bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Material Behavior of the Fused Deposition Modeling Processed Parts
Authors: Somireddy Madhukar , Czekanski Aleksander
Published: July 2017

In the present research, one of the additive manufacturing techniques, fused deposition modeling (FDM) fabricated parts are considered for investigation of their material behavior. The FDM process is a layer upon layer deposition of a material to build three dimensional parts and such parts behave as laminated composite structures. Each layer of the part acts as a unidirectional fiber reinforced lamina, which is treated as an orthotropic material. The mesostructure of a part fabricated via fused deposition modeling process is accounted for in the investigation of its mechanical behavior. The finite element (FE) procedure for characterization of a material constitutive law for the FDM processed parts is presented. In the analysis, the mesostructure of the part obtained via FDM process is replicated in the finite element models. Finite element models of tensile specimens are developed with mesostructure that would be obtained from FDM process, then uniaxial tensile test simulations are conducted. The elastic moduli of a lamina are calculated from the linear analysis and the strength parameters are obtained from the nonlinear finite element analysis. The present work provides a FE methodology to find elastic moduli and strength parameters of a FDM processed part by accounting its mesostructure in the analysis.
Patterned Microstructure Array Fabrication by Using a Novel Standing Surface Acoustic Wave Device
Authors: Wang Yancheng , Xue Dai , Deng Zhaoxin , Mei Deqing
Published: July 2017

This paper develops a novel standing surface acoustic wave (SAW) device with three-pair of interdigital transducers (IDTs) to fabricate the patterned microstructure arrays with the assistance of ultraviolet (UV) polymerization. The working principle, structural design, and fabrication of the SAW device are presented. Then experimental setup was conducted to investigate the fabrication process and method of the patterned microstructure arrays on a thin liquid polymer surface. By adjusting the input wavelength and working voltage and selecting the pairs of IDTs, several types of patterned microstructure arrays, such as linear undulate and latticed undulate with different surface morphologies, could be fabricated. Results also demonstrated that the developed SAW device with the assistance of UV polymerization is an effective method to fabricate the patterned microstructure arrays, which may have great potential in the application of biomedical and microelectronic fields.
Experimental Characterization of the Interaction Between Carbon Fiber Composite Prepregs During the Preforming Process
Authors: Zhang Weizhao , Zhang Zixuan , Lu Jie , Wang Q. Jane , Su Xuming , Zeng Danielle , Mirdamadi Mansour , Cao Jian
Published: July 2017

Carbon fiber composites have received growing attention because of their high performance. One economic method to manufacturing the composite parts is the sequence of forming followed by the compression molding process. In this sequence, the preforming procedure forms the prepreg, which is the composite with the uncured resin, to the product geometry while the molding process cures the resin. Slip between different prepreg layers is observed in the preforming step and this paper reports a method to characterize the properties of the interaction between different prepreg layers, which is critical to predictive modeling and design optimization. An experimental setup was established to evaluate the interactions at various industrial production conditions. The experimental results were analyzed for an in-depth understanding about how the temperature, the relative sliding speed, and the fiber orientation affect the tangential interaction between two prepreg layers. The interaction factors measured from these experiments will be implemented in the computational preforming program.
Laser Sintering of Copper Nanoparticles: A Simplified Model for Fluence Estimation and Validation
Authors: Roy Nilabh , Jou William , Feng He , Jeong Jihoon , Wang Yaguo , Cullinan Michael
Published: July 2017

Copper (Cu) has already replaced aluminum as the primary material for interconnect fabrication due to its superior electrical and thermal conductivity. Low resistivity of Cu decreases the RC delay which in turn increases the integrated circuit (IC) speed. Copper nanoparticle (NP) inks can also serve as a promising replacement of silver NP inks in 2D printing applications on solid and flexible substrates. This paper presents a simplified model to estimate optimum laser sintering parameters of Cu NPs. The model is validated by the experimental sintering results using nanosecond and femtosecond pulsed lasers. The predicted sintering thresholds agree well with sintering experiments.
Towards Identifying the Elements of a Minimum Information Model for Use in a Model-Based Definition
Authors: Miller Alexander McDermott , Hartman Nathan W. , Hedberg Thomas , Barnard Feeney Allison , Zahner Jesse
Published: July 2017

The Model-Based Enterprise (MBE) paradigm is being adopted by manufacturing companies in a variety of industries. Companies benefit from enhanced visualization, documentation, and communication capabilities when 3D annotated product definitions, or Model-Based Definitions (MBD) replace two-dimensional drawings throughout an enterprise. It is critical that product information, much of which is defined implicitly in drawings, is not lost in this transition. This presents a challenge to authors and translators of 3D models used through the product lifecycle. They must understand the semantics of the product information typically presented by a drawing then explicitly include this information, in a computer-interpretable form, in the MBD.

