• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.2
• /
• pp.35-42
• /
• 2000

In recent years the recording density of hard disks has increased significantly largely due to the decreasing flying height. As a result of decreased flying height, the reliability issue become more critical. In this work the relationship between hard disk surface damage and data loss was investigated by using an actual hard disk drive. The purpose of this research was to identify the key factor which leads to data loss. It was shown that data loss is directly related to the physical damage of the Co-magnetic layer and there was no data loss when only carbon protective coating was damaged by the diamond tip.

• Journal of Environmental Science International
• /
• v.25 no.7
• /
• pp.989-998
• /
• 2016

In this study, we analyzed the content and compensation factors of 337 cases of national environmental disputes from five recent years (2000~2014). Causes of damage were noise-vibration in 234 cases (69%), sunlight in 48 cases (14%), air pollution in 19 cases (6%), water pollution in 15 cases (4%), odor in 13 cases (4%), and others factors in 8 cases (3%). Sources of damage were construction in 224 cases (66%), structures in 36 cases (11%), vehicle on road in 31 cases (9%), industry in 18 cases (5%), environmental facility in 11 cases (3%), livestock facility in 6 cases (2%), and other sources in 11 cases (3%). From the results of logistic regression analysis, important factors associated with compensation were found to be damage amount, damage distance, zoning districts, source, and administrative disposition.

• Journal of the Korean Society of Safety
• /
• v.17 no.1
• /
• pp.1-5
• /
• 2002

An approach for the damage of delamination which is the major concern during mechanical working for composite laminate material is proposed based on linear elastic fracture mechanics. This paper presents method evaluating of damage crack length using by average thrust force with AE characteristics. Also, the relations of AE characteristics are obtained from delamination damages. We found the onset ply of the delamination and a critical energy release rate and expressed a stress intensity factor by AEcount equation.

• Structural Engineering and Mechanics
• /
• v.19 no.1
• /
• pp.21-42
• /
• 2005

A method is presented to detect and assess the structural damage from changes in natural frequencies using Genetic Algorithm (GA). Using the natural frequencies of the structure, it is possible to formulate the inverse problem in optimization terms and then to utilize a solution procedure employing GA to assess the damages. The technique has been applied to a cantilever beam and a plane frame, each one with different damage scenario to study the efficiency of the developed algorithm. A laboratory tested data has been used to verify the proposed algorithm. The study indicates the potentiality of the developed code to solve a wide range of inverse identification problems in a systematic way. The outcomes show that this method can detect and estimate the amount of damages with satisfactory precision.

• Structural Engineering and Mechanics
• /
• v.24 no.1
• /
• pp.91-105
• /
• 2006

In this paper, post-earthquake capacity evaluation method of reinforced concrete buildings was studied. Substructure pseudo-dynamic test and static loading test of first story column in a four-story R/C building was carried out in order to investigate the validity of the evaluation method proposed in the Damage Assessment Guideline (JBDPA 2001). In pseudo-dynamic test, different levels of damage were induced in the specimens by pre-loading, and input levels of seismic motion, at which the specimens reached to the ultimate stage, were examined. From the experimental result, no significant difference in damage levels such as residual crack width between the specimens under static and pseudo-dynamic loading was found. It is shown that the seismic capacity reduction factors ${\eta}$ can provide a reasonable estimation of post-earthquake seismic capacity of R/C buildings suffered earthquakes.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.914-921
• /
• 2006

To describe the effect of the numerous and various oriented microcracks on the compressive and tensile concrete behaviors, the directional nonlocality is defined. The plasticity model using multiple failure criteria is developed for RC planar members in tension-compression. The crack damages are defined in the pre-determined reference orientations, and then the total crack damage is calculated by integrating multi-oriented crack damages. To describe the effect of directional nonlocality on the anisotropic tensile damage, based on the existing test results, the nonlocal damage factor is defined in each reference orientation. The reduced compressive strength in the cracked concrete is defined by the multi-oriented crack damages defined as excluding the tensile normal plastic strain from the compressive equivalent plastic strain. The proposed model is implemented to finite element analysis, and it is verified by comparisons with various existing panel test results.

