• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.331-338
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• 2006

This paper presents the experimental results on volumetric changes in ordinary portland cement concrete made with various water-to-cement ratios(W/C's) ranging from 0.32 to 0.50 and cured in low different conditions. Curing regimes employed in this work were designed to exhibit autogenous and drying shrinkage as well as swelling of concrete. The concrete avoided any moist evaporation(Regime f showed only autogenous shrinkage and the lower the W/C, the feater the autogenous shrinkage. The concrete exposed to air drying conditions at $20{\pm}1^{\circ}C$ and $60{\pm}3%$ RH after 6-day water curing at $20{\pm}1^{\circ}C$(Regime II) swelled and then started to shrink. The maximum swelling value of concrete developed in water curing was between 15 and $40{\pm}10^{-6}$, and the greatest total shrinkage(autogenous+drying shrinkage) was obtained for the mixture made with W/C of 0.32. The concrete let to air drying conditions(Regime III) showed greater total shrinkage compared to the concrete cured in Regime II. The concrete exposed to air drying condition after 6-day sealed curing(Regime IV) exhibited slightly smaller total shrinkage than that of the concrete cured in Regime III. Net drying shrinkage that can be derived from the results of Regime I, III, and IV increased as the W/C increased despite of similar total shrinkage. This result indicated that drying shrinkage governs total shrinkage of high-W/C concretes. In other words, a portion of autogenous shrinkage in total shrinkage increased in low-W/C concretes. Therefore, it should be controlled in terms of cracking potential. Finally, total shrinkage of high-strength and high-performance concrete made with low W/C can be effectively reduced by appropriate early moisture curing.

• Journal of Sericultural and Entomological Science
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• v.2
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• pp.1-31
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• 1962

The purpose of this treatise is to prove the presence of cystine in silk fiber through wide sampling throughout all the sericultural processes of Bombyx mori.; also to show that disulfide cross linkages exist in the silk fiber. The conclusions reached were as follows: 1. Crystalline cystine was obtained from silk fibroin using Folin's Method. 2. Analytical data showing the cystine content of silk fiber and its related materials were obtained using Sullvan's Method as follows: Material Percent Cystine A. Mulberry leaf protein 0.175 B. Silkworm egg 0.33 C. Silkworm Body, matured, fat extracted, without silk gland 0.41 D. Silk gland, matured 1.23 E. Silkworm feces none F. Silkworm pupa, fat extracted 0.30 G. Silkworm moth, fat extracted 0.60 H. Raw Silk 0.22 I. Fibroin 0.175 J. Sericin 0.30 3. The presence of cystine in the silkworm was substantiated the existence of 0.175 % methionine in mulberry leaves and 0.12% methionine in the silk gland. 4. Part of the sulfhydryl compounds in the silk gland is believed to transfer to serine and methionine, with the former being secreted into the liquid silk finally as silk fiber and the latter used for nutritive purposes in the growing of silk gland tissue. 5. The cystine content is variable by mulberry species, silkworm species, sex, breeding process, and other culturing environments. 6. Hybrid silkworms require more nutritive amino acids for effective growth than the original parents, and secrete less of them as silk fiber. 7. From such an observation, the amino acid composition of silk fiber is believed to be fairly flexible. Cystine if included in the amorphous part of the fiber, especially in sericin. 8. The result from enriching the silkworm diet with pure cystine or wool cystine did not result in any advantage, therefore it is believed that the natural cystine and methionine contents in the mulberry leafaregoodenoughforsilkwormnutrition. 9. The disulfide cross linkage in silk fiber was verified by using the Harris Method. Contraction took place following the treatment of the fiber with various salts and acids. Comparisons were made with wool fiber. 10. During these experiments, the fibrious structure of silk fiber and the net-globular liquid form were photographed microscopically. It is believed that the globules of liquid silk are net-formed by the inter attraction of the OH ion of the globular peptide and the H ion of water as shown by the hair cracking behavior of the film. The net-globular protein precipitation from the mulberry protein solution showed that mulberry is a proper diet for the formation of fibrous protein in the silk fiber. 11. The significance of the presence of cystine in silk fiber as emphasized in this paper should result in modification of the general conception that cystine is absent from this fiber. NOTICE: A part of this treatise was presented at the annual Korea Sericultural Society meeting held in 1961.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.3
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• pp.1-7
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• 2018

