bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbocharging Practical Implications in Management Studies
Authors: Simsek Zeki , Li Ning , Huang Jason L.
Published: August 2021

This is the second editorial commentary in a three-part series that addresses introductions, implications, and interestingness. The first, focusing on the introduction design, is about what the beginning of a paper should look like. The second, focusing on practice implications, is about what the end of a paper should look like. The third discusses how to develop and fit attention-grabbing ideas into the academic conversation in the literature. We hope this editorial series provides inspiration and ideas about publishing papers that people want to engage with.
Neighborhoods, Racism, Stress, and Preterm Birth Among African American Women: A Review
Authors: C. Giurgescu , D.P. Misra , J.C. Slaughter-Acey , S.L. Gillespie , A.L. Nowak , E. Dove-Medows , C.G. Engeland , S.N. Zenk , T.A. Lydic , S. Sealy-Jefferson , J. Ford , S. Drury , P. Stemmer
Published: August 2021

African American women are more likely to experience preterm birth (<37 completed weeks gestation) compared with White women. African American women are also more likely to live in neighborhoods characterized as disadvantaged (i.e., exhibiting higher rates of vacant housing, poorer property conditions, and more litter and crime) and to experience racial discrimination compared with White women. These chronic stressors have been related to preterm birth (PTB) among African American women. This review focuses on potential stress-related pathways by which neighborhood disadvantage and racial discrimination increase the risk for PTB among African American women. Specifically, we propose cortisol, systemic inflammation, proteome and lipidome profiles, and telomere shortening as potential mediators linking these social determinants of health with PTB among African American women. Examination of these factors and the signaling pathways they contribute to will increase our knowledge of the effects of social determinants of health on PTB for African American women.
How A Social Enterprise Wanes: The Transaction Costs of Credible Commitments at Etsy.com
Authors: Agafonow Alejandro , Perez Marybel
Published: August 2021

This article fathoms how a social enterprise wanes by applying the construct of imperative credible commitments from transaction cost economics to the case of Etsy.com, an online marketplace created to connect artisans and craftwork enthusiasts. In the absence of imperative credible commitments, Etsy’s social mission was bound to change, leaving the company’s major stakeholders without safeguards to protect the perpetuation of the transactions that Etsy was created to serve. The construct of credible commitments has proved to be fertile in understanding issues of political and economic transition, yet its relevance to puzzle out the corporate world has been underestimated. To bridge this gap, we have recourse to the analogy between disabling the discretion of monarchs and executives to prevent them from reneging on commitments. Hence, by building on political economy academics’ attention is drawn to strategies that, despite existing in the corporate world, have rarely been perceived as important by management and economics scholars.
The State, Business and Corporate Social Responsibility in India
Authors: John Kishore Thomas
Published: August 2021

Prabhakaran Paleri, Corporate Social Responsibility: Concepts, Cases and Trends (New Delhi: Cengage Limited, 2020), xx + 443 pp.
Inclusive innovation editorial: The promise of inclusive innovation
Authors: Schrock Greg , Nichola Lowe
Published: August 2021

Innovation is an elusive concept that is widely viewed as a panacea for economic renewal. Public-sector institutions invest heavily in innovation even as private-sector actors and interests dominate innovation policy and its rewards, especially at the local scale. But in a moment when planners and policy makers are under pressure to promote economic inclusion, we must also ponder the prospects for innovation to be inclusive and equitable. In this opening editorial to this special issue on “Inclusive Innovation,” we sketch out a tentative vision for “inclusive innovation” beginning with the problems that can lead innovation to instead be exclusive and unequal. We conclude by summarizing the contributions of the authors to this special issue, which underscore not only the diverse dimensions of inclusive innovation but also the critical importance of policy-led institutions to facilitate this goal.
Trends in quality of care and dying perceived by family caregivers of nursing home residents with dementia 2005–2019
Authors: Klapwijk Maartje S , Bolt Sascha R , Boogaard Jannie A , ten Koppel Maud , Gijsberts Marie-José HE , van Leussen Carolien , The B. Anne-Mei , Meijers Judith MM , Schols Jos MGA , Pasman H Roeline W , Onwuteaka-Philipsen Bregje D , Deliens Luc , Van den Block Lieve , Mertens Bart , de Vet Henrica CW , Caljouw Monique AA , Achterberg Wilco P , van der Steen Jenny T
Published: August 2021

Background:

Dementia palliative care is increasingly subject of research and practice improvement initiatives.

