• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 가을 학술발표회 논문집
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• pp.117-122
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• 1990

This is the study on the feature of workability and engineering properties of flowing concrete using the superplasticizing agents which is using to effect considerable reductions in water contents in the same level of consistemcy and workability. It is the aim of this study to compare workabili쇼 and engineering properties of flowing concrete according to the addition time and method of superplasticizing agents. In this experimental study, 2cm slump of concrete, 18cm slump of conventional concrete, two kinds of aggregates and addition time and method of superplasticizing agents of 0, 15, 30, 45, 60 and 90 minutes were included to analyze and investigate the workability and engineering properties of flowing concrete.

• Elastomers and Composites
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• 제39권4호
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• pp.263-273
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• 2004

The effects of zinc surfactant (ZB) on the bis(triethoxysilylpropyl)disulfide (TESPD)-silica mixture in natural rubber (NR) and solution butadiene-co-styrene rubber(S-SBR) were compared with respect to their rheological property, processability, physical properties, and silica dispersion. In the NR compound, addition of the ZB increased the reversion resistance time (T-2), the tensile modulus, and the BO time; however, lowered the viscosity, the HBU, and tans values. In the S-SBR copound, addition of the ZB increased the $tan{\delta}$ values while lowered the T-2, the tensile modulus the BO time, the viscosity, and the HBU of the compound. In the NR compounds, addition of the ZB significantly increased the processability and mechanical property. However, in the S-SBR compounds, it improved the processability the mechanical property was not improved.

• 한국소음진동공학회논문집
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• 제25권4호
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• pp.291-298
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• 2015

In this study, the reverberation time of apartment living room was measured and distribution of the reverberation time was analyzed. In addition, sound field characteristics of mock-up test room similar with living room and timber structured bedroom was investigated with addition of furniture and sound absorption material. Average reverberation time of unfurnished apartment unit was 1.11 s, and reverberation time in 630 Hz~2000 Hz bands were longer than 1.2 s. It was found that from the field measurement results, reverberation time characteristic of furnished apartment living room was uniform in most of frequency bands. Averaged reverberation time of furnished living room was 0.48 s and the reverberation time of bedroom was 0.44 s. Standardized sound pressure level correction values were calculated from the average reverberation time of furnished and unfurnished apartment units. The correction value of unfurnished living room was −3.4 dB and that of furnished living room was 0.2 dB. Measured reverberation time of furnished and unfurnished apartment units indicated that reference reverberation time; 0.5 s, in KS and ISO standards is reasonable also in Korean residential environment.

• Structural Engineering and Mechanics
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• 제82권4호
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• pp.445-458
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• 2022

Some of the control systems used in engineering structures that use sensors and decision systems have some time delay reducing efficiency of the control system or even might make it unstable. In this research, in addition to considering the effect of the time delay in vibration control process, predictive control is used to compensate the time delay. A semi-active vibration control approach with the help of magneto-rheological dampers is implemented. In addition to using fuzzy inference system to determine the appropriate control voltage for MR damper, structural behavior prediction system and specifying future responses are also used such that the time delays occurring within control process are overcome. For this purpose, determination of prediction horizon is conducted for one, five, and ten steps ahead for single degree of freedom structures with periods ranging from 0.1 to 4 seconds, subjected to twenty earthquake excitations. The amount of time delay applied to the control system is 0.1 seconds. The obtained results indicate that for 0.1 second time delay, average prediction error values compared to the case without time delay is 3.47 percent. Having 0.1 second time delay in a semi-active control system reduces its efficiency by 11.46 percent; while after providing the control system with structure behavior prediction, the difference in the results for the control system without time delay is just 1.35 percent on average; indicating a 10.11 percent performance improvement for the control system.

• 한국식품영양학회지
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• 제21권4호
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• pp.436-442
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• 2008

Buckwheat leaves and young parts of the plant are consumed as a vegetable in certain countries. The quality characteristics of Sulgidduk withadded buckwheat vegetable powder(BVP)(0, 0.2, 0.5, 1.0, 1.5% w/w) were assessed in this study. Weobtained the following results: The water contents of Sulgidduk on the first day evidenced no differences according to the ratio of BVP addition, whereas the water contents of Sulgidduk decreased with increasing storage time and increasing amounts of added BVP. As the amount of BVP increased, both the L value(Lightness) and the a value(Redness) decreased, whereas the b value(Yellowness) increased. In terms of the mechanical texture characteristics, the hardness of the Sulgidduk increased with addition of both 0% and 0.5% BVP, with increases in storage time. The springiness of Sulgidduk was reduced as the quantities of BVP increased. We detected no significant differences in the chewiness of Sulgidduk according to the ratio of BVP addition. Also, the chewiness of Sulgidduk increased with BVP additions of 0% and 0.2% with increases in storage time, whereas no differences were detected in the group to which 0.5% BVP was added. The cohesiveness of the Sulgidduk decreased with increases in BVP and storage time. In our sensory evaluation of the color and flavor characteristics, the optimal quality was reported in conjunction with the Sulgidduk to which 1.0% and 1.5% BVP was added(p<0.05), whereas we noted no significant differences in texture and taste(sweetness) according to the ratio of BVP addition. Sulgidduk with 1% of BVP evidenced the best characteristics in our overall sensory evaluation.

