• The Journal of Bigdata
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• v.6 no.2
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• pp.85-98
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• 2021

The pandemic of COVID-19 further promoted the imbalance in the volume of imports and exports among countries using containers, which worsened the shortage of empty containers. Since it is important to secure as many empty containers as the appropriate demand for stable and efficient port operation, measures to predict demand for empty containers using various techniques have been studied so far. However, it was based on long-term forecasts on a monthly or annual basis rather than demand forecasts that could be used directly by ports and shipping companies. In this study, a daily and weekly prediction method using an actual artificial neural network is presented. In details, the demand forecasting model has been developed using multi-layer perceptron and multiple linear regression model. In order to overcome the limitation from the lack of data, it was manipulated considering the business process between the loaded container and empty container, which the fully-loaded container is converted to the empty container. From the result of numerical experiment, it has been developed the practically applicable forecasting model, even though it could not show the perfect accuracy.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.483-483
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• 2022

댐과 저수지의 운영 최적화를 위한 수문학적 예보는 현재 수동적인 댐 운영이 주를 이루면서 활용도가 높지 않다. 불확실한 기후변화나 기후재난 상황에서 우리 사회에 악영향을 최소화하기 위해 선제적으로 대응/대비할 수 있는 댐 운영 방안이 불가피하다. 강우량 예측 기술은 기후변화로 인해 제한적인 상황이다. 실례로, 2020년 8월에 섬진강의 댐이 극심한 집중 강우로 인해 무너지는 사태가 발생하였고 이로 인해 지역사회에 막대한 경제적 피해가 발생하였다. 선제적 댐 방류량 운영 기술은 또한 환경적인 변화로 인한 영향을 완화하기 위해 필요한 것이다. 제한적인 기상 예보 기술을 극복하고자 심화학습이나 강화학습 같은 인공지능 모델들의 활용성에 대한 연구가 시도되고 있다. 따라서 본 연구는 섬진강 댐의 시간당 수문 데이터를 이용하여 댐 운영을 위한 심화학습 모델을 개발하고 그 활용도를 평가하였다. 댐 운영을 위한 심화학습 모델로서 시계열 데이터 예측에 적합한 Long Sort Term Memory(LSTM)과 Gated Recurrent Unit(GRU) 알고리즘을 구축하고 댐 수위를 예측하였다. 분석 자료는 WAMIS에서 제공하는 2000년부터 2021년까지의 시간당 데이터를 사용하였다. 입력 데이터로서 시간당 유입량, 강우량과 방류량을, 출력 데이터로서 시간당 수위 자료를 각각 사용하였으며. 결정계수(R2 Score)를 통해 모델의 예측 성능을 평가하였다. 댐 수위 예측값 개선을 위해 하이퍼파라미터의 '최적값'이 존재하는 범위를 줄여나가는 하이퍼파라미터 최적화를 두 가지 방법으로 진행하였다. 첫 번째 방법은 수동적 탐색(Manual Search) 방법으로 Sequence Length를 24, 48, 72시간, Hidden Layer를 1, 3, 5개로 설정하여 하이퍼파라미터의 조합에 따른 LSTM와 GRU의 민감도를 평가하였다. 두 번째 방법은 Grid Search로 최적의 하이퍼파라미터를 찾았다. 이 두가지 방법에서는 같은 하이퍼파라미터 안에서 GRU가 LSTM에 비해 더 높은 예측 정확도를 보였고 Sequence Length가 높을수록 정확도가 높아지는 경향을 보였다. Manual Search 방법의 경우 R2가 최대 0.72의 정확도를 보였고 Grid Search 방법의 경우 R2가 0.79의 정확도를 보였다. 본 연구 결과는 가뭄과 홍수와 같은 물 재해에 사전 대응하고 기후변화에 적응할 수 있는 댐 운영 개선에 도움을 줄 수 있을 것으로 판단된다.

• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.481-486
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• 2022

The recent rapid growth of the IoT(Internet of Things) is leading to the spread of low-power wireless technology. A major challenge in designing IoT wireless networks is to achieve coexistence between different wireless technologies that share the 2.4 [GHz] ISM (Industrial Scientific Medical) frequency band. Therefore, there is a need for research on improving the reliability of wireless networks and coexisting operation between wireless networks. In particular, it is necessary to study an interference model and performance for mutual service coexistence in a BLE (Bluetooth Low Energy) wireless network environment, which is expected to be widely used as a connection medium between devices in various industrial fields. In this paper, the co-channel interference model with the IEEE 802.15.4 system is established focusing on the physical layer of the BLE system widely used in residential and industrial wireless applications, and the performance of the BLE wireless communication system is analyzed in the co-channel interference environment. As a result of the analysis, as the distance between the interference source and the BLE system increases in an environment where noise and co-channel interference exist, the amount of co-channel interference decreases and the error rate performance of the BLE system improves.

• Journal of Dental Anesthesia and Pain Medicine
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• v.24 no.1
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• pp.67-73
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• 2024

Background: Nitrous oxide has been an integral part of surgical anesthesia for many years in the developed world and is still used in developing countries such as India. The other main concerns in low-resource countries are the lack of an advanced anesthesia gas-scavenging system and modular surgical theatres. As a greenhouse gas that has been present in the atmosphere for more than 100 years and damages the ozone layer, nitrous oxide is three times worse than sevoflurane. Here, we conducted an observational study to quantify the annual nitrous oxide consumption and its environmental impact in terms of carbon dioxide equivalence in one of busiest tertiary health care and research centers in Northern India. Methods: Data related to nitrous oxide expenditure' from the operation theatre and manifold complex of our tertiary care hospital and research center from 2018 to 2021 were collected monthly and analyzed. The outcomes were extracted from our observational study, which was approved by our institutional ethics board (INT/IEC/2017/1372 Dated 25.11.2017) and registered prospectively under the Central Registry (CTRI/2018/07/014745 Dated 05.07.2018). Results: The annual nitrous oxide consumption in our tertiary care hospital was 22,081.00, 22,904.00, 17,456.00, and 18,392.00 m³ (cubic meters) in 2018, 2019, 2020, and 2021, respectively. This indicates that the environmental impact of nitrous oxide (in terms of CO₂ equivalents) from our hospital in 2018, 2019, 2020, and 2021 was 13,016.64, 13,287.82, 10,289.94, and 10,841.24 tons, respectively. Conclusion: This huge amount of nitrous oxide splurge is no longer a matter of laughter, and serious efforts should be made at every central and peripheral health center level to reduce it.

• Nanomaterials
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• v.12 no.7
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• pp.1061-1074
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• 2022

In this work, a self-powered, solar-blind photodetector, based on InZnSnO (IZTO) as a Schottky contact, was deposited on the top of Si-doped β-Ga₂O₃ by the sputtering of two-faced targets with InSnO (ITO) as an ohmic contact. A detailed numerical simulation was performed by using the measured J-V characteristics of IZTO/β-Ga₂O₃ Schottky barrier diodes (SBDs) in the dark. Good agreement between the simulation and the measurement was achieved by studying the effect of the IZTO workfunction, β-Ga₂O₃ interfacial layer (IL) electron affinity, and the concentrations of interfacial traps. The IZTO/β-Ga₂O₃ (SBDs) was tested at a wavelength of 255 nm with the photo power density of 1 mW/cm². A high photo-to-dark current ratio of 3.70×10⁵ and a photoresponsivity of 0.64 mA/W were obtained at 0 V as self-powered operation. Finally, with increasing power density the photocurrent increased, and a 17.80 mA/W responsivity under 10 mW/cm² was obtained.

• The Korean Journal of Air & Space Law and Policy
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• v.33 no.1
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• pp.205-226
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• 2018

