• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.412-415
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• 2015

This paper presents a MPPT(Maximum Power Point Tracking) control CMOS interface circuit for vibration energy harvesting. The proposed circuit consists of an AC-DC converter, MPPT Controller, DC-DC boost converter and PMU(Power Management Unit). The AC-DC converter rectifies the AC signals from vibration devices(PZT). MPPT controller is employed to harvest the maximum power from the PZT and increase efficiency of overall system. The DC-DC boost converter generates a boosted and regulated output at a predefined level and provides energy to load using PMU. A full-wave rectifier using active diodes is used as the AC-DC converter for high efficiency, and a schottky diode type DC-DC boost converter is used for a simple control circuitry. The proposed circuit has been designed in a 0.35um CMOS process. The chip area is $950um{\times}920um$.

• Journal of Navigation and Port Research
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• v.26 no.2
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• pp.235-243
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• 2002

Theoretical analysis have been performed to design the high power semiconductor laser for an optical sensor at 1.55${\mu}{\textrm}{m}$ wavelength range which is the lowest loss wavelength in optical fiber. The materials of active region and SCH were $Ln_{1-x}Ga_xAs_yP_{1-y}$. In order to use the light source of optical sensors, it has to satisfy wide spectral width and short coherence length. Therefore, in order to suppress lasing oscillation, we proposed laterally tilted PBH type with a window region. Also, tapered stripe structure was applied for high coupling efficiency into a single mode fiber. From these analyses, the devices of laterally tilted angled and bending structure were fabricated and their characteristics were measured. In the results of the measurement, the fabricated devices have sufficient output power and wide FWHM to apply to the light source of optical fiber sensors.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.467-470
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• 2009

A novel 8 V DC power source with an external series-parallel connection of 50 Dye-Sensitized Solar Cells(DSSCs) has been proposed. One DSC has the optimized length to width ratio of $5.2{\times}2.6$ cm and an active area 8 $cm^2$($4.62{\times}1.73$ cm) which attained a conversion efficiency of 4.2%. From the electrochemical impedance spectroscopic analysis, it was found that the resistance elements related to the Pt electrode and electrolyte interface behave like that of diode and the series resistance corresponds to the sum of the other resistance elements. In addition, the TEMoo mode pulsed Nd:YAG laser beam is used to improve the incident photon to current efficiency(IPCE) of DSSC. From this result, this novel 8V-0.38A DC power source shows stable performance with an energy conversion efficiency of about 4.5% under 1 sun illumination(AM 1.5, Pin of 100 $mW/cm^2$).

• Polymer(Korea)
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• v.29 no.5
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• pp.486-492
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• 2005

Into a no-conjugated polymer chain we have introduced side chains with a styrene-linked triphenylamine segment as a $\pi-electron$ donor, styrene-]inked aminobenzaldehyde segment as a tunable reactive -CHO group, and PM (4-(dicyanomethylene)-2-(tert-butyl)-4H-pyran) moiety as a $\pi-electron$ acceptor for red emitting materials. The thermal stability and the optical properties of the statistical copolymers have been studied. All the polymers were electrochemically active and showed electroluminescent emission at around 700nm. The EL device of P5-PM based on the sturcture of $ITO/PPV/polymer/BCP/Alq_3/Al$ showed a maximum brightness of $120cd/m^2\;at\;50mA/cm^2$ with an external quantum efficiency of $0.67\%$. It was possible to enhance the external quantum efficiency by balancing the charge recombination. A red-emitting polymer with high external quantum efficiency was developed by incorporating bifunctionality.

• Journal of The Korean Society of Integrative Medicine
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• v.9 no.3
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• pp.185-192
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• 2021

Purpose : Our study aimed to compare the effectiveness of low-level laser therapy (LLLT) and light-emitting diode therapy (LEDT) for chronic pain intensity reduction and body temperature increase in older adults with chronic pain. Methods : Overall, 144 of 332 participants' records were used in this retrospective chart review. The study was conducted at a private health center in Busan city and the integrative medical center of a tertiary care hospital in Daegu city, South Korea. Patients experiencing chronic pain for over 6 months were assigned to either the LLLT or LEDT group. Both groups underwent 16 sessions of phototherapy held twice a week for 8 weeks, with each session lasting 60 minutes. The primary outcomes for both groups were the mean visual analogue scale (VAS) scores and body temperatures in both groups. The secondary outcome was the correlation between changes in body temperature and pain intensity. Measurements were recorded at the baseline and at each follow-up session. Results : A decrease in pain intensity and an increase in body temperature (p<.001) were observed in both groups. There was a significant difference in the VAS scores and temperature changes between the groups (p<.001). Odditionally, there were significant differences in the patterns of change in the VAS score and body temperature between the groups as the sessions progressed (p<.01), and a strong inverse correlation between body temperature and pain intensity changes were observed (p<.01). Conclusion : The use of photobiomodulation therapy at a specific wavelength may improve pain severity and simultaneously increase the body temperature among elderly people with chronic pain.

