• Journal of Korean Neurosurgical Society
• /
• v.61 no.2
• /
• pp.282-286
• /
• 2018

True extracranial carotid artery aneurysms (ECCAs) are uncommon. Atherosclerosis is the most common etiological factor. Neck pain, a pulsatile mass and murmur at auscultation are the most common symptoms. ECCAs may exhibit severe clinical manifestations due to complications. Cases of rupture can be fatal. There is a risk of distal embolization and stroke in thrombosed cases. We discuss two cases of enlarged ECCA treated surgically in the light of the most recent literature.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.281-284
• /
• 2004

The most important reason of using of ultra high strength concrete in super tall building is that ultra high strength concrete can reduce the section of members and control side sway effectively. However, the practical utilization of ultra high strength concrete is dependent not only on the production techniques, but also the overall preparation including proper code provisions, construction technique. The purpose of this study is to evaluate of mechanical properties of UHSC, such as modulus of elasticity, stress-strain behavior, modulus of rupture and tensile splitting strength. It is similar to normal or high strength concrete but necessary to discern the difference between normal or high strength concrete and ultra high strength concrete and modify existed equations. And in this study another important factor is to discern the difference according to member size, curing method in ultra high strength concrete experimentally.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.04a
• /
• pp.37-44
• /
• 1998

The objective of this study is development of high strength lightweight concrete and application or structural use. For this, mix proportions for each strength level were selected from lab tests, and adapted to producing ready-mixed concrete in batcher plant. It was very important to prewet the lightweight aggregates sufficiently for producibility and also workability. Splitting tensile strength of high-strength lightweight concrete produced has lower values than that of normal weight concrete, but modulus of rupture and modulus of elasticity are not less than normal weight concrete. The strength reduction factor ($\lambda$) for sand-lightweight concrete make higher than 0.85 present in structures using high-strength lightweight concrete. And it was showed that not parabola distribution but triangular distribution of stress in compression zone.

• Journal of KSNVE
• /
• v.9 no.2
• /
• pp.285-294
• /
• 1999

Transient analysis for compressible fluid flow has been performed experimentally and analytically to study the dynamic characteristics of the end volume transmission lines following a sudden pressure change a its entrance. The numerical method was developed based on the method of characteristics. The sudden pressure at its entrance was generated by rupture of diaphragm in a shock tube. The sudden pressure was used to obtain the response, as input signal for the numerical analysis. The response to the sudden pressure at the end volume was measured using a pressure transducer. The experimental result shows good agreements with the numerical result. The effects of tube length, its diameter and end volume magnitude are evaluated on the responses of the pressure and on the damping factor. It is found that the viscous damping effects on the response through the transmission pipeline becomes larger with increasing pi;eline length and decreasing diameter of the pipe and the fluid-elastic stiffness decreases with increasing the terminal volume. The numerical approach presented in this paper can be very useful in designing the instrument and control system.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.341-344
• /
• 2004

In the present research, slump, modulus of rupture (MOR) and flexural toughness $(I_{30})$ of high performance hybrid fiber reinforced concrete (HPHFRC) mixed with micro-fiber (carbon fiber) and macro-fiber (steel fiber) and replaced with silica fume were assessed with the analysis of variance (ANOVA). Steel fiber was a considerable significant factor in aspect of the response values of MOR and boo Based on the significance of factors related to response values from ANOVA, following assessments were available; Slump decrease: carbon fiber >> steel fiber > silica fume; MOR: steel fiber > silica fume > carbon fiber; $I_{30}$: steel fiber > carbon fiber > silica fume. Steel fiber $1.0\%$, carbon fiber $0.25\%$ and silica fume $5.0\%$, and Steel fiber $1.0\%$, carbon fiber $0.25\%$ and silica fume $2.5\%$ were obtained as the most optimum mixture.

• Proceedings of the KIEE Conference
• /
• 1994.07b
• /
• pp.1351-1353
• /
• 1994

High strengh pocelain insulators with 35wt% alumina were manufactured by wet produce technique. The microstructure and crystalline phases of this samples and the effect of CaO addition to insulator bodies were studied. Electrical and mechanical properties (permittivity, dissipation factor, modulus of rupture, Young's modulus etc,) were studied. The relation between microstructure and electrical, mechanical properties were analyzed.

• Journal of Korean Neurosurgical Society
• /
• v.30 no.6
• /
• pp.717-723
• /
• 2001

