enhanced the sensitivity of NO gas sensor based on the activated carbon. In addition, the effect of PET addition during the pitch synthesis on the surface oxygen content and conductivity of activated carbon was investigated. Finally, the correlation of the sensitivity with physical properties of activated carbon was analyzed.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.63-71
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• 2023

In the present study, the effect of pitch amplitude on the unsteady aerodynamics of a NACA 0012 airfoil is numerically investigated. When the frequency ratio is equal to 1.0, airfoil pitching with 20 and 30 degrees of pitch amplitude shows almost small lift generation, but the lift is significantly increased in case of 10-degree pitch amplitude. When the frequency is 0.5, the lift coefficients have large values, and the lift increases with a decrease in pitch amplitude. When the frequency ratio is 1.0, the airfoil generates large thrust. The thrust decreases as the pitch amplitude decreases. When the frequency ratio is 0.5, drag is generated for the 30-degree pitch amplitude, but the thrust is generated for 10-degree pitch amplitude. In future, the effect of heave amplitude on the unsteady aerodynamics of the airfoil will be studied.

• The Journal of the Acoustical Society of Korea
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• v.23 no.6
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• pp.488-496
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• 2004

This paper describes a music information retrieval system which uses humming as the key for retrieval Humming is an easy way for the user to input a melody. However, there are several problems with humming that degrade the retrieval of information. One problem is a human factor. Sometimes people do not sing accurately, especially if they are inexperienced or unaccompanied. Another problem arises from signal processing. Therefore, a music information retrieval method should be sufficiently robust to surmount various humming errors and signal processing problems. A retrieval system has to extract pitch from the user's humming. However pitch extraction is not perfect. It often captures half or double pitches. even if the extraction algorithms take the continuity of the pitch into account. Considering these problems. we propose a system that takes multiple pitch candidates into account. In addition to the frequencies of the pitch candidates. the confidence measures obtained from their powers are taken into consideration as well. We also propose the use of an algorithm with three dimensions that is an extension of the conventional DP algorithm, so that multiple pitch candidates can be treated. Moreover in the proposed algorithm. DP paths are changed dynamically to take deltaPitches and IOIratios of input and reference notes into account in order to treat notes being split or unified. We carried out an evaluation experiment to compare the proposed system with a conventional system. From the experiment. the proposed method gave better retrieval performance than the conventional system.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.534-538
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• 2017

In this study, the molecular weight controlled pitches derived from pyrolyzed fuel oil (PFO) were prepared using solvent extraction and were carbonized. Electrochemical characteristics of lithium battery anode materials were investigated using these petroleum pitches. Three pitch samples prepared by the thermal reaction were 3903 (at $390^{\circ}C$ for 3 h), 4001 (at $400^{\circ}C$ for 1 h) and 4002 (at $400^{\circ}C$ for 2 h). The prepared hexane insoluble pitches were analysed by XRD, TGA, SEM and Gel permeation Chromatography (GPC). The electrochemical characteristics of the PFO-derived pitch as an anode material were investigated by constant current charge/discharge, cyclic voltammetry and electrochemical impedance tests. The coin cell using pitch (4001) and the electrolyte of $LiPF_6$ in organic solvents (EC : DMC = 1 : 1 vol%, VC 3 wt%) has better initial capacity (310 mAh/g) than that of other pitch coin cells. Also, this carbon anode showd a high initial efficiency of 82%, retention rate capability at 2 C/0.1 C of 90% and cycle retention of 85%. It was found that modified pitches improved the cycling and rate capacity performance.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.142-149
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• 2020

In this study, the electrochemical performance of Graphite/Silicon/Pitch composites as anode material was investigated to improve the low theoretical capacity of artificial graphite. Spherical artificial graphite surface was coated with polyvinylpyrrolidone (PVP) amphiphiles material to synthesize Graphite/Silica material by silica islands growth. The Graphite/Silicon/Pitch composites were prepared by petroleum pitch coating and magnesiothermic reduction. The Graphite/Silicon/Pitch composite electrodes manufactured using poly(vinylidene fluoride) (PVDF), carboxymethyl cellulose (CMC) and polyacrylic acid (PAA) binders. The coin type half cell was assembled using various electrolytes and additives. The Graphite/Silicon/Pitch composites were analysed by X-ray diffraction (XRD), scanning electron microscope (SEM) and a thermogravimetric analyzer (TGA). The electrochemical characteristics of Graphite/Silicon/Pitch composite were investigated by constant current charge/discharge, rate performance, cyclic voltammetry and electrochemical impedance spectroscopy. The Graphite/Silicon/Pitch composites showed high cycle stability at a graphite/silica/pitch ratio (1:4:8 wt%). When the electrode is prepared using PAA binder, the high capacity and stability is obtained. The coin type half cell assembled using EC: DMC: EMC electrolyte showed high initial capacity (719 mAh/g) and excellent cycle stability. The rate performance has an capacity retention (77%) at 2 C/0.1 C and an capacity recovery (88%) at 0.1 C / 0.1 C when the vinylene carbonate (VC) was added.

• Applied Chemistry for Engineering
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• v.30 no.3
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• pp.331-336
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• 2019

In this study, required properties and optimized procedure conditions for the pitch based soft carbon anode of lithium ion battery was investigated for improving the initial efficiency and rate performance. Each petroleum residue was thermally treated at 360, 370, and $410^{\circ}C$ for 3 hours to synthesis a pitch and the corresponding pitch shows the softening point of 86, 98, and $152^{\circ}C$, respectively. The elemental analysis and thermal characteristics of the pitch were investigated by EA analysis and TGA. It was noted that the low H/C and improved thermal stability were obtained with the high softening point. The obtained pitch was carbonized at $1,200^{\circ}C$ for 1 hour to produce a soft carbon based anode. As a result of investigating the crystal structure by XRD analysis, it was found that the crystallinity of soft carbon increased with increasing the softening point. It was considered that relatively higher boiling components and decreases in the evaporation component resulted the components participation for cyclization during the heat treatment process. The soft carbon based anode with an improved crystallinity shows the enhanced initial efficiency and rate performance. The mechanism of both improvements was also discusssed based on the developed crystal structure of soft carbon based anode materials.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.713-721
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• 2022

In order to use the LED video wall in the broadcasting studio, there are a few things to be aware of. First, since the pixels are closely arranged, a moire phenomenon may occur due to a short arrangement period, and second, the distance between pixels (pixel pitch) may be recorded on the image sensor of the broadcasting camera. When moire occurs or pixel pitch is observed, viewers feel uncomfortable. Moire effect can be reduced by adjusting the shooting distance or angle of the camera, but in order to prevent the pixel pitch from being recorded on the image sensor, secure a sufficient distance between the LED video wall and camera. even when the distance secured, the zoom lens used in the broadcasting studio must be operated by appropriately changing the magnification. If the focal length is changed by changing the magnification to obtain a desired angle of view, the pixel pitch may be unintentionally recorded. In this study we propose the range that the pixel pitch is not observed while changing the magnification ratio of the zoom lens when the distance from the video wall is sufficiently secured. The content was played back on the LED video wall and the LED video wall was recorded on the server using an HD camera equipped with a B4 mount zoom lens