• Journal of KIISE:Information Networking
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• v.33 no.1
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• pp.16-27
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• 2006

The wireless transmission medium inherently broadcasts a signal to all neighbor nodes in the transmission range. Existing asynchronous MAC protocols do not provide a concrete solution for reliable broadcast in link layer. This mainly comes from that an omni-directional broadcasting causes to reduce the network performance due to the explosive collisions and contentions. This paper proposes a reliable broadcast protocol in link taller based on directional antennas, named MDB(MAC protocol for Directional Broadcasting). This protocol makes use of DAST(Directional Antennas Statement Table) information and D-MACA(Directional Multiple Access and Collision Avoidance) scheme through 4-way handshake to resolve the many collision problem wit]1 omni-directional antenna. To analyze its performance, MDB protocol is compared with IEEE 802.11 DCF protocol [9] and the protocol 2 of reference [3], in terms of the success rate of broadcast and the collision rate. As a result of performance analysis through simulation, it was confirmed that the collision rate of the MDB protocol is lower than those of IEEE 802.11 and the protocol 2 of reference [3], and that the completion rate of broadcast of MDB protocol is higher than those of IEEE 802.11 and the protocol 2 of reference [3].

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.11
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• pp.393-402
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• 2014

We have experienced an explosive increase of the IoT(Internet of Things) technology based devices including smart phones and the wireless communications. Also the growing power consumption in IEEE 802.11 WLANs(Wireless LANs) driven by these dramatic increases in not only mobile users and but also wireless APs(Access Points). To reduce the power consumption, this paper proposes a wireless AP power saving algorithm, which minimizes the transmission power without decrease the transmission and carrier sense ranges. A wireless AP which is use in our algorithm checks its own original coverage periodically for whether there is a new STA(Station) or not when its transmission power is decreased. Moreover, if there are no signaling message to connect the wireless AP, it changes its operation mode Wake-up to sleep. A Result shows that the proposed AP algorithm can reduce the total power consumption of the wireless AP approximated 18% and 35% compared to the conventional wireless AP with and without the existing power saving algorithm, respectively.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.14 no.5
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• pp.43-59
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• 2019

The promotion of social economy is one of the Korean government's top 100 initiatives. As of August 2019, there are 2,249 certified social enterprises in Korea, showing explosive growth with a 41-fold increase from 2007 when the Social Enterprise Promotion Act was first enacted. Currently, the discussion of the sustainability of social-economic organizations is lively, including the issue of changing the certification system to the registration system. Noting the unusual management structure of social enterprise - seeking both social and economic value, this study identifies factors affecting the performance of social enterprises. The study focuses on an empirical investigation of the relationships between characteristics of entrepreneurs' experiences in social economy, strategic competency, the extent to which they seek social value, and their performance. This study is unique in social enterprise research due to its approach to the hybrid management structure of social enterprise with a focus on entrepreneurs' characteristics. Accordingly, this empirical investigation focuses on how social-value seeking mediates the relationships between strategic competency emphasized in typical for-profit enterprises, the characteristics of experiences stressed in social-economic organizations, and the performance of social enterprises. The study findings suggest that, firstly, social entrepreneurs must seek social value as a top priority and improve economic performance using strategic competency to keep pursuing social value, and secondly, social-value seeking must be founded upon entrepreneurs' understanding and experiences in social economy. Practical implications of the study findings include concrete directions for training in social enterprises offered by relevant agencies and the establishment of competency models for current and future entrepreneurs.

• Journal of the Korea Society for Simulation
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• v.27 no.1
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• pp.101-109
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• 2018

Field experiments as well as numerical analyses with finite element analysis codes are two valuable and complemental ways to understand the structural response under explosive blast load. However, there seems to be only limited information available about finite element analysis and experimental validation on the response of structural components under internal explosions. For complementary use of the two ways, the numerical analyses should be validated with field experiments by comparing their results. In this paper, a small-scaled reinforced concrete building with a room is employed for experimental investigations. An amount of TNT is detonated at the center of the room. Pressure at three different sites in the room, displacement of centers of two walls, and damage patterns of four walls are measured and compared to results from numerical analyses. The experimental results are much similar to the numerical analyses results. The finite element analysis code ANSYS AUTODYN is employed to numerically analyze both pressure distribution inside the room and response of walls subjected to blast pressure. The feasibility and validity of the numerical analysis on the reponses of structural components under internal explosions are discussed in terms of structural damage assessment, and evaluated as the same damage in the analysis and the experiments.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.790-803
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• 2019

The dioctyl terephthalic acid (DOTP) process produces plastic plasticizers by esterification of terephthalic acid with powder in the form of octanol. In this study, the dust explosion characteristics of terephthalic acid directly injected into the manhole in the form of powder in the presence of flammable solvent or vapor in the reactor of this process were investigated. Dust particle size and particle size distribution dust characteristics were investigated, and pyrolysis characteristics of dust were investigated to estimate fire and explosion characteristics and ignition temperature. Also, the minimum ignition energy experiment was performed to evaluate the explosion sensitivity. As a result, the average particle size of terephthalic acid powder was $143.433{\mu}m$. From the thermal analysis carried out under these particle size and particle size distribution conditions, the ignition temperature of the dust was about $253^{\circ}C$. The lower explosive limit (LEL) of the terephthalic acid was determined to be $50g/m^3$. The minimum ignition energy (MIE) for explosion sensitivity is (10 < MIE < 300) mJ, and the estimated minimum ignition energy (Es) based on the ignition probability is 210 mJ. The maximum explosion pressure ($P_{max}$) and the maximum explosion pressure rise rate $({\frac{dP}{dt}})_{max}$ of terephthalic acid dust were 7.1 bar and 511 bar/s, respectively. The dust explosion index (Kst) was 139 mbar/s, corresponding to the dust explosion grade St 1.

