CF System Research Articles

The impact of Caputo-Fabrizio fractional derivative and the dynamics of noise on worm propagation in wireless IoT networks

The main objective of this article on Wireless sensor network of the Internet of Things (IoT). The wireless network, B bluetooth network, infrared network, and other networks are the key components of the Internet of Things (IoT). The major emphasis of this work was on the impact of Caputo-Fabrizio fractional derivative on worm propagation in heterogeneous susceptible-exposed-infected-recovered wireless IoT devices. We first determined the equilibrium points and fundamental reproduction number for the Caputo-Fabrizio HSEIR system, and then we discussed the stability of the system at the worm propagation equilibrium point. Using the Picard-Lindeof method, we determine the existence and unique solution for the fractional CF system of the heterogeneous SEIR model. Next, we use fixed point theory to judge the stability of the iterative method. We investigate the impact of the derivative order on the behaviour of the resultant functions and acquired numerical values by computing the model's findings for various fractional orders. In addition, we compute the integer-order model's results and contrast them with the results of the fractional-order model. We develop a periodically intermittent controller driven by white noise with the amazing benefits of reduced cost and more adaptable control technique to restrict the spread of worms in wireless IoT networks. To clearly define the conditions for stability in probability one, we employ the stochastic analysis technique. Our results show that the nonlinear worm propagation system may be stabilised by intermittent stochastic perturbation under the parameters of intermittent time linked to stochastic perturbation strength. Our theoretical conclusions may be used to analyse the observable processes of the worm, design countermeasures to prevent its spread, and evaluate the consequences of various system parameters.

Personalized Movie Recommendation System

In the digital world of today, where there is an infinite amount of content to consume, including movies, books, videos, articles, and so on, finding content that appeals to one's tastes has become challenging. On the other hand, providers of digital content want to keep as many people using their service for as long as possible. This is where the recommender system comes into play, where content providers suggest content to users based on their preferences. Web applications that offer a variety of services and automatically suggest some services based on user interest increasingly rely on recommendation systems. Different business services each play a significant role in the success of the current marketing field. The personalize recommendation technique is one of the most valuable tools for providing personalized service on websites. When it comes to e-Commerce's online marketing efforts, this strategy is extremely useful. To build the proposal framework, the cooperative sifting is exceptionally helpful advances in the field of recommender frameworks. The accuracy of recommendation engines is the source of many issues in today's web. Therefore, a variety of strategies are utilized to enhance the recommendation system's diversity and accuracy. When generating recommendations, the fundamental recommender systems typically take one of the following into account: The Content-Based Filtering, which is based on the user's preferences, it describes things, and we use keywords other than the user's profile to show what the user likes and dislikes. To put it another way, CBF algorithms suggest products that people have liked in the past or products that are similar to them. It looks at what you've liked in the past and suggests the best match, Or a collaborative filtering system makes recommendations for items based on how similar users and/or items are measured. The CF system only suggests products that are popular with similar types of users. The development of a movie recommendation system with category-based recommendations, more precise results, increased efficiency, and overcoming the cold start are the goals of this system.

A Review on Cell-Free Massive MIMO Systems

Cell-free massive multiple-input multiple-output (CF mMIMO) can be considered as a potential physical layer technology for future wireless networks since it can benefit from all the advantages of distributed antenna systems (DASs) and network MIMOs, such as macro-diversity gain, high channel capacity, and link reliability. CF mMIMO systems offer remarkable spatial degrees of freedom and array gains to mitigate the inherent inter-cell interference (ICI) of cellular networks. In such networks, several distributed access points (APs) together with precoding/detection processing can serve many users while sharing the same time-frequency resources. Each AP can be equipped with single or multiple antennas, and hence, can provide a consistently adequate service to all users regardless of their locations in the network. This paper presents a detailed overview of the current state-of-the-art on CF systems. First, it performs a literature review of the conventional CF and scalable user-centric (UC) CF mMIMO systems in terms of the limited capacity of the fronthaul links and the connection between APs and user equipments (UEs). As beyond networks will rely on higher frequency bands, it is of paramount importance to discuss the impact of beamforming techniques that are being investigated. Finally, some of the CF promising enabling technologies are presented to emphasize the main applications in these networks.

