• 한국세라믹학회지
• /
• 제33권7호
• /
• pp.809-815
• /
• 1996

When Li2O.2SiO2 glass was crystallized between the temperature of maximum nucleation and the temperature of maximum crystal growth it was found that the control of heating rate had serious effect on the crystallinity and microstructure and the greatly changed physical properties. Density and elastic modulus tends to increase but thermal expansion coefficient decreased with increased crystallinity. When heating rate between the tempe-rature of maximum nucleation and the temperature of maximum crystal growth was 10~5$0^{\circ}C$/hr. crystallinity was increased to result in the increment of strength. When nuclation was done at 44$0^{\circ}C$ for 5 hours and the temperature of crystal growth was held at 575$^{\circ}C$ strength was increased until crystallinity reached 65% and strength was decreased with higher crystallinity. These phenomena could be explained that even for the same crystallinity different heat rates resulted in different number and size of cracks.

• 한국주조공학회지
• /
• 제3권4호
• /
• pp.256-261
• /
• 1983

In this study, the variations of tensile strength and yield strength of Al-20% Si alloy were studied. Copper, magnesium and nickel as alloying elements added from 1% to 3% respectively. The temperature range was from room temperature to $350^{\circ}C$. The refinement of primary silicon crystal was treated with phosphorous addition. The results obtained are as follows: 1. Tensile strnegth and yield strength showed more increased strength in refining treated alloy than that of in nonrefining alloy at elevated temperature. 2. Tensile strength and yield strength were increased with the contents of copper. Tensile strength showed the maximum at $150^{\circ}C$, but yield strength was decreased with increasing temperature. 3. The effect of magnesium addition on tensile strength and yield strength showed the maximum at 1% addition and $150^{\circ}C$. 4. Tensile strength and yield strength showed a slight increase with the content changes of nickel and they were decreased with increasing temperature.

• 대한관절경학회지
• /
• 제2권1호
• /
• pp.85-92
• /
• 1998

Various methods for fixation of graft have been widely used for reconstruction of anterior cruciate ligament. However, the biomechanical strength of each fixation techniques are not fully understood. The purpose of this study is to compare the pull out strength of different fixation techniques which is probably the most important factor for the success at the initial stage of healing. Biomechanical test was carried out to measure and compare the pull out tensile strength of five different fixation techniques in 35 pig(Yorkshire) knees. ANOVA and Duncan multiple comparison test was applied for statistical analysis. In the two fixation techniques with bone patellar tendon bone graft, the mean maximum tensile strength was $1333.4{\pm}148.5N$ with titanium interference screw, while it was $1310.1{\pm}168.9N$ with biodegradable interference screw. The failure mode were pulled out of bone plugs from the femoral tunnel in majority cases. In the fixations with hamstring tendon, the mean maximum tensile strength were $1405.9{\pm}135.1N$ with SemiFix screw, $820.3{\pm}104.5N$ with biodegradable interference screw, and $682.1{\pm}54.2N$ with Endobutton. The mode of failure was variable in each technique. The tendon was pulled out from the tunnel in biodegradable interference screw fixation, the screw was bent in the SemiFix system, and the polyester tape were ruptured or the buttons were pulled into tunnel in Endobutton fixation. The mean maximum tensile strength of two interference screws with bone patellar tendon bone was statistically comparable to that of SemiFix with hamstring tendon. However biodegradable interference screw and Endobutton with hamstring tendon showed weaker maximum tensile strength than above three fixation techniques (P<0.05).

• Journal of Magnetics
• /
• 제21권1호
• /
• pp.115-124
• /
• 2016

The present study analyzes T1 TSE and T1 slice sel. IR (dark_fluid) signal strength according to the degree of gadolinium contrast agent dilution and analyzes the turbo factors with regard to changes in the maximum and overall signal strength to study correlations between changes and signal-to-noise ratios (SNRs) and compare peak-to-peak SNR (PSNR) enhancement in order to improve the quality of T1-weighted images. Enhancement TR (600 msec) evaluated to determine the T1 TSE turbo factor and obtain the maximum signal strength, T1WI were used sequentially to experiment with turbo factors_1-4. T1 slice sel. IR (dark-fluid) was used to sequentially test turbo factors_2-5 but not turbo factor_1 at a TR (1500 msec) and compare data at an increase in T1 of 900 msec. The T1 TSE was reduced according to the contrast agent concentration. Phantom signal strength increased, whereas turbo factors_1-4 exhibited maximum signal strength at a concentration of 3 mmol, followed by a gradual decrease. In the turbo factors_2-5, the signal strength increased sharply to maximum signal strength at 0.7 mmol, followed by a reduction. T1 TSE had a greater maximum signal strength than did T1 slice sel. IR (dark_fluid). A comparison of SNR found that T1 TSE imaging was superior (33.3 dB) in turbo factor_1 and T1 slice sel. IR (dark_fluid) was highest (33.9 dB) at turbo factor_5. A PSNR comparison analysis was not sufficient to distinguish between the images obtained with both techniques at 30 dB or higher under all experimental conditions.

• 한국강구조학회 논문집
• /
• 제14권6호
• /
• pp.823-834
• /
• 2002

Steel-Concrete Column은 H형강의 플랜지 사이에 후프를 용접하고 플랜지 사이의 공간에 콘크리트가 채워진 새로운 합성기둥이다. 본 연구에서는 이 새로운 합성 기둥의 구조성능을 평가하기 위하여 단주압축, 휨, 전단실험을 수행하였다. 각 실험별 실험체들을 순철골 실험체와 철골 콘크리트 실험체로 구성하여 Steel-Concrete Column을 구성하는 철골, 내부 콘크리트, 후프의 내력기여도를 평가할 수 있도록 하였다. 실험결과 Steel-Concrete Column은 $\ulcorner$강구조 한계상태 설계 기준$\lrcorner$ 에 의해 계산된 내력값을 충분히 만족하여 구조부재에 적용 가능하다고 판단된다.