Aim:

To assess any changes over time in the evaluation of quality of care and quality of dying with dementia by family caregivers.

Design:

Combined analysis of eight studies with bereaved family caregivers’ evaluations 2005–2019.

Setting/participants:

Family caregivers of nursing home residents with dementia in the Netherlands ( n = 1189) completed the End-of-Life in Dementia Satisfaction With Care (EOLD-SWC; quality of care) and Comfort Assessment in Dying (EOLD-CAD, four subscales; quality of dying) instruments. Changes in scores over time were analysed using mixed models with random effects for season and facility and adjustment for demographics, prospective design and urbanised region.

Results:

The mean total EOLD-SWC score was 33.40 (SD 5.08) and increased by 0.148 points per year (95% CI, 0.052–0.244; adjusted 0.170 points 95% CI, 0.055–0.258). The mean total EOLD-CAD score was 30.80 (SD 5.76) and, unadjusted, there was a trend of decreasing quality of dying over time of −0.175 points (95% CI, −0.291 to −0.058) per year increment. With adjustment, the trend was not significant (−0.070 EOLD-CAD total score points, 95% CI, −0.205 to 0.065) and only the EOLD-CAD subscale ‘Well being’ decreased.

Conclusion:

We identified divergent trends over 14 years of increased quality of care, while quality of dying did not increase and well-being in dying decreased. Further research is needed on what well-being in dying means to family. Quality improvement requires continued efforts to treat symptoms in dying with dementia.
Effect of Superstitious Beliefs and Risk Intuitions on Genetic Test Decisions
Authors: Riley Kristen E. , Sussman Andrew L. , Schofield Elizabeth , Guest Dolores D. , Dailey Yvonne T. , Schwartz Matthew R. , Buller David B. , Hunley Keith , Kaphingst Kimberly A. , Berwick Marianne , Hay Jennifer L.
Published: August 2021

Introduction

Moving beyond numeric representations of risk perceptions, we examine cognitive causation, or superstitious thinking, and negative affect in risk as predictors of MC1R (i.e., moderate v. high risk) skin cancer genetic testing and responses to this testing.

Methods

Participants ( N = 496) completed baseline assessments using validated measures of cognitive causation (beliefs that thinking about cancer risk increases cancer likelihood) and negative affect in risk (negative feelings generated during risk perception) and subsequently received a test offer. Participants could access a website to learn about and request genetic testing. Those who tested ( n = 167) completed assessments of cognitive and affective reactions 2 wk after testing, including the Impact of Events–Revised Intrusive thoughts subscale.

Results

Those with higher negative affect in risk were less likely to return a saliva sample for testing (odds ratio = 0.98, 95% confidence interval = 0.96–0.99). Those with higher cognitive causation reported more fear ( b = 0.28–0.31; P’s < 0.05). Higher negative affect in risk was associated with more emotion-laden test responses, particularly in those receiving higher-risk as compared with average-risk results.

Conclusion

Negative affect in risk did not hamper test information seeking, although it did inhibit the uptake of genetic testing. Those with higher cognitive causation showed more fear regarding their test result, as indicated by higher distress in those who received average-risk results and lower believability in those who received higher-risk results.
Learning reward functions from diverse sources of human feedback: Optimally integrating demonstrations and preferences
Authors: Bıyık Erdem , Losey Dylan P. , Palan Malayandi , Landolfi Nicholas C. , Shevchuk Gleb , Sadigh Dorsa
Published: August 2021

