• Cleaning of contaminated MFM probes using a BOPP film and external magnetic field

      Zhang, Chao; Liu, Jinyun; Meng, Qing-Ling; Zhang, Wenxiao; Wang, Ying; Li, Dayou; Wang, Zuobin; Changchun University of Science and Technology; University of Bedfordshire (Elsevier, 2017-02-22)
      When magnetic samples are tested with a magnetic force microscope (MFM), the probe tip can inevitably be contaminated and magnetic particles are often adhered to the tip surface. The probe with magnetic contamination will seriously affect the quality of morphological and magnetic imaging. In the work, a method for the cleaning of contaminated magnetic probe tips was developed by the use of a biaxially-oriented polypropylene (BOPP) film together with an external magnet field in an MFM system. In the experiments, an MFM system was used for manipulating the tip to push into the BOPP film with a depth of 50-100nm under a magnetic field and hold for 5s, and the relationships between loading forces and separating forces were studied. The scanning electron microscope (SEM) images have shown that the use of the BOPP film together with an external magnet field is effective for the cleaning of contaminated MFM probes. This method can greatly improve the quality of magnetic imaging, prolong the service life of magnetic probes and reduce the experimental costs in many MFM applications.
    • Co-presence in the real and the virtual space: interactions through orientation

      Christopoulos, Athanasios; Conrad, Marc; Shukla, Mitul; University of Bedfordshire (Springer Verlag, 2017-08-03)
      The global aim of this research is to identify, map, and form a taxonomy of the ways, the elements, and the factors that affect learner engagement with virtual worlds when Hybrid Virtual Learning models are used. Thereafter, the more specific objective of the research is to provide clear guidance to educators who are already utilising or are planning to embed this learning model in their educational agenda. For the examination of this topic, a quanti-qualitative research approach is used, as this allows to investigate the subject both from the students’ and the instructional designer’s point of view. The sample of this study consists of both undergraduate and postgraduate university students. Participants are requested to fill in two different questionnaires, one before using the virtual world and one after completing their assignment. That way it is possible not only to fully mirror their thoughts, preconceptions, and opinions towards the use of virtual worlds in Higher Education, but also the impact that the instructional designer’s choices have on enhancing the opportunities for interactions. In addition, a focus group is being observed – both in the physical classroom and in the virtual world – during the course of the assignment. The focus of this experiment was on the impact that the orientation/induction process has on learner engagement. The findings suggest that students’ interactions with the content of the virtual world, and the in-class student-to-student interactions, have stronger impact on student engagement. This is because students’ simultaneous co-exis-tence in both environments eliminated the drawbacks of each educational approach, and broadened the network of interactions.
    • Cognitive radio aided internet of vehicles (IoVs) for improved spectrum resource allocation

      Yu H; Eze, Joy C.; Zhang, Sijing; Liu, Enjie; Eze, Elias Chinedum; University of Bedfordshire (Institute of Electrical and Electronics Engineers Inc., 2015-12-28)
      The highly anticipated era of Internet of Things (IoTs) expected to empower all aspects of Intelligent Transportation Systems (ITS) will undeniably improve transport safety and significantly reduce road accidents. To promote the communication of mobile vehicles (or IoVs), US FCC officially allocated a merger 75 MHz spectrum in the 5.9 GHz band to enable vehicular communication. In this paper, we studied the application of CR technology to IoVs in order to increase the spectrum resource opportunities especially when the officially allocated 75 MHz spectrum in 5.9 GHz band is not enough due to high demands as a result of increasing number of connected devices as already foreseen in the near era of IoTs. We proposed a novel CRAVNET framework which empowers CR assisted vehicles to make opportunistic usage of licensed spectrum bands on the highways, and developed a novel co-operative three-state spectrum sensing and allocation solution which makes CR vehicular SUs aware of additional spectrum resources opportunities on their current and future positions. Both the simulation and theoretical analysis have demonstrated that our solution can significantly improve the performance of a cooperative spectrum sensing and sharing schemes, and provide vehicles with additional spectrum opportunities with zero interference with the PUs activities.
    • Cognitive radio aided Vehicular ad-hoc networks with efficient spectrum allocation and QoS guarantee

