bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discrete Adjoint Sensitivities for the Real-Time Optimal Control of Large District Heating Networks During Failure Events
Authors: Pizzolato Alberto , Sciacovelli Adriano , Verda Vittorio 
Published: February 2017

In this paper, we propose an innovative approach for the real-time optimal control of district heating networks during anomalous conditions. We aim at minimizing the maximum thermal discomfort of the connected users after a pipe breakage by an integrated and centralized management of the user control-valves. Our control strategy uses a gradient-based optimizer driven by discrete adjoint sensitivities, which makes it fast and nearly insensitive to the problem dimensions.
We tested the proposed approach by simulating a set of different malfunctions in the Turin District heating network and by analyzing the building temperature field during the optimizer convergence history. Compared to the control strategy in use today, we observe that our approach flattens the temperature field and eliminates discomfort peaks, bringing a considerable increase of the minimum user temperature which ranges from a minimum of 1.8 °C to a maximum of 15.4 °C. Furthermore, our optimization strategy allows for superior results to what is achievable conventionally with an 85 % increase of the pumping head, making back-up pumping devices a non-necessary investment.
A Survey of Approaches for Fault Diagnosis in Axial Piston Pumps
Authors: Maradey Lázaro Jessica Gissella , Borrás Pinilla Carlos , Roa Prada Sebastian 
Published: February 2017

Axial piston variable displacement pumps (VDAP) are the heart of every hydraulic system, and are they commonly used in the industry for its high capacity, efficiency (volume and total), and good performance in the handling of high pressures and speeds. Faults are usually associated with wear and leakage processes, which cause significant decreases in performance.
This paper discusses about the advantages to implement a Condition-based Maintenance (CBM) and the use of techniques of fault diagnosis in axial variable displacement piston pumps (VDAP), as they are: Neural Networks (NN), Support Vector Machine (SVM) and Fuzzy Logic (FL) and other hybrid models.
The results of this investigation provide guidelines for the selection of the most suitable technique to prevent faults in VDAP in order to help reducing down time, increase productivity and competitiveness of companies that requires the use of fluid power systems by enabling the implementation of a non-intrusive fault diagnosis management system, which must be reliable, economical and easily accessible to the industry.
Development of the Reliability-Risk Modeling Framework for Ranking Conceptual Designs
Authors: D’Angelo Anthony 
Published: February 2017

A critical component of Systems Engineering (SE) is to conduct a thorough Risk Analysis. This paper introduces a novel hybrid approach to develop a Reliability-Risk modeling technique that will be able to rank Conceptual Designs as a function of Reliability. A traditional SE approach is used to identify all success modes associated with the development of a complex system. Also, the Advanced Development, Design, Integration & Evaluation, Production, and Operation & Support that make up the major phases of a Systems Engineering model will define the Holographic Reliability Design Space.
Requirements of the System under development are captured through the implementation of the Integration Definition Function Modeling (IDEF0) technique. The IDEF0 method is defined in Federal Information Processing Standard Publications (FIPS PUBS 183) [1]. Using the developed IDEF0 model allows the function of each component to be identified, the proper reliability model to be chosen, and completion of a reliability-based analysis.
Upon completion of calculating the reliability, for each criterion, the use of a Multi-Criteria Decision System (MCDS) is required to rank the conceptual designs in terms of reliability. A MCDS was developed to analyze the conflicting objects inherent during the design and integration of any complex system.
The model developed herein was used to analyze 5 Packaging Conceptual designs being considered to become part of the military Supply Chain. After completion of the analysis, the new and innovative Packaging Designs were ranked based on reliabilities associated with design, test, integration, manufacturing, and incorporation into the existing Supply Chain. The results of the rankings were then presented to the ultimate decision makers for final approval.
Non-Linear Modeling of Ocean Current Turbine Blades Under Large Deflection
Authors: Suzuki Takuya , Mahfuz Hassan 
Published: February 2017