• Metals and materials international
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• 제24권6호
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• pp.1202-1212
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• 2018

The effects of Nickle (Ni) addition on bainitic transformation and property of ultrahigh strength bainitic steels are investigated by three austempering processes. The results indicate that Ni addition hinders the isothermal bainite transformation kinetics, and decreases the volume fraction of bainite due to the decrease of chemical driving force for nucleation and growth of bainite transformation. Moreover, the product of tensile strength and total elongation (PSE) of high carbon bainitic steels decreases with Ni addition at higher austempering temperatures (220 and $250^{\circ}C$), while it shows no significant difference at lower austempering temperature ($200^{\circ}C$). For the same steel (Ni-free or Ni-added steel), the amounts of bainite and RA firstly increase and then decrease with the increase of the austempering temperature, resulting in the highest PSE in the sample austempered at temperature of $220^{\circ}C$. In addition, the effects of austempering time on bainite amount and property of high carbon bainitic steels are also analyzed. It indicates that in a given transformation time range of 30 h, more volume of bainite and better mechanical property in high carbon bainitic steels can be obtained by increasing the isothermal transformation time.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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• pp.185-190
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• 1998

Corrosion of steel reinforcement is the most significant factor of deterioration in reinforced concrete structures. Chloride ion is considered one of the most common culprits on the corrosion of steels in concrete. The main objective of this study is understanding behavior of chloride ion in hardened cement pastes at different stages of curing. Cement pastes with water-cement ratio of 0.5 are allowed to hydrate in sealed containers for 28, 70, 180 days. And than pore solution is expressed. It was found that the $Cl^-$ concentrations in pore solution is decreased with increasing curing time in all Nacl addition level, the $OH^-$ concentrations is increased to 70 days but decrease at 180 days in all Nacl addition level. The $Cl^-$/$OH^-$ in pore solution is increased with increasing curing time in all Nacl addition level, however $Cl^-$/$OH^-$ of maximum Nacl addition level(Nacl 0.54% by weight of cement) is under the onset of depassivation level 0.3.

• 전자공학회논문지C
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• 제34C권11호
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• pp.47-55
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• 1997

In general, processing flow of the conventional floating-point multiplication consists of either multiplication, addition, normalization, and rounding stage of the conventional floating-point multiplier requries a high speed adder for increment, increasing the overall execution time and occuping a large amount of chip area. A floating-point multiplier performing addition and IEEE rounding in parallel is designed by using the carry select addder used in the addition stage and optimizing the operational flow based on the charcteristics of floating point multiplication operation. A hardware model for the floating point multiplier is proposed and its operational model is algebraically analyzed in this paper. The proposed floating point multiplier does not require and additional execution time nor any high spped adder for rounding operation. Thus, performance improvement and cost-effective design can be achieved by this suggested approach.

• 한국주조공학회지
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• 제17권6호
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• pp.608-614
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• 1997

The effect of mold preheating temperature on the microstructure such as grain size, eutectic silicon morphology was investigated for the Al-7wt%Si-0.3wt%Mg alloy. Microstructural variations have been characterized as a function of Sr addition and cooling rate during solidification. Microstructures were correlated with cooling rate, local solidification time and eutectic nucleation temperature, etc. In this study, Sr addition caused increase of local solidification time, undercooling and reduction of eutectic plateau temperature. In logarithmic scale, local solidification time was in inverse proportion to cooling rate. Eutectic nucleation temperature was in inverse proportion to cooling rate of logarithmic scale. Increasing the cooling rate refined dendrite arm spacing and eutectic silicon. Dendrite arm spacing was logarithmically in inverse proportion to cooling rate. Without modifier addition, eutectic silicon was modified at cooling rate of $7^{\circ}C/s$ or higher.

• Elastomers and Composites
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• 제43권4호
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• pp.281-287
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• 2008

고체상태 $^{13}C$ NMR을 이용하여 폴리부타디엔 고무(BR) 가황체의 정성 및 정량분석을 행하였다. TBBS로 촉진된 기존의 충진 BR 가황체에서는 올레핀성 이중결합에의 부가반응과 이중결합 옆의 $\alpha$ 위치에서의 치환반응이 동시에 일어났다. 또한 반응 초기에는 이중결합 옆의 $\alpha$ 위치에서의 치환반응은 이중결합에의 부가반응보다 빠르게 진행되었다. 한편 과가류(overcure) 시간 동안 이중결합-부가 폴리설파이드 구조는 5각형 및 6각형 고리 구조로 변형되는 것으로 추정되었다. 이러한 사슬 변형은 과가류 시간에 발생하는 화학적 가교 밀도와 상관되었다.