• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.83-88
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• 2015

Coating materials used in the electron beam (EB) deposition method, which is being studied as one of the fabrication methods of thermal barrier coating, are exposed to high power electron beam at focused area during the EB deposition. Therefore the coating source for EB process is needed to form as ingot with appropriate density and microstructure to sustain their shape and stable melts status during EB deposition. In this study, we tried to find the optimum powder condition for fabrication of ingot of 8 wt% yttria stabilized zirconia which can be used for EB irradiation. It seems that the ingot, which is fabricated through bi-modal type initial powder mixture which consists of tens of micro and nano size particles, was shown better performance than the ingot which is fabricated using monolithic nanoscale powder when exposed to high power EB.

• Journal of the Korean Magnetics Society
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• v.21 no.6
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• pp.219-224
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• 2011

The motion features of sanals inside of the primo vascular system (PVS), that is so-called the Kyungrak system, are investigated under a low static magnetic field by using the anatomy technology and optical microscope. The sanals with a size of about 1 selected and separated from the primo vessel and node of the real PVS inside of the surface of the internal organs are observed from rabbits' abdominal wall and dipped with PBS liquid inside of petri dish. The sanal's moving velocity along the direction of magnetic field (xdirection) and perpendicular to the direction of magnetic field (y-direction) under the low magnetic field of 0 Oe, 20 Oe, 40 Oe, 60 Oe, and 80 Oe, respectively, is observed below a internal temperature of $38^{\circ}C$. Ten sanals' moving velocities versus magnetic field are shown two differently dominant tendencies with an average velocity of 0.9 pixel/s and a random velocity according to the x-direction and y-direction, respectively. This experimental results imply that the rotating motion of sanal with nuclei DNA composed of many inorganic magnetic materials of Mn and Co is monotonically weakened by the increase of applied magnetic field.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.2
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• pp.179-192
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• 2019

Additional frequencies are allocated in maritime digital data exchange to alleviate overload of the VHF data link. The shipborne ad-hoc network (SANET) for this frequencies was subsequently proposed, which provides various IP-based services to ships on behalf of satellite communications. In SANET, a ship should determine its own IP address to achieve IP connectivity to the shore. Accordingly, this paper proposes a SANET configuration (SANETconf) protocol as an IP configuration protocol. SANETconf propagates non-overlapping IP addresses across the network from the shore to ships. A ship obtains its IP address by exchanging Request and Response messages with its neighbors. Therefore, SANETconf eliminates the process of DAD and managing the movement of ships. Extensive simulations were performed to verify the applicability of SANETconf. Based on results, 85% of the ships can determine their own IP address within one frame. Also, SANETconf has a high resource efficiency by using 0.024 percent of resources for IP configuration.

• Journal of the Korea Society of Computer and Information
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• v.26 no.4
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• pp.105-112
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• 2021

In the era of big data, interest in data is exploding. In particular, the development of the Internet and social media has led to the creation of new data, enabling the realization of the era of big data and artificial intelligence and opening a new chapter in convergence technology. Also, in the past, there are many demands for analysis of data that could not be handled by programs. In this paper, an analysis model was designed and verified for classification of unstructured data, which is often required in the era of big data. Data crawled DBPia's thesis summary, main words, and sub-keyword, and created a database using KoNLP's data dictionary, and tokenized words through morpheme analysis. In addition, nouns were extracted using KAIST's 9 part-of-speech classification system, TF-IDF values were generated, and an analysis dataset was created by combining training data and Y values. Finally, The adequacy of classification was measured by applying three analysis algorithms(random forest, SVM, decision tree) to the generated analysis dataset. The classification model technique proposed in this paper can be usefully used in various fields such as civil complaint classification analysis and text-related analysis in addition to thesis classification.

