• Journal of KIISE
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• v.42 no.10
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• pp.1222-1230
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• 2015

Segmentation of the anterior cruciate ligament (ACL) in knee MRI remains a challenging task due to its inhomogeneous signal intensity and low contrast with surrounding soft tissues. In this paper, we propose a multi-atlas-based segmentation of the ACL in knee MRI with locally-aligned probabilistic atlas (PA) in an iterative graph cuts framework. First, a novel PA generation method is proposed with global and local multi-atlas alignment by means of rigid registration. Second, with the generated PA, segmentation of the ACL is performed by maximum-aposteriori (MAP) estimation and then by graph cuts. Third, refinement of ACL segmentation is performed by improving shape prior through mask-based PA generation and iterative graph cuts. Experiments were performed with a Dice similarity coefficients of 75.0%, an average surface distance of 1.7 pixels, and a root mean squared distance of 2.7 pixels, which increased accuracy by 12.8%, 22.7%, and 22.9%, respectively, from the graph cuts with patient-specific shape constraints.

• Journal of Astronomy and Space Sciences
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• v.19 no.4
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• pp.351-366
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• 2002

In this study, we developed low cost INS and (D)GPS integration for continuous attitude and position and utilized it for the determination of exterior orientation parameters of image sensors which are equipped in 4S-Van. During initial alignment process, the heading information was extracted from twin GPS and fine alignment with Kalman filter was performed for the determination of roll and pitch. Simulation and van test were performed for the performance analysis. Based on simulation result, roll and pitch error is around 0.01-0.03 degrees and yaw error around 0.1 degrees. Based on van test, position error in linear road is around 10 cm and curve around 1 m. Using direct georeferencing method, the image sensor's orientation and position information can be acquired directly from (D)GPS/INS integration. 4S-Van achieved 3D spatial data using (D)GPS/INS and image data can be applied to the spatial data integration and application such as contemporary digital map update, road facility management and Video GIS DB.

• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.384-389
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• 2002

A new idea of the wavelength locking module for DWDM application was investigated in the present research. Only one etalon photo-diode is generally used in the internal/external wavelength locking system. For the internal wavelength locking module with 50 GHz applications, an algle tuning method of the etalon commonly applied. However, the alignment process of the etalon with the angle tuning method is limited because the lock performance is extremely sensitive accoriding to the change of the tilting angle. In an optical viewpoint, the alignment tolerance of the locker module with the etalon PD array block was good, and the precise tuning of the wavelength was possible. The characteristics of free spectral range (FSR) and peak shift of wavelength according to the tilting angle with the locker module was investigated. For the present module, the optimized initial tilting angle was experimentally obtained.

• Korean Journal of Optics and Photonics
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• v.25 no.1
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• pp.29-37
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• 2014

We have studied and demonstrated general, systematic error-correction methods for a dual rotating quarter-wave plate ellipsometer. To estimate and correct 5 systematic error sources (three offset angles and two unexpected retarder phase delays), we used 11 of the 25 Fourier components of the ellipsometry signal obtained in the absence of an optical sample. Using these 11 Fourier components, we can determine the errors from the 5 sources with nonlinear optimization methods. We found systematic errors ${\epsilon}_3$, ${\epsilon}_4$, ${\epsilon}_5$) are more sensitive to the inverted Mueller matrix than retarder phase delay errors (${\epsilon}_1$, ${\epsilon}_2$) because of their small condition numbers. To correct these systematic errors we have found that error of any variety must be less than 0.05 rad. Finally, we can use the magnitudes of these errors to correct the Mueller matrix of optical components. From our experimental ellipsometry signals, we can measure phase delay and the rotational angular position of its fast axis for a half-wave plate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.464-470
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• 2000

In this paper, we introduce a modified interference cancellation scheme to overcome MAI(Multiple Access Interference) in DS-CDMA. Among ICs(Interference Cancellers), PIC(Parallel Interference Canceller) requires the more stages to have the better BER(Bit Error Rate), and SIC(Successive Interference Canceller) faces the problems of power reordering and large delays. To resolve the problems of them, we propose a modified interference cancellation scheme combining SIC and PIC. The proposed interference canceller has improved the performance through the total received signal applied sorting method is fed into the initial stage. Its structure extracts the good characteristics because of the input signal removed MAI in the initial stage. The characteristics of the proposed system are as follows (1) smaller delay, and the strongest user signal is also reduced to MAI(unlike SIC), (2) it has the good BER performance only using fewer stages (unlike PIC).

