• The Journal of Korean Academy of Prosthodontics
• /
• v.18 no.1
• /
• pp.15-35
• /
• 1980

The purpose of this study was to investigate stresses in the various components of fixed partial dentures restoring the posterior teeth of the lower jaw, and to measure quantitatively the effects of certain modifications in structural design on the stresses in the restorations using two-dimensional photoelasticity. Two-dimensional photoelastic methods were used in this study. Several models of fixed partial dentures were constructed. Shoulder less margins and anatomic occlusal reduction were incorporated in Model 1. Rounded shoulders and flat occlusal reduction were incorporated in Model 2, while Model 3 was a cantilever fixed partial denture. Other similar fixed partial dentures were constructed with V and U notches deliverately included in the region of the fixed joints for comparative reasons. The birefringent materials used in this study were PSM-1 and PSM-5 in standard sheets. PSM-1 was used for constructing the substructure, and PSM-5 was used in making the components of the fixed partial dentures. The two materials were used in the construction of composite photoelastic models. Improved artificial stone was used to represent dental cement in luting the composite photoelastic models. Static loading procedures were used at preplanned sites to represent occlusal loads in the mouth. 35 mm color and B/W film were used to record isochromatics in accordance with photoelastic procedures. Data reduction was performed using the grid method, which helped in, the mathematical integration procedure (Shear difference method) to separate the principal stresses. The results were as follows. 1. Fixed partial dentures do not function in bending as a symmetrical beam. Alternate areas of tension and compression were demonstrated when multiple contact loading was used. 2. The weakest part in posterior fixed partial dentures is the fixed joint. 3. (1) Models I and modified Model I were loaded on the pontic using a 50 pound vertical static load. The shear stress near the posterior fixed joint in Model 1 (U notches) was+129.4 p.s.i., and at the same fixed joint in modified Model 1 (V notches) was+239.4 p.s.i. The concentration of stress in fixed joint was reduced by 50% when U notches replaced the V notches. (2) Modified Model 2 was loaded using a multiple contact loader at a total load of 125 pounds. The difference between the principal stresses (${\sigma}_1-{\sigma}_2$), shear stress, at the V notches was+600 p.s.i., and at the U notches was+3l7 p.s.i. The shear stress was reduced by 50% when U notches replaced the V notches. V-grooves at the fixed joints should be avoided, and should be replaced by regular shaped U-grooves. 4. Cantilever fixed partial dentures had much higher stresses at the fixed joint than fixed partial dentures that were attached at both ends.

• Journal of the Korea Society of Computer and Information
• /
• v.18 no.11
• /
• pp.99-106
• /
• 2013

In Instant message service, the server should process instant messages and request messages which include many presence resources for users. And it also precesses massive notification messages generating from the subscribed presence resources. In this paper a new architecture of instant message service with multiple servers which can distribute loads efficiently as the number of users increases has been suggested. It also provides various functions to users using extended call processing language. The user subscribes presence information and call processing language script which describes user's functions. The server processes instant messages, presence services and call processing language scripts. New extended presence information data structure has been suggested and new call processing language operation tags have been added. Therefore extendability of the system can be increased and various services which combine presence service and call processing can be provided in this system. Furthermore instant message processing module has been integrated in the server to decrease the amount of SIP(Session Initiation Protocol) messages, and it also improves system efficiency, The performance of our proposed system has been analysed by experiments.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.7
• /
• pp.61-73
• /
• 2008

