bluuebunny/crossref_metadata_2025 huggingface dataset:
Compressed Sensing Techniques for Ultrasonic Imaging of Cargo Containers
Authors: Martínez Lorenzo José Á. , Álvarez López Yuri
Published: February 2017

This contribution presents a compressed sensing (CS)-based ultrasonic imaging system for fast, low-cost inspection of metallic cargo containers. The idea is to detect the footprint of metallic objects within the container that can be used to conceal smuggling goods. This ultrasonic technology can complement currently deployed X-ray-based radiographic systems and millimeter-wave scanners, thus increasing the probability of detection.

The proposed hardware consists of an array of acoustic transceivers that is attached to the metallic structure of the metallic cargo container to create a guided acoustic wave. Variations in the thickness of the metallic structure create reflections that can be located by backpropagating the measured reflected wave.

Aiming to reduce the number of acoustic transceivers, this contribution evaluates the feasibility of applying CS techniques in the proposed acoustic imaging system. It has been observed that in the majority of the cases, the acoustic images retrieved by the cargo inspection system are sparse, that is, only those image pixels corresponding to discontinuities in the metallic plate (due to gaps, joints, placement of a metallic object on it) are different from zero. Thus, sparsity condition, which is one of the CS requirements, is satisfied for this particular application.

A simulation-based example resembling a real case of cargo inspection is considered for validation purposes. A comparison between standard backpropagation and CS for different number of samples is presented, proving that CS is able to recover the acoustic image with as few as 10% of the samples required by Nyquist sampling rate.
Study of Energy Harvesting Performance of Wet-Stretched PVDF Nanofibers
Authors: Najjar Raghid , Luo Yi , Hu Xiao , Beachley Vince , Xue Wei
Published: February 2017

An average human body produces a large amount of energy throughout the day. A significant portion of this energy is utilized as mechanical energy. Body movement such as footfalls and arm swings can produce enough energy to power portable electronics using mechanical-to-electrical energy harvesters. These devices should be small, light, portable, and flexible. Polyvinylidene fluoride (PVDF) has shown a high biocompatibility and is a suitable candidate for energy harvesting applications. Moreover, PVDF can be produced in large quantities while still maintaining a low cost. Electrospinning is a common process used to prepare PVDF nanofibers. Here we introduce a novel technique called wet-stretched electrospinning to further increase the amount of energy generated by the PVDF devices. Our initial results show that the wet-stretched nanofibers outperform the regular PVDF nanofibers by up to 12 times under similar conditions. These promising results suggest that the proposed method has great potential to be utilized as a major improvement from the traditional electrospinning process of PVDF. These findings are significant and are especially pertinent to the field of energy harvesters designed for powering medical devices or wearable systems.
3D Printing for Manufacturing Antique and Modern Musical Instrument Parts
Authors: Celentano Frank , May Nicholas , Simoneau Edward , DiPasquale Richard , Shahbazi Zahra , Shahbazmohamadi Sina
Published: February 2017

Professional musicians today often invest in obtaining antique or vintage instruments. These pieces can be used as collector items or more practically, as performance instruments to give a unique sound of a past music era. Unfortunately, these relics are rare, fragile, and particularly expensive to obtain for a modern day musician. The opportunity to reproduce the sound of an antique instrument through the use of additive manufacturing (3D printing) can make this desired product significantly more affordable. 3D printing allows for duplication of unique parts in a low cost and environmentally friendly method, due to its minimal material waste. Additionally, it allows complex geometries to be created without the limitations of other manufacturing techniques. This study focuses on the primary differences, particularly sound quality and comfort, between saxophone mouthpieces that have been 3D printed and those produced by more traditional methods. Saxophone mouthpieces are commonly derived from a milled blank of either hard rubber, ebonite or brass. Although 3D printers can produce a design with the same or similar materials, they are typically created in a layered pattern. This can potentially affect the porosity and surface of a mouthpiece, ultimately affecting player comfort and sound quality. To evaluate this, acoustic tests will be performed. This will involve both traditionally manufactured mouthpieces and 3D prints of the same geometry created from x-ray scans obtained using a ZEISS Xradia Versa 510. The scans are two dimensional images which go through processes of reconstruction and segmentation, which is the process of assigning material to voxels. The result is a point cloud model, which can be used for 3D printing. High quality audio recordings of each mouthpiece will be obtained and a sound analysis will be performed. The focus of this analysis is to determine what qualities of the sound are changed by the manufacturing method and how true the sound of a 3D printed mouthpiece is to its milled counterpart. Additive manufacturing can lead to more inconsistent products of the original design due to the accuracy, repeatability and resolution of the printer, as well as the layer thickness. In order for additive manufacturing to be a common practice of mouthpiece manufacturing, the printer quality must be tested for its precision to an original model. The quality of a 3D print can also have effects on the comfort of the player. Lower quality 3D prints have an inherent roughness which can cause discomfort and difficulty for the musician. This research will determine the effects of manufacturing method on the sound quality and overall comfort of a mouthpiece. In addition, we will evaluate the validity of additive manufacturing as a method of producing mouthpieces.
A Fringe Signal Processing Method With Multi-Sample Zero-Crossing Detection Based on DSP and its Application in Absolute Gravimeters
Authors: Qian Jin , Wu Kang , Wang Lijun
Published: February 2017

