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Jeongmin Lee,Sangwook Lee,Wooram Jung,Guk Bae Kim,Taehun Kim,Jiwon Seong,장혜민,Young Noh,Na Kyung Lee,Boo Rak Lee,Jung-Il Lee,Soo Jin Choi,Wonil Oh,Namkug Kim,Seunghoon Lee,Duk L. Na 대한의학회 2022 Journal of Korean medical science Vol.37 No.31
Background: To deliver therapeutics into the brain, it is imperative to overcome the issue of the blood-brain-barrier (BBB). One of the ways to circumvent the BBB is to administer therapeutics directly into the brain parenchyma. To enhance the treatment efficacy for chronic neurodegenerative disorders, repeated administration to the target location is required. However, this increases the number of operations that must be performed. In this study, we developed the IntraBrain Injector (IBI), a new implantable device to repeatedly deliver therapeutics into the brain parenchyma. Methods: We designed and fabricated IBI with medical grade materials, and evaluated the efficacy and safety of IBI in 9 beagles. The trajectory of IBI to the hippocampus was simulated prior to surgery and the device was implanted using 3D-printed adaptor and surgical guides. Ferumoxytol-labeled mesenchymal stem cells (MSCs) were injected into the hippocampus via IBI, and magnetic resonance images were taken before and after the administration to analyze the accuracy of repeated injection. Results: We compared the planned vs. insertion trajectory of IBI to the hippocampus. With a similarity of 0.990 ± 0.001 (mean ± standard deviation), precise targeting of IBI was confirmed by comparing planned vs. insertion trajectories of IBI. Multiple administrations of ferumoxytol-labeled MSCs into the hippocampus using IBI were both feasible and successful (success rate of 76.7%). Safety of initial IBI implantation, repeated administration of therapeutics, and long-term implantation have all been evaluated in this study. Conclusion: Precise and repeated delivery of therapeutics into the brain parenchyma can be done without performing additional surgeries via IBI implantation.
Noise Suppression of Spectrum-Sliced WDM-PON Light Sources Using FP-LD
Wooram Lee,김봉규,김병휘,Seung-Hyun Cho,Jaedong Park 한국전자통신연구원 2005 ETRI Journal Vol.27 No.3
We improved the performance of the spectrum-sliced light source for wavelength-divisionmultiplexed passive optical networks by employing a Fabry-Perot laser diode (FP-LD). We found that FP-LDs can suppress the intensity noise as significantly as using a gainsaturated semiconductor optical amplifier. The transmission characteristics were measured and analyzed both with and without employing an FP-LD.
Design and Layout of CMOS interface circuit for measuring photoplethysmogram
WooRam Lee,WanJik Lee,ChangSoo Won,SangHee Son,WonSup Chung,KyoungRok Cho 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
A CMOS interface circuit for measuring PPG(Photoplethysmogram) is proposed and designed by using current-control Schmitt trigger in this paper,. This circuit detects the blood beat using PPG which occurs in bloodbeat sensor and composed of analog and digital parts. Current signal of sensor is converted into voltage in analog parts and then converted into digital signal in digital parts. Compared to the conventional method, operation speed is increased and linear error is diminished by applying OTA(Operational transconductance amplifier) to Schmitt trigger circuit and oscillator. Also, proposed and designed circuit has some features of low power consumption, simple structure and high resolution compared with previous method.
Neural Network Compensation for Frequency Cross-Talk in Laser Interferometry
LEE, Wooram,HEO, Gunhaeng,YOU, Kwanho The Institute of Electronics, Information and Comm 2009 IEICE transactions on fundamentals of electronics, Vol.92 No.2
<P>The heterodyne laser interferometer acts as an ultra-precise measurement apparatus in semiconductor manufacture. However the periodical nonlinearity property caused from frequency cross-talk is an obstacle to improve the high measurement accuracy in nanometer scale. In order to minimize the nonlinearity error of the heterodyne interferometer, we propose a frequency cross-talk compensation algorithm using an artificial intelligence method. The feedforward neural network trained by back-propagation compensates the nonlinearity error and regulates to minimize the difference with the reference signal. With some experimental results, the improved accuracy is proved through comparison with the position value from a capacitive displacement sensor.</P>
Improved Measurement Accuracy of a Laser Interferometer: Extended Kalman Filter Approach
LEE, Wooram,KIM, Dongkyun,YOU, Kwanho The Institute of Electronics, Information and Comm 2010 IEICE transactions on fundamentals of electronics, Vol.93 No.10
<P>In this paper a nonlinearity compensation algorithm based on the extended Kalman filter is proposed to improve the measurement accuracy of a heterodyne laser interferometer. The heterodyne laser interferometer is used for ultra-precision measurements such as those used in semiconductor manufacturing. However the periodical nonlinearity property caused by frequency-mixing restricts the accuracy of the nanometric measurements. In order to minimize the effect of the nonlinearity, the measurement process of the laser interferometer is modeled as a state equation and the extended Kalman filtering approach is applied to the process. The effectiveness of our proposed algorithm is demonstrated by comparing the results of the algorithm with experimental results for the laser system.</P>
Frequency detuning effects in a loop-back WDM-PON employing gain-saturated RSOAs
Wooram Lee,Seung Hyun Cho,Mahn Yong Park,Jie Hyun Lee,Kim, C.,Geon Jeong,Byoung Whi Kim IEEE 2006 IEEE photonics technology letters Vol.18 No.13-16
<P>We report that, in a loop-back wavelength-division-multiplexed passive optical network link with gain-saturated reflective semiconductor optical amplifiers, the upstream performance is strongly affected not only by the gain saturation but also by the selective spectral filtering caused by the frequency difference between the optical downstream signal and the cascaded filter's passband. We experimentally investigate these effects and propose to use an additional negatively detuned optical filter at an optical network terminal to improve the upstream transmission performance</P>
Development of a compact thermoelectric generator consisting of printed circuit heat exchangers
Lee, Wooram,Lee, Jaeyoung Elsevier 2018 Energy conversion and management Vol.171 No.-
<P><B>Abstract</B></P> <P>Printed circuit heat exchangers (PCHEs) are employed to improve the compactness of a thermoelectric generator (TEG). PCHEs allows miniaturization of the heat exchanger without excessive additional cost, and permit high temperature and pressure (up to 1100 K and 600 bar) of working fluid, which enable high thermoelectric conversion efficiency. To investigate the pressure loss and thermal resistance of a PCHE in detail, three-dimensional computational fluid dynamic (CFD) analysis is conducted. Experimental results of the proposed TEG with PCHEs are newly presented. The TEG provides power density of 233.1 kW/m<SUP>3</SUP> at inlet temperatures of 448.15 K (hot side) and 293.15 K (cold side), which is the highest value in literature for a low-temperature TEG (<505.15 K hot side). Based on the models of friction and heat transfer in a PCHE validated by the experiment, it is noted that the flow rate required for the heat exchangers in a TEG producing a given amount of electrical power can be reduced by adaption of PCHEs. Such novel results on the TEG with PCHEs might be helpful for more compact design and expands the applicability of TEGs for waste heat recovery.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heat transfer for PCHE in TEG was investigated in detail by 3D CFD analysis. </LI> <LI> Experimental data for a 200-W TEG implemented with PCHEs are newly presented. </LI> <LI> Power density of the TEG was sufficiently high at low temperature. </LI> <LI> Reduction of TEG flow rate requirements from use of PCHEs is estimated. </LI> </UL> </P>