As part of a research dedicated to the field evaluation of the durability of concrete subjected to freezing-thawing, this study analyzes the relationship between the surface roughness and the relative dynamic elastic modulus through image analysis. Four mix compositions with water-to-binder ratios (W/B) of 40%, 50%, 60% and 70% and without AE agent were considered to provoke early freezing. The basic physical properties of the mixes including the relative dynamic elastic modulus and the compressive strength were first evaluated experimentally according to W/B. Then, tests were performed to measure the surface roughness followed by photographs and SEM image analysis. The measured surface roughness tended to increase with larger number of freezing-thawing cycles regardless of W/B. The relative dynamic elastic modulus appeared to increase gradually with the number of cycles for the relatively denser mixes with W/B of 40% and 50%. Besides, the surface roughness increased only at rupture for the mixes with W/B of 60% and 70%. Moreover, the analysis of the photographs of the surface of the mixes with W/B of 40% and 50% revealed that the degradation progressed gradually from the surface with the freezing-thawing cycles. However, for the mixes with W/B of 60% and 70%, apparent change of the surface remained very insignificant until rupture at which damage like cracking could be observed. Consequently, the analysis of surface photograph or the measurement of the surface roughness presented some limitation in assessing the degree of freezing-thawing-induced degradation in case of relatively porous specimens. On the other hand, the photograph and surface roughness appeared to be sufficient for assessing such degradation for the mixes with W/B of 40% and 50%. Accordingly, the image of the surface and the surface roughness are potentially applicable on site for the assessment of freezing-thawing damages in relatively dense mixes.

• Journal of Food Hygiene and Safety
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• v.32 no.5
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• pp.434-442
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• 2017

The UV light in sunlight breaks down the chemical bonds in a polyolefin polymer through a process called photodegradation, ultimately causing cracking, chalking, colour changes, and loss of physical properties such as impact strength, tensile strength, elongation, and others. UV absorbers are used to prevent or terminate the oxidation of plastics by UV light. They are receptive to UV radiation and dissipate the energy harmlessly as heat. Benzotriazoles and benzophenones are used mainly in polyolefins such as polyethylene and polypropylene. In this study, we have developed a method for the analysis of 12 UV absorbers, which are Uvinul 3000, Cyasorb UV 24, Uvinul 3040, Tinuvin 312 and P, Seesorb 202, Chimassorb 81, Tinuvin 329, 234, 326, 328 and 327, migrated from the food packaging materials into four food simulants for aqueous, acidic, alcoholic and fatty foods. The UV absorbers in food simulants were determined by reversed-phase high performance liquid chromatograph-ultraviolet detector with 310 nm after solid-phase extraction with a hydrophilic-lipophilic balance (HLB) cartridge or dilution with isopropanol. The analytical method showed a good linearity of coefficient ($R^2{\geq}0.99$), limits of detection (0.049~0.370 mg/L), and limits of quantification (0.149~1.120 mg/L). The recoveries of UV absorbers spiked to four food simulants ranged from 70.05% to 110.13%. The developed method would be used as a reliable tool to determine concentrations of the migrated UV absorbers.

• Horticultural Science & Technology
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• v.29 no.3
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• pp.247-254
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• 2011

The agronomic characteristics, nutritional contents, and insect response of the potato clones transformed with a glufosinate ammonium resistance gene were evaluated. Among the 4 transgenic potato clones, the Bar 3 clone was selected as a promising one for commercialization. The Bar 3 clone showed similar tuber yield capacity but higher herbicide resistance as compared with the non-transgenic potato cv. Dejima. The herbicide resistance of the Bar 3 clone was more than 5 times higher when tested with the herbicide concentration recommended by the producer. The major agronomic characteristics of the Bar 3 clone were not different from those of the non-transgenic Dejima. The annual variation in yields and agronomic characteristics showed similar tendency for 2 years from the third to fourth generation after transformation. The tubers of the Bar 3 clone also showed low occurrence in common scab and physiological disorders such as cracking and secondary growth. But the reasons for such results are yet to be studied. Also, it was considered that the Bar 3 clone have a potential of reducing not only common scab occurrence but also soil erosion during potato cultivation in field. The nutritional contents (mineral compound, vitamin C and amino acid) and response to Spodoptera exigua of the transgenic potato clones were not significantly different.

