• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.7
• /
• pp.1539-1545
• /
• 2015

GPS (global positioning system) is a popular system that provides location information by measuring arrival time difference at the receiver between several GPS satellite signals. GPS is widely used in commercial area as well as military systems. Reliable GPS signal reception is more important in the military systems. However, since the carrier frequencies of the GPS signals are well known, the GPS receivers are vulnerable to intentional jamming attacks. To remove jammers but maintain GPS signals at the received signals, a popular technique is an adaptive beam steering method based on array antenna. Among adaptive beam steering techniques, this paper considers MVDR (minimum variance distortionless response) algorithm, and proposes a new adaptive technique that preserves the received signals at desired direction, but removes the jamming signals adaptively. The performance of the proposed method is verified through computer simulation.

• Journal of Korean Society of Transportation
• /
• v.31 no.1
• /
• pp.77-86
• /
• 2013

This paper focuses on the development of analytical models for estimating the changes in saturation flow rates (SFR) at the stop-lines of a signalized intersection due to the existence of nearby work-zones, and thereby calculating the prevailing capacity values for specific lane groups. Major changes were incorporated in the logics of previous models and significant revisions have been made to secure the accuracy and simplicity. Furthermore, much attention was paid to model validation by making comparisons to both extensive simulation results and empirical data from various sites. It was found that SFRs are highly sensitive to the location of work-zones, the distance to each work-zone from the stop-line of a concerned approach, the number of lanes open and closed, and the effective green time. Using such geometric and operating conditions that constitute work-zone environment, the proposed models successfully estimated SFR values with a miniscule margin of error.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.6
• /
• pp.545-554
• /
• 2000

Compton X-ray backscatter technique has been used to quantitatively assess the impact damage in quasi-isotropic laminated composites and to obtain a cross-sectional profile of impact-damaged laminated composites from the density variation of the cross section. An adaptive filter is applied to the Compton backscattering data for the reconstruction and noise reduction from many sources including quantum noise, especially when the SNR(signal-to-noise ratio) of the image is relatively low. A nonlinear reconstruction model is also proposed to overcome distortion of the Compton backscatter image due to attenuation effects, beam hardening, and irregular distributions of the fibers and the matrix in composites. Delaminations masked or distorted by the first few delaminations near the front surface are detected and characterized both in width and location, by application of an error minimization algorithm.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.5
• /
• pp.545-550
• /
• 2012

Steam generator is one of the major components of nuclear power plant and steam generator tubes are the pressure boundary between primary and secondary side, which makes them critical for nuclear safety. As the operating time of nuclear power plant increases, not only damage mechanisms but also scaled deposits on steam generator tubes are known to be problematic causing tube support flow hole blockage and heat fouling. The ability to assess the extent and location of scaled deposits on tubes became essential for management and maintenance of steam generator and eddy current bobbin data can be utilized to measure thickness of scale on tubes. In this paper, tube reference standards with various thickness of scaled deposit has been set up to provide information about the overall deposit condition of steam generator tubes, providing essential tool for steam generator management and maintenance to predict and prevent future damages. Also, methodology to automatically measure scale thickness on tubes has been developed and applied to field data to estimate overall scale amount.

• Journal of the Korean Magnetic Resonance Society
• /
• v.9 no.2
• /
• pp.138-154
• /
• 2005

Vanadium-incorporated aluminophosphate molecular sieve $VO^{2+}-SAPO-5$ was studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies to determine the vanadium structure and interaction with various adsorbate molecules. It was found that the main species at low concentration of vanadium is a monomeric vanadium units in square pyramidal or distorted octahedral coordination, both in oxidation state (IV) for the calcined hydrated material and in oxidation state (V) for the calcined material. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. It is suggested as a $VO(H_2O)_3^{2+}$ complex coordinated to two framework oxygen bonded aluminum. When calcined, hydrated $VO^{2+}-}SAPO-5$ is dehydrated at elevated temperature, a species loses its water ligands and transforms to $VO^{2+}$ ions coordinated to two framework oxygens (species B). Species B reduces its intensity, significantly after treatment with $O_2\;at\;600^{\circ}C$ for 5 h, thus suggesting oxidation of $V^{4+}\;to\;V^{5+}$. When dehydrated $VO^{2+}-SAPO-5$ contacts with $D_2O$ at room temperature, the EPR signal of species A is observed. Thus species assumed as a $VO^{2+}(O_f)_2(D_2O)_3$, by considering two framework oxygens. Adsorption of deuterated ethanol, propanol on dehydrated $VO^{2+}_{-}SAPO-5$ result in another new vanadium species E and F, respectively, which are identified as a $VO^{2+}-(CH_3CH_2OD)_3,\;VO^{2+}-(CH_3CH_2CH_2OD)_2$ complex. When deuterated benzene is adsorbed on dehydrated $VO^{2+}-SAPO-5$, another new vanadium species G, identified as a $VO^{2+}-(C_6D_6)$ is observed. Possible coordination geometries of these various complexes are discussed.