Secure Optimal Precoding for User-Centric Cell-Free Massive MIMO System

The security of user-centric cell-free massive multiple-input multiple-output (UC-CF mMIMO) system in the presence of multiple collusive eavesdroppers (Eves) is investigated in this letter. The access points (APs) share the estimated channel state informations (CSIs) of serving users to central processing unit (CPU). Utilizing the received partial CSIs, the CPU optimizes precoding via formulating a secrecy rate maximization problem under minimum rate requirements of users and power constraints of APs. The formulated problem is non-convex, and the optimum solution is acquired by iteratively solving a sequence of second-order cone programming problems. The numerical simulations present the comparison of secrecy performance achieved in different AP selection methods of UC-CF system, and CF system.

Can Dynamic TDD Enabled Half-Duplex Cell-Free Massive MIMO Outperform Full-Duplex Cellular Massive MIMO?

We consider a dynamic time division duplex (DTDD) enabled cell-free massive multiple-input multiple-output (CF-mMIMO) system, where each half-duplex (HD) access point (AP) is scheduled to operate in the uplink (UL) or downlink (DL) mode based on the data demands of the user equipments (UEs), with the goal of maximizing the sum UL-DL spectral efficiency (SE). We develop a new, low complexity, greedy algorithm for the combinatorial AP scheduling problem, with an optimality guarantee theoretically established via showing that a lower bound of the sum UL-DL SE is sub-modular. We also consider pilot sequence reuse among the UEs to limit the channel estimation overhead. In CF systems, all the APs estimate the channel from every UE, making pilot allocation problem different from the cellular case. We develop a novel algorithm that iteratively minimizes the maximum pilot contamination across the UEs. We compare the performance of our solutions, both theoretically and via simulations, against a full duplex (FD) multi-cell mMIMO system. Our results show that, due to the joint processing of the signals at the central processing unit, CF-mMIMO with dynamic HD AP-scheduling significantly outperforms cellular FD-mMIMO in terms of the sum SE and 90% likely SE. Thus, DTDD enabled HD CF-mMIMO is a promising alternative to cellular FD-mMIMO, without the cost of hardware for self-interference suppression.

Pollinator diversity and foraging behavior of Apis mellifera Linnaeus and Apis cerana Fabricius on Chinese cabbage (Brassica rapa Linnaeus subspecies chinensis) grown under different farming systems

The present study was on pollinator diversity and foraging behavior of Apis mellifera Linnaeus and Apis cerana Fabricius on Chinese cabbage (Brassica rapa Linnaeus subspecies chinensis) grown under different farming systems. A total of 19 insects belonging to 16 genera under 7 families and 3 orders were recorded on Chinese cabbage. Among all insect visitors, A. mellifera (8.85 / 100 flowers) was the most dominant visitor. Significantly higher abundance was recorded in SPNF system followed by the control and CF system, respectively. The insect pollinators showed a positive correlation with temperature and a negative correlation with humidity. The average number of flowers visited by both foragers in one minute was significantly more in SPNF system followed by the control and CF system. The average time spent per flower by both foragers was significantly more in the CF system followed by the control and SPNF system. The number of loose pollen grains sticking to the body of insect pollinators recorded in SPNF system and CF system was statistically the same. Hence, it can be concluded that pollinators prefer SPNF system as compared to CF system and control. So, due to enhanced pollination in SPNF system, farmers may obtain more yields if they are consistent with the timely application of indigenous farm products.

Alternate wetting and drying combined farmyard manure for reducing greenhouse gas while improving rice yield

Water and organic amendments are the most important factors controlling methane (CH ) emissions from paddy fields. Alternate wetting and drying (AWD) in rice cultivation improve water productivity (WP), minimize methane emission, but might increase nitrous oxide emissions (N O). The effects of combined water management and organic manure application on methane and nitrous oxide emission, rice yield are not well documented. The objective of this experiment was to determine rice cultivation technology that can improve productivity and reduce GHG emissions on rice field. The Inpari 32 rice cultivar was used in this study. Closed chamber methods were used for measuring emissions of greenhouse gases. Our results showed that, in comparison with continuous flooding, the AWD significantly reduced total global warming potential (GWP) by 13–17%. The AWD technique increased grain yields by 6-7% compared with those of CF. The AWD technique reduced CH (14–18%) and increased water productivity by 7–12% compared to CF system, along an 18–23% reduction in GHG intensity (GHGI). In conclusion, AWD technique and soil amendment with farmyard manure could be effectively used in greenhouse gas mitigation strategies for reducing GHG emission, GWP, and GHGI without sacrificing rice yield.

