Experimental and Simulated Performance Evaluation of Bifacial Photovoltaic Floating System With a Horizontal Single-Axial Tracker

Experimental performance evaluation and comparative analyses of heat pipe and direct flow augmented solar collectors

The advantage of proton therapy over conventional photon therapy is compromised by proton range uncertainty and dose monitoring is of critical importance to improve the precision of proton therapy. In this work, we report the design and performance evaluation of a prompt gamma imaging (PGI) system being developed in our lab, with high spatial resolution, high sensitivity and 2D imaging capability for real-time proton therapy monitoring. Key components of the PGI system include a multi-slit tungsten collimator, a scintillation detector array based on BGO block and SiPM, a customized ASIC-based readout electronics and a White Rabbit (WR) switch-based data acquisition electronics. Initial experimental evaluation of the detector module with the system electronics demonstrated the feasibility of the detector module for prompt gamma detection. Spatial resolution, sensitivity and Bragg peak positioning accuracy of the system was investigated with GATE simulations. The sensitivity measured at FOV center was 0.251%. ~2 mm spatial resolution was achieved for different FOV regions in both X and Y directions with slightly better spatial resolution in X direction. Bragg peak positioning accuracy was quantified by positioning bias and root mean square error (RMSE) of the most distal edge position (MDEP) of the reconstructed prompt gamma images and evaluated under different count levels. With the count level increasing from 104 to 106, a sharp decrease in MDEP error from 2.29 mm to 0.76 mm was observed, indicating improved Bragg peak positioning accuracy under higher count levels and excellent Bragg peak positioning capability of the PGI system. To conclude, the designed PGI system is viable for proton therapy monitoring. Further system assembling and experimental performance evaluation in real proton therapy facility are ongoing.

Wireless links are often subject to burst errors leading to consecutive packet losses, which could be buffered and transmitted later, giving priority to packets on stronger links. This improves overall bandwidth utilization. A channel state dependent scheduling protocol based on the above idea is developed and implemented in a wireless LAN. A commercial wireless LAN, Lucent Technology's Wavelan, is used with Pentium based laptops and PCs. The protocol is implemented as a part of the device driver in the Linux operating system. The protocol includes a channel sensing mechanism to help determine when a wireless link comes out of the error state. Experimental performance evaluation with UDP streams and FTP sessions demonstrates the significant performance benefits of channel state dependent scheduling. The performance evaluation includes a novel channel modulation technique based on previously collected traces for reproducibility of experiments.

This paper presents GREP, a novel group rekeying scheme that leverages the history of join events in order to achieve efficiency and high scalability. GREP rekeys the group with only two broadcast messages, hence displaying an overhead which is small, constant and independent of the group size. Also, GREP efficiently recovers the group from collusion attack with no recourse to total member reinitialization. Even in the very unlikely worst case, collusion recovery displays a smooth impact on performance that gradually increases with the attack severity. We implemented GREP for the Contiki OS and tested it on different resource-constrained platforms. Our analytical and experimental evaluation confirms that GREP is efficient, highly scalable and deployable also on constrained nodes. The paper extends a previous version of this work, especially through additional security analysis, treatise of probabilities for worst case collusion, and experimental evaluation of performance.

Experimental investigation and performance evaluation of a mixed-flow air to air membrane enthalpy exchanger with different configurations

Reiterative deconvolution: New technique for time of flight estimation errors reduction in case of close proximity of two reflections

All‐optical multiwavelength conversion (MWC) enables optical layer multicast without electronic processing. Wavelength conversion by four‐wave‐mixing (FWM) offers strict transparency in bit rate and modulation format. In this letter, a novel FWM MWC scheme is proposed, supported by theoretical analysis and experimental performance evaluation at 10/20/40 Gb/s. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49:1067–1071, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22358

