• Korean Journal of Optics and Photonics
• /
• v.22 no.5
• /
• pp.207-213
• /
• 2011

We propose a new method to measure the phase errors of an AWG(arrayed waveguide grating) through Monte-Carlo analysis. In the frequency domain method, we used the Monte-Carlo method to fit the theory to the experimental results. The phase and amplitude values are obtained from the fitted theory. To verify our method, we carried out a simulation. Some phase errors were included to make a virtual interferogram and we measured the actual AWG phase errors from it by our method. The results show that our method gives good results if the laser tuning range is larger than 1.7 times of the AWG FSR(free spectral range) and if the phase errors are within ${\pm}50^{\circ}$.

• The Journal of Korean Society for Radiation Therapy
• /
• v.24 no.1
• /
• pp.23-30
• /
• 2012

Purpose: There was a problem with using MU verification programs for the reasons that there were errors of MU when using MU verification programs based on Pencil Beam Convolution (PBC) Algorithm with radiation treatment plans around lung using Analytical Anisotropic Algorithm (AAA). On this study, we studied the methods that can verify the calculated treatment plans using AAA. Materials and Methods: Using Eclipse treatment planning system (Version 8.9, Varian, USA), for each 57 fields of 7 cases of Lung Stereotactic Body Radiation Therapy (SBRT), we have calculated using PBC and AAA with dose calculation algorithm. By developing MU of established plans, we compared and analyzed with MU of manual calculation programs. We have analyzed relationship between errors and 4 variables such as field size, lung path distance of radiation, Tumor path distance of radiation, effective depth that can affect on errors created from PBC algorithm and AAA using commonly used programs. Results: Errors of PBC algorithm have showned $0.2{\pm}1.0%$ and errors of AAA have showned $3.5{\pm}2.8%$. Moreover, as a result of analyzing 4 variables that can affect on errors, relationship in errors between lung path distance and MU, connection coefficient 0.648 (P=0.000) has been increased and we could calculate MU correction factor that is A.E=L.P 0.00903+0.02048 and as a result of replying for manual calculation program, errors of $3.5{\pm}2.8%$ before the application has been decreased within $0.4{\pm}2.0%$. Conclusion: On this study, we have learned that errors from manual calculation program have been increased as lung path distance of radiation increases and we could verified MU of AAA with a simple method that is called MU correction factor.

• Journal of Biomedical Engineering Research
• /
• v.36 no.5
• /
• pp.169-176
• /
• 2015

Implantable closed-loop epilepsy controllers require ideally both accurate epileptic seizure detection and low power consumption. On-chip oscillators can be used in implantable devices because they consume less power than other oscillators such as crystal oscillators. In this study, we investigated the tolerable error range of a lower power on-chip oscillator without losing the accuracy of seizure detection. We used 24 ictal and 14 interictal intracranial electroencephalographic segments recorded from epilepsy surgery patients. The performance variations with respect to oscillator frequency errors were estimated in terms of specificity, modified sensitivity, and detection timing difference of seizure onset using Generic Osorio Frei Algorithm. The frequency errors of on-chip oscillators were set at ${\pm}10%$ as the worst case. Our results showed that an oscillator error of ${\pm}10%$ affected both specificity and modified sensitivity by less than 3%. In addition, seizure onsets were detected with errors earlier or later than without errors and the average detection timing difference varied within less than 0.5 s range. The results suggest that on-chip oscillators could be useful for low-power implantable devices without error compensation circuitry requiring significant additional power. These findings could help the design of closed-loop systems with a seizure detector and automated stimulators for intractable epilepsy patients.

• Speech Sciences
• /
• v.15 no.3
• /
• pp.203-217
• /
• 2008

The number of Asian women immigrants in Korea is getting bigger and it's important to note that their communication problem in Korean causes not only the difficulty of adapting to Korean society but their children's speech-language disorder. To date there is little research on their acoustics characters and articulatory errors. Therefore, this study focuses on acoustic characters and articulatory error patterns of the women immigrants from Japan and Philippine based on the theory of "contrastive analysis". The subjects were 16 Japanese women immigrants(age: 42.5$\pm$4.4) and 14 Philippine women immigrants(age: 31.64$\pm$6.7) and control group consisted of 10 Korean women(age: 28.3$\pm$1.2). Speech and hearing of all subjects and control group were within normal limits. Speech samples were analyzed in a computer using CSL and data analysis was done on FFT widow for F1, F2, F3 of vowels and on wideband spectrogram for VOT of plosives and africatives. The results of this study were like this; For Japanese women immigrants, they had different articulatory patterns of /e/, /a/, /u/, /o/, /$\varepsilon$/, /m/ from those of Koreans and showed articulatory errors on the fortis and aspirated sounds. The reason is Japanese has only two distinctive characters for plosives and affricates; voicing and voiceless. The Philippine women immigrants also showed the same error patterns as the Japanese women immigrants. Especially the errors on aspirated sounds were prominent because their mother tongue has no distinctive characters about aspirated sounds. For vowels, they showed errors of /a/, /o/, /c/.

