• Korean Chemical Engineering Research
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• 제61권4호
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• pp.635-644
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• 2023

Due to the rapid development of the livestock industry, particularly due to residual pharmaceutical antibiotics, environmental populations have been negatively affected. Herein, we report a ZnO/melamine-functionalized carboxylic-rich graphene oxide (ZFG) photocatalyst for visible light-driven photocatalytic degradation of tetracycline hydrochloride in aqueous solutions. The properties of the photocatalysts were evaluated by XRD, FTIR, XPS, Fe-SEM, HR-TEM, TGA, Raman spectroscopy, UV-Vis spectroscopy, zeta potential, and electrochemical measurements. The photocatalytic activity was measured using high-performance liquid chromatography. The photocatalytic properties of the ZFG photocatalyst evaluated against the tetracycline hydrochloride (TCH) antibiotic under visible light irradiation showed superior photodegradation of 96.27% within 60 min at an initial pH of 11. The enhancement of photocatalytic degradation was due to the introduction of functionalized graphene, which increases the light-harvesting capability and molecular adsorption capability in addition to minimizing the recombination rate of photogenerated charge carriers due to its role as an electron acceptor and mediator.

• Journal of Microbiology and Biotechnology
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• 제28권3호
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• pp.432-438
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• 2018

Microalgae hold promise as a renewable energy source for the production of biofuel, as they can convert light energy into chemical energy through photosynthesis. However, cost-efficient harvest of microalgae remains a major challenge to commercial-scale algal biofuel production. We first investigated the potential of electrolytic water as a flocculant for harvesting Tetraselmis sp. Alkaline electrolyzed water (AEW) is produced at the cathode through water electrolysis. It contains mineral ions such as $Na^+$, $K^+$, $Ca^{2+}$, and $Mg^{2+}$ that can act as flocculants. The flocculation activity with AEW was evaluated via culture density, AEW concentration, medium pH, settling time, and ionic strength analyses. The flocculation efficiency was 88.7% at 20% AEW (pH 8, 10 min) with a biomass concentration of 2 g/l. The initial biomass concentration and medium pH had significant influences on the flocculation activity of AEW. A viability test of flocculated microalgal cells was conducted using Evans blue stain, and the cells appeared intact. Furthermore, the growth rate of Tetraselmis sp. in recycled flocculation medium was similar to the growth rate in fresh F/2 medium. Our results suggested that AEW flocculation could be a very useful and affordable methodology for fresh biomass harvesting with environmentally friendly easy operation in part of the algal biofuel production process.

• 전기전자학회논문지
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• 제21권1호
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• pp.66-69
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• 2017

In recent year, energy harvesting technologies from the ambient environments such as light, motion, wireless waves, and temperature again a lot of attraction form research community [1-5] due to its efficient solution in order to substitute for conventional power delivery methods, especially in wearable together with on-body applications. The drawbacks of battery-powered characteristic used in commodity applications lead to self-powered, long-lifetime circuit design. Thermoelectric generator, a solid-state sensor, is useful compared to the harvesting devices in order to enable self-sustained low-power applications. TEG based on the Seebeck effect is utilized to transfer thermal energy which is available with a temperature gradient into useful electrical energy. Depending on the temperature difference between two sides, amount of output power will be proportionally delivered. In this work, we illustrated a low-input voltage energy harvesting circuit applied discontinuous conduction mode (DCM) method for getting an adequate amount of energy from thermoelectric generator (TEG) for a specific wearable application. With a small temperature gradient harvested from human skin, the input voltage from the transducer is as low as 60mV, the proposed circuit, fabricated in a $0.6{\mu}m$ CMOS process, is capable of generating a regulated output voltage of 4.2V with an output power reaching to $40{\mu}W$. The proposed circuit is useful for powering energy to battery-less systems, such as wearable application devices.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.112-117
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• 2024

The Internet of Things (IoT) device is a key component for Industry 4.0, which is the network in homes, factories, buildings, and infrastructures to monitor and control the systems. To demonstrate the IoT network, batteries are widely utilized as power sources, and the batteries inevitably require repeated replacement due to their limited capacity. Magneto-mechano-electric (MME) generators are one of the candidate to develop self-powered IoT systems since MME generators can harvest electricity from stray alternating current (AC) magnetic fields arising from electric power cables. Herein, we report a magneto-mechano-triboelectric generator enabled by a ferromagnetic-ferroelectric composite. In the triboelectric nylon matrix, a ferromagnetic carbonyl iron powder (CIP) was introduced to induce magnetic force near the AC magnetic field for MME harvesting. Additionally, a ferroelectric ceramic powder was also added to the MME composite material to enhance the charge-trapping capability during triboelectric harvesting. The final ferromagnetic-ferroelectric composite-based MME triboelectric harvester can generate an open-circuit voltage and a short-circuit current of 110 V and 8 μA, respectively, which were enough to turn on a light emitting diode (LED) and charge a capacitor. These results verify the feasibility of the MME triboelectric generator for not only harvesting electricity from an AC magnetic field but also for various self-powered IoT applications.

