Recent Submissions

  • Performance Assessment of Various PV Module Types under Desert Conditions through Device Simulations and Outdoor Measurements

    Katsaounis, Theodoros; Kotsovos, K.; Gereige, I.; Basaheeh, A.; Abdullah, M.; Khayat, A.; Al Habshi, E.; Al-Saggaf, A.; Tzavaras, Athanasios (EUPVSEC 2019 Proceedings, EUPVSEC, 2019-10-23) [Conference Paper]
    The Middle East region is considered as one the most promising areas for PV deployment due to its vast solar potential. Despite this fact, successful deployment of PV systems in the region is challenging due to local weather conditions. Dust storms are very frequent in these areas, which not only cause heavy soiling on PV module surface but may also significantly affect the form and intensity of the solar spectrum due to airborne dust particles which scatter sunlight. In addition, the combination of high ambient temperatures and increased irradiance levels pose additional challenges in PV module performance and reliability. Therefore, in this work a customized device simulator is proposed aiming to provide accurate calculations of PV module energy yield and performance using local climate data including solar radiation spectrum and temperature measurements. Simulation data are validated with outdoor IV measurements on various types of commercial c-Si based PV modules including polycrystalline Si and bifacial PERC, located at KAUST University at the Western Region of Saudi Arabia.Seasonal performance variations of various solar cell technologies due to local spectrum variations are also investigated.
  • Non-Hermitian Broad Aperture Semiconductor Lasers Based on PT-Symmetry

    Botey, Muriel; Ahmed, Waqas Waseem; Medina, Judit; Herrero, Ramon; Staliunas, Kestutis (IEEE, 2019-09-20) [Conference Paper]
    In this paper we propose a novel configuration to regularize the complex spatiotemporal dynamics of broad area lasers into bright light beam. It has recently been shown that arbitrary non-Hermitian optical potentials based on local Parity-Time (PT-) symmetry may tailor and control the flow of light, due to the asymmetric mode coupling. We now provide a comprehensive analysis on how this can be applied to stabilize the emission from broad aperture semiconductor lasers. The mechanism relies on a non-Hermitian configuration of the laser potential achieved by simultaneous spatial modulation of the refractive index and gain-loss profiles. This allows concentrating the light into a bright and narrow output beam. We provide a numerical analysis on Vertical Cavity Surface Emitting lasers and Broad Area Semiconductor Lasers. The results indicate a significant intensity enhancement and concentration of the emitted stabilized beam. The proposed mechanism may be technologically achievable, and it is expected to be applicable to regularize the radiation of other broad aperture and microlasers, which typically emit quite random and irregular light patterns. Besides, the reported concentration effect is universal, and could be extended to random and quasi-periodic background potentials.
  • Non-Hermitian Light Management Based on Local Hilbert Transform

    Staliunas, K.; Ahmed, Waqas Waseem; Botey, M.; Herrero, R. (IEEE, 2019-09-20) [Conference Paper]
    We demonstrate a novel idea of nonhermitian management of light based on a local Hilbert transform. Local Hilbert transform, a substantial modification of classical Hilbert transform allows to design non-Hermitian vector fields of arbitrary directionality, p (r), with desired shapes and topologies. We derive a local Hilbert transform to systematically build such potentials, by modifying background potentials (being either regular or random, extended or localized). In particular, we explore particular directionality fields, for instance in the form of a focus to create sinks for probe fields (which could help to increase absorption at the sink), or to generate vortices in the probe fields. Physically, the proposed mechanism provide a flexible new tool for dynamically shaping and precise control over probe fields leading to novel effects in nonlinear wave dynamics, and in particular in broad area microlasers.
  • In Situ Injection Rate Measurement to Study Single and Split Injections in a Heavy-Duty Diesel Engine