• Journal of Conservation Science
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• v.36 no.6
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• pp.494-504
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• 2020

Ten historic sites (denoted as A- J in this study) of a tomb were found during the construction of the east-west expressway in District 2 of Hyangnam, Hwaseong, which is implemented by the Gyeonggi-do headquarters of the Korea Land & Housing Corporation. Thetombswere first detected at siteH, and further investigations revealed various tombs from the Three Kingdoms period; artifacts such as gilt-bronze shoes and caps were excavated from wooden coffins in the tombs. The pottery examined in this study was the only pottery artifact excavated from the site. Its raw clay was soft and loose, reddish brown, and had quartz and feldspar particles of < 1 mm, which appeared to have been added as reinforcing agents. The firing temperature of the pottery was estimated to be under 800-870 ℃ as the mica remains and tridimite, which is the phase transition mineral of quartz, was not produced; a slight endothermic peak was also detected because of the hydration of sericite at 800 ℃. The condition of the artifact was severely weakened because of various factors, such as soil pressure from the stratum formed over the site and repeated freezing and thawing. The artifact could not be collected alone, and thus, surrounding soil that had attached to the artifact was also collected; the artifact was transported to the laboratory and conservation treatment was conducted in a safe and systematic manner.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.2
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• pp.285-290
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• 2023

Compressors are widely used in high-speed electronic systems and are used to reduce the number of operands in multiplier. The proposed compressor is constructed based on the m-GDI(: modified gate diffusion input) to reduce the propagation delay time. This paper is compared the performance of compressors by applying 4-2, 5-2 and 6-2 m-GDI compressors to the multiplier, respectively. As a simulation results, compared to the 8-bit Dadda multiplier using the 4-2 and 6-2 compressor, the multiplier using the 5-2 compressor is reduced propagation delay time 13.99% and 16.26%, respectively. Also, the multiplier using the 5-2 compressor is reduced PDP(: Power Delay Product) 4.99%, 28.95% compared to 4-2 and 6-2 compressor, respectively. However, the multiplier using the 5-2 compression circuit is increased power consumption by 10.46% compared to the multiplier using the 4-2 compression circuit. In conclusion, the 8-bit Dadda multiplier using the 5-2 compressor is superior to the multipliers using the 4-2 and 6-2 compressors. The proposed circuit is implemented using TSMC 65nm CMOS process and its feasibility is verified through SPECTRE simulation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1B
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• pp.97-103
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• 2009

The decompostion characteristics of NAPL TCE in cement/slag/Fe(II) system were studied with various TCE concentration and amounts of binders (cement/slag) For analyses of the TCE degradation by cement/slag/Fe(II), TCE solution injected using gas-tight syringe after TCE solution dissolved a methanol. Initial concentrations of TCE are 0.42 mM, NAPL condition 11.7 mM and saturated condition 16.8 mM respectively. The result showed that the cases of 8.4 mM and 4.2 mM are decreased 88% of total TCE concentration within 18 days. NAPL condition 11.7 mM was decreased 84% within 50 days and saturated condition 16.8 mM was decreased 60% of total TCE concentration within 60 days respectively. This showed that degradations of TCE in various concentrations were in one kind reaction as pseudo-first-order. TCE was dissolved as aqueous solution before degraded. The reaction rate was increased $0.12day^{-1}$, $0.24day^{-1}$, $0.31day^{-1}$ when the mass of media 0.1, 0.2, 0.3 S/L rate was increased. TCE reaction speed is affected by cement/slag surface ares in this system. When HDTMA, experimental facter, was added, TCE decomposition rate was high despite the high concentration of NAPL. and The decompostion characteristics of NAPL TCE in cement/slag/Fe(II) system were studied by using modeling.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.12
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• pp.1141-1153
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• 2010