• Korean Journal of Plant Resources
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• v.32 no.3
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• pp.228-236
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• 2019

This study is conducted to investigate the effects of growth characteristics (GC) and DPPH radical scavenging activity (DRSA) of the heading lettuce 'Fidel' depending on four concentrations of activated mineral groups (AMG: 1.6% active minerals and 0.03% CaO) added to basic nutrient solutions (diluted by 0, 0.05, 0.1, and 0.2%) and on four different light-emitting diodes (LED; B:R:W ratio = 0:1:12, 0:1:9, 0:5:5, and 2:3:5). Both 0.1 and 0.2% AMG showed better GC of lettuce in plant width, plant length, leaf width, leaf length, and the number of leaves than those of other AMG, while leaf thickness and chlorophyll value did not show significant difference among all AMG. Moreover, 0.1 and 0.2% AMG showed heavier shoot fresh weights than those of other AMG. As for the combinations of AMG and LED, B0:R5:W5 showed the best lettuce GC regardless of AMG compared to other AMG and LED combinations. As shown in the above results of LED, although there was a difference in lettuce growth by LED, the differences of lettuce growth by AMG were statistically significant. The DRSA was the highest at 82.8% in B2:R3:W5, followed by B0:R5:W5 at 77.8%. LED showed differences but AMG did not affect DRSA. Therefore, the optimal conditions in plant factory for GC and DRSA of the lettuce were 0.1% AMG and B0:R5:W5.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.267-270
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• 2014

This paper presents a CMOS interface circuit for vibration energy harvesting. The proposed circuit consists of an AC-DC converter and a DC-DC boost converter. The AC-DC converter rectifies the AC signals from vibration devices(PZT), and the DC-DC boost converter generates a boosted and regulated output at a predefined level. A full-wave rectifier using active diodes is used as the AC-DC converter for high efficiency, and a schottky diode type DC-DC boost converter is used for a simple control circuitry. A MPPT(Maximum Power Point Tracking) control is also employed to harvest the maximum power from the PZT. The proposed circuit has been designed in a 0.35um CMOS process. The chip area is $530um{\times}325um$. Simulation results shows that the maximum efficiencies of the AC-DC converter and DC-DC boost converter are 97.7% and 89.2%, respectively. The maximum efficiency of the entire system is 87.2%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.266-274
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• 2023

Recently, sterilization technology has received increasing interest due to the COVID-19 pandemic and required safety precautions. Particularly, sterilization devices using near ultraviolet (UV) with a 405 nm wavelength are also drawing attention. It has a UV-C wavelength and other sterilization effects. Its blue-colored light on the boundary between UV and visible light is used as a light-emitting diode (LED) lamp for 405 nm sterilization, owing to its longer wavelengths than UV rays. However, the 405 nm wavelength contains blue light that can damage the eyes and skin during prolonged exposures and affect the emotional and biological parts of the body. Currently, 405 nm sterilization LED light registers are circulating in the market. However, they have not undergone safety tests for blue-light hazards. Thus, with the active distribution of sterilization LED lights, solid safety standards and management systems are essential to protect users from blue-light hazards. Accordingly, in this study, we conducted spectral radiance and spectral radiative luminance tests on 405 nm sterilization LED registers available in the market by the measurement criteria of IEC 62471. Safety standards must be established to secure users' safety against blue light hazards at a time when 405nm sterilization LED lights are actively distributed due to COVID-19.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.953-965
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• 2023

The stratospheric drones are developed to perform missions such as weather observation, communication relay, surveillance, and reconnaissance at 18km to 20km, where climate change is minimal and there is no worry about a collision with aircraft. It uses solar panels for daytime flights and energy stored in batteries for night flights, providing many advantages over existing satellites. The electrical and power systems essential for stratospheric drone flight must ensure reliability, efficiency, and lightness by selecting the optimal circuit topology. Therefore, it is necessary to analyze the circuit topology of various types of multi-level inverters with high redundancy that can ensure the reliability and efficiency of the motor driving power required for stable long-term flight of stratospheric drones. By quantifying the switch element voltage drop and the number and weight of inverter components for each topology, we evaluate efficiency and lightness and propose the most suitable circuit topology for stratospheric drones.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.537-539
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• 2006

We developed an 4.5" $192{\times}64$ active matrix organic light-emitting diode display on a glass using organic thin-film transistor (OTFT) switching-arrays with two transistors and a capacitor in each sub-pixel. The OTFTs has bottom contact structure with a unique gate insulator and pentacene for the active layer. The width and length of the switching OTFT is $800{\mu}m$ and $10{\mu}m$ respectively and the driving OTFT has $1200{\mu}m$ channel width with the same channel length. On/off ratio, mobility, on-current of switching OTFT and on-current of driving OTFT were $10^6,0.3{\sim}0.5\;cm^2/V{\cdot}sec$, order of 10 ${\mu}A$ and over 100 ${\mu}A$, respectively. AMOLEDs composed of the OTFT switching arrays and OLEDs made using vacuum deposition method were fabricated and driven to make moving images, successfully.