• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.417-420
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• 2008

The requirement for durability of concrete is increasing recently as a large-scale concrete structure is built. For this reason, the concern about high-durable concrete is being high. Recently, metakaoline to be profitable in economical aspect as well as to have strength and durability of level similar to silica fume is evaluated highly as new admixture. In this study, the scaling, the drying shrinkage, the chloride resistance and the air-void structure are compared for both metakaolin and silica fume concrete. According to the results, the replacement of metakaoline improved the resistance of chloride penetration, freezing and thawing in concrete. On the other hand, as metakaolin was replaced to 10%, it was similar level with OPC in the property of scaling. It was showed that replacement of only metakaoline was similar with OPC in the drying shrinkage. However, MS5 reduced the drying shrinkage about 10%. In conclusion, replacement of the metakaoline 10% is the most excellent performance in terms of durability of concrete.

• Journal of the Korean GEO-environmental Society
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• v.15 no.10
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• pp.53-62
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• 2014

In Korea, the pipe type that has been well used as sewage pipe from the past is primarily a rigid pipe which is represented by concrete hume pipe, but the use of it is being decreased sharply because of the problems such as tube erosion and incomplete watertightness securing through the time. On the other hand, the use of flexible pipe has been increased because its construction ability is excellent on account of its light weight as well as it is resistant to corrosion. However, because there are lacks of market's confidence in flexible pipe and occurrence cases of partial damage incomplete caused by compaction control, cause analysis and management for them are needed. Therefore, this study tried to estimate the deformation characteristics of pipe caused by each condition through numerical analysis changing construction sequence, rigidity of pipe, strength of ground concrete under the pipe, relative compaction ratio of sand foundation under the pipe and relative compaction ratio of backfill material above the pipe. Evaluation result is that influence on each factor is confirmed and the quality control of sand around the pipe are turned up to be important.

• Journal of Korean Home Economics Education Association
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• v.23 no.2
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• pp.89-107
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• 2011

In this work, we investigated the perceptions of marriage among married people through in-depth interviews with twenty-two married men and women. The results of our analysis on the in-depth interviews are as follows. 1. Married men and women are well aware of the fact that. in a marriage life, one must sacrifice something in order to get anything. That is, even though they have yearning for their lost days of single life and they miss those days, on the other hand, they think that, through marriage, they feel more stable with a sense of belonging to the family. and they are no longer feeling lonely. 2. Married people consider that marriage is something you really have to experience yourself before one knows what it is like to be married. That is, they consider that, while, being single is just like tasting only a little bit of the flavor of life, marriage is like tasting the true meaning of life. The true meanings of life that married people are trying to find are "the strength they get from their family and children", "the journey of finding one's true self through overcoming hardships of life", "the joy and comfort of living together as a family", and finally "the broader life experience and higher quality of life".

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.9
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• pp.707-711
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• 2013

Carbon nanotubes(CNT) has strength and chemical stability, greatly conductivity characteristics. In particular, MWCNT (multi-walled carbon nanotubes) show rapidly resistance sensitive for changes in the ambient gas, and therefore they are ideal materials to gas sensor. So, we fabricated NOx gas sensors structured MOS-FET using MWCNT (multi-walled carbon nanotubes) material. We investigate the change resistance of NOx gas sensors based on MOS-FET with ultra lean NOx gas concentrations absorption. And NOx gas sensors show sensitivity on the change of gate-source voltage ($V_{gs}=0[V]$ or $V_{gs}=3.5[V]$). The gas sensors show the increase of sensitivity with increasing the temperature (largest value at $40^{\circ}C$). On the other hand, the sensitivity of sensors decreased with increasing of NOx gas concentration. In addition, We obtained the adsorption energy($U_a$), $U_a$ = 0.06714[eV] at the NOx gas concentration of 8[ppm], $U_a$ = 0.06769[eV] at 16[ppm], $U_a$ = 0.06847[eV] at 24[ppm] and $U_a$ = 0.06842[eV] at 32[ppm], of NOx gas molecules concentration on the MWCNT gas sensors surface with using the Arrhenius plots. As a result, the saturation phenomena is occurred by NOx gas injection of concentration for 32[ppm].

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2374-2385
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• 1994

SiCw/Al composite material is especially attractive because of their superior specific strength, specific stiffness, corrosion fatigue resistance, creep resistance, and wear resistance compared with the corresponding wrought Al alloy. In this study, Fatigue crack growth behavior and fatigue crack path morphology(FCPM) of SiC whisker reinforced Al 6061 alloy with 25% SiC volume fraction and Al 6061 allay were performed. Result of the fatigue crack growth test sgiwed that fatigue crack growth rate of SiCw/Al 6061 composite was slower than that of Al 6061 matrix therefore it was confirmed that Sic whisker have a excellent fatigue resistance. And Al 6061 matrix had only FCPM perpendicular to loading direction. On the other hand SiCw/Al 6061 composite had three types in fatigue crack path morphology. First type is that both sides FCPM of artificial notch are perpendicular to loading direction. Second type is that a FCPM in artifical notch has slant angle to loading direction and the other side FCPM is perpendicular to loading direction. Third type is that both sides FCPM of notch have slant angle to loading direction. It was considered that this kinds of phenomena were due to non-uniform distribution of SiC whisker and confirmed by SEM observation for fracture mechanism study.