Reward functions are a common way to specify the objective of a robot. As designing reward functions can be extremely challenging, a more promising approach is to directly learn reward functions from human teachers. Importantly, data from human teachers can be collected either passively or actively in a variety of forms: passive data sources include demonstrations (e.g., kinesthetic guidance), whereas preferences (e.g., comparative rankings) are actively elicited. Prior research has independently applied reward learning to these different data sources. However, there exist many domains where multiple sources are complementary and expressive. Motivated by this general problem, we present a framework to integrate multiple sources of information, which are either passively or actively collected from human users. In particular, we present an algorithm that first utilizes user demonstrations to initialize a belief about the reward function, and then actively probes the user with preference queries to zero-in on their true reward. This algorithm not only enables us combine multiple data sources, but it also informs the robot when it should leverage each type of information. Further, our approach accounts for the human’s ability to provide data: yielding user-friendly preference queries which are also theoretically optimal. Our extensive simulated experiments and user studies on a Fetch mobile manipulator demonstrate the superiority and the usability of our integrated framework.
Differences in the Ageing Behavior of Asphalt Pavements with Porous and Stone Mastic Asphalt Mixtures
Authors: Jing Ruxin , Varveri Aikaterini , Liu Xueyan , Scarpas Athanasios , Erkens Sandra
Published: August 2021

The degradation of bituminous materials as a result of ageing has a significant effect on asphalt pavement performance. In this study, one porous asphalt (PA) section and one stone mastic asphalt (SMA) asphalt pavement section were designed and constructed in 2014 and exposed to the actual environmental condition. To study the change in the pavement’s mechanical properties, asphalt cores were collected from both test sections annually. The change in stiffness modulus was determined via cyclic indirect tensile tests. To investigate the ageing behavior across the pavement depth, the bitumen was extracted and recovered from 13 mm slices along the depths of the cores. The chemical composition and rheological properties of the field-recovered bitumen, and that of original bitumen aged in standard short- and long-term ageing protocols, were investigated by means of the Fourier Transform Infrared (FTIR) spectrometer and Dynamic Shear Rheometer. The results show that the effect of mineral aggregate packing, and therefore of air-void distribution and connectivity, on the ageing sensitivity of the pavements with time was significant, as the changes in the stiffness of the PA mixture were greater than that of SMA mixture. In addition, the results of field-recovered bitumen show that there is an ageing gradient inside the porous asphalt layer, however, the ageing of SMA mainly happens on the surface of the layer. Finally, the field-recovered and laboratory-aged bitumen results demonstrate a weak relation between field and standard laboratory ageing protocols.
Characterization of Mellowing Process to Control Expansion in High-Sulfate-Bearing Soil
Authors: Shon Chang-Seon , Scullion Tom , Blackmon Wade , Zhang Dichuan , Kim Jong Ryeol
Published: August 2021

Calcium-based stabilizing materials (CBSMs) such as lime and fly ash are extensively used in subgrade primarily to enhance mechanical strength and improve resistance to chemical attack, resulting in more durable roadway. The soluble sulfate phase contained in some soils, however, can react with CBSMs and form ettringite minerals. If the soil is compacted before the end of this reaction, large, unstable, and volumetric swelling can occur. Among several methods to control sulfate-induced swelling, a “mellowing” approach is typically used because of its efficient, economical, and practical benefits when dealing with calcium-based stabilization of soils with significant soluble sulfate contents. Although the mellowing method is one of the frequently used methods, little data is available on the characterization of the specified mellowing process in the high-sulfate-bearing soil during the mellowing period. A research program investigated key factors influencing the mellowing process during the mellowing period, explaining how stabilizer type and content, remixing interval, mellowing period, and temperature play a role in reducing soluble sulfate content. Moreover, for selected mixtures, the 3-dimensional volumetric expansion and retained strength were measured after the mellowing process. Laboratory test results have revealed that a single mellowing process with higher lime content and daily remixing at high temperature leads to the rapid reduction of sulfate content in the soil. Moreover, after the mellowing process, additional soil treatment with fly ash or a combination of lime and fly ash leads to lower expansion and higher retained unconfined compressive strength of the soil mixture.
Localization of Relevant Urban Micro-Consolidation Centers for Last-Mile Cargo Bike Delivery Based on Real Demand Data and City Characteristics
Authors: Rudolph Christian , Nsamzinshuti Alexis , Bonsu Samuel , Ndiaye Alassane Ballé , Rigo Nicolas
Published: August 2021