      Eze, Joy C.; Zhang, Sijing; Liu, Enjie; Theresa, Efor E.; Eze, Elias Chinedum; University of Bedfordshire; Ebonyi State University (Institute of Electrical and Electronics Engineers Inc., 2016-10-24)
      The increasing demand of diverse vehicular network oriented applications (both safety and non-safety related services would undoubtedly lead to shortage of spectral resource challenge for V2V communication networks. In order to resolve this issue, a novel Adaptive CR Enabled Vehicular NETwork (ACREVNET) framework is proposed in this paper. To avoid heavy overhead usually incurred during spectrum sensing, we developed a novel CR adaptive spectrum sensing (CRASS) scheme that can reduce the spectrum sensing cost and improve sensing performance effectively. We also applied the concept of Nash Bargaining Solution (NBS) to guarantee fairness in spectral resources allocation and proposed a generalized non-symmetric NBS (GNNBS) to perform a non-symmetric cognitive inter-cell spectrum allocation in the proposed ACREVNET framework. Simulation results clearly show that the proposed schemes can acquire additional spectral resource for vehicular communication by applying CR technology, and reduce the message transmission delay and blocking probability significantly.
    • Cognitive radio technology assisted vehicular ad-hoc networks (VANETs): current status, challenges, and research trends

      Eze, Joy C.; Zhang, Sijing; Liu, Enjie; Eze, Elias Chinedum; University of Bedfordshire (Institute of Electrical and Electronics Engineers Inc., 2017-10-26)
      VANET and cognitive radio network (CRN) are both new emerging technologies in wireless networking. The application of CR concept in wireless communication systems for intelligent vehicles has been envisioned as a promising idea towards solving the problem of scarce spectrum. This paper discusses CR technologies for VANETs aimed at opportunistic spectrum access (OSA) for improved vehicular communication efficiency. This survey explored novel approaches and current research challenges associated with the use of CR technologies in VANETs. Our study is different from previous works in that it presents recent advances, open issues, and future research directions on how to effectively design and deploy CR enabled vehicular networks emphasizing on architecture, CR-VANETs and WAVE Standards, MAC schemes for CR-VANETs, spectrum sensing, minimized interference impact through coordination between PUs and SUs, spectrum management, efficient message routing, security and privacy, as well as CR enabled vehicular networks test-beds and simulation platforms. Furthermore, the paper also identified several challenges facing the design and development of CR-VANTs and the required approaches to tackle them.
    • Cognitive radio-enabled Internet of Vehicles: a cooperative spectrum sensing and allocation for vehicular communication

      Eze, Joy C.; Zhang, Sijing; Liu, Enjie; Eze, Elias Chinedum; University of Bedfordshire; Ebonyi State University (IET, 2018-02-07)
      Internet of Things (IoTs) era is expected to empower all aspects of Intelligent Transportation System (ITS) to improve transport safety and reduce road accidents. US Federal Communication Commission (FCC) officially allocated 75MHz spectrum in the 5.9GHz band to support vehicular communication which many studies have found insufficient. In this paper, we studied the application of Cognitive Radio (CR) technology to IoVs in order to increase the spectrum resource opportunities available for vehicular communication, especially when the officially allocated 75MHz spectrum in 5.9GHz band is not enough due to high demands as a result of increasing number of connected vehicles as already foreseen in the near era of IoTs. We proposed a novel CR Assisted Vehicular NETwork (CRAVNET) framework which empowers CR enabled vehicles to make opportunistic usage of licensed spectrum bands on the highways. We also developed a novel co-operative three-state spectrum sensing and allocation model which makes CR vehicular secondary units (SUs) aware of additional spectrum resources opportunities on their current and future positions and applies optimal sensing node allocation algorithm to guarantee timely acquisition of the available channels within a limited sensing time. The results of the theoretical analyses and simulation experiments have demonstrated that the proposed model can significantly improve the performance of a cooperative spectrum sensing and provide vehicles with additional spectrum opportunities without harmful interference against the Primary Users (PUs) activities.
    • Comparative analysis of long-haul system based on SSB modulation utilising dual parallel Mach–Zehnder modulators

