bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Piping Seismic Response Under Multiple Excitation
Authors: Kai Satoru , Watakabe Tomoyoshi , Kaneko Naoaki , Tochiki Kunihiro , Tsukimori Kazuyuki , Otani Akihito
Published: March 2018

The uniform response spectrum (URS) analysis method is generally used to seismic qualification of piping systems in nuclear power plants (NPPs). This method can reasonably not only compute dynamic responses of the piping systems exposed to different seismic motions from the building but also tend to overestimate the responses due to an assumption while conservatively considering a variety of the characteristic among input loadings. Increases of design seismic motions for NPPs in Japan by 2–3 times due to the 2011 off Pacific Coast of Tohoku Earthquake resulted that structures, systems, and components such as piping systems are subject to numbers of additional supporting structures to meet the design code requirements. Use of multiple-input analysis methods (independent support motion methods) is expected to bring high degree of precision in dynamic responses than the URS method. However, existence of a handful of experimental tests prevents from utilizing the method in the design process for NPPs in Japan. In order to practically utilize the multiple-input analysis methods in the plant design, this paper provides validation analyses and results for the multiple-input analysis methods for piping by conducting excitation tests and validation analyses. Some recommendations were also found in the study for seismic design of NPPs.
Experiment Study on Fluidelastic Instability of Tube Bundles Consisting of Different Frequency Tubes With Visual Image Processing System
Authors: Tan Wei , Li Zhao , Wu Hao , Wang Yipeng , Zhang Yanfeng , Zou Jiandong , Zhu Guorui
Published: March 2018

Fluidelastic instability (FEI) is the most harmful vibration mechanism for heat exchangers. Due to the inevitable manufacturing precision and assembly error, natural frequencies of tubes are not equal in the ideal condition. In order to describe the dispersion characteristic of tube bundles, a new factor named dispersion ratio is proposed in this paper. A series of tubes experiments in normal square and rotated triangular array with pitch ratio s = 1.4 and s = 1.28 were designed and conducted with high-speed camera and visual image processing system. Results show that FEI behaviors of tubes were greatly affected by tubes array geometry, pitch ratio, and dispersion ratio. Reduced critical velocity (Vcr) increased with dispersion ratio in normal square array but no obvious phenomenon was observed in rotated triangular array.
Experimental Characterization and Modeling of Thermal Contact Resistance of Electric Machine Stator-to-Cooling Jacket Interface Under Interference Fit Loading
Authors: Emily Cousineau J. , Bennion Kevin , Chieduko Victor , Lall Rajiv , Gilbert Alan
Published: March 2018

Cooling of electric machines is a key to increasing power density and improving reliability. This paper focuses on the design of a machine using a cooling jacket wrapped around the stator. The thermal contact resistance (TCR) between the electric machine stator and cooling jacket is a significant factor in overall performance and is not well characterized. This interface is typically an interference fit subject to compressive pressure exceeding 5 MPa. An experimental investigation of this interface was carried out using a thermal transmittance setup using pressures between 5 and 10 MPa. The results were compared to currently available models for contact resistance, and one model was adapted for prediction of TCR in future motor designs.
Multiscale Transient Modeling of Latent Energy Storage for Asynchronous Cooling
Authors: Helmns Andrea , Carey Van P.
Published: March 2018

This paper establishes a multiscale design evaluation framework that integrates performance models for a thermal energy storage (TES) unit and a subsystem heat exchanger (HX). The modeling facilitates the analysis of transient input and extraction processes for the TES device which uses solid–liquid phase change to store thermal energy. We investigate sensible and latent heat transfer through the unit's matrix structure which contains phase change material (PCM) in the interstitial spacing. The heat transfer is driven by a temperature difference between fluid flow passages and the PCM matrix which experiences sensible heat transfer until it reaches the PCM fusion point; then it undergoes melting or solidification in order to receive, or reject, energy. To capture these physics, we establish a dimensionless framework to model heat transfer in the storage device much like effectiveness-number of transfer units (NTU) analysis methods for compact HX. Solution of the nondimensional governing equations is subsequently used to predict the effectiveness of the transient energy input and extraction processes. The TES is examined within the context of a larger subsystem to illustrate how a high efficiency design target can be established for specified operating conditions that correspond to a variety of applications. The general applicability of the model framework is discussed and example performance calculations are presented for the enhancement of a Rankine power plant via asynchronous cooling.
Examining the Robustness of Grasping Force Optimization Methods Using
Uncertainty Analysis
Authors: Cloutier Aimee , Yang James
Published: March 2018