Piles of a bridge pier are connected with the column through the pile cap (footing). Behavior of the pile foundation can be different according to the connection method between piles and the pile cap. Connection methods between pile heads and the pile cap are divided into two groups : rigid connections and hinge connections. Domestic design code has been specified to use rigid connection method for the highway bridge. In the rigid connection method, maximum bending moment of a pile occurs at the pile head and this helps the pile to prevent the excessive displacement. Rigid methods are also good to improve the seismic performance. However, some specifications prescribe that conservative results through investigations of both the fixed-head condition and the free-head condition should be reflected in the design. This statement may induce an over-estimated design for the bridge which has high-quality structures with casing covered drilled shafts and the PC-house contained pile cap. Because the assumption of free-head conditions (hinge connections) is unreal for the elevated pile cap system with multiple piles of the long span sea-crossing bridges. On the other hand, elastic displacement method to evaluate the pile reactions under the pile cap is not suitable for this type of bridges due to impractical assumptions. So, full modeling techniques which analyze the superstructure and the substructure simultaneously should be performed. Loads and stress state of the large diameter drilled shaft and the pile cap for Incheon Bridge which will be the longest bridge of Korea were investigated through the full modeling for rigid connection conditions.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.1
• /
• pp.93-100
• /
• 2015

Modern wooden structures usually are connected with steel fastener type connectors. And joints using multiple connectors in wooden structures will form semi-rigid connection. If connection in wooden structure would be designed to be pinned joint, the underestimate for loads transmitted through connection, would result in the deficient capacity of resistance in connection. And if joints in wooden structures would be assumed to be fully-rigid joint, amount of fasteners needed at the connection could be excessively increased. It will give a bad effect in the view of beauty, constructability and economy. Estimate for the reasonable stiffness of connection might be essential in design of reasonable connection in wooden structure. This paper will suggest analysis modelling technique that can represent approximate stiffness of connections using a common analysis program for double shear connection in order to give help in performing easily the design of wooden structure. It is verified that the suggested approximate analysis modelling technique could represent the behavior in connection by comparing the analysis results with test results for tensile, bending moment.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.10
• /
• pp.655-660
• /
• 2018

Internal combustion generation (ICG) is used to supply power to islands due to geographical characteristics, but there are some problems, such as considerable operating cost, salt pollution, and environmental pollution. For these islands, KEPCO pays a significant amount of operating deficit each year, especially for the fuel and servicing costs, which account for a large portion of this deficit. Integrated ICG (IICG) through an offshore cable between near islands is being considered to decrease servicing costs. Distributed generation (DG) is also being introduced on the islands because of the demand for a low-carbon society. In hybrid internal combustion generation (HICG), DG is introduced into IICG, which can be applied because the DG output is insufficient due to environmental characteristics, and the IICG is used as an auxiliary power source. Therefore, this paper proposes an algorithm to estimate the optimal DG capacity that can be introduced in accordance with the KEPCO operating deficit in the HICG. According to simulations, the optimal DG capacity depends on the fuel cost and load capacity. The validity of the proposed algorithm was confirmed for multiple islands with different peak loads.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.2
• /
• pp.134-141
• /
• 2008

This paper presents an innovative load management technique that can effectively lower the summer peak load by adjusting the aircondition loads through smoothe coordinations between utility companies and large customers. An intelligent hierarchical load management system composed of a Central Intelligent Load Management System(CIMS) and multiple Local Intelligent Management Systems(LIMS) is also proposed to implement the reposed technique. Upon receiving a load curtailment request from the utilities, CIMS issues tokens, which can be used by each LIMS as a right to turn on the airconditioner. CIMS creates and maintains a queue for fair allocation of the tokens among the LIMS demanding tokens. By adjusting the number tokens and queue management Policies, desired load factors can be achieved conveniently. The Markov Birth and Death Process and the Balance Equations are employed in estimating various queue performances. The proposed technique is tested using a summer load data of a large apartment complex and proved to be quite effective in load management while minimizing the customer inconveniences.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.7B
• /
• pp.679-689
• /
• 2006