      Paloi, Fadil; Haxha, Shyqyri; University of Bedfordshire; Royal Holloway, University of London (Springer New York LLC, 2018-02-08)
      In this paper, we have proposed a long-haul optical transmission system, based on a single sideband (SSB) modulation scheme. Analytical and simulation models have been developed, optimised and demonstrated for the proposed SSB system configurations. The SSB modulation scheme was proposed to overcome dispersion in the fibre. We have shown that the related link losses can be minimized by increasing the quality of the optical signal at the modulation. We have optimised the radio over fibre configuration scheme based on dual parallel dual drive Mach–Zehnder Modulator, thereby increasing transmission length of the fibre. With the proposed SSB, by suppressing some of the harmonics and cancelling one of the sidebands, we have halved the RF power fading and interference. The developed analytical (theoretical/mathematical) model agrees very well with the simulation results using two (both) different commercial simulation tools. The optical signal is boosted while minimizing the number of repeaters. We report a SSB configuration, compensation and amplification with individual spans of 150 km, by extending the length of the link up to 3250 km. The proposed system configuration exhibits high performance with less complexity and lower cost.
    • Comparative analysis of scheduling algorithms for radio resource allocation in future communication networks

      Ashfaq, Khuram; Safdar, Ghazanfar Ali; Ur-Rehman, Masood; ; University of Bedfordshire; University of Glasgow (PeerJ, 2021-05-18)
      Wireless links are fast becoming the key communication mode. However, as compared to the wired link, their characteristics make the traffic prone to time- and location-dependent signal attenuation, noise, fading, and interference that result in time varying channel capacities and link error rate. Scheduling algorithms play an important role in wireless links to guarantee quality of service (QoS) parameters such as throughput, delay, jitter, fairness and packet loss rate. The scheduler has vital importance in current as well as future cellular communications since it assigns resource block (RB) to different users for transmission. Scheduling algorithm makes a decision based on the information of link state, number of sessions, reserved rates and status of the session queues. The information required by a scheduler implemented in the base station can easily be collected from the downlink transmission. This paper reflects on the importance of schedulers for future wireless communications taking LTE-A networks as a case study. It compares the performance of four well-known scheduling algorithms including round robin (RR), best channel quality indicator (BCQI), proportional fair (PF), and fractional frequency reuse (FFR). The performance of these four algorithms is evaluated in terms of throughput, fairness index, spectral efficiency and overall effectiveness. System level simulations have been performed using a MATLAB based LTE-A Vienna downlink simulator. The results show that the FFR scheduler is the best performer among the four tested algorithms. It also exhibits flexibility and adaptability for radio resource assignment.
    • Comparative study of one-dimensional photonic crystal heterostructure doped with a high and low-transition temperature superconducting for a low-temperature sensor

      Soltani, A.; Ouerghi, F.; AbdelMalek, Fathi; Haxha, Shyqyri; University of Tunis-El Manar; University of Bedfordshire (Elsevier, 2019-04-20)
      In this work, we present a theoretical study dealing with the sensitivity to physical parameters such as defect nature and thickness, and temperature. Indeed, the sensitivity considerably enhanced via the use of one-dimensional photonic crystal heterostructure (1D-PCH) which is composed of a few layers of ordinary materials, and superconducting defects. The aim of this paper is to compare the sensitivity of two proposed models consisting of (a) 1D-PCH doped with a high-transition temperature superconductor (Yttrium barium copper oxide (YBCO)), and (b) 1D-PCH doped with a low-transition temperature superconductor (niobium nitrure (NbN)). By using the transfer-matrix method (TMM), it has been demonstrated that model (b) is very sensitive compared to model (a). Therefore, the superconducting defect nature on 1D-PCH, using a few layers can play a fundamental role in a very low-temperature sensor.
    • Comparing contextual and non-contextual features in ANNs for movie rating prediction