The development of robust and adaptable methods of grasping force optimization (GFO) is an important consideration for robotic devices, especially those which are designed to interact naturally with a variety of objects. Along with considerations for the computational efficiency of such methods, it is also important to ensure that a GFO approach chooses forces which can produce a stable grasp even in the presence of uncertainty. This paper examines the robustness of three methods of GFO in the presence of variability in the contact locations and in the coefficients of friction between the hand and the object. A Monte Carlo simulation is used to determine the resulting probability of failure and sensitivity levels when variability is introduced. Two numerical examples representing two common grasps performed by the human hand are used to demonstrate the performance of the optimization methods. Additionally, the method which yields the best overall performance is also tested to determine its consistency when force is applied to the object's center of mass in different directions. The results show that both the nonlinear and linear matrix inequality (LMIs) methods of GFO produce acceptable results, whereas the linear method produces unacceptably high probabilities of failure. Further, the nonlinear method continues to produce acceptable results even when the direction of the applied force is changed. Based on these results, the nonlinear method of GFO is considered to be robust in the presence of variability in the contact locations and coefficients of friction.
Design of Sliding Mode Controller With Proportional Integral Sliding Surface for Robust Regulation and Tracking of Process Control Systems
Authors: Kadu C. B. , Khandekar A. A. , Patil C. Y.
Published: March 2018

This paper deals with the design of sliding mode controller (SMC) with proportional plus integral sliding surface for regulation and tracking of uncertain process control systems. However, design method requires linear state model of the system. Tuning parameter of SMC has been determined using linear quadratic regulator (LQR) approach. This results in optimum sliding surface for selected performance index. Matched uncertainty is considered to obtain the stability condition in terms of its upper bound. A conventional state observer has been used to estimate the states. The estimated states are then fed to controller for determining control signal. The simulation study and experimentation on real-life level system have been carried out to validate performance and applicability of the proposed controller.
Propagation of Parametric Uncertainties in a Nonlinear Aeroelastic System Using an Improved Adaptive Sparse Grid Quadrature Routine
Authors: Devathi Harshini , Sarkar Sunetra
Published: March 2018

A novel uncertainty quantification routine in the genre of adaptive sparse grid stochastic collocation (SC) has been proposed in this study to investigate the propagation of parametric uncertainties in a stall flutter aeroelastic system. In a hypercube stochastic domain, presence of strong nonlinearities can give way to steep solution gradients that can adversely affect the convergence of nonadaptive sparse grid collocation schemes. A new adaptive scheme is proposed here that allows for accelerated convergence by clustering more discretization points in regimes characterized by steep fronts, using hat-like basis functions with nonequidistant nodes. The proposed technique has been applied on a nonlinear stall flutter aeroelastic system to quantify the propagation of multiparametric uncertainty from both structural and aerodynamic parameters. Their relative importance on the stochastic response is presented through a sensitivity analysis.
Crack Growth and Tolerance of Stainless Steel Canisters in the Marine Environment
Authors: Heui-Yung Chang
Published: March 2018

Most of the dry storage cask systems that are used to contain nuclear fuel are austenitic stainless steel canisters. Past experience suggests that stainless steel is susceptible to stress corrosion cracking (SCC) in the presence of chloride salts. A crack growth rate (CGR) model has been developed and applied to evaluate the crack depth in stainless steel canisters over the timeframe of the storage at independent spent fuel storage installations. This study focuses on stainless steel canisters for dry storage systems in the two nuclear power plants in Taiwan. The crack depth was first evaluated using the CGR model, site climate data, and canister surface temperature. The critical crack size and depth were then determined from the structural tolerance assessment of the canister shells. It was found that the variations in the thermal and hydraulic properties of dry storage canisters produce large variations in the SCC initiation time but do not affect the surface temperature in the range of 55–60 °C. The CGR at the SCC initiation is high and the growth of flaws is significant. The surface temperature and CGR decrease with time. The total crack depth therefore may not vary greatly as a function of SCC initiation time. Overall, dry storage canisters show high structural tolerance to crack size and depth.
Strain-Hardening Model of Dual-Phase Steel With Geometrically Necessary Dislocations
Authors: Ren Chuang , Dan Wen Jiao , Xu Yong Sheng , Zhang Wei Gang
Published: March 2018

The strain-hardening behavior of metal during the uniaxial tension can be treated as the competing result of generation and annihilation of statistically stored dislocations (SSDs). Geometrically necessary dislocations (GNDs) are generated to accommodate a lattice mismatch and maintain deformation compatibility in dual-phase (DP) steels because of the heterogeneous deformation of the microstructure. In this study, a dislocation-based strain-hardening model that encompasses GNDs was developed to describe the mechanical properties of dual-phase steel. The GNDs were obtained based on a cell model of uniaxial deformation and the SSDs were calculated using a dynamic recovery model. The strain of each phase is a nonlinear function of the overall material strain obtained by the point-interpolation method (PIM). The proposed strain-hardening model was verified by using commercially produced DP600 steel. The calculated results obtained with GNDs are able to predict more precisely the experimental data than that without. The effects of martensite volume fraction and grain size on the strain-hardening behaviors of individual phases and material were studied.
Response of High-Pressure Micro Water Jets to Static and Dynamic Nonuniform Electric Fields
Authors: Shi Yi , Cao Jian , Ehmann Kornel F.
Published: March 2018

