• KIPS Transactions on Software and Data Engineering
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• v.3 no.2
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• pp.81-86
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• 2014

In this paper, we present an effective sound classification system for recognizing the real-time context of a smartphone user. Our system avoids unnecessary consumption of limited computational resource by filtering both silence and white noise out of input sound data in the pre-processing step. It also improves the classification performance on low energy-level sounds by amplifying them as pre-processing. Moreover, for efficient learning and application of HMM classification models, our system executes the dimension reduction and discretization on the feature vectors through k-means clustering. We collected a large amount of 8 different type sound data from daily life in a university research building and then conducted experiments using them. Through these experiments, our system showed high classification performance.

• Journal of Sensor Science and Technology
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• v.32 no.3
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• pp.140-146
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• 2023

Water quality is crucial for human health and the environment. Accurate measurement of the quantity of organic carbon in water is essential for water quality evaluation, identification of water pollution sources, and appropriate implementation of water treatment measures. Total organic carbon (TOC) analysis is an important tool for this purpose. Although other methods, such as chemical oxygen demand (COD) and biochemical oxygen demand (BOD) are also used to measure organic carbon in water, they have limitations that make TOC analysis a more favorable option in certain situations. For example, COD requires the use of toxic chemicals, and BOD is time-consuming and can produce inconsistent and unreliable results. In contrast, TOC analysis is rapid and reliable, providing accurate measurements of organic carbon content in water. However, common methods for TOC analysis can be complex and energy-intensive because of the use of high-temperature heaters for liquid-to-gas phase transitions and the use of acid, which present safety risks. This study focuses on a TOC analysis method using TiO₂ photocatalysis, which has several advantages over conventional TOC analysis methods, including its low cost and easy maintenance. For TiO₂, rutile and anatase powders are mixed with an inorganic binder and spray-coated onto a glass fiber substrate. The TiO₂ powder and inorganic binder solutions are adjusted to optimize the photocatalytic reaction performance. The TiO₂ photocatalysis method is a simple and low-power approach to TOC analysis, making it a promising alternative to commonly used TOC analysis methods. This study aims to contribute to the development of more efficient and cost-effective approaches for water quality analysis and management by exploring the effectiveness and reliability of the developed equipment.

• Journal of the Institute of Convergence Signal Processing
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• v.25 no.1
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• pp.46-51
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• 2024

Drone was first used for military purposes but as the range of use has recently expanded. It is being widely used in various industrial fields such as agriculture, service, logistics, and leisure. Lithium polymer batteries are lightweight and highly efficient, so they are mainly used as power supplies for drones. Accordingly, the need for lightweight and high energy density lithium polymer batteries has increased in order to supply stable power to drone. However, lithium polymer batteries can lead to ignition and explosion due to overcharging, short circuit, etc., so they must be used with a protective circuit installed. The protection circuit consists of a protection IC that monitors the voltage of the lithium polymer battery and a dual N-channel MOSFET that acts as a switch in case of overcharge and overdischarge. Therefore, this paper was implemented in one package form using a battery protection IC and a MOSFET semiconductor die chip serving as a switch. When implemented as a one chip package IC, at least 67% of savings compared to existing parts can be achieved.

• 한국무역상무학회:학술대회논문집
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• 2006.06a
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• pp.45-72
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• 2006