The research study described in this paper seeks to discover what is the minimum set of required information to carry out all the tasks in a given workflow of a model-based enterprise. A survey was conducted across various industry sectors to identify the foundational elements of this Minimum Information Model (MIM) in selected workflows. This study identified the information used within the specific workflows, the capabilities of 3D CAD models to carry this information, and the implications for doing so.
Interlaminar Toughening of GFRP: Part 1 — Improved Diffusion and Precipitation
Authors: Bian Dakai , Beeksma Bradley R. , Shim D. J. , Jones Marshall , Yao Y. Lawrence
Published: July 2017

A low concentrated polystyrene (PS) additive to epoxy is used since it is able to reduce the curing reaction rate but not at the cost of increasing viscosity and decreasing glass transition temperature of the curing epoxy. The modified epoxy is co-cured with a compatible thermoplastic interleaf during the vacuum assisted resin transfer molding (VARTM) to toughen the interlaminar of the composites. Using viscometry, the solubilities of thermoplastics polycarbonate (PC), polyetherimide (PEI), and polysulfone (PSU) are determined to predict their compatibility with epoxy. The diffusion and precipitation process between the most compatible polymer PSU and epoxy formed semiinterpenetration networks (semi-IPN). To optimize bonding adhesion, these diffusion and precipitation regions were studied via optical microscopy under curing temperatures from 25 C to 120 C and PS additive concentrations to epoxy of 0% to 5%. Uniaxial tensile tests were performed to quantify the effects of diffusion and precipitation regions on composite delamination resistance and toughness. Crack paths were observed to characterize crack propagation and arrest mechanism. Fracture surfaces were examined by scanning electron microscopy (SEM) to characterize the toughening mechanism of the thermoplastic interleaf reinforcements. The chemically etched interface between diffusion and precipitation region showed semi-IPN morphology at different curing temperatures. Results revealed deeper diffusion and precipitation regions increases energy required to break semi-IPN for crack propagation resulting in crack arrests and improved toughness.
Product-Service Family Enabled Product Configuration System for Cloud Manufacturing
Authors: Yu Shiqiang , Zheng Pai , Yu Chunyang , Xu Xun
Published: July 2017

Rapid responsiveness to diverse customer needs is considered a competitive advantage in manufacturing business. To shrink the inquiry-to-order process, manufacturing firms will benefit a lot from building a product configuration system (PCS) which is the enabler of mass customisation (MC). PCS has matured in consumer businesses for decades but in capital goods industries, typically operating in engineer-to-order (ETO) manner, things differ a lot. It is for the reason that conventional PCS is incapable of extending customisation from order-delivery processes to the design/engineering phase. Cloud manufacturing, which is an emerging service-oriented manufacturing paradigms enabled by cyber-physical system, the Internet of Things and the Internet of Service, is promising to break the bottleneck of “ETO PCS” by the provision of technical infrastructure for product, service and data customisation. With the introducing of manufacturing-as-a-service (MaaS) concept, a product family is extended to a product-service family (PSF) in this paper for implementing in-depth product configuration process with scalable customisation depth (i.e., the degree of customisation freedom). Additionally, an approach of service delegation in product configuration process is proposed to support customer-centric product customisation. At last, the methodology proposed in this paper is validated by a case study in which the product configuration process of a complex ETO product is performed.
Effect of Arc-Current and Particle Morphology on Fracture Toughness of Plasma Sprayed Aluminium Oxide Coating
Authors: Kar Simanchal , Bandyopadhyay P. P. , Paul S.
Published: July 2017

Alumina powder was sprayed on low carbon steel substrate using atmospheric plasma spray process. Two different powders namely crushed and agglomerated powders were used and current was varied to study their effect on fracture toughness. Theoretically, with increase in arc current, melting of ceramic oxide shall increases and in turn dense coating should form. However, it was observed that if the arc power is too high and particle size of the powder being small (∼ 30 μm), the particles tend to fly away from the plasma core. Similarly, particle size distribution and powder morphology also affects the coating properties. Smaller particle should allow more melting resulting in dense coating and agglomerated powder allows flowability as well as better coating efficiency. Conversely, smaller particles tend to fly away from the plasma making the process difficult while the agglomerated particles showed a bimodal structure marked by presence of unmelted region in the splat core. All these factors lead to substantial variation in the fracture toughness of the coating. The present paper attempts to correlate plasma spraying parameters and microstructure of the coating with fracture toughness of the same.
An Experimental Method of Needle Deflection and Prostate Movement Using the Anatomically Accurate Prostate Simulator and the Electromagnetic Tracking System
Authors: Li Dian-Ru , Yeh Jih-Kai , Lin Wei-Chen , Montgomery Jeffrey S. , Shih Albert
Published: July 2017