The use of cargo cycles for last-mile parcel distribution requires urban micro-consolidation centers (UMC). We develop an approach to localize suitable locations for UMCs with the consideration of three criteria: demand, land use, and type of road. The analysis considers metric levels (demand), linguistic levels (land use), and cardinal levels (type of road). The land-use category is divided into commercial, residential, mixed commercial and residential, and others. The type of road category is divided into bicycle road, pedestrian zone, oneway road, and traffic-calmed road. The approach is a hybrid multi-criteria analysis combining an Analytical Hierarchical Process (AHP) and PROMETHEE methods. We apply the approach to the city center of Stuttgart in Germany, using real demand data provided by a large logistics service provider. We compared different scenarios weighting the criteria differently with DART software. The different weight allocation results in different numbers of required UMCs and slightly different locations. This research was able to develop, implement, and successfully apply the proposed approach. In subsequent steps, stakeholders such as logistics companies and cities should be involved at all levels of this approach to validate the selected criteria and depict the “weight” of each criterion.
Mitigating Increased Driving after the COVID-19 Pandemic: An Analysis on Mode Share, Travel Demand, and Public Transport Capacity
Authors: Ciuffini Francesca , Tengattini Simone , Bigazzi Alexander York
Published: August 2021

Reduced transit capacity to accommodate social distancing during the COVID-19 pandemic was a sudden constraint that along with a large reduction in total travel volume and a shift in activity patterns contributed to abrupt changes in transportation mode shares across cities worldwide. There are major concerns that as the total travel demand rises back toward prepandemic levels, the overall transport system capacity with transit constraints will be insufficient for the increasing demand. This paper uses city-level scenario analysis to examine the potential increase in post-COVID-19 car use and the feasibility of shifting to active transportation, based on prepandemic mode shares and varying levels of reduction in transit capacity. An application of the analysis to a sample of cities in Europe and North America is presented. Mitigating an increase in driving requires a substantial increase in active transportation mode share, particularly in cities with high pre-COVID-19 transit ridership; however, such a shift may be possible based on the high percentage of short-distance motorized trips. The results highlight the importance of making active transportation attractive and reinforce the value of multimodal transportation systems as a strategy for urban resilience. This paper provides a strategic planning tool for policy makers facing challenging transportation system decisions in the aftermath of the COVID-19 pandemic.
Character Growth Following Collective Life Events: A Study on Perceived and Measured Changes in Character Strengths During the First Wave of the COVID-19 Pandemic
Authors: Gander Fabian , Wagner Lisa
Published: August 2021

Did the COVID-19 pandemic promote character growth? Studies using sequential samples suggest that collective life events can result in character growth, but their conclusions have been questioned. This study used three approaches to examine character growth during the first wave of the pandemic: perceived changes in oneself and in a close other, and a longitudinal analysis of changes. In addition, we tested whether character strengths assessed before the pandemic predicted specific instances of growth, that is, engagement in volunteering and compliance with regulations during the pandemic. German-speaking participants ( N = 366, 76.5% female, mean age: 45.33 years) who had completed an assessment of character strengths before the pandemic reported on perceived changes in character strengths, engagement in volunteering, and compliance with regulations. A subsample also completed a second assessment of character strengths. The results showed that (a) participants reported perceived changes for most character strengths in both themselves and close others, while (b) longitudinal increases were only observed for humility and prudence. Pre-pandemic character strengths predicted (c) engagement in volunteering and (d) compliance with regulations. We conclude that actual character growth was smaller than the perceived changes but that the character strengths did predict relevant behaviors related to the COVID-19 pandemic.
High-temperature PMIA dielectric composites with enhanced thermal conductivity utilizing functionalized BaTiO3 nanowires–carbon nanotubes fillers
Authors: Duan Guangyu , Hu Fengying , Xin Zhongyuan , Chi Changlong , Yu Xiang
Published: August 2021