    Aljohani, Bassam S. E.; Ben Houidi, Moez; Babayev, Rafig; Aljohani, Khalid; Johansson, Bengt (SAE International, 2019-09-12) [Conference Paper]
    The split injection strategy holds a potential for high pressure combustion engines. One advantage of such strategy is the capability to control the heat release rate, which also implies the use of multiple split-injections with relatively short dwell intervals. Most injection rate measurement techniques require installment of the injector on a dedicated test rig. However, these techniques fail to accurately reproduce real-engine operating conditions. Using the spray impingement method, this paper investigates the injection rate of a high flow-rate solenoid injector while being operated on the engine. The aim is to have an experimental configuration as similar as possible to the real engine in terms of the acoustics and the fuel temperature within the injection system. The assumption of spray force proportional to the spray momentum is used to measure the injection rate. The spray momentum is measured while the injector is mounted on the Volvo D13 engine and connected to the in-series fuel rail and pump. A high-natural-frequency piezoelectric pressure transducer is mounted perpendicularly at 4 mm from one of the nozzle holes. The injector and sensor are contained within a specially designed collector for the injected fuel, which is maintained at atmospheric pressure and temperature. Experiments with single injection are conducted varying the Duration of Injection (DOI) from 400 up to 2000 µs. The tests with split double-injections are conducted with fixed DOI of 500 µs while the dwell time are varied from 100 up to 1000 µs. All tests are performed at the rail pressures of 500, 1000, 1500 and 2000 bar while the engine is operated at 1200 rpm. Results show that the injection rate shape of single injections is highly dependent on the rail pressure profile. With double split-injections, the rate of the second injection as well as the total fuel mass injected increases when the dwell time is shortened. Short dwell intervals boost the fuel quantities as a result of the altered needle response. Long dwell time between two equally-long injections generate similar injection rates. The injector hydraulic delay was more pronounced when dwell time was kept long enough. Overall, higher injection pressure advances the effective start of injection while retarding the effective end of injection.
  • A Lagrangian Method for Extracting Eddy Boundaries in the Red Sea and the Gulf of Aden

    Friederici, Anke; Mahamadou Kele, Habib Toye; Hoteit, Ibrahim; Weinkauf, Tino; Theisel, Holger; Hadwiger, Markus (IEEE, 2019-09-05) [Conference Paper]
    Mesoscale ocean eddies play a major role for both the intermixing of water and the transport of biological mass. This makes the identification and tracking of their shape, location and deformation over time highly important for a number of applications. While eddies maintain a roughly circular shape in the free ocean, the narrow basins of the Red Sea and Gulf of Aden lead to the formation of irregular eddy shapes that existing methods struggle to identify. We propose the following model: Inside an eddy, particles rotate around a common core and thereby remain at a constant distance under a certain parametrization. The transition to the more unpredictable flow on the outside can thus be identified as the eddy boundary. We apply this algorithm on a realistic simulation of the Red Sea circulation, where we are able to identify the shape of irregular eddies robustly and more coherently than previous methods. We visualize the eddies as tubes in space-time to enable the analysis of their movement and deformation over several weeks.
  • A Micro-Resonator Based Digital to Analog Converter for Ultralow Power Applications

    Ahmed, Sally; Zou, Xuecui; Fariborzi, Hossein (IEEE, 2019-08-22) [Conference Paper]
    This paper presents a micro-resonator based digital to analog converter (DAC) for the internet of things (IoT) and low power applications. The device consists of a clamped-clamped micro-resonator with multiple electrodes. To enable the operation as a DAC, the air-gap between each partial electrode and the beam is varied based on the weight of input bits, so the beam’s resonance frequency and the output amplitude are decided by digital inputs. The tested DAC consumes 7 pJ/conversion step with a sampling rate of 64 S/s. We show that a sampling rate of 0.1 MS/s and energy/conversion of 2.7 fJ can be achieved by moderate device scaling.
  • A Decomposition Approach for Complex Gesture Recognition Using DTW and Prefix Tree

    Chen, Hui; Ballal, Tarig; Al-Naffouri, Tareq Y. (IEEE, 2019-08-15) [Conference Paper]
    Gestures are effective tools for expressing emotions and conveying information to the environment. Sequence matching and machine-learning based algorithm are two main methods to recognize continuous gestures. Machine-learning based recognition systems are not flexible to new gestures because the models have to be trained again. On the other hand, the computational time that matching methods required increases with the complexity and the class of the gestures. In this work, we propose a decomposition approach for complex gesture recognition utilizing DTW and prefix tree. This system can recognize 100 gestures with an accuracy of 97.38%.
  • Stability and Trajectories Analysis of a Fractional Generalization of Simple Pendulum Dynamic Equation

