• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.6
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• pp.26-37
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• 2001

In order to improve the several problems of the general backpropagation, we propose a method using a fuzzy logic system for automatic tuning of the activation function gain in the backpropagation. First, we researched that the changing of the gain of sigmoid function is equivalent to changing the learning rate, the weights, and the biases. The inputs of the fuzzy logic system were the sensitivity of error respect to the last layer and the mean sensitivity of error respect to the hidden layer, and the output was the gain of the sigmoid function. In order to verify the effectiveness of the proposed method, we performed simulations on the parity problem, function approximation, and pattern recognition. The results show that the proposed method has considerably improved the performance compared to the general backpropagation.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.2
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• pp.73-78
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• 2011

A frequency synthesizer for DAB applications is designed using $0.18{\mu}m$ CMOS process with 1.8V supply. NP-core type is chosen for VCO core to improve low power characteristic and symmetric characteristic of output waveform. VCO range is 1302.34 MHz - 1949.51 MHz using switchable capacitor bank and varactor bank. Varactor biases that improve varactor capacitance characteristics were minimized as two, $K_{vco}$(VCO gain) is maintained using technique of varactor bank switching. Intervals of $K_{vco}$ are maintained adding VCO frequency compensation logic. Each block of VCO and frequency synthesizer designed $0.18{\mu}m$ CMOS process with 1.8V supply is verified by Cadence Spectre, measured VCO consumes 9mA current, and is 39.8% tuning range, total power consumption of the frequency synthesizer is 18mW.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.580-587
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• 2003

In this paper, we introduce a novel model to analyze the linearity of a TW-EAM (traveling-wave electroabsorption modulator). The device length, microwave loss (ML), and internal reflection (IR) due to impedance mismatch have effect on the linearity of a TW-EAM. The longer devices have characteristics of lower biases with minimum IMDS (intermodulation distortions). ML decreases the output power as well as the IMD value. Internal reflection has different nonlinear characteristics according to the wavelength of the input frequency and the device length. There is little change in SFDR (spurious-free dynamic range) due to ML or IR. As a result, for a 50 GHz band RF-optical communication system, a 0.8 mm-long TW-EAM with the lowest ML would have better properties by using n, which is caused by impedance, mismatch at the output port.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.2
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• pp.159-167
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• 2009

To obtain the gravity data with consistent quality and good distribution over Korea, to overcome the difficulties in constructing precision geoid from biased distribution of ground data, to resolve the discrepancy between the ground and ocean gravity data, an airborne gravity survey was conducted from Dec. 2008 to Jan. 2009. The data was measured at the average flying height of 3,000m and the data with cross-over error of 2.21mGal is obtained. The geoid constructed using this airborne gravity data shows the range of 9.34 $\sim$ 33.88m. Comparing the geoid with respect to the GPS/levelling data, a precision of 0.145m is obtained. After fitting, the degree of fit to GPS/levelling data was calculated about 5cm. It was found that there exists large biases in the area of south-western and northern part of the peninsular which is considered to be the effect of distorted vertical datum in Korea. Thus, more investigation on vertical datum would be needed in near future.

• Journal of Korean Society of Archives and Records Management
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• v.11 no.1
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• pp.231-252
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• 2011

User needs and their usage motivations are critical components of web portal success, yet limited studies have been conducted with the constituents of good cultural heritage archive portals from the user perspective. This study proposes a quality assessment model from the user perspective. To overcome the intrinsic biases, the triangulation approach was chosen for building a research model. The proposed research model adapts three existing web portal quality models: service quality model, data quality model, and technology acceptance model. A 99-item instrument is suggested to investigate the proposed model. In the next phase of research, the instrument will be tested for its construct validity, and the research model will be empirically tested.

• Journal of the Korean Data and Information Science Society
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• v.17 no.3
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• pp.889-904
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• 2006

Our purpose is to ascertain, if possible, whether atomic bomb survivors with cataracts and epilation were more radiosensitive than those survivors with cataracts but without epilation. A major ophthalmologic survey was conducted in Hiroshima and Nagasaki in 1963-64. At that time, 2125 individuals were examined. Among these individuals, estimated eye organ doses, based on the DS86 dosimetry system, and information on the occurrence of epilation within the first 60 days following the bombings are available on 1742. In the analysis of these data we have assumed that each individual represents a sample of one from a binomial distribution, and that the occurrence of cataracts and epilation are independent biological phenomena. We got following results. The threshold for cataract induction and its 95% confidence limits have been estimated from data on the occurrence of cataract and epilation. Among the 1742 study subjects, 40 had both cataracts and severe epilation. The estimated threshold based on these cases is 0.98 sievert(Sv), with 95% lower and upper confidence bounds of 0.72, and 1.32 Sv, respectively, and is highly statistically significant. Among the 27 cases of cataracts where severe epilation was not reported, the estimated threshold is 1.74 Sv with 95% lower and upper confidence bounds of 1.21 Sv, and "not estimable". The difference between these two estimates is not statistically significant although the effect of dose is highly significant in both instances. The potential importance of biases in the DS86 dose estimates is discussed. The difference between the threshold estimated from cataract cases with epilation and that from cases without epilation is not statistically significant at the 5% or 10% level, and thus affords no support for the notion of increased radiosensitivity.

