• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.199-208
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• 2013

So far today, there is a speed limit by the radius of curve based on operation regulation in domestic railway, however a study for the maximum running speed at the curved section without any derailment would be necessary. The two major factors related to the running safety of railway vehicle are classified as the railway vehicle condition and the track condition. In terms of the rail inclination among many other factors, the determination of rail inclination within the possible limit is necessary for the geometrical structure of the optimum track. The disregard of the geometrical parameter related to the rail inclination may cause a serious problem to the running safety of railway vehicle. This study is focusing on the analyzing of running safety regard to the change of rail inclination among the many other parameters to improve derailment safety, so that there is an affection analysis of the running safety regard to the change of rail inclination in the ideal and geometric track condition. Also There is an affection analysis of the running safety regard to the simultaneous change of rail inclination and the running speed at the curved section. According to analysis results of running safety, In case that the left and right rail inclination are 1/40, the running safety of this condition defined than other conditions. Also, the rail inclination of conventional lines is 1/40, Therefore, the railway vehicle passing through curve is safe when the railway vehicle runs in conventional lines.

• Journal of the Korean Data and Information Science Society
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• v.28 no.6
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• pp.1245-1255
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• 2017

The online learning is a process of obtaining the solution for a given objective function where the data is accumulated in real time or in batch units. The stochastic gradient descent method is one of the most widely used for the online learning. This method is not only easy to implement, but also has good properties of the solution under the assumption that the generating model of data is homogeneous. However, the stochastic gradient method could severely mislead the online-learning when the homogeneity is actually violated. We assume that there are two heterogeneous generating models in the observation, and propose the a new stochastic gradient method that mitigate the problem of the heterogeneous models. We introduce a robust mini-batch optimization method using statistical tests and investigate the convergence radius of the solution in the proposed method. Moreover, the theoretical results are confirmed by the numerical simulations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.11
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• pp.1201-1208
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• 2009

The Direction-Of-Arrival(DOA) resolution of signals depends on the aperture size of the array. Therefore it is not easy to resolve closely spaced coherent signals impinge on an array with a small radius. In order to overcome the problem, a new method is proposed to use the characteristic of spatial spectrums for arrays which have different aperture sizes after virtually expanding the spacing of original antenna array. In case of coherent signals impinge on an uniform circular array, the perfect DOA resolution capability of 100 % is achieved at the SNR range of -10 dB to 0 dB by the Deterministic Maximum Likelihood(DML) algorithm including the proposed method. On the other hand, the standard DML algorithm can not resolve signals at all at the same SNR.

• Journal of Intelligence and Information Systems
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• v.14 no.4
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• pp.201-216
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• 2008

Nowadays various new items are available, but limitation of searching effort makes it difficult for customers to search new items which they want to purchase. Therefore new item providers and customers need recommendation systems which recommend right items for right customers. In this research, we focus on the new item recommendation issue, and suggest preference boundary- based procedures which extend traditional content-based algorithm. We introduce the concept of preference boundary in a feature space to recommend new items. To find the preference boundary of a target customer, we suggest heuristic algorithms to find the centroid and the radius of preference boundary. To evaluate the performance of suggested procedures, we have conducted several experiments using real mobile transaction data and analyzed their results. Some discussions about our experimental results are also given with a further research area.

• Journal of Korean Society for Geospatial Information Science
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• v.8 no.1 s.15
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• pp.97-103
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• 2000

The main purpose of 1-1-9 Caller Location Information System is to identify and display the precise location of emergency incidents such as natural or man - made fires, medical emergencies and accidents. The state - of- the - art technologies such as Am (Automatic Number Identification), GIS(Geographical Information System) and GPS (Global Positioning System) were applied and integrated in the system for efficient and effective location identification. It displays a radius of 25M, 50M and 100M on the map after location identification. The system can also provide the shortest path to an incident location from a fire station or a fire engine. In case of a fire breakout in or near a building, the attribute information of the building, called a building attribute card, is displayed along with the map location. The system then matches the information with the fire situation and sends an alert to a responsible fire station by phone or fax in order to help promptly react to the problem. An attribute card includes the critical information of a premise such as building's location, number of stories, floor plans, capacity, construction history, indoor fire detection and Prevention facilities, etc.