The absolute gravitation acceleration (g) is generally measured by observation of a free-falling test mass in a vacuum chamber based on laser interference. Usually the free-falling object trajectory is obtained by timing the zero-crossings of the interference fringe signal. A traditional way to time the zero-crossings is electronic counting method, of which the resolution is limited in principle. In this paper, a fringe signal processing method with multi-sample zero-crossing detection based on Digital Signal Processor (DSP) is proposed and realized for the application in absolute gravimeters. The principle and design of the fringe signal processing method are introduced. The measuring precision is evaluated both theoretically and from numerical software simulations with MATLAB®, and verified by hardware simulated free-falling experiments. The results show that the absolute error of the gravity acceleration measurement introduced by the fringe signal processing method is less than 0.5 μGal (1 μGal = 1×10−8 m/s2), and the impact on the standard deviation is about 2 μGal. This method can effectively reduce the systematic error of the traditional electronic counting method, and satisfy the requirements for precision and portability, especially for field ready absolute gravimeters.
The Numerical Simulation of Turbulent Flow in Semi-Closed Rotor-Stator Cavity
Authors: Luo Guohu , Wang Shengde , Shen Hong , Yao Zhenqiang
Published: February 2017

The present work numerically considered the turbulent flow in a semi-closed rotor-stator cavity with a superimposed throughflow based on Reynolds Stress Model (RSM). The mean flow structure and turbulent field in the semi-closed cavity (SC) were identified by comparison with the flow in open cavity (OC) and closed cavity (CC). Then the effects of rotation Reynolds number, ranging from 1 × 106 to 4 × 106, on the flow in SC were investigated. The superimposed flow noticeably decreases the tangential velocity, resulting that the pressure difference between central hub and periphery in SC is greater than the OC but less than the CC. The flow in SC belongs to Stewartson type in the region between inlet and outlet, but to Bachelor type between outlet and periphery. Around the outlets, the flow is greatly affected, especially for turbulent field, where the turbulence intensities maintain at higher levels outside the two boundary layers. With the increase of Reynolds number, the tangential velocity goes up, resulted the attenuation of jet impinging effects, the shrinking of affected zones by outlets and the enlargement of pressure difference. Moreover, with the Bödewadt layer moving toward the central hub, the turbulence intensities increase inside two boundary layers but decrease outside them. Consequently, the flow is transited to Stewartson and then Batchelor type.
Deformation of Stenotic Blood Vessel Model Made From Poly (Vinyl Alcohol) Hydrogel by Hydrostatic Pressure
Authors: Shimizu Yasutomo , Liu Lei , Kosukegawa Hiroyuki , Funamoto Kenichi , Hayase Toshiyuki , Nakayama Toshio , Ohta Makoto
Published: February 2017

Vascular plaque deformation reduces blood flow, increases arterial embolism risk, and may lead to ischemic stroke. Plaque stiffness varies widely and is an important factor influencing both plaque and parent artery deformation. These geometric changes affect local hemodynamics, which impact plaque initiation influencing disease progression. However, most previous studies used non-elastic stenotic vessel models. For more realistic analysis, we constructed a stenosis model comprising an elastic poly (vinyl alcohol) hydrogel (PVA-H) parent artery and plaque of variable stiffness. Our previous study using this flexible model demonstrated substantial effects of hydrostatic pressure. Here ultrasonography was conducted under changing hydrostatic pressure to measure geometric changes at the narrowest cross section. PVA-H specimens were constructed with the stiffness of a hard lipid core, smooth muscle, and plaque, as estimated by tensile tests using 5, 12, and 15 wt% PVA, respectively. The change in cross-sectional aspect ratio (height/face length) at the narrowest site is largest (∼1.3) for the 5 wt% PVA-H plaque and smallest (∼1.2) for the 12 wt% PVA-H plaque. Stenotic artery deformation depends on both artery and plaque elasticity. Hydrostatic pressure has a substantial effect on both vessel and plaque geometries, which markedly alter blood flow.
Nonlinear Characteristics of a Sudden Expansion Followed by Sudden Contraction Channel
Authors: Liu Keyan , Yang Mo , Zhang Yuwen , Shen Chunyun
Published: February 2017

