8,161 research outputs found
Detection of the customer time-variant pattern for improving recommender systems
No full textDue to the explosion of e-commerce, recommender systems are rapidly becoming a core tool to accelerate cross-selling and strengthen customer loyalty. There are two prevalent approaches for building recommender systems-content-based recommending and collaborative filtering. So far, collaborative filtering recommender systems have been very successful in both information filtering and e-commerce domains. However, the current research on recommendation has paid little attention to the use of time-related data in the recommendation process. Up to now there has not been any study on collaborative filtering to reflect changes in user interest. This paper suggests a methodology for detecting a user's time-variant pattern in order to improve the performance of collaborative filtering recommendations. The methodology consists of three phases of profiling, detecting changes, and recommendations. The proposed methodology detects changes in customer behavior using the customer data at different periods of time and improves the performance of recommendations using information on changes. (C) 2004 Elsevier Ltd. All rights reserved
A simple, scalable, and stable explicit rate allocation algorithm for MAX-MIN flow control with minimum rate guarantee
No full textIn this paper, we present a novel control-theoretic explicit rate (ER) allocation algorithm for the MAX-MIN flow control of elastic traffic services with minimum rate guarantee in the setting of the ATM available bit rate (ABR) service. The proposed ER algorithm is simple in that the number of operations required to compute it at a switch is minimized, scalable in that per-virtual-circuit (VC) operations including per-VC queueing, per-VC accounting, and per-VC state management are virtually removed, and stable in that by employing it, the user transmission rates and the network queues are asymptotically stabilized at a unique equilibrium point at which MAX-MIN fairness with minimum rate guarantee and target queue lengths are achieved, respectively. To improve the speed of convergence, we normalize the controller gains of the algorithm by the estimate of the number of locally bottle-necked VCs, The estimation scheme is also computationally simple and scalable since it does not require per-VC accounting either. We analyze the theoretical performance of the proposed algorithm and verify its agreement with the practical performance through simulations in the case of multiple bottleneck nodes. We believe that the proposed algorithm will serve as an encouraging solution to the MAX-MIN flow control of elastic traffic services, the deployment of which has been debated long due to their lack of theoretical foundation and implementation complexity
Functional expression of human pyruvate carboxylase for reduced lactic acid formation of Chinese hamster ovary cells (DG44)
No full textTo investigate the effect of human pyruvate carboxylase (hPC) on lactate formation in Chinese hamster ovary (CHO) cell lines, FLAG-tagged hPC was introduced into a dihydrofolate-deficient CHO cell line (DG44). Three clones expressing high levels of hPC, determined by Western blotting using an anti-FLAG monoclonal antibody, and a control cell line were established. Immunocytochemistry revealed that a substantial amount of expressed hPC protein was localized in the mitochondria of the cells. hPC expression did not impair cell proliferation. Rather, it improved cell viability at the end of adherent batch cultures with the serum-containing medium probably because of reduced lactate formation. Compared with control cells, specific lactate production rate of the three clones was decreased by 21-39%, which was because of a decreased specific glucose uptake rate and yield of lactate from glucose. Reduced lactate formation by hPC expression was also observed in suspension fed-batch cultures using a serum-free medium. Taken together, these results demonstrate that through the expression of the hPC enzyme, lactate formation in CHO cell culture can be efficiently reduced
Differences in optimal pH and temperature for cell growth and antibody production between two Chinese hamster ovary clones derived from the same parental clone
No full textTo investigate clonal variations of recombinant Chinese hamster ovary (rCHO) clones in response to culture pH and temperature, serum-free suspension cultures of two antibody-producing CHO clones (clones A and B), which were isolated from the same parental clone by the limiting dilution method, were performed in a bioreactor at pH values in the range of 6.8-7.6, and two different temperatures, 33 degrees C and 37 degrees C. In regard to cell growth, clone A and clone B displayed similar responses to temperature, although their degree of response differed. In contrast, clones A and B displayed different responses to temperature in regard to antibody production. In the case of clone A, no significant increase in maximum antibody concentration was achieved by lowering the culture temperature. The maximum antibody concentration obtained at 33 degrees C (pH 7.4) and 37 degrees C (pH 7.0) were 82.0 +/- 2.6 and 73.2 +/- 4.1 mu g/ml, respectively. On the other hand, in the case of clone B, an approximately 2.5-fold increase in maximum antibody concentration was achieved by lowering the culture temperature. The enhanced maximum antibody concentration of clone B at 33 degrees C (132.6 +/- 14.9 mu g/ml at pH 7.2) was due to not only enhanced specific antibody productivity but also to prolonged culture longevity. At 33 degrees C, the culture longevity of clone A also improved, but not as much as that of clone B. Taken together, CHO clones derived from the same parental clone displayed quite different responses to culture temperature and pH with regards antibody production, suggesting that environmental parameters such as temperature and pH should be optimized for each CHO clone