• KOMUNHWA
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• no.70
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• pp.63-88
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• 2007

The purpose of this writing is to examine the places and instruments of the dissection for deformed animal carcasses excavated in shellfish stacks of the period of the Proto-Three Kingdoms(삼한) and the Three Kingdoms(삼국). The remains were chosen, which had been excavated and finished in the analysis of the animal carcasses, and the main objects are all shells and deer, especially among Mammalia. As the result, the dissection of shells was not taken place in the habitats of the animals, but inside or around of the residence of the people. For deer, too, it was done in the public place or specific area around and inside the residence. As concerns the method of dissection for shells, for Pelecypoda(부족류), represented by Meretrix lusoria(백합), the inner meat was taken out by wrenching the shell with a kind of small knives, or by boiling, and sometimes by cracking the middle of the shell in the case of big Meretrix lusoria and Dosinorbis japonicus(떡조개). For Rapana venosa(피뿔고둥), representative of Gastropoad(배발류), the people broke the top or some parts of the body to get the inner meat or used some kind of needles and stylus to pick the inner meat out after boiling. Abalones‘ meat was attached firmly to the shell, so very sharp and proper metal instruments were used to take the meat out Relatively small-sized Reishia clavigera(대수리),Top shell(밤고둥) meats were taken out by breaking the top parts after boiling, then sucking the meats, or by picking them out by using needles and stylus in the original shape. In the case of large Mammalia like deer, in the full consideration of the point that deer itself are used in various ways, they were dissected in the order of skinning, taking out the internal organs, cutting front and rear legs, separating joint parts and meats, extracting bone-marrow by 철정, 철부, ironed hand knife in very delicate ways. It seems that skinning, and front and rear legs' cutting were taken place in the place around the residence, on the other hand joint parts' separating and bone-marrow extracting in the residence. The tools for the dissection were confirmed to be hand-knife, honed ax, hammer stone, bondstone, needles and stylus, and some other sharp instrument. They were used properly according to objects.

• Food Science and Preservation
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• v.16 no.5
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• pp.650-655
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• 2009

This study was conducted to measure the quality characteristics of rough rice during low temperature drying by using an experimental dryer and heat pump with a capacity of 150kg at four temperature levels of 20, 30, 40, and $50^{\circ}C$. The quality and proper drying temperature of rough rice was investigated by measuring variations in moisture content, crack rates, germination rates and cooked rice. Temperatures over $40^{\circ}C$ is considered a high-temperature area, and below $40^{\circ}C$ is considered a low-temperature area. The drying rates were 0.3, 0.6, 0.9, and 1.3%/hr, and the crack ratios were 0, 1.6, 6.8, and 24.2% at the drying temperatures of 20, 30, 40, and $50^{\circ}C$, respectively, which showed that the higher the drying temperature was, the higher the drying rate and crack rate was. Therefore, 20 and $30^{\circ}C$ were found to be appropriate drying temperatures for avoiding crack formation, and $50^{\circ}C$ was inappropriate. At $40^{\circ}C$, the operation methods needed to be modified to limit cracking, such as increasing the tempering time. Also, as the drying temperature increased, the germination rate decreased. Germination rates at 20 and $30^{\circ}C$ were suitable for using the rough rice as a seed, and those at 40 and $50^{\circ}C$ were over 80%, which is the minimum allowable percentage. In the sensory evaluation of cooked rice, the quality of appearance, taste, and texture varied as a function of drying temperature. When considering these factors, the cooked rice that was dried at 20 and $30^{\circ}C$ was better than the cooked rice dried at high-temperature. Consequently, in view of drying temperature and rates, the best conditions for drying rough rice were below $30^{\circ}C$ and below 0.6%/hr.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.126-135
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• 2002

