• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.1
• /
• pp.117-123
• /
• 1998

We investigated the effect of mechanical backside damage in Czochralski grown silicon wafer. The intensity of mechanical damage was evaluated by minority carrier recombination lifetime by laser excitation/microwave reflection photoconductivity decay method, photo-acoustic displacement method, X-ray section topography, and wet oxidation/preferential etching methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the photo-acoustic displacement values increased proportionally, and it was at Grade 1: Grade 2:Grade 3 = 1:19.6:41 that the normalized relative quantization ratio of excess photo-acoustic displacement in damaged wafer was calculated, which are normalized to the excess PAD from sample Grade 1.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.4
• /
• pp.581-586
• /
• 1998

We investigated the effect of mechanical back side damage in Czochralski grown silicon wafer. The intensity of mechanical damage was evaluated by minority carrier recombination lifetime by laser excitation/microwave reflection photoconductivity decay method, degree of X-ray diffuse scattering, X-ray section topography, and wet oxidation/preferential etching methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the magnitude of diffuse scattering and X-ray excess intensity increased proportionally, and it was at Grade 1:Grade 2:Grade 3=1:7:18.4 that the normalized relative quantization ratio of excess intensity in damaged wafer was calculated, which are normalized to the excess intensity from sample Grade 1.

• Korean Journal of Agricultural Science
• /
• v.31 no.2
• /
• pp.87-96
• /
• 2004

This study concentrates on the trail of the CNU(Chungnam National University) forest. The amount of use and the pattern of damage are considered, as well as the extent of environmental damage. Finally, some managerial strategies are proposed in connection with sustainable maintenance. The trail of the university forest is composed of three sections; one is the neighborhood park and the Institute of Information Technology/Communications, the second is the Institute of Information Technology/Communications and the Dormitory, and the third section is the Dormitory and the Foreign prof's Apt. The total length of the trail is 2.6km. The daily amount of use is 1,269 visitors per day. The amount of using increased three times the amount of that in 1998. This study shows the pattern of damage of the trail in the order of root-exposure, widening, rock-exposure, deepening and the divergence in the frequency of occurrence of all these factors. Environmental damage is also graded thus: grade 3 is 27.4m, grade 4 is 0.8m, grade 5 is 1.5m, and grade 6 is 0.2m. Accordingly, some managerial strategies were proposed in connection with the sustainable trail maintenance.

• Computers and Concrete
• /
• v.4 no.3
• /
• pp.221-241
• /
• 2007

Based on the experiment results, the damage and fracture behavior of concrete at the ages of 1d, 2d, 7d and 28d, in three-point bending and uniaxial tensile tests, were simulated with a finite element program, ABAQUS. The critical stress intensity factor $K_{IC}^s$ and the critical crack tip opening displacement ($CTOD_C$) of concrete were calculated with effective-elastic crack approach for the three-point bending test of grade C30 concrete. Based on the crack band model, a bilinear strain-softening curve was derived to simulate the LOAD-CMOD curves and LOAD-Displacement curves. In numerical analysis of the uniaxial tension test of concrete of grade C40, the damage and fracture mechanics were combined. The smeared cracking model coupling with damaged variable was adopted to evaluate the onset and development of microcracking of uniaxial tensile specimen. The uniaxial tension test was simulated by invoking the damage plastic model which took both damage and plasticity as inner variables with user subroutines. All the numerical simulated results show good agreement with the experimental results.

• Journal of the Korean Institute of Gas
• /
• v.21 no.6
• /
• pp.8-14
• /
• 2017

One of the main causes of gas pipeline accidents is mechanical impact(third party damage). The majority of high pressure gas pipelines buried in major domestic industrial complexes are old pipes which have being operated over 20 years. Therefore, if an accident occurs, there will be a full scale accident because there is no additional inspection and reinforcement time. In this study, the defects on the piping during the mechanical impact were studied through the third party damage(excavation) experiments. Experiments were carried out using the 21 ton excavator which is operated in the actual excavation work and the type of pipe to be struck are ASTM A106 Grade.B and ASTM A53 Grade.B. As a result, when the bucket used during excavator operation is a sawtooth bucket, the defect is more bigger. And the smaller the diameter of the pipe, the smaller the depth and length of the defect. Also, it was confirmed that the impact height had no effect on the defects on the buried pipe, during the excavation work.

• Journal of Environmental Impact Assessment
• /
• v.15 no.6
• /
• pp.357-372
• /
• 2006

