• International Journal of Highway Engineering
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• v.16 no.2
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• pp.19-24
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• 2014

PURPOSES : The study objective was to evaluate rheology and physical properties of SBS-modified warm-mix asphalt (WMA) binders in comparison with hot-mix asphalt (HMA) binders. METHODS : Four different SBS polymers were used to prepare polymer-modified asphalt (PMA) binders, and three different warm-mix additives (WAD) were used to prepare a total of 12 WMA PMA binders. The kinematic viscosity was measured at 115, $135^{\circ}C$. The PG was determined using DSR and BBR. The pass/fail (P/F) temperatures for high and low PG grading were evaluated for HMA PMA and WMA PMA binders. RESULTS : PG 76-22 binders could be prepared by modifying the base binder (PG 64-22) using 4.5 wt% of SBS. The kinematic viscosity (KV) of SBS PMA was increased by 3 times higher than that of base asphalt. The SBS PMA with WAD showed 10% lower KV than that of the normal SBS PMA at $115^{\circ}C$ The high P/F temperatures showed almost no difference between HMA PMA and WMA PMA binders. The high P/F temperature showed very high correlations with KV ($R^2$ > 0.97). The result of SBS modification caused increase of low P/F temperature by $2.7^{\circ}C$ on average. CONCLUSIONS : Since the PMA with WAD showed 10% lower KV than normal (HMA) PMA at $115^{\circ}C$, reducing PMA mixture temperature down to a WMA level was possible in this study. The higher KV binders showed the higher P/F temperature. There was almost no change in high P/F temperature due to the use of WAD. The SBS PMA, showing an increased low P/F temperature, might show somewhat poorer performance at low-temperature, even though the lower PG grade was staying at the same level, i.e., $-22^{\circ}C$.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.1-8
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• 2011

The objective of this paper is to evaluate the performance of low $CO_2$ asphalt binder properties using LEADCAP$^{(R)}$(Low Energy and Carbon Asphalt Pavement) additive as function of various aging methods such as RTFO(Rolling thin film oven), Ultraviolet(UV) lay. In order to simulate the short-term aging of asphalt binder that occurs during the hot-mixing asphalt process, the Rolling Thin Film Oven(RTFO) was used. Asphalt binder using LEADCAP$^{(R)}$ is prepared by addition of a photoinitiator activated by ultraviolet lay. The mechanical and rheological properties of the asphalt binder were estimated using UTM(Universal Testing Machine) and DSR(Dynamic Shear Rheometer). The test results showed that the asphalt binder using LEADCAP$^{(R)}$ additive was improved the rutting resistance at testing temperature ($70^{\circ}C$) and increased tensile strength at low temperature. Also, Thermal analysis shows that the Melting Point(Tm) of asphalt binder using LEADCAP$^{(R)}$ additive was constant although the asphalt binder was aged by Ultraviolet.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11B
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• pp.1607-1617
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• 2010

In this paper we propose MA-CBRP, mesh adaptive algorithm for wireless mesh networks. MA-CBRP is a hybrid algorithm based on ad-hoc CBRP protocol. In MA-CBRP, the mesh router periodically sends the ANN message as like Hello-message in CBRP. ANN message allows to all clients periodically store a route towards the mesh-router and renewal information in their routing cache. While CBRP periodically reply Hello-message, MA-CBRP does not reply to achieve less overhead. After receiving ANN message, mesh client send JOIN message to mesh router when the route towards mesh router changed. at the same time Register the entry to mesh router, it can achieve to reduce overhead of control the route and shorten the time to find route. consequently, MA-CBRP shows 7% reduced overhead and shortened time to find route than CBRP with regardless of clients number.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.129-132
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• 2008

The generally six-port phase correlator is comprised of a wilkinson power divider and three $90^{\circ}$ hybrid coupler, got bandwidth performance of less than 10%. in this paper, the six-port phase correlator using two section power divider has 33% bandwidth and external matching hybrid coupler has 15% bandwidth was designed with the center frequency of 2.5GHz. Analysis of the simulation result indicates that RF port and LO port got frequency bandwidth of 13%. Insert loss performance of fabricated six-port phase correlator is incremented, but bandwidth resembles simulation result. And phase tolerance within bandwidth is less than $90^{\circ}$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.632-641
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• 2007

Since the mobile node acts as the router, the Mobile Ad Hoc network requires the security methods that are different from that of network of the wire environment. Also, since the total network can't be included in the transmission area of the mobile node, when one node sends the message to the other node, we need the middle node. But if the middle node is the unreliable malicious node, we can't guarantee the secure message transmission. Also, because all nodes configuring the network are the mobile nodes, they use the restricted battery capacity and the restricted resources. Therefore, because we have trouble performing the encryption that many resources are required when we sending the message, it is vulnerable to the security than the network of the wire environment. Last, because the network topology continues to change by the mobility of nodes configuring the network, we need the security measure that matches the network characteristics. We suggest the routing attack detection for performance enhancement of AODV protocol in Mobile Ad Hoc networks.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.1075-1080
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• 2004

Dextransucrase (DSRB742) from Leuconostoc mesenteroides NRRL B-742CB is a glucosyltransferase that catalyzes the synthesis of dextran using sucrose, or the synthesis of oligosaccharides when acceptor molecules, like maltose, are present. The DSRB742 gene (dsrB742) was cloned and the properties were characterized. In order to identify critical amino acid residues, the DSRB742 amino acid sequence was aligned with glucosyltransferase sequences, and three amino acid residues reported as sucrose binding amino acids in Streptococcus glucosyltransferases were selected for site-directed mutagenesis experiments. Asp-533, Asp-536, and His-643 were independently replaced with Ala or Asn. D533A and D536A dextransucrases showed reduced dextran synthesis activities, 2.3% and 40.8% of DSRB742 dextransucrase, respectively, and D533N, D536N, H643A, end H643N dextransucrases showed complete suppression of dextran synthesis activities altogether. Additionally, D536N dextransucrase showed complete suppression of oligosaccharide synthesis activities. However, modifications at Asp-533 or at His-643 retained acceptor reaction activities in the range of 8.4% to 21.3% of DSRB742 acceptor reaction activity. Thus at least two carboxyl groups of Asp-533 and Asp-536, and His-643 as a proton donor, are essential for the catalysis process.

• Journal of Korea Multimedia Society
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• v.7 no.8
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• pp.1066-1077
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• 2004

Dramatic increase in the number of Internet users want highly qualified service of continuous media contents on the web. To solve these problems, we present two network caching schemes(PPC, PPCwP) which consider the characteristics of continuous media objects and user access pattern in this paper. While there are plenty of reasons to create rich media contents, delivering this high bandwidth contents over the internet presents problems such as server overload, network congestion and client-perceived latency. PPC scheme periodically calculates the popularity of objects based on the playback quantity and determines the optimal size of the initial fraction of a continuous media object to be cached in proportion to the calculated popularity. PPCwP scheme calculates the expected popularity using the series information and prefetches the expected initial fraction of newly created continuous media objects. Under the PPCwP scheme, the initial client-perceived latency and the data transferred from a remote server can be reduced and limited cache storage space can be utilized efficiently. Trace-driven simulation have been performed to evaluate the presented caching schemes using the log-files of iMBC. Through these simulations, PPC and PPCwP outperforms LRU and LFU in terms of BHR and DSR.