• Journal of the Korean Wood Science and Technology
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• v.16 no.1
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• pp.9-20
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• 1988

Lespedeza species have been widely used not only as plant resources for bark, leaves and honey, but also as erosion control materials. This study was carried out to investigate the structural and wood tiber characteristics in order to obtain basic information for the utilization of the wood. The wood structure was investigated for 10 selected species and the wood fiber, for the 5 selected species among Lespedeza species distributed all over the country. The following results were obtained. In the cross section, campylotropis showed ray diffuse porous wood, L. bicolor, L. cyrtobotrya, L. thunbergii var. intermedia, diffuse porous wood, and L. tomentella, L. angustifolioides. L. maritima, L. robusta, L. patentibicolor, ring porous wood. The maximum diameter of a single vessel ranged 66-123 ${\mu}$ in all species. Campylotropis showed the most number of vessels, L. angustifolioides, the least. The number of ray per mm ranged 7-22, Campylotropis showed the most number of rays, L. angustifolioides, the least. In the radial section the average length of vessel ranged 121-250 ${\mu}$ in all species. L. thunbergii var. intermedia showed the longest vessel, L. tomentella, the shortest. In tangential section the average width of the uniseriate ray ranged 9.2-14.7${\mu}$, that of the multiseriate ray, 19.2-42.1 ${\mu}$. The average height of the uniseriate ray ranged 143.0-1162.0 ${\mu}$. The width of fiber ranged 10.12-13.61 ${\mu}$, L. maximowiezii showed the narrowest tiber, L. thunbergii var. intermedia. the widest, the thickness of fiber wall ranged 2.93-3.71 ${\mu}$ in the five species. L. maximowiezii showed the most thin fiber wall, L. thunbergii var. intermedia, the thickest, L. cyrtobotrya showed the difference in the size of fiber between the shade and the sunny sites but L. maximowiezii showed no difference. There was significant difference in fiber length, fiber width and wall thickness between L. eyrtobotrya and L. maximowiezii.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1E
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• pp.25-30
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• 2002

We report on the development of a fiber optic hydrophone consists of a sensing Michelson interferometer and a compensating Mach-Zehnder interferometer for optical path length compensation. The double interferometer configuration has the following advantages: the hydrophone can be made more small; a laser source with a relatively short coherence length can be used; and the compensating interferometer can be located near the signal processing electronics, far away from the sensing interferometer and noise introduced by reference arm can be greatly reduced. The performance of the hydrophone is evaluated experimentally by immersing the sensing interferometer in a water tank to detect underwater acoustic signals generated by an acoustic wave projector. Experimental results show that over the frequency range of 1 to 4 kHz, the hydrophone has an almost flat response with an average normalized sensitivity of -302 dB re 1/ μ Pa.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.507-510
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• 2001

A numerical analysis based on the nonlinear Schroedinger equation is presented to analyze the propagation stability of the average soliton in a simple nonlinear amplifying loop mirror. The ratio of amplification period to soliton period and the length fraction of the erbium-doped fiber in the loop are varied to investigate their effects on the soliton stability. It is observed that stable soliton propagation is obtained even when the amplification period is only slightly shorter than the soliton period when the length fraction of the erbium-doped fiber in the loop is small, which is different from the previously published condition for stable average soliton propagation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.159-166
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• 2006

Although the strain distribution along the length of a beam in buildings or infrastructures is non-uniform, most fiber optic sensors are point sensors that can measure the strain only at a local point of a beam. Long gage fiber optic sensors that measure integrated strain over a relatively long length can consider strain variation. This type of sensor was found to be efficient and useful for monitoring large-scale structures. On the other hand, the maximum strain or stress in a beam can not be measured with long gage optic sensors. However, for the assessment of the safety of multi-span steel beams subjected to various vertical loads, the maximum strain or stress measured during monitoring is required for comparison with the allowable stress of the beam calculated by a design code. Therefore, in this paper, mathematical models are presented for determination of the maximum values of strains in more three-span steel beams based on the average strains measured by long gage optic sensors.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.15 no.3
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• pp.213-220
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• 2005

Penetration and health effect of fibers was related with their diameters and length. The purpose of this study is to characterize and compare the diameter and length of airborne man-made mineral fibers(MMMF) or synthetic vitreous fibers in the related industries. The average fiber length of the continuous filament glass, rock wool, refractory ceramic, and glass wool fibers production industries approximately 27, 28, 35, $50-105{\mu}m$. Airborne glass fibers were longest in all the type of MMMFs. The average diameters of airborne fibers generated from refractory ceramic, rock wool, glass wool, continuous filament glass fibers production industries were approximately 1.0, 1.6, 1.5-4 and $10{\mu}m$, respectively. The percentages of respirable fibers(<$3{\mu}m$) were 94% for RCFs, 73% for rock wool fibers, 61.0% for glass fibers, and 1.6% for filament glass fibers. The length of glass fibers were the longest in all types of fibers, and length of the others were similar. The refractory ceramic fibers were smallest in diameters and highest in fraction of respirable fibers.