This study reports that a novel high-temperature poly (m-phenyleneisophthalamide) (PMIA) composite with enhanced dielectric constant and thermal conductivity was prepared by filling with BaTiO3 nanowires–carbon nanotubes (BTCNs) fillers. Due to effective functionalization of BaTiO3 nanowires (BTNWs) and multi-wall carbon nanotubes (MWCNTs), the fabricated BTCNs fillers were homogeneously dispersed in PMIA matrix. The consequence displays that the dielectric constant of PMIA composite with 15 wt % BTNWs fillers increases to 27.6 at 103 Hz, which is about nine times higher than that of pure PMIA. Moreover, owing to the high thermal conductivity of MWCNTs, the thermal conductivity of PMIA with 15 wt% BTNWs fillers increases to 1.01 W/(mK). The enhanced thermal conductivity is beneficial for BTCNs/PMIA composite to dissipate the generated heat by dielectric loss. Considering these merits, this research would provide new methods and ideas for preparation of high-temperature dielectric polymer composites and reducing the internal thermal effect.
Design optimization of a fluidized bed with a novel air chamber using the CFD-Taguchi method
Authors: Wang Fei , Yan Hao , Zeng Yishan , Xu Wei , Zang Haozhou , Meng Jian
Published: August 2021

The gas–solid fluidized bed is the key structure of industrial fluidization, and it is widely used in fields such as chemical reactors and industrial material conveying. To study the uniformity of velocity distribution ( Vu) in a fluidized bed and clarify the interaction mechanism between the geometric structure of the air chamber and the gas flow, in this paper, 16 novel chamber structures for powder unloading were designed based on the Taguchi method. Computational fluid dynamics was used to simulate the different chamber schemes, and the effects of various geometric factors on the response were analyzed based on the Taguchi method. The effect of the novel optimization model for powder unloading was verified by tests. The results show that the optimal combination of geometrical parameters is air chamber capacity ( V) at level 4, separation ratio ( K) at level 1 and clearance of splitter plate ( δ) at level 1, and δ has the greatest effect on the Vu1 and Vu2 in the fluidized bed. With the increase in δ and K, the velocity of the airflow away from the inlet side increases, and the area of the vortex near the splitter plate increases. Compared with the baseline model, the fluidized bed with the novel air chamber can effectively reduce the residual rate of powder unloading.
Numerical simulation on hydraulic performance and tip leakage vortex of a slanted axial-flow pump with different blade angles
Authors: Fei Zhaodan , Xu Hui , Zhang Rui , Zheng Yuan , Mu Tong , Chen Yaohui
Published: August 2021

The blade angle has a great effect on hydraulic performance and internal flow field for axial-flow pumps. This research investigated the effect of the blade angle on hydraulic performance and tip leakage vortex (TLV) of a slanted axial-flow pump. The hydraulic performance and the TLV are compared with different setting angles. The dimensionless turbulence kinetic energy (TKE) is used to investigate the TLV. A novel variable fv is utilized to analyze the relation among the TLV, strain tensor and vorticity tensor. The proper orthogonal decomposition (POD) method is used to analyze TLV structure. The results show that with the increase of the blade angle, the pump head is getting larger, the flow rate of the best efficiency moves to be larger, and both the primary TLV (P-TLV) and the secondary TLV (S-TLV) are getting stronger. The P-TLV often exists in the outer edge of TKE distribution and S-TLVs often exist in the largest value area of TKE. This phenomenon is more evident with blade angle increasing. Through POD method, it shows that the first six modes contain more than 90% of TKE. The reason why the TKE value near the region of S-TLV is high is that the tip leakage flow is a kind of jet-like flow with high kinetic energy. The main structure of the P-TLV is shown in modes 4−6, resulting in a reflux zone but not with the highest TKE.
Design, analysis, control simulation, and experiment of novel electromagnetic hybrid vibration absorber
Authors: Song Chunsheng , Xu Binghui , Fan Xuefeng , Yang Pengfei , Duan Ruirui
Published: August 2021

