• Tunnel and Underground Space
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• v.23 no.1
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• pp.54-65
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• 2013

The LCM (Linear Cutting Machine) test is one of the most powerful and reliable methods for designing the disc cutter and for predicting the TBM (Tunnel Boring Machine) performance. It has an advantage to predict the actual load on disc cutter from the laboratory test on the real-size large rock samples, however, it also has a disadvantage to transport and/or prepare the large rock samples and to need an extra cost for experiment. In order to overcome this problem, lots of numerical studies have been performed. In this study, the PFC3D (Particle Flow Code in 3 Dimension) has been adopted for numerical analysis on optimum cutter spacing and failure aspects of Busan Tuff. The optimum cutting condition with s/p ratio of 16 and minimum specific energy of $14MJ/m^3$ was derived from numerical analyses. The cutter spacing for Busan Tuff had the good agreements with those of LCM test and numerical analysis by finite element method.

• Tunnel and Underground Space
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• v.27 no.6
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• pp.387-392
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• 2017

Recently, road cave-ins, also referred to as ground sinking, have become a problem in urban environments. Public utility facilities such as sewage pipelines, communications pipes, gas pipes, power cables, and other types of underground structures are installed below the roads. It was reported that cave-ins are caused by the aging and lack of proper maintenance of underground facilities, as well as by construction problems. A road cave-in is first initiated by the formation of cavities typically induced by the breakage of underground pipelines. The cavities then grow and reach the base of the pavement. The traffic load applied at the surface of the roads causes an abrupt plastic deformation. This type of accident can be considered as a type of disaster. A road cave-in can threaten both human safety and the economy. It may even result in the loss of human life. In the city of Seoul, efforts to prevent damage before cave-ins occur have been prioritized, through a method of discovering and repairing joints through the 3D GPR survey.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.90-94
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• 2007

The conventional single-reference station positioning is affected by systematic errors such as ionospheric and tropospheric delay, so that the rover must be located within 10 km from the reference station in order to acquire centimeter-level accuracy. The medium-range real-time kinematic has been proven feasible and can be used for high precision applications. However, the longer of the baseline, the more of the time for resolving the integral ambiguity is required. This is due to the fact that systematic errors can not be eliminated effectively by double-differencing. Recently, network approaches have been proposed to overcome the limitation of the single-reference station positioning. The real-time systematic error modeling can be achieved with the use of GPS network. For expanding the effective range and decreasing the density of the reference stations, Land Survey Bureau, Ministry of the Interior in Taiwan set up a national GPS network. In order to obtain the high precision positioning and provide the multi-goals services, a GPS network including 66 stations already been constructed in Taiwan. The users can download the corrections from the data center via the wireless internet and obtain the centimeter-level accuracy positioning. The service is very useful for surveyors and the high precision coordinates can be obtained real time.

• Journal of Korean Society of Transportation
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• v.27 no.6
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• pp.7-18
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• 2009

In 2008, there are 135 service areas, which provide for drivers to convenience on expressways. But there are some problems on parking capacity, because it is failed to calculate the appropriate parking lots of the service area. The fundamental problem is that the size of parking lots is calculated by simple value; despite there are various factors of utilization, congestion, and turnover. This paper describes a study on proper coefficient for calculating the appropriate service area, considering the characteristics of drivers' behavior. We conducted statistical analysis with the surveyed data in "Status of the expressway facilities in 2004." Analysis results show there are some difference by day and night, and vehicle type with the factor of utilization, congestion, and turnover, and there are different usages according to expressway route. The results indicate that the usage of a service area have different characteristics by time and space, and vehicle type.