This paper presents the experimental performance evaluation of the distributed Virtual Home Region Multi-Hash Location Service (VIMLOC). This is, up to our knowledge, the first location management scheme specifically designed and implemented for medium/large-scale wireless mesh networks (WMNs,) which are seen as a cost-effective solution to provide broadband wireless access in large areas. Therefore, if the use of geographic routing is assumed for scalability reasons, such a location management is needed to map between the identifier of a node and its current position in the network (i.e., location address). Furthermore, this paper also presents what is, up to our knowledge, the first experimental performance comparison over a WMN testbed of three different location management schemes, namely proactive, reactive, and VIMLOC. All three schemes have been implemented in the Click modular router framework. For the scenario under test, the quantitative results show that the VIMLOC protocol has comparable (or better) success rate to that of the proactive and reactive schemes. Additionally, VIMLOC outperforms these schemes in terms of overall overhead, state volume, and efficiency parameters, in general.

Wi-Fi Peer to Peer (P2P), commercially known as Wi-Fi Direct, is a recent industry standard that allows user devices to communicate with each other without requiring a Wi-Fi access point or Internet connectivity. Offering promising solutions for secure and high-throughput device to device communication over moderately high range, Wi-Fi P2P can potentially revolutionize M2M communication and Internet of Things (IoT) towards an all-connected wireless ecosystem. Secure Digital (SD) memory cards with built-in processing unit and Wireless LAN chipset can serve as a small standalone communication terminal which on installation of a communication protocol stack and a data-sharing application may enable connection establishment and data communication between memory cards. Such architecture may find interesting applications with manifold advantages for device-to-device data sharing in public gatherings without requiring cellular network or WLAN access points. In this paper, we develop an architecture to establish Wi-Fi P2P connection between SD memory cards and enable automatic data sharing by proximitybased device-to-device communication between mobile user equipments. The prototype does not use any of the resources of host device barring power. The key contribution of this paper is the development of a standalone prototype of our proposition on off-the-shelf WLAN SD memory cards and its experimental performance evaluation.

Bypass dual throat nozzle (BDTN) is a modern concept of fluidic thrust vector control. This method able to solve the problem of thrust loss without need the secondary mass flow from other part of engine. Internal nozzle performance and thrust vector angles have been measured in the BDTN experimentally and numerically. A new simple approach is proposed to detect the thrust deflection angle. Numerical simulation of 3-D turbulent air flow is carried out by using the RNG k-e turbulence model. The obtained results of thrust coefficient, discharge coefficient and thrust deflection angle have been validated by comparing with measured experimental data. The results show that for nozzle pressure ratio of 1–4 the tested nozzle able to deflect the thrust vector of 26.5°-19°. By increasing NPR from 2 up to 4, the thrust coefficient values will change in the range of 0.85-0.93. Also the effect of different positions of the bypass channel on the BDTN performance parameters has been investigated numerically. The predicted results show that the BDTN configuration with bypass duct on the first nozzle throat has the highest value of thrust deflection angle over the range of NPRs.

The objective of this research is to experimentally evaluate the lubrication performances of different nanofluids in milling titanium alloy Ti-6Al-4V. Six types of nanofluids, namely, Al2O3, SiO2, MoS2, CNTs, SiC, and graphite, were selected. Cottonseed oil was used as the base oil. The lubrication performance was investigated in terms of milling force, surface roughness, and morphology of workpiece surface. Experimental results demonstrated that the Al2O3 nanoparticle obtained the minimal milling force (Fx = 277.5 N, Fy = 88.3 N), followed by the SiO2 nanoparticle (Fx = 283.6 N, Fy = 86.5 N). The surface roughness obtained by the Al2O3 nanofluid was the minimum (Ra = 0.594 μm), whereas it was the maximum by using minimum quantity lubrication (Ra = 1.772 μm). The surface roughness of the six nanofluids was described by the following order: Al2O3 < SiO2 < MoS2 < CNTs < graphite < SiC. The workpiece surface morphology was the best for Al2O3 and SiO2. The viscosity of the nanofluids was also analyzed. Spherical Al2O3 and SiO2 nanoparticles improved the lubrication effect of base oil mostly and were more suitable as environment-friendly additives for the base oil compared with the others.