For sustainable development of air transport, the establishment and application of international standards of environmental protection area is significant. The development and use of alternative fire extinguishing agent to Halon, which is used for the fire extinguishing systems of engine nacelles/APU and cargo compartments, has been requested in order to protect the ozone layer. The ICAO has been active in preparing international standards and recommended practices (SARPs); however, certification of alternative fire extinguishing agents has been postponed due to technical readiness problem.. Consequently, the implementation of SARPs has also been postponed by two years from the end of 2016. to the end of 2018. As such consequences have caused confusion among Member States regarding its implementation, it is necessary to discuss and pay more attention to this issue. ICAO Council and Air Navigation Commission should consider between setting the implementation time frame earlier or giving enough time for mature readiness and preparedness. Also in order to minimize the unnecessary discharge of Halon owned by Member States, it is necessary to consider efficient management methodologies; for example, requesting fire extinguisher manufacturers to recharge in professional ways. For the successful implementation of the SARPs, ICAO developed an implementation task list as including notification of differences, establishment of a national implementation plan, drafting of the modification to the national regulations and means of compliance, adoption of the national regulations and means of compliance. Member States can develop their own rule making process in reference with the ICAO implementation task list. This issue was presented and discussed during the 54th Conference of Directors General of civil aviation, Asia and Pacific Regions which was held in Ulaanbaatar, Mongolia in 2017 with significant attention among participated Contacting States. In this regards, ICAO Council and Air Navigation Commission should consult with Legal Bureau lawyers regarding SARPs preparing process to eliminate difficulties and confusions for proper implementation within effective date.

• Clean Technology
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• v.12 no.2
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• pp.67-77
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• 2006

A simple dual sludge process, called as $KNR^{(R)}$ (Kwon's Nutrient Removal) system, was developed for small sewage treatment. It is a hybrid system that consists of an UMBR (Upflow multi-layer bioreactor) as anaerobic and anoxic reactor with suspended denitrifier and a post aerobic biofilm reactor, filled with pellet-like media, with attached nitrifier. To evaluate the stability and performance of this system for small sewage treatment, the pilot-scale $KNR^{(R)}$ plant with a treatment capacity of $50m^3/d$ was practically applied to the actual sewage treatment plant, which was under retrofit construction during pilot plant operation, with a capacity of $50m^3/d$ in a small rural community. The HRTs of a UMBR and a post aerobic biofilm reactor were about 4.7 h and 7.2 h, respectively. The temperature in the reactor varied from $18.1^{\circ}C$ to $28.1^{\circ}C$. The pilot plant showed stable performance even though the pilot plant had been the severe fluctuation of influent flow rate and BOD/N ratio. During a whole period of this study, average concentrations of $COD_{cr}$, $COD_{Mn}$, $BOD_5$, TN, and TP in the final effluent obtained from this system were 11.0 mg/L, 8.8 mg/L, 4.2 mg/L, 3.5 mg/L, 9.8 mg/L, and 0.87/0.17 mg/L (with/without poly aluminium chloride(PAC)), which corresponded to a removal efficiency of 95.3%, 87.6%, 96.3%, 96.5%, 68.2%, and 55.4/90.3%, respectively. Excess sludge production rates were $0.026kg-DS/m^3$-sewage and 0.220 kg-DS/kg-BOD lower 1.9 to 3.8 times than those in activated sludge based system such as $A_2O$ and Bardenpho.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.2
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• pp.118-131
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• 1997

An opening efficiency experiment of anchovy boat seine has been carried out using a half size of the ordinary seine to reduce the size of the seine net and to improve the fishing efficiency from field operation. The intervals of towing boats were set at 100, 200 and 300m, and the towing speed, at 0.6, 0.9, and 1.2k't by possible combinations of them. The vertical openings of wing net, inside wing net, bagnet and flapper as well as the spreads of the seine net and the towing tension of the warp were measured, to find out efficient fishing gear and method of the anchovy boat seine. The results obtained are as follows : 1. The vertical opening of the inside wing net ranged from 8.7m to 12.0m at the normal current and from 7.0m to 10.0m at the counter current, and that of the wing net, from 8.4m to 19.8m at the normal current and from 4.9m to 16.3m at the counter current. The vertical opening of the wing net and inside wing net decreased as the towing speed and intervals of the boats increase, from 66% to 16% and from 32% to 18% of the normal opening, respectively. 2. The vertical opening of the fore of bag net ranged from 7.9m to 12.8m at the normal current and from 7.4m to 9.7m at the counter current, and that of the flapper, from 3.4m to 5.1m at the normal current and from 4.4m to 5.1m at the counter current, and that of the flapper, from 3.4m to 5.1m at the normal current and from 4.4m to 5.1m at the counter current. The vertical opening of the bag net was from 98% to 57% of the normal opening and the flapper showed a circular shape and it rose up to the upper layer with a slower towing speed. 3. The vertical opening of the end of the bag net ranged from 7.1m to 9.3m at the normal current and from 7.4m to 8.8m at the counter current. The end of the bag net rose up to the upper layer, This phenomenon was more apparent as the towing speed and the interval of the boats increase. 4. The towing tension of the experimental nets increased from 648kg to 2,716kg at the normal current and from 1,050kg to 6,010kg at the counter current with increasing towing speed. 5. The net depth of the anchovy seine was stable with the higher towing speed and the wider interval of the boats, but it was unstable by rising up to the upper layer with the lower towing speed and the narrower interval of towing boats.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.255-265
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• 1999