This paper presents a non-linear modeling approach for large-scale ocean current turbine (OCT) blades. During the operation, OCT blades are subjected to a hydrodynamic load that has fluid density 800 times higher than that of air. The fluid load on OCT blades are sufficient to cause large deflection; therefore, a method that couples the blade’s deflection and the hydrodynamic load is required. For this purpose, we developed a non-linear model for turbine blades based on blade element momentum (BEM) theory. The newly developed method considers interplay between blade’s deflection and the hydrodynamic load. In addition, geometric non-linearity is also considered in the analysis, which provides a more accurate prediction of the structural response.
For validation purposes, the developed method and a set of existing National Renewable Energy Laboratory (NREL) codes were used to calculate the deflection of the OCT blade. A comparison of flap-wise and edge-wise deflections given by both methods were determined and the results showed a good correlation between the two methods. This comparison was made only for small deflection since NREL codes cannot account for large deflection.
In the next step, to investigate the effect of non-linearity, both linear and non-linear analyses were performed for a large-scale OCT blade where deflection was indeed large. In this study, we analyzed a flexible blade made of E-glass/epoxy composite. The difference in deflection was about 11% for the flexible blade since the fluid-structure interaction was significant as the blade deflection was large.
Quantifying the Linearity of the Fluid Dynamics for Noncontacting Annular Seals
Authors: Watson Cori , Paudel Wisher , Wood Houston G. , Weaver Brian K. 
Published: February 2017

Non-contacting annular seals are used in turbomachinery to reduce the leakage of working fluid. The leakage is caused by a pressure differential across the seal and is reduced through textures cut into the surface of the seal. Three common types of non-contacting annular seals are labyrinth seals, hole-pattern seals, and helical groove seals. Labyrinth seals have circumferentially cut grooves as their surface texture. Helical groove seals have continuously cut grooves following a helical path along the surface. Hole-pattern seals have holes patterned across the surface. Each surface texture causes different flow patterns and sealing mechanisms.
These non-contacting annular seals can have textures cut across the surface of the rotor, the surface of the stator, or both. The goal of this study is to determine the degree to which the flow of seals with textures on both surfaces can be viewed as the superposition of the flow for a seal with the rotor surface textured and a smooth stator combined with the flow for a seal with the stator surface textured and a smooth rotor. To accomplish this goal, simulations were run in ANSYS CFX for each seal type and configuration for a variety of rotor speeds and pressure ratios to compare superimposed solutions to standard 3D solutions.
The ability to superimpose solutions to a differential equation — and therefore a fluid dynamics system — is determined by the linearity of the differential equation. By comparing the superimposed solution with the standard solution, this study will quantify the degree of non-linearity in the system. The degree of divergence away from linearity will be compared against the rotor speed and pressure ratio, which are proportional to the Reynold’s number. The Navier-Stokes equation contains a non-linear inertial force term. The relative significance of the inertia forces is predicted by the Reynold’s number so a strong correlation is expected between the Reynold’s number and the agreement between the flow found by superposition and the flow found by the actual seal model.
The other application of this research is to the computational modeling of annular seals. Annular seals can be computationally demanding and time consuming to model. This is especially true for seals with texture on both surfaces where millions of finite volumes may be needed in the simulation in order to find a convergent solution. For rotor speeds with strong agreement between the actual flow and the superimposed flow, superposition can be applied to perform faster simulations of seals with texture on both surfaces.
Optimal Sinusoidal Cellular Structures for Energy Absorption
Authors: Jiang Yunyao , Li Yaning 
Published: February 2017

In this investigation, the elastic mechanical properties of the sinusoidal cellular structures were first explored via analytical models. The analytical analysis showed that for linear elastic materials, the amplitude-to-wavelength ratio of the sinusoidal structures is a key geometric parameter to determine the deformation mechanisms. To further evaluate the influences of the geometric nonlinearity, a set of finite element simulations were performed for sinusoidal structures with the same density but various amplitude-to-wavelength ratios. It was found that the optimal amplitude-to-wavelength ratio for the maximum energy absorption corresponds to the transition between symmetric to asymmetric deformation mechanisms.
Selected designs were fabricated via a 3D printer (Objet, Connex 260). Mechanical experiments under quasi-static uniaxial compression and cyclic compression were performed on the 3D printed specimens. Finite element (FE) simulations with both linear elastic and nonlinear hyperelastic material models were performed and compared with the experiments. The 3D-printed sinusoidal structures were shown to be re-configurable under cyclic loading.
Electro-Mechanical Impedance Measurements in an Imitated Low Earth Orbit Radiation Environment
Authors: Anderson Mary L. , Daniel Joshua D. , Zagrai Andrei N. , Westpfahl David J. 
Published: February 2017