This study develops an experimental method to measure the needle deflection and prostate movement using an anatomically accurate prostate simulator with the electromagnetic tracking (EMT) system. Accurate needle insertion is crucial for prostate biopsy to acquire the tissue samples from cancer sites identified by magnetic resonance imaging. False negatives or inability to diagnose are the clinical challenges in the biopsy procedure. The main cause is that the needle tip missed the targeted cancer sites due to needle deflection and prostate movement. An anatomically accurate prostate simulator was developed to quantitatively and experimentally measure the deviation of needle tip from the ideal path and the movement of a target point in the prostate. The EMT system was utilized to simultaneously track the needle tip and target point positions in 3D space. Results show that the maximal needle deflection occurred at the first 60-mm insertion with 6.7 and 0.7 mm in and perpendicular to the needle insertion plane, respectively. The corresponding target point movements were 6.5 mm and 2.4 mm in and perpendicular to the needle insertion plane, respectively. Differences between multiple insertions through the same path have also been quantified. This method can be utilized to study clinical prostate biopsy techniques, evaluate the accuracy of needle devices, and train clinicians for accurate prostate needle biopsy.
Process Effect on Part Surface Roughness in Powder-Bed Electron Beam Additive Manufacturing
Authors: Shrestha Subin , Chou Y. Kevin
Published: July 2017

Surface roughness is an inherent attribute of parts fabricated by Powder-Bed Electron Beam Additive Manufacturing (PB-EBAM) process. The wide application of PB-EBAM technology is affected by the part surface quality and therefore needs to be studied and optimized so as to establish PB-EBAM process among other manufacturing processes. Therefore, in this study, the build surface of fabricated parts built with different speed function (SF) is analyzed using white light interferometry. The results show that, in general the build surface roughness along the beam moving direction slightly increases with the scanning speed. On the other hand, the hatch spacing noticeably affects the surface roughness in the transverse direction. The experimentally acquired average surface roughness increased with increasing speed function from about 3 μm for SF20 case to 11 μm for SF65 case. In addition, a 3D VOF model has been attempted to predict the surface formation during the PB-EBAM process. Thus simulated SF36 case was able to predict different surface features and was in good agreement with experiment which shows that surface roughness analysis with numerical model may be a possible approach.
Overhang Support Structure Design for Electron Beam Additive Manufacturing
Authors: Cheng Bo , Chou Y. Kevin
Published: July 2017

Overhang structures are commonly found in Powder-bed metal additive manufacturing (AM) such as electron beam additive manufacturing (EBAM) process. The EBAM is assumed to build overhang structure without support features since powder bed could provide support. However, heat dissipation difference by sintered powder and solid substrate for overhang feature actually causes severe part distortion and requires support structure. Current support generation methods usually used certain types of structure to cover the overhang space. They may overestimate the support volume or put a large amount of supports, which could not be necessary and increase the post process time. Thus, the object of this task is to enhance the performance and efficient usage of the EBAM technology through effective support structure designs. In this study, a combined heat support and support anchor design method has been proposed. Numerical model has been used to evaluate stress and deformation during the design process. The detailed design process has been presented for a typical overhang and the simulation results have indicated that overhang deformation can be greatly reduced using this new method.
Investigation of Cellular Confinement in 3D Microscale Fibrous Substrates: Fabrication and Metrology
Authors: Tourlomousis Filippos , Boettcher William , Ding Houzhu , Chang Robert C.
Published: July 2017

Engineered microenvironments along with robust quantitative models of cell shape metrology that can decouple the effect of various well-defined cues on a stem cell’s phenotypic response would serve as an illuminating tool for testing mechanistic hypotheses on how stem cell fate is fundamentally regulated. As an experimental testbed to probe the effect of geometrical confinement on cell morphology, poly(ε-caprolactone) (PCL) layered fibrous meshes are fabricated with an in-house melt electrospinning writing system. Gradual confinement states of fibroblasts are demonstrated by seeding primary fibroblasts on defined substrates, including a classical two-dimensional (2D) petri dish and porous 3D fibrous substrates with microarchitectures tunable within a tight cellular dimensional scale window (1–50 μm). To characterize fibroblast confinement, a quantitative 3D confocal fluorescence imaging workflow for 3D cell shape representation is presented. The methodology advanced allows the extraction of cellular and subcellular morphometric features including the number, location, and 3D distance distribution metrics of the shape-bearing focal adhesion proteins.
Effects of Post Weld Heat Treatments (PWHT) on Friction Stir Welded AA2219-T87 Joints
Authors: Dewan Mohammad W. , Wahab Muhammad A. , Sharmin Khurshida
Published: July 2017