CTD castings and current observations are taken in June, July and October, 1997 and May and July, 1998 to investigate the effect of the Keum River dyke on the structure of physical properties and the type of the Keum River estuary. Tide and tidal current relation shows that the ebbing is longer than the flooding by 1.5 hours with the early current reversing before high tide. In the rainy season (May to July), frequent large fresh water discharge during the ebbing from the dyke changes vertical salinity difference and time variation of salinity greatly near the head of the estuary, where salinity becomes lower than 2‰ in summer fresh water flooding. Halocline developed by the fresh water discharge makes two-layer structure, of which strength and depth increase in the low tide. The relationship between tide phase and surface salinity variation shows the phase lag of 2.5 hours near the head of the estuary but the standing wave relation down the estuary. This phase lag implies that a low salinity water diluted by the fresh water discharge for 2-3 hours in the ebb period moves with tidal excursion. In the dry season, vertical salinity difference reduces significantly. We calculate stratification and circulation parameters using the observed salinity structure, surface current and fresh water discharge. The Keum River estuary shows a partially mixed type, changing the stratification parameter from the rainy to the dry season. Mean flows of observed tidal current at lower and upper layer are landward and seaward, which are consistent with the circulation of a partially mixed estuary. Based upon the estuary type and circulation we suggest that the suspended materials will move toward the upstream due to low-layer mean flow and then the Keum River estuary will be a deposit environment.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.538-543
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• 2008

Recently a nano-scale diamond is possible to manufacture forms of powder(below 100 nm) by new processing of explosion or deposition method. Using a sintering of nano-scale diamond is possible to manufacture of grinding tools. We have need of a processing development of coated uniformly inorganic to prevent an abnormal grain growth of nano-crystal and bonding obstacle caused by sintering process. This paper, in order to improve the sintering property of nano-scale diamond, we coated ZnO thin films(thickness: $20{\sim}30\;nm$) in a vacuum by ALD(atomic layer deposition) Economically, in order to deposit ZnO all over the surface of nano-scale diamond powder, we used a new modified fluidized bed processing replaced mechanical vibration effect or fluidized bed reactor which utilized diamond floating owing to pressure of pulse(or purge) processing after inserted diamond powders in quartz tube(L: 20 mm) then closed quartz tube by porosity glass filter. We deposited ZnO thin films by ALD in closed both sides of quartz tube by porosity glass filter by ALD(precursor: DEZn($C_4H_{10}Zn$), reaction gas: $H_2O$) at $10^{\circ}C$(in canister). Processing procedure and injection time of reaction materials set up DEZn pulse-0.1 sec, DEZn purge-20 sec, $H_2O$ pulse-0.1 sec, $H_2O$ purge-40 sec and we put in operation repetitive 100 cycles(1 cycle is 4 steps) We confirmed microstructure of diamond powder and diamond powder doped ZnO thin film by TEM(transmission electron microscope) Through TEM analysis, we confirmed that diamond powder diameter was some $70{\sim}120\;nm$ and shape was tetragonal, hexagonal, etc before ALD. We confirmed that diameter of diamond powders doped ZnO thin film was some $70{\sim}120\;nm$ and uniform ZnO(thickness: $20{\sim}30\;nm$) thin film was successfully deposited on diamond powder surface according to brightness difference between diamond powder and ZnO.