The manipulation of the trajectory of high-pressure micro water jets has the potential to greatly improve the accuracy of water jet related manufacturing processes. An experimental study was conducted to understand the basic static and dynamic responses of high-pressure micro water jet systems in the presence of nonuniform electric fields. A single electrode was employed to create a nonuniform electric field to deflect a high-pressure micro water jet toward the electrode by the dielectrophoretic force generated. The water jet's motions were precisely recorded by a high-speed camera with a 20× magnification and the videos postprocessed by a LabVIEW image processing program to acquire the deflections. The experiments revealed the fundamental relationships between three experimental parameters, i.e., voltage, pressure, and the distance between the water jet and the electrode and the deflection of the water jet in both nonuniform static and dynamic electric fields. In the latter case, electric signals at different frequencies were employed to experimentally investigate the jet's dynamic response, such as response time, frequency, and the stability of the water jet's motion. A first-order system model was proposed to approximate the jet's response to dynamic input signals. The work can serve as the basis for the development of closed-loop control systems for manipulating the trajectory of high-pressure micro water jets.
Effect of Jet Oscillation on the Maximum Impingement Plate Skin Friction
Authors: Ritcey Adam , McDermid Joseph R. , Ziada Samir
Published: March 2018

The maximum impingement plate skin friction and flow field is measured for an acoustically forced planar impinging gas jet using oil film interferometry (OFI) and particle image velocimetry (PIV), respectively. The study is performed at a jet Reynolds number of Rejet = 11,000 and an impingement distance H, which is set to eight times the nozzle width W. The planar impinging gas jet is forced at the jet nozzle exit using Strouhal numbers StH = 0.39, 0.76, and 1.1, which are similar to those associated with the jet-plate tones measured in air-knife wiping experiments. The flow-field measurements indicate that the jet column oscillates at the applied forcing frequency, and depending on the forcing frequency, organized vortex structures can be identified in the shear layers that impinge on the plate surface. Both of these jet oscillation features result in a reduction in the time-averaged maximum impingement plate skin friction. This skin friction reduction is attributed to momentum loss at the jet centerline caused by increased levels of fluid entrainment and mixing of the surrounding quiescent fluid.
Smoothed Particle Hydrodynamics for the Rising Pattern of Oil Droplets
Authors: Hosseinkhani Mehdi Rostami , Omidvar Pourya
Published: March 2018

The problem of rising droplets in liquids is important in physics and has had many applications in industries. In the present study, the rising pattern of oil droplets has been examined using the smoothed particle hydrodynamics (SPH), which is a fully Lagrangian meshless method. The open-source SPHysics2D code is developed to two phase by adding the effects of surface tension and an added pressure term to the momentum equation. Several problems of droplet dynamics were simulated, and the performance of the developed code is evaluated. First, the still water–oil tank problem was solved to examine the hydrostatic pressure, especially at the interface, for different density ratios. Then, the rising patterns of an oil droplet of different densities are simulated and the time evolutions of the rising velocity and center of mass are shown. It is shown that the shape and behavior of the droplet rising depend on the balance between viscous, surface tension, and dynamic forces. Afterward, the flow morphologies of multiple droplet rising are shown where the density ratio causes negligible effects on the droplet shape, but it has large effects on the dynamics behavior of rising process.
Effect of Ceramic and Metallic Reinforcement on Mechanical, Corrosion, and Tribological Behavior of Aluminum Composite by Adopting Design of Experiment Through Taguchi Technique
Authors: Sureshkumar P. , Uvaraja V. C.
Published: March 2018

An attempt has been made to develop and study the properties and behavior of structure-based aluminum composite. Aluminum (AA6063)-based composites were fabricated by stir casting technique (also known as liquid metallurgy route) by varying weight percentage of metallic-based copper nitrate Cu (NO3)2 with fixed proposition of ceramic-based silicon nitride (Si3N4) reinforcement. The mechanical and corrosion properties and tribological behavior of composite were studied. Further, the sample microstructure and characterizations were investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD) technique. The composite with fixed weight proportion of ceramic and higher metallic reinforced samples shows higher tensile strength, improved corrosion resistance, and higher hardness behavior. Due to higher hardness nature, the tribological properties of composite such as wear rate and coefficient of friction have been reduced. Moreover, the impact strength of composite decreased due to combination of ceramic and metallic reinforcement. In addition to the above study, design of experiment (DOE) was adopted to optimize the major wear test parameters such as percentage of reinforcement, applied load, sliding distance, and sliding speed. Finally, analysis of variance (ANOVA) was carried out to identify the most significant test parameter and its interaction affecting wear behavior and its coefficient of friction of composite sample.
Effects of Microstructure of Quasicrystal Alloys on Their Mechanical and Tribological Performance
Authors: Lee Kyungjun , Dai Wei , Naugle Donald , Liang Hong
Published: March 2018

