• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.3
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• pp.72-83
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• 2022

This paper studied the effect on the microstructure, electrical properties, and compressive strength of cement mortar containing carbon fiber (CF) and steel fiber (SF), which are conductive materials. The resistivity of conductive fiber-reinforced cement mortar (FRCM) was measured using the 4-probe method, and the compressive strength was measured based on the compression test. Their performance was compared and reviewed with plain mortar (PM). Furthermore, the surface shape and composition of the fracture surface of the conductive FRCM were analyzed using a scanning electron microscope (SEM) and an energy disperse X-ray spectrometer (EDS). The results showed that the resistivity gradually increased as the curing time increased in all specimens, whereas the resistivity decreased significantly as the fiber volume fraction increased. Adding steel fibers up to 1.25% did not affect the resistivity of cement mortar considerably. On the contrast, the resistivity of carbon fiber was somewhat decreased even at low contents (ie, 0.1 to 0.3%), and thereafter, it was significantly decreased. The percolation threshold of the conductive CFRCM containing CF used in this experiment was 0.4%, and it is judged to be the optimum carbon fiber dosage to maximize the conductive effect while maintaining the compressive strength performance as much as possible. For the surface shape and composition analysis of conductive FRCM, the fracture surface was observed through SEM-EDS. These results are considered to be very useful in establishing the microstructure mechanism of reinforcing fibers in cement mortars.

• Journal of the Korean Wood Science and Technology
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• v.32 no.4
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• pp.66-73
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• 2004

Three species of Italian poplar (Populus euramericana), red pine (Pinus densiflora) and oriental oak (Quercus variabilis) were selected for this study. They were cut so that the distances between each of tips and roots for a pair of fingers were 0, 0.15, 0.30 and 0.45 mm. Poly vinyl acetate (PVAc) and resorcinol-phenol resin (RPR) were used for finger-jointing. Compressive test parallel to the grain was conducted for the finger-jointed specimens. The results were as follows: The efficiency of compressive Young's modulus of finger-jointed timber to solid wood indicated low values, whereas the efficiency of compressive strength indicated high values of more than 90% in all species, especially, it was found that those of red pine indicated markedly high values of more than 97%. The efficiency of compressive displacement of Italian poplar finger-jointed timber was 2 times higher than solid wood, and it was 1.2 and 1.3 times higher than solid woods in red pine and oriental oak, respectively. Also, it was found that 0, the distance between each tip and root for the fingers, indicated the highest efficiency of compressive strength performance in Italian poplar finger-jointed timber, and for red pine and oriental oak finger-jointed timbers, the distances of 0.15 and 0.30 were found to indicate the highest efficiency.

• Journal of the Korean Wood Science and Technology
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• v.32 no.5
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• pp.75-85
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• 2004

The natural dyes from Gardenia jasminoides, Carthamus tinctorius L., Rhus javanica, Lithospermum erythrorhizon, Caesalpinia sappan L., and Castanea crenata were extracted under different pH in distilled water, As the pH in distilled water went from acid to alkali, the much deeper colors in the same color tone were generated from the individual plant species. Before dyeing, wood species were treated by different mordants including AI, Cu, Cr and Fe for color-fixing between wood and the natural dyes. Each mordant could develop independent color on the surface of the woods. The wood species dyed by the natural dyes created deep-tone colors according to higher pH and temperature of the dyeing solution, leading to deeper penetration of the dyes into the wood tissues. Finally through the computer modelling of natural-dyed wood furniture, it was confirmed that the colored furniture can adequately be compatible with the current interior spaces of diverse colors.