Comparison Study on Improved Movie Recommender Systems

Recommendation system is a crucial part of offering items especially in services that offer streaming. For streaming movie services on OTT, RS are a helping hand for users in finding new movies for leisure. In this paper, we propose a machine learning an approach based on auto encoders to produce a CF system which outputs movie rating for a user based on a huge DB of ratings from other users. Utilising Movie Lens dataset, we explore the use of deep learning neural network based Stacked Auto encoders to predict user s ratings on new movies, thereby enabling movie recommendations. We consequently implement Singular Value Decomposition (SVD) to recommend movies to users. The experimental result showcase that our R S out performs a user-based neighbourhood baseline in terms of MSE on predicted ratings and in a survey in which user judge between recommendation s from both systems.

Tumor-derived biomimetic nanozyme with immune evasion ability for synergistically enhanced low dose radiotherapy

High doses of radiation can cause serious side effects and efficient radiosensitizers are urgently needed. To overcome this problem, we developed a biomimetic nanozyme system (CF) by coating pyrite (FeS2) into tumor-derived exosomes for enhanced low-dose radiotherapy (RT). CF system give FeS2 with immune escape and homologous targeting abilities. After administration, CF with both glutathione oxidase (GSH-OXD) and peroxidase (POD) activities can significantly lower the content of GSH in tumor tissues and catalyze intracellular hydrogen peroxide (H2O2) to produce a large amount of ·OH for intracellular redox homeostasis disruption and mitochondria destruction, thus reducing RT resistance. Experiments in vivo and in vitro showed that combining CF with RT (2 Gy) can provide a substantial suppression of tumor proliferation. This is the first attempt to use exosomes bionic FeS2 nanozyme for realizing low-dose RT, which broaden the prospects of nanozymes.Graphical

Intensified production of zeolite A: Life cycle assessment of a continuous flow pilot plant and comparison with a conventional batch plant

AbstractThis study investigates on the environmental impact of an intensified technology for the manufacturing of Zeolite A, one of the largest zeolites employed worldwide by volume and value. The technology under consideration is an oscillatory continuous‐flow synthesis, developed industrially by Arkema, and currently at pilot‐scale. Life cycle assessment (LCA) is used in this work to measure the sustainability of this emerging technology in an anticipatory fashion, before its full deployment, with the aim of driving the process development toward the minimization of the environmental footprint. The assessment explores the full life‐cycle of the production system and comprises comparative analysis, scenario analysis, and a hotspot analysis. Finally, the continuous‐flow technology is benchmarked against the environmental impact of a conventional batch production of zeolite A, based on a full‐scale commercial plant. The results evidence that significant benefits would stem from shifting from batch to continuous‐flow production. The comparative analysis reveals that the extent of the latter advantages depends on the impact category under consideration and directs the next steps of CF system's process development toward pivotal aspects such as the recirculation system to further reduce the system's environmental impacts. Regardless of the chosen production technology, a large share of the total environmental impact hinges on the production of NaOH, a building block of the synthesis, and hence is hardly mitigatable. On the whole, the findings of this work emphasize the need of prioritizing LCA during the development phase of emerging technologies and underline its efficacy to prevent waste of resources and capitals.

Infrared analysis of ultrasound treated milk systems with different levels of caseins, whey proteins and fat

Low-frequency ultrasound (20 kHz) was applied to model casein (CF) and whey protein (WF) milk systems with varying fat contents of 2%, 4%, and 6% (w/w) under different energy densities from 9.54 to 190.8 J mL−1. The study used Fourier transform mid-infrared spectrometry (FT-MIR) to analyse the modification of milk proteins and fat. The results showed that the fat content and sonication time influenced the intensities of fatty chains and ester groups which are assigned to triacylglycerols and lipid-protein complexes for both CF and WF systems. Acoustic cavitation induced structural changes of proteins due to denaturation/aggregation and disruption of milk fat globules/fat clusters led to new protein–protein and protein-lipid interactions.

Attribute-Aware Recommender System Based on Collaborative Filtering: Survey and Classification.

Attribute-aware CF models aim at rating prediction given not only the historical rating given by users to items but also the information associated with users (e.g., age), items (e.g., price), and ratings (e.g., rating time). This paper surveys work in the past decade to develop attribute-aware CF systems and finds that they can be classified into four different categories mathematically. We provide readers not only with a high-level mathematical interpretation of the existing work in this area but also with mathematical insight into each category of models. Finally, we provide in-depth experiment results comparing the effectiveness of the major models in each category.