The flow and heat transfer in a sudden expansion followed by sudden contraction channel are widely applied in industry, and it is also a classic problem for theoretical study. In this article, the SIMPLE algorithm with QUICK scheme were used to study the flow and heat transfer in a sudden expansion followed by sudden contraction channel. The nonlinear characteristics and temperature field were investigated for various Reynolds number and geometrical dimension. The results show that the temperature field evolves from symmetric to asymmetric state with the increasing Re. When Re ≥ Rec, the flow loses stability and from symmetric to asymmetric via a symmetry-breaking bifurcation; when the Reynolds number continues to increase, the fluid flow and heat transfer oscillation. The nonlinear characteristics of flow and heat transfer within the channel is further analyzed.
Active Control of Rear Sub-Frame Vibration in Rear and All-Wheel Drive Vehicles
Authors: Deng J. , Kashani A. R.
Published: February 2017

Feedback control of the rear sub-frame structure is used to abate its gear mesh induced vibration. The goal of the active control is to absorb vibration at a location close to the perturbation source, i.e., the rear differential. Proof mass actuators (PMAs) are used in this active vibration control application. A tuned absorption-based as well as a linear quadratic active vibration control schemes, each with its own advantages and disadvantages, were developed for this application. Following to the synthesis and numerical simulation of the two active vibration control strategies, they were first evaluated on a test structure in the laboratory.

Following the laboratory evaluation, one of the active vibration control strategies was implemented on an all-wheel drive vehicle. Two small PMAs, mounted on the rear sub-frame of the vehicle, were used as the active elements in this vibration control application. An accelerometer placed next to each actuator was used as the feedback sensor.

The effectiveness of active vibration control in absorbing the shaker induced vibration of the sub-frame was successfully demonstrated. In addition, rolling dynamometer tests showed effective vibration reduction of rear differential induced vibration of the sub-frame. As expected, lowering the sub-frame vibration resulted in lower vibration and noise in the cabin.
Design of a Stewart-Gough Platform for Engineering Material Characterization
Authors: Fry Sean T. , Turner Cameron J.
Published: February 2017

Stewart-Gough platforms have been used as the basis for multiaxial test machines in multiple applications. Their stiffness coupled with the ability to simultaneously create a combined loading (tensile/bending/twisting) of any design enables them to excite material parameters in any conceivable coupling. For engineered materials, whose properties are often nonlinear and nonisotropic, such loadings are necessary to understand the as-built material parameters inherent within these designed systems. However, the design of a Stewart-Gough is nontrivial as the presence of singular configurations is poorly understood. In the proximity of these singular configurations, precision control of the loading applied by the system is difficult to control due to large gradients in the forces generated. This work uses a combination of simulation and surrogate modeling to establish a “map” of the singular configurations of the Stewart-Gough platform. As a result, a “home” location where the system provides a zero loading upon a specimen is found so as to maximize distance from a singular configuration, and a greater understanding of the nature of singularities in parallel robotics structures is obtained.
Heat Transfer Behavior of the Boundary Layer Near Surfaces in Annular Flow of High Capacity Canned Motor Pump
Authors: Wang Shengde , Luo Guohu , Shen Hong , Yao Zhenqiang
Published: February 2017

As significant fluid machinery, canned motor pumps are widely applied in industrial field. The typical characteristic of canned motor pump is that the fluid comes into the narrow gap and affects the performance of canned motor. The coolant flow in the narrow annular gap between rotor and stator cans belongs to Taylor-Couette-Poiseuille flow which has been investigated for a long time while the thermal design is a key function of internal narrow gap annular flow of canned motor. However, the temperature distribution prediction of canned motor deviates from the experiments, especially in the high-capacity canned motor due to the large shear rate of fluid and eddy-current loss of motor’s can. According to the researcher’s work, the significant work lies in the heat transfer coefficient that different researchers give various numerical prediction and experimental measurement. It brings big challenge in thermal design of high-capacity canned motor pump. In this paper, the author focuses on the reason why the heat transfer coefficient is remarkably lower than that other’s forecast. In this paper, the heat transfer behavior of the boundary layer near surfaces in the annular flow is investigated by using the commercial fluid dynamic (CFD) method. Firstly, the Naiver-Stocks (N-S) equations and energy conservation equation are employed for modeling the flow and heat transfer behavior, and the k-ω turbulent model is used for solving the flow control equations. Secondly, the fluid domain is described by a simplified geometrical model: two concentric cylinders with finite gap length. Thirdly, numerical approach is used to analyze the subject with tools of Solidworks, ICEM CFD and Ansys Fluent. Two parameters are analyzed in the research, namely the rotating speed and the wall heat flux, without considering the fluid viscous dissipation and thermal contact resistance. Numerical simulation results indicate that Taylor vortex exists in the flow regime, and the temperature distribution is affected by both the rotating speed and the wall heat flux, named thermal barrier effect under large heat flux condition. The thermal barrier effect lies in that the temperature gradient of interface decreases compared to the peak value of temperature gradient near the surface, so that the heat transfer coefficient is reduced remarkably. This effect leads to the temperature prediction deviates from the experiment measurement.
Optimization and Stiffness Performance Analysis for 3-DOF Spatial and Spherical Parallel Mechanisms
Authors: Zhang Dan , Wei Bin
Published: February 2017