Piezoelectric sensors are used in many structural health monitoring (SHM) methods to interrogate the condition of the structure to which the sensors are affixed or imbedded. Among SHM methods utilizing thin wafer piezoelectric sensors (PWAS), electro-mechanical impedance monitoring is seen as a promising approach to assess structural condition in the vicinity of a sensor. Using the converse and direct piezoelectric effects, this health monitoring method utilizes mechanical actuation and electric voltage to determine the impedance signature of the structure. If there is damage to the structure, there will be a change in the impedance signature. It is important to discern between actual damage and environmental effects on the piezoelectric ceramic sensors and the structure. If structural health monitoring is to be implemented in space structures on orbit, it is imperative to determine the effects of the extreme space environment on piezoelectric sensors and the structures to which they are affixed. The space environment comprises extreme temperatures, vacuum, atomic oxygen, microgravity, micro-meteoroids and debris, and significant amounts of radiation. Radiation in space comes from three sources: solar events, background cosmic radiation, and trapped particles in the Van Allen Belts. Radiation exposure to structures on orbit will vary significantly depending on the duration of the flight and the altitude and inclination of the orbit. In this contribution, the effect of gamma radiation on piezoelectric ceramic sensors and space grade aluminum is investigated for equivalent gamma radiation exposure to 3-months, six-months, and 1-year on Low Earth Orbit (LEO).
An experiment was conducted at White Sands Missile Range, Gamma Radiation Facility using Cobalt-60 as the source of radiation. A free PWAS and a PWAS bonded to a small aluminum beam were exposed to increasing levels of gamma radiation. Impedance data were collected for both sensors after each radiation exposure. The total radiation absorbed dose was 200 kRad (Si) by the end of the experiment. The results show that piezoelectric ceramic material is affected by gamma radiation. Over the course of increasing exposure levels to Cobalt-60, the impedance frequency of the free sensor increased with each absorbed dose. The impedance measurements of the sensor bonded to the aluminum beam reflects structural and sensor’s impedance. The data for this sensor show an increase in impedance amplitude with each level of absorbed dose. The mechanism at work in these impedance changes is suggested and future experimental work is identified. A survey of previous results of radiation exposure of piezoelectric ceramic sensors and aluminum alloys is presented and are compared to previous studies.
Role of Particle Size to Channel Thickness Ratio on Performance of Nanofluids in Micro-Channels
Authors: Smith Sonya T. , Mosleh Mohsen , Shirvani Khosro A. 
Published: February 2017

Experimental and numerical investigations were conducted to explore the viability of single-phase nanofluids for microchannel cooling. The experiments were conducted with water/ethylene glycol-based nanofluids to investigate the thermal conductivity enhancement. In the numerical analysis, micro-channels ranged in width from 40 μm to 90 μm with the fixed channel height were considered.
Thermal conductivity enhancements of nearly 14% at particle concentration of 0.1% by weight was observed in the experiments. Numerical predictions suggest that design variables (particle size and channel aspect ratio) and thermo-physical properties of the nanofluid have a significant effect on the thermal performance of micro-channel heat sinks. It was shown that at fixed Reynold number, reduction of channel width reduces the hydraulic pressure loss and the heat transfer coefficient, and utilizing nanofluids increases these parameters.
Transient Characterization of Data Center Racks
Authors: Fulpagare Yogesh , Joshi Yogendra , Bhargav Atul 
Published: February 2017

The increased computational and storage demand has increased the heat dissipation of servers in data centers. The flow inside the data center is highly dynamic due to various parameters such as server workload, server fan speed, tile porosity, Computer Room Air Conditioning (CRAC) air flowrates, CRAC supply & return air temperatures and data center cold & hot aisle arrangements. Data center facility level transient CFD analysis was reported in recent literature which needs weeks to accomplish the computation. Hence, such facility level simulations are difficult to achieve with good accuracy. The main contributions of this paper are transient experiments, transient CFD model & transient effects on thermal and flow field due to variation in server load of server rack inside the raised floor plenum data center.
In the current study we have developed a transient CFD model of three racks in a raised floor plenum data center room with cold and hot aisle containment based on experiments. The middle 42U (1U = 4.45 cm) rack houses four server simulators each having height of 10U. The flow tiles supply the cold air as inlet with average velocity of 1.53 m/s at 17°C. All the rack servers were modelled with 75% porosity and estimated thermal mass Each server simulator was assigned a total heat dissipation of 2500 W, with a total heat load of 10 kW per rack. The effect on rack inlet and outlet air temperatures were monitored by providing server heat loads as step & ramp inputs to the middle simulator rack. The results show that the rack level transient effects are significant and cannot be ignored.
The Long-Term Viability of Concentrated Photovoltaic Systems in the Southwestern US
Authors: Sahm Aaron , Burnham Laurie , Boehm Robert , Betemedhin Adam , Wood Gary 
Published: February 2017

