• Journal of the Korean Electrochemical Society
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• v.22 no.2
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• pp.60-68
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• 2019

High-voltage operation of the lithium ion battery is one of the advantageous approaches to obtain high energy capacity without changing the conventional cell components and structure. However, operating at harsh condition inevitably results in severe side reactions at the electrode surface and structural disintegration of active material particles. Herein we coated layers composed of $Al_2O_3$ and ZnO on the electrode based on NCM using atomic layer deposition (ALD). Thicker layers of novel Al-doped ZnO (AZO) coating compared to conventional ALD coated layers are prepared. Cathode based on NCM with the varying AZO coating thickness are fabricated and used for coin cell assembly. Effect of ALD coating thickness on the charge-discharge cycle behavior obtained at high-voltage operation was investigated.

• The Journal of the Convergence on Culture Technology
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• v.7 no.1
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• pp.646-653
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• 2021

The medical bed developed in this study consists of N keys and each is driven vertically by an actuator. Since M sensors are mounted on each keyboard to measure body pressure, the resolution of the body pressure map is determined by the MN. A sensor controller is mounted on each keyboard, and the body pressure values measured from M sensors are transmitted to the main controller through a serial communication network such as CAN (Car Area Network). Each keyboard is equipped with a servo driver that drives a motor, and it is connected to the main controller via CAN to control the height of the keyboard according to the displacement value indicated by the main controller. In addition, the maximum body pressure value and body pressure ratio applied to each part of the keyboard are calculated and used as the basic data for controlling bed comfort by artificial intelligence. As a result, the proposed system can be a foundation that can be used for the control of body comfort and pressure sore prevention by artificial intelligence to be developed in the future.

• Journal of the Korean Institute of Gas
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• v.28 no.1
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• pp.59-64
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• 2024

In this study, we conducted research on a miniaturized transmission system suitable for ultra-compact electric vehicles, such as electric arts or small electric cars. While conventional electric vehicles eliminate multi-gear transmissions and control motor output or secure initial driving force through reducers, in vehicles like electric karts or compact electric cars, which have relatively small battery capacities, the driving range can be reduced or the motor can be stressed epending on the loading state. Therefore, in this study, we developed a low stage ratio 0.625 and high stage ratio 1.6 a two-stage transmission system that can change gears as needed, considering factors such as slope conditions and loading status, by applying the continuously variable transmission (CVT) mechanism. Based on the selected gear ratios, we designed the transmission and created a test rig to verify the power transmission efficiency of the developed transmission. Using the test rig, we varied the rotational speed and load of the transmission to confirm its power transmission characteristics and also examined the heat generation characteristics during shifting and operation. As a result, developed a two-stage transmission with a CVT structure.

• Journal of IKEEE
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• v.28 no.1
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• pp.78-89
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• 2024

PMIC chips based on a BCD process used in automotive semiconductors require multi-time programmable (MTP) intellectual property (IP) that does not require additional masks to trim analog circuits. In this paper, MTP cell size was reduced by about 18.4% by using MTP cells using PMOS capacitors (PCAPs) instead of NMOS capacitors (NCAPs) in MTP cells, which are single poly EEPROM cells with two transistors and one MOS capacitor for small-area MTP IP design. In addition, from the perspective of MTP IP circuit design, the two-stage voltage shifter circuit is applied to the CG drive circuit and TG drive circuit of MTP IP design, and in order to reduce the area of the DC-DC converter circuit, the VPP (=7.75V), VNN (=-7.75V) and VNNL (=-2.5V) charge pump circuits using the charge pumping method are placed separately for each charge pump.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.77-88
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• 2000