This paper focuses on the optimization and stiffness performance analysis of three kinds of three degrees of freedom (DOF) spatial and spherical parallel mechanisms. Firstly, the kinematic model and the Jacobian matrix for the 3-DOF parallel mechanisms are established and solved, and the objective functions for stiffness and workspace optimization are formed; secondly, by using stiffness and workspace as objective functions and applying different multi-objective optimization methods, the general procedure for the multi-objective optimization problem for the parallel mechanisms are established. Finally, the correspondence and the differences between several stiffness models are compared and illustrated.
Passive Control and Enhancement of Low Reynolds Number Slot Jets Through the Use of Tabs and Chevrons
Authors: Sexton Andrew , Punch Jeff , Jeffers Nicholas , Stafford Jason
Published: February 2017

Optical networks are a critical element of contemporary communications infrastructure, due to their efficacy in transmitting high-speed data over large distances. Photonic integrated circuits (PICs) offer compelling advantages in terms of performance and miniaturization, but the increase in power density of these components, coupled with shrinking packaging restrictions, presents a significant thermal management challenge. This has driven the need for the integration of liquid-based microfluidic cooling artefacts into next generation PIC packages. Liquid micro-jets are emerging as candidate primary or secondary heat exchangers for such packages, however the thermal behavior of confined, low Reynolds number liquid slot jets is not comprehensively understood. This investigation utilized a hot foil technique to experimentally determine the influence of implementing jet outlet modifications — in the form of tabs and chevrons — as techniques for passive control and enhancement of single-phase convective heat transfer. The investigation was carried out for slot jets in the laminar flow regime, with a Reynolds number range, based on the conventional slot jet hydraulic diameter, of 100 to 500. The investigation was carried out with a slot jet aspect ratio of 4, and a fixed confinement height to hydraulic diameter ratio (H/Dh) of 1. It was found that all outlet modifications increased local and area-averaged Nusselt number compared to a conventional slot jet. Modifications to the major axis (or long edge) of the slot jet were most effective, achieving increases in area-averaged Nusselt number of up to 61%. It was also determined that the location and magnitude of Nusselt number peaks within the slot jet stagnation region, could be passively controlled and enhanced through the application of outlet tabs at varying locations, allowing for more flexible targeted hotspot cooling. Therefore, it was concluded that enhancements in an integrated microjet cooling artefact can be achieved through passive geometry devices, without compromising the stringent packaging restrictions of such systems, such as confinement height and nozzle geometry.
Multistability and Modal Interactions in Periodic 2D Coupled Pendulums Array
Authors: Bitar Diala , Kacem Najib , Bouhaddi Noureddine
Published: February 2017

The collective dynamics of an array of periodic two dimensional (2D) coupled pendulums under harmonic horizontal base excitation is investigated. The coupled differential equations governing the nonlinear vibrations of the considered system have been solved using an analytical-numerical solving procedure, based on the multiple scales method coupled with standing wave decomposition. It allows the identification of complex and wide variety of nonlinear phenomenon exhibited by the periodic nonlinear structure. The frequency responses for several coupled pendulums were calculated in order to analyze the stability, the modal interactions and the bifurcation topologies resulting from the collective dynamics of the coupled pendulums, while highlighting the large number of multimodal solutions for a small number of coupled pendulums. The complexity and the multivaludness of the responses were illustrated by a study of basins of attraction which display the large distribution of the multi-mode branches.
Analytical Investigation on the Rotational Speed Dependence of the Rotordynamic Fluid Force: The Case of Concentric Circular Whirl in the Annular Plain Seal
Authors: Ikemoto Atsushi , Sakamoto Kazukiyo , Inoue Tsuyoshi , Uchiumi Masaharu
Published: February 2017

Rotordynamic (RD) fluid forces of various kinds of seals has been investigated and reported by Childs [1], Iwatsusbo [2][3] and so on, because it has significant influence on the stability of rotating machinery. Those studies were carried out at lower speeds than the actual machines because of various restrictions such as the limitations of the experimental unit. Then, extrapolation approximations using the obtained results were used to predict the RD fluid force of the actual machines. However, when the rotor vibration is analyzed for the high speed rotating shaft such as a rocket turbopump, a more accurate evaluation of the rotational speed dependence of the derived RD fluid force is desired.