Influence of Rehabilitation on Oxygen Uptake Kinetics during High Intensity Exercise in Patients with Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive and life-limiting condition of unknown cause with no curative treatment. The impact of IPF on a patient’s quality of life is devastating and palliative treatment such as pulmonary rehabilitation programmes are used to improve quality of life among these individuals, yet relatively little attention has been made to access the effectiveness of rehabilitation programs aimed designed for these patients. There are large gaps in our knowledge on the cardiorespiratory response to exercise and rehabilitation among IPF patients and this study aims to fill this gap in a physiological prospective. We quantified the effects of an eight-week pulmonary rehabilitation program for IPF patients, conducted at Morriston Hospital, Swansea. Fifteen individuals (13 with Idiopathic Pulmonary Fibrosis and two with Pulmonary Fibrosis associated with Rheumatoid Disease) underwent physical and physiological assessments during a three-day testing protocol: 1) On Day 1, physical function (six-minute walk test) and ventilatory function (spirometry) were measured; 2) On Day 2, patients’ cardio-respiratory responses to slowly-increasing, wide-ranging metabolic challenge (using a protocol consisting of periods of rest, incremental bicycle exercise to maximal effort, and post-exercise recovery) were assessed via respiratory gas analysis and ECG recording; 3) On Day 3, patients’ cardio-respiratory responses to rapid-onset, high-workload metabolic challenge were assessed (using a protocol including a rapid-onset, constant workload bicycle exercise) by modelling dynamic respiratory oxygen and heart rate responses. Respiratory gas analysis was used to measure the rate of oxygen uptake ( VO2 ) and oxygen uptake efficiency (OUES). All assessments were performed before and after participants completed the pulmonary rehabilitation programme. A Holter ECG recorder (Pathfinder/Lifecard Digital CF system; Spacelabs Medical Ltd., UK) provided continuous ECG data throughout each exercise test, from which heart rate was derived. Following the rehabilitation programme, heart rate was elevated by 11% - 18% during exercise and recovery states. Post-rehabilitation VO2 was significantly increased (p = 0.01 - 0.03) during the first two minutes of heavy-intensity exercise, whilst HR was reduced (p = 0.04) during this period. OUES and standard measures of respiratory performance (minute ventilation, peak VO2) were unchanged following rehabilitation, whilst peak HR and work rates were significantly reduced during incremental exercise only (p -3). Pulmonary rehabilitation improved the rate of oxygen uptake during heavy-intensity exercise, despite substantially lower heart rates. This suggests that the rehabilitation programme increased systemic arterial-tissue oxygen exchange and/or influenced cardiovascular function to improve systemic oxygen delivery. We might therefore expect that individuals with IPF would find it easier to perform the activities of daily life, including those requiring substantial metabolic demands, following rehabilitation.

Comparative study of nanofiltration membrane characterization devices of different dimension and configuration (cross flow and dead end)

Comparison of nanofiltration characterization data from literature is challenging due to different hydrodynamics and system designs, which affect membrane retention. In this study, stirred cell (SC), micro and macro cross flow systems (micro and macro CF) with different configuration were used to measure salt and organic tracer retention. Minimal concentration polarization conditions were applied in order to:1)evaluate comparability of the systems for characterization of membrane pore radius and molecular-weight-cut-off,2)understand the impact of system configuration and operation on mass transfer,3)compare salt retention at laboratory scale with the retention of spiral wound module.Results indicated that system dimension was the most important parameter to affect the mass transfer and the concentration of both salt and organic tracers on the membrane surface (Cm) in the macro CF system. Indeed, the higher channel length to width ratio of macro CF was related to reduced mass transfer and higher Cm. However, a comparability of the three systems was observed by operating at low flux (below 80 L/m2h) and higher cross flow velocity (above 0.4 m/s), where the lowest concentration polarization conditions were maintained. This is valid taking into account the variation of hydrodynamics (e.g. relation of Sherwood number and Reynolds range), which is intrinsically related to the different operation modes of dead end and cross flow. This study gives a novel contribution to improve the accuracy of membrane characterization methodologies and to identify suitable operative conditions for testing new membrane materials at small scale.