• Korean Journal of Ophthalmology
• /
• v.32 no.6
• /
• pp.497-505
• /
• 2018

Purpose: To evaluate and compare published methods of calculating intraocular lens (IOL) power following myopic laser refractive surgery. Methods: We performed a retrospective review of the medical records of 69 patients (69 eyes) who had undergone myopic laser refractive surgery previously and subsequently underwent cataract surgery at Samsung Medical Center in Seoul, South Korea from January 2010 to June 2016. None of the patients had pre-refractive surgery biometric data available. The Haigis-L, Shammas, Barrett True-K (no history), Wang-Koch-Maloney, Scheimpflug total corneal refractive power (TCRP) 3 and 4 mm (SRK-T and Haigis), Scheimpflug true net power, and Scheimpflug true refractive power (TRP) 3 mm, 4 mm, and 5 mm (SRK-T and Haigis) methods were employed. IOL power required for target refraction was back-calculated using stable post-cataract surgery manifest refraction, and implanted IOL power and formula accuracy were subsequently compared among calculation methods. Results: Haigis-L, Shammas, Barrett True-K (no history), Wang-Koch-Maloney, Scheimpflug TCRP 4 mm (Haigis), Scheimpflug true net power 4 mm (Haigis), and Scheimpflug TRP 4 mm (Haigis) formulae showed high predictability, with mean arithmetic prediction errors and standard deviations of $-0.25{\pm}0.59$, $-0.05{\pm}1.19$, $0.00{\pm}0.88$, $-0.26{\pm}1.17$, $0.00{\pm}1.09$, $-0.71{\pm}1.20$, and $0.03{\pm}1.25$ diopters, respectively. Conclusions: Visual outcomes within 1.0 diopter of target refraction were achieved in 85% of eyes using the calculation methods listed above. Haigis-L, Barrett True-K (no history), and Scheimpflug TCRP 4 mm (Haigis) and TRP 4 mm (Haigis) methods showed comparably low prediction errors, despite the absence of historical patient information.

• Journal of Biosystems Engineering
• /
• v.25 no.5
• /
• pp.415-420
• /
• 2000

It is very difficult to mechanize tomato harvesting because identifying a target tomato which is partly covered by leaves and stalks is not easy. This research was conducted to develop tomato harvesting robot which can identifying a target tomato, determining its dimensional position, and harvesting it in a limited time. Followings were major findings in this study. The first visual system of the robot was composed of two CCD cameras, however, which could not detect tomato not placed on the center of lens and partly covered by leaves or stalks. Secondary visual device, combined with two cameras and pan tilting was designed which could decreased the positioning errors within $\pm$10mm but still not enough for covered tomato by any obstacles. Finally, laser detector was added to the visual system that could reduce the position detecting errors within 10mm in X-Y direction and 5mm in Z direction for the covered tomatoes.

• Korean Journal of Optics and Photonics
• /
• v.14 no.1
• /
• pp.58-64
• /
• 2003

In order to read correct data from a disk-type holographic storage medium, it is very important to implement a servo-control in the pick-up module, as in a conventional CD-ROM. We propose a novel servo-control method using a glass plate on the optical axis, which is able to compensate the mechanical errors coming from wobbling of holographic disk and spindle motor. By rotating the glass plate within $\pm$10 degrees, we can reduce the reading errors of $\pm$200 ${\mu}{\textrm}{m}$ to $\pm$15 ${\mu}{\textrm}{m}$.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.769-772
• /
• 2005

Five DOF motion errors of a hydrostatic bearing table driven by the coreless type linear motor were compensated utilizing the active controlled capillaries in this study. Horizontal linear motion and yaw error were simultaneously compensated using two active controlled capillaries and vertical linear motion, pitch and yaw error were also simultaneously compensated using three active controlled capillaries. By the compensation, horizontal linear motion accuracy and yaw were improved from 0.16 ${\mu}m$ and 1.96 arcsec to 0.02 ${\mu}m$ and 0.03 arcsec. Vertical linear motion accuracy, pitch and roll were also largely improved from 0.18 ${\mu}m$, 2.26 arcsec and 0.14 arcsec upto 0.03 ${\mu}m$, 0.07 arcsec and 0.02 arcsec. The compensated motion errors were within the range of measuring repeatability which was ${\pm}0.02\;{\mu}m$ in the linear motion and ${\pm}0.05$ arcsec in the angular motion. From these results, it is found that the motion error compensation method utilizing the active controlled capillaries are very effective to improve the five motion accuracies of the hydrostatic bearing tables.

• Journal of Biosystems Engineering
• /
• v.25 no.3
• /
• pp.233-240
• /
• 2000

A commercially available Doppler radar was modified and evaluated for on-board monitoring of ground speed. The radar output was corrected for pitch angle of aircraft based on the output of an electrolytic tilt sensor. The effects of aircraft speed, height and mounting angle on error in the ground speed were evaluated. The speed error decreased with an increase of the mounting angle since the radar contact angle with respect to the ground approached to the mounting angle. The error increased with an increase of the nominal aircraft speed. The altitude insignificantly affected the speed error. The Doppler radar provided acceptable percent errors within 5% in most measurements. The error can be reduced within ${\pm}$1.5% by increasing the mounting angle ($43^{\circ}$). The error of -3.8% at the mounting angle of $29^{\circ}$could be reduced by adjusting the mounting angle with respect to the radar contact angle.

• Journal of Biosystems Engineering
• /
• v.21 no.3
• /
• pp.283-292
• /
• 1996

Automatic guidance of farm tractors would improve productivity by reducing operator fatigue and increasing machine performance. To control tractors within $\pm$5cm of the desired path, fuzzy and adaptive steering controllers were developed to evaluate their characteristics and performance. Two input variables were position and yaw errors, and a steering command was fed to tractor model as controller output. Trapezoidal membership functions were used in the fuzzy controller, and a minimum-variance adaptive controller was implemented into the 2-DOF discrete-time input-output model. For unit-step and composite paths, a dynamic tractor simulator was used to test the controllers developed. The results showed that both controllers could control the tractor within $\pm$5cm error from the defined path and the position error of tractor by fuzzy controller was the bigger of the two. Through simulations, the output of self-tuning adaptive controller was relatively smooth, but the fuzzy controller was very sensitive by the change of gain and the shape of membership functions. Contrarily, modeling procedure of the fuzzy controller was simple, but the adaptive controller had very complex procedure of design and showed that control performance was affected greatly by the order of its model.