This paper introduces ONLIS(Overlay Multicast Network for Live IPTV Service), a novel overlay multicast network optimized to deliver live broadcast IPTV stream. We analyzed IPTV reference model of ITU-T IPTV standardization group in terms of network and stream delivery from the source networks to the customer networks. Based on the analysis, we divide IPTV reference model into 3 networks; source network, core network and access network, ION(Infrastructure-based Overlay Multicast Network) is employed for the source and core networks and PON(P2P-based Overlay Multicast Network) is applied to the access networks. ION provides an efficient, reliable and stable stream distribution with very negligible delay while PON provides bandwidth efficient and cost effective streaming with a little tolerable delay. The most important challenge in live P2P streaming is to reduce end-to-end delay without sacrificing stream quality. Actually, there is always a trade-off between delay & stream quality in conventional live P2P streaming system. To solve this problem, we propose two approaches. Firstly, we propose DSPT(Distributed Streaming P2P Tree) which takes advantage of combinational overlay multicasting. In DSPT, a peer doesn't fully rely on SP(Supplying Peer) to get the live stream, but it cooperates with its local ANR(Access Network Relay) to reduce delay and improve stream quality. When RP detects bandwidth drop in SP, it immediately switches the connection from SP to ANR and continues to receive stream without any packet loss. DSPT uses distributed P2P streaming technique to let the peer share the stream to the extent of its available bandwidth. This means, if RP can't receive the whole stream from SP due to lack of SP's uploading bandwidth, then it receives only partial stream from SP and the rest from the ANR. The proposed distributed P2P streaming improves P2P networking efficiency.

• Korean Journal of Remote Sensing
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• v.37 no.2
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• pp.321-335
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• 2021

Particulate matter (PM10 and PM2.5 with a diameter less than 10 and 2.5 ㎛, respectively) can be absorbed by the human body and adversely affect human health. Although most of the PM monitoring are based on ground-based observations, they are limited to point-based measurement sites, which leads to uncertainty in PM estimation for regions without observation sites. It is possible to overcome their spatial limitation by using satellite data. In this study, we developed machine learning-based retrieval algorithm for ground-level PM10 and PM2.5 concentrations using aerosol parameters from Geostationary Ocean Color Imager (GOCI) satellite and various meteorological parameters from a numerical weather prediction model during January to December of 2019. Gradient Boosted Regression Trees (GBRT) and Light Gradient Boosting Machine (LightGBM) were used to estimate PM concentrations. The model performances were examined for two types of feature sets-all input parameters (Feature set 1) and a subset of input parameters without meteorological and land-cover parameters (Feature set 2). Both models showed higher accuracy (about 10 % higher in R2) by using the Feature set 1 than the Feature set 2. The GBRT model using Feature set 1 was chosen as the final model for further analysis(PM10: R2 = 0.82, nRMSE = 34.9 %, PM2.5: R2 = 0.75, nRMSE = 35.6 %). The spatial distribution of the seasonal and annual-averaged PM concentrations was similar with in-situ observations, except for the northeastern part of China with bright surface reflectance. Their spatial distribution and seasonal changes were well matched with in-situ measurements.

• The Korean Journal of Food And Nutrition
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• v.11 no.3
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• pp.323-328
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• 1998

This study was to investigate regularity of breakfast and food habits of commuting local college students. The regularly breakfast eating rate was found to be 32.9% in man and 26.5% in woman. The mean score of food habits was pretty low, 36.7 out of minimum possible score 12 and maximum 60. The mean score of nutrition attitude was 58.1 out of minimum possible score 18 and maximum 90. This survey showed that skipping breakfast or irregularity of breakfast led to overeating, high fat diet, lot of alcohol and imbalanced diet. It was known that breakfast was the most important among three meals. But having balanced breakfast daily was very difficult according to loss of appetite and busy schedule early in the morning. I suggested carbohydrate food, protein food, and vitamin & mineral food items desirable for nutritionally balanced, easily digestible, tasteful, quick and easily cooking breakfast menu. It was recommended to choose on item out of each of three food categories considering calory(1/3 of daily recommended calory intake for breakfast).