    Ndoye, Ibrahima; Kirati, Taous-Meriem Laleg (IEEE, 2019-08-15) [Conference Paper]
    In this paper, we present the dynamics of the simple pendulum by using the fractional-order derivatives. Equations of motion are proposed for cases without input and external forcing. We use the fractional-order Euler-Lagrange equations to obtain the fractional-order dynamic equation of the simple pendulum. We perform equilibria analysis, indicate the conditions where stability dynamics can be observed for both integer and fractional-order models. Finally, phase diagrams have been plotted to visualize the effect of the fractional-order derivatives.
  • Cracking open the black box: What observations can tell us about reinforcement learning agents

    Dethise, Arnaud; Canini, Marco; Kandula, Srikanth (ACM Press, 2019-08-14) [Conference Paper]
    Machine learning (ML) solutions to challenging networking problems, while promising, are hard to interpret; the uncertainty about how they would behave in untested scenarios has hindered adoption. Using a case study of an ML-based video rate adaptation model, we show that carefully applying interpretability tools and systematically exploring the model inputs can identify unwanted or anomalous behaviors of the model; hinting at a potential path towards increasing trust in ML-based solutions.
  • Flexible and Multi-Functional Graphene Sensor Platform

    Kaidarova, Altynay; Almoudi, Abeer; Allagani, Renad M.; Marengo, Marco; Khan, Mohammed Asadullah; Buttner, Ulrich; Duarte, Carlos M.; Kosel, Jürgen (IEEE, 2019-08-08) [Conference Paper]
    This paper presents a flexible, printed and robust sensor platform for the detection of various parameters: strain, flow speed, pressure, conductivity, temperature and magnetic field. The sensors are based on Laser-Induced Graphene fabricated by laser printing on Kapton substrate. Multi-functionality is obtained by exploiting printing process combined with the flexible nature of Kapton and the piezoresistivity of Graphene. Sensor have been implemented for the detection of strain, flow speeds, forces pressure, salinity and magnetic field. Their sensitivity and dynamic range can be tailored via the substrate and laser printing design. A robust and reliable operation was obtained during underwater experiments in the Red Sea.
  • Theroratical Study of Fully Printed Magnetically Tunable Reconfigurable Patch Antenna

    Ghaffar, Farhan A.; Vaseem, Mohammad; Roy, Langis; Shamim, Atif (IEEE, 2019-07-26) [Conference Paper]
    Due to varying wireless standards in different regions, there is a big desire to have reconfigurable and tunable components which can be tuned to the frequency of interest. At present a single wireless device, such as a mobile phone contains multiple antennas, filters, all of them working at different frequencies. It will be great if an antenna or a filter can be tuned to work at different frequencies, thus the overall number of antennas or filters in a device can be reduced. This control is possible through a magnetic field, if these components are built on a magnetic substrate. Traditional magnetic substrates are expensive that involve complicated fabrication process and operate the material in saturated state making them inefficient. A better approach would be to operate the antenna or any other microwave device in the partially magnetized state. In this work, the authors present the theory and design of a polarization reconfigurable patch antenna with frequency tunablity in the unsaturated state. Operating away from the saturated state can improve the overall efficiency of the RF components. The analytical model is initially verified using a high frequency simulator to predict the antenna performance on a magnetic substrate with normal bias. A low-cost printing technique where the substrate could be realized using magnetic ink is used for the implementation of the antenna. A circular patch antenna working at 6 GHz is used for the validation of the theory. When triggered by an external magnetic field, the as-fabricated antenna shows a maximum tuning range of ~16% and ~5% for the two splitted frequency points. A good match is achieved between the theory, simulations and measurements of the antenna.
  • Flexibility Assesment of Fully Inkjet-Printed Reconfigurable Antenna With VO2 Switch

    Vaseem, Mohammad; Su, Zhen; Yang, Shuai; Shamim, Atif (IEEE, 2019-07-26) [Conference Paper]
    With the surge of Internet of Things (IoT) applications, billions of wireless devices need to be manufactured which could be mounted on non-planar objects or be worn by humans. This is where printing flexible electronics can be a game changer. Recently, frequency-reconfigurable radio-frequency (RF) components are in high demand due to multiple frequency-bands in wireless devices. A very important part of reconfigurable components is RF switch. Traditional switches are based on PIN diode, microelectromechanical-systems (MEMS), transistor, ferrite- and ferro-electric based devices. All these traditional switches have their own sets of advantages and disadvantages, however, one issue is common, almost all RF switches need to be soldered or attached to the reconfigurable components. Thus, it is hard to maintain switch configuration in flexible condition. To overcome these issues, we demonstrate a printing technique to fabricate reconfigurable antenna supported on flexible kapton substrate with switch based on VO2 ink. The fully printed antenna operates at 2.5-3.5 GHz when the switch is in the OFF state. When switch is thermally activated in the ON state, it operates at 1.6-2.6 GHz. The printed antenna shows a maximum gain of ~2 dBi at 3.2GHz with concave bending position. Antenna performance in different bent configurations supports its uses for many RF designs that require reconfigurability and tunability.
  • 3D Printed Near-isotropic Asymmetric Dipole Antenna-on-Package for IoT Applications

