• Journal of Navigation and Port Research
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• v.27 no.3
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• pp.283-288
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• 2003

Recently, the growth of applications and services over high-speed Internet increases, ATM networks as wide area back-bone has been a major solution. As the conventional TCP/IP suite is still the standard protocol used to support upper application on current. Internet, the issues regarding whether TCP/IP will operate efficiently on top of an ATM infrastructure and how to control its QoS still remain for studies. TCP uses a window-based protocol for flow control in the transport layer. When TCP uses the UBR service in ATM layer, the control method is only buffer management. If a cell is discarded in ATM layer, one whole packet of TCP will be lost; this fact occur the most TCP performance degradation. Several dropping strategies, such as Tail Drop, EPD, PPD, SPD, FBA, have been proposed to improve the TCP performance over ATM. In this paper, to improve the TCP performance, we propose a packet dropping scheme that is based on comparison with EPD, SPD and FBA. Our proposed scheme is applied to schemes discussed in the previous technology. Our proposed scheme does not need to know each connection's mean packet size. When the buffer exceeds the given threshold, it is based on comparison between the number of dropped packet and the approved packet. Our results are reported and discussed for comparing these discarding schemes under similar conditions. Although the number of virtual channel (VC) is increased, the simulation results showed that the proposed scheme can allocate more fairly each VC than other scheme.

• Journal of Advanced Navigation Technology
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• v.16 no.5
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• pp.794-800
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• 2012

In this paper, we propose a scheme for improving not only the utilization of frequency bands in the guard channel scheme but also the dropping rate of cognitive radio user in the wireless cognitive radio-based cellular network. The proposed scheme enables cognitive radio users to utilize the guard channel for servicing only handoff calls in normal times, but cognitive radio users must vacate the frequency channel when handoff call appearing. At this time our scheme ensures their seamless services for cognitive radio users, by predicting handoff call's appearance by MMOSPRED (Multi-Media One Step Prediction) method and then reserving the demanded channels for spectrum handoff calls. Our simulations show that our scheme performs better than other schemes; GCS(Guard Channel Scheme) and a scheme without prediction in terms of cognitive users call's dropping rate and resource utilization efficiency.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.895-906
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• 2014

A fundamental study of the dynamically penetrating anchor (DPA - colloquially known as torpedo anchor) embedded into deep seabed was conducted using measurement data and numerical approaches. Numerical simulation of such a structure penetration was often suffered by severe mesh distortion arising from very large soil deformation, complex contact condition and nonlinear soil behavior. In recent years, a Coupled Eulerian-Lagrangian method (CEL) has been used to solve geomechanical boundary value problems involving large deformations. In this study, 3D finite element analyses using the CEL formulation are carried out to simulate the construction process of dynamic anchors. Through comparisons with results of field measurements, the CEL method in the present study is in good agreement with the general trend observed by in-situ measurements and thus, predicts a realistic large deformation movement for the dynamic anchors by free-fall dropping, which the conventional FE method cannot. Additionally, the appropriate parametric studies needed for verifying the characteristic of dynamic anchor are also discussed.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.307-310
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• 2000

ATM is the switching and multiplexing technology chosen by the ITU-T for the operation of B-lSDN. Basically, ATM technology is designed to combine the reliability of circuit switching with the efficiency and flexibility of packet switching technology. For servicing QoS in IPOA(IP over ATM) when the larger effort is given, it will be the good method that the original QoS benefits having ATM switching have in ATM layer underlying layer. The IETF has recently proposed Differentiated Services framework for provision of QoS. In this paper we analyse performance of two Diffserv mechanism. Threshold Dropping and Priority Scheduling. Threshold Dropping and Priority Scheduling can be regarded as basic mechanisms from which the other mechanisms have been derived. Hence comparative performance of these two mechanisms in providing required QoS is an important issue. In this Paper we carry out a performance comparison of the TD and PS mechanisms with the aim of providing the same level of packet loss to the preferred flow. Our comparison of the TD and PS allows us to determine resultant packet loss for the non-preferred flows as a function of various parameters of the two mechanisms.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.738-745
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• 2004