• Science of Emotion and Sensibility
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• v.24 no.4
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• pp.117-128
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• 2021

In this work, we study smart gloves that can prevent carpal tunnel syndrome when using a mouse. Because the left and right wrist movements are fine, a tensile fabric sensor with a large gauge factor and low hysteresis was required before the study. A universal testing machine was used to calculate each gauge rate on four different fabrics, and the fabric with the least hysteresis was selected. In addition, three attachment methods were analyzed using Arduino to select a method with a large sensor value change. For prototypes made by attaching to the selected fabric, data patterns were analyzed using Arduino. The first method identifies only one sensor (A sensor), and the second identifies two sensors (A and B sensors). When the wrist is bent to the right, tensile fabric sensors are attached to both the left (A sensor) and right (B sensor) sides of the wrist, the A sensor is strained, increasing the △sensor value, and the B sensor is relaxed, decreasing the △sensor value. However, when the wrist was bent to the left, the pattern was analyzed in the opposite direction. Through this study, we examined smart gloves to prevent carpal tunnel syndrome with an algorithm that turns on the LED when the wrist is bent, and based on the results of this study, we will directly use mice on 10 people to identify problems and solve problems when used.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.14-22
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• 2022

In this study, a fire test was conducted to evaluate the fire performance of precast concrete (PC) slabs in an outdoor environment in response to the increase in fire incidents caused by the growth of warehouses. Prior to the field fire test, the tensile yield strength of the tendon at elevated temperatures was tested to analyze the mechanical properties. Also, by referring to previous studies, the thermal properties of tendon and the mechanical and thermal properties of concrete were investigated. A field fire test was conducted to analyze the structural and fire performance of two identical slabs with 50 and 150 mm bearing length. As the bearing length increased, deflection and horizontal displacement decreased. The fire test lasted for 200 minutes without the collapse of slabs, validating current codes. Based on the structural performance which maintained even with concrete spalling and rupture of some tendons, the bonded method is assumed to be practical in pre-tensioned PC slabs. The results of fire test are expected to be utilized in evaluating the fire performance of PC slabs in warehouses.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.139-147
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• 2022

In this study, we designed a high-strength, low-alkali type cement composite for artificial reef by mixing various binders and evaluated whether it is possible to manufacture it with an ME method 3D printer. As a result of the tests, it is found that it is important to control the water-binder ratio, the silica sand-binder ratio, and the type of silica sand in order to control the fluidity of the cement composites to enable 3D printing. The surface quality of 3D printer output can be achieved by adjusting the amount of viscosity agent added while obtaining printable fluidity. In the cement composites mixing proportion using the alpha-type hemihydrate gypsum, a setting control agent needs to be used to control the quick setting effect. It is also necessary to derive the time to maintain the fluidity, and to apply it when printing. To obtain the required strength, the mix proportion needs to be modified while satisfying the fluidity level of 3D-printable cement composites. In the present study, 3D-printable mix proportions were designed by the use of multi-component binders including alpha-type hemihydrate gypsum a for low-alkali type artificial reefs, and the printability was confirmed. A further study needs to be performed to quantitatively evaluate the alkali reduction effect.

• Science of Emotion and Sensibility
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• v.25 no.3
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• pp.77-90
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• 2022

This study seeks to develop a stretch sensor for measuring the wrist movements of people using fishing lures. In order to confirm wrist movement, a stretch sensor was attached to the wrist band, and measurements of the dorsiflexion, plantar flexion, and fishing landing motion were measured using a scale to gauge factor, tensile strength, and elongation recovery rate. A conductive sensor using CNT dispersion was developed and applied to the E-band under the same conditions. A total of 15 sensors of the same size and five types of impregnation once, twice, and three times each were used to measure the gauge factor using UTM. The sensor that was impregnated twice had the best gauge rate, and the prototypes were manufactured with three sensors with high gauge rates and tensile strength. The results of the operation test conducted by connecting to the Arduino showed that Sample 1, which had the highest tensile strength and gauge factor, had a stable graph wavelength in three operations. Samples 2 and 3 showed stable wavelengths in the dorsiflexion and the plantar flexion; however, signal noise appeared in the fishing landing motion. This showed stable wavelengths in the two motions, but the wavelengths of the graphs differ depending on the tensile strength and gauge factor in the fishing landing motion. As a result, it was possible to identify the conditions necessary for manufacturing a stretch sensor for measuring wrist movement. This study will contribute to the development of smart wearable products for lure fishing.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.4
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• pp.384-389
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• 1989

