• Journal of Korean Society of Transportation
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• v.22 no.7 s.78
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• pp.25-32
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• 2004

It is implicated in the current road design manual that design speed is well representing the operating speed of drivers. On the contrary, the disparity between the design speed and operating speed means that current road design cannot guarantee the safety and comfort of driving. In this context, operating speed was observed at the two lane rural roadways to find out the relation of operating speed and design speed. In addition to this, the friction factor from supply and demand which was derived from the operating speed was compared in terms of the dynamics in driving safety factor. It was concluded that the actual speed was consistently exceeding the design speed at the horizontal curves having the radius less than or equal to 200 m. Similarly, the demanded side friction was also consistently exceeding the supplied side friction at the horizontal curves having the radius less than or equal to 200 m and the amount of difference was also inversely proportional to the radius of the horizontal curves.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.377-379
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• 2007

To reduce the chattering errors of reed switch sensors used for automatic remote measurement of water supply system, a reed switch sensor was analyzed and improved. The operation of reed switch sensors can be described as a mechanical contact by approximation of permanent magnet piece to generate an electrical pulse. The reed switch sensors are used in measurement application by detecting the rotational or translational displacement. To apply for flow measurement devices, the reed switch sensors should keep high reliability. They are applied for the electronic digital type of water flow meters. The reed switch sensor is just installed simply on the mechanical type flow meter. A small magnet is attached on a pointer of the water meter counter rotor. Inside the reed sensor, two steel leaf springs make mechanical contact and apart as rotation of flow meter counter. The counting electrical contact pulses can be converted as the water flow amount. The MCU sends the digital flow rate data to the server using the wireless communication network. But it occurs data difference or errors by chattering noise. The reed switch sensor contains chattering error by it self at the force equivalent position. The vibrations such as passing car near to the switch sensor installed location. In order to reduce chattering error, most system uses just software methods for example using filter and also statistical calibration methods. The chattering errors were reduced by changing leaf spring structure using mechanical hysteresis characteristics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.1 s.232
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• pp.71-79
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• 2005

For the non-premixed interacting jet flames, it has been reported that if eight small nozzles are arranged along the circle of $40{\sim}72$ times the diameter of single jet, the flames are not extinguished even in 200m/s. In this research, experiments were extended to the partially premixed cases to reduce both flame temperature and NOx emission. Nine nozzles were used- eight was evenly located along the perimeter of the imaginary circle and one at the geometric centre. The space between nozzles, S, the equivalence ratio, ${\phi}$, the exit velocity and the role of the jet from the centre nozzle were considered. Normally, flame was lifted and flame base was located inside the imaginary circle made by the nozzle. As nozzles went away from each other, blowout velocity increased and then decreased. The maximum blowout velocity diminished with the addition of air to the fuel stream. When the fuel and/or oxidizer were not fed through the centre nozzle, the maximum blowout velocity obtained by varying S and ${\phi}$ was around 160m/s. Optimum nozzle separation distance at which peak blowout velocity obtained also decreased with ${\phi}$ decrease. Flame base became leaner as approaching to the blowout. It seemed that lots of air was supplied to the flame stabilizing region by the entrainment and partially premixing. To approve this idea and to enhance the blowout velocity, fuel was supplied to the centre region. With the small amount of fuel through the centre nozzle, partially premixed flame could be sustained till sonic velocities. It seemed that the stabilizing mechanism in partially premixed interacting flame was different from that of non-premixed case because one was stabilized by the fuel supply through the centre nozzle but the other destabilized.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.480-484
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• 2013

Since SiOC was introduced as an anode material for lithium ion batteries, it has been studied with different chemical compositions and microstructures using various silicon based inorganic polymers. Poly(phenyl carbosilane) is a SiOC precursor with a high carbon supply in the form of the phenyl unit, and it has been investigated for film applications. Unlike any other siloxane-based polymers, oxygen atoms must be utilized in an oxidation process, and the amount of oxygen is controllable. In this study, SiOC anodes were prepared using poly(phenyl carbosilane) with different heat treatment conditions, and their electrochemical properties as an anode material for lithium ion batteries were studied. In detail, cyclic voltammetry and charge-discharge cycling behavior were evaluated using a half-cell. A SiOC anode which was prepared under a heat treatment condition at $1200^{\circ}C$ after an oxidation step showed stable cyclic performance with a reversible capacity of 360 mAh/g.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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• pp.25-38
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• 2019

This study is to develop a diagnostic model for the effective introduction of smart factories in the manufacturing industry, to diagnose SMEs that have difficulties in building their own smart factory compared to large enterprise, to identify the current level and to present directions for implementation. IT, AT, and OT experts diagnosed 18 SMEs using the "Smart Factory Capacity Diagnosis Tool" developed for smart factory level assessment of companies. They analyzed the results and assessed the level by smart factory diagnosis categories. Companies' smart factory diagnostic mean score is 322 out of 1000 points, between 1 level (check) and 2 level (monitoring). According to diagnosis category, Factory Field Basic, R&D, Production/Logistics/Quality Control, Supply Chain Management and Reference Information Standardization are high but Strategy, Facility Automation, Equipment Control, Data/Information System and Effect Analysis are low. There was little difference in smart factory level depending on whether IT system was built or not. Also, Companies with large sales amount were not necessarily advantageous to smart factories. This study will help SMEs who are interested in smart factory. In order to build smart factory, it is necessary to analyze the market trends, SW/ICT and establish a smart factory strategy suitable for the company considering the characteristics of industry and business environment.