In this study, the rotational speed dependence of RD fluid forces in the case of the concentric circular whirl in the annular plain seal is investigated. As a result, the characteristics of these fluid forces vary with the rotational speed significantly. In addition, the strong dependencies of RD fluid force coefficients calculated from these fluid forces on the rotational speed are observed. It is revealed that the changes of the RD fluid force coefficients to rotational speed were modeled by using the quadratic function.
Tunable Bandpass Filter Based on Electrothermally and Electrostatically Actuated MEMS Arch Resonator
Authors: Hajjaj Amal Z. , Al Hafiz Md Abdullah , Younis Mohammad I.
Published: February 2017

This paper demonstrates experimentally a wide bandpass filter based on an electrothermally tuned single MEMS arch resonator operated in air. The in-plane resonator is fabricated from a silicon-on-insulator wafer with a deliberate curvature to form an arch shape. A DC voltage is applied across the anchors to pass current through the resonator to induce heat and modulate its stiffness, and hence its resonance frequencies. We show that the first resonance frequency increases up to twice of the initial value while the third resonance frequency decreases until getting very close to the first resonance frequency. This leads to the phenomenon of veering, near crossing, where both modes exchange roles. Hence, the first resonance frequency becomes insensitive to axial forces and thermal actuation whereas the third resonance natural frequency becomes very sensitive. We demonstrate an exploitation of the veering phenomenon to realize a bandpass filter, where the first and third resonance modes are excited electrostatically simultaneously to achieve a bandpass. We demonstrate also that by driving both modes nonlinearly near the veering regime, so that the first mode shows softening behavior and the third mode shows hardening behavior, sudden jumps in the response from both modes are induced leading to sharp roll off from the bandpass to the stop band. We show a flat, wide, and tunable bandwidth and center frequency by controlling the electrothermal actuation voltage.
Integrated Process for Textile Cotton Waste (TCW) Valorization: Waste-to-Energy and Wastewater Decontamination
Authors: Ribeiro A. , Vilarinho C. , Araújo J. , Carvalho J.
Published: February 2017

The increasing of world population, industrialization and global consuming, existing market products existed in the along with diversification of raw materials, are responsible for an exponential increase of wastes. This scenario represents loss of resources and ultimately causes air, soils and water pollution. Therefore, proper waste management is currently one of the major challenges faced by modern societies.

Textile industries represents, in Portugal, almost 10% of total productive transforming sector and 19% of total employments in the sector composed by almost 7.000 companies. One of the main environmental problems of textile industries is the production of significant quantities of wastes from its different processing steps. According to the Portuguese Institute of Statistics (INE) these industries produce almost 500.000 tons of wastes each year, with the textile cotton waste (TCW) being the most expressive. It was estimated that 4.000 tons of TCW are produced each year in Portugal.

In this work an integrated TCW valorisation procedure was evaluated, firstly by its thermal and energetic valorisation with slow pyrolysis followed by the utilization of biochar by-product, in lead and chromium synthetic wastewater decontamination.

Pyrolysis experiments were conducted in a small scale rotating pyrolysis reactor with 0.1 m3 of total capacity. Results of pyrolysis experiments showed the formation of 0,241 m3 of biogas for each kilogram of TCW. Results also demonstrated that the biogas is mostly composed by hydrogen (22%), methane (14 %), carbon monoxide (20%) and carbon dioxide (12%), which represents a total high calorific value of 12.3 MJ/Nm3.

Regarding biochar, results of elemental analysis demonstrated a high percentage of carbon driving its use as low cost adsorbent. Adsorption experiments were conducted with lead and chromium synthetic wastewaters (25, 50 and 100 mg L−1) in batch vessels with controlled pH. It was evaluated the behaviour of adsorption capacity and removal rate of each metal during 120 minutes of contact time using 5, 10 and 50 g L−1 of adsorbent dosage. Results indicated high affinity of adsorbent with each tested metal with 78% of removal rate in chromium and 95% in lead experiments. This suggests that biochar from TCW pyrolysis may be appropriated to wastewaters treatment, with high contents of heavy metals and it can be an effective alternative to activated carbon.
Adsorption-Controlled Thermal Switch Using Nonequilibrium Molecular Dynamics Simulation
Authors: Avanessian Tadeh , Hwang Gisuk
Published: February 2017

A thermal switch is a system to control the heat transfer “on/off” for the desired functionalities, and this serves as a basic building block to design advanced thermal management systems in various applications including electronic packaging, waste heat recovery, cryogenic cooling, and new applications such as thermal computers. The existing thermal switches employ the macroscale mechanical-based, relatively slow transient “on/off” switch mechanisms, which may be challenging to provide solutions for micro/nanoscale applications. In this study, a fast and efficient thermal switch mechanism without having extra mechanical controlling system is demonstrated using gas-filled, heterogeneous nanogaps with asymmetric surface interactions in Knudsen regime. Argon gas atoms confined in metal-based solid surfaces are employed to predict the degree of thermal switch, S. Non-equilibrium molecular dynamics simulation is used to create the temperature gradient over the two nanogaps, and the maximum degree of thermal switch is Smax ∼ 13, which results from the difference in adsorption-controlled thermal accommodation coefficient (TAC) and pressure between the two sides of the gaps.
A Vibration Compensation Method for Absolute Gravimeters
Authors: Wang Guan , Hu Hua , Wu Kang , Wang Lijun
Published: February 2017

