• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.84-90
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• 2011

Handling paging mechanism at the IP layer (i.e., IP paging) makes it possible to support heterogeneous wireless access technologies, providing energy-saving and reduced location registration signaling overhead over IP-based mobile networks. However, IP paging may rather cause adverse effects under active communication environments because of significant paging signaling overhead and frequent paging delay. Therefore, in order to solve these problems, a cost-effective IP paging scheme is proposed in this paper, which enables a mobile node to perform selective registration and paging based on its profile information. Numerical results indicate that the proposed scheme has apparent potential to mitigate considerable paging signaling overhead and frequent paging delay in IP-based hierarchical mobile networks.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.115-116
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• 2006

UWB 시스템은 실내 LBS 에 가장 유망한 기술로 각광받고 있다. 그러나 실내건물을 이루는 손실성 매질로 인해서 신호에 지연이 발생, 거리오차가 발생하게 된다. 본 문제를 해결하기 위해서 공기중의 채널과 매질의 채널정보를 통해서, 신호의 지연을 추정하려고 하였다. 신호의 스팩트럼의 주파수에 관한 손실기울기는 투과한 매질의 두께에 비례하여, 깊어진다는 것을 사용하여, 매질 투과로 인한 신호의 지연시간을 추정하는 기술과 손실기울기를 측정하기 위한 RAKE 수신기를 소개한다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.3
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• pp.147-153
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• 1989

Laboratory measurement of compressional wave velocity for two piston cores has been carried out successfully. The cores penetrated into the Holocene mud deposit located just off the Pusan harbor. Differences between the mercury delay method using a mercury column and the time delay method utilizing a digital processing oscilloscope for the observed velocity are negligible. Thus, both methods can be used independently to determine the velocity of unconsolidated marine sediment. The core velocity is, however, always higher than the velocity calculated from the seismic profile. This result should be considered seriously to interprete a seismic profile, otherwise one may encounter systematic error in calculating sediment thickness.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2095-2100
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• 2012

In this paper, we propose the channel sounding scheme which is made for ideal communication between some application as well as the short distance of high speed data transmission in MIMO-OFDM system for Wireless PAN. This method is able to perceive the duration of the impulse response through the delaying of power delay profile, modeled a power delay profile which has an attenuate characteristic, and obtained the coefficient of channel response by ML (maximum likelihood). Through the amplitudes, phases and delays associated with each multipath component which were acquired from this channel sounding scheme, we can describe the wave propagation characteristics of channels between the transmitter and receiver so that the receiver could enhance not only the reliability but also the ability of communication link. Multi agent system models can be used to analyze the path of the system within any time frame. Further, parameter values can be perturbed to examine how the path of the system changes in response to exogenous shocks.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.9-15
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• 2006

This paper shows the impedance profile of PEEC(Partial Equivalent Electrical Circuit) PDN(Power Distribution Networks) including core and I/O circuit. Through the simulated results, we find that the core power noise having connection with I/O power is affected by I/O switching. Also, using designed $74{\times}5inch$ DLL(Delay Locked Loop) test board, we analyzed the effect of power noise on operation region of chip. Jitter of a DLL measure for frequency of $50{\sim}400MHz$ and compared with impedance obtained result of simulation. Jitter of a DLL are increased near about frequency of 100MHz. It is reason that the resonant peak of PDNs has an impedance of more the 1ohm on 100MHz. we present the impedance profile of a chip and board for the decoupling capacitor reduced the target impedance. Therefore, power supply network design should be considered not only decoupling capacitors but also core switching current and I/O switching current.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1058-1064
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• 2006

In this paper, the channel capacity of a specified wireless indoor multiple-input multiple-output(MIMO) channel is estimated by analyzing spatial characteristics of this channel using the three-dimensional ray tracing method, and a technique for deriving an optimized separation of multi-antenna elements is proposed. At first, the ray paths, the path losses, and the time-delay profile are computed using the three-dimensional ray tracing method in an indoor corridor environment, which has the line of sight(LOS) and non-line of sight(NLOS) regions. The ray tracing method is verified by a comparison between the computation results and the measurements which are obtained with dipole antennas, an amplifier and a network analyzer. Then, an MIMO system is positioned in the indoor channel environment and the ray paths and path losses are computed for four antenna-position combinations and various values of the antenna separation to obtain the channel capacity for the MIMO system. An optimum antenna-separation is derived by averaging the channel capacities of 100 receiver positions with four different antenna combinations.