• Korean Journal of Agricultural Science
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• v.48 no.1
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• pp.103-117
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• 2021

The severe effects of climate change, such as global warming and the El Niño phenomenon, have become more prevalent. In recent years, natural disasters such as drought, heavy rain, and typhoons have taken place, resulting in noticeable damage. Korea is affected by droughts that cause damage to rice fields and crops. Societal interest in droughts is growing, and measures are urgently needed to address their impacts. As the demand for high-quality agricultural products expands, farmers have become more interested in water management, and the demand for field irrigation is increasing. Therefore, we investigated water demand in the irrigation of drought-vulnerable crops. Specifically, we determined the water requirements for crops including cabbage, red pepper, apple, and bean in four regions by calculating the consumptive water use (evapotranspiration), effective rainfall, and irrigation capacity. The total consumptive water use (crop evapotranspiration) estimates for Dangjin-si (cabbage), Yesan-gun (apple), Cheongyang-gun (pepper) in Chungnam, and Goesan-gun (bean) in Chungbuk were 33.5, 206.4, 86.1, and 204.5 mm, respectively. The volumes of groundwater available in the four regions were determined to be the following: Dangjin-si, 4,968,000 m³; Yesan-gun, 4,300,000 m³; Cheongyang-gun, 1,114,000 m³, and Goesan-gun, 3,794,000 m³. The annual amounts available for the representative crops, compared to the amount of evapotranspiration, were 313.9% in Dangjin-si, 29.5% in Yesan-gun, 56.1% in Cheongyang-gun, and 20.1% in Goesan-gun.

• Tribology and Lubricants
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• v.37 no.6
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• pp.246-252
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• 2021

Among the engine components of an internal combustion engine, the valve train is a series of systems that supply intake gas to the combustion chamber and operate intake and exhaust valves that discharge exhaust gas. If excessive wear occurs in the valve train system, the suction and exhaust valves do not open and close on time, which leads to abnormal combustion and exhaust gas. In this study, we conduct experiments and analyses on friction and wear characteristics of the valve train system. Moreover, we experimentally study the correlation between the pinball and pinball cap on engine oil lubrication, friction experiment, wear amount analysis, and surface analysis. Specifically, we experiment using Ball on reciprocating tribo-tester and apply commercial engine oil sold on the market engine oil. We construct the experimental conditions for each new oil and oil. Accordingly, the completed specimen was subjected to a confocal microscope to check the wear volume, observe the surface of the specimen, and confirm the elemental components using a scanning microscope (SEM) and an energy dispersion X-ray spectrometer (EDS). Through this experiment, we analyze the friction and wear characteristics of valve train components according to engine oil grade, and the obtained data serve as an effective engine oil management method.

• Journal of Internet Computing and Services
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• v.24 no.5
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• pp.107-120
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• 2023

The public bicycle of Seoul, Ttareungyi, was launched at October 2015 to reduce traffic and carbon emissions in downtown Seoul and now, 2023 Oct, the cumulative number of user is upto 4 million and the number of bike is about 43,000 with about 2700 stations. However, super growth of Ttareungyi has caused the several problems, especially demand/supply mismatch, and thus the Seoul citizen has been complained about out of stock. In this point, this study conducted a real time demand forecasting model to prevent stock out bike at stations. To develop the model, the research team gathered the rental·return transaction data of 20,000 bikes in whole 1600 stations for 2019 year and then analyzed bike usage, user behavior, bike stations, and so on. The forecasting model using machine learning is developed to predict the amount of rental/return on each bike station every hour through daily learning with the recent 90 days data with the weather information. The model is validated with MAE and RMSE of bike stations, and tested as a prototype service on the Seoul Bike Management System(Mobile App) for the relocation team of Seoul City.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.73-76
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• 2009

Generally, wind or solar power system is operated as a stand-alone power system, the efficiency of which could be higher by designing wind-solar combined system considering average wind speed and solar radiation of the desert region, Mongolia. This system is designed to generate electricity for power users and pumps the ground water for irrigation using deep well pump. The ground water can be used for farming or forestation where there is no or little irrigation system. In connection with this study, a renewable energy park, Green Eco Energy Park, was developed at about 50km east of Ulaanbaatar. 3 sets of 10kW wind power generator and 70 kW of solar power module were installed there. The electricity generated from the system is used to on-site office building and deep well pump for ground water pumping. A 10kW stand-alone solar pumping system, which has no rechargeable battery system, is installed to pump the ground water with the amount of generated power. The ground water is stored in 3 artificial ponds and then it is used for raising nursery tree and farming. The purpose of this study is to provide a possible energy solution to desert regions where there is no or little power system. The system also supply power to ground water pump, and the water can be used for farming and forestation, which will also be a solution of preventing desertification or spreading of desert area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.6013-6021
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• 2012

Although there are many patients who suffer from cold hypersensitivity and have a difficult time in living daily lives due to feeling cold at room temperature, it is about true that an accurate diagnostic method and an effective remedy for a cold hypersensitivity have not been developed yet. Therefore, in order to develop traditional medicine equipment for cold hypersensitivity, we have designed new oxygen chamber system which can diagnose cold hypersensitivity with multiple bionic sensors and supply a patient optimum amount of oxygen adaptively to the extent of their illness. In particular, diverging from conventional diagnosis based on the experience of doctor and subjective statements of patient, we introduced accurate method for diagnosis in comparing between output of multiple sensors and threshold derived from clinical trials. After all, the proposed oxygen chamber system will contribute to achieving scientific evidence and manufacturing of korean traditional medicine.