Resonant and Nonresonant All-Optical Switching Devices in GaAs/GaAlAs

The resonant refractive and absorptive optical nonlinearity of a GaAs/GaAlAs single quantum well waveguide are characterised; hh and Ih excitons are well resolved at room temperature. The unsaturated resonant nonlinear refractive index coefficient n2 was 1.4x10e-8 cm2/W, measured using the external Mach-Zehnder interferometric technique. It has been shown that the recovery time of the resonant nonlinearity is reduced to 125 ps (1/e recovery time), by placing the single quantum well close to the top surface. All-optical switching of an integrated asymmetric Mach-Zehnder interferometer is demonstrated and it was shown experimentally and theoretically that due to the absorption saturation, a complete switching is not possible. The nonresonant nonlinear optical properties of GaAlAs waveguide were characterised at photon energy below half the band gap

An Accurate Performance Analysis of Hybrid Efficient and Reliable MAC Protocol in VANET under Non-saturated Conditions

Vehicular Ad Hoc Networks (VANETs) is a technology supporting two types of applications, safety and service applications with higher and lower priorities respectively. Thereby, Medium Access Control (MAC) protocol is designed to provide reliable and efficient data broadcasting based on prioritization. Different from the IEEE 1609.4 (legacy), HER-MAC protocol is a new multi-channel MAC proposed for VANETs, offering remarkable performance with regards to safety applications transmission. This paper focuses on the analysis of packet delivery ratio of the HER-MAC protocol under non-saturated conditions. 1-D and 2-D Markov chains have been developed for safety and non-safety applications respectively, to evaluate mathematically the performance of HER-MAC protocol. The presented work has taken into account the freezing of the backoff timer for both applications and the backoff stages along with short retry limit for non-safety applications in order to meet the IEEE 802.11p specifications. It highlights that taking these elements into consideration are important in modeling the system, to provide an accurate estimation of the channel access, and guarantees that no packet is served indefinitely. More precise results of the system packet delivery ratio have been yield. The probability of successful transmission and collisions were derived and used to compute the packet delivery ratio. The simulation results validate the analytical results of our models and indicate that the performance of our models outperformed the existing models in terms of the packet delivery ratio under different number of vehicles and contention window

Centralized scheduling, routing tree in WiMAX mesh networks

In the last few years, demand for high speed internet access service has increased greatly so the IEEE 802.16 working group on broadband wireless access (BWA) is developing the worldwide interoperability for microwave access (WiMAX) standard for wireless metropolitan area networks (MANs) which aims to provide broadband wireless last mile access, easy deployment, and high speed data rate for large spanning area. This paper propose an efficient routing and collision free centralized scheduling (CS) algorithms using single channel single transceiver system in WiMAX mesh network, which introduces the cross layer concept between the network layer and media access controller (MAC) layer. The proposed approach has improved the system performance in the aspects of scheduling length, channel utilization ratio (CUR), and the throughput of the system

Review of network routing in IEEE 802.16 WiMAX mesh networks

The rapid growth of high-speed multimedia services for mobile, residential and small business customers has created an increasing demand for last mile broadband access. Technologies based on 802.16 which called WiMAX (Worldwide Interoperability Microwave Access) promises to deliver high data rates over large distances and deliver multimedia services and are expected to play a major role in high speed broadband delivery. Routing in Wireless Mesh Network (WMN) is challenging because of the unpredictable variations of the wireless environment. Traditional mechanisms have been proved that the routing performance would get deteriorated and ideal metrics must be explored. There are various challenges for the routing in WiMAX mesh such as delay, long transmission scheduling, and increasingly stringent Quality of Service (QoS) support and load balance and fairness limitations. The goal of this paper is to review some routing algorithms proposed by various authors for IEEE 802.16 mesh networks. This paper discusses the problem of routing for providing QoS, for minimizing interference, robustness and fairness in detail

Ultrafast All-Optical Switching In Gaalas Directional-Couplers At 1.55 Mu-M Without Multiphoton Absorption

We demonstrate ultrafast, high throughput, all-optical switching in optimized, 2-cm-long, half- and full-beat-length nonlinear directional couplers operated at 1.55 mum, below half the band gap of Ga0.82Al0.18As. The long device length allowed the elimination of nonlinear loss and resulted in a switching peak power and energy of 85 W and 65 pJ, respectively

Cucurbituril—assisted sensitive fluorescence detection and quantitation of naproxen drug in wastewater samples: Guest-host characterization and HPLC investigation