• Journal of Dental Anesthesia and Pain Medicine
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• v.18 no.2
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• pp.97-103
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• 2018

Background: Respiration monitoring is necessary during sedation for dental treatment. Recently, acoustic respiration rate ($RRa^{TM}$), an acoustics-based respiration monitoring method, has been used in addition to auscultation or capnography. The accuracy of this method may be compromised in an environment with excessive noise. This study evaluated whether noise from the ultrasonic scaler affects the performance of RRa in respiratory rate measurement. Methods: We analyzed data from 49 volunteers who underwent scaling under intravenous sedation. Clinical tests were divided into preparation, sedation, and scaling periods; respiratory rate was measured at 2-s intervals for 3 min in each period. Missing values ratios of the RRa during each period were measuerd; correlation analysis and Bland-Altman analysis were performed on respiratory rates measured by RRa and capnogram. Results: Respective missing values ratio from RRa were 5.62%, 8.03%, and 23.95% in the preparation, sedation, and scaling periods, indicating an increased missing values ratio in the scaling period (P < 0.001). Correlation coefficients of the respiratory rate, measured with two different methods, were 0.692, 0.677, and 0.562 in each respective period. Mean capnography-RRa biases in Bland-Altman analyses were -0.03, -0.27, and -0.61 in each respective period (P < 0.001); limits of agreement were -4.84-4.45, -4.89-4.15, and -6.18-4.95 (P < 0.001). Conclusions: The probability of missing respiratory rate values was higher during scaling when RRa was used for measurement. Therefore, the use of RRa alone for respiration monitoring during ultrasonic scaling may not be safe.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.255-260
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• 2006

Safety-critical navigation systems have to provide 'reliable' position solutions, i.e., they must detect and exclude measurement or system faults and estimate the uncertainty of the solution. To obtain more accurate and reliable navigation systems, various filtering methods have been employed to reduce measurement noise level, or integrate sensors, such as global navigation satellite system/inertial navigation system (GNSS/INS) integration. Recently, particle filters have attracted attention, because they can deal with nonlinear/non-Gaussian systems. In most GNSS applications, the GNSS measurement noise is assumed to follow a Gaussian distribution, but this is not true. Therefore, we have proposed a fault detection and exclusion method using particle filters assuming non-Gaussian measurement noise. The performance of our method was contrasted with that of conventional Kalman filter methods with an assumed Gaussian noise. Since the Kalman filters presume that measurement noise follows a Gaussian distribution, they used an overbounded standard deviation to represent the measurement noise distribution, and since the overbound standard deviations were too conservative compared to the actual distributions, this degraded the integrity-monitoring performance of the filters. A simulation was performed to show the improvement in performance of our proposed particle filter method by not using the sigma overbounding. The results show that our method could detect smaller measurement biases and reduced the protection level by 30% versus the Kalman filter method based on an overbound sigma, which motivates us to use an actual noise model instead of the overbounding or improve the overbounding methods.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.103-107
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• 2006

At present, most efforts tend to develop a INS which is only based linear accelerometers, because of the low cost micro-machining gyroscopes lack of the accuracy needed for precise navigation application and possible achieving the required levels of precise for micro-machining accelerometer. Although it was known in theory that a minimum of six accelerometers are required for a complete description of a rigid body motion, and any configuration of six accelerometers (except for a "measure zero " set of six-accelerometer schemes) will work. Studies on the feasible configuration of GF-INS indicate that the errors of angular velocity resolved from the six accelerometers scheme are diverged with time or have multi solutions. The angular velocity errors are induced by the biases together with the position vectors of the accelerometers, therefore, in order to treat with the problem just mentioned, researchers have been doing many efforts, such as the extra three accelerometers or the magnetometers may be taken as the reference information, the extended Kalman filter (EKF) involved to make the angular velocity errors bound and be estimated, and so on. In this paper, the typical configurations of GF-INS are introduced; for each type GF-INS described, the solutions to the angular velocity and the specific force are derived and the characteristic is indicated; one of the corresponding extend Kalman filters are introduced to estimate the angular errors; parts of the simulation results are presented to verify the validity of the equations of angular velocity and specific force and the performance of extend Kalman filter.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.535-540
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• 2006

The relationship between the observable noise model and the satellite elevation angle can be modeled quite well by an exponential function.[Jin, 1996] Noise size and dependence on the elevation angle are, however, different for each observation and receiver type. Therefore, the coefficient determination of this model is an issue, and various methods including PR-CP, single difference, and time difference have been suggested. The limitations of them are difficulty to model the carrier phase noise and to eliminate bias. To overcome these disadvantages for using Jin's model, we suggest zero baseline double difference (DD) and noise sorting algorithm. Data DD technique in zero baseline is useful to eliminate all the troublesome GPS biases, and the remaining error is the sum of GPS measurement noises from two satellites. These DD residuals for hours should be sorted by the combination of satellite elevation angles, and then variance value of the residual for each combination can be estimated. Using these values, we construct an over-determined linear equation whose solution is a set of noise variance for each satellite elevation angle. With 24hr Trimble 4000ssi data, we easily worked out the coefficients of the noise model not only for pseudorange but also for carrier phase. We estimated the standard deviation of the measurement DD using our model, and plotted 1 and 3 sigma lines for every epoch to verify the representation of the residual error. 63.3% of pseudorange residual and 65.9% of phase error did not exceed the 1 sigma lines. Additionally, 99.2% and 99.5% of them lied within 3sigma line. These figures prove that the Gaussian property of measurement noise, and that the suggested model by our algorithm corresponds to the observable noise information.