Rapid and efficient production of cecropin A antibacterial peptide in Escherichia coli by fusion with a self-aggregating protein

BackgroundCecropin A (CeA), a natural cationic antimicrobial peptide, exerts potent antimicrobial activity against a broad spectrum of Gram-positive and Gram-negative bacteria, making it an attractive candidate substitute for antimicrobials. However, the low production rate and cumbersome, expensive processes required for both its recombinant and chemical synthesis have seriously hindered the exploitation and application of CeA. Here, we utilized a short β-structured self-aggregating protein, ELK16, as a fusion partner of CeA, which allowed the efficient production of high-purity CeA antibacterial peptide with a simple inexpensive process.ResultsIn this study, three different approaches to the production of CeA peptide were investigated: an affinity tag (His-tag)-fused protein expression system (AT-HIS system), a cell-free protein expression system (CF system), and a self-assembling peptide (ELK16)-fused protein expression system (SA-ELK16 system). In the AT-HIS and CF systems, the CeA peptide was obtained with purities of 92.1% and 90.4%, respectively, using one or more affinity-chromatographic purification steps. The procedures were tedious and costly, with CeA yields of only 0.41 and 0.93 μg/mg wet cell weight, respectively. Surprisingly, in the SA-ELK16 system, about 6.2 μg/mg wet cell weight of high-purity (approximately 99.8%) CeA peptide was obtained with a simple low-cost process including steps such as centrifugation and acetic acid treatment. An antimicrobial test showed that the high-purity CeA produced in this study had the same antimicrobial activity as synthetic CeA peptide.ConclusionsIn this study, we designed a suitable expression system (SA-ELK16 system) for the production of the antibacterial peptide CeA and compared it with two other protein expression systems. A high yield of high-purity CeA peptide was obtained with the SA-ELK16 system, which greatly reduced the cost and time required for downstream processing. This system may provide a platform for the laboratory scale production of the CeA antibacterial peptide.

Optimizing Soil Moisture and Nitrogen Use Efficiency of Some Maize (Zea mays) Varieties under Conservation Farming System

In Zambia, small holder farmers depend on producing maize (Zea mays), which is a major staple food for many Zambians. Maize productivity among the smallholder farmers is quite low, giving only 2.3 tons per hectare. The low yields are attributed to insufficient and erratic rain fall, low soil fertility, and poor farming practices. Therefore, the objective of this study was to evaluate the performance of maize genotypes for nitrogen use efficiency and soil moisture utilisation under conservation farming system. The trials were carried out at two sites with different soil types. Three maize varieties i.e. ZMS 606, GV 640 and GV 635 were evaluated in maize – cowpea rotation. Four cowpea varieties used for rotation with maize, i.e. Bubebe Lutembwe, BB 14-16-2-2 and LT 11-3-3-12. BB 14-16-2-2 and LT 11-3-3-12 are mutation-derived lines of Bubebe and Lutembwe cowpea parent varieties respectively. The experimental design used was split plot with three replications. The NUE was significantly (P< 0.05) higher in CF and accounted for 27 % and 15% more than conventional farming system which valued 17% and 3% at Chisamba and Batoka, respectively. while soil moisture content was higher at Batoka than Chisamba in CF system. ZMS 606 and GV 640 varieties were superior over GV 635 for NUE. Cowpea variety BB 14-16-2-2 significantly increased NUE of maize varieties. Therefore, smallholder farmers in Zambia can increase maize productivity in maize - cowpea rotation system due to the increased NUE. Recommendations are made for farmers to select improved nitrogen efficient maize varieties to optimize productivity of maize in conservation farming system.

A novel bio-electro-Fenton process with FeVO4/CF cathode on advanced treatment of coal gasification wastewater

Abstract An investigation was carried out aimed at checking the feasibility of the novel bio-electro-Fenton process with FeVO4/CF cathode on advanced treatment of coal gasification wastewater. The maximum power density arrived 849.7 mW/m3 in MFC-FeVO4/CF system, which was corresponding to a current density of 2.6 A/m3 at the voltage of 326.8 mV. The concentration of BOD5, COD, TOC and total phenols in the cathode effluent under short-circuit conditions were 4.5 mg/L, 32.5 mg/L, 8.8 mg/L and 15.6 mg/L, respectively, which all met the class-I criteria of the Integrated Wastewater Discharge Standard. FeVO4/CF could be employed as a two-way Fenton-like catalyst that leads to the production of more reactive oxygen species. The in situ generation of Fenton-like reagents (Fe(II, V(IV) and H2O2) at the cathode was demonstrated by the cyclic voltammetry measurement. This novel process provides a cost-effective alternative to extend the practical merits of traditional MFCs and Fenton towards advanced treatment of industrial wastewater.

