• Title, Summary, Keyword: Aggregation

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A Minimum Missing Aggregation Policy for RSS Services (RSS 서비스를 위한 최소 누락 수집 정책)

  • Han, Young-Geun;Lee, Sang-Ho
    • Journal of KIISE:Databases
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    • v.35 no.5
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    • pp.391-399
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    • 2008
  • RSS is the XML-based format for the syndication of web contents, and users aggregate RSS feeds with RSS feed aggregators. In order to effectively aggregate RSS feeds, an RSS aggregation policy is necessary. In this paper, we first propose an aggregation policy to minimize the number of postings being missed within an aggregation. Second, we analyze and compare our aggregation policy with existing aggregation policies. Our analysis reveals that our aggregation policy can reduce approximately 23% of the aggregation missing in comparison with the other aggregation policies while it increases only 6% of the aggregation delay.

Protein Aggregation and Adsorption upon In vitro Refolding of Recombinant Pseudomonas Lipase

  • Lee, Young-Phil;Rhee, Joon-Shick
    • Journal of Microbiology and Biotechnology
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    • v.6 no.6
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    • pp.456-460
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    • 1996
  • Recombinant Pseudomonas lipase was used to study protein aggregation and adsorption upon in vitro refolding. Protein adsorption as well as aggregation was responsible for major side reactions upon in vitro refolding as a function of protein concentration. The optimal range of protein concentration was determined by the relative contribution of protein aggregation and adsorption. Above the optimal range, the yield of active lipase inversely correlated with protein aggregation, showing a competition between folding and aggregation. However, adsorption of protein rather than protein aggregation is thought to contribute as a major side reaction of the refolding process at sub-optimal concentrations at which the formation of aggregates should be more reduced. Protein aggregation was influenced by the amount of guanidine hydrochloride in the refolding solvent. The refolding temperature was a critical factor determining the extent of protein aggregation. The refolding yield was also affected by the dilution fold and dilution mode, which suggests that the refolding process might kinetically compete with the rate of mixing.

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Measurement of cell aggregation characteristics by analysis of laser-backscattering in a microfluidic rheometry

  • Shin, Se-Hyun;Hou, J.X.;Suh, Jang-Soo
    • Korea-Australia Rheology Journal
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    • v.19 no.2
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    • pp.61-66
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    • 2007
  • The aggregation characteristics of red blood cells (RBCs) are known as important factors in the microvascular flow system, and increased RBC aggregation has been observed in various pathological diseases, such as thrombosis and myocardial infarction. This paper describes a simple microfluidic device for measuring the RBC aggregation by integrating a microfluidic slit rheometry and laser-backscattering technique. While a decreasing-pressure mechanism was applied to the microfluidic rheometry, a syllectogram (the light intensity versus time) showed an initial increase and a peak caused by the high shear stress-induced disaggregation, immediately followed by a decrease in the light intensity due to RBC aggregation. The critical shear stress (CST) corresponding to the peak intensity was examined as a new index of the RBC aggregation characteristics. The CST of RBCs increased with increasing aggregation-dominating protein (fibrinogen) in the blood plasma. The essential feature of this design was the combination of the rheometric-optic characterization of RBC aggregation with a microfluidic chip, which may potentially allow cell aggregation measurements to be easily carried out in a clinical setting.

Improved Method for "Aggregation Based on Situation Assessment" ("상황 평가에 기반을 둔 병합"을 위한 개선 방법)

  • Choe, Dae-Yeong
    • The KIPS Transactions:PartB
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    • v.8B no.6
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    • pp.669-674
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    • 2001
  • In order to reflect the aggregation situation in the aggregation process, aggregation based on situation assessment (ASA) method was proposed in [1]. It consists of the situation assessment model (SAM) and the ASA algorithm. In the SAM, the value of parameter, p, is transformed into the nearest integer value [1]. The integer-typed output of SAM is used as input for an aggregation. The integer-typed output of SAM indicates the current degree of aggregation situation. The ASA algorithm produces at most finite several aggregation results between min and max. In the sequel, the ASA method can not properly handle the applications with the more sophisticated aggregation results between min and max. In order to solve this problem, we propose two improved ASA (I-ASA) methods. In these I-ASA methods, we allow the value of parameter of SAM to be a real number, and suggest two improved ASA algorithms to make continuous aggregation results between min and max. These I-ASA methods can handle both a precise aggregation and an approximate aggregation. Therefore, when compared to the ASA method [1], the proposed I-ASA methods have advantages in that they can handle the applications with the more sophisticated aggregation results and can be used in the more general applications for aggregations.

