Mechanical Engineering
http://hdl.handle.net/10211.3/7516
2024-03-29T08:24:15ZImproving data center energy efficiency using a cyber-physical systems approach: integration of building information modeling and wireless sensor networks
http://hdl.handle.net/10211.3/198084
Improving data center energy efficiency using a cyber-physical systems approach: integration of building information modeling and wireless sensor networks
Wu, Wei; Na, Woonki; Law, Deify
The increase in data center operating costs is driving innovation to improve their energy efficiency. Previous research has investigated computational and physical control intervention strategies to alleviate the competition between energy consumption and thermal performance in data center operation. This study contributes to the body of knowledge by proposing a cyber-physical systems (CPS) approach to innovatively integrate building information modeling (BIM) and wireless sensor networks (WSN). In the proposed framework, wireless sensors are deployed strategically to monitor thermal performance parameters in response to runtime server load distribution. Sensor data are collected and contextualized in reference to the building information model that captures the geometric and functional characteristics of the data center, which will be used as inputs of continuous simulations aiming to predict real-time thermal performance of server working environment. Comparing the simulation results against historical performance data via machine learning and data mining, facility managers can quickly pinpoint thermal hot zones and actuate intervention procedures to improve energy efficiency. This BIM-WSN integration also facilitates smarter power management by capping runtime power demand within peak power capacity of data centers and alerting power outage emergencies. This paper lays out the BIM-WSN integration framework, explains the working mechanism, and discusses the feasibility of implementation in future work. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.
Defining the Future of Sustainability and Resilience in Design, Engineering and Construction, MAY 10-13, 2015, Chicago, CA, ASCE, ICSDEC
2015-01-01T00:00:00ZElectroplating of CdTe Thin Films from Cadmium Sulphate Precursor and Comparison of Layers Grown by 3-Electrode and 2-Electrode Systems
http://hdl.handle.net/10211.3/198059
Electroplating of CdTe Thin Films from Cadmium Sulphate Precursor and Comparison of Layers Grown by 3-Electrode and 2-Electrode Systems
Weerasinghe, Ajith R.; Dharmadasa, Imyhamy M.; Madugu, Mohammad L.
Electrodeposition of CdTe thin films was carried out from the late 1970s using the cadmium sulphate precursor. The solar energy group at Sheffield Hallam University has carried out a comprehensive study of CdTe thin films electroplated using cadmium sulfate, cadmium nitrate and cadmium chloride precursors, in order to select the best electrolyte. Some of these results have been published elsewhere, and this manuscript presents the summary of the results obtained on CdTe layers grown from cadmium sulphate precursor. In addition, this research program has been exploring the ways of eliminating the reference electrode, since this is a possible source of detrimental impurities, such as K+ and Ag+ for CdS/CdTe solar cells. This paper compares the results obtained from CdTe layers grown by three-electrode (3E) and two-electrode (2E) systems for their material properties and performance in CdS/CdTe devices. Thin films were characterized using a wide range of analytical techniques for their structural, morphological, optical and electrical properties. These layers have also been used in device structures; glass/FTO/CdS/CdTe/Au and CdTe from both methods have produced solar cells to date with efficiencies in the region of 5%-13%. Comprehensive work carried out to date produced comparable and superior devices fabricated from materials grown using 2E system.
From COATINGS (ISSN: 2079-6412). Vol.7(2), pp. 1-17.
2017-02-01T00:00:00ZPhonon interference in crystalline and amorphous confined nanoscopic films
http://hdl.handle.net/10211.3/187547
Phonon interference in crystalline and amorphous confined nanoscopic films
Liang, Zhi; Wilson, Thomas E.; Keblinski, Pawel
Using molecular dynamics phonon wave packet simulations, we study phonon transmission across hexagonal (h)-BN and amorphous silica (a-SiO2) nanoscopic thin films sandwiched by two crystalline leads. Due to the phonon interference effect, the frequency-dependent phonon transmission coefficient in the case of the crystalline film (Sijh-BNjAl heterostructure) exhibits a strongly oscillatory behavior. In the case of the amorphous film (Sija-SiO2jAl and Sija-SiO2jSi heterostructures), in spite of structural disorder, the phonon transmission coefficient also exhibits oscillatory behavior at low frequencies (up to 1.2 THz), with a period of oscillation consistent with the prediction from the two-beam interference equation. Above 1.2 THz, however, the phonon interference effect is greatly weakened by the diffuse scattering of higher-frequency phonons within an a-SiO2 thin film and at the two interfaces confining the a-SiO2 thin film.
The following article appeared in J. Appl. Phys. 121, 075303 (2017); doi: 10.1063/1.4976563 and may be found at http://dx.doi.org/10.1063/1.4976563.
Dielectric and piezoelectric properties of percolative three-phase piezoelectric polymer composites
http://hdl.handle.net/10211.3/187545
Dielectric and piezoelectric properties of percolative three-phase piezoelectric polymer composites
Banerjee, Sankha; Cook-Chennault, K A
Three-phase piezoelectric bulk composites were fabricated using a mix and cast method. The composites were comprised of lead zirconate titanate (PZT), aluminum (Al), and an epoxy matrix. The volume fraction of the PZT and Al was varied from 0.1 to 0.3 and 0.0 to 0.17, respectively. The influences of an electrically conductive filler (Al), polarization process (contact and Corona), and Al surface treatment, on piezoelectric and dielectric properties, were observed. The piezoelectric strain coefficient, d33, effective dielectric constant, εr, capacitance, C, and resistivity were measured and compared according to polarization process, the volume fraction of constituent phases, and Al surface treatment. The maximum values of d33 were ∼3.475 and ∼1.0 pC/N for corona and contact poled samples, respectively, for samples with volume fractions of 0.40 and 0.13 of PZT and Al (surface treated), respectively. Also, the maximum dielectric constant for the surface treated Al samples was ∼411 for volume fractions of 0.40 and 0.13 for PZT and Al, respectively. The percolation threshold was observed to occur at an aluminum volume fraction of 0.13. The composites achieved a percolated state for Al volume fractions >0.13 for both contact and corona poled samples. In addition, a comparative time study was conducted to examine the influence of surface treatment processing time of aluminum particles. The effectiveness of the surface treatment, sample morphology and composition was observed with the aid of scanning electron microscope and energy dispersive x-ray spectroscopy images. These images were correlated with piezoelectric and dielectric properties.
The following article appeared in Journal of Vacuum Science & Technology B 34, 041232 (2016); doi: 10.1116/1.4955315 and may be found at http://avs.scitation.org/doi/abs/10.1116/1.4955315