Substorms associated with azimuthal turnings of the interplanetary magnetic field
No full textWhether the magnetospheric substorms can be triggered by the interplanetary magnetic field (IMF) variations is an important issue in the substorm research. In this work we investigate observationally the relationship between substorm activities and IMF By variations, i.e., azimuthal turnings. We have searched for the EMT's azimuthal turning events for a period of one year using the data from multispacecraft monitoring the solar wind, WIND, IMP 8 and Geotail. Based on specific selection criteria, we have found 11 such events that exhibit pure azimuthal turnings while the IMF B-z remains quasi-steady. These events are found to be mostly in reasonable temporal associations with the substorm activities which were identified by multipoint measurements using the geomagnetic bays, auroral images, geosynchronous energetic particle injections and magnetic dipolarizations. We find an average response time of similar to8-9 min between the substorm onsets and the dayside magnetopause contact times of the IMF By turnings. The results suggest that in addition to the more popular trigger by northward turnings of the IMF, its azimuthal (both positive and negative) turnings be also regarded as another possible external trigger of substorms. (C) 2001 Published by Elsevier Science Ltd
A NEW EXPERIMENTAL-METHOD (E-PLOT) TO CHARACTERIZE THE SUBSTRATE-CURRENT AND THE SATURATION-VOLTAGE OF FRESH AND HOT-ELECTRON-DAMAGED NMOSFETS
No full textThis work was supported by Goldstar Electron Co. Ltd
Time dependent hot-carrier induced interface state generation in deep submicron LDD nMOSFETs
No full textThe physical mechanism for stress time dependence of hot-carrier induced interface state generation has been investigated by using the lucky-electron model based rate equation and the charge-pumping technique. Both the effective value of critical energy for interface slate generation and the potential barrier for channel hot-electron injection into the gate electrode have been evaluated. The time dependence of interface state generation was formulated with combination of the simple degradation model and the measured barrier heights. It was concluded that the major physical mechanism for self-limiting behavior is the decrement of injected hot-carriers into the oxide due to enhancement of energy-barrier caused by the negative charge build-up at the Si-SiO2 interface
An evolutionary approach to the combination of multiple classifiers to predict a stock price index
No full textMultiple classifier combination is a technique that combines the decisions of different classifiers. Combination can reduce the variance of estimation errors and improve the overall classification accuracy. However, direct application of combination schemes developed for pattern recognition to solving business problems has some limitations, because business problems cannot be explained completely by the results provided by machine-learning-driven classifiers alone owing to their intrinsic complexity. To solve such problems, this paper proposes an approach that is capable of incorporating the subjective problem-solving knowledge of humans into the results of quantitative models. Genetic algorithms (GAs) are used to combine classifiers stemming from machine learning, experts, and users. We use our GA-based method to predict the Korea stock price index (KOSPI). (C) 2005 Elsevier Ltd. All rights reserved.This work was supported by the Research Grant from
Hallym University, Korea
Hybrid genetic algorithms and support vector machines for bankruptcy prediction
No full textBankruptcy prediction is an important and widely studied topic since it can have significant impact on bank lending decisions and profitability. Recently, the support vector machine (SVM) has been applied to the problem of bankruptcy prediction. The SVM-based method has been compared with other methods such as the neural network (NN) and logistic regression, and has shown good results. The genetic algorithm (GA) has been increasingly applied in conjunction with other Al techniques such as NN and Case-based reasoning (CBR). However, few studies have dealt with the integration of GA and SVM, though there is a great potential for useful applications in this area. This study proposes methods for improving SVM performance in two aspects: feature subset selection and parameter optimization. GA is used to optimize both a feature subset and parameters of SVM simultaneously for bankruptcy prediction. (c) 2005 Elsevier Ltd. All rights reserved
SH-SY5y cell phosphoprotein patterns following treatment with sevoflurane monitored by 2D gel electrophoresis.
No full textSH-SY5y cells were incubated with sevoflurane for 2, 5, 15, or 30 min; harvested and lysed. Intracellular enriched phosphoproteins were analyzed by 2D gel electrophoresis. Right panel: Coomassie Brilliant Blue staining; left panel: ProQ Diamond. Y axes represent the apparent molecular mass (kDa), and X axes represent pH values. Acquired images showed reproducibility of experiments. Data shown are representative of three separate experiments.</p
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