• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.779-789
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• 2014

Cognitive radio (CR) technology based on geo-location database access approach and/or wideband spectrum sensing approach is absolutely vital in order to recognize available frequency bands in white spaces (WSs), and efficiently utilize shared spectrums. This paper presents a new structure for the TVWS database access protocol implementation based on Internet Engineering Task Force (IETF) Protocol to Access WS database (PAWS). A wideband compressive spectrum sensing (WCSS) scheme using a modulated wideband converter is also proposed for the TVWS utilization. The developed database access protocol technology which is adopted in both the TV band device (TVBD) and the TVWS database operates well in the TV frequency bands. The proposed WCSS shows a stable performance in false alarm probability irrespective of noise variance estimation error as well as provides signal detection probabilities greater than 95%. This paper also investigates Federal Communications Commision (FCC) regulatory requirements of TVWS database as well as European Telecommunications Standards Institute (ETSI) policy related to TVWS database. A standardized protocol to achieve interoperability among multiple TVBDs and TVWS databases, which is currently prepared in the IETF, is discussed.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.701-708
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• 2007

A tilting train, which was developed to run the curve section without reducing the speed and compromising the riding quality, can improve the speed so as to reduce the travel time, compared to the existing trains. Then the force generated by the train operation to the track is in proportion to train operation speed, which means the track shall bear the increased force as much as the increase in train operation speed. Particularly, wheel load and lateral wheel load generated by train operation and distributed to the rail tend to cause the track to suffer the strain and furthermore the severe disaster such as derailment. To deal with such problem and ensure the train will run safety and stably, the tolerance in wheel load change, lateral wheel load and derailment coefficient was determined for quantitative evaluation of the train operation stability. In this study, derailment coefficient of inner and outer rail at existing curve section of tilting train was determined to evaluate the curve radius, possibility of acceleration and the need of rail improvement, which was then compared with the existing traditional train and high speed train. Conducting the quantitative evaluation of dynamic wheel load and lateral wheel load of each train, which was based on field survey, derailment coefficient and static & dynamic wheel load change, which serve the evaluation criteria of train operation stability, were determined for comparison with the standards, thereby analyzing the stability of the tilting train.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.259-266
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• 2017

The purpose of this study was to contribute to the field application cost effectively and reasonably by developing the functional piles that reinforces shear force. CFP pile (Concrete Filled Pretensioned Spun High Strength Concrete Pile with Ring type Composite shear connectors) developed in this study increases the shear stress by placing composite shear connector and filling the concrete into hollow part of the pile. By placing the reinforcement (H13-8ea) and the reinforcement (H19-8ea) into hollow section inside of PHC piles, it also improves the shear strength due to increasing steel ratio. It reinforces shear strength effectively by dowel force that is generated by putting reinforcement (H13-8) into the holes of composite shear connectors for the composite behavior of filled concrete and PHC pile. The study was reviewed and compared the calculated result of the shear strength by limit state design method highway bridge design standards (2012) and experiment result of the shear strength by KS F 4306. We can design the shear strength reasonably as the safety ratio of 2.20, 2.15, 2.05 is shown comparing to design shear strength, according to design shear strength on each cross sections and the experiment results of the CFP pile.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.1-14
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• 1996

Especially in the case of a full form ship, the stability on course can be considered to become severest among 4 items of criteria in Interim Standards for Ship Maneuverability adopted by IMO in 1993. The purpose of this study is to find some ideas for the improvement of stability on course through changes in rudder area with reference to span distance. In this paper, we established the formula on the relation between the experimental constants relevant to rudder normal force and hydrodynamic derivatives of hull-propeller-rudder system. We carried out various kinds of captive model test relevant to rudder normal force etc., and evaluated hydrodynamic derivatives of hull-propeller-rudder system, and analyzed the stability on course with the parameter of changes in rudder area. Furthermore, we also discussed effects of changes in rudder area on maneuvering performance including stability on course, based on computer simulation. As a result, it is clarified that there is a possibility that stability on course may become bad through an increase of rudder area. The reason for the bad stability on course is that the void space between the upper edge of rudder and the lower part of stern overhang decreases. This space change exerts a great influence on straightening coefficient of incoming flow to rudder in maneuvering motion, which has close relation to stability on course.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.5
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• pp.781-793
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• 2014

A Public Key Infrastructure (PKI) is security standards to manage and use public key cryptosystem. A PKI is used to provide digital signature, authentication, public key encryption functionality on insecure channel, such as E-banking and E-commerce on Internet. A soft-token private key in PKI is leaked easily because it is stored in a file at standardized location. Also it is vulnerable to a brute-force password attack as is protected by password-based encryption. In this paper, we proposed a new method that detects private key compromise and is probabilistically secure against a brute-force password attack though soft-token private key is leaked. The main idea of the proposed method is to use a genuine signature key pair and (n-1) fake signature key pairs to make an attacker difficult to generate a valid signature with probability 1/n even if the attacker found the correct password. The proposed method provides detection and notification functionality when an attacker make an attempt at authentication, and enhances the security of soft-token private key without the additional cost of construction of infrastructure thereby extending the function of the existing PKI and SSL/TLS.