The laser interferometer is used to track the falling object in a freefall absolute gravimeter, which could be disturbed by the vibration from the ground. Thus, the vibration compensation method is often used to reduce the influence of the vibration. Typically, a sensor (broadband seismometer) is used to record the vibration. But the measured ‘vibration’ Nm(t) does not equal the motion of the reference corner cube N(t). Because there exists a transfer function G(s) making Nm(s) = G(s)N(s). Traditionally, G(s) is assumed to be equal to the transfer function of the sensor, which can be achieved with the help of other equipment. But the assumption is not reasonable and the process of calculating the transfer function is complicated. A novel vibration compensation method without any other equipment is proposed in this paper. In this method, G(s) is simplified to estimate N(t) using N′(t) = ANm(t − τ), which is used for compensation. The gain A and delay τ can be obtained by analysis of the data acquired by the absolute gravimeter. The experiments are conducted with the homemade absolute gravimeter T-1 and repeated for 75 times. The standard deviation of the uncompensated results is 3276 μGal (1 μGal = 1 × 10−8 m/s2), while that of the compensated results is 167 μGal. The compensation method not only achieves a reduction by nearly a factor of 20, but also can be simply used without any other equipment. The results indicate that the method basically meets the demands of absolute gravimeters. In the future, it may be applied to dynamic absolute gravity measurement and take the place of vibration isolators.
Robustness Analysis of the Collective Dynamics of Nonlinear Periodic Structures Under Parametric Uncertainty
Authors: Chikhaoui Khaoula , Bitar Diala , Kacem Najib , Bouhaddi Noureddine
Published: February 2017

In order to ensure more realistic design of nonlinear periodic structures, the collective dynamics of a coupled pendulums system is investigated under parametric uncertainties. A generic discrete analytical model combining the multiple scales method, the perturbation theory and a standing-wave decomposition is proposed and adapted to the presence of uncertainties. These uncertainties are taken into account through a probabilistic modeling implying that the stochastic parameters vary according to random variables of chosen probability density functions. The proposed model leads to a set of coupled complex algebraic equations written according to the number and positions of the uncertainties in the structure and numerically solved using the time integration Runge-Kutta method. The uncertainty propagation through the established model is finally ensured using the Latin Hypercube Sampling method. The analysis of the dispersion, in term of variability of the frequency and amplitude intervals of the multistability domain shows the effects of uncertainties on the stability and nonlinearity of a three coupled pendulums structure. The nonlinear aspect is strengthened, the multistability domain is wider, more stable branches are obtained and thus the multimode solutions are enhanced.
Interfacial Properties of Injection Molded Glass Fiber/Thermoplastics Composites
Authors: Wongpajan Rutchaneekorn , Mathurosemontri Suchalinee , Boonlertsamut Jitlada , Thumsorn Supaphorn , Hamada Hiroyuki
Published: February 2017

Four kinds of commercial glass fiber reinforced thermoplastics including GF reinforced polypropylene (GF/PP), GF reinforced polyamide 6 (GF/PA6), GF reinforced polycarbonate (GF/PC) and GF reinforced polyoxymethylene (GF/POM) were used in this study. The contents of GF were 10%, 20% and 40%. GF/PP, GF/PA6, PF/PC and GF/POM composites were fabricated to dumbbell specimen by injection molding. The effect of glass fiber contents on tensile properties, morphology and dynamic mechanical properties was investigated. Fiber volume fraction, fiber length distribution and fiber orientation were observed by burning off polymer resin and dispersed remaining fibers on a glass slide. The Kelly-Tyson model is used for prediction strength and calculated the critical fiber length of each GF reinforced polymer composites. Tensile strength of all composites increased with increasing glass fiber contents. The fiber orientation factor and the fiber length distribution were increased at higher contents of glass fibers. The interfacial shear strength values of GF/PP, GF/PC and GF/POM composites increased with increasing fiber contents while the declination of the interfacial shear strength was found in GF/PA6 composites. It is interesting to report that the interfacial shear strength of GFRP composites was calulated according to the modified rule of mixture (MROM) and the Kelly-Tyson model, which the interfacial shear strength of the composites increased with incresing glass fiber contents.
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.
Design of a Large and Versatile Two-Phase Flow Facility for Transient Studies in Pipes
Authors: Polanco Geanette , Da Paixao José , Vidal Antonio , Aguillón Orlando
Published: February 2017