• Journal of Korea Multimedia Society
• /
• v.11 no.7
• /
• pp.1016-1024
• /
• 2008

In this paper, we designed and implemented the ACE(ACtive Emergency call service system) system for emergency call service actively. ACE system has two physical components; E-Device(Emergency Mobile Device) and E-Server(Emergency Server). The role of E-Device is the mobile device in order to call emergency by using mild handi-capped, the elderly and children who are able to communicate theirs intention to another. E-Server is the server for management E-devices with realtime monitering. E-Device will be developed to the portable size for easily mild handi-capped, the elderly and children. When they need the service of emergency call, the button of E-device can be used and the call signal is transmitted to the emergency office and the guardian through Internet and CDMA. E-server should be developed the integrated control system for management of E-Devices basically. And it also supported to realtime monitoring of E-devices with respect to high quality of emergency call service for rise the efficiency.

• Journal of Advanced Navigation Technology
• /
• v.17 no.3
• /
• pp.298-305
• /
• 2013

In this paper, we propose simple combining schemes for sensing ATSC digital television signals with spectral correlation density (SCD). The detection algorithms exploiting the cyclostationarity exhibited by the pilot of ATSC digital television signals usually use the SCD value at a given particular frequency. However, we found that non-zero SCDs are found to be distributed over a certain range of frequencies in multipath fading environment. To utilize a set of non-zero SCD values computed in the vicinity of the pilot location, we formulate a class of combining methods in analogy with the maximal ratio combining, the square law combining and the equal gain combining. We show that the proposed simple combining schemes improve the detection performance by 0.5~1.0dB under multipath fading environments.

• Journal of Korean Neurosurgical Society
• /
• v.39 no.3
• /
• pp.198-203
• /
• 2006

Objective : To evaluate the natural histories and growth rates of meningiomas, the authors perform this retrospective observational study and attempt to identify those factors predicting tumor growth. Methods : Between 1993 and 2004, a total of 83 patients were diagnosed by computed tomography[CT] scans or magnetic resonance[MR] imaging as having an intracranial meningioma, and were treated by observation only using regular clinical and radiological examinations. Twenty-six of these 83 patients, with available data were included in this study. Follow up periods ranged from 9 to 137 months [mean, 55.6 mo.; median, 60 mo.]. The tumor volumes, absolute growth rates, and tumor doubling times were calculated. Results : Patient age and sex distributions were comparable to those of other studies, but exceptionally 16 meningiomas [62%] were located at the skull base in the present study. During follow-up monitoring, the majority of meningiomas grew, though 77% showed low absolute annual growth rates [$<1cm^3/yr$]. The tumor doubling times ranged from 2.87 to 201.72 years [mean, 42.91 yr]. Based on Imaging analysis, peritumoral edema and the absence of calcification were probable factors predicting tumor growth. Tumor-related symptoms seemed to be slightly related to tumor growth. Other factors, e.g., gender, age, tumor location, and T2-weighted signal Intensities on MR imaging, were not significantly related to tumor growth. Conclusion : This study shows that the majority of meningiomas are slow growing. However, variations in tumor growth are unexplained, thus individualized optimal treatment strategies should be provided in each meningioma.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.154-154
• /
• 2019

Characterization of reliable field-scale root-zone soil moisture (RZSM) variability contribute to effective hydro-meterological monitoring. Although a promising cosmic-ray neutron probe (CRNP) holds the pontential for field-scale RZSM measurement, it is often restricted at deeper depths due to the non-unique sensitivity of CRNP-measured fast neutron signal to other hydrogen pools. In this study, a merging framework relied on coupling cosmic-ray soil moisture with a representative additional RZSM, was introduced to scale shallower CRNP effective depth to represent root-zone layer. We tested our proposed framework over a densely vegetated region in South Korea covering a network of one CRNP and nine in-situ point measurements. In particular, cosmic-ray soil moisture and ancillary RZSM retrieved from the most time stable location were considered as input datasets; whereas the remaining point locations were used to generate a reference RZSM product. The errors between these two input datasets and the reference were forecasted by a linear autoregressive model. A linear combination of forecasts was then employed to compute a suitable weight for merging two input products from the predicted errors. The performance of merging framework was evaluated against reference RZSM in comparison to the two original products and a commonly used exponential filter technique. The results of this study showed that merging framework outperformed other products, demonstrating its robustness in improving field-scale RZSM. Moreover, a strong relationship between the quality of input data and the performance merging framework in light of CRNP effective depth variation has been also underlined via the merging framework.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.1169-1177
• /
• 2008

The system of the railway signaling using the track transmits the approved speed to the location of a train and it. Referring to the way of transmitting train control information, there are the one transmitting it to the on-board system of a train using the direct track, the another transmitting it establishing an instrument, and the other transmitting an instrument by a railway track. The one is the method using the direct track as a conductor for composing the part of the track and attaining the information controlling a train by transmitting a signal to the track. It is used for the high-speed railway and the subway. The method using the track attains information by transmitting it to returned information, and the on-board system of a train attains it by magnetic coupling. Because many reinforcing bars on the concrete slab track are used, interaction between a rail and a reinforcing bar that is not produced on ballast track is made. Due to the interaction, the electric characteristic of rail is changed. In the current paper, we numerically computed the coupling coefficient between the rail and the reinforcing bar based on the concrete slab track throughout the model related to the rail and the reinforcing bar using the concrete slab track that is used in the second interval of the Gyeongbu high-speed railway, and we defined the coupling coefficient not changed in the electric characteristic of rail in the condition that there is no interaction between the rail and the reinforcing bar.