• 한국재료학회지
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• 제12권1호
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• pp.10-15
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• 2002

Melt blends of maleic anhydride grafted polypropylerle(PP-g-MA) and Nylon 6 were prepared to study the influence of chemical reaction between the two polymer components. By adding the MA grafted polystyrene pold (ethylene/butadiene) and polystyrene[SEBS-g-MA] as the compatible modifiers to reinforce the impact resistance, the Izod impact strength, high rate impact strength and morphology were studied. The notched Izod impact strength increased with the content of PP-g-MA and SEBS- g-MA. The energy of high rate impact strength increased as the thickness of specimen increased, while, it increased as the specimen displacement decreased. In the morphology observed by SEM, finally, we confirmed the improvement of the compatibilization and interfacial adhesion with the content of SEBS-g-MA. The continuous phase of PP-g-MA was the main cause of the modified properties.

• 한국운동역학회지
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• 제12권1호
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• pp.115-124
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• 2002

The purpose of this study is to analyze the ground reaction force of arm landing on arm and leg during sports aerobics. Subjects of this study were total 10 players of 5 males and 5 females who have are domain sports aerobics medalists more than the third place in national tournaments. The subjects jumped between the two ground reaction force analyzers, while landing their right hand on the front platform(#1) and their right leg on the rear platform(#2), and the data frequency was set to 200Hz. Findings of this study are as follows; More than 3 times of impact peak force of vertical reaction force acted on arm joint than on leg joint. And, when ground reaction force on foot increased, ground reaction force on hand decreased. 3 impact peaks of curve of ground reaction force were found - Impact Peak 1 incurred on the time the palm lands on the ground, Impact Peak 2 absorbing shock secondarily on wrist joint, and Active Peak incurred on the time of holding the weight while pushing out the severly bent elbow joint.

• 대한기계학회논문집A
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• 제26권12호
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• pp.2656-2661
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• 2002

Multiple impact models to examine the effect of stress interference are proposed and investigated. The single shot model analysis, which used various shot ball conditions, was carried out to compare with multiple impacts analysis. Then the multiple impact analysis were performed to predict the effect of the shot ball distances. The results showed that the stress interference in the multiple impact model significantly reduced the maximum value of the compressive residual stresses. The residual stress profiles were strongly effected by the shot ball distances. The multiple impact model can simulate a realistic shot peening process rather than a single shot model does. It is concluded that the proposed model predicts the real process more accurately.

• 한국소음진동공학회논문집
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• 제12권8호
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• pp.573-580
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• 2002

Generally the ceiling frame of apartment house is made of wood. But the wood frame has several problems due to the natural properties such as distortion by shrink, low fire resistance and material loss in the construction field. And it has some defections in sound insulation performance. Therefore it is necessary to develop a new method that can be used as a ceiling frame. This study aims to analyze and to compare the sound insulation characteristics against the floor impact sound between wood ceiling frame and M-bar frame which is made of steel. The results of this study are like these. M-bar frame is more effective than wood ceiling frame in sound insulation. And sound absorbing or sound insulation materials which can be Put on gypsum board are helpful to improve floor impact sound insulation performance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.372.1-372
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• 2002

Although impact hammer is widely used as a convenient excitation tool in structural modal testing, little is known about the dynamic charateristics of its impulse mechanism. Transmission of the impulsive force to the structure depends on the dynamic properties of the impact hammer as well as the stiffness of the tip. An improved dynamic model of the impact hammer is proposed in this study with numerical simulations based on this model. (omitted)

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.262-267
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• 2002

Impact behavior of polycarbonate in various defect state was investigated using an instrumented impact fester. A mettled of analyzing raw impact data was developed and successfully demonstrated the impact behavior in terms of load-displacement and energy-displacement curves. This technique was shown to be capable of separating defect, no-defect initiated fractures as well as their propagation behaviors.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
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• pp.85-85
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• 2003

We examined the hypothesis that the crater formation rate exhibits periodicity, employing data sets of Grieve (1991), Moon et al. (2001), and the Earth Impact Database (2002; DB02). DB02 is known to supercede previous compilations in terms of its accuracy and precision of the ages; it is the first time that this database has been used for periodicity analysis. For data sets comprising impact structures with D$\geq$5km (and also those with $\geq$20km), there is no convincing evidence for periodicities in the crater ages, according to our Fourier analysis. However, we detected two peaks at 16.1Myr and 34.7Myr for craters with D$\geq$30km; we confirm that the age distribution of impact craters with D$\geq$45km has dominant power at 16.1Myr. Thus, we may conjecture a probable periodic shower of Earth impactors with sizes d$\geq$1.5km. In addition, we found that the selection of data sets, the lower limits on the ages and diameters of impact craters, as well as the accuracy and precision of the ages, all constitute crucial factors in reconstructing the impact cratering history of the Earth.

• 한국디자인학회:학술대회논문집
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• 한국디자인학회 2002년도 봄 학술발표회 논문집
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• pp.24-25
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• 2002

• 대한기계학회논문집A
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• 제26권4호
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• pp.787-793
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• 2002

In this study, a bar impact test of low velocity was carried out to gain an insight into the damage mechanism and sequence induced in alumina plates(AD 85 and AD 90) under impact conditions. An experimental setup utilizing an instrumented long bar impact was devised, that can measure directly the impact force applied to the specimen and supply a compressive contact pressure to the specimen. During the bar impact testing, the influences of the contact pressure applied along the impact direction to the specimen on the fracture behavior were investigated. The measured impact force profiles explained well the damage behavior induced in alumina plates. The higher contact pressure to the specimen led to the less damage due to the suppression of radial cracks due to the increase in the apparent flexural stiffness of plate. It had produced the change of damage pattern developed in the specimen; from the radial cracks to the local contact stress dominant damage. It would contribute to the improvement of the ballistic property in ceramic plates. The observed results showed the following sequence in damage developed: The development of cone crack at impact region, the formation of radial cracks from the rear surface of plate depending on the plate thickness, the occurrence of crushing within the cone envelope and the fragmentation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.865-868
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• 2002

This study investigated the shape deformation of ball projectile(5.56mn) under the low energy impact by the use of the drop weight impact tester. ball projectile(5.56mm) consisted of the copper face with a lead core. The impact conditions were changed with the variations of the mass and the drop height of the impact tup. Shape deformation of ball projectile(5.56mm) after low velocity impact was measured using a video microscope and CCD camera. The test result showed that impact energy by changing of drop height of the impact tup affected shape deformation of ball projectile(5.56mm). So, it is important to study the relativity between shape deformation of ball projectile(5.56mm) and ballistic protection of plate(such as hybrid composite laminates) under the high velocity impact.