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© Springer Nature Switzerland AG 2018. Temporal information has been proved to be an important factor to recommender systems. Both of user behaviors and QoS performance of services are time-sensitive, especially in dynamic cloud environment. Furthermore, due to the data sparsity problem, it is still difficult for existing recommendation methods to get the similarity relationships between services or users well. In view of these challenges, in this paper, we propose a temporal-sparsity aware service recommendation method based on hybrid collaborative filtering (CF) techniques. Specifically, temporal influence is considered into classical neighborhood-based CF model by distinguishing temporal QoS metrics from stable QoS metrics. To deal with the sparsity problem, a time-aware latent factor model based on a tensor decomposition model is applied to mine the temporal similarity between services. Finally, experiments are designed and conducted to validate the effectiveness of our proposal.

Copyright © 2016 John Wiley & Sons, Ltd. Traffic hotline discovery is necessary for rational and scientific urban transportation planning in the new living quarters and economic zones. Cloud of Things (CoT) is a newly emerging concept, involving with two advanced technologies, that is, Cloud Computing and Internet of Things (IoT). CoT provides promising opportunities for traffic hotline discovery. However, it is still a challenge to discover the traffic hotlines over CoT. In view of this challenge, a hotline discovery method over CoT by using big taxi GPS data is proposed in this paper. Specifically, a traffic hotline discovery principle is presented to provide a reference standard for the generalized traffic spots that need planning, and a corresponding hotline discovery method is proposed for traffic hotspot identification and hotline selection. To improve the scalability and efficiency of the proposed method in “Big Data” environment, the SAP HANA cloud is applied to implement the proposed method under two application scenarios. Finally, the experimental results demonstrate that the proposed method is both effective and efficient. Software—Practice and Experience. Copyright © 2016 John Wiley & Sons, Ltd.

With software-defined networking (SDN) becoming the leading technology for large-scale networks, it is definitely expected that SDN will suffer various types of distributed denial-of-service (DDoS) attacks because of its centralized control logic. However, almost all of existing works concentrate on the controller overloading DDoS attacks, while vulnerabilities exposed by data plane of SDN for DDoS attacks are largely ignored. In this paper, we firstly investigate a flow rule flooding DDoS attack. By thoroughly analyzing the flow table size and miss rate, we find that attackers are able to inflict significant performance degradation over the system with limited volume of attack resource. We then prove that it is possible for attackers to maximize the performance degradation and minimize the attack rate at the same time. Besides the flooding DDoS attack, we also study a novel DDoS attack targeting data plane of SDN. By utilizing the entry lifetime management mechanism of flow tables, this attack almost never exhibits an intensive controller access behavior. It flies under the radar by inflicting non-notable performance impact on the system, while it creates heavy long-term financial burden on the target application. Finally, we present a potential countermeasure for this stealthy DDoS attack. Through extensive experiments, we conclude that DDoS attacks targeting data plane are possible. Copyright © 2016 John Wiley & Sons, Ltd.

Glutathione S-transferases (GSTs) from different field populations of Liposcelis bostrychophila (Psocoptera: Liposcelididae) were purified by glutathione-agarose affinity chromatography and characterized subsequently by their Michaelis-Menten kinetics toward the artificial substrates 1-chloro-2,4-dinitrobenzene (CDNB) and reduced glutathione (GSH). The specific activity of the affinity of purified GST toward CDNB was highest in lab population, 2.7-fold higher than that of Guanghan population with the lowest value observed. GSTs of lab population exhibited higher apparent Michaelis-Menten constants (Km) and higher maximal velocity (Vmax) values than those of Jianyang and Guanghan populations, revealing that the latter two populations exhibited significantly higher affinities to the test substrates. Inhibition kinetics showed that all test compounds (ethacrynic acid, curcumin, diethyl maleate, bromosulfalein, and carbosulfan) possessed significant inhibitory effects on GSTs. Curcumin appeared to be the most effective inhibitor. Compared to the other compounds, diethyl maleate and carbosulfan exhibited their I50s (the concentration required to inhibit 50% of GSTs activity) at higher concentrations.