• The Journal of Bigdata
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• v.6 no.1
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• pp.179-196
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• 2021

With the spread of untact culture resulting from the Covid-19 pandemic, the size of the car camping market has expanded to minimize contact with others. As a result, SUVs have exceeded sales of sedans, and sales of recreational vehicles (RVs) have increased by 101% compared to the same period last year. Despite the explosive increase in demand for car camping, research on car camping has not matched this increase. Therefore, in this study, we intended to conduct a study focused on car camping users. According to a survey of Naver's famous car camping cafe, it was difficult to find articles, maps, and websites with car camping places. Analysis of car camping websites showed that most only post information about the camping itself, so details of car camping places were not available. Furthermore, according to a survey derived from related prior studies and literature surveys, most users urged solutions to the problem of unauthorized garbage dumping in the car camping locations. In addition, car camping users wanted to receive information on amenities near the car camping places. Therefore, we aimed to establish a car camping website that provides basic information on car camping places and nearby convenience facilities. Moreover, to solve the problem of garbage dumping, we provided a category wherein users can post pictures of clean camping campaigns. We also developed a business model utilizing the certification process of clean camping. The business model is designed with a structure wherein car camping users are rewarded through the clean camping certification process. Compensation for clean camping certification was proposed to be provided through partnerships with domestic automakers, Korea Tourism Organization, and Small Business Market Promotion Agency.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.81-88
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• 2021

In general, a non-explosive nylon wire cutting-based holding and release mechanism has been used to store and deploy deployable solar panels of CubeSat. However, with this method, accessing the solar panel's access port for charging the cube satellite's battery and electrical inspection and testing of the PCB and payloads while the solar panel is in storage is difficult. Additionally, the mechanism must have a reliable release function in an in-orbit environment, and reusability for stow and deploy of the solar panel, which is a hassle for the operator and difficult to maintain a consistent nylon wire fastening process. In this study, we proposed a pin-puller-based solar panel holding and release mechanism that can easily deploy a solar panel without cutting nylon wires by separating constraining pins. The proposed mechanism's release function and performance were verified through a solar panel deployment test and a maximum separation load measurement test. Through this, we also verified the design feasibility and effectiveness of the pin-puller-based separation device.

• The Journal of the Korea Contents Association
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• v.19 no.7
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• pp.384-392
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• 2019

Big data-related research that deals with the amount of explosive information in the era of the Fourth Industrial Revolution is actively underway. Big data is an essential element that promotes the development of artificial intelligence with a wide range of data that become learning data for machine learning, or deep learning. The use of deep learning and big data in various fields has produced meaningful results. In this paper, we have investigated the use of Big Data in the cultural arts industry, focusing on video contents. Noteworthy is that big data is used not only in the distribution of cultural and artistic contents but also in the production stage. In particular, we first looked at what kind of achievements and changes the Netflix in the US brought to the OTT business, and analyzed the current state of the OTT business in Korea. After that, Netflix analyzed the success stories of 'House of Cards', which was produced / circulated through 'Deep Learning' cinematique, which is a prediction algorithm, through accumulated customer data. After that, FGI (Focus Group Interview) was held for cultural and artistic contents experts. In this way, the future prospects of Big Data in the domestic culture and arts industry are divided into technical aspect, creative aspect, and ethical aspect.

• The Journal of the Korea Contents Association
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• v.19 no.1
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• pp.682-695
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• 2019

In recent years, using a connected platform, companies have built and implemented a mobile viral marketing strategy to attract new customers and to have long-term relationships with existing customers. The emergence of interactive Web 2.0 has led to an explosive increase in customer engagement, and practitioners have become interested in connected platform to build close relationships with their customers. However, the study on the effectiveness of various customer influx methods using the connected platform that companies utilize for an increase of customer participation is insufficient. Based on the theoretical study of Sashi (2012), this study analyzes the actual mobile viral promotion of company A's open market shopping mall for the purpose of bringing new customers and having a long-term relationship with the new customers[1]. By analyzing the customer engagement type, the implications for the effectiveness of mobile viral promotion are suggested. First, as a result of the immediate effect of online viral promotion, promotions are partially effective in attracting new customers. Second, as a result of examining the change of customer engagement type in order to find out the long - term effect of online viral promotion, it was found that in most cases, new customers were not become satisfied customers and, Laggard Effect, which takes time to become a satisfied customer, has been confirmed.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.6
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• pp.113-123
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• 2018

There are no studies related to the cryptocurrency exchange, unlike the explosive topic and the active transaction of the cryptourrency around the world. In this study, variables were constructed based on the previous researches to examine the effects of e-service qualities(information quality, transaction quality, design quality, safety quality), satisfaction and continuance intention of cryptocurrency exchange. The samples consist of 180 survey data drawn from the users of cryptocurrency exchange. The collected data were analyzed by SPSS 24.0 and AMOS 21.0. According to results of the reliability and validity test, all were found reliable, and all items were included. As a result of hypothesis testing through path analysis, First, the e-service qualities (information quality, transaction quality, design quality, safety quality) of the cryptocurrency exchange showed positive effects on satisfaction at the significance level of 1% and 5%. Second, e-service qualities (information quality, transaction quality, design quality, safety quality) of the cryptocurrency exchange were found to have positive effects on continuance intention at the significance level of 1% and 5%. Third, the satisfaction of the cryptocurrency exchange has a positive effect on continuance intention at 1% level of significance.