The Equator Principles are a set of voluntary environmental and social guidelines for ethical project finance. These principles commit banks and other signatories to not finance projects that fail to meet these guidelines. The principles were conceived in 2002 on an initiative of the International Finance Corporation and launched in 2003. Since then, dozens of major banks have adopted the Principles, and with these banks among them accounting for more than three quarters of all project loan market volume the Principles have become the de facto standard for all banks and investors on how to deal with potential social and environmental effects of projects to be financed. While regarding the Principles an important initiative, NGOs have criticised the Principles for not producing real changes in financing activities and for allowing projects to go through that should have been screened out by the Principles, such as the Sakhalin-II oil and gas project in Russia. In early 2006, a process of revision of the principles was begun. The Equator Principles state that endorsing banks will only provide loans directly to projects under the following circumstances: - The risk of the project is categorized in accordance with internal guidelines based upon the environmental and social screening criteria of the International Finance Corporation (IFC). - For all medium or high risk projects (Category A and B projects), sponsors complete an Environmental Assessment, the preparation of which must meet certain requirements and satisfactorily address key environmental and social issues. - The Environmental Assessment report addresses baseline environmental and social conditions, requirements under host country laws and regulations, applicable international treaties and agreements, sustainable development and use of renewable natural resources, protection of human health, cultural properties, and biodiversity, including endangered species and sensitive ecosystems, use of dangerous substances, major hazards, occupational health and safety, fire prevention and life safety, socio-economic impacts, land acquisition and land use, involuntary resettlement, impacts on indigenous peoples and communities, cumulative impacts of existing projects, the proposed project, and anticipated future projects, participation of affected parties in the design, review and implementation of the project, consideration of feasible environmentally and socially preferable alternatives, efficient production, delivery and use of energy, pollution prevention and waste minimization, pollution controls (liquid effluents and air emissions) and solid and chemical waste management. - Based on the Environmental Assessment, Equator banks then make agreements with their clients on how they mitigate, monitor and manage those risks through an 'Environmental Management Plan'. Compliance with the plan is required in the covenant. If the borrower doesn't comply with the agreed terms, the bank will take corrective action, which if unsuccessful, could ultimately result in the bank canceling the loan and demanding immediate repayment. - For risky projects, the borrower consults with stakeholders (NGO's and project affected groups) and provides them with information on the risks of the project. - If necessary, an expert is consulted. The Principles only apply to projects over 50 million US dollars, which, according to the Equator Principles website, represent 97% of the total market. In early 2006, the financial institutions behind the Principles launched stakeholder consultations and negotiations aimed at revising the principles. The draft revised principles were met with criticism from NGO stakeholders, who in a joint position paper argued that the draft fails by ignoring the most serious critiques of the principles: a lack of consistent and rigorous implementation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2A
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• pp.152-161
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• 2007

IEEE 802.11 Wireless Local Area Network (WLAN) became a prevailing technology for the broadband wireless Internet access, and new applications such as Voice over WLAM (VoWLAN) are fast emerging today. For the battery-powered VoWLAN devices, the standby time extension is a key concern for the market acceptance while today's 802.11 is not optimized for such an operation. In this paper, we propose a novel Idle Mode operation, which comprises paging, idle handoff, and delayed handoff. Under the idle mode operation, a Mobile Host (MH) does not need to perform a handoff within a predefined Paging Area (PA). Only when the MH enters a new PA, an idle handoff is performed with a minimum level of signaling. Due to the absence of such an idle mode operation, both IP paging and Power Saving Mode (PSM) have been considered the alternatives so far even though they are not efficient approaches. We implement our proposed scheme in order to prove the feasibility. The implemented prototype demonstrates that the proposed scheme outperforms the legacy alternatives with respect to energy consumption, thus extending the standby time.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.3
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• pp.189-197
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• 2014

Collection and management of various information related to the ballast water are the essential components for the efficient implementation of the IMO Ballast Water Management Convention. Based upon the ballast water risk assessment and information system developed by other states, regions or even at global level, an integrated information system has been established to be applied to our domestic ports. The integrated information system is composed of four DataBases (DB) which are the Shipping DB, Ballast water DB, Port Environment DB and Species DB. The Shipping DB has been established based on the data collected from the Port Management Information System (Port-MIS). For the Ballast water DB, Ballast water has only been estimated by the loading/unloading of the cargoes as the convention has not come into effect yet. The Port Environment DB and Species DB are being established based on the reference documents and existing and newly collected monitoring data. From these DB, the integrated information system will be able to provide a base for the information search, statistic analysis and risk assessment of ballast water. Once the convention comes into effect, this integrated information system will be applied to manage the domestic ballast water discharge and also the port management.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.2
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• pp.61-67
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• 2018