This paper presents a novel type of electromagnetic hybrid vibration absorber (EHVA) with a double-ring series permanent magnetic circuit applied to improve the two-stage vibration isolation system of marine power machinery. The EHVA comprises a mover with several groups of coils having a series connection, as well as a stator with internal permanent magnets and external permanent magnets, which form a novel magnetic circuit structure based on an improved Halbach array. In this magnet circuit, two adjacent groups of magnetic induction lines overlap at the coil position, thereby strengthening the magnetic field intensity. When the mover moves axially, the coil cuts the magnetic induction line to produce Lorentz force and magnetic damping force. First, the dynamic parameters of the EHVA were calculated based on multi-rigid-body dynamic theory and fixed-point theory. Second, the mechanical and electromagnetic structures of the EHVA were designed. Finally, a test stand was constructed, the system control channel was identified, and the simulation as well as experiment for vibration control using an [Formula: see text] controller were performed. Results indicated that the hybrid vibration reduction system under control reduced the acceleration amplitude by 12.3 dB at 30.6 Hz and achieved better vibration absorption effects between 27 and 33 Hz compared with the uncontrolled system.
Effect of intra-yarn hybridisation and fibre architecture on the impact response of composite laminates: Experimental and numerical analysis
Authors: Dalfi Hussein
Published: August 2021

Advanced composite laminates (i.e. glass composite laminates) are highly susceptible to low velocity impact, and the induced damage failures substantially reduced their residual mechanical properties and safe-service life during their application. Therefore, experiments and simulation efforts to predict their low-velocity impact damages and energy absorbing have significant importance in composite structures design. In this regards, experimental and finite element analysis (FEA) with aiding Abaqus software were respectively performed to investigate the influence of yarn hybridisation on the response of composite laminates under low velocity impact. The hybrid yarns, which consisted of S-glass and polypropylene yarns have been used to manufacture two types of composites; non-crimp cross-ply hybrid yarns and twill hybrid fabric composites. Additionally, for comparison, the non-crimp cross-ply and twill fabric composite laminates have been made from glass fibres only. The vacuum infusion resin process has been adopted to manufacture these composite laminates. The impact performance of composite laminates has been investigated using low-velocity impact at 15 J, 35, and 50 impact energy levels. The numerical analysis was executed using Abaqus/Explicit and Hashin failure criteria and continuum damage mechanics by using homogenous shell were adopted to simulate the intra-laminar damage in layers. Meanwhile, standard cohesive inter-laminar interfaces that inserted between composite layers with quadratic stress failure criteria have been used to model delamination failures. The numerical results regarding impact force-time, displacement–time and energy-time histories plots, as well as the damage evolution behaviour of matrix crack and fibre fracture, presented an agreement with experimental results.
Effect of nonlinear edge loads and hybridization of FMLs on buckling performance of interlaminar composites with/without cutouts
Authors: Muddappa Yathish PP , Rajanna T , Giridhara G
Published: August 2021

The solution for the buckling problems of fibre metal laminates is usually based on the assumptions that the plates are subjected to uniform edges loads without any discontinuity or damages. Nevertheless, in practice the plates are subjected to various kinds of nonlinear/nonuniform edge loads along with various sized and positioned openings. The present work mainly focused on the vibration and buckling performance of inter laminar hybrid fiber metal laminates (HFMLs) with and without cutouts subjected to different kinds of nonlinear loading conditions by utilizing finite element approach. Towards this a 9-noded heterosis plate element has been used to discretize the plate by taking into account the effect of shear deformation and rotary inertia. Since the stress distribution within the plate is highly non-uniform in nature, the dynamic approach has been used to solve the buckling problems. The present study consists of aluminum metal face sheets bonded with four layered symmetric hybrid cross-ply laminates, in which six different hybrid configurations have been considered. The performance of each hybrid configuration along with different sized and positioned cutouts is well investigated under various nonlinear loading conditions.
Comparative assessment between AlTiN and AlTiSiN coated carbide tools towards machinability improvement of AISI D6 steel in dry hard turning
Authors: Das Anshuman , Kamal Miyaz , Das Sudhansu Ranjan , Patel Saroj Kumar , Panda Asutosh , Rafighi Mohammad , Biswal Bibhuti Bhushan
Published: August 2021