Thirteen varieties of Tongil type and ten of Japonica type which were produced in Korea, in 1985, were campa red in namely, width, thickness, length and weight of rice grains. Thousand-grain weight of paddy, brown rice and milled rice were not significantly different between Tongil type and Japonica type, but difference of paddy-brown rice and brown rice-milled rice had significant (p<2,859** and 4.316***, respectively), and the ratio of difference of paddy-brown rice was higher Tongil type than Japonica type. Width, thickness and length of paddy, brown rice and milled rice was significant (width : p<5.189***, 5.289** and 5.466***, thickness: p<3.371** 4.074*** and 5.988***, length: p<3.016**, 4.419*** and 5.492*** in paddy, brown rice and milled rice, respectively) between the Tongil type and Japonica type, and then the width and thickness of Japonica type were thicker than Tongil type, but length of Japonica type was shorter than Tongil type width/thickness ratio of paddy wes significant (p<2.396*) between the Tongil type and Japonica type, but its brown rice and milled rice was not. And length/width and length/ thickness ratio of paddy, brown rice and milled rice were significant (length/width : p<5.525***, 5.495*** and 5.863***, length/thickness: p<4.734***, 6,863*** and 8.425*** in paddy, brown rice and milled rice) between the Tongil type and Japonica type, and then its ratio were higher Tongil type than Japonica type.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.3
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• pp.266-270
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• 1991

Storage in the form of brown or milled rice saves space and cut cost rather than storage of rough rice, the common way of grain storage in Korea. But, brown or milled rice may be more susceptable to grain aging and sensory change than rough rice. Rice stored in government warehouse for 20 months after harvest was hulled into brown or milled rice and packaged with kraft paper bag (paper package), polyprophylen (PP package), and polyethylene (PE package). Then, after those rice packages were stored under room condition for one year, we investigated germinability, fat acidity, and sensory change to determine milling and packaging effects. Germinability of rough and brown rice was decreased significantly after long-term storge. In germination rate, Chucheong cultivar was lower than Milyang #23, brown rice was lower than rough rice, but there was no differences within packaging materials. TTC test which had a significant correlation with germinability can be used as a handy procedure for predicting grain germination. Fat acidity was increased as the order of rough < milled < brown rice in terms of milling, and PP < paper < PE package in terms of packaging materials. Especially, storage of brown rice increased fat acidity above 30 mg KOH, indicating one of characteristics of grain aging. To prevent from high fat acidity it was necessary to store in forms of rough grain with paper or PP packaging and milled rice with paper, or PP, or PE packaging. In sensory test of stored grain, eating quality in brown rice was the worst because of acidification of fatty acid. Also, eating quality of stored grain became worse as fat acidity increased.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.1
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• pp.55-62
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• 1994

The germplasms of naked barley evaluated for starch content were 137 crossing blacks and progeny lines obtained from the breeding program of the Wheat and Barley Research Institute, 540 Tabdong Kwonsungu Suwon, in the 1988/1989 season. Starch content was distributed between 49.15 and 62.50% with a mean of 57.20%. It was high in the bred lines and the Uz type lines than the imported, uz type or lax type ones. The range observed for seed coat weight was 1.12-3.02mg and the mean seed coat weight was 1.88mg. The seed coat weight ratio to kernel weight was measured between 4.0 and 8.7% with a mean of 6.5%. The varieties differ greatly in the characteristics depending on the plant type and origin of germplasms. The variation observed with protein content ranged from 9.60 to. 15.90% while the average was 12.86%. Starch content was negative relationships with kernel weight, seed coat weight, seed coat weight ratio., kernel width, kernel thickness and protein content, and starch content was higher in smaller kernels within a variety. The weight and weight ratio. of seed coat were positively correlated with the width, thick-ness of kernels, whilst they were negatively correlated with starch content. The heritability of starch content was 30.0%.