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Mechanism of Vibrio vulnificus Cytolysin on Rat Platelet Aggregation (Vibrio vulnificus cytolysin의 흰쥐 혈소판 응집 기전)

  • 김현철;채수완;이병창;은재순
    • YAKHAK HOEJI
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    • v.43 no.6
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    • pp.802-808
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    • 1999
  • Vibrio vulnificus cytolysin has been incriminated as one of the important virulence determinants in V. vulnificus infection. In the present study, the effects of Vibrio vulnificus cytolysin on platelets were examined. Vibrio vulnificus cytolysin induced platelet aggregation and increased intracellular calcium concentration ($[Ca^{2+}]_i$) of rat platelets. These effects were abolished in $Ca^{2+}-free$ buffer (2 mM EGTA). Cytolysin also potentiated ADP-and collagen-induced platelet aggregation. Lanthanum (2 mM) inhibited cytolysin-diduced platelet aggregation. However, another $Ca^{2+}$ channel blockers, verapamil ($20{\;}{\mu}M$) or mefenamic acid ($20{\;}{\mu}M$) did not block cytolysin-induced platelet aggregation. Osmotic protectants, sucrose (50 mM) and raffinose (50 nM) suppressed platelet aggregation by 35.9% and 63.4%, respectively. V. vulnificus cytolysin increased membrane conductances of platelet membranes. These results suggest that cytolysin-induced platelet aggregation is mediated via lanthanum sensitive-calcium influx which resulted from the pore formation by V. vulnificus cytolysin.

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Optimal Frame Aggregation Level for Connectivity-Based Multipolling Protocol in IEEE 802.11 Wireless LANs (IEEE 802.11 무선랜에서 연결정보 기반의 멀티폴링 프로토콜을 위한 최적의 프레임 애그리게이션 레벨)

  • Choi, Woo-Yong
    • Journal of Korean Institute of Industrial Engineers
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    • v.40 no.5
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    • pp.520-525
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    • 2014
  • When the PCF (Point Coordinated Function) MAC protocol is combined with the frame aggregation method to enhance the MAC performance in IEEE 802.11 wireless LANs, the formulae for the optimal frame aggregation level for best PCF MAC performance were derived in our previous study. We extend the formulae for the PCF protocol to derive the optimal frame aggregation level for the connectivity-based multipolling MAC protocol in IEEE 802.11 wireless LANs. By simulations, we compare the performances of IEEE 802.11 wireless LANs with the optimal and random frame aggregation levels. Compared with the random frame aggregation level, the optimal frame aggregation level significantly improves the performance of IEEE 802.11 wireless LANs.

Secure and Fine-grained Electricity Consumption Aggregation Scheme for Smart Grid

  • Shen, Gang;Su, Yixin;Zhang, Danhong;Zhang, Huajun;Xiong, Binyu;Zhang, Mingwu
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.4
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    • pp.1553-1571
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    • 2018
  • Currently, many of schemes for smart grid data aggregation are based on a one-level gateway (GW) topology. Since the data aggregation granularity in this topology is too single, the control center (CC) is unable to obtain more fine-grained data aggregation results for better monitoring smart grid. To improve this issue, Shen et al. propose an efficient privacy-preserving cube-data aggregation scheme in which the system model consists of two-level GW. However, a risk exists in their scheme that attacker could forge the signature by using leaked signing keys. In this paper, we propose a secure and fine-grained electricity consumption aggregation scheme for smart grid, which employs the homomorphic encryption to implement privacy-preserving aggregation of users' electricity consumption in the two-level GW smart grid. In our scheme, CC can achieve a flexible electricity regulation by obtaining data aggregation results of various granularities. In addition, our scheme uses the forward-secure signature with backward-secure detection (FSBD) technique to ensure the forward-backward secrecy of the signing keys. Security analysis and experimental results demonstrate that the proposed scheme can achieve forward-backward security of user's electricity consumption signature. Compared with related schemes, our scheme is more secure and efficient.