In this paper, the 3-mode variable gain high power amplifier for a transmitter of INMARSAT-B operating at L-band(1626.5-1646.5 MHz) was developed. This SSPA can amplify 42 dBm in high power mode, 38 dBm in medium power mode and 36 dBm in low power mode for INMARSAT-B. The allowable errol sets +1 dBm as the upper limit and -2 dBm as the lower limit, respectively. To simplify the fabrication process, the whole system is designed by two parts composed of a driving amplifier and a high power amplifier. The HP's MGA-64135 and Motorola's MRF-6401 were used for driving amplifier, and the ERICSSON's PTE-10114 and PTF-10021 for the high power amplifier. The SSPA was fabricated by the RP circuits, the temperature compensation circuits and 3-mode variable gain control circuits and 20 dB parallel coupled-line directional coupler in aluminum housing. In addition, the gain control method was proposed by digital attenuator for 3-mode amplifier. Then il has been experimentally verified that the gain is controlled for single tone signal as well as two tone signals. In this case, the SSPA detects the output power by 20 dB parallel coupled-line directional coupler and phase non-splitter amplifier. The realized SSPA has 41.6 dB, 37.6 dB and 33.2 dB for small signal gain within 20 MHz bandwidth, and the VSWR of input and output port is less than 1.3:1. The minimum value of the 1 dB compression point gets more than 12 dBm for 3-mode variable gain high power amplifier. A typical two tone intermodulation point has 36.5 dBc maximum which is single carrier backed off 3 dB from 1 dB compression point. The maximum output power of 43 dBm was achieved at the 1636.5 MHz. These results reveal a high power of 20 Watt, which was the design target.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.1
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• pp.48-59
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• 2023

Ground-level ozone affects human health and plant growth. Ozone is produced by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOCs) from anthropogenic and biogenic sources. In this study, two different land cover and emission factor datasets were input to the MEGAN v2.1 emission model to examine how these parameters contribute to the biogenic emissions and ozone production. Four input sensitivity scenarios (A, B, C and D) were generated from land cover and vegetation emission factors combination. The effects of BVOCs emissions by scenario were also investigated. From air quality modeling result using CAMx, maximum 1 hour ozone concentrations were estimated 62 ppb, 60 ppb, 68 ppb, 65 ppb, 55 ppb for scenarios A, B, C, D and E, respectively. For maximum 8 hour ozone concentration, 57 ppb, 56 ppb, 63 ppb, 60 ppb, and 53 ppb were estimated by scenario. The minimum difference by land cover was up to 25 ppb and by emission factor that was up to 35 ppb. From the modeling performance evaluation using ground ozone measurement over the six regions (East Seoul, West Seoul, Incheon, Namyangju, Wonju, and Daegu), the model performed well in terms of the correlation coefficient (0.6 to 0.82). For the 4 urban regions (East Seoul, West Seoul, Incheon, and Namyangju), ozone simulations were not quite sensitive to the change of BVOC emissions. For rural regions (Wonju and Daegu) , however, BVOC emission affected ozone concentration much more than previously mentioned regions, especially in case of scenario C. This implies the importance of biogenic emissions on ozone production over the sub-urban to rural regions.

• KSBB Journal
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• v.23 no.4
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• pp.317-322
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• 2008

The Biochemical Oxygen Demand(BOD) is one of important parameters for the most widely used method of organic pollution in wastewater and wastewater treatment effluent. As the conventional BOD test needs 5-day long incubation period, it is thus incompatible with real time control of wastewater treatment plant. To resolve this problem, in the present study an on-line Dissolved Oxygen(DO) monitoring system was used to observe the transient change of dissolved oxygen concentration in livestock wastewater. The system was composed of BOD sensor, amplifier and computer. It was observed that the concentration of the microorganism in the livestock wastewater was relatively constant during the growth period of initial one hour, which allowed the assumption of the constant Oxygen Uptake Rate(OUR) within one hour of measurement. It was thus concluded that the present scheme provided a protocol for automatic measurement of BOD in livestock wastewater, which can be applicable to optimal control of livestock wastewater treatment plant.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.214.1-214.1
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• 2015