Delivering multicast stream is one of the cost-saving approach in the large scale VOD environment. Because implementing VCR-like interactions for user's convenience in the multicast streaming system involves complex problems, we need the proper solutions for them. In this paper, we propose a hybrid scheme which uses the general P2P and the patching scheme with the Collaborative Interaction Streaming Scheme(CISS). CISS provides jumping functionability to the appropriate multicast session after VCR-like interaction in the environment in which multiple peers transmit VCR-like interaction streams to the VCR-like functionability request node to reduce the loads generated by frequent join or departure of peers at the multicast tree during providing VCR-like functionability. Therefore, with the proposed scheme we can distribute network traffic and reduce control overhead and latency. And to evaluate the performance of proposed scheme we compare it in the aspect of the performance of streaming delivery topology, control overhead and streaming quality with P2Cast[10] and DSL[11]. The simulation result shows that proposed P2Patching reduces about 30% of process overhead and enhances about $25{\sim}30%$ of streaming quality compared with DSL.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.9 no.3 s.43
• /
• pp.51-58
• /
• 2005

Many RC building structures of multiple uses constructed in Korea have the Irregularities of torsion and soft story at bottom stories simultaneously. Seismic design codes generally require dynamic analysis and to take into account the effect or earthquake excitations in the orthogonal direction using the approximate methods of 100/30 and SRSS for type of building structures. And ail buildings should be designed to be safe in any direction of earthquake input. But, most of designers have difficulty in considering the orthogonal and directional effect of earthquake. The objective of the study stated herein is to verily 1) the effect of the choice of the reference axes on the seismic design member forces by comparing the analytical results on member forces using the principal axes suggested by Wilson and the global axes generally adopted in design office, 2) the validity or the 100/30 and SRSS methods by comparing the member forces obtained through linear elastic time history analysis with those obtained through using response spectrum analysis and 100/30 (or SRSS) methods. Based on the observations on the analytical results, it is concluded as follows; 1) The values of member forces by principal axes can be about $15\%$ smaller than those by the global axes in the example structure. 2) Though the values of member forces given by time history analysis are generally within the peak values predicted by 100/30 and SRSS methods, many member force vectors $(P,\;M_y,\;and\;M_z)$ by lime history analysis were located outside the boundaries predicted by the approximate method such as the 100/30 method.

• Composites Research
• /
• v.28 no.4
• /
• pp.219-225
• /
• 2015

Air spoiler, which can reduce the drag during operation, can be considered as a possible means to reduce carbon dioxide emission and to increase fuel efficiency. In this study, a composite air spoiler was designed and tested by static and repeated loads. The Green Water Pressure of 0.1 MPa a ship experiences during operation was perpendicularly applied to the air spoiler. Air spoiler was manufactured with sandwich panel which has glass fabric face and balsa core. Multiple sandwich panels were assembled to steel frame by bolt joint. The joint was designed to have bearing failure and examined by static and fatigue tests. Tests showed that the designed joint has enough margin of safety to endure joint failure. The developed sandwich panel to air spoiler is planned to be applied to a large scale commercial ship.

• Journal of the Korean GEO-environmental Society
• /
• v.10 no.1
• /
• pp.49-54
• /
• 2009

The seismic slope stability is most often evaluated by the pseudo-static limit analysis, in which the earthquake loading is simplified as static inertial loads acting in horizontal and/or vertical directions. The transient loading is represented by constant acceleration via the pseudostatic coefficients. The result of a pseudostatic analysis is governed by the selection of the value of the pseudostatic coefficient. However, selection of the value is very difficult and often done in an ad hoc manner without a sound physical reasoning. In addition, the maximum acceleration is commonly estimated from the design guideline, which cannot accurately estimate the dynamic response of a slope. There is a need to perform a 2D dynamic analysis to properly define the dynamic response characteristics. This paper develops a new hybrid pseudostatic method that links the modified one-dimensional seismic site response analysis and the pseudostatic algorithm. The modified site response analysis adjusts the density of the layers to simulate the change in mass and weight of the layers of the slope with depth. Multiple analyses were performed at various locations within the slope to estimate the change in seismic response of the slope. The calculated peak acceleration profiles with depth from the developed procedure were compared to those by the two-dimensional analyses. Comparisons show that the two methods result in remarkable match. The calculated profiles are used to perform pseudostatic analysis. The results show that use of peak or a fraction of acceleration at the surface can seriously underestimate or overestimate the factor of safety, and that the proposed procedure significantly enhances the reliability of a standard procedure.