• 전기전자학회논문지
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• 제26권3호
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• pp.483-487
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• 2022

본 논문에서는 태양에너지 하베스팅을 위한 자가발전 아두이노 시스템을 설계하고 이의 동작을 설명한다. 이를 위해서 아두이노 시스템이 시시각각 변하는 태양에너지의 양을 센싱하고 이에 따라서 active mode와 sleep mode의 동작 시간의 비율을 스스로 조정해서 주어진 태양 빛의 세기에 대해서 최적으로 동작할 수 있는 동작 조건을 스스로 찾아가는 방법을 설명하고 이의 동작을 검증한다. 본 논문에서 개발한 active mode와 sleep mode의 동작 시간의 비율의 자가 조절을 통해서 태양 빛의 세기가 충분히 강할 경우에는 아두이노 시스템이 active mode로 지속적으로 구동되고, 태양광으로부터 전력을 충분히 공급받을 수 없는 경우 sleep mode를 사용하여 전력 소모를 최소화한다. 그 결과 active mode를 지속적으로 구동하는 것에 비해 sleep mode를 사용하는 경우 전력 소모를 최대 81.7% 줄여 에너지 소비를 최소화할 수 있다는 것을 알 수 있다. 또한 빛의 세기가 중간 수준일 때에는 active mode와 sleep mode의 비율을 빛의 세기에 맞게 적정하게 배분하여 동작하게 한다. 본 논문에서 제안한, 스스로 active mode와 sleep mode의 동작 시간 비율을 조절하는 방법은 특히 높은 전력 소비 효율 특성이 필요한 웨어러블 및 바이오-헬스용 자가발전 시스템을 에너지 효율적으로 동작시킬 때에 도움이 될 것으로 생각된다.

• 한국전기전자재료학회논문지
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• 제34권6호
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• pp.495-504
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• 2021

Energy Harvesting is a technology that can convert wasted energy such as vibration, heat, light, electromagnetic energy, etc. into usable electrical energy. Among them, vibration-based piezoelectric energy harvesting (PEH) has high energy conversion efficiency with a small volume; thus, it is expected to be used in various autonomous powering devices, such as implantable medical devices, wearable devices, and energy harvesting from road or automobiles. In this study, wasted vibration energy in an automobile is converted into electrical energy by high-power piezoelectric materials, and the generated electrical energy is found to be an auxiliary power source for the operation of wireless sensor nodes, LEDs, etc. inside an automobile. In order to properly install the PEH in an automobile, vibration characteristics includes frequency and amplitude at several positions in the automobile is monitored initially and the cantilever structured PEH was designed accordingly. The harvesting properties of fabricated PEH is characterized and installed into the engine part of the automobile, where the vibration amplitude is stable and strong. The feasibility of PEH is confirmed by operating electric components (LEDs) that can be used in practice.

• 한국자원식물학회지
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• 제31권5호
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• pp.522-530
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• 2018

Brachypodium distachyon has been developed as a monocot model plant for temperate grasses and bioenergy crops. Although B. distachyon research is moving forward rapidly, the study of photoresponses has not been explored. To extend our knowledge of responses to light in monocots, we performed photoresponse analysis of B. distachyon using two inbred lines, Bd21 and Bd21-3. In this study, we first compared growing phenotypes between the two lines and investigated coleoptile and primary leaf growths under dark, far-red, red, and white light conditions. The results showed that the growth of the two lines were similar until tillering stage, but other developmental stages from heading to senescence were much delayed in Bd21-3, which resulted in increased height and tiller numbers. Under different light conditions, primary leaf lengths were kept increasing during the growth period, whereas the coleoptile extension was inhibited 4 to 7 days after growth depending on the light conditions applied. These results suggest that the responses to light in B. distachyon can be examined by measuring coleoptile lengths approximately 7 days after seedling growth. Moreover, we selected light-responsive genes known in Arabidopsis thaliana, such as chlorophyll A/B binding protein (CAB), light-harvesting chlorophyll binding protein (Lhcb) and chalcone synthase (CHS), and confirmed their light-induced gene expression in B. distachyon. Therefore, the present study suggests that the inhibition of coleoptile growth can be used as the parameter to analyze photoresponses in the monocot model plant, and also provide the reference genes whose expression is induced by far-red and red light treatment.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.703-704
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• 2014

• Korean Chemical Engineering Research
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• 제61권4호
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• pp.627-634
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• 2023

Graphitic carbon nitride (g-C₃N₄) has attracted considerable attention since its discovery for its catalysis of water splitting to hydrogen and oxygen under visible light irradiation. However, pristine g-C₃N₄ confers only low photocatalytic efficiency and requires surface cocatalysts to reach moderate activity due to a lack of accessible surface active sites. Inspired by the high specific surface area and superior electron transfer of graphene, we developed a strongly coupled binary structure of graphene and g-C₃N₄ aerogel with 3D porous skeleton. The as-prepared 3D structure photocatalysts achieve a high surface area that favors efficient photogenerated charge separation and transfer, enhances the light-harvesting efficiency, and significantly improves the photocatalytic hydrogen evolution rate as well. The photocatalyst performance is observed to be optimized at the ratio 3:7 (g-C₃N₄:GO), leading to photocatalytic H₂ evolution of 16125.1 mmol. g^-1. h^-1 under visible light irradiation, more than 161 times higher than the rate achieved by bulk g-C₃N₄.

• 한국전기전자재료학회논문지
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• 제37권3호
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• pp.337-344
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• 2024

This work focuses on improving the light-harvesting efficiency of thin-film silicon solar cells through innovative multi-architecture surface modifications. To create a regular optical structure, a lithographic process was performed to form it on a glass substrate through various etching processes, from Etch-1 to Etch-3. AZO was deposited on top of the structures and re-etched to create a multi-architectural surface. These surface-modified structures improved the light absorption and overall performance of the solar cell through changes in optical and physical properties, which we will analyze. In addition, we investigated the effect of post-cleaning on the etched glass structures through EDX analysis to understand the mechanism of the etching action. The results of this study are expected to provide important guidelines for the design and fabrication of solar cells and other photovoltaic devices.