• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.706-713
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• 2015

Graphite foams (GFs) were prepared by adding different amounts of mesophase pitch (MP) into polyvinyl alcohol-acrylic acid (PVA-AAc) solution followed by the heat treatment. It was confirmed that the pore diameters of GFs were controlled by the slurry concentration, which was the mesophase content added in polymer solution, and their thermal conductivity and compressive strength were also controlled by porosities of GFs formed at different conditions. The resulting GFs in this study had the highest thermal conductivity of $53.414{\pm}0.002W/mK$ and compressive strength of $1.348{\pm}0.864MPa$ at 0.69 in porosity. The thermal conductivity of MP based GFs increased approximately 23 times higher than that of using isotropic pitch based GFs due to the developed graphitic structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.511-516
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• 2002

Pitch is a perception related to the subjective frequency that is one of the psychological aspects or attributes of tones. It is also an important factor to determine the sound quality together with loudness and timber. Although the study on pitch has been active in the field of speech communication, but its application to the product sound quality is not yet enough. In this study, the empirical data by Zwicker is made use in the modification of the currently available pitch extraction model based on the place theory. By applying this modified model to various sound samples composed of tonal or banded components, the applicability of the model is suggested. As a demonstration example, the algorithm is used for the sound quality analysis of a product noise having fundamental frequency and harmonics. The result shows that the pitch should be regarded as an important subjective cue in the sound quality analysis.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.13-22
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• 2007

This study was carried out to scrutinize possibility of manufacturing pitch pine (Pinus rigida) glued laminated timber in order to add values of pitch pine trees. Also, it was investigated to improve bending performance of pitch pine glulam. Pitch pine was imported as one of major plantation species in Korean peninsula. Machine stress rated grades of pitch pine lumber mostly ranged between E7 and E9. which grades were more or less inferior to producing high quality glulam. However, the adhesive properties between pitch pine and pitch pine, and between pitch pine and Japanese larch (Larix kaempferi Carr.), such as shear bond strength, wood failure rate and de-lamination rate of bonded layer submerged in cold and boiling water, were higher than Korean Standard criteria. These properties are essential for manufacturing glulam with single species or multiple species. The modulus of rupture (MOR) of pitch pine glulam exceeded the criterion of Korean Standard for glulam strength grade but modulus of elasticity (MOE) was lower than the criterion. On the other hand, the bending performances (MOR and MOE) were improved 20 percent by mixing with Japanese larch laminar. It is effective to arrange higher quality Japanese larch laminar at the outer layer of glulam for improving bending performances. In conclusion, it is possible to use low quality pitch pine as laminar of structural glulam for adding values of pitch pine.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.43.2-43.2
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• 2011

Wind turbine pitch/yaw bearings are relatively big and have different operating conditions like very heavy load to support compared with widely used industrial bearings. Once pitch/yaw bearings failed, according to their special surroundings, serious damages like higher repair costs and additional costs by stopped electricity generation are occur. Therefore, pitch/yaw bearings must be designed to have enough strength and fatigue life under actual operating conditions. In this study, with finite element analysis, it was investigated that stress distribution between rolling elements and raceway and comparatively analyzed using widely used guideline (NREL DG03). Design parameters of wind turbine pitch/yaw bearings are also analyzed, and it could be used as reference for the large bearing design field.

• Carbon letters
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• v.25
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• pp.89-94
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• 2018

In this study, we tried to prepare an isotropic spinnable pitch which can be useful to prepare the general purpose carbon fiber through the co-carbonization of biomass tar with ethylene bottom oil under two different preparation methods (atmospheric distillation, pressurized distillation). The results showed that the ethylene bottom oil added co-carbonization was very effective to decrease of the oxygen contents for obtaining a stable spinnable pitch. The pressurized distillation was more effective to reduce the oxygen functional groups of pitches than atmospheric distillation. The obtained spinnable pitch by the pressurized distillation showed higher pitch yield of 42% and lower oxygen content of 9.12% than the spinnable pitch by the atmospheric distillation. The carbon fiber derived from the pressurized distillation spinnable pitch by carbonization at $800^{\circ}C$ for 5 min showed that the higher tensile strength of carbon fiber was increased up to 800 MPa.

• Korean Journal of Optics and Photonics
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• v.12 no.5
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• pp.414-417
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• 2001

Experimentally, the aligned direction of AFLCs in electro-optic cells having both the substrates rubbed along the same direction is skewed by a few degrees from the rebbing direction. To explain why, we proposed "Torsional Rigid Body Model" and interpreted their skewing angle as the action of short pitch with the large shear stress. That is, the azimuthal an anchoring strength (about 35 dyn/cm) in the cell is much larger than the maximum shear stress (about 10$^{-6}$ dyn/cm) for the original pitch and so forbids the optic axis to skew. On the side hand, the strength is smaller than the maximum shear stress (about 42 dyn/cm) for short pitch and then allows the optic axis to skew.