The current design of materials against wear considers hardness as the sole material property. As a result, the brittleness associated with increased hardness leads to severe damage. The purpose of this research is to understand the nature of conflicts between hardness and toughness of a new alloy composite. First, we designed Al-Cu-Fe alloys containing crystal structures of λ, β, and quasi-crystalline i-phase. These and their combination with others lead to a set of alloys with various hardness and fracture toughness. Experimental study was carried out using a noble and hard tungsten carbide (WC) ball against sample disks. The WC ball did not produce any wear. The wear rate of those alloys was found to be dependent not only on their hardness, but also the toughness, an alternative to the well-accepted Archard-based equations.
Physics-Based Modeling for Lap-Type Joints Based on the Iwan Model
Authors: Zhan Wanglong , Huang Ping
Published: March 2018

This study proposed a physics-based heuristic modeling for the nonlinear constitutive relation of bolted joints based on the Iwan model accompanying with the rough surface contact theory. The approach led to an Iwan distribution function which possesses the tribology-related features of the contact interface. In particular, the break-free force distribution function of the Jenkins elements could be expressed in terms of height distribution of surface asperities. The model considered the contribution of elastically, elasto-plastically as well as plastically deformed asperities to the total tangential loads. Following this, constitutive relations for lap-type bolted joints and the corresponding backbone curves, hysteresis loops, and energy dissipation per cycle were obtained. A model application was implemented and the results were compared with the published experimental results. The proposed model agrees very well with the experimental results when the contact parameters met the actual contact situation. The obtained results indicated that the model can be used to study the tangential behaviors of rough surfaces.
Nonlinear Vibrations of Buried Rectangular Plate
Authors: Hong Guangyang , Li Jian , Luo Zhicong , Li Hongying
Published: March 2018

We perform an investigation on the vibration response of a simply supported plate buried in glass particles, focusing on the nonlinear dynamic behaviors of the plate. Various excitation strategies, including constant-amplitude variable-frequency sweep and constant-frequency variable-amplitude sweep are used during the testing process. We employ the analysis methods of power spectroscopy, phase diagramming, and Poincare mapping, which reveal many complicated nonlinear behaviors in the dynamic strain responses of an elastic plate in granular media, such as the jump phenomena, period-doubling bifurcation, and chaos. The results indicate that the added mass, damping, and stiffness effects of the granular medium on the plate are the source of the nonlinear dynamic behaviors in the oscillating plate. These nonlinear behaviors are related to the burial depth of the plate (the thickness of the granular layer above plate), force amplitude, and particle size. Smaller particles and a suitable burial depth cause more obvious jump and period-doubling bifurcation phenomena to occur. Jump phenomena show both soft and hard properties near various resonant frequencies. With an increase in the excitation frequency, the nonlinear added stiffness effect of the granular layer makes a transition from strong negative stiffness to weak positive stiffness.
Study on Effects of Heat Loss and Channel Deformation on Thermal-Hydraulic Performance of Semicircular Straight Channel Printed Circuit Heat Exchangers
Authors: Yoon Su-Jong , O'Brien James , Sabharwall Piyush , Wegman Kevin , Sun Xiaodong
Published: March 2018

Effective and robust high-temperature heat transport systems are essential for the successful deployment of advanced high temperature reactors. The printed circuit heat exchanger (PCHE) is a strong potential candidate for the intermediate or secondary loop of high temperature gas-cooled reactors (HTGRs) due to their high power density and compactness. For high-temperature PCHE applications, the heat loss, which is difficult to be insulated completely, could lead to the degradation of heat exchanger performance. This paper describes an analytical methodology to evaluate the thermal-hydraulic performance of PCHEs from experimental data, accounting for extraneous heat losses. Experimental heat exchanger effectiveness results, evaluated without accounting for heat loss, exhibited significant data scatter while the data were in good agreement with the ε-NTU method once the heat loss was accounted for. The deformation of PCHEs would occur during the diffusion-bonding fabrication process or high temperature operations due to the thermal deformation. Computational assessment of the PCHE performance test data conducted at the Ohio State University showed that the deformation of flow channels caused increase of pressure loss of the heat exchanger. The computational fluid dynamics (CFD) simulation results based on the nominal design parameters underestimated the pressure loss of the heat exchanger compared to the experimental data. Image analysis for the flow channel inlet and outlet was conducted to examine the effect of channel deformation on the heat exchanger performance. The CFD analysis based on the equivalent channel diameter obtained from the image analysis resulted in a better prediction of PCHE pressure loss.
Simple Effective Conservative Treatment of Uncertainty From Sparse
Samples of Random Variables and Functions
Authors: Romero Vicente J. , Schroeder Benjamin B. , Dempsey James F. , Breivik Nicole L. , Orient George E. , Antoun Bonnie R. , Lewis John R. , Winokur Justin G.
Published: March 2018