• Toxicological Research
• /
• v.30 no.1
• /
• pp.45-48
• /
• 2014

Helicobacter pylori (H. pylori) is the most important factor of gastric disease in clinical practice. Moreover, smoking, stress and a poor diet may be additive factors for gastric damage. With these factors, increasing infection of H. pylori triggers gastritis, gastric ulcers and gastric cancer. To develop a new protective agent, we are concerned with plant-derived extract. The extract of Coptis chinensis (C. chinensis) and its constituents were investigated to assess their protective activities against gastric damage. The C. chinensis extract showed a scavenging effect against 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radicals, inhibition of H. pylori colonization and antiulcerogenic activities in rat. In particular, palmatine derived from C. chinensis was found to be the novel protective agent. It is better than the C. chinensis extract, berberine, a well-known constituent of C. chinensis. We suggest that palmatine from the root cortex of C. chinensis may be a good candidate for the development of new pharmaceuticals to prevent gastric disease.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.9 no.2
• /
• pp.209-218
• /
• 2017

Sea ice is the main factor affecting the safety of the Arctic engineering. However, traditional numerical methods derived from classical continuum mechanics have difficulties in resolving discontinuous problems like ice damage. In this paper, a non-local, meshfree numerical method called "peridynamics", which is based on integral form, was applied to simulate the interaction between level ice and a cylindrical, vertical, rigid structure at different velocities. Ice in the simulation was freshwater ice and simplified as elastic-brittle material with a linear elastic constitutive model and critical equivalent strain criterion for material failure in state-based peridynamics. The ice forces obtained from peridynamic simulation are in the same order as experimental data. Numerical visualization shows advantages of applying peridynamics on ice damage. To study the repetitive nature of ice force, damage zone lengths of crushing failure were computed and conclude that damage zone lengths are 0.15-0.2 times as ice thickness.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.43 no.5
• /
• pp.13-27
• /
• 2015

This study examined disaster risk from climate change in urban open spaces. This study conducted an assessment depending on type of damage and type of open space, subcategorizing it into flood damage and wind damage, flat park and mountainous park, and classified the assessment items by type into natural factor, artificial factor, and social factor for the purpose of analysis. Our major findings from this study are as follows: To look at the standardized score for the disaster risk from flood damages in the case of a flat park, Asian Park was higher at 55.800 point than Seoul Forest at 51.775 point, and in the case of mountainous parks, Dogok Park was at 58.428 point and Baebongsan Park was at 58.374 point. To look at the standardized score for disaster risk from wind damage, in the case of a flat park, Asian Park was higher at 64.763 point than Seoul Forest at 61.054 point, and in the case of mountainous parks, Baebongsan Park was higher at 58.533 point than Dogok Park at 55.459 point. This study raised a question about the necessity for and value of this disaster risk assessment in open space from damages caused by climate change, established an assessment model for disaster risk from damages in open spaces only to attempt risk assessment. Disaster risk of urban green space was enhanced.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.7
• /
• pp.77-86
• /
• 2007

Installation damage of 3 types of geogrids was evaluated with compaction condition by laboratory tester. This experimental was in accordance with ENV ISO 10722-1. First, soil distribution and water content were conducted. And then we changed cyclic loading time and type of geogrids as a factor of installation damage. The samples are woven, warp-knitted, welded type of 6, 8, 10T. This study aims to give an insight into the relationships between installation damage and cyclic loading time. The result of studies was that strength of the damaged geogrids can be closely correlated with the time of loading cycles. Especially, welded type shows slower slope than two types of geogrids due to coating materials. That means welded type is coated with PP (Polypropylene), but the other two types of geogrids are coated with PVC (Polyvinyl Chloride). To confirm another factor different method was performed. The size of soil was used between 9.5 mm and 23.5 m to compare initial experimental. Cyclic loading compaction is taken 200 times before installation test and the reason is that the reduction factor of this case by installation damage was higher than other compaction loading conditions.