During the past several decades, China has made great progress in grain storage research, which greatly improved and promoted grain storage techniques and facilities. Especially in the 1990s, modern grain storage depots were constructed, in which four new technologies of grain inspection automation, machinery aeration, grain cooling, and phosphine recirculating fumigation were popularized. The main technologies to phase out methyl bromide in national depots are under-film phosphine recirculation fumigation and mixing fumigation of phosphine and carbon dioxide. In grain storage scientific research, research programs from applied to molecular fields have been implemented in institutes and universities. The 4th national survey of stored grain insects showed 270 species including 44 natural enemies were recorded. Among these stored grain insect pests the psocid, Liposcelis bostrychophila is generally more prevalent in stored grain with high moisture content. Hence, bionomics, ecologies, control measures, and molecular biology have being conducted since 1990s, and many achievements have been obtained. Efficacy of new grain protectants such as diatomaceous earth and spinosad against the main stored grain insects were evaluated. Researches on effective concentration of phosphine, application technique, recirculation fumigation, combination phosphine with carbon dioxide, and phosphine resistance mechanism were executed. Other fumigants tested included ethyl formate, carbon disulfide, and sulfuryl fluoride against stored grain insects were evaluated, or reevaluated. The fumigation activities and mechanisms of ethyl formate to the main stored product insects were systemically studied and the results showed ethyl formate controlled Sitophilus oryzae, Tribolium castaneum, Rhyzopertha dominica and Liposcelis bostrychophila effectively in a very short time, and the fumigation efficacy at relatively low temperature was better than that at relatively higher temperature. With the rapid progress of technology and scientific research, the objectives of high quality, high nutrition, high benefit, low waste, low pollution, and low cost in grain storage will be achieved, even during prolonged storage.

The psocid, Liposcelis bostrychophila is a prevalent insect pest in large grain depots in P.R. China. Our previous research proved that ethyl formate killed psocid adults of susceptible strain within 24 h, and the fumigation efficacy at relatively low temperature was better than that at relatively high temperature. In this paper, fumigation activities of ethyl formate on DDVP and PH₃ resistant strains of L. bostrychophila were studied by the sealed jar fumigation method under different ethyl formate concentrations, fumigation times, and temperatures. Results showed that treatment time and concentration significantly affected fumigation effectiveness of ethyl formate against L . bostrychophila adults at 30°C. The 50% lethal concentrations (LC₅₀) of ethyl formate against two resistant strains increased as the temperature increased from 20° to 30°C. At 27±0.5°C and 24 h fumigation, the LC₅₀ were significantly lower for DDVP and PH₃ resistant strains than that of the susceptible strains and the LC₅₀ of DDVP resistant strains were significantly lower than that of PH₃ resistant strains.

Purpose: To improve the production of L-serine from sucrose directly by wild type Corynebacterium glutamicum SYPS-062.Methods: The culture medium for the production of L-serine was optimized using a statistical experimental design. Sucrose, ammonium sulfate ((NH4)2SO4) and biotin were the key factors, based on previous studies. A three-level Box–Behnken factorial design combined with response surface methodology were used to optimize the medium for the production of L-serine. Validation experiments were also carried out to establish the adequacy and accuracy of the model obtained.Results: Under optimal conditions (sucrose 81 g/l, (NH4)2SO4 30 g/l and biotin 27 µg/l), L-serine concentration increased to 14.90 g/l which is about 2.5-fold increase over that of the original medium (6 g/l). L-serine concentration in a 5 L fermenter reached 16.4 g/L.Conclusion: The results show that statistical medium design method is effective in improving L-serine production. The optimization medium is considered fundamental and useful for the development of C.glutamicum SYPS-062 cultivation process for efficient production of L-serine on a large scale.Keywords: L-Serine, Sugar, Medium optimization, Corynebacterium glutamicum Box–Behnken factorial design, Response surface methodology