Synergetic Solvent Engineering of Film Nanomorphology to Enhance Planar Perylene Diimide-Based Organic Photovoltaics.

Solvent additive has proven as a useful protocol for improving the film nanomorphology of polymer donor (D): fullerene acceptor (A) blends in bulk heterojunction (BHJ) photovoltaic cells. By contrast, the effect of such solvent additive on nonfullerene BHJ cells based on perylene diimide acceptor, for instance, is less effective because of their highly planar structure and strong π-aggregation in solid state. Here we choose N,N'-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (PDI) and thieno[3,4-b]thiophene-alt-benzodithiophene (PTB7) as a model D:A blend system to investigate how solvent engineering strategy synergistically impacts the blend film nanomorphology. Based on the differences of solvent volatility and solubility, various host solvents-chloroform (CF) and chlorobenzene (CB) and solvent additives-chloronaphthalene (CN) and 1,8-diiodooctane (DIO) are selected for comparative studies. It is found that the π-aggregation of PDIs can be largely suppressed by using low-boiling point (Tb) CF solvent, yet enlarged by using high-Tb CB. Moreover, CN additive provides good solubility of PDI molecules and hence reduces large PDI aggregates in CB system, while DIO exhibiting poor solubility works oppositely. By contrast, DIO that presents larger Tb difference with CF prolongs the film-forming, which assists in optimizing the PDI aggregation and increases the intermixed PTB7:PDI phases more significantly than CN in CF system, yielding the finest phase-separation morphology and balanced charge mobility. Consequently, the inverted BHJ cells based on CF-processed PTB7:PDI blend film with 0.4 vol % DIO exhibit the highest PCE of 3.55% with a fill factor of 56%, both of which are among the best performance for such a paradigm PTB7:PDI blend-based BHJ cells.

A participative network of organic and conventional crop farms in the Seine Basin (France) for evaluating nitrate leaching and yield performance

In the Seine Basin, characterized by intensive arable crops, most surface and groundwater is contaminated by nitrate (NO3−). A collaborative study was set up, involving a network of volunteer farmers, to investigate NO3− leaching with ceramic cups (90cm deep) on whole crop rotations of organic (OF) and conventional (CF) commercial farms in the Seine Basin. A total of eight CF and six OF systems were studied (63 fields) in five different soil and climate conditions, taking into account a wide diversity of practices (including low or no exogenous N inputs, systematic catch-crop implementation, and no tillage) and use of different exogenous organic matter (EOM) such as biogas residue; slurry; poultry manure; and cow and horse manure.Over the 2years, OF cropping systems (including alfalfa) led to a lower average sub-root concentration (37±9mgNO3−l−1) than CF systems (48±19mg NO3−l−1, ±standard deviation between farms). The water inflows calculated ranged from 86 to 190mm depending on the year for the 4-month drainage period. The amounts of N leached were on average 23% lower in OF (12.5±2.9kgNha−1yr−1) than in CF systems (16.2±6.3kgNha−1yr−1). Concerning farming practices, the main impacting factors were the use of EOM in fall, the lack of catch crops before spring, and the proportion of legumes in the rotation. Overall, this wide collaborative network highlights good and innovative practices by CF and OF farmers attempting to decrease NO3− in groundwater.

A dynamic collaborative filtering system via a weighted clustering approach

A collaborative filtering system (CF) aims at filtering huge amount of information, in order to guide users of web applications towards items that might interest them. Such a system, consists in recommending a set of personalized items for an active user, according to the preferences of other similar users. Existing methods, such as memory and Matrix Factorization (MF) approaches can achieve very good recommendation accuracy, unfortunately they are computationally very expensive. Applying such approaches to real-world applications in which users, items and ratings are frequently updated remains therefore a challenge. To address this problem, we propose a novel efficient incremental CF system, based on a weighted clustering approach. Our system is designed to provide a high quality of recommendations with a very low computation cost. In contrast to existing incremental methods, the complexity of our approach does not depend on the number of users and items. Our CF system is therefore suitable for dynamic settings, involving huge databases, in which available information evolves rapidly (i.e, submission of new ratings, update of existing ratings, appearance of new users and new items). Numerical experiments, conducted on several real-world datasets, confirm the efficiency and the effectiveness of our method, by demonstrating that it is significantly better than existing incremental CF methods in terms of both scalability and recommendation quality.