Friction Stir Welding (FSW) offers significantly better performance on aluminum alloy joints compared to the conventional fusion arc welding techniques; however, plastic deformation, visco-plastic flow of metals, and complex non-uniform heating cycles during FSW processes, result in dissolution of alloying elements, intrinsic microstructural changes, and post-weld residual stress development. As a consequence, about 30% reduction in ultimate strength (UTS) and 60% reduction in yield strength (YS) were observed in defect-free, as-welded AA2219-T87 joints. PWHT is a common practice to refine grain-coarsened microstructures which removes or redistributes post-weld residual stresses; and improves mechanical properties of heat-treatable welded aluminum alloys by precipitation hardening. An extensive experimental program was undertaken on PWHT of FS-welded AA2219-T87 to obtain optimum PWHT conditions and improvement of the tensile properties. Artificial age-hardening (AH) helped in the precipitation of supersaturated alloying elements produced around weld nugget area during the welding process. As a result, an average 20% improvement in YS and 5% improvements in UTS was observed in age-hardened (AH-170°C-18h) specimens as compared to AW specimens. To achieve full benefit of PWHT, solution-treatment followed by age-hardening (STAH) was performed on FS-welded AA2219-T87 specimens. Solution-treatment (ST) helps in the grain refinement and formation of supersaturated precipitates in aluminum alloys. Age-hardening of ST specimens help in the precipitation of alloying elements around grain boundaries and strengthen the specimens. Optimum aging period is important to achieve better mechanical properties. For FS-welded AA2219-T87 peak aging time was 5 hours at 170°C. STAH-170°C -5h treated specimens showed about 78% JE based on UTS, 61% JE based on yield strength, and 36% JE based on tensile toughness values of base metal.
Development of Laser Polishing As an Auxiliary Post-Process to Improve Surface Quality in Fused Deposition Modeling Parts
Authors: Perez Dewey Mario , Ulutan Durul
Published: July 2017

Laser polishing is a highly effective surface treatment process mainly used on metals and optical components, but it can also be used on plastic parts. It requires no manual labor, can be applied on parts of any size, and produces no hazardous or polluting substances on many plastic parts. Fused deposition modeling (FDM) is an additive manufacturing process in which parts are built by extruding thin layers of hot material through a nozzle. It has the advantage of producing complicated part geometries, and the possibility to change a design with no additional cost. This study investigates the use of laser polishing as an auxiliary post-process on Polylactic Acid (PLA) parts produced with FDM to improve the surface quality of final products. Although YAG lasers are commonly used in assisting metal machining processes, a CO2 laser was utilized in this study to post-process 3D-printed parts in order to reduce the staircase appearance. The main purpose of this study is to demonstrate that instead of reducing step size in 3D printing processes, it is possible to use bigger step sizes and laser treat the surface quickly afterwards to decrease the total process time while not compromising from surface quality. Laser speeds of 43–180 mm/s and laser powers of 0.75–3.75 W were tested on blocks of 3D-printed PLA with a parallelogram prism shape at 0.3 mm layer height. By varying laser speed and power, roughness reductions of up to 97% were achieved resulting in a uniform average surface roughness of 2.02 μm. This presents a fast, automatable, and inexpensive auxiliary post-process to FDM.
Bending Mechanism Analysis for Laser Forming of Metal Foam
Authors: Bucher Tizian , Young Adelaide , Zhang Min , Chen Chang Jun , Yao Y. Lawrence
Published: July 2017

To date, the industrial production of metal foam components has remained challenging, since few methods exist to manufacture metal foam into the shapes required in engineering applications. Laser forming is currently the only method with a high geometrical flexibility that is able to shape arbitrarily sized parts. What prevents the industrial implementation of the method, however, is that no detailed experimental analysis has been done of the metal foam strain response during laser forming, and hence the existing numerical models have been insufficiently validated. Moreover, current understanding of the laser forming process is poor, and it has been assumed, without experimental proof, that the temperature gradient mechanism (TGM) from sheet metal forming is the governing mechanism for metal foam.

In this study, these issues were addressed by using digital image correlation (DIC) to obtain in-process and post-process strain data that was then used to validate a numerical model. Additionally, metal foam laser forming was compared with metal foam 4-point bending and sheet metal laser forming to explain why metal foam can be bent despite its high bending stiffness, and to evaluate whether TGM is valid for metal foam.

The strain measurements revealed that tensile stretching is only a small contributor to foam bending, with the major contributor being compression-induced shortening. Unlike in sheet metal laser forming, this shortening is achieved through cell wall bending, as opposed to plastic compressive strains. Based on this important difference with traditional TGM, a modified temperature gradient mechanism (MTGM) was proposed.
Multi-Scale Stereolithography Using Shaped Beams
Authors: Mao Huachao , Leung Yuen-Shan , Li Yuanrui , Hu Pan , Wu Wei , Chen Yong
Published: July 2017