Big data and cloud computing are two disruptive trends nowadays, provisioning numerous opportunities to the current information technology industry and research communities while posing significant challenges on them as well. Cloud computing provides powerful and economical infrastructural resources for cloud users to handle ever increasing data sets in big data applications. However, processing or sharing privacy-sensitive data sets on cloud probably engenders severe privacy concerns because of multi-tenancy. Data encryption and anonymization are two widely-adopted ways to combat privacy breach. However, encryption is not suitable for data that are processed and shared frequently, and anonymizing big data and manage numerous anonymized data sets are still challenges for traditional anonymization approaches. As such, we propose a scalable and cost-effective framework for privacy preservation over big data on cloud in this paper. The key idea of the framework is that it leverages cloud-based MapReduce to conduct data anonymization and manage anonymous data sets, before releasing data to others. The framework provides a holistic conceptual foundation for privacy preservation over big data. Further, a corresponding proof-of-concept prototype system is implemented. Empirical evaluations demonstrate that scalable and cost-effective framework for privacy preservation can anonymize large-scale data sets and mange anonymous data sets in a highly flexible, scalable, efficient, and cost-effective fashion. Copyright © 2013 John Wiley & Sons, Ltd.

Purpose: To improve the production of a novel exopolysaccharide (EPS) by Bacillus mucilaginosus CGMCC5766.Methods: The culture medium for production of EPS was optimized using statistical experiment design. Sucrose, CaCO3 and K2HPO4 were found to be the key factors based on the results obtained from Plackett–Burman experimental design. The optimal concentration range of the three factors was examined by the steepest ascent path, and then the optimum concentration was further investigated through response surface methodology. Validation experiments were also carried out to establish the adequacy and accuracy of the model obtained.Results: Under optimal conditions (sucrose 61.31 g/l, CaCO3 5.06 g/l and K2HPO4 0.17 g/l), EPS concentration achieved 22.04 g/l, which was about 1.6-fold increase compared with that using the original medium. EPS concentration in 5-l fermenter reached 23.46 ± 0.76 g/l.Conclusion: The optimization medium is considered fundamental and useful for the development of B. mucilaginosus CGMCC5766 cultivation process for efficient production of EPS on a large scale.Keywords: Bacillus mucilaginosus CGMCC5766, Exopolysaccharide, Medium, Optimization, Statistical experiment design

Purpose: To improve the biosynthesis of L-arginine by overexpressing homologous NAD kinase (ppnk) in Corynebacterium crenatum SYPA5-5 and to study its impact in presence of high (HOS) and low oxygen supply (LOS).Methods: A recombinant plasmid (pJC1-tac-ppnK) harboring homologous NAD kinase (ppnk) was constructed in a shuttle vector pJC1 and transferred in L-arginine producing strain Corynebacterium crenatum SYPA5-5. Furthermore, fermentation was performed by shake flask method with consecutive determination of cell growth and glucose concentration. NAD+ kinase activity was studied by stop method and NADP(H) concentrations were determined by spectrophotometric enzymatic cycling method. To check the biosynthesis of amino acids, HPLC method was used to determine extracellular amino acid concentrations.Results: In HOS condition, NAD+ kinase activity increased by 116 %, while intracellular concentrations of NADP+ and NADPH increased by 7.3 and 36.8 %, respectively. Whereas, in LOS condition , NAD+ kinase activity increased 49 % , with intracellular 14.67 and 15 % increases in NADP+ and NADPHrespectively. More importantly, recombinant strain could produce 26.47 and 11.36 g/L L-arginine in HOS and LOS respectively, which is higher than control strain value of 24.29 and 7.58 g/L respectively.Conclusion: These results suggest that altering the concentration of co-enzymes by NAD kinase in Corynebacterium crenatum is an effective way to increase NADP+ with concurrent production of NADPH for further enhanced L-arginine biosynthesis in Corynebacterium crenatum in both conditions of high and low oxygen supply.Keywords: NAD kinase, PpnK, L-arginine, Corynebacterium crenatum

Traditionally, service discovery is often promoted by the centralized approach that typically suffers from single point of failure, poor reliability, poor scalability, to name a few. In view of this challenge, a QoS-aware service discovery method is investigated for elastic cloud computing in an unstructured peer-to-peer network in this paper. Concretely speaking, the method is deployed by two phases, that is, service registering phase and service discovery phase. More specifically, for a peer node engaged in the unstructured peer-to-peer network, it firstly registers its functional and nonfunctional information to its neighbors in a flooding way. With the multiple registered information, the QoS-aware service discovery is promoted in a probabilistic flooding way according to the network traffic. At last, extensive simulations are conducted to evaluate the feasibility of our method. Copyright © 2013 John Wiley & Sons, Ltd.