• Proceedings of the KSR Conference
• /
• 1999.11a
• /
• pp.558-565
• /
• 1999

Rubber wheel-type AGT has two major kinds of bogie; one is the bogie type and the other and passenger loads. This paper deals with the statics analysis for two types of bogie frame subjected to combined external forces, as well as independent ones specified in UIC 515-4. Furthermore, the dynamics analysis is performed under vibrational loading conditions so as to compare dynamic characteristics, Numerical results by using commercial packages, Ⅰ-DEAS and NASTRAN show that maximum stresses do not exceed the yielding level of material used for both bogies. From an overall viewpoint of strength, the bogie type turns out to be superior to the steering type except the case of a lateral loading. It is also observed that the steering type shows a be stiffened. It is strongly anticipated that vibrational fatigue analysis should be carried out under realistic loading conditions closely matching to situations such as running surface and lateral clearances along the guideway.

• International conference on construction engineering and project management
• /
• 2009.05a
• /
• pp.1094-1099
• /
• 2009

Workforce information is important in production planning because production planning requires matching a production unit's capacity to loads of assignments. However, tracking and managing workforce information such as skills and accident history is not an easy job. This paper describes a prototype database system for a workforce database system that employs RFID technology. This system tracks daily workforce production capacity on sites. A pilot project is described to explore the benefits and possibility of using radio-frequency identification (RFID) to track and manage workforce information, and is followed by the results of a survey to identify benefits. In addition to the survey identifying the benefits of the database system, the paper also presents a list of challenges through a series of interviews.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2000.11a
• /
• pp.225-228
• /
• 2000

In this paper, the design for a low noise amplifier with the EM simulation is presented. The ATF36077 pHEMT device is applied to design LNA for U-NII frequency band (5 GHz ～ 6 GHz). The matching networks have been designed by the only open ended stub in order to reduce parasitic effects generated from a via structure. Through EM simulator, the simulation result shows that the linear gain (@5.5 GHz) is over 10 dB, input return loss and output return loss (@ 5.5 GHz) are a below 10 dB respectively, and the 3rd order intercept point is about 17 dBm.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.23 no.6
• /
• pp.868-873
• /
• 1986

The Schottky barrier diode has been used as an element of the mixer inspite of its conversion loss. In this paper the use of a GaAs MESFET is shown as a device of mixer, and the conversion gain is obtained. Also, input matching circuits aredesigned by s-parameter and fabricated on a dielectric teflon epoxy fiber glass substrate. According to the results, the conversion gain is 9 dB at the signal frequency of 4 GHz and the intermediate frequency of 1.217GHz.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.2
• /
• pp.85-89
• /
• 2011

In this paper, a novel Class-E power amplifier using metamaterials has been realized with one RF LDMOS diffusion metal-oxide-semiconductor field effect transistor. The CRLH structure can lead to metamaterial transmission line with the Class-E power amplifier tuning capability. The CRLH TL is achieved by the frequency offset and the nonlinear phase slope of the CRLH TL for the matching network of the power amplifier. Also, the proposed power amplifier has been realized by using the CRLH structure in the output matching network for better efficiency. Operating frequencies are chosen at 13.56 MHz in this work. The measured results show that the output power of 39.83 dBm and the gain of 11.83dB was obtained. At this point, we have obtained the power-added efficiency (PAE) of 73 % at operation frequency.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.1
• /
• pp.23-28
• /
• 2009

The general six-port phase correlator is comprised of a Wilkinson power divider and three $90^{\circ}$ hybrid coupler, which has less than 10 % bandwidth. In this paper, the six-port phase correlator using two section power divider has 33 % bandwidth and external matching $90^{\circ}$ hybrid coupler with 15 % bandwidth was designed at the center frequency of 2.5 GHz. The simulation result by ADS2003A indicates that RF port and LO port of proposed six-port phase correlator got wide frequency bandwidth of 14 % for VSWR of 1.5. The fabricated six-port phase correlator has a bandwidth of 12 % similar to the simulation result. The maximum phase discrepancy and insertion loss are $6^{\circ}$ and 2.5 dB over a bandwidth, respectively.

• The Journal of the Korea Contents Association
• /
• v.17 no.11
• /
• pp.389-397
• /
• 2017

Recently semantic web document is produced and added in repository in a cloud computing environment and requires an intelligent semantic agent for analytical classification of documents and information retrieval. The traditional methods of information retrieval uses keyword for query and delivers a document list returned by the search. Users carry a heavy workload for examination of contents because a former method of the information retrieval don't provide a lot of semantic similarity information. To solve these problems, we suggest a key word frequency and concept matching based semantic clustering model using hadoop and NoSQL to improve classification accuracy of the similarity. Implementation of our suggested technique in a cloud computing environment offers the ability to classify and discover similar document with improved accuracy of the classification. This suggested model is expected to be use in the semantic web retrieval system construction that can make it more flexible in retrieving proper document.

• The Journal of the Korea Contents Association
• /
• v.9 no.11
• /
• pp.54-62
• /
• 2009

To avoid the redundant investment on the project selection process, it is necessary to check whether the submitted research topics have been proposed or carried out at other institutions before. This is possible through the search engines adopted by the keyword matching algorithm which is based on boolean techniques in national-sized research results database. Even though the accuracy and speed of information retrieval have been improved, they still have fundamental limits caused by keyword matching. This paper examines implemented TFIDF-based algorithm, and shows an experiment in search engine to retrieve and give the order of priority for similar and redundant documents compared with research proposals, In addition to generic TFIDF algorithm, feature weighting and K-Nearest Neighbors classification methods are implemented in this algorithm. The documents are extracted from NDSL(National Digital Science Library) web directory service to test the algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.7B
• /
• pp.595-601
• /
• 2006

This study presents an ultrasonic location awareness system for the ubiquitous computing with absolute position. The flight time of ultrasonic waves is determined by a period detecting technique which is able to extend the sensing range compared with traditional methods. For location awareness, ultrasonic waves are sent successively from each ultrasonic transmitter and synchronized by radio frequency (RF) signal, where the transmitting part is fixed and the receiving part is movable. To expand the recognizing range, cell matching technique and coded ultrasonic technique are introduced. The experimentation for various distances is accomplished to verify the used period detecting technique of U-SAT system. The positioning accuracy by using cell matching is also verified by finding the locations of settled points and the usability of coded ultrasonic technique is verified. As a result, the possibility of ultrasonic location awareness system for the ubiquitous computing can be discussed as a pseudo-satellite system with low cost, a high update rate, and relatively high precision, in the places where GPS is not available.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.3 s.357
• /
• pp.78-84
• /
• 2007

A multistandard direct-conversion mixer for WCDMA, Wibro, and 802.11a/b/g is designed in 0.18 um CMOS technology To support multistandard and to reduce the chip area the switched inductor is used as the matching method. This switched inductor matching network selects the mixer's operation frequency band by turning on or off the switch transistor. Since the performances of mixer and operation frequency can be affected by the parasitic of switch transistor the mixer should be designed with the optimized size of switch to minimize parasitic effects. Proposed mixer is able to achieve return loss less than -13 dB in $2.1\sim2.5GHz$ and $5.1\sim5.9GHz$ bands with the suitable performance to meet requirements of WCDMA, WiBro, and 802.11a/b/g.