• Journal of Korea Multimedia Society
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• v.16 no.12
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• pp.1454-1464
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• 2013

In this paper, we propose a rapid rigid registration method for the fusion visualization of intra-operative 2D XA and pre-operative 3D CTA images. In this paper, we propose a global movement estimation based on a trilateration for the fast and robust initial registration. In addition, the principal axis of each image is generated and aligned, and the bounding box of the vascular shape is compared for more accurate initial registration. For the fine registration, two images are registered where the distance between two vascular structures is minimized by selective distance measure. In the experiment, we evaluate a speed, accuracy and robustness using five patients' data by comparing the previous registration method. Our proposed method shows that two volumes can be registered at optimal location rapidly, and robustly comparing with the previous method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.997-1003
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• 2012

GNSS and ARS are the most common sensors in low-end UAVs. However, these sensors are vulnerable to built-in errors and cannot measure the body heading independently. The GNSS/INS cannot fully compensate the IMU errors in initial alignment process and rectilinear flights. For an unmanned helicopter, a magnetometer can be more useful than any other sensors to obtain heading information. However, the electric motor which drives small helicopter UAV keeps the magnetometer from reading the pure magnetotelluric vector. This paper shows the effects of electric motor on the magnetometer readings, and presents a method to compensate the effects. The results are verified with flight test data. The simulation and experimental results in this paper proves that aiding GNSS/INS with magnetometer increases observability and improves accuracy.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.141-146
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• 2020

In brushless DC motors (BLDC), the on/off angle of the switch is determined by the optimal alignment of the stator and rotor, while switched reluctance motors (SRM) are complex parameters with many on/off angles of the switch. It appears as a function and therefore the switching angle is variable for optimal operation. Therefore, in order to operate the switched reluctance motor (SRM) optimally, the rotor position can be detected using a high resolution position sensor and a complicated additional circuit. In this paper, rotor position detection and related position detection circuits are applied and detected by using various sensors such as encoder, hall sensor and opto interrupter among several methods to drive switched reluctance motor (SRM). Also a study on securing the initial position of the rotor was conducted.

• Journal of Advanced Navigation Technology
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• v.23 no.3
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• pp.245-250
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• 2019

Inertial navigation system has navigation errors because of the error of inertial measurement unit (IMU) and misalignment over time. In order to solve this problem, aided navigation system is performed using global navigation satellite system (GNSS), speedometer, etc. The inertial navigation system equipped with underwater vehicle mainly uses speedometer and performed aided navigation because satellite signals do not pass through underwater. There are DVL, EM-Log, and RPM in the speedometer, and the sensors are applied according to the system environment. This paper describes velocity aided navigation using RPM of inertial navigation system operating in high speed and deep water environment. In addition, we proposes an algorithm to compensate the limit of RPM with straight direction and the current velocity error. There are results of monte-calo simulation to prove performance of the proposed algorithm.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.4
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• pp.517-526
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• 2019

In the present study, unsteady flows around a projectile ejected from an aircraft platform have been numerically investigated by using a three dimensional compressible RANS flow solver based on unstructured meshes. The relative motion between the platform and projectile was described by six degrees of freedom(6DOF) equations of motion with Euler angles and a chimera technique. Initial behavior of the projectile for varying conditions, such as roll and pitch-yaw command on the control surface of the projectile, flight Mach number, and platform pitch angle, was investigated. The ejection stability of the projectile was degraded as Mach number increases. In the transonic condition, the initial behavior of the projectile was found to be unstable as increase of platform pitch angle. By applying the command to control surfaces of the projectile, initial stability was highly enhanced. It was concluded that the proposed simulation data are useful for estimating the ejection behavior of a projectile in design phase.