In this chapter, a thorough treatment of the modulation schemes for UG Wireless is presented. The effects of soil texture and water content on the capacity of multi-carrier modulation in WUC are discussed. The multi-carrier capacity model results are analyzed. Moreover, the underground MIMO design for underground communications is explained thoroughly. An analysis of medium access in wireless underground is done as well. Furthermore, the soil properties are considered for cross-layer communications of UG wireless. The performance analysis of traditional modulation schemes is also considered. The soil moisture-based modulation approach is also explored in this chapter. The connectivity and diversity reception approaches are discussed for wireless underground communications. The connectivity and interference models are studied for Ad-Hoc and Hybrid Networks. The topology control mechanisms for maintaining network connectivity are explored for maximizing network capacity under the physical models (e.g., the protocol interference model and physical interference model). Moreover, the underground diversity is examined for 3W-Rake receiver and coherent detection along with experimental evaluation and comprehensive analysis of performance of equalization techniques.

A long term healthcare monitoring system requires battery operated devices with low-power technologies. Researchers tried to adapt various short-range technologies for Wireless Body Area Networks (WBANs) in ubiquitous health monitoring. The classical Bluetooth is known for its greedy power consumption, IrDA and NFC require line-of-sight conditions, and ANT has weak coexistence features and interference issues. A typical choice remains ZigBee/6LoWPAN over IEEE 802.15.4 based solutions in WBANs because of their low-power consumption. However, the recently proposed Bluetooth Low Energy (BLE) announced more compelling features in various aspects. Only few studies have been published supporting these claims on BLE. In this paper, we present a BLE based remote healthcare monitoring platform and we study its compatibility for ECG monitoring. ECG data requires continuous and real-time transmissions, making it particularly challenging for resource constrained devices. In our system, a BLE112 module from Bluegiga and a BLE USB dongle are used for WBAN. The performance of the system is evaluated experimentally and the results showed good potential of this proposed BLE platform in meeting the main QoS requirements of medical applications in terms of throughput, end-to-end delay, and packet error rate, while staying energy efficient.

High-voltage amplifiers as a means of amplifying the low-output voltage signals of the feedback controllers to the suspension voltages typically in the kilovolts range are often required for electrostatic force generation in electrostatic levitation. This paper proposes a high-voltage do amplifier including an amplitude modulator, a power amplifier, a step-up transformer, a pair of peak detectors, and a voltage feedback channel to stabilize the amplifier outputs in an effort to provide high suspension voltage and fast dynamic response. Since the various carrier frequencies have virtually no effect on the power consumption of the do amplifier by filtering out the high-frequency carrier components with peak detectors while keeping the input signal unaffected, satisfactory dynamic performance can be achieved by choosing a sufficiently high carrier frequency. The operating principle of the dc amplifier is analyzed, followed by an experimental performance evaluation and discussion for electrostatic levitation applications. The experimental results demonstrate the superiority of the high-voltage do amplifier over classical ac amplifiers in terms of dynamic response, force-voltage coefficient, voltage ripple, power consumption, and long-time stability using a carrier frequency of 30 kHz and the closed-loop control scheme.

The availability and adoption of a wide range of mobile computing devices (e.g., laptops, personal digital assistants (PDA s), wearable computers) of varying sizes and processing capabilities, along with the emergence of wireless local‐area networks (WLAN s) and wireless personal‐area networks (WPAN s), are enabling the ubiquitous access of information anywhere, anytime. These networks are frequently being used as extensions to the Internet, and end users are increasingly exploiting them to access wireless Internet services. One of the emerging short‐range wireless networking technologies that shows great promise as an enabling technology in the deployment of WPAN s is the recent industry‐standard Bluetooth. In this article, we explore by design, implementation, and experimental performance evaluation, mechanisms and approaches that enable Bluetooth devices to achieve (1) seamless IP connectivity to external IP ‐based networks, (2) high performance even in the presence of IEEE 802.11 interfering traffic, and (3) efficient support for high‐quality audio by exploiting the Audio/Video Distribution Transport Protocol (AVDTP ). We anticipate that our reported experiences and practical results will benefit network designers, developers, and users of Bluetooth technology in WPAN environments.