Frequent interruptions of pipe flows is a common situation that has to be addressed by the industry working with single and two-phase flows. These interruptions generate abrupt changes in speed and therefore changes in the pressure inside the process pipe that could create major hazardous operating conditions or even produce system failures. In terms of two-phase or multiphase flow phenomenon, there is a real need for experimental data to support the increasing concern about determining reliability of pipe system, as well as, risk assessment concerning environmental hazards due to pipe system failures. Here after, the design and construction of a large and versatile test facility to study transient performance after a rapid closure occurs, is presented. The final goal of this facility is to create the possibility of having a database corresponding to the phenomenon known as water hammer for both single and two-phase flow. Different two-phase flow patterns can be simulated for the test. The facility is located on the premises of the Laboratory of Conversion of Mechanical Energy of the Simon Bolivar University, Caracas, Venezuela (LABCEM-USB). The facility consists of an instrumented closed flow loop that works with water and air at distinct flow proportions. The facility can be described as a group of seven interconnected sub-systems or modules that connect all the required capabilities. The Sub-systems are: liquid system, gas system, mixing system, pneumatic system, instrumentation system, electrical system and the test section. This modular design allows identification of the main components as individual subtask for the designing process. The test section is made in transparent material for visualization and it can be modified into different geometrical arrangements or configurations using different angles of inclination. Both static and dynamic pressure before and after an imminent closing of the valves for specific conditions of flow. The capability of selection of the inclination and the geometrical configuration of the test section (inverted “U” shape or linear pipe section) makes a unique air/water two-phase flow facility. The design represents a compact but versatile capability for evaluating test sections from a horizontal to a vertical position of the pipe. Initial results presented here show the pressure level achieved for different configurations.
The Effect of Intake and Exhaust on the Two-Dimensional Airfoil in a Distributed Propulsion System
Authors: Wang Yongsheng , Zhou Ming , Xu Quanyong
Published: February 2017

A new distributed propulsion system in which micro-engines were embedded into the wings was proposed. To consider the effects of the intake and exhaust of the engines, the system was simplified as a two-dimensional airfoil with a surface ingestion and a trailing edge jet. The influence of the layout was comprehensively studied with CFD. Compared to the original design, the surface ingestion and trailing edge jet can increase the lift coefficient. The lift-drag ratio increases at smaller attack angles (< 3°) and decreases at greater attack angles (> 3°). The lift-drag ratio improvement with surface ingestion at the leading edge is mainly due to the drop in drag, while the increase with ingestion close to the trailing edge is primarily because of the augment of lift. Moreover, increasing the temperature of the jet flow can enlarge the range of the attack angles with a higher lift-drag ratio.
Characterization of Adhesive Joints Under Shock-Wave Loading
Authors: Yildiz Salih , Shaffren Daniel , Jahnke Doug , Delale Feridun , Andreopoulos Yiannis
Published: February 2017

The failure behavior of adhesive joints under shock-wave loadings was investigated in a large scale shock tube facility for the first time. An overlapping specimen consisting of two parts, one circular patch and one supporting ring were bonded together in a specially designed jig. Sub-miniature semi-conductor strain gauges were attached on the specimen to monitor the transient strain on specific locations. A high speed camera was used to record the detachment of the patch from the ring. Image processing tool was used to track the position of the patch as a function of time. This information yield estimates of velocity, acceleration and kinetic energy of the patch. A finite element model was also created and the computation results were compared to the experimental values obtained.
Fluid-Structure Interaction Analysis on the Performance of the High-Pressure Fuel Pump for Diesel Engines
Authors: Qian Dexing , Liao Ridong , Xiang Jianhua , Sun Baigang , Wang Shangyong
Published: February 2017

In this paper, a 3-D fluid-structure interaction (FSI) analysis on the performance of the high-pressure fuel pump for diesel engines is presented. The fluid and structure are two-way coupled and several complex factors are taken into accounts in the FSI model. For instance, the fluid model includes not only the high-pressure fuel pump but also the rail and pressure-control valve which are used to maintain a stable delivery pressure of the pump; Gap boundary condition is adopted to simulate the opening and closing of the valve; The flow is assumed to be nonisothermal and the physical properties of the fuel such as dynamic viscosity and density are functions of pressure and temperature. While in the structure model, the spring force on the valve and the contacts between the valve and the valve seat as well as the top block are considered. The calculated volumetric efficiency losses agree well with the experiments, which indicates that the FSI model established in this study could well predict the physical phenomenon taking place in the high-pressure fuel pump. Several new conclusions can be drawn from the discussions on the results such as the suction efficiency loss due to the delay closing of the inlet valve is extremely small while the suction loss due to the expansion of the high-pressure fuel entrapped in the dead volume is very large.
Estimation of the Surface Temperature of a Photovoltaic Panel Through a Radiation-Natural Convection Heat Transfer Model in Matlab Simulink
Authors: Palacio Vega Mario A. , González López Orlando M. , Martínez Guarín Arnold R. , Gómez Vásquez Rafael D. , Bula Antonio , Mendoza Fandiño Jorge M.
Published: February 2017