• Geotechnical Engineering
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• v.14 no.1
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• pp.93-108
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• 1998

In this study, the analytic solutions and numerical methods were used to estimate the shape and size effects on the stability of underground openings. The stability of underground openings was evaluated by scrutinizing the effects of the rock mass quality, the state of in-situ stresses and the lateral earth pressure coefficient on the displacement, the stress concentration and the plastic region developed in the vicinity of the openings. The analytic solutions have shown that the stress concentration factor is inversely proportional to the radius of curvature of openings. Through parametric study on the various shapes and sizes of underground openings the characteristics of the controlling factors concerned with the stability were analyzed. Then, the study was extended to the horseshoe-shaped openings commonly used for under ground storage. Through the extended study the effects of the stress ratio and the height-towidth ratio of openings on the maximum displacement and plastic region developed around the openings were estimated. The results have shorn that the height-to-width ratio of domestic storage caverns can be increased economically without stability problem, as far as the lateral earth pressure coefficient is appropriate.

• Journal of the Korean Ceramic Society
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• v.45 no.4
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• pp.220-225
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• 2008

Lead-free ferroelectric ceramics are widely researched today for industrial applications as sensors, actuators and transducers. Since $Pb(Zr_aTi_{1-a})O_3$-(PZT) has high Curie temperature($T_C$), high piezoelectric properties near its morphotropic phase boundary(MPB) composition and small temperature dependence electrical behavior, it has been used to commercial materials for wide temperature range and different application fields. According to the tolerance factor concept, since the $Bi^{3+}$ cation with 12-fold coordinate has a smaller ionic radius than 12-fold coordinate $Pb^{2+}$, most bismuth based perovskites possess a smaller tolerance factor. Therefore, MPBs with a higher $T_C$ may be expected in $Bi(Me^{3+})O_3PbTiO_3$ solid solutions. As in lead based perovskite systems, it is clear that we need to explore more materials in simple or complex bismuth based MPB systems. The objective of this study is to investigate the $Bi(Ni_{1_a}X_a)O_3-PbTiO_3(X=Ti^{4+},\;Nb^{5+})$ perovskite solid-solution. For improving the electronic conduction problem, the magnesium and manganese modified system was also studied.

• Journal of the Korean Vacuum Society
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• v.7 no.2
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• pp.88-93
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• 1998

The fabrication process and emission characteristics of gated silicon field emitter arrays(FEAs) using chemical-mechanical-polishing (CMP) method are described. Novel fabrication techniques consisting of two-step dry etching with oxidation of silicon and CMP processes were developed for the formation of sharp tips and clear-cut edged gate electrodes, respectively. The gate height and aperture could be easily controlled by varying the polishing time and pressure in the CMP process. We obtained silicon FEAs having self-aligned and clear-cut edged gate electrode opening by eliminating the dishing problem during the CMP process with an oxide mask layer. The tip height of the finally fabricated FEAs was about 1.1 $\mu$m and the end radius of the tips was smaller than 100 $\AA$. The emission current meaured from the fabricated 2809 tips array was about 31 $\mu$A at a gate voltage of 80 V.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.4
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• pp.77-87
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• 1994

This paper deals with an automated forming sequence design system by which designers can determine desirable operation sequences even if they have little experience in the design of cold forging process. The forming sequence design in the cold forging is very important and requires many kinds of technical and empirical knowledge. They system isproposed, which generates forming sequence plans for the multistage cold forging of axisymmtrical solid products. Since the process of metal forming can be considered as a transformation of geometry, treatment of the geometry of the product is a key in planning process. To recognize the geometry of the product section, section entity representation and primitive geometries were used. Section entity representation can be used for the calculation of maximum diameter, maximum height, and volume. Forming sequence for the part can be determined by means of primitive geometries such as cylinder, cone, convex, and concave. By utilizing this geometrical characteristics (diameter, height, and radius), the product geometry is expressed by a list of the priitive geometries. Accordingly the forming sequence design is formulated as the search problem which starts with a billet geometry and finishes with a given product one. Using the developed system, the sequence drawing with all dimensions, which includes the proper sequence of operations for the part, is generated under the environment of AutoCAD. Based on the results of forming sequence, process variables(strain, punch pressure, die inner pressure, and forming load) are determined.

• Journal of Internet Computing and Services
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• v.10 no.2
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• pp.153-160
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• 2009

One of the major challenges of designing a dissemination protocol for Wireless Sensor Networks(WSNs) is energy efficiency. Recently, this issue has received much attention from the research community, and SPMS, which outperforms the well-known protocol SPIN, specially is a representative protocol. In addition, one of many characters of SPMS is the use of the shortest path to minimize the energy consumption. However, since it repeatedly uses the same path as the shortest path, the maximizing of the network lifetime is impossible, though it reduces the energy consumption. In this paper, we propose a dissemination protocol using probability-based clustering which guarantees energy-efficient data transmission and maximizes network lifetime. The proposed protocol solves the network lifetime problem by a novel probability function, which is related to the residual energy and the transmission radius between nodes. The simulation results show that it guarantees energy-efficient transmission and moreover increases the network lifetime by approximately 78% than that of SPMS.