• Proceedings of the Korean Fiber Society Conference
• /
• 1997.10a
• /
• pp.364-368
• /
• 1997

The purpose of this Study was to determine thermal sensation and physiological responses for men in summer indoor environment, under various air temperature and relative humidity, with male university students. Subjective Evaluation, Heart Rate Variability(HRV), Electroencephalogram(EEG) were examined. We found that comfort of people was achieved at 50% R.H., 24C, and the difference of skin temperature was found at the calf area as air temperature changes. At low air temperature and low humidity, heart rate was decreased, but there was no change at brain wave, keeping a-wave.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.30 no.2
• /
• pp.47-54
• /
• 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 Korean Wood Science and Technology
• /
• v.42 no.5
• /
• pp.571-578
• /
• 2014

As a way of developing wooden joint development, a glass fiber reinforced wood plate was manufactured to replace a steel plate. Also, the fracture toughness was evaluated. Through application to a cantilever-type specimen made of a column and a beam, the moment resistance performance was evaluated. For the fracture toughness specimen of the wood plate, 12 types were manufactured by varying the combination of a main member (veneer and plywood) and reinforcement (glass fiber sheet and glass fiber cloth). The results of the fracture toughness test indicated that the 5% yield load of the specimen using plywood was 18% higher than that of the specimen using veneer, and that the specimen reinforced by inserting glass fiber sheets between testing materials (Type-3-PS) had the highest average 5% yield load 4841 N. Thus, a moment resistance strength test was performed by applying Type-3-PS to a column-beam joint. The results of the test indicated that compared to the specimen using a steel plate and a drift pin (Type-A), the maximum moment ratio of the specimen using a glass fiber reinforced wood plate (Type-3-PS) and a drift pin (Type-B) was 0.79; and that a rupture occurred in the wood plate due to high stiffness of the drift pin. The maximum moment ratio of the specimen using a glass fiber reinforced wood plate (Type-3-PS) and a glass fiber reinforced wooden laminated pin (Type-C) was 0.67, which showed low performance. However, unlike Type-A, a ductile fracture occurred on Type-C, and the load gradually decreased even after the maximum moment.

• Journal of the Korea Concrete Institute
• /
• v.20 no.4
• /
• pp.531-539
• /
• 2008

The purpose of this study is to investigate the mechanical properties of high strength concretes reinforced with hooked steel fiber. For this purpose, total 36 specimens whose variables are concrete compressive strength, steel fiber aspect ratio, and steel fiber volume contents, are made and tested. From the test results including previous research work, flexural performance of steel fiber reinforced high strength concrete is evaluated in terms of flexural strength and toughness index. Flexural behavior of steel fiber reinforced high strength concrete is enhanced with respect to the fiber volume content, the aspect ratio, and concrete compressive strength. More efforts are devoted to evaluate quantitatively between the flexural strength and the structural parameters such as the fiber volume content, the aspect ratio, and concrete compressive strength.

• Design & Manufacturing
• /
• v.16 no.4
• /
• pp.24-33
• /
• 2022

Fiber-reinforced plastics(FRPs) have excellent specific stiffness and strength, so they are usually used as automotive parts that require high rigidity and lightweight instead of metal. However, it is difficult to predict the mechanical properties of injection molded parts due to the fiber orientation and breakage of FRPs. In this paper, the fiber orientation characteristics and mechanical properties of injection molded specimens were evaluated in order to fabricate automotive transmission side covers with FRPs and design a rib structure for improvement of their rigidity. The test molds were designed and manufactured to confirm the fiber orientation characteristics of each position of the injection molded standard plate-shaped specimens, and the tensile properties of the specimens were evaluated according to the injection molding conditions and directions of specimens. A gusset-rib structure was designed to improve the additional structural rigidity of the target products, and a proper rib structure was selected through the flexural tests of the rib-structured specimens. Based on the evaluation of fiber orientation and mechanical characteristics, the optimization analyses of gate location were performed to minimize the warpage of target products. Also, the deformation analyses against the internal pressure of target product were performed to confirm the rigidity improvement by gusset-rib structure. As a result, it could be confirmed that the deformation was reduced by 27~37% compared to the previous model, when the gusset-rib structure was applied to the joining part of the target products.