The excessive land activities in farming can cause soil erosion, inundation by a flood, and fallow. So far land evaluation has been analyzed using the land use limitation derived from the excessive land activities. This study was done for evaluating the agricultural fields by using 3 land use limitations, inundation potential, soil erodibility potential, and fallow potential. The study area is Ibang-myeon, Changnyeong-gun, Gyeongnam-province, Korea. A logistic regression model was applied to recognize the inundation potential by a flood in the Nakdong river basin. And potential soil erodibility index (PSEI) was derived from USLE model to analyze the soil erodibility potential. And a probability model from a logistic regression model was applied to detect the fallow potential. Therefore, we found 220.7ha for the 4th grade and 86.1ha for the 5th grade was analyzed as water damage potential. Large area near Nakdong river have problem to grow the rice due to the damage by water inundation. And 213.6ha for the 3rd grade and 103.3ha for 4th grade was detected as a result of the analysis of soil erosion potential. The soil erosion potential was high when within-field integrity of soil was not stable, or the kinetic energy was high or the slope length was long due to a steep slope of a specific land. And 869.1ha for 3rd grade, 174.9ha for 4th grade, and 110.6ha for 5th grade was detected to be distributed having the fallow potential. Especially, a village, having a steep mountain, had 249.5ha for the 3rd grade, which was 28.7% of total area showing the 3rd grade. Finally, Three villages, including An-ri, Geonam-ri, Songgok-ri, showed they had largest area of the suitable land in the study area. These villages had similar topographic condition where they were far from Nakdong river, and they had relatively higher elevation and flat lands.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.32 no.1
• /
• pp.33-46
• /
• 2004

This study is aimed to redesign established parks and to propose a series of devices protecting them from vandalism. To solve the problems, we ascertained the damaged areas of the park greens. The trace analysis was performed to grasp the transverse inside the parks of Jeonju and Iksan in Collabuldo. Then, we presented the basic plan for minimizing park damage and for remodeling the system of movement. The results of the study are summarized as follows: it is identified that the transverse phenomenon is considerably wide-spread in majority of parks, and has no relationship to the park area or the green area. It is considered that the $\ulcorner$Condition rating class$\lrcorner$ of grass damage, which is grade 6, is extraordinarily high and the damage is accumulated considerably. Also, the damage part of other grade is discovered equally, and when unattended, the acceleration of damage is positive. A damage width a 0.5∼1.5m makes up the greater part of 79.6%. It also constitutes most of a rectilinear form. The difference in the height between the original point and destination point is below 0.7m, which is above 70%. It is identified that the interrelationship between the damage continuation length and plan distance is relatively high by the simple regression: analysis and by Pearson' correlation analysis. In spite of the normal damage continuation length is 20m, the frequency degree is downward with extreme point at 10m. Accordingly, it is assumed that park users have physical and psychological pressure when they cross the lawn field. Damage types are classified as the Simple cut cross type, the Behavioral facilitates type, Access advantage type and the Strolling type through type classification. It is considered that this classification is effective when identifying short pass type on lawn field according to the damage length and intensity.

• Smart Structures and Systems
• /
• v.25 no.5
• /
• pp.531-541
• /
• 2020

This paper demonstrates the possibility of evaluating the safety of a building right after an earthquake using consumer-grade surveillance cameras installed in the building. Two cameras are used in each story to extract the time history of interstory drift during the earthquake based on camera calibration, stereo triangulation, and image template matching techniques. The interstory drift of several markers on the rigid floor are used to estimate the motion of the geometric center using the least square approach, then the horizontal interstory drift of any location on the floor can be estimated. A shaking table collapse test of a steel building was conducted to verify the proposed approach. The results indicate that the accuracy of the interstory drift measured by the cameras is high enough to estimate the damage state of the building based on the fragility curve of the interstory drift ratio. On the other hand, the interstory drift measured by an accelerometer tends to underestimate the damage state when residual interstory drift occurs because the low frequency content of the displacement signal is eliminated when high-pass filtering is employed for baseline correction.

• Restorative Dentistry and Endodontics
• /
• v.45 no.4
• /
• pp.55.1-55.12
• /
• 2020

Objectives: This study investigated the effects of physically damaged and resin-contaminated tips on radiant emittance, comparing them with new undamaged, non-contaminated tips using 3 pieces of spectrophotometric laboratory equipment. Materials and Methods: Nine tips with damage and/or resin contaminants from actual clinical situations were compared with a new tip without damage or contamination (control group). The radiant emittance was recorded using 3 spectrophotometric methods: a laboratory-grade thermopile, a laboratory-grade integrating sphere, and a portable light collector (checkMARC). Results: A significant difference between the laboratory-grade thermopile and the laboratory-grade integrating sphere was found when the radiant emittance values of the control or damaged/contaminated tips were investigated (p < 0.05), but both methods were comparable to checkMARC (p > 0.05). Regardless of the method used to quantify the light output, the mean radiant emittance values of the damaged/contaminated tips were significantly lower than those of the control (p < 0.05). The beam profile of the damaged/contaminated tips was less homogeneous than that of the control. Conclusions: Damaged/contaminated tips can reduce the radiant emittance output and the homogeneity of the beam, which may affect the energy delivered to composite restorations. The checkMARC spectrophotometer device can be used in dental offices, as it provided values close to those produced by a laboratory-grade integrated sphere spectrophotometer. Dentists should assess the radiant emittance of their light-curing units to ensure optimal curing in photoactivated, resin-based materials.

• Korean Journal of Materials Research
• /
• v.14 no.1
• /
• pp.78-82
• /
• 2004

In this study, the degree of creep damages on the weldment accelerated creep degradation was nondestructively evaluated by replica method. The frequency of creep cavities occurrence has been observed highly at the intercritical HAZ. The life fraction of weldment damaged by creep has shown from 0.25(damage grade: 2) to 0.75(damage grade: 4) when it reptured. The degree of creep damages is considered to be evaluated by the metallographic replica method which is one of nondestructive evaluation methods.