Current Stereolithography (SL) can fabricate three-dimensional (3D) objects in a single scale level, e.g. printing macro-scale or micro-scale objects. However, it is difficult for the SL printers to fabricate a 3D macro-scale object with micro-scale features. In the paper a novel SL-based multi-scale fabrication method is presented to address such a problem. The developed SL process can fabricate multi-scale features by dynamically changing the shape and size of a laser beam. Different shaped beams are realized by switching apertures with different micro-patterns. The laser beam without using any micro-patterns is used to fabricate the macro-scale features, while the shaped laser beams with smaller sizes are used to fabricate micro-patterned features. Accordingly, the tool path planning method for the multi-scale fabrication process are developed so that macro-scale and micro-scale features can be built by using different layer thicknesses, laser exposure time, and scanning paths. Compared with the conventional SL process based on a fixed laser beam size, our process can fabricate multi-scale features in a 3D object. It also has fast fabrication speed and good surface quality.
Simulations of Microstructure Evolution During Friction Stir Blind Riveting Using a Cellular Automaton Method
Authors: Samanta Avik , Shen Ninggang , Ji Haipeng , Wang Weiming , Ding Hongtao , Li Jingjing
Published: July 2017

Friction stir blind riveting (FSBR) is a novel and highly efficient joining technique for lightweight metal materials, such as aluminum alloys. The FSBR process induced large gradients of plastic deformation near the rivet hole surface and resulted in a distinctive gradient microstructure in this domain. In this study, microstructural analysis is conducted to analyze the final microstructure after the FSBR process. Dynamic recrystallization (DRX) is determined as the dominant microstructure evolution mechanism due to the significant heat generation during the process. To better understand the FSBR process, a two-dimensional Cellular Automaton (CA) model is developed to simulate the microstructure evolution near the rivet hole surface by considering the FSBR process loading condition. To model the significant microstructure change near the rivet hole surface, spatial distributed temporal thermal and mechanical loading conditions are applied to simulate the effect of the large gradient plastic deformation near the hole surface. The distribution grain topography and recrystallization fraction are obtained through the simulations, which agree well with the experimental data. This study presents a reliable numerical approach to model and simulate microstructure evolution governed by DRX under the large plastic deformation gradient in FSBR.
The Effects of Polarity and Current Path in Electrically Assisted Single Point Incremental Forming of 2024-T3 Aluminum
Authors: Grimm Tyler J. , Ragai Ihab , Roth John T.
Published: July 2017

Electrically assisted incremental sheet forming (EAIF) is a novel addition to the incremental forming (IF) method. One variation of this approach applies direct electrical current during forming. Many improvements over tradition IF can be seen by utilizing this method, to include greater part accuracy, reduced forming force, and greater formability.

In order to maximize the effects of electrically assisted incremental forming, all parameters of the method must be investigated, including the polarity of the current passing through the part and the path that the applied current takes. The effects of altering these two parameters is the primary investigation in this research.

It was determined that, in order to optimize springback reduction and formability during electrically assisted single point incremental forming, the tool should be assigned the positive electrode and the center of the workpiece should be assigned the negative electrode. Additionally, the mechanism behind the spalling effect inherent to EAIF is discussed.
Chatter Suppression in Parallel Turning With Unequal Pitch Using Observer Based Cutting Force Estimation
Authors: Sakata Shinya , Kadota Takashi , Yamada Yuki , Nakanishi Kenichi , Yoshioka Hayato , Suzuki Norikazu , Kakinuma Yasuhiro
Published: July 2017

Parallel turning attracts attention as one of the important technologies for the multi-tasking machine tools. This is because there is a potential to enhance the stability limits compared to turning operation using single tool when cutting conditions are properly selected. Although stability prediction models for parallel turning have been developed in recent years, in-process monitoring technique of chatter is almost out of focus.

In this study, to suppress chatter vibration, unequal pitch turning method was proposed. In this method, the upper tool was controlled based on optimum pitch angle calculated from spindle speed and chatter frequency. Chatter frequency was identified from estimated cutting force by disturbance observer. From the result of parallel turning test, it is clear that chatter vibration can be suppressed by controlling the upper tool based on optimum pitch angle.
Coolant Channel and Flow Characteristics of MQL Drill Bits: Experimental and Numerical Analyses
Authors: Kao Yi-Tang , Takabi Behrouz , Hu Mozheng , Tai Bruce L.
Published: July 2017

In minimum quantity lubrication (MQL) machining, mist flow plays a critical role in both lubrication and cooling. This paper aims to characterize the mist flow structure of different coolant channel designs for through-tool MQL drilling. Two different channel geometries (circular and triangular cross-section) and two sizes of each channel were selected for both experimental and computational analyses. The flow structure was captured by a high-speed camera and explained using computational fluid dynamics (CFD). The results showed that, for all the channel geometries, higher oil concentration was found close to the drill center. Specifically, in the triangular channel, the flow tends to accumulate at three corners. This study also measured the airspeed, which increased with the hydraulic diameter of the channel. These results have demonstrated the effects of channel geometry and the feasibility of using CFD in mist flow analysis.
A Modified Dynamic Programming Model in Condition-Based Maintenance Optimization
Authors: Xu Mengkai , Alam Md. Noor-E , Kamarthi Sagar
Published: July 2017