      Mustafa, Ghulam; Frommholz, Ingo; University of Bedfordshire (CEUR-WS, 2016-12-31)
      Contextual recommendation goes beyond traditional models by incorporating additional information. Context aware recommender systems (CARs) correspond to not only the user's preference profile but also consider the given situation and context. However, the selection and incorporation of optimal contextual features in context aware recommender systems is always challenging. In this paper we evaluate different representations (feature sets) from the given dataset (LDOS-CoMoDa) for contextual recommendations, in particular looking into movie rating prediction as a subproblem of recommendation. We further crosscompare these representations to select useful and relevant features and their combination. We also compare the performance of standard matrix factorization to Artificial Neural Networks (ANNs) in CARs. Our evaluation shows that dynamic, contextual features are dominant compared to non-contextual ones for the given task in the given data set.We also show that ANNs slightly outperform matrix factorization approaches typically used in CARs.
    • A comparison of reinforcement learning algorithms in fairness-oriented OFDMA schedulers

      Comșa, Ioan-Sorin; Zhang, Sijing; Aydin, Mehmet Emin; Kuonen, Pierre; Trestian, Ramona; Ghinea, Gheorghiţă; Brunel University; University of Bedfordshire; University of the West of England; HEIA-FR, Switzerland; et al. (MDPI, 2019-10-14)
      Due to large-scale control problems in 5G access networks, the complexity of radio resource management is expected to increase significantly. Reinforcement learning is seen as a promising solution that can enable intelligent decision-making and reduce the complexity of different optimization problems for radio resource management. The packet scheduler is an important entity of radio resource management that allocates users’ data packets in the frequency domain according to the implemented scheduling rule. In this context, by making use of reinforcement learning, we could actually determine, in each state, the most suitable scheduling rule to be employed that could improve the quality of service provisioning. In this paper, we propose a reinforcement learning-based framework to solve scheduling problems with the main focus on meeting the user fairness requirements. This framework makes use of feed forward neural networks to map momentary states to proper parameterization decisions for the proportional fair scheduler. The simulation results show that our reinforcement learning framework outperforms the conventional adaptive schedulers oriented on fairness objective. Discussions are also raised to determine the best reinforcement learning algorithm to be implemented in the proposed framework based on various scheduler settings. View Full-Text
    • Compensation of the magnetic force imaging by scanning directions

      Liu, Jinyun; Yu, Miao; Qu, Yingmin; Zhang, Wenxiao; Fan, Yinxue; Song, Zhengxun; Qiu, Renxi; Li, Dayou; Wang, Zuobin; Changchun University of Science and Technology; et al. (Elsevier, 2017-08-26)
      It was found that the results of magnetic force microscope (MFM) imaging were different with the probe scanning directions. This paper studied the effect of scanning directions on the MFM imaging, and a method for the distortion compensation was proposed to reduce the errors. In the study, three different scanning directions with the angles of 0°, 45° and 90° were used to measure the magnetic domain structures distributions of magnetic sample. The experimental results have shown that the scanning direction parallel to the magnetic domain structure will cause a minimum phase shift difference and lead to a structure distortion. A method for compensating the distortions was proposed. With this method, the distorted structures were corrected and the effect of scanning directions on the MFM imaging was significantly reduced. This work provides a way for the acquisition of the correct images of magnetic structures using an MFM and the improvement of imaging quality in a wide range of MFM applications.
    • Conceivable security risks and authentication techniques for smart devices

      Muzammal, Syeda Mariam; Shah, Munam Ali; Zhang, Sijing; Yang, Hongji; COMSATS Institute of Information Technology, Pakistan; University of Bedfordshire; Bath Spa University (Springer, 2016-06-29)
      With the rapidly escalating use of smart devices and fraudulent transaction of users’ data from their devices, efficient and reliable techniques for authentication of the smart devices have become an obligatory issue. This paper reviews the security risks for mobile devices and studies several authentication techniques available for smart devices. The results from field studies enable a comparative evaluation of user-preferred authentication mechanisms and their opinions about reliability, biometric authentication and visual authentication techniques.
    • Construction of superhydrophobic surfaces by sol-gel techniques