This paper examines the variability of predicted responses when multiple stress–strain curves (reflecting variability from replicate material tests) are propagated through a finite element model of a ductile steel can being slowly crushed. Over 140 response quantities of interest (QOIs) (including displacements, stresses, strains, and calculated measures of material damage) are tracked in the simulations. Each response quantity's behavior varies according to the particular stress–strain curves used for the materials in the model. We desire to estimate or bound response variation when only a few stress–strain curve samples are available from material testing. Propagation of just a few samples will usually result in significantly underestimated response uncertainty relative to propagation of a much larger population that adequately samples the presiding random-function source. A simple classical statistical method, tolerance intervals (TIs), is tested for effectively treating sparse stress–strain curve data. The method is found to perform well on the highly nonlinear input-to-output response mappings and non-normal response distributions in the can crush problem. The results and discussion in this paper support a proposition that the method will apply similarly well for other sparsely sampled random variable or function data, whether from experiments or models. The simple TI method is also demonstrated to be very economical.
Evaluation of Ride Comfort and Driving Safety for Moving Vehicles on Slender Coastal Bridges
Authors: Zhu J. , Zhang W. , Wu M. X.
Published: March 2018

Evaluating driving safety of moving vehicles on slender coastal bridges as well as bridge safety is important to provide supporting data to make decisions on continuing or closing the operations of bridges under extreme weather conditions. However, such evaluations could be complicated due to the complex dynamic interactions of vehicle-bridge-wind-wave (VBWW) system. The present study proposes a comprehensive evaluation methodology on vehicle ride comfort and driving safety on the slender coastal bridges subject to vehicle, wind, and wave loads. After a brief introduction of the VBWW coupling dynamic system and obtaining the dynamic responses of the vehicles, the vehicle ride comfort is evaluated using the advanced procedures as recommended in the ISO 2631-1 standard based on the overall vibration total value (OVTV). The vehicle driving safety is analyzed based on two evaluation criteria, i.e., the roll safety criteria (RSC) and the sideslip safety criteria (SSC), through the vehicle contact force responses at the wheels. Finally, the proposed methodology is applied to a long-span cable-stayed bridge for the vehicle ride comfort and driving safety evaluation.
A High-Dimensional Reliability Analysis Method for Simulation-Based Design Under Uncertainty
Authors: Sadoughi Mohammad Kazem , Li Meng , Hu Chao , MacKenzie Cameron A. , Lee Soobum , Eshghi Amin Toghi
Published: March 2018

Reliability analysis involving high-dimensional, computationally expensive, highly nonlinear performance functions is a notoriously challenging problem in simulation-based design under uncertainty. In this paper, we tackle this problem by proposing a new method, high-dimensional reliability analysis (HDRA), in which a surrogate model is built to approximate a performance function that is high dimensional, computationally expensive, implicit, and unknown to the user. HDRA first employs the adaptive univariate dimension reduction (AUDR) method to construct a global surrogate model by adaptively tracking the important dimensions or regions. Then, the sequential exploration–exploitation with dynamic trade-off (SEEDT) method is utilized to locally refine the surrogate model by identifying additional sample points that are close to the critical region (i.e., the limit-state function (LSF)) with high prediction uncertainty. The HDRA method has three advantages: (i) alleviating the curse of dimensionality and adaptively detecting important dimensions; (ii) capturing the interactive effects among variables on the performance function; and (iii) flexibility in choosing the locations of sample points. The performance of the proposed method is tested through three mathematical examples and a real world problem, the results of which suggest that the method can achieve an accurate and computationally efficient estimation of reliability even when the performance function exhibits high dimensionality, high nonlinearity, and strong interactions among variables.
Design and Evaluation of a Novel Rotatable One-Element Snake Bone for NOTES
Authors: Liu Bin , Zhang Aoyu , Liu John , Han Zhimin , Xie Tianyu
Published: March 2018

The distal head of the natural orifice transluminal endoscopic surgery (NOTES) platform commonly uses the structure of a snake bone, which cannot rotate, and the manufacturing is often time-consuming. A novel rotatable, one-element snake bone for NOTES is proposed. This paper first describes the movement mechanism and actuation. The new structure, which is composed of hinge pairs for bending and track-sled rings for rotation, was designed to reach a 90 deg bending angle and 62 deg rotational angle. The workspace of the snake bone was derived using screw theory and was simulated on matlab. The relationship between the angle and wire displacement was analyzed in detail. The new snake bone system bent and rotated by manipulating control wires that were actuated by DC motors, and its angular movements were measured by motion sensors with an angle error within ±2.6 deg. The snake bone was mounted on a flexible tube, inserted into a colonoscopy model, and navigated by motor actuation to eventually reach the cecum. The experimental results demonstrate the new snake bone's ability to travel through a natural orifice by rotating and bending, which satisfies the mobility requirement for NOTES.
Second Law Analysis of Magneto-Micropolar Fluid Flow Between Parallel Porous Plates
Authors: Kosarineia Abbas , Sharhani Sajad
Published: March 2018