Plate bonding technique has been widely used in strengthening of existing concrete structures, although it has often a serious problem of premature falure such as interface separation and rip-off. However, this premature failure problem has not been well explored yet especially in view of local failure mechanism around the interface of plate ends. The purpose of the present study is, therefore, to identify the local failure of strengthened plates and to derive a separation criterion at the interface of plates. To this end, a comprehensive experimental program has been set up. The double lap pull-out tests considering pure shear force and half beam tests considering combined flexure-shear force were performed. The main experimental parameters include plate thickness, adhesive thickness, and plate end arrangement. The strains along the longitudinal direction of steel plates have been measured and the shear stress were calculated from those measures strains. The effects of plate thickness, bonded length, and plate end treatment have been also clarified from the present test results. Nonlinear finite element analysis has been performed and compared with test results. The Interface properties are also modeled to present the separation failure behavior of strengthened members. The cracking patterns as well as maximum failure loads agree well with test data. The relation between maximum shear and normal stresses at the interface has been derived to propose a separation failure criterion of strengthened members. The present study allows more realistic analysis and design of externally strengthened flexural member with steel plates.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.51-61
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• 2010

Ettringite $(Ca_6[Al(OH)_6]_2(SO_4)_3{\cdot}26H_2O)$ is a sulfate mineral that shows a complicate property in concrete. It is often called as "a cancer of concrete" because secondary ettringite formation in hardened concrete often cause expansion and cracking of concrete due to its expansive crystal structure. In the present study, we tested the possibility for crystal growth inhibition of secondary ettringite by crystallization inhibitors that are commercially used for scaling inhibitors in Korea. For the test, we developed a method of ettringite solution synthesis. Three types of crystallization inhibitors were selected and examined the effects On ettringite growth inhibition. The experimental results of ettringite solution synthesis indicated that ettringite was successfully synthesized under condition that the mass balance between calcium hydroxide saturated solution and aluminum sulfate solution was attained. Monosulfate and semisulfate were synthesized when the ratio of $Ca^{2+}$ ions to ${SO_4}^{2+}$ ions was increased. The induction time of ettringite crystallization was less than 2 min. and crystallization was almost completed within an hour. The experimental results of ettringite crystallization inhibition showed that organic PBCT (2-Phosphonobutane-1,2,4-Tricarboxylic Acid) and inorganic SHMP (Sodium Hexametaphosphate) were relatively less effective on ettringite crystallization inhibition under experimental conditions. However, organic HEDP (1-Hydoxyethylidene-1,1-Diphosphonic Acid) effectively prevented ettringite growth with producing amorphous gel phase materials up to inhibitor concentration 0.1 vol.% of aluminum sulfate solution.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.451-464
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• 2022

The high-level nuclear waste repository is a deep geological disposal system exposed to complex environmental conditions such as high temperature, radiation, and ground-water due to handling spent nuclear fuel. Continuous exposure can lead to cracking and deterioration of the structure over time. On the other hand, the high-level nuclear waste repository requires an ultra-long life expectancy. Thus long-term structural health monitoring is essential. Various sensors such as an accelerometer, earth pressure gauge, and displacement meter can be used to monitor the health of a structure, and a piezoelectric sensor is generally used. Therefore, it is necessary to develop a highly durable sensor based on the durability assessment of the piezoelectric sensor. This study designed an accelerated life test for durability assessment and life prediction of the piezoelectric sensor. Based on the literature review, the number of accelerated stress levels for a single stress factor, and the number of samples for each level were selected. The failure mode and mechanism of the piezoelectric sensor that can occur in the environmental conditions of the high-level waste repository were analyzed. In addition, two methods were proposed to investigate the maximum harsh condition for the temperature stress factor. The reliable operating limit of the piezoelectric sensor was derived, and a reasonable accelerated stress level was set for the accelerated life test. The suggested methods contain economical and practical ideas and can be widely used in designing accelerated life tests of piezoelectric sensors.