Thin-film transistors (TFTs)의 채널층으로 널리 쓰이는 indium-gallium-zinc oxide (IGZO)는 높은 전자 이동도(약 10 cm2/Vs)를 나타내며 유기 발광 다이오드디스플레이(OLED)와 대면적 액정 디스플레이(LCD)에 필수적으로 사용되고 있다. 하지만, 이러한 재료는 우수한 TFT의 채널층의 특성을 가지는 반면, ZnO 기반 재료이기 때문에 소자 구동에서의 안정성은 가장 큰 문제로 남아있다. 따라서 최근, IGZO layer의 특성을 향상시키기 위한 연구가 다양한 방법으로 시도되고 있다. IGZO의 조성비를 조절하여 전기적 특성을 최적화거나 IGZO layer의 조성 중 Ga을 다른 금속 메탈로 대체하는 연구도 이루어지고 있다. 그러나 IGZO에 미량의 도펀트를 첨가하여 박막 특성 변화를 관찰한 연구는 거의 진행되지 않고 있다. 산화물 TFTs의 전기적 특성과 안정성은 산소 함량에 영향을 많이 받는 것으로 알려져 있으며, 더욱이 TFT 채널층으로 쓰이는 IGZO 박막의 고유한 산소 공공은 디바이스 작동 중 열적으로 활성화 되어 이온화 상태가 될 때 소자의 안정성을 저하시키는 것이 문제점으로 지적되고 있다. 그러므로 본 연구에서는 낮은 전기 음성도(1.22)와 표준전극전위(-2.372 V)를 가지며 산소와의 높은 본드 엔탈피 값(719.6 kJ/mol)을 가짐으로써 산소 공공생성을 억제할 것으로 기대되는 yttrium을 IGZO의 도펀트로 도입하였다. 따라서 본 연구에서는 Y-IGZO의 박막 특성 변화를 관찰하고자 한다. 본 연구에서는 magnetron co-sputtering법으로 IGZO 타깃(DC)과 Y2O3 타깃(RF)를 이용하여 기판 가열 없이 동시 방전을 이용해 non-alkali glass 기판 위에 증착 하였다. IGZO 타깃은 DC power 110 W으로 고정하였으며 Y2O3 타깃에는 RF Power를 50 W에서 110 W까지 증가시키면서 Y 도핑량을 조절하였다. Working pressure는 고 순도 Ar을 20 sccm 주입하여 0.7 Pa로 고정하였다. 모든 실험은 $50{\times}50mm$ 기판 위에 총 두께 $50nm{\pm}2$ 박막을 증착 하였으며, 그 함량에 따른 전기적 특성 및 광학적 특성을 살펴보았다. 또한, IGZO 박막 제조 시 박막의 안정화를 위해 열처리과정은 필수적이다. 하지만 본 연구에서는 열처리를 진행하지 않고 Y-IGZO의 안정성 개선 여부를 보기 위하여 20일 동안 상온에서 방치하여 그 전기적 특성변화를 관찰하였다. 나아가 Y-IGZO 채널 층을 갖는 TFT 소자를 제조하여 소자 구동 특성을 관찰 하였다. Y2O3 타깃에 가해지는 RF Power가 70 W 일 때 Y-IGZO박막은 IGZO박막과 비교하여 상대적으로 캐리어 밀도는 낮은 반면 이동도는 높은 최적 특성을 얻을 수 있었다. 상온방치 결과 Y-IGZO박막은 IGZO박막에 비해 전기적 특성 변화 폭이 적었으며 이것은 Y 도펀트에 의한 안정성 개선의 결과로 예상된다. 투과도는 Y 도핑에 의하여 약 1.6 % 정도 상승하였으며 밴드 갭 내에서 결함 준위로 작용하는 산소공공의 억제로 인한 결과로 판단된다.

• Korean Journal of Materials Research
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• v.4 no.3
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• pp.301-311
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• 1994

The growth of amorphous and first crystalline phase, and phase sequence by solid state reaction were examined in Co/Si multilayer thin films by DSC and XRD. The experimental results were compared with the results expected by effective driving force models, PDF and effective heat of formation models.Amorphous phase growth was not observed in Co/Si system and it was consistent with the predicted result by effective driving force. It was observed that the first crystalline phase is CoSi. According to the PDF and effective heat of formation models, the first crystalline phases were CoSi and $CO_2Si$, respectively. The experiemental results were coincident with the PDF model considering structure factors. In case of the atomic concentration ratios of 2Co : 1Si and 1Co : 2Si, the phases sequences were $CoSi\to Co_2Si$ and $CoSi \to Co_2Si \to CoSi \to CoSi_2$, respectively and it was analysized through the effective heat of formation model. The formations of CoSi, $CO_2Si$ and $COSi_2$ in initial stage were controlled by nucleation and the activation energies for the nucleation of three phases were 1.71, 2.34 and 2.79eV.

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.36-41
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• 2017

As the space debris in the satellite orbit increases, the risk of collision between the currently operating satellites and the space debris is continuously increasing. Therefore, in this study, we designed one-degree-of-freedom capture device using simple deployment mechanism. The capture device consists of four link groups connected with net. To increase the reliability, each link group is connected to one driving part so that the total degree of freedom is 1. In addition, the links were stowed on each side of the satellites so that they would not affect the janitor satellite mission. Finally, to confirm the possibility of deployment in the space environment, we carried out deployment experiments in water similar to the microgravity environment, and confirmed the deployment of capture device and the possibility of capturing target satellite.