In this study, the influence of the applied magnetic field is investigated for magneto-micropolar fluid flow through an inclined channel of parallel porous plates with constant pressure gradient. The lower plate is maintained at constant temperature and the upper plate at a constant heat flux. The governing motion and energy equations are coupled while the effect of the applied magnetic field is taken into account, adding complexity to the already highly correlated set of differential equations. The governing equations are solved numerically by explicit Runge–Kutta. The velocity, microrotation, and temperature results are used to evaluate second law analysis. The effects of characteristic and dominate parameters such as Brinkman number, Hartmann Number, Reynolds number, and micropolar viscosity parameter are discussed on velocity, temperature, microrotation, entropy generation, and Bejan number in different diagrams. The results depicted that the entropy generation number rises with the increase in Brinkman number and decays with the increase in Hartmann Number, Reynolds number, and micropolar viscosity parameter. The application of the magnetic field induces resistive force acting in the opposite direction of the flow, thus causing its deceleration. Moreover, the presence of magnetic field tends to increase the contribution of fluid friction entropy generation to the overall entropy generation; in other words, the irreversibilities caused by heat transfer reduced. Therefore, to minimize entropy, Brinkman number and Hartmann Number need to be controlled.
Experimental Study on Melt Coolability Capability of Calandria Vault Water During Severe Accident in Indian PHWRs for Prolonged Duration
Authors: Prasad Sumit V. , Nayak A. K.
Published: March 2018

The present experimental investigation in a scaled facility of an Indian pressurized heavy water reactors (PHWRs) is focused on the heat transfer behavior from the calandria vessel (CV) to the calandria vault during a prolonged severe accident condition in the presence of decay heat. The transient heat transfer simulates the conditions from single phase to boiling in the calandria vault water, partial uncovery of the CV due to boil off of water in the vault, and refill of calandria vault. Molten borosilicate glass was used as the simulant due to its comparable heat transfer characteristics similar to prototypic material. About 60 kg of the molten material was poured into the test section at about 1100 °C. Decay heat in the melt pool was simulated by using high watt cartridge type heaters. The temperature distributions inside the molten pool across the CV wall thickness and vault water were measured for prolonged period which can be divided into various phases, viz., single phase natural convection heat transfer in calandria vault, boiling heat transfer in calandria vault, partial uncovery of CV, and refilling calandria vault. Experimental results showed that once the crust formed, the inner vessel temperature remained very low and vessel integrity maintained. Even boiling of calandria vault water and uncovery of CV had negligible effect on melt, CV, and vault water temperature. The heat transfer coefficients on outer vessel surface were obtained and compared with various conditions.
Electroplastic Drilling of Low- and High-Strength Steels
Authors: Ruszkiewicz Brandt J. , Gendreau Elizabeth , Niaki Farbod Akhavan , Mears Laine
Published: March 2018

When postforming machining operations are required on high-strength structural components, tool life becomes a costly issue, often requiring external softening via techniques such as laser assistance for press-hardened steel components. Electrically assisted manufacturing (EAM) uses electricity during material removal processes to reduce cutting loads through thermal softening. This paper evaluates the effect of electric current on a drilling process, termed electroplastic drilling, through the metrics of axial force, and workpiece temperature when machining mild low carbon steel (1008CR steel) and an advanced high strength press hardened steel. A design of experiment (DoE) is conducted on 1008CR steel to determine primary process parameter effects; it is found that electricity can reduce cutting loads at the cost of an increased workpiece temperature. The knowledge generated from the DoE is applied to the advanced high strength steel to evaluate cutting force reduction, process time savings, and tool life improvement at elevated feedrates. It is found that force can be reduced by 50% in high feedrates without observing catastrophic tool failure for up to ten cuts, while tool failure occurs in only a single cut for the no-current condition. Finally, the limitations of the developed model in electroplastic drilling are discussed along with future suggestions for industrialization of the method.
Drilling CFRP Laminates by Dual-Axis Grinding Wheel System With Copper/Diamond Functionally Graded Grinding Wheel
Authors: Kunimine Takahiro , Tsuge Hideaki , Ogawa Daisuke , Yamada Motoko , Sato Hisashi , Watanabe Yoshimi
Published: March 2018

This study aims to investigate the drilling performance of a copper/diamond functionally graded grinding wheel (FGGW) fabricated by centrifugal sintered-casting for carbon fiber-reinforced plastic (CFRP) laminates by originally designed dual-axis grinding wheel (DAGW) system. The copper/diamond FGGW was also originally designed and fabricated by the centrifugal sintered-casting to suppress abrasive-grain wear and reduce the consumption of abrasive grains in our previous study. Drilling tests were carried out over 50 holes in dry machining. Thrust force was evaluated with force sensor during drilling test. Hole diameter, roundness, and roughness were measured to assess hole quality. Drill chips were observed by scanning electron microscope (SEM) to investigate chip morphology. Precision drilling without burring and delamination was achieved in CFRP laminates. Good hole-quality was still obtained over 50 holes due to the low thrust force during drilling. Specific three-dimensional (3D) drilling process of the DAGW system enabled stable and precision drilling with low thrust force in CFRP laminates continuously.
Evaluation on the Performance of Photovoltaic–Thermal Hybrid System Using CO2 as a Working Fluid
Authors: Pumaneratkul Chayadit , Yamasaki Haruhiko , Yamaguchi Hiroshi , Iwamoto Yuhiro
Published: March 2018