In condition-based maintenance, preventive replacement threshold and inspection scheme play important roles in maintenance performance. Major research considers cost as the main objective for measuring maintenance performance; here the average cost per unit time is used as the only objective in a single-unit system. The intention of this study was to investigate that how the average cost per unit time varies through changing replacement threshold and inspection scheme, the aim is to simultaneously determine an optimal replacement threshold and inspection scheme. The heterogeneity of hazard rate over stages of the equipment entails less frequent inspections when the equipment is at a healthy condition and more frequent inspections when the equipment is at a progressively deteriorated condition. Therefore the proposed condition-based inspection in the present work is non-periodic. A method based on dynamic programming is developed in order to implement a condition-based inspection scheme; furthermore the threshold for preventive replacement and the inspection scheme are simultaneously determined and then the optimal average maintenance cost is obtained.
Fabrication and Characterization of a Biocompatible Coating Formed on a Heat-Treated Magnesium Alloy Using Micro-Arc Oxidation
Authors: Ibrahim Hamdy , Elahinia Mohammad
Published: July 2017

The fast corrosion rate of magnesium (Mg) alloys is the main problem associated with the use of such biocompatible alloys for bone fixation applications. The corrosion resistance of Mg alloys can be improved by different post-fabrication processes such as heat treatment and coating. We have heat-treated a biocompatible Mg-1.2Zn-0.5Ca (wt.%) alloy at optimized heat treatment parameters to achieve the highest mechanical strength and corrosion resistance. Afterwards, the heat-treated alloy was coated with a ceramic layer using micro arc oxidation (MAO) process to further enhance the corrosion resistance.

The microstructure of the prepared samples was investigated using optical microscopy and scanning electron microscopy (SEM). The corrosion characteristics were determined by conducting in vitro electrochemical and immersion corrosion tests.

The results showed that the heat treatment process successfully improved the mechanical and corrosion properties of the Mg-1.2Zn-0.5Mn (wt.%) alloy. Both the in vitro electrochemical and immersion corrosion tests showed that the MAO-coated samples have a significantly higher corrosion resistance which results in a significantly lower corrosion rate. This study indicated that the biocompatible coating produced by MAO process may be suitable for providing heat-treated Mg-Zn-Ca-based alloys with protection from corrosion towards synthesizing bone fixation materials in clinical application.
Dynamic Electrical Impedance in Bipolar Tissue Welding
Authors: Li Xiaoran , Borduin Russell , Chen Roland , Li Wei
Published: July 2017

Bipolar tissue welding is a material joining process where high frequency alternating current is applied to biological tissue in medical procedures such as wound closure and blood vessel sealing. The process is often performed with a set of laparoscopic forceps in a minimal invasive surgery to achieve less bleeding and shorter recovery time. However, problems such as tissue sticking, thermal damage, and joint failure often occur and need to be solved before the process can be reliably used in more surgical procedures. In this study, experiments were conducted to investigate dynamic behavior of the tissue welding process through electrical impedance measurements. Both scissor-type and parallel electrodes were used with various compression and power settings in the experiment. It was found that the electrical impedance of tissue was lower when parallel electrodes were used. It can be used to understand the results and dynamic behavior of the tissue welding process, including the size of heat affected zone, tissue sticking, and the compression force effect.
One-dimensional hydroxyapatite materials: preparation and applications
Authors: Lu Bing-Qiang , Zhu Ying-Jie
Published: July 2017

As one of the biominerals, hydroxyapatite (HAP) plays important roles in biology, and inspires researchers to investigate HAP-based materials for the applications in various biomedical fields. Among them, one-dimensional (1-D) micro-/nanostructured HAP materials have attracted great interest in the last decades. This review summarizes the preparation and applications of 1-D HAP materials, and discusses different aspects of 1-D HAP materials. Various synthetic methods have been developed to prepare 1-D HAP materials with different morphologies, sizes, surface properties and crystallinities. In addition, elements-substituted 1-D HAP materials and composites have also been prepared. Surfactants and additives are usually adopted to control the nucleation and growth of 1-D HAP materials, but the related mechanisms are not very clear yet. The applications of 1-D HAP materials have been widely investigated, and the biomedical applications show great prospect but still need further improvements. A new kind of highly flexible fire-resistant inorganic paper made of ultralong HAP nanowires has been developed and is a promising alternative of the traditional cellulose paper for valuable archives and important documents. Regardless of the advances, further studies should be made for preparing 1-D HAP materials with controlled structures, sizes and morphologies and for boosting their various applications.
Do commercial fisheries display optimal foraging? The case of longline fishers in competition with odontocetes
Authors: Richard Gaëtan , Guinet Christophe , Bonnel Julien , Gasco Nicolas , Tixier Paul
Published: July 2017