This paper focuses on an approach to predict the temperature of a Photovoltaic panel under varying irradiation conditions in Cordoba, Colombia. The thermal model developed considers a heat transfer analysis in order to estimate the performance of a photovoltaic solar system due to local temperature variation. The heat transfer model analyzes the photovoltaic cell as a system exposed to radiation and natural convection by carrying out a first law energy balance which takes into account the radiation energy from the sun that hits the panel and the energy lost from the photovoltaic cell through natural convection and radiation. To determine the natural convection heat transfer coefficient, the Grashof number was employed along with Nusselt and Rayleigh number in a dimensionless form. The model has been implemented in the Matlab-Simulink platform that allows to establish a specific empirical correlation among the Nusselt number and Rayleigh for PV statics panels operating under natural convection condition. This experimental process consists in an iterative adjust of the theoretical equations of natural convection with experimental data gathered from a real PV module operation. The variables measured were the surface temperature, the environmental temperature and the solar irradiation provided by a pyranometer. It is found a good agreement between the radiation behavior and the predicted temperature. The higher values of the irradiation and environmental temperature coincides with predicted and observed PV surface temperatures and the thermal performance of the panel. The mean absolute error of the model was 3.09 K and the root mean square deviation 3.47 K.
Identification of Design Criteria for Converter Cooling System of Permanent Magnet Direct-Drive Wind Turbine Generator
Authors: Augusto Gerardo L. , Culaba Alvin B. , Gan Lim Laurence A.
Published: February 2017

The design criteria of converter cooling system for a 2.5 MW permanent magnet direct-drive wind turbine generator were investigated. Two (2) distribution networks with pipe sizes of DN40 and DN50 were used as basis for fluid flow analysis. The theoretical system pressure drop and system volume flow rate of converter cooling system were calculated using the governing equations of mass conservation, pump performance curve and distribution network characteristics. The system of nonlinear equations was solved using multivariable Newton-Raphson method with the solution vector determined using LU decomposition method. Numerical results suggest that the DN50 pipe provides a pressure drop limit of less than 300 Pa/m in the converter cooling system better than the pressure drop obtained from a DN40 pipe. The system volume flow rate of DN50 pipe was found to be above the operating limit of heat exchanger requirement of 135.30 L/min which needs to dissipate heat with a minimum of 50 kW.
Characterization of Nanoparticle Enhanced Multifunctional Sandwich Composites Subjected to Space Radiation
Authors: Abuali Galehdari Nasim , Kelkar Ajit D.
Published: February 2017

One of the major concerns in long duration space exploration is to minimize the exposure of crew and equipment to space radiation. High energy radiation not only can be hazardous to the health but also can damage the materials and electronics. Current designs are contained heavy metals to avoid occupational hazards from radiation exposures. As a result the shielding structures are heavy and not effective to attenuate all types of radiation. Therefore, the proposed lightweight sandwich composites are designed to effectively shield high energy radiations while providing structural integrity. In the manufactured hybrid sandwich composite, High Molecular Weight Poly Ethylene (HMWPE) woven fabrics are selected as face sheets due to their advanced mechanical properties and excellent physical properties along with effective shielding properties. Basically polymers due to high hydrogen content are considered as effective materials to attenuate high energy radiations. In addition, the core material is epoxy composites incorporating three weight percentages of three different nanoparticles viz. Boron Carbide, Boron Nanopowder and Gadolinium. In fact if polymers as low Z materials are used alone, they usually are not successful to attenuate highly penetrative rays. Therefore, one solution is known to infuse polymer matrix with high radiation absorption properties nanoparticles. Among several different nanomaterials, the three aforementioned nanofillers were chosen because of their good radiation absorption properties. Gadolinium has the highest thermal neutron cross section compare to any other known element and 10B-containing materials are known as excellent radiation absorbers and the composite filled with them have the advantage of convenient and safety in construction, operation and reintegration. The sandwich composites were manufactured using Heat-Vacuum Assisted Resin Transfer Molding method (H-VARTM), which is a cost effective method for high volume production of sandwich structures. To evaluate the shielding performance of manufactured sandwich panels the neutron attenuation testing was performed. The results from neutron radiation tests show more than 99% shielding performance in all of the sandwich panels. In comparison with other nanofillers, Boron Nanopowder showed highest radiation shielding efficiency (99.64%), which can be attributed to its lowest particle size and better dispersion ability into epoxy resin. The flatwise compression testing was performed on all four sandwich panels to determine the mechanical strength of materials before and after being exposure to radiation. The results demonstrate that proposed hybrid sandwich panels can preserve their mechanical integrity while being exposed to the radiation.