• Journal of the Korean Society for Advanced Composite Structures
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• v.7 no.1
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• pp.25-31
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• 2016

Bond stress between cast-in-place ductile fiber reinforced cementitious composites and CFRP plank were experimentally analyzed. As failure shape, the mixture of failure between CFRP plank and epoxy, and failure between concrete and epoxy was shown. In case of RFCON from the suggested simple bond slip relationship, the maximum average bond stress was 5.39MPa, the initial slope was 104.09MPa/mm, and the total slip length was 0.19mm. PPCON showed the maximum average bond stress of 4.31MPa, the initial slope of 126.67MPa/mm, and the total slip length of 0.26mm, while RFCON+ appeared to have 8.71MPa, 137.69MPa/mm, 0.16mm. PPCON+ had 6.19MPa maximum average bond stress, 121.56MPa/mm initial slope, and 0.34mm total slip length. To comprehend the behavior of composite structure of FRP and concrete, local bond slip relation is necessary, and thus a simple relation is suggested to be easily applied on hybrid composite system.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.2
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• pp.47-54
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• 1998

Refining is one of the most important processes of fiber treatment that provides optical and physical properties of final paper products. The evaluation method of refining progress is usually freeness (CSF) or wetness (SR) test because of its rapidity and convenience. However, there are some deficiencies in using freeness or wetness test to evaluate pulp fibers accurately because its results are more influenced by fines contents than extent of fibers treatment. The objective of this study is to show the deficiency of wetness in evaluating the refining process. For this, beating is done by varying the beating load. Handsheets are made after beating until 25 and $32^{\circ}C$ SR, and then paper properties are measured. Refined fibers are analyzed by fiber length, fines contents, curl, kink, WRV, and zero-span tensile strength. The results show that longer beating time is required to reach the same wetness at lower beating load. There are differences in the average fiber length, distribution curve of fiber length, fines contents, curl, kink, WRV of long fiber fraction, drainage time, and zero-span tensile strength of rewetted sample at different beating load. At the low beating load in the same wetness, apparent density, breaking length, burst strength, and tear strength are higher, while opacity and air permeability are lower than those of the high beating load. Using Page s equation, which shows the relationship among tensile strength, intrinsic fiber strength, and interfiber bonding strength, interfiber bonding strength is calculated and analyzed to explain final paper properties. At $25^{\circ}C$ SR, interfiber bonding strength is only slightly higher at 2.5kgf beating load, while the intrinsic fiber strength is substantially higher. At $32^{\circ}C$ SR, intrinsic fiber strength is a little bit higher at 2.5kgf beating load, and interfiber bonding strength is remarkably higher than those of 5.6kgf beating load. These results can be used to explain the different properties of the final paper at selected beating loads.

• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.50-56
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• 2013

Optical-fiber electronic speckle pattern interferometry (ESPI) is a non-contact, non-destructive examination technique with the advantages of rapid measurement, high accuracy, and full-field measurement. The optical-fiber ESPI system used in this study was compact and portable with the advantages of easy set-up and signal acquisition. By suitably configuring the optical-fiber ESPI system, producing an image signal in a charge-coupled device camera, and periodically modulating beam phases, we obtained phase information from the speckle pattern using a four-step phase shifting algorithm. Moreover, we compared the actual defect size with that of interference fringes which appeared on a screen after calculating the pixel value according to the distance between the object and the CCD camera. Conventional methods of measuring defects are time-consuming and resource-intensive because the estimated values are relative. However, our simple method could quantitatively estimate the defect length by carrying out numerical analysis for obtaining values on the X-axis in a line profile. The results showed reliable values for average error rates and a decrease in the error rate with increasing defect length or pressure.

• Journal of the Korean Wood Science and Technology
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• v.43 no.2
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• pp.145-155
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• 2015

Fiber morphology and basic characteristics of Legi bamboos (Gigantochloa atter) growing on Yogyakarta were studied considering their age and height positions in the culms. Culms of 4, 16, and 40 months were harvested, and their total lengths were measured. The length, diameter, and wall thickness of each internode were measured. All the sample culms were divided into three different parts along the height, and their fiber dimension and physical properties were observed. The data obtained were analyzed by analysis of variance. The results showed that the culms had a diameter of 5.8 to 10.8 cm. The lowest internodes always showed the shortest length and the thickest wall. The culms had an average fiber length of 2.41 mm and Runkel ratio of 0.61. Fiber length was affected by the height, while fiber diameter, lumen diameter, and fiber wall thickness were affected significantly by the age of the culms. The culms had high green moisture content (GMC) of 157.89%, and basic density (BD) of $456.67kg.m^{-3}$, a total longitudinal shrinkage of 0.35%, and relatively low R/T shrinkage ratio. The interactions between age and height were affected GMC and BD.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.3
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• pp.14-21
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• 2010

Three different species of cattails (Typha orientalis, Typha angustata, Typha latifolia) cultivated in South Korea were examined as raw materials for the production of pulp and paper. Soda pulping with anthraquinone was used for the stems and the leaves of cattail, separately. Addition of anthraquinone in soda pulping improved the yield greatly. Chemical components between three cattail species and within each species (leaves and stem) gave little differences. Average fiber length of the bleached cattail fibers was a little shorter than that of the HwBKP of Eucalyptus. Average fiber width of the cattail fibers was a half of that of the HwBKP. Compared to the HwBKP, cattail pulp gave higher breaking length, higher opacity, and better smoothness at equivalent freeness.