Objective : Subarachnoid hemorrhage(SAH) is still one of the most serious disease with high morbidity and mortality in the neurosurgical field. Clipping of the aneurysmal neck is the gold standard of the surgical treatment of aneurysmal SAH. The purpose of this study was to investigate the role of the postoperative angiography and to assess the risk factors related to the incomplete clipping. Materials and Methods : From July 1995 to June 1998, the pre- and postoperative angiography were performed in 50 patients among total 81 patients who have underwent the aneurysmal surgery. We reviewed the various contributing factors including age, sex, Hunt-Hess grade, Fisher grade and the premature rupture of aneurysm during operation retrospectively. Careful evaluation of pre- and postoperative angiography focusing on the size, shape, and remnant neck of the aneurysms and vasospasm was performed. According to the angiographic findings, the patients were divided into two groups ; a complete clipping group and an incomplete clipping group. The data were analyzed by using unpaired independent sample t test after F-test to compare the significance between two groups. Results : Incomplete clipping of aneurysms was found in 6(12%) patients through the evaluation of postoperative angiography. Among them, three cases were located on the middle cerebral artery territory. Whereas the patient age, sex, Hunt-Hess grade, and Fisher grade were not significant(p>0.05), an intraoperative premature rupture had a statistical significance(p<0.05). A severe vasospasm occurred in 24(48%) cases and one patient with anterior communicating aneurysm was reoperated due to residual sac. Conclusion : According to our experience, the surgeons' judgement is the most reliable factor in deciding the postoperative angiography. During the aneurysmal surgery, the premature rupture always disturbs a complete clipping of aneurysms. Therefore, the temporary clipping of parent arteries is considered essential for a successful clipping. We believe that the postoperative angiography has a role in decreasing the re-bleeding risk due to clip migration and an inaccurate clipping only in the selected cases.

• Journal of the Korean Institute of Gas
• /
• v.20 no.5
• /
• pp.9-16
• /
• 2016

Buried pipe system is subject to leak or rupture due to internal and external defects with age. Especially, if the pipeline is designed for pressurized gas, the leak can wreak a devastating on its surrounding area. The current method of setting up underground gas pipeline is based on OGP criteria of applying one tenth of the inner pipe pressure. The criteria is applied irrespective of their burial depth or pipe's properties. At times, even the whole safety measures are totally ignored. Considering the magnitude of possible damage from a gas leakage, a precise analytical tool for the risk assessment is urgently needed. The study was conducted to assess possible scenarios of gas accidents and to develop a computer model to minimize the damage. The data from ETA was analyzed intensively, and the model was developed. The model is capable of predicting jet fire influence area with comprehensive input parameters, such as burial depth. The model was calibrated and verified by the historic accident data from Edison Township, New Jersey, the United States. The statistical model was also developed to compare the results of the model in this study and the existing OGP model. They were in good agreement with respect to damage predictions, such as radiation heat coming from 10 meters away from the heat source of gas flame.

• Earthquakes and Structures
• /
• v.13 no.1
• /
• pp.59-66
• /
• 2017

Modern seismic codes rely on performance-based seismic design methodology which requires that the structures withstand inelastic deformation. Many studies have focused on the inelastic deformation ratio evaluation (ratio between the inelastic and elastic maximum lateral displacement demands) for various inelastic spectra. This paper investigates the inelastic response spectra through the ductility demand ${\mu}$, the yield strength reduction factor $R_y$, and the inelastic deformation ratio. They depend on the vibration period T, the post-to-preyield stiffness ratio ${\alpha}$, the peak ground acceleration (PGA), and the normalized yield strength coefficient ${\eta}$ (ratio of yield strength coefficient divided by the PGA). A new inelastic deformation ratio $C_{\eta}$ is defined; it is related to the capacity curve (pushover curve) through the coefficient (${\eta}$) and the ratio (${\alpha}$) that are used as control parameters. A set of 140 real ground motions is selected. The structures are bilinear inelastic single degree of freedom systems (SDOF). The sensitivity of the resulting inelastic deformation ratio mean values is discussed for different levels of normalized yield strength coefficient. The influence of vibration period T, post-to-preyield stiffness ratio ${\alpha}$, normalized yield strength coefficient ${\eta}$, earthquake magnitude, ruptures distance (i.e., to fault rupture) and site conditions is also investigated. A regression analysis leads to simplified expressions of this inelastic deformation ratio. These simplified equations estimate the inelastic deformation ratio for structures, which is a key parameter for design or evaluation. The results show that, for a given level of normalized yield strength coefficient, these inelastic displacement ratios become non sensitive to none of the rupture distance, the earthquake magnitude or the site class. Furthermore, they show that the post-to-preyield stiffness has a negligible effect on the inelastic deformation ratio if the normalized yield strength coefficient is greater than unity.

• Journal of the Korean Geosynthetics Society
• /
• v.12 no.1
• /
• pp.101-107
• /
• 2013

Environmental-friendly and economical construction are the recent issues for civil structures and soilbag as facing wall is widely used for cut-slope remediation projects. However, the stability of structures is an important issue for the use of environmental-friendly and economical materials. In order to understand the stability of soilbag reinforced retaining wall, tensile resistance, rupture, tensile strength, and internal/external safety factor of the wall were analyzed with MSEW program and the results were compared to the safety factor of block-type reinforced walls. The stability of retaining wall was analyzed with reduction coefficients of connection strength to check the connection stability. Because it is possible to move between soilbag and geogrid connector for soilbag retaining wall, the safety factor of the wall was analyzed with different inclination angles of soilbag. The analysis result shows that the connection strength and internal/external stability of soilbag reinforced wall satisfy the stability criteria.