In this study, the CO2-based photovoltaic–thermal hybrid system has been investigated with an objective to increase the power generation efficiency in photovoltaic solar panel and to improve the performance of supercritical CO2 solar Rankine cycle system (SRCS). From a previous study, an improvement of 2% of power generation efficiency was confirmed via experimental investigation. In this study, the temperature distribution on the CO2-based photovoltaic–thermal hybrid system has been numerically and experimentally investigated and confirmed with referenced experimental results. Particularly, in this study, the one-dimensional (1D) calculation of CO2 flow in the cooling tube and three-dimensional (3D) calculation of temperature distribution on the surface of the photovoltaic solar panel are conducted. The typical summer and winter weather conditions are used as the calculation references to investigate the effect of temperature distribution of the photovoltaic solar panel. The results show that the trend of temperature distribution from calculation was confirmed with the experimental data both in summer and winter conditions. Furthermore, in summer condition, the CO2 temperature was increased to a maximum of 28 °C.
A soft, bistable valve for autonomous control of soft actuators
Authors: Rothemund Philipp , Ainla Alar , Belding Lee , Preston Daniel J. , Kurihara Sarah , Suo Zhigang , Whitesides George M.
Published: March 2018

An entirely soft valve uses a snap-through instability to integrate autonomous control functions into soft actuators.
Extended release of perioperative immunotherapy prevents tumor recurrence and eliminates metastases
Authors: Park Chun Gwon , Hartl Christina A. , Schmid Daniela , Carmona Ellese M. , Kim Hye-Jung , Goldberg Michael S.
Published: March 2018

Prolonged perioperative delivery of immunotherapy prevents local tumor recurrence and eliminates established spontaneous metastases.
Draft Genome Sequence of Multidrug-Resistant Stenotrophomonas pavanii BWK1, Isolated from Mareca penelope Feces
Authors: Kenzaka Takehiko , Tani Katsuji
Published: March 2018

Migratory birds serve as vectors by transmitting antibiotic-resistant bacteria across large distances. Here, we isolated a multidrug-resistant
Stenotrophomonas pavanii
strain, BWK1, from
Mareca penelope
feces. Analysis of the draft genome sequence of the isolated strain indicated that BWK1 harbors a class A beta-lactamase, metallo-beta-lactamase, and several multidrug efflux pumps.
King-Devick concussion test performs poorly as a screening tool in elite rugby union players: a prospective cohort study of two screening tests versus a clinical reference standard
Authors: Fuller Gordon Ward , Cross Matthew J , Stokes Keith A , Kemp Simon P T
Published: March 2018

Background

The King-Devick (KD) test is an objective clinical test of eye movements that has been used to screen for concussion. We characterised the accuracy of the KD test and the World Rugby Head Injury Assessment (HIA-1) screening tools as methods of off-field evaluation for concussion after a suspicious head impact event.

Methods

A prospective cohort study was performed in elite English rugby union competitions between September 2016 and May 2017. The study population comprised consecutive players identified with a head impact event with the potential to result in concussion. The KD test was administered off-field, alongside the World Rugby HIA-1 screening tool, and the results were compared with the preseason baseline. Accuracy was measured against a reference standard of confirmed concussion, based on the clinical judgement of the team doctor after serial assessments.

Results

145 head injury events requiring off-field medical room screening assessments were included in the primary analysis. The KD test demonstrated a sensitivity of 60% (95% CI 49.0 to 70) and a specificity of 39% (95% CI 26 to 54) in identifying players subsequently diagnosed with concussion. Area under the receiver operating characteristic curve for prolonged KD test times was 0.51 (95% CI 0.41 to 0.61). The World Rugby HIA-1 off-field screening tool sensitivity did not differ significantly from the KD test (sensitivity 75%, 95% CI 66 to 83, P=0.08), but specificity was significantly higher (91%, 95% CI 82 to 97, P<0.001). Although combining the KD test and the World Rugby HIA-1 multimodal screening assessment achieved a significantly higher sensitivity of 93% (95% CI 86% to 97%), there was a significantly lower specificity of 33% (95% CI 21% to 48%), compared with the HIA-1 test alone.

Conclusions

The KD test demonstrated limited accuracy as a stand-alone remove-from-play sideline screening test for concussion. As expected with the addition of any parallel test, combination of the KD test with the HIA-1 off-field screening tool provided improved sensitivity in identifying concussion, but at the expense of markedly lower specificity. These results suggest that it is unlikely that the KD test will be incorporated into multimodal off-field screening assessments for concussion at the present time.
Outpatient management of children at low risk for bacterial meningitis
Authors: Garcia Silvia , Echevarri Janire , Arana-Arri Eunate , Sota Mercedes , Benito Javier , Mintegi Santiago
Published: March 2018

Objective

To determine the outcome of children aged 2–14 years with cerebrospinal fluid (CSF) pleocytosis and at very low risk for bacterial meningitis managed as outpatients without antibiotics.