Antiplatelet Effect of AC7-1 isolated from Ardisia crispa

  • Han, Byung-Hoon;Kang, Young-Hwa;Suh, Dae-Yeon;Park, Man-Ki
    • Proceedings of the Korean Society of Applied Pharmacology
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    • pp.69-69
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    • 1997
  • In the screening of tropical medicinal plants using PAE receptor binding assay, the ether extract of Ardisia crispa showed the potent antagonistic activity. Ardisia crispa have been used to heal the scurf, earache, orchitis, fever and diarrhoea, cough and given to the mother after childbirth to ‘wash out dirty blood’ in Malaysia. By means of activity guided isolation, compound AC7-1 was isolated as the potent PAF antagonist. In this study, antiplatelet effects of compound AC7-1 were examined in vitro platelet aggregation assay using the chronolog aggregometer. Compound AC7-1 inhibited PAF-, collagen-, ADP-, thrombin-induced platelet aggregation in human, rabbit and rat platelet rich plasma. In vitro rabbit platelet aggregation, the IC$\_$50/ value of compound AC7-1 was 5 ${\times}$ 10$\^$-6/ M against PAF(5 ${\times}$ 10$\^$-7/M)-induced aggregation. The IC$\_$50/ values of AC7-1 on PAF-induced platelet aggregation increased with increase of the concentration of PAF used. This result suggested the competitive nature of the AC7-1 antagonism. In vitro rat platelet aggregation, the IC$\_$50/ values of AC7-1 on collagen-, ADP-induced platelet aggregation were 4 ${\times}$ 10$\^$-6/ M, 2 ${\times}$ 10$\^$-5/ M, respectively. Also in vitro human platelet aggregation, AC7-1 potently inhibited both the primary phase and secondary phase of thrombin-induced aggregation.

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Performance Analysis of Two-Level Frame Aggregation in IEEE 802.11n (IEEE 802.11n에서의 2단계 프레임 집약 기법 성능 분석)

  • Song, Tae-Won;Yang, Seong-Yeol;Pack, Sang-Heon;Youn, Joo-Sang
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.13 no.6
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    • pp.1175-1180
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    • 2009
  • Frame Aggregation is a promissing technology for improving MAC throughput in IEEE 802.11n. In IEEE 802.11n, two frame aggregation schemes, Aggregate MSDU (A-MSDU) and Aggregation MPDU (A-MPDU), are defined. In this paper, we analyze the performance the two-level frame aggregation scheme where A-MSDU and A-MPDU are combined. We develop the analytical model for the two-level frame aggregation scheme and present numerical results on the effect of bit error rate, aggregation size, and the number of nodes.

Analysis of Optimized Aggregation Timing in Wireless Sensor Networks

  • Lee, Dong-Wook;Kim, Jai-Hoon
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.3 no.2
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    • pp.209-218
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    • 2009
  • In a wireless sensor network(WSN) each sensor node deals with numerous sensing data elements. For the sake of energy efficiency and network lifetime, sensing data must be handled effectively. A technique used for this is data aggregation. Sending/receiving data involves numerous steps such as MAC layer control packet handshakes and route path setup, and these steps consume energy. Because these steps are involved in all data communication, the total cost increases are related to the counts of data sent/received. Therefore, many studies have proposed sending combined data, which is known as data aggregation. Very effective methods to aggregate sensing data have been suggested, but there is no means of deciding how long the sensor node should wait for aggregation. This is a very important issue, because the wait time affects the total communication cost and data reliability. There are two types of data aggregation; the data counting method and the time waiting method. However, each has weaknesses in terms of the delay. A hybrid method can be adopted to alleviate these problems. But, it cannot provide an optimal point of aggregation. In this paper, we suggest a stochastic-based data aggregation scheme, which provides the cost(in terms of communication and delay) optimal aggregation point. We present numerical analysis and results.