AISI D6 (hardness 65 HRC) is one of the hard-to-cut steel alloys and commonly used in mould and die making industries. In general, CBN and PCBN tools are used for machining hardened steel but its higher cost makes the use for limited applications. However, the usefulness of carbide tool with selective coatings is the best substitute having comparable tool life, and in terms of cost is approximately one-tenth of CBN tool. The present study highlights a detailed analysis on machinability investigation of hardened AISI D6 alloy die steel using newly developed SPPP-AlTiSiN coated carbide tools in finish dry turning operation. In addition, a comparative assessment has been performed based on the effectiveness of cutting tool performance of nanocomposite coating of AlTiN deposited by hyperlox PVD technique and a coating of AlTiSiN deposited by scalable pulsed power plasma (SPPP) technique. The required number of machining trials under varied cutting conditions (speed, depth of cut, feed) were based on L16 orthogonal array design which investigated the crater wear, flank wear, surface roughness, chip morphology, and cutting force in hard turning. Out of the two cutting tools, newly-developed nanocomposite (SPPP-AlTiSiN) coated carbide tool promises an improved surface finish, minimum cutting force, longer tool life due to lower value of crater & flank wears, and considerable improvement in tool life (i.e., by 47.83%). At higher cutting speeds, the crater wear length and flank wear increases whereas the surface roughness, crater wear width and cutting force decreases. Chip morphology confirmed the formation of serrated type saw tooth chips.
Size-dependent vibration of functionally graded rotating nanobeams with different boundary conditions based on nonlocal elasticity theory
Authors: Fang Jianshi , Yin Bo , Zhang Xiaopeng , Yang Bin
Published: August 2021

The free vibration of rotating functionally graded nanobeams under different boundary conditions is studied based on nonlocal elasticity theory within the framework of Euler-Bernoulli and Timoshenko beam theories. The thickness-wise material gradient variation of the nanobeam is considered. By introducing a second-order axial shortening term into the displacement field, the governing equations of motion of the present new nonlocal model of rotating nanobeams are derived by the Hamilton’s principle. The nonlocal differential equations are solved through the Galerkin method. The present nonlocal models are validated through the convergence and comparison studies. Numerical results are presented to investigate the influences of the nonlocal parameter, angular velocity, material gradient variation together with slenderness ratio on the vibration of rotating FG nanobeams with different boundary conditions. Totally different from stationary nanobeams, the rotating nanobeams with relatively high angular velocity could produce larger fundamental frequencies than local counterparts. Additionally, the axial stretching-transverse bending coupled vibration is perfectly shown through the frequency loci veering and modal conversion.
Experimental investigation on thermal behavior of non-boiling slug and bubbly two phase-flow in helical tube with spiral
Authors: Rezazadeh Reza , Jafarmadar Samad , Khorasani Saleh , Niaki Seyed Reza Amini
Published: August 2021

The present study provides experimental results of the flow pattern and thermal behavior of a none-boiling air-water two-phase flow in a helical tube with a turbulator. In order to evaluate the thermal behavior, a glass tube was put under constant heat flux. The inlet, outlet, and surface temperature of the helical tube were measured to calculate the heat transfer coefficient. The results showed that the addition of the turbulator in the helical tube leads to a rapid conversion from bubble flow to slug flow. Also, the formed bubbles are much smaller and spread radially throughout the pipe. Findings showed that the turbulator significantly improved the heat transfer of the two-phase flow, in which ratios of heat transfer enhancement with and without turbulator is 28% and 19%, respectively. Finally, cost-to-benefit ratio (C.B.R) analysis confirmed that when air-water two-phase flow transits through the helical tube are not affected by the presence or absence of turbulator.
Improvements to torque versus tension relationship considering nut dilation effects
Authors: Fernando Saman , Lee Jessey , Pokharel Tilak , Gad Emad
Published: August 2021