Methods

Multicentre, prospective, observational study conducted at nine Spanish paediatric EDs. Patients were diagnosed with meningitis based on clinical suspicion of meningitis and CSF pleocytosis when evaluated in the ED. Children between 2 and 14 years of age with pleocytosis and very low-risk criteria for bacterial meningitis (well appearing, Bacterial Meningitis Score (BMS)=0, procalcitonin (PCT)<0.5 ng/mL and observation without deterioration for less than 24 hours in the ED) were treated as outpatients without antibiotics pending CSF cultures. The primary composite outcome was a final diagnosis of bacterial meningitis or return to the ED for clinical deterioration.

Results

Of 182 children between 2 and 14 years old diagnosed with meningitis, 56 met the very low-risk criteria and 45 were managed as outpatients. None was diagnosed with bacterial meningitis or returned due to clinical deterioration. Another 31 patients with BMS=1 (due to a peripheral absolute neutrophil count (ANC)>10 000/mm3) and PCT <0.5 ng/mL were managed as outpatients, diagnosed with aseptic meningitis and did well. BMS using PCT had the same sensitivity but greater specificity than classic BMS.

Conclusions

This set of low-risk criteria appears safe for the outpatient management without antibiotics of children with CSF pleocytosis. Larger studies are needed to evaluate the predictive values of replacing peripheral ANC with PCT in the BMS.
A multivariate approach to investigate the combined biological effects of multiple exposures
Authors: Jain Pooja , Vineis Paolo , Liquet Benoît , Vlaanderen Jelle , Bodinier Barbara , van Veldhoven Karin , Kogevinas Manolis , Athersuch Toby J , Font-Ribera Laia , Villanueva Cristina M , Vermeulen Roel , Chadeau-Hyam Marc
Published: March 2018

Epidemiological studies provide evidence that environmental exposures may affect health through complex mixtures. Formal investigation of the effect of exposure mixtures is usually achieved by modelling interactions, which relies on strong assumptions relating to the identity and the number of the exposures involved in such interactions, and on the order and parametric form of these interactions. These hypotheses become difficult to formulate and justify in an exposome context, where influential exposures are numerous and heterogeneous. To capture both the complexity of the exposome and its possibly pleiotropic effects, models handling multivariate predictors and responses, such as partial least squares (PLS) algorithms, can prove useful. As an illustrative example, we applied PLS models to data from a study investigating the inflammatory response (blood concentration of 13 immune markers) to the exposure to four disinfection by-products (one brominated and three chlorinated compounds), while swimming in a pool. To accommodate the multiple observations per participant (n=60; before and after the swim), we adopted a multilevel extension of PLS algorithms, including sparse PLS models shrinking loadings coefficients of unimportant predictors (exposures) and/or responses (protein levels). Despite the strong correlation among co-occurring exposures, our approach identified a subset of exposures (n=3/4) affecting the exhaled levels of 8 (out of 13) immune markers. PLS algorithms can easily scale to high-dimensional exposures and responses, and prove useful for exposome research to identify sparse sets of exposures jointly affecting a set of (selected) biological markers. Our descriptive work may guide these extensions for higher dimensional data.
Preparation and Characterization of Carbon Nanotubes/Carbon Fiber/Phenolic Composites on Mechanical and Thermal Conductivity Properties
Authors: Feng Ailing , Jia Zirui , Yu Qiang , Zhang Hongxia , Wu Guanglei
Published: March 2018

The properties of fiber-matrix interface pay an important effect on the mechanical properties of carbon fiber-reinforced composites. To improve the interfacial properties in carbon fiber/phenolic resin (CF/PF) composites, CF adhered CNTs (CNTs-CF) were prepared by CVD method. The surface of treated CF and the distribution of CNTs in the interfacial region of CF were detected by scanning electron microscopy (SEM). SEM images identified 700[Formula: see text]C being the optimum growth temperature to obtain CNTs-CF, in which CNTs randomly dispersed surrounding the individual fiber surfaces. Compared to crude CF/PF composites, the tensile strength, bending strength, shear strength, impact strength, thermal conductivity at 25[Formula: see text]C of CNTs-CF/PF composites increase by 144.5%, 59.2%, 129.0%, 75.9% and 41.7%. The improvement of mechanical properties is due to that the homogenously dispersed CNTs serve as a supplementary reinforcement to the interface and further reduce inter-laminar stress concentration. This represents an important step toward CNT-reinforced polymers with high mechanical properties.
Aerosol-assisted chemical vapor deposition of ultra-thin CuOx films as hole transport material for planar perovskite solar cells
Authors: Zhang Zhixin , Chen Shuqun , Li Pingping , Li Hongyi , Wu Junshu , Hu Peng , Wang Jinshu
Published: March 2018

This paper reports on the fabrication of CuOx films to be used as hole transporting layer (HTL) in CH3NH3PbI3 perovskite solar cells (PSCs). Ultra-thin CuOx coatings were grown onto FTO substrates for the first time via aerosol-assisted chemical vapor deposition (AACVD) of copper acetylacetonate in methanol. After incorporating into the PSCs prepared at ambient air, a highest power conversion efficiency (PCE) of 8.26% with HTL and of 3.34% without HTL were achieved. Our work represents an important step in the development of low-cost CVD technique for fabricating ultra-thin metal oxide functional layers in thin film photovoltaics.