• Journal of the Korean School Mathematics Society
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• v.16 no.2
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• pp.319-335
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• 2013

Chinese mathematical curriculum is divided 4 areas(number and algebra, space and figure, statistics and probability, practice and synthetic application). The purpose of this paper is to analyze the contents of the practice and synthetic application in yanbian elementary textbook. For this, 12-textbook which was published in yeonbeon a publishing company is analyze by topic, mathematical process, area of content and mathematical activity. mathematical process The following results have been drawn from this study. First, contextual backgrounds of practice are restricted in classroom. The contents of synthetic application are limited in connection of mathematical areas. Mathematical problem solving is a main in mathematical process, whereas reasoning activity is a few. Mathematical experience activity is a main in mathematical process, whereas synthetic activity is a few. We can use the suggestions of this paper for development of textbook and the contents of mathematical process.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.572-578
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• 2003

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings in a HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Raynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigenvalue problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• Journal of Internet Computing and Services
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• v.3 no.3
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• pp.11-17
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• 2002

The web-based distance education has some problems in managing students despite the merit of getting over the problem of time and space compared with the classroom education or residential course. These problems make the web-based distance learners difficult in achieving the purpose and the standard of goal. And they drive the manager in charge of the web-based distance education into worries. The manager of the distance education should keep on monitoring students' participation and response, and then give the appropriate feedback to the students. But, the existing distance education system neglects to support efficient management function, for it puts emphasis on the activity of teaching and learning. Therefore, the purposes of this study are to extract the factors that are necessary to manage the distance education for training teachers, to realize the effective management system which can offer a proper feedback in the distance education for training teachers through the application of those factors to the training program, to make it possible to change the management system flexibly according to the curriculum and the computing setting.

• Journal of Internet Computing and Services
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• v.8 no.1
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• pp.79-85
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• 2007

As the use of the computer and networks generalized, the various tasks which are requested secrets can be processed such os the banking transaction. And because of increasing of data exchange, Internet, and mobile networks, the method which is not connected only but also used with many users has been changed. Especially because of the structural problem of the Internet, a lot of information is leaked out when we use the Internet banking. If we check the Internet banking by using an existing cypher method which is either simple of slow, a credit card number, an account number or password will be leaked out. Because the security of information doesn't meet our expectation, we need more powerful cryptography. But, the wasted space-time which is required shouldn,t be ignored when the whole transferred data are encrypted. So, by using both the Elliptic Curve algorithm which is based on mobile networks and the partial encryption of the DTD of XML in this essay, we will implement more faster cypher method of the partial XML.

• Archives of Plastic Surgery
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• v.35 no.1
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• pp.86-91
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• 2008

Purpose: The performance of rhinoplasty on the patient who has already undergone unsatisfactory results or complications after augmentation rhinoplasty is a challenging surgical problem. Because the dead space is remained after removal of the foreign body and the thickness of the skin is not even, the deformity would be more conspicuous if the nose is reconstructed again with hard implant only or autogenous cartilage. In these cases, the autogenous fascia can be used to get a good result. We present our clinical experience of secondary rhinoplasty using Scarpa's fascia of lower abdomen. Methods: Thirty-two patients underwent the procedure from March of 2002 to February of 2007. Nine patients were reconstructed with Scarpa's fascia only, eighteen patients were reconstructed with silicone implant and fascia, and five patients were reconstructed with cartilage and fascia for secondary rhinoplasty. Results: There were no major complications. Most of the patients were satisfied with the results. The deviation of the silicone implant and postoperative hypertrophic scar of the donor site were seen in one case each. Postoperative absorption of fascia were seen in two cases using Scarpa's fascia only. Conclusion: Secondary rhinoplasty using Scarpa's fascia is very useful method which offers a minimized donor site scar, low complication rate, shorter operation time and patient satisfaction and prevents the alopecia caused by the harvest of temporalis fascia.

• Tunnel and Underground Space
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• v.15 no.5 s.58
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• pp.359-368
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• 2005

In case the overburden of a tunnel is too low to adopt NATM, cut and cover method generally can be chosen as alternative. However, in tunneling some area with very low or no overburden between two mountains, the cut and cover method requires additional construction of a couple of tunnel portals and the maintenance of portal slopes until backfilling is completed. As a solution for this problem, increasing the tunnel overburden by raising the ground level can be effective. This paper presents the case study for tunneling at C240 site in Taiwan High Speed Railway(THSR) in which soil-cement filling method was used for pre-banking before tunnel excavation. Cement content of filling material was $2\~4\%$ and thickness of filling a round was $130\~250\;mm$. The stability evaluation for the soil-cement slope and concrete lining of low cover tunnel was conducted by numerical analysis.