• Journal of the Korean Applied Science and Technology
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• v.40 no.6
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• pp.1191-1200
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• 2023

The lithium ion battery has applied to various fields of energy storage systems such as electric vehicle and potable electronic devices in terms of high energy density and long-life cycle. Despite of various research on the electrode and electrolyte materials, there is a lack of research for investigating of the binding materials to replace polymer based binder. In this study, we have investigated petroleum pitch/polymer composite with various ratios between petroleum pitch and polymer in order to optimize the electrochemical and physical performance of the lithium-ion battery based on petroleum pitch/polymer composite binder. The electrochemical and physical performances of the petroleum pitch/polymer composite binder based lithium-ion battery were evaluated by using a charge/discharge test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and universal testing machine (UTM). As a result, the petroleum pitch(MP-50)/polymer(PVDF) composite (5:5 wt % ratio) binder based lithium-ion battery showed 1.29 gf mm^-1 of adhesion strength with 144 mAh g^-1 of specific dis-charge capacity and 93.1 % of initial coulombic efficiency(ICE) value.

• Carbon letters
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• v.1 no.3_4
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• pp.165-169
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• 2001

The C-type mesophase pitch-based carbon fiber (C-MPCF) was prepared throuch C-type spinnerette and compared the mechanical properties to those of round type mesophase pitch fiber (R-MPCF) and C-type isotropic pitch fiber (C-iPCF). The tensile strength and modulus of C-MPCF were about 18.6% and 35.7% higher than those of R-MPCF. The tensile strength of C-MPCF was 62% higher than that of C-iPCF of the same $8{\mu}m$ thickness because of more linear transverse texture, which could be easily converted to graphitic crystallinity during heat treatment. The torsional rigidity of C-MPCF was 2.37 times higher than that of R-MPCF. The electrical resistivity of C-MPCF was $8{\mu}{\Omega}{\cdot}m$. The C-iPCF shows far lower electrical resistivity than R-iPCF as well as the mesophase carbon fiber because of better alignment of texture to the fiber axis.

• Computers and Concrete
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• v.31 no.6
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• pp.527-536
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• 2023

Fiber Reinforced Polymer (FRP) bar has emerged as a viable and sustainable replacement to steel in reinforced concrete (RC) under severe corrosive environment. The behavior of concrete columns reinforced with FRP bars, spirals, and hoops is an ongoing area of research. In this study, 3D nonlinear numerical modelling of circular concrete columns reinforced with Glass Fiber Reinforced Polymer (GFRP) bars and transversely confined with GFRP spirals were conducted using fracture-plastic model. The numerical models and experimental results are found to be in good agreement. The effectiveness of confinement was accessed through von-mises stresses, and it was found that the stresses in the concrete's core are higher with a 30 mm pitch (46 MPa) compared to a 60 mm pitch (36 MPa). The validated models are used to conduct parametric studies. In terms of axial load carrying capacity and member ductility, the effect of concrete strength, spiral pitch, and longitudinal reinforcement ratio are thoroughly investigated. The confinement effect and member ductility of a GFRP RC column increases as the spiral pitch decreases. It is also found that the confinement effect and member ductility decreased with increase in strength of concrete.

• Carbon letters
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• v.2 no.2
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• pp.99-104
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• 2001

Partial mesophase (PM) pitch precursor was prepared from fluidized catalytic cracking-decant oils (FCC-DO) by chemical reaction in the presence of $Br_2$. The PM pitch heated-treatment at $420^{\circ}C$ for 9 h exhibited the softening point of $297^{\circ}C$ with 23% yield, and 55% anisotropic content. The PM pitch precursor was melt-spun through circular nozzle by pressurized $N_2$, stabilized at $310^{\circ}C$, carbonized at $700^{\circ}C$, $1000^{\circ}C$, and $1200^{\circ}C$. The enough stabilization introduced 16.4% of the oxygen approximately. The stacking height ($L_{c002}$) and interlayer spacing ($d_{002}$) of the as-spun fibers were 4.58 nm and $3.45{\AA}$ and the value became minimum and maximum at $700^{\circ}C$ respectively in the carbonization procedure. The tensile strength increased with an increase in the heat treatment temperature exhibiting highest value of 750 MPa at $1200^{\circ}C$ carbonization.