Depredation in longline fisheries by odontocete whales is a worldwide growing issue, having substantial socioeconomic consequences for fishers as well as conservation implications for both fish resources and the depredating odontocete populations. An example of this is the demersal longline fishery operating around the Crozet Archipelago and Kerguelen Island, southern Indian Ocean, where killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) depredate hooked Patagonian toothfish (Dissostichus eleginoides). It is of great interest to better understand relationships of this modern fishery with its environment. Thus, we examined the factors influencing the decision-making process of fishers facing such competition while operating on a patch. Using optimal foraging theory as the underlying hypothesis, we determined that the probability captains left an area decreases with increasing fishing success, whereas in presence of competition from odontocete whales, it increases. Our study provides strong support that fishers behave as optimal foragers in this specific fishery. Considering that captains are optimal foragers and thus aim at maximizing the exploitation of the resources, we highlight possible risks for the long-term sustainability of the local ecosystems.
LEARNING TO INCENTIVIZE IN DIFFERENT MODES OF COORDINATION
Authors: WALL FRIEDERIKE
Published: July 2017

The paper studies which incentive systems emerge in organizations when self-interested managers collaboratively search for higher levels of organizational performance and the headquarters learn about the success of the incentive systems employed. The study uses an agent-based simulation and, in particular, controls for different levels of intra-organizational complexity and modes of coordination, i.e., the way how preferences on the departmental site are aligned with each other in respect to the overall organizational objective. The results indicate that for different levels of intra-organizational complexity different incentive systems emerge: With lower intra-organizational complexity, in tendency, the less focus is put on firm performance and vice versa. However, results also suggest that the mode of coordination may considerably affect the emergence of the incentive structure. This provides support for the idea that multiple management controls, like the incentive system and the mode of coordination, should be regarded and designed as a system with interrelations among its components and not just as a collection of several control practices.
Prediction Model of School Readiness
Authors: Suleiman Iyad , Arslan Maha , Alhajj Reda , Ridley Mick
Published: July 2017

Studying the school readiness is an interesting domain that has attracted the attention of the public and private sectors in education. Researchers have developed some techniques for assessing the readiness of preschool kids to start school. Here we benefit from an integrated approach which combines Data Mining (DM) and social network analysis towards a robust solution. The main objective of this study is to explore the socio-demographic variables (age, gender, parents' education, parents' work status, and class and neighbourhood peers influence), achievement data (Arithmetic Readiness, Cognitive Development, Language Development, Phonological Awareness), and data that may impact school readiness. To achieve this, we propose to apply DM techniques to predict school readiness. Real data on 306 preschool children was used from four different elementary schools: (1) Life school for Creativity and Excellence a private school located in Ramah village, (2) Sisters of Saint Joseph missionary school located in Nazareth, (3) Franciscan missionary school located in Nazareth and (4) Al-Razi public school located in Nazareth, and white-box classification methods, such as induction rules were employed. Experiments attempt to improve their accuracy for predicting which children might fail or dropout by first, using all the available attributes; next, selecting the best attributes; and finally, rebalancing data and using cost sensitive classification. The outcomes have been compared and the models with the best results are shown.
Ontology Based Arabic Opinion Mining
Authors: El-Halees Alaa , Al-Asmar Ahmed
Published: July 2017

In Arabic language, studies in the area of opinion mining are still limited compared to that being carried out in other languages. In this paper, we highlight the problem for Arabic opinion mining techniques when analysing reviews having different features with different opinion strengths. The traditional works of opinion mining consider all features extracted from the reviews to be equally important, so they fail to determine the correct opinion of the review and make the review's sentiment classification less accurate. This research presents a technique based on an ontology that uses feature level classification to classify Arabic user-generated reviews by identifying the relevant features from the review based on the degree of these features in the ontology tree. Then, we exploit the important features extracted to determine the overall polarity of the review. Moreover, summarisation for each feature is done to determine which feature has satisfied or dissatisfied customers. To evaluate our work, we use public datasets which are hotels and books datasets. We used [Formula: see text]-measure metrics to assess the performance and compare the results with other supervised and unsupervised techniques. Also, subjective evaluation is used in our method to demonstrate the effectiveness of feature and opinion extraction process and summarisation. We show that our method improves the performance compared with other opinion mining classification approaches, obtaining 78.83% [Formula: see text]-measure in hotels domain and 79.18% in books domain. Furthermore, the subjective evaluation shows the effectiveness of our method by getting an average [Formula: see text]-measure of 84.62% in hotels dataset and 86.31% in books dataset.
Multi-indicator Evaluation and Analysis of Coordinated Industrial Development of Urban Agglomerations
Authors: SUN Xuan
Published: July 2017