• Current Optics and Photonics
• /
• v.8 no.1
• /
• pp.45-55
• /
• 2024

A fiber spool with ultra-low vibration sensitivity has been demonstrated for the ultra-narrow-linewidth fiber-stabilized laser by the multi-object orthogonal experimental design method, which can achieve the optimization object and analysis of influence levels without extensive computation. According to a test of 4 levels and 4 factors, an L₁₆ (4⁴) orthogonal table is established to design orthogonal experiments. The vibration sensitivities along the axial and radial directions and the normalized sums of the vibration sensitivities are determined as single objects and comprehensive objects, respectively. We adopt the range analysis of object values to obtain the influence levels of the four design parameters on the single objects and the comprehensive object. The optimal parameter combinations are determined by both methods of comprehensive balance and evaluation. Based on the corresponding fractional frequency stability of ultra-narrow-linewidth fiber-stabilized lasers, we obtain the final optimal parameter combination A3B1C2D1, which can achieve the fiber spool with vibration sensitivities of 10^-12/g magnitude. This work is the first time to use an orthogonal experimental design method to optimize the vibration sensitivities of fiber spools, providing an approach to design the fiber spool with ultra-low vibration sensitivity.

• Journal of the Korea Institute of Building Construction
• /
• v.13 no.3
• /
• pp.253-262
• /
• 2013

The test on the mix of PVA fiber of low carbon inorganic composite as a cement substitute found it to be satisfactory in terms of flexibility and stiffness. The result of the evaluation of the properties of low carbon inorganic panel revealed that the absorptivity was low at 8 to 9%, which is lower than the KS value of 25%. Also, the test on non-combustibility and gas toxicity found that these factors satisfied the decision criteria. In the test on heavy metals discharges, Pb, Cd, Cr6+, Hg, and As were not detected. Regarding far-Infrared emissivity and formaldehyde emission, the substitute was found to be harmless to the human body. Therefore, if the issue of shrinkage, which is a disadvantage of inorganic composites, is addressed, it is judged that it is possible to develop a low carbon inorganic composite panel with better performance.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2002.05a
• /
• pp.53-56
• /
• 2002

External low-velocity impact loadings onto the composites cause reduction of stiffness and/or strength. The reductions indicate that internal(external) damages were developed within the composites. These damages could be matrix cracking, fiber/matrix debonding, or delamination between layers. In previous studies, damage evaluation have been done by applying secondary mechanical loading such as buckle-driven compressive, or fatigue, or flexural loadings. An evaluation method by applying indentation loadings on the composites was proposed. The load-displacement curves obtained from the indentation testing provided the extent of damages within the composites due to impact loadings.

• Structural Monitoring and Maintenance
• /
• v.5 no.1
• /
• pp.129-150
• /
• 2018

This paper presents the structural performance monitoring of an urban footbridge located in Hangzhou, China. The structural health monitoring (SHM) system is designed and implemented for the footbridge to monitor the structural responses of the footbridge and to ensure the structural safety during the period of operation. The monitoring data of stress and displacement measured by the fiber Bragg grating (FBG)-based sensors installed at the critical locations are used to analyze and assess the operation performance of the footbridge. A linear regression method is applied to separate the temperature effect from the stress monitoring data measured by the FBG-based strain sensors. In addition, the static vertical displacement of the footbridge measured by the FBG-based hydrostatic level gauges are presented and compared with the dynamic displacement remotely measured by a machine vision-based measurement system. Based on the examination of the monitored stress and displacement data, the structural safety evaluation is executed in combination with the defined condition index.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2001.11a
• /
• pp.70-75
• /
• 2001

There is a problem to be solved for improvement of durability and safety for concrete When the waterproofing and anticorrosive work of main concrete are design, the material a of construction need to be correctly applied to appropriate circumstance conditions. Epoxy mostly been used for concrete water tank structure. Lately, lots of subjects on adaption res in mortar for waterproofing and anticorrosive are under discussion. Then, we attempt to approach by evaluating and comparing every capabilities with waterproofing materials in this experiment. Capability evaluation items include the bond age and curing conditions, the bond strength after accelerated weathering test and fret impact resistance, a mount of water, seepage quan Through the experiment analysis, we found that waterproofingtity, drinking water chemicals resistance. and anticorrosive resin mortar used with glass fiber cloth, inorgar material is dominantly superior to other waterproofing materials. According to this paper, we suggest the resin mortar as a new surface treatment material water tank structure.