• Journal of KIISE:Information Networking
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• v.29 no.1
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• pp.24-30
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• 2002

Label switching technology is currently emerging as a solution for the rapidly growing of Internet traffic demand. Multiprotocol label switching(MPLS) is one of the standards made by the Internet Engineering Task Force(IETE) intended to enhance speed, scalability, and inter-opearability between label switching technologies. In MPLS, utilization of label space is a very important factor of network performance because labels are basic unit in packet switching. We propose a algorithm to effectively use label space by a multiple disconnect timer at the label switching router. Our algorithm is based on multiple utilization of the connection release timer over the MPLS network with multiple domains. In our algorithm, a relatively linger timeout interval is assigned to the traffic with higher class by the aid of the packet classifier. This reduces delay for making a new connection and also reduces the amount of packets which will be routed to the layer 3. Simulation results shows that reduction of required label number in MPLS network and this indicate our algorithm offers better performance than the existing ones in term of utilization of label space.

• Journal of Animal Environmental Science
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• v.11 no.1
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• pp.25-34
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• 2005

The study aimed to develop a tractor drawn animal slurry manure sub-soil injector for arable land and thus, can reduce the waste management cost through effective treatment and utilization of animal slurry manure. The application of animal slurry manure to agricultural land will probably be one of the most effective ways to enrich the soil with vital nutrients. However, some existing slurry manure spenders are not suitable in the field because of their adverse effects to the environment. Based on this premise, a prototype was designed and assembled using 5 sub-soiling standards attached to the sin injector device. The traction force of the Prototype measured in the depth of 10 cm and 15 cm from the ground surface of a paddy field was 1,062 kgf and 1,214 kgf, respectively. A unique feature of the machine was that there was an equal volume of slurry manure flowing from each delivery pipe and regulated by a pressurized container that was likewise synchronized with the speed of the tractor The sub-soiling manure injection system can mitigate or reduce the harmful emission of obnoxious gases and malodor during the injection operation.

• Convergence Security Journal
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• v.17 no.5
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• pp.63-69
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• 2017

In the early 1990s, IETF(Internet Engineering TaskForce) had started the discussion on new address protocol that can modify and supplement various drawbacks of existing IPv4 address protocol with the introduction of CIDR(Classless Inter-Domain Routing) which is a temporary solution for IPv4 address depletion, NAT, private IP address. While various standards related to new address protocol has been proposed, the SIPP(Simple Internet Protocol Plus) was adopted among them because it is regarded as the most promising solution. And this protocol has been developed into current IPv6. The new concepts are introduced with modifying a lot of deficiencies in the exisitng IPv4 such as real-time data processing, performance on QoS, security and the efficiency of routing. Since many security threats in IPv6 environment still exist, the necessity of stable data communication environment has been brought up continuously. This paper deveopled one-way communication algorithm in IPv6 based on the high possibility of protecting the system from uncertain and potential risk factors if the data is transmitted in one way. After the analysis of existing IPv6 and ICMPv6, this paper suggests one-way communication algorithm as a solution for existing IPv6 and ICMPv6 environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.3
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• pp.68-76
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• 2021

Storage racks have suffered huge losses due to earthquakes, but related research and regulations are relatively insufficient non-structural elements compared to the structural elements. In this study, we tried to experimentally analyze the behavioral characteristics of storage racks due to external force according to the fixing conditions of the column-foundations connection of storage racks. In general, the column-foundations connection of storage racks is installed according to the user's convenience without installation standards and regulations. For this reason, this study conducted a behavior analysis test on four full-scale storage racks with the condition of column-foundations connection of four typical storage racks. The behavior characteristics analysis test was performed by two-direction of the shake table with El-Centro seismic wave. To confirm the behavior characteristics according to the magnitude of the seismic load, 50% ~ 150% of the seismic waves were increased by 50% for each test. In addition, a resonance search test was conducted to confirm the natural frequency of each storage racks foundations fixing condition. Among the data obtained through the test, the displacement of the top layer and the permanent displacement after the test were compared for each condition to analyze the behavior characteristics of the column-foundations fixed conditions of the storage racks. As a result, the change of natural frequency was small in storage racks due to the change of the conditions of the foundations, and the behavior characteristics were changed due to the difference of the restoring force due to the change of the storage racks foundations condition rather than the influence of the natural frequency of the input load.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.6
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• pp.825-836
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• 2022

Micropiles can be used to support additional load in extended building structures. However, their use brings about a risk of exceeding the bearing capacity of existing piles. In this study, pre-compression was applied to distribute the load of an existing building to micropiles, and an indoor loading test was performed to confirm the structural applicability of a wedge-type anchorage device designed to improve its capacity. According to the test results, the maximum strain of the anchorage device was 0.63 times that of the yield strain, and the amount of slip generated at the time of anchorage was 0.11 mm, satisfying structural standards. In addition, using MIDAS GTS, a geotechnical finite element analysis software, the effect of the size of the pre-compression, the thickness of the soil layer, and the ground conditions around the tip on the reaction force of the existing piles and micropiles were analyzed. From the numerical analysis, as the size of the pre-compression load increased, the reaction force of the existing pile decreased, resulting in a reduction rate of up to 36 %. In addition, as the soil layer increased by 5 m, the reduction rate decreased by 4 %, and when the ground condition at the tip of the micropile was weathered rock, the reduction rate increased by 14 % compared with that of weathered soil.