    Su, Zhen; Klionovski, Kirill; Bilal, Rana Muhammad; Shamim, Atif (IEEE, 2019-07-26) [Conference Paper]
    Internet of Things (IoT) applications have received massive attention in the previous decade. An antenna designed for such applications/devices needs to satisfy bandwidth requirement of concerned communication protocol whilst maintaining a near isotropic radiation pattern. This is important so that the device can communicate without effect from its orientation. The antenna also needs to provide sufficient gain, be small in size and weight for easy integration with the devices and ideally be low cost for feasible volume fabrication. This paper presents a Bluetooth 2.45 GHz Antenna-on-Package that satisfies all of the above-mentioned requirements and thus is suitable for IoT applications. The presented antenna has superior maximum gain (1.56 dB) and gain margin (5.05dB) compared to relevant designs in research literature and is fabricated using additive manufacturing technique. The presented design also considers the effect of components i.e. battery and Bluetooth chip in optimization model.
  • Interview choice reveals your preference on the market: To improve job-resume matching through profiling memories

    Yan, Rui; Zhang, Tao; Le, Ran; Zhang, Xiangliang; Song, Yang; Zhao, Dongyan (Association for Computing Machineryacmhelp@acm.org, 2019-07-25) [Conference Paper]
    Online recruitment services are now rapidly changing the landscape of hiring traditions on the job market. There are hundreds of millions of registered users with resumes, and tens of millions of job postings available on the Web. Learning good job-resume matching for recruitment services is important. Existing studies on job-resume matching generally focus on learning good representations of job descriptions and resume texts with comprehensive matching structures. We assume that it would bring benefits to learn the preference of both recruiters and job-seekers from previous interview histories and expect such preference is helpful to improve job-resume matching. To this end, in this paper, we propose a novel matching network with preference modeled. The key idea is to explore the latent preference given the history of all interviewed candidates for a job posting and the history of all job applications for a particular talent. To be more specific, we propose a profiling memory module to learn the latent preference representation by interacting with both the job and resume sides. We then incorporate the preference into the matching framework as an end-to-end learnable neural network. Based on the real-world data from an online recruitment platform namely “Boss Zhipin”, the experimental results show that the proposed model could improve the job-resume matching performance against a series of state-of-the-art methods. In this way, we demonstrate that recruiters and talents indeed have preference and such preference can improve job-resume matching on the job market.
  • GCN-MF: Disease-gene association identification by graph convolutional networks and matrix factorization

    Han, Peng; Shang, Shuo; Yang, Peng; Liu, Yong; Zhao, Peilin; Zhou, Jiayu; Gao, Xin; Kalnis, Panos (Association for Computing Machineryacmhelp@acm.org, 2019-07-25) [Conference Paper]
    Discovering disease-gene association is a fundamental and critical biomedical task, which assists biologists and physicians to discover pathogenic mechanism of syndromes. With various clinical biomarkers measuring the similarities among genes and disease phenotypes, network-based semi-supervised learning (NSSL) has been commonly utilized by these studies to address this class-imbalanced large-scale data issue. However, most existing NSSL approaches are based on linear models and suffer from two major limitations: 1) They implicitly consider a local-structure representation for each candidate; 2) They are unable to capture nonlinear associations between diseases and genes. In this paper, we propose a new framework for disease-gene association task by combining Graph Convolutional Network (GCN) and matrix factorization, named GCN-MF. With the help of GCN, we could capture nonlinear interactions and exploit measured similarities. Moreover, we define a margin control loss function to reduce the effect of sparsity. Empirical results demonstrate that the proposed deep learning algorithm outperforms all other state-of-the-art methods on most of metrics.
  • Electrical Characterization of Solar-Blind Deep-Ultraviolet (Al0.28Ga0.72)2O3Schottky Photodetectors Grown on Silicon by Pulsed Laser Deposition