      Gu, Liang; Wang, Yanyan; Xu, Chengyun; Zhang, Feng; Wu, Zhuhui; Zhang, Xiaoxing; Shi, Zhenwu; Peng, Changsi; Soochow University (Institute of Electrical and Electronics Engineers Inc., 2018-02-08)
      In this work, SÌO2 sol and 1H, 1H, 2H, 2H-perfluorodecylsilane are mixed in a certain proportion by ultrasonic to obtain modified SiO2 sol and gel. A superhydrophobic coating with a contact angle of 160° and a slide angle of less than 5° was constructed by spin coating on a glass substrate. The sol-gel techniques we used is simple and inexpensive, and the as-constructed superhydrophobic coatings are relatively uniform. In addition, by controlling the number of spin coating, the durability of the coating can be effectively enhanced. It is believed that this technique can hold a great potential in superhydrophobic surface fabrication.
    • Content-based image search system design for capturing user preferences during query formulation

      Artemi, Mahmoud; Liu, Haiming; University of Bedfordshire (CEUR-WS, 2020-07-30)
      Most existing studies of content-based image retrieval (CBIR) system design focus on learning users’ information needs through relevance feedback at the result assessment stage only. However, in many CBIR systems, the underlying machine learning mechanisms need the users’ feedback at query formulation stage for a better training and search performance, which unfortunately is often not supported by the search interface design. The lack of support for the users’ query formulation through an effective CBIR interface has been a drawback for system performance and the users’ search satisfaction and experiences. We propose a new CBIR system design approach based on Vakkari’s three-stage model, which encourages the users to provide feedback at the query formulation stage through a user-centered interface. The interface helps the users to form and express their information needs through enabling the users to participate in the training phase of the machine learning mechanism of the system. A user study with 28 participants shows how the proposed system design supports the users’ interaction through the user-centered search interface. The findings of this study highlight the importance for the users to engage in all stages of the search process, especially at the query formulation stage when the considered mechanism requires a training process, through a user-centered interaction design.
    • Content-based technical solution for cyberstalking detection

      Asante, Audrey; Feng, Xiaohua; Catholic University College of Ghana; University of Bedfordshire (Institute of Electrical and Electronics Engineers Inc., 2021-07-27)
      The continued usage of technology has led to the rise of cyberstalking. Cyberstalking is seen as traditional method of stalking that has been altered by technology. This crime has now been modernized using technological tools and techniques. The continued increase in cyberstalking in the world today has drawn attention to the need to address this problem. Though studies on this crime have been conducted in the fields of criminology, legal, public health, sociology, and psychology, it still remains a challenge to detect, prevent, and investigate this crime. Traditional stalking methods have been used to combat it, despite the fact that this crime is committed online. Unfortunately, these methods have provided few solutions for detecting and preventing it. The prevalence of this crime, combined with technological advancement, has necessitated the development of technical strategies to mitigate it, protect victims, and assist law enforcement agencies. In this study, a content-based detection framework for cyberstalking is proposed. The framework consists of message identification, filtering, detection (content detection and profiling offender) and evidence modules. It is designed as a forensic readiness framework that can automatically detect cyberstalking, gather evidence and profile potential offenders. The framework employs machine learning, data mining techniques, digital forensics, and profiling to analyze text, image, and media contents, collect evidence, and profile offenders. This framework would not only detect cyberstalking automatically, but it would also be useful as an investigative tool for law enforcement.
    • Controllable patterning of hybrid silicon nanowire and nanohole arrays by laser interference lithography