• Journal of Korea Foundry Society
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• v.17 no.2
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• pp.158-163
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• 1997

Properties of $Al_{86}Ni_6Ce_4Mg_4$ alloy powder produced by helium gas atomization process were investigated by using DSC, XRD, SEM and TEM. The powders below 32 ${\mu}m$ in diameter were identified as an amorphous phase mixed with a ${\alpha}-Al$ phase. $Al_{86}Ni_6Ce_4Mg_4$ bulk alloy was manufactured by hot extruding the alloy powders at various temperatures, and the estimation of its mechanical properties was carried out subsequently. As a result, the bulk alloy extruded at the temperature below $450^{\circ}C$ exhibited the microstructure in which the near-spherical shape of some powders below 20 ${\mu}m$ were nearly unchanged and fine voids between matrix and powders were formed during extrusion process. On the other hand, the tensile strength and elongation at room temperature for $Al_{86}Ni_6Ce_4Mg_4$ bulk alloy extruded at $450^{\circ}C$ were 750 MPa and 7.5%, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.2
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• pp.47-59
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• 1982

It is well practised in the field of concrete engineering that the effort of improving the low slumped concrete and uplifting the quality of the soft concrete by adopting the superplasticizer. In this paper, an attempt is made to find out the optimum mix design of the superplasticized concrete with an unit weight of cement 400 kg and the range of $19{\pm}1cm$ of slump by variatlng the sand percentage, unit water content and the dosage of superplasticizer. As a result, the author obtained the basic idea on the optimum mix design and strength of superplasticized concrete. On the other hand, it is also considered during the research the method of preventing the slump loss of the superplasticized concrete due to the delayed time after concrete mixing.

• Parasites, Hosts and Diseases
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• v.51 no.2
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• pp.243-246
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• 2013

It is known that physicochemical conditions (e.g., pH, temperature, and ionic strength) affect the size of trichomonads. In this study, the sizes of 4 isolates of Trichomonas vaginalis cultured for more than a year (called "old T") and 3 isolates freshly isolated from vaginitis cases (called "fresh T") were compared by scanning electron microscopy. Although the fresh T had shorter body length, body width, and flagellar length than old T, total length (about $26{\mu}m$), including body length, flagella length, and axostyle length was almost the same in the 2 groups. A striking difference was observed between the axostyles of the 2 groups; the axostyle length of the fresh T ($8.2{\mu}m$) was more than twice as long as that of the old T ($4.0{\mu}m$). However, in several parasitology textbooks, the length of T. vaginalis is said to vary widely from 7 to $32{\mu}m$, and its undulating membrane is said to extend about half way (53.5%) to the posterior end of the body. On the other hand, in our study, the undulating membrane was observed to extend more than 3/4 of the body length (72.1%) in old T, whereas in fresh T it could not be measured. Taken together, we suggest that T. vaginalis averages 26 (21-32) ${\mu}m$ in total length, with 9.5 (7.4-11.4) ${\mu}m$ of body length and 6.8 (5.3-7.7) ${\mu}m$ of width, and its undulating membrane extending 3/4 of its body length. Therefore, these findings may provide useful information for morphological characteristics of T. vaginalis.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.11-12
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• 2002

Accidental overexposures by radiotherapy have gathered attention recently in Japan. The widely publicized accidents have occurred at the government official benefit society hospital and at the hospital affiliated to a medical school. The accident at the government official benefit society hospital occurred when one of two existing accelerators was renewed. A radiotherapy planning system was also introduced at that time. Then treatment planning for the old and the new linear accelerator was performed using the system. There were variations in wedge factors for the 30 degrees wedge filter between the old and the new linear accelerator. That is, the difference in the structure of the wedge filter (30 degrees) resulted in variations of the wedge factors between both accelerators. In order to keep strength, a lead board was backed to the lead wedge filter for the new linear accelerator, whereas the wedge filter for the old one was made of the iron. The X-ray attenuation of the iron wedge filter is smaller than that of the lead wedge filter. The basic beam data of the old linear accelerator, however, wasn't delivered properly between the user and the maker. Then, the accident took place because the same wedge factor was used for the old and the new linear accelerator. On the other hand, the accident which occurred at the university hospital was brought about by the input mistake in initialization of the computer system when a linear accelerator was introduced. The input mistake was found when the software of the system was updated. If the dose had been measured and confirmed adequately, the accidents could have been prevented in both cases.

• Korean journal of food and cookery science
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• v.4 no.1
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• pp.17-26
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• 1988

The polysaccharide produced by pseudomonas elodea, Gellan gum, was rheologically characterized, compared with agar. Rheological properties were determined from the change in the value of intrinsic viscosity with the pH and salt concentration. At the range of pH 2∼ll and salt 0∼0.16M KC1, the intrinsic viscosity of Gellan gum ranged from 8.8 to 21.2dl/g and agar ranged from 1.97 to 11.46d1/g. In the absence of salt, the intrinsic viscosity of Gellan gum increased as the pH of solution increased up to neutral pH then decreased slightly at alkaline pH, whearas the intrinsic viscosity of agar increased as the pH of solution increased up to pH 9 then decreased slightly. Intrinsic viscosity of Gellan gum and agar decreased with an increase in salt concentration. The chain stiffness parameter for the Gellan gum was 0.033. The overlap parameter of Gellan gum and agar were 0.047g/dl and 0.087g/dl, respectively. Gellan gum and agar were shear rate dependent or pseudoplastic. The yield stress and proportionality constant of Gellan gum increased slightly as the concentration increase, on the other hand, the shear index of Gellan gum showed a maximum at 0.75g/dl and gradually decreased as the concentration increase. The apparent viscosity of Gellan gum and agar decreased as the temperature increase. A lower concentration of the divalent cations calcium and magnesium is required to obtain maximum gel strength than for the monovalent cations sodium and potassium.