    Alfaraj, Nasir; Li, Kuang-Hui; Kang, Chun Hong; Priante, Davide; Braic, Laurentiu; Guo, Zaibing; Ng, Tien Khee; Li, Xiaohang; Ooi, Boon S. (Institute of Electrical and Electronics Engineers (IEEE), 2019-07-01) [Conference Paper]
    This study reports on (Al0.28Ga0.72)2O3-based ultraviolet-C Schottky metal-semiconductor-metal and metal-insulator-metal photodetectors with peak responsivities of 1.17 and 0.40 A/W, respectively, for an incident-light wavelength of 230 nm at 2.50 V reverse-bias. © 2019 The Author (s)
  • Wideband Self-Injection-Locked Green Tunable Laser Diode

    Shamim, Md. Hosne Mobarok; Ng, Tien Khee; Ooi, Boon S.; Khan, Mohammed Zahed Mustafa (Institute of Electrical and Electronics Engineers (IEEE), 2019-07-01) [Conference Paper]
    A wideband tunability of 6.53 nm with appreciable SMSR (> 10 dB) and linewidth (~0.1 nm) is demonstrated from a simple and low-cost tunable self-injection locked InGaN/GaN green laser based external-cavity system, for the first time.© 2019 The Author(s)
  • Rate Splitting and Common Message Decoding for MIMO C-RAN Systems

    Ahmad, Alaa Alameer; Kakar, Jaber; Dahrouj, Hayssam; Chaaban, Anas; Shen, Kaiming; Sezgin, Aydin; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim (IEEE, 2019-07-01) [Conference Paper]
    In this paper, we study the benefits of rate-splitting (RS) in multiple-input multiple-output (MIMO) cloud radio access networks (C-RAN). For this setting, we propose a stream-based transmission scheme in which user's messages are divided into a private and a common part, each of which is encoded into multiple streams. Under this stream-based strategy, we formulate a weighted sum-rate maximization problem subject to backhaul capacity and transmit power constraints. We determine the beamforming vectors of private and common streams of this non-convex optimization problem via a proposed iterative algorithm based on the fractional programming (FP) framework. Numerical results show gains of up to 27% of RS-MIMO over the baseline scheme of treating interference as noise (TIN). Particularly, at large backhaul capacities and specific antenna settings at which interference levels are maximal, rate splitting along with common message decoding is a viable option for effective interference management in MIMO C-RAN.
  • Large-System Analysis of Massive MIMO with Optimal M-MMSE Processing

    Sanguinetti, Luca; Bjornson, Emil; Kammoun, Abla (IEEE, 2019-07-01) [Conference Paper]
    We consider the uplink of a Massive MIMO network with L cells, each comprising a BS with M antennas and K single-antenna user equipments. Recently, [1] studied the asymptotic spectral efficiency of such networks with optimal multicell minimum mean-squared error (M-MMSE) processing when M and K is kept fixed. Remarkably, [1] proved that, for practical channels with spatial correlation, the spectral efficiency grows unboundedly, even with pilot contamination. In this paper, we extend the analysis from [1] to the alternative regime in which M, K with a given ratio. Tools from random matrix theory are used to compute low-complexity approximations which are proved to be asymptotically tight, but accurate for realistic system dimensions, as shown by simulations.
  • Refractive telescope design with digital correction of residual chromatic aberrations

    Zhang, Jingang; Nie, Yunfeng; Fu, Qiang; Peng, Yifan; Wang, Shuzhen (SPIE-Intl Soc Optical Eng, 2019-06-21) [Conference Paper]
    In general, optical designers employ combinations of multiple lenses with extraordinary dispersion materials to correct chromatic aberrations, which usually leads to considerable volume and weight. In this paper, a tailored design scheme that exploits state-of-the-art digital aberration correction algorithms in addition to traditional optics design is investigated. In particular, the proposed method is applied to the design of refractive telescopes by shifting the burden of correcting chromatic aberrations to software. By tailoring the point spread function in primary optical design for one specified wavelength and then enforcing multi-wavelength information transfer in a post-processing step, the uncorrected chromatic aberrations are well mitigated. Accordingly, a telescope of f-8, 1,400mm focal length, and 0.14 ◦ field of view is designed with only two lens elements. The image quality of the designed telescope is evaluated by comparing it to the equivalent designs with multiple lenses in a traditional optical design manner, which validates the effectiveness of our design scheme.

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