The level of coordinated industrial development in a region is considered as an important factor of measuring the construction of urban agglomerations. As the economic development patterns and stages vary in regions, a single-standard evaluation system is generally insufficient in evaluating and analyzing the coordinated industrial development of urban agglomerations. This paper, with multivariate values and diversified development demands considered, quantitatively describes the industrial development of urban agglomerations from four dimensions: economics, specialization, balance, and friendliness. On this basis, it synthesizes the indicator parameters effectively and proposes a multi-indicator evaluation model. Through the model, the paper comparatively analyzes the present status and development course of coordinated industrial development of typical urban agglomerations (Beijing–Tianjin–Hebei urban agglomeration, the Yangtze River Delta urban agglomeration, and the Pearl River Delta urban agglomeration) in China. The results show that Beijing–Tianjin–Hebei urban agglomeration has the clearest division of industries, but its industrial spillover effect is limited, the industrial structure of small and medium cities is too simple, and the economic gap among cities narrows at a very slow rate. The core cities in the Yangtze River Delta urban agglomeration exert certain driving effect upon the economy of their surrounding areas. However, they hardly give full play to their comparative advantages due to a low level of regional integration and high industrial similarity among cities. Compared with the above two urban agglomerations, the Pearl River Delta urban agglomeration enjoys more reasonable division of industries among cities, significant driving effect of core cities, and higher level of coordinated industrial development as driven by the market economy.
G20 and the Reform of Global Energy Governance
Authors: Yu Hongyuan
Published: July 2017

Due to institutional fragmentation and conflicts among various actors, a systematic reform to improve the effectiveness of the global energy governance system has become increasingly urgent. Currently, the Group of Twenty (G20), which consists of the world’s major economies and constitutes 60 percent of global energy trade, is in a good position to remold the global framework for energy governance. The past G20 summit meetings have witnessed more attention and efforts from member-state leaders to address problems associated with global energy. However, most of the discussion has been focused on technical issues rather than a comprehensive review of the whole governance system. In the future, the G20 should take proactive measures to enhance its leadership role and policy innovation in the reform of global energy governance, in order to spur green development of the world. As the largest developing nation, China should tap into the G20 platform to advance the transformation of its domestic and international energy systems.
The Quest for Global Leadership: U.S.-China Competition in Multilateral Financial Institutions
Authors: Kapur Devesh
Published: July 2017

As China emerges as a global power, it has showed great willingness to remake global development finance by setting up new multilateral financial institutions. The creation of those new institutions represents a marked departure from the existing multilateral development bank (MDB) system. For the first time, the new institutions do not depend on the financial largess of the West. To understand the circumstances that have led China to create these new institutions and the likely consequences, the article first examines the Bretton Woods institutional architecture that was created by the United States when it emerged as the principal global economic superpower in the aftermath of World War II. In the second part, it analyzes the competition between China and the United States in global financial governance given Beijing’s expanding interests and Washington’s declining influence. The article further explores in the third section new opportunities and challenges that the new financial institutions could bring to China, and finally proposes how China could better leverage those new institutions to play a transformative role in promoting its global leadership.
Rating Effects on Social News Posts and Comments
Authors: Glenski Maria , Weninger Tim
Published: July 2017

At a time when information seekers first turn to digital sources for news and opinion, it is critical that we understand the role that social media plays in human behavior. This is especially true when information consumers also act as information producers and editors through their online activity. In order to better understand the effects that editorial ratings have on online human behavior, we report the results of a two large-scale in vivo experiments in social media. We find that small, random rating manipulations on social media posts and comments created significant changes in downstream ratings, resulting in significantly different final outcomes. We found positive herding effects for positive treatments on posts, increasing the final rating by 11.02% on average, but not for positive treatments on comments. Contrary to the results of related work, we found negative herding effects for negative treatments on posts and comments, decreasing the final ratings, on average, of posts by 5.15% and of comments by 37.4%. Compared to the control group, the probability of reaching a high rating ( ⩾ 2,000) for posts is increased by 24.6% when posts receive the positive treatment and for comments it is decreased by 46.6% when comments receive the negative treatment.
Exploring and Analyzing the Tor Hidden Services Graph
Authors: Bernaschi Massimo , Celestini Alessandro , Guarino Stefano , Lombardi Flavio
Published: July 2017

The exploration and analysis of Web graphs has flourished in the recent past, producing a large number of relevant and interesting research results. However, the unique characteristics of the Tor network limit the applicability of standard techniques and demand for specific algorithms to explore and analyze it. The attention of the research community has focused on assessing the security of the Tor infrastructure (i.e., its ability to actually provide the intended level of anonymity) and on discussing what Tor is currently being used for. Since there are no foolproof techniques for automatically discovering Tor hidden services, little or no information is available about the topology of the Tor Web graph. Even less is known on the relationship between content similarity and topological structure. The present article aims at addressing such lack of information. Among its contributions: a study on automatic Tor Web exploration/data collection approaches; the adoption of novel representative metrics for evaluating Tor data; a novel in-depth analysis of the hidden services graph; a rich correlation analysis of hidden services’ semantics and topology. Finally, a broad interesting set of novel insights/considerations over the Tor Web organization and content are provided.