      Guo, Xudong; Li, Songhao; Lei, Zecheng; Liu, Ri; Li, Li; Wang, Lu; Dong, Litong; Peng, Kuiqing; Wang, Zuobin (Wiley-VCH Verlag, 2020-03-17)
      Metal-assisted chemical etching (MACE) is a cost-effective method to fabricate Si nanostructures including silicon nanowires (SiNWs) and silicon nanoholes (SiNHs). However, the preparation of metallic template for MACE would require complex experimental conditions including strict cleaning process and multiple steps. Herein, superlens-enhanced laser interference lithography is applied to directly fabricate complicated metallic patterns and then MACE is used to obtain hybrid SiNW and SiNH arrays. Ag films are first deposited on Si substrates, and then a 1064 nm high power laser source is utilized to generate two-beam interference electric fields. Because Ag molecules are very sensitive to any input energy change, they tend to break up or aggregate and form different Ag patterns which have a specific energy threshold to lower its free energy. By manipulating the distribution of input electric field, complicated metallic patterns and their corresponding Si nanostructures with feature sizes that range from tens of nanometers to several micrometers are obtained.
    • Controllable superhydrophobic surfaces with tunable adhesion fabricated by laser interference lithography

      Dong, Litong; Zhang, Ziang; Ding, Ran; Wang, Lu; Liu, Mengnan; Weng, Zhankun; Wang, Zuobin; Li, Dayou; Changchun University of Science and Technology; Changchun Observatory; et al. (Elsevier, 2019-05-15)
      Superhydrophobic surfaces with tunable wettability have attracted much attention in recent years, and many techniques have been developed to fabricate artificial function structures. However, applications of tunable adhesive superhydrophobic surfaces have been limited due to ambiguous structural factors on wettability. In thispaper, we studied the relationship between the surface adhesion and geometry parameters of periodic submicron structures, and presented a facile approach for the fabrication of controllable superhydrophobic surfaces with tunable adhesion through laser interference lithography (LIL) combined with inductively coupled plasma (ICP) etching. The wettability properties of periodic geometry structures were selected by tailoring the top area ratio of the pillar array. The findings of this work will contribute to quantifying structural parameters on the submicron scale through the combination of three-beam LIL and ICP etching for designing and developing new systems for micro-droplet manipulation. This approach can find potential applications in many fields such as targeted drug delivery, biomolecular quantitative detection, selective liquid transportation and oil/water separation.
    • Controlled manipulation of TRAIL into single human colon cancer cells using atomic force microscope

      Qu, Yingmin; Liu, Jinyun; Wang, Guoliang; Song, Zhengxun; Wang, Zuobin; Changchun University of Science and Technology; University of Bedfordshire (Institute of Electrical and Electronics Engineers Inc., 2018-02-08)
      In this study, an AFM tip was used to penetrate the human colon cancer cells (SW480) in the culture medium containing pEGFP-N1-TRAIL plasmids. The trail plasmids encoded with the enhanced green fluorescent protein (EGFP) were moved into the SW480 cells through membrane holes created by the AFM probe. Following the penetration, the culture medium was changed into the RPMI1640 medium supplemented with 10% of fetal bovine serum and incubated for 24h. The expression of PEGFP-N1-TRAIL in SW480 cells was then observed by inverted fluorescence microscope. The experiment results indicate that the AFM tip can be used to penetrate the membranes of targeted cells individually.
    • Controlled self-assembly of lambda-DNA networks with the synergistic effect of a DC electric field

      Gao, Mingyan; Hu, Jing; Wang, Ying; Liu, Mengnan; Wang, Jianfei; Song, Zhengxun; Xu, Hongmei; Hu, Cuihua; Wang, Zuobin; (American Chemical Society, 2019-11-04)
      Large-scale and morphologically controlled self-assembled λ-DNA networks were successfully constructed by the synergistic effect of a DC electric field. The effect of DNA concentration, direction, and intensity of the electric field, even the modification of the mica surface using Mg2+ on the characteristics of the as-prepared DNA networks, were investigated in detail by atomic force microscopy (AFM). It was found that the horizontal electric field was more advantageous to the formation of DNA networks with more regular structures. At the same concentration, the height of DNA network was not affected significantly by the intensity change of the horizontal electric field. The modification of Mg2+ on mica surface increased the aggregation of DNA molecules, which contributed to the morphological change of the DNA networks. Furthermore, DNA molecules were obviously stretched in both horizontal and vertical electric fields at low DNA concentrations.