• Clinical and Experimental Pediatrics
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• v.57 no.8
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• pp.363-369
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• 2014

Purpose: This study examines changes in developmental profiles of children with language delay over time and the clinical significance of assessment conducted at age 2-3 years. Methods: We retrospectively reviewed the medical records of 70 children (62 male, 8 female), who had visited the hospital because of delayed language development at 2-3 years, and were reassessed at ages 5-6. Language and cognitive abilities were assessed using multiple scales at the initial and follow-up visits. Results: At the initial test, 62 of the 70 children had mental development index (MDI) below 70 of Bayley Scales of Infant Development Test II. Of the 62 children in the follow-up assessment, 30 children (48.4%) remained within the same cognitive range (full-scale intelligence quotient, FSIQ<70 of Wechsler preschool and primary scale of intelligence), 12 had borderline intellectual functioning (FSIQ, 70-85), 6 improved to average intellectual functioning (FSIQ>85), and 5 had specific language impairment, 9 had autism spectrum disorders. At the initial test, 38 of the 70 children had cognitive developmental quotients (C-DQ) below 70. Of the 38 children in the follow-up assessment, 23 children (60.5%) remained within the same cognitive range (FSIQ<70). The correlation coefficient for MDI and FSIQ was 0.530 (P<0.0001) and that for C-DQ and FSIQ was 0.727 (P<0.0001). There was a strong correlation between C-DQ and FSIQ, and a moderate correlation between MDI and FSIQ. Conclusion: Low MDI scores reflect a specific delay in cognitive abilities, communication skills, or both. The C-DQ, receptive language development quotient, and social maturity quotient also help to distinguish between children with isolated language delay and children with cooccurring cognitive impairment. Moreover, changes in the developmental profile during preschool years are not unusual in children with language delay. Follow-up reassessments prior to the start of school are required for a more accurate diagnosis and intervention.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4977-4983
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• 2015

The full depth excavation induces couple of technical and social problems like increase of construction cost and time for excavation and backfill, increase of public complains and delay of traffic, and so force. In order to overcome these problems, lots of laboratory tests were carried out for sewer pipeline of maintenance materials with trenchless methods. The testing materials are PVC strip and then the lab tests were followed by Korean Standard. We will treat the structure safety and pipe integrity of PVC profile more excellent than the profile have application to SPR. There is no side-effect to process and to satisfy the criteria of tensile strength, impact strength and softening temperature. The profile with resin adhesive showed no leakage of water at specific pressure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4C
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• pp.342-352
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• 2002

In this paper, we compare the performances of RIO and RIO-DC buffer management schemes for DiffServ AF PHB standardized in IETF. For the comparison, we relatively differentiate maximum delay for each Assured Service subclass in Differentiated Services by allocating bandwidth to each subclass differently. In addition, we set the values of RIO and RIO-DC parameters considering the buffer size determined by the network topology and the ratio of bandwidth allocated to each subclass. In this simulation environment, the performances of RIO and RIO-DC schemes are analyzed focusing on the throughput of the In-profile traffic, the link utilization and the fairness. Simulation results show that the performance of RIO-DC scheme is comparable to that of RIO scheme with regard to the throughput of the In-profile traffic and the link utilization. However, under the simulation condition RIO-DC scheme improves the fairness between flows much better than RIO scheme.

• Convergence Security Journal
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• v.8 no.4
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• pp.105-113
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• 2008

Mobile computing environment is known to be quite difficult to provide user with a stable Quality of Service (QoS) due to vehicle mobility nature. In order to protect the inherent characteristics of wireless network such as low bandwidth and high transmission delay along with the vehicle's mobility, many works are conducted to apply caching and prefetching methods. This paper presents a novel prefetching technique which is based on owner's profile. It is the scheme with the vehicle velocity, the visit frequency and resident time of specific region for vehicle owner's past given period, and the user profile which has owner's personal inclination about a certain place. The proposed scheme shown relatively superior performance in terms of the utilization ratio of prefetched information and the failure ratio of information retrieval than the previous methods.