Total lifetime costs of photovoltaic (PV) systems are important determinants of profitability. But such costs are not always accurately measured and compared against fluctuating electricity costs, which can be an important contributor to long-term profitability. In this paper, we consider the economics of concentrated photovoltaics (CPV), which offer significantly higher efficiency and greater energy production over traditional fixed flat-plate PV installations in high-irradiance regions, but are perceived to be risky investments.
Working with two models, one a simple annual model that uses only direct normal solar insolation; the other a more complex hourly model that uses direct normal solar insolation, ambient temperature, and wind speed to predict energy yield, we calculated the energy production and corresponding revenue generation for a 28 kW CPV unit and a comparable single-axis tracker field in Nevada. Our resulting cost matrix shows how much revenue a CPV system can reasonably be expected to generate under different pricing schemes and time periods. While the values vary depending on the assumptions made, the matrix provides an index of profitability, enabling prospective buyers to compare the costs of purchasing, installing and maintaining a system against likely revenue.
As a result of our calculations, we anticipate that CPV systems will still be viable in high flux areas because they offer the promise of profitability now and continued or increased profitability as cell costs decrease and/or overall efficiency increases. Nonetheless, other factors, such as long-term reliability and O&M costs, must be addressed if CPV is to compete with other simpler technologies, such as single-axis PV trackers, which have lower upfront costs and are therefore becoming more attractive to potential customers.
Microfluidic Synthesis of Polymer Ionic Liquid Gel Beads for Energy Harvesting Applications
Authors: Kudtarkar Kaushik A. , Smith Thomas W. , Iglesias Patricia , Schertzer Michael J. 
Published: February 2017

In the operation of many common devices and processes, more than 60% of consumed energy is wasted in many common processes. These loses come in many forms including heat, friction, and vibration. Energy harvesters are devices that can recapture some of this waste energy and convert it into electrical energy. This work will focus on electrostatic energy harvesting devices that recapture vibrational energy. Electrostatic energy harvesters recapture mechanical energy when a conductive mass translates or deforms in an electric field. Polymer ionic liquid gel beads may serve as a useful replacement for fluid droplets in electrostatic energy harvesters.
This work uses a recently developed method for reliable synthesis of polymer gel beads. These beads are synthesized using a micro-reactor, which generates monomeric droplets in a silicon oil carrier fluid. The monomer solution also contains a photoinitiator and cross linker, which enables the monomer to polymerize when exposed to UV light. The present work demonstrates a method to rapidly synthesize uniform beads with a variety of chemical compositions. These chemical compositions can be used to tune the electromechanical properties of the beads to improve performance in applications such as energy harvesting devices.
Metamaterial Application in Stress Wave Mitigation Generated by Impulsive Force
Authors: Rodrigues Gustavo Simão , Weber Hans Ingo 
Published: February 2017

The idea to use metamaterials to mitigate mechanical waves is recent and constitutes a technology under development. These materials have a special design, presenting characteristics not found in nature. The interesting feature is a negative effective mass density. This property is achieved by creating in the structure masses linked by springs which act as internal resonators and, as a result, it is observed that metamaterials act as mechanical filters, preventing or reducing the intensity of propagation of mechanical waves that travel in the structure, when the frequency of propagation is close to the resonance frequencies of the internal resonators.
An internal combustion generates a blast wave which acts on a structure as an impulsive effort. This is a basic phenomenon in the shooting of an armament leading to this research that target to investigate the possible application of metamaterials to improve recoil mechanism technology. A recoil mechanism moderates the firing loads on the supporting structure by prolonging the time of resistance to the propellant gas forces. Depending on application of the armament, recoil can be very undesirable. Firstly, carriage mount where the armament is fixed will suffer premature wear. Secondly and more critical, if the armament is mounted onto a vehicle, its dynamics during shooting is completely affected and an accident can be caused when shooting occurs during a critical situation, like a curvilinear path for example.
It is intended to use numerical simulations and experimental validation to verify the behavior of the designed metamaterial under a controlled impulse input. Finite Element Method (FEM) is used to simulate wave propagation through a common material and then through a special designed metamaterial to evaluate how this kind of pulse will be affected by internal resonators. After the simulations, a prototype adequate to validate numerical results will be investigated on a test bench. In a further development the impulse input will be adapted to real measured blast efforts.