Sensitive spectrofluorometric and liquid chromatography with fluorescence detection methods have been developed for detection and determination of naproxen drug in the presence of cucurbit7uril (CB7). Fluorescence signals have been improved with the addition of CB7 to the drug aqueous solution. Fluorescence spectroscopy, mass spectrometry, 1H-NMR, and liquid chromatography with fluorescence detection were used to investigate the guest-host interaction of naproxen drug and cucurbiturils. Naproxen was found to form a supramolecular complex with CB7 that had a high formation constant. The optimal conditions for the interaction were discovered using spectroflurometry to be 0.2 mg/ml of CB7, 2.4 μg/ml of naproxen drug, and pH10. A 1:1 complex between naproxen and CB7 is revealed by proton NMR and tandem mass spectrometry. Using the standard addition calibration method, an HPLC with a fluorescence detector was used to detect naproxen in influent and effluent wastewater samples. Finally, it was discovered that the measured concentrations of naproxen in the influent and the effluent wastewater were 1.87 × 10−4 ppb and 2.1 × 10−5 ppb, respectively. This was done by sample enrichment, which reduced the 1000 mL into 1 ml

Unequal error protection for wireless data transmission using superposition coding with feedback

High quality of data transmission services is an important task for wireless broadband communication systems. This paper is concerned with the design problem of real-time wireless data transmission which provides unequal error protection (UEP). Using superposition coding, the rea-time data stream is divided into two streams, high priority (HP) and low priority LP streams depending on their interest. These two bit streams are encoded separately, and then superimposed together with two different level of power to achieve the UEP for them in the receiver end. Feedback of channel state information (CSI) is used in adaptive physical layer channel for efficient use of the current available bandwidth. In this proposed scheme, same recourses; time, bandwidth and power are used to increase the transmission efficiency compared with other schemes which are use transmission of one data stream with one power level but in different techniques to exploit the available bandwidth

Cross layer design in 802.16d

WiMAX based wireless mesh network aims to provide broadband wireless for the last-mile access. It has high-speed data rate for large spanning area and is the key topology for the next generation wireless networking. The WIMAX mesh network (WMN) is developed with the use of base station (BS) as the main controller. However, the effects of the interferences from the transmission of the neighboring nodes within the mesh networks are inevitable and critical because all the nodes are using the same medium to communicate. This paper presents a cross-layer design that rely on the routing information in network (NET) layer and the scheduling slots in the medium access control (MAC) layer. The construction of the routing path with multi-channel single transceiver system and single channel single transceiver is proposed together with centralized scheduling (CS) algorithms that reduce the existing interferences in WMN. The analysis results show that the proposed algorithms have significantly improved the system performance in term of length of scheduling, channel utilization ratio (CUR), and throughput of the system

Development and validation of a tool to improve community pharmacists' surveillance role in the safe dispensing of herbal supplements

Background: There has been an appreciable increase in the use of herbal supplements, including immune boosters, during the current COVID-19 pandemic. However, there are concerns with falsified herbal supplements Objectives Developed a new questionnaire that can potentially help community pharmacists with identifying the extent of falsified herbal supplements. Methods: A cross sectional study conducted over nine months among 500 community pharmacies in the UAE. Face-to-face interviews were undertaken using a structured questionnaire, which was subjected to face and content validity, with the content validity index (CVI) computed. Construct validity was tested using an exploratory factor analysis (EFA) via principally component analysis (PCA). The model was then confirmed through Partial confirmatory factor analysis (PCFA). Reliability was assessed via test-retest reliability, internal consistency, item internal consistency (IIC), and intraclass correlation coefficients (ICCs). Results: An instrument compromised of five domains with a 24-item scale was developed with CVI of 0.843. The KMO measure of sampling adequacy was 0.891, and Bartlett’s test of sphericity indicated significance (p-value < 0.001). Confirmation of the subsequent 5-domains was achieved through PCFA using MLA with oblimin rotation. The PCFA obtained values of 0.962 for NFI, 0.977 for CFI, and 0.987 for TLI; all values were greater than 0.95, and the RMSEA value was 0.03 (i.e., less than 0.06). Consequently, the model had a good fit. All domains demonstrated Cronbach’s alpha coefficients above 0.70, with 0.940 for the full instrument. Meanwhile, all items met the IIC correlation standard of ≥ 0.40. The instrument presented good ICC statistics of 0.940 (0.928 – 0.950) as well as statistical significance (p < 0.001). Those participants who had more than 10 experience years more likely to identify falsified herbal supplements compared to those who have 1 to 10 experience years (p < 0.001). Conclusions: This study developed and validated a new instrument to identify safe herbal supplements products, which will help enhance the role of the community pharmacists in safe and effective treatment of suitable patients with herbal supplements