Welding preheating means that the surface of the base material to which the metal is welded before the main welding is heated to a constant temperature. It prevents the cracks of the adjacent influences such as reduction of material hardening degree by controlling the cooling rate, suppression of segregation of impurities, prevention of thermal deformation, and moisture removal. For this reason, it is a necessary operation for high quality welding. Induction heating is an efficient heating method that converts electric energy into heat energy by applying electromagnetic induction phenomenon. Compared with combustion heat generated by gas and liquid, it is clean, stable, and economical as well as rapid heating. It can be heated regardless of the shape, depth and material of the heating body by modifying the shape of the frequency and the coil with a simple structure. In this paper, we implemented a low frequency welding preheating system using induction heating technique and observed the temperature changes of coil resistance, inductance and automotive transmission parts according to the height of each transmission in winding coil for three kinds of automotive transmission parts. We confirmed that the change of current is a very important factor in the low frequency heating.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1143-1150
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• 2023

The global climate crisis and the implementation of low-carbon policies have led to a growing interest in renewable energy and a growing number of related industries. Among them, solar power is attracting attention as a representative eco-friendly energy that does not deplete and does not emit pollutants or greenhouse gases. As a result, the supplement of solar power facility is increasing all over the world. However, solar power is easily affected by the environment such as geography and weather, so accurate solar power forecast is important for stable operation and efficient management. However, it is very hard to predict the exact amount of solar power using statistical methods. In addition, the conventional prediction methods have focused on only short- or long-term prediction, which causes to take long time to obtain various prediction models with different prediction horizons. Therefore, this study utilizes a many-to-many structure of a recurrent neural network (RNN) to integrate short-term and long-term predictions of solar power generation. We compare various RNN-based very short- and long-term prediction methods for solar power in terms of MSE and R² values.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.1
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• pp.13-18
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• 2014

Sensor nodes are used for monitoring and collecting the environmental data via wireless sensor network. The wireless sensor network with various sensor nodes draws attention as a key technology in ubiquitous computing. Sensor nodes has very small memory capacity and limited power resource. Thus, it is essential to have energy efficient strategy for the sensor nodes. Since the sensor nodes are operating on the same frequency bands with ISM frequency bands, the interference by the devices operating on the ISM band degrades the quality of communication integrity. In this paper, the convolutional code is proposed instead of ARQ for the error control for the sensor network. The proposed convolutional code was implemented and the BER performance is measured. For the fixed transmitting powers of -19.2 dBm and -25dBm, the BER with various communication distances are measured. The packet loss rate and the retransmission rate are calculated from the measured BER. It is shown that the porposed method obtained about 9~12% and 12-19% reduction in retransmission rate for -19.2 dBm and -25 dBm respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.1022-1025
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• 2009

USN(Ubiquitous Sensor Network) is a core infrastructure that makes come true the u-life in the ubiquitous society through various services of area such as u-city and u-Health. Therefore, we need to reseach about the domestic standards to establish the core technique of USN. Currently, the status of USN standards is most of technical standard and reseach that are technology for sensor node implementation and a protocol for energy-efficient communication and interlock with existing network. But, Standard and reseach for sensor network, integration management of heterogeneous sensor networks for USN application, sensing data management and USN database structure definition such as application and middleware are weak level. In this paper, we researched for standard development of the domestic sensor network service and relevant standard analysis to configure SWE(Sensor Web Enablement) of OGC(Open Geospatial Consortium) for standarded plattform technoloy in part of the middleware. Also we researched that it's a connection between domestic TTA (Telecommunications Technology Association) standards and SWE Standard. Finally, we researched for standard service plattform architecture on sensor network through analysis on the possibility of applying OGC-based services platform.