• 한국염색가공학회지
• /
• 제9권5호
• /
• pp.1-9
• /
• 1997

In the single yarn spinning process by the ring spinning system, the finer the fineness of yarn and the lower the twist coefficient, the lower the breaking strength and breaking elongation. The change of yarn specific volume to yarn number agreed with Peirce's formula in the range of Ne 50 to 70, but above that range the values of the experiment are higher than that of the formula. The change of diameter of yarn to the reciprocal of the square root of yarn number agreed with Peirce's formula in the range of under 0.14, but above that value the values of the experiment are higher than that of the formula. In breaking strength variation according to twist constant of single yarn, as the twist coefficient increased, breaking strength increased. At 5.8∼6.0 of twist coefficient the maximum breaking strength was shown, but above that value breaking strength decreased. Breaking elongation also showed a similar tendency. But at 6.0∼6.5 of twist coefficient the maximum breaking elongation was shown. Also spinning tension increased as twist coefficient increased. Twist coefficient, breaking strength and breaking elongation according to the number of coils stayed almost the same. Yarn spinning tension according to the number of coils at the maximum of diameter was the lowest value. The speed of the traveller at the maximum of diameter was the highest value.

• 한국공작기계학회논문집
• /
• 제16권6호
• /
• pp.29-36
• /
• 2007

The present study examined the mechanical properties of the friction welding of Ni-Cr-Mo to SM45C. Friction welding was conducted at welding conditions of 2,000 rpm, friction pressure of 100MPa, friction time of 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0 seconds, upset pressure of 150MPa, and upset time of 3.0 seconds. When the friction time was 1.6 seconds, the maximum tensile strength of the friction weld happened to be 1,020MPa, which is 120% of the base material's tensile strength(850MPa). At the same condition, the maximum shear strength was 438MPa, which is equivalent to 103% of the base material's shear strength(425MPa). At the same condition, the maximum vickers hardness was Hv490 at Ni-Cr-Mo nearby weld interface, which is higher Hv40 than condition of the friction time 0.8 seconds, and the maximum vickers hardness was Hv305 from weld interface of SM45C, which is higher Hv12 than condition of the friction time 0.8 seconds. The results of microstructure analysis show that the structures of two base materials have fined and rearranged along a column due to heating and axial force during friction, which has affected in raising hardness and tensile strength.

• Environmental Engineering Research
• /
• 제11권5호
• /
• pp.257-265
• /
• 2006

The purpose of research is to mix the fly ash from municipal solid waste incinerator in the recycled Polypropylene and to recycle. The specimen was produced by mixing 20 wt.% of MSWI fly ash at maximum in the recycled Polypropylene and the particle size analyzer, DSC, TGA, SEM and UTM instruments were used to analyze the physical chemical properties of the specimen. As a result of measurement, the average particle size of MSWI fly ash was $18.08\;{\mu}m$. In TGA analysis, the temperature of specimen S-5 at 50% of weight decrease was risen by $7^{\circ}C$ higher than specimen S-1. In UTM measurement, specimen S-2 showed the maximum strength for tensile strength and specimen S-3 showed the maximum strength for flexural strength. But, impact strength was decreased according to the increasing proportion of MSWI fly ash. In conclusion, when the proper amount of MSWI fly ash was added to the recycled Polypropylene, thermal endurance, tensile strength and flexural strength could be increased, but impact strength was decreased.

• 한국방재학회 논문집
• /
• 제5권4호
• /
• pp.29-36
• /
• 2005

본 연구는 부산 가덕도 부근 해성점토에 대하여 일축압축시험을 실시하여 일축압축강도, 최대강도에서의 변형률, 심도와의 관계를 비교 및 분석하였으며 시료에 포함되어 있는 불순물과 시료채취시 충진율이 흙의 일축압축강도와 교란도에 미치는 영향을 파악하였다. 시험결과 시료의 일축압축강도는 최대강도에서의 변형률이 증가함에 따라 감소하는 결과를 보였으며 채취 심도가 깊을수록, 시료채취시의 충진율이 좋을수록 증가하는 추세를 보였다. 특히 시료 충진율의 증가는 일축압축강도 증가를 가져왔고 시료의 등급 또한 높여주었다.

• PNF and Movement
• /
• 제19권1호
• /
• pp.105-113
• /
• 2021

Purpose: The purpose of this study was to investigate the effect of trunk-stabilization training using stabilizing reversal and rhythmic stabilization techniques of PNF on trunk muscle strength and respiratory function in elderly stroke patients. Methods: There were 26 stroke patients included in the study. Patients were divided into two groups, and all patients performed exercise 30 min five times per week for six weeks. The experimental group performed trunk stability exercise using stabilizing reversal and rhythmic stabilization techniques of PNF, and the control group performed flexibility and strength training. Trunk muscle strength, forced vital capacity, maximum inspiratory pressure, and maximum expiration pressure were measured to determine the changes after the intervention. For statistical processing, a paired t-test was performed within the group, and the value after intervention was performed as an independent t-test to find out the difference between the two groups. Results: In the experimental group, all of the trunk muscle strength, forced vital capacity, maximum inspiratory pressure, and maximum expiration pressure showed significant differences according to the intervention. In the control group, there were statistically significant differences in trunk muscle strength and forced vital capacity, but the maximum inspiratory pressure and the maximum expiration pressure did not show any statistical change. Conclusion: From these results, it can be seen that the trunk stability exercises that use the proprioceptive neuromuscular promotion method of stable reversal and rhythm stabilization can be a good intervention for the respiratory function of stroke patients.