• Journal of Positioning, Navigation, and Timing
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• v.13 no.3
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• pp.245-256
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• 2024

Following the introduction of civilian navigation, the commercial Global Navigation Satellite System (GNSS) receivers' market has been expanding in various fields such as autonomous driving and smart cities. With improved receiver performance and widespread use of GNSS, the configurations of base and rover receivers are becoming more complex. As a result, user must consider combinations of base stations with different qualities, costs, and performances. To address these issues, we conducted zero-baseline tests to analyze the double-differenced code-pseudorange noise of various receiver combinations, ranging from low- to high-cost. The results showed that the noise varied depending on the receiver combination. Notably, receivers from the same manufacturer exhibited similar noise and positioning errors despite significant price differences. We also found that the double-differenced noise of all receiver combinations was correlated with the Carrier-to-Noise Density Ratio (C/N0), the satellite elevation angle, and the Doppler shift, and it did not perfectly follow a normal distribution. Further analysis based on Modified Allan Deviation (MDEV) showed that different types of noise were observed for each receiver combination and the double-differenced noise and positioning errors have similar statistical characteristics. From this study, the importance of receiver combinations and their various characteristics can be better understood.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.92-97
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• 2005

In this study, the effect of contact angles of PDMS and external voltage has been investigated. SU-8 (Microchem, USA) negative photoresist and PDMS are used to make the microchannel. The contact angle of the native PDMS is $105^{\circ}$. The native PDMS is treated with the oxygen plasma and the contact angle changes $19^{\circ}$, $46^{\circ}$ and $69^{\circ}$. As a result, the rate of increase in flow velocity is not directly proportional to the rate of increase of external voltage. This is because the electrical double layer is condensed and the zeta potential is increased with an increase of the external voltage. The flow velocity is highest for the contact angle of $19^{\circ}$ at the same external voltage. Hence we conclude that the thickness of electrical double layer and flow velocities vary with contact angle at the same external voltage.

• Imaging Science in Dentistry
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• v.31 no.4
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• pp.209-214
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• 2001

Purpose: To investigate the ability of double TMJ view by multifunctional panorama to view the bony components and the space of the temporomandibular joint. Materials and Methods: Ten dry skulls fitted with resin shims over the articular surface of the condyle were used to reproduce the temporomandibular joint space. Fine metal wires were attached to the three portions of contours of the condylar head and the articular eminence. With 10 dry skulls and 20 cases having TMJ dysfunction, double TMJ views by multifunctional panorama (Planmeca 2002 Proline CC) and transcranial views were taken, analyzed from the anatomical view point, and compared statistically in view of the widths of the posterior joint space and the condylar head. Results: In double TMJ view, the supero-anterior part of the condyle represented the lateral 1/3, the most superior part represented center portion, and the posterior part medial l/3 of the condyle. In maximum mouth opening, no other structures were superimposed with the condyle in double TMJ view. In double TMJ view, petrous bone was moderately superimposed with the superior part of the condyle and the posterior increment of angle exposure made wider the images of the articular eminence and the condyle. The tendency of reduction in the posterior joint space appeared in the side of TMJ dysfunction compared with the normal side. The posterior joint spaces in double TMJ view were statistically wider (p<0.05) than those in transcranial view. The correlation coefficient was 0.5179 between the widths of the posterior joint spaces in two radiographic views. Conclusions: Double TMJ view can be substituted for transcranial view in evaluating the TMJ dysfunction.

• 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.

• Journal of the Korean Solar Energy Society
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• v.25 no.1
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• pp.57-64
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• 2005

The present society have been polluted the earth environment by the rapid industrial growth. So, the meaning of sustainable development is doing more important. Therefore the technology skills of sustainable architecture techniques have been studied many-side of energy as like energy saving and substitutive energy. But, See the studies until now, there have been just one system either energy saving or substitutive energy. So, the paper studies about energy saving system with substitutive energy system(the double-skin facade system with PV modules) and presents the performance of system through the analysis of reduction of the energy load, the solar radiation on the slope angle of PV module, the blind effect in system.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.257-260
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• 1997

In this paper, the double inverted pendulum having a single actuator is built and the controller for the system is proposed. The lower link is hinged on the plate to free for rotation in the x-z plane. The upper link is connected to the lower link through a DC motor. The double inverted pendulum built can be kept upright posture by controlling the position of the upper link even though the proposed inverted pendulum has no actuator in lower hinge. The algorithm to control the inverted pendulum is consisted of a state feedback controller within a linearizable range and a fuzzy logic controller coupled with a feedback linearization control for the rest of the range. Concept of the virtual work is employed to drive the linearlized model for the state feedback controller. The feedback linearization controller drives a DC motor with the modified reference joint angle from the fuzzy controller which adjusts a upright posture of a proposed pendulum system. Finally, the experiments are conducted to show the validity of the proposed controller.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.220-224
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• 2003

This is a preliminary study is to make the robot walk more stably by observing the ZMP (Zero Moment Point) of the robot when the robot stands on one leg(single support) and then on two legs(double support) and so on. The robot consists of nine DOF (Degree of freedom) with lower part of the body. It is equipped with motor drivers and force sensors inside the robot. The motors are controlled by the external PC (Intel pentium 4). By the experimental results, it is found that the robot is unstable in the instant of changing from single support to double support or from double support to single support. We use the trajectory compensation of the angle and the length of both legs to realize more stable walking.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.492-494
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• 1996

This paper describes a study on the series resonant inverter using the double full-bridge, and the output voltage of the proposed inverter is controlled by phase shift angle of the outputs of two inverters. These control schemes can be reduce the switching loss and EMI, etc, which the inverter is drived by auto following control of output frequency, because it is impossible for switching devices to be always turned on and off at zero voltage or zero current. Theoretical characteristics of the proposed double inverter circuit are compared with Pspice simulation and experimental results.

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.24-27
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• 1999

This paper proposed a method to reduce torque ripple of double-layer axial flux permanent magnet motor. Torque is generated by interacting between current of stator winding and airgap flux. In the case of slotless axial flux permanent magnet motor, only commutation torque component is significant. Hence, cogging and reluctance torque will not be considered. For this propose, we were supplied differential phase current in each winding and shifted rotor magnet. According to shifted rotor magnet and flux and phase of current were shifted, phase of developed torque in each side is difference. As a result, we could reduce the total torque ripple in motor and obtain minimum torque ripple in the case of 7.5 degree shifting angle between two rotors.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.2
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• pp.69-76
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• 1994

An effective method for reducing the harmonics in double connected modified current source inverter[MCSI] by switching taps on auto transformer is presented in this paper. The proposed system operates as like a 24 step MCSI by adding only tap changing auxiliary circuit which consists of several taps and static switching elements to the 12 step multiple inverter, which is double connected three-phase six-step MCSI with an auto transformer. The basic theories of the proposed inverter systems for analyzing the output waveforms are described. And to optimize the effectiveness of the harmonic reduction, the optimum turn ratio and the tap changing control angle of auto transformer are decided by digital simulation and its validity is verified by experiment. Although the construction of the proposed inverter is very simple, it is clarified that the output waveform of the inverter is almost the same as that of the conventional 24 step multiple inverter under the optimum condition.