There are a number of ways to reduce the ground vibrations, one of which is by installing underground walls. Model tests for ground vibration have been conducted in recent years, but limited attention has been paid to underground wall which can reduce high vibrations. Up to date, only barriers have been actually installed in dry sand because of many unknown factors subsisting on the behavior of the ground. The characteristics of vibration sources, ground conditions and wall barriers have not been well understood yet, therefore centrifugal modeling was adopted to examine all these characteristics. This paper describes a ball dropping system, which can generate a pulse wave propagation through soil mass, and the test results show the effectiveness of underground wall barrier in reducing mechanical vibration.

• 전자공학회논문지 IE
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• v.45 no.3
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• pp.50-55
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• 2008

In CDMA system, the number of mobile stations which can be served simultaneously in a base station is limited by the amount of total interference received. Considering the facts, the call admission control method using the effective bandwidth concept is employed in this paper. The bandwidth for a new call and a handoff call is allocated by considering the number of mobile station being served and dynamically assigned by taking account of the blocking rate of new calls and the dropping rate of handoff calls. Also, there is reserved resource for handoff call. We analyze the performance of system according to reserved resource by a simulation study. The more a resource reserved, the less it is the dropping rate of handoff.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.85-94
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• 2005

In this thesis, we propose a Speed Accommodation Priority Algorithm Scheme(SPAS) and Traffic Control Model Scheme (TCMS) to satisfy a desired handoff dropping probability and to reduce the blocking probability of new calls using mobility characteristics and handoff rate in mobile communication networks. The guard channels below threshold can guarantee the Quality of Service(QoS) in terms of the request handoff dropping probability and the guard channels above the threshold can be used to handle high priority new calls and high priority handoff calls. When the ratio of the handoff call arrival rate is less then the ratio of the new call arrival rate, the proposed method can guarantee the new call better than the previous guard channel scheme.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1097-1103
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• 2001

TiO$_2$anchored on a porous clay ceramic support (PCS) for use in lightweight photocatalyst were synthesized by the dropping precipitant method. A PCS of macro and micro pore size of around several mm~${\mu}{\textrm}{m}$ in diameter were prepared by the rapid heat treatment at, 1,15$0^{\circ}C$ for 10 min from low grade of clay. The change in pH of reaction solution due to the different addition rate of NH$_4$HCO$_3$as a precipitant, the reaction temperature and the concentration of TiCl$_4$had a pronounced effect on the nature of precipitated TiO$_2$particles on the surface of a PCS and the crystal structure of precipitated TiO$_2$particles. At an addition rate of 0.8 ml/min of NH$_4$HCO$_3$and pH=6 of reaction solution, homogeneous precipitation of TiO$_2$particles on a PCS was achieved. TiO$_2$particles with anatase phase was precipitated on the surface of a PCS at the low concentration of TiCl$_4$, the high addition rate of NH$_4$HCO$_3$and the high reaction temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.317-317
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• 2006

This study is about Sealant for LCD panel which used m manufacture of liquid crystal display device with LC dropping method, with the least contamination of liquid crystals, the best adhesion of glass and Improvement of photoreaction for shaded area.

• Journal of Welding and Joining
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• v.5 no.1
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• pp.57-63
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• 1987

A method which can be used for evaluating slag detachability is proposed in this study. The proposed method was intended to get an absolute value for slag detachability, to give consistent value for a given welded joint, and finally to be simple to test. With a test fig made in this study, an impact by dropping a steel ball (13Kg in weight) is applied on the back side of an as-welded plate having a slag layer on the weld bead. Such impact applied forces the slag to drop off from the bead surface. In order to make a quantitative evaluation the amount of slag removed was measured with increasing the number of drops. Using this method six kinds of fluxes were evaluated in terms of the effects of flux type, basicity and weding variables on the slag detachability. As an initial result of this test, it was found that welding heat input affects the detachability significantly. Most importantly the evaluation made using the presently proposed method gives the same order of ranking as that of the actual practice done by a welder.