Torque as a tightening method is a simple technique that can be used to tighten a bolt to a given pre-load. Therefore, it is important to theoretically derive an accurate torque vs tension relationship for threaded fasteners as this would enable the industry to achieve a reliable pre-load. Various attempts were made to develop a complete theoretical relationship between torque and tension. Due to the thread angle there exists a nut dilation force causing the nut to expand radially out wards. This effect is more prominent in nuts with smaller height (Style 0 hex nut, refer ISO 4035 1 ). This nut dilation force creates a combined frictional effect with the drive torque thus affecting the torque tension relationship. This paper proposes a novel 3D formulation for torque tension relationship taking into consideration the nut dilation effect. This paper further develops new formulae for tightening and loosening torque, retaining torque, tension vs nut rotational angle relationship as well as formula for nut dilation force for both tightening and loosening.
Increase of energy efficiency ratio of a direct evaporative cooler by dynamic behavior with energy and exergy analysis
Authors: Omidi Kashani Behzad
Published: August 2021

The present research is about increasing the energy efficiency ratio (EER) in current direct evaporative coolers (DEC) in Iran. Increasing the cooling load and reducing the electrical energy consumption simultaneously (increasing the energy efficiency ratio (EER)) in DEC are the main goals of manufacturers and consumers of this device. When the circulation water pump runs continuously (static state), the circulation water rate is about 1.89 to 2.90 times of the amounts recommended in the reasonable standards. In order to adjust the circulation water rate to the recommended amount by standards, the present study has utilized repetitive cyclic scheduling programs to reduce the circulation rate to the optimal amount, (by turning the circulation pump on and off by dynamic pattern operation). In other words, the circulation pump stays on only for a certain period of a working cycle, and then the pump stays off for the rest of it. The cooling load and EER were measured based on ASHRAE 133 (2015). The results indicated that the cooling load in the dynamic state increased by 5.03 and 6.18 percent compared to the static state at low and high fan speeds, respectively. Moreover, in comparison with the static state, the amount of electrical energy consumed (kW-hr) in the dynamic state decreased by 8.8 and 4.2 percent at low and high fan speeds, respectively. Finally, the coefficient of performance (COP or EER) of the DEC in the dynamic state is increased by 15.16 and 10.78 in comparison with the static state at low and high fan speeds, respectively.
Optimal design of helical flute of irregular tooth end milling cutter based on particle swarm optimization algorithm
Authors: Yu Haibin , Zheng Minli , Zhang Wei , Nie Wanying , Bian Tianchen
Published: August 2021

Due to the variable pitch angle and helix angle of the irregular tooth end milling cutter, the mass of the integral end milling cutter is eccentric, and the high stability and precision design of the irregular tooth end milling cutter is still a challenge. Aiming at the influence of dynamic balance of irregular tooth end milling cutter which can not be ignored in high-speed milling, the parameterized design of radial section of irregular tooth end milling cutter was carried out. Based on the space transformation law of the centroid of helical flute, a new method for calculating the centroid coordinate of end milling cutter was put forward, and a general mathematical model of eccentricity of integral end milling cutter was given. It was proved that this model could accurately calculate the centroid position and eccentricity of the end milling cutter. The influence of pitch difference angle and helix difference angle on eccentricity of end milling cutter was studied and analyzed. The particle swarm optimization (PSO) algorithm was creatively applied to optimize the helical flute shape of the end milling cutter, the curvature radius of helical flute curve is optimized, so that the centroid coordinate is infinitely close to the origin of coordinate. The number of iterations was set to 200. In the 32nd iteration, the result approached to infinitesimal, the final function converged, and obtained the groove curvature radius of the milling cuter with the smallest eccentricity. The optimized eccentricity of the end milling cutter is infinitesimal, which can make the vibration damping performance of the end milling cutter be fully developed. On the basis of ensuring the same cutting performance, the cutting tool unbalance was effectively reduced and the dynamic performance of milling cutter was further improved.
Contribution of Lamb wave modes in the formation of higher order modes cluster (HOMC) guided waves
Authors: Abbasi Z , Honarvar F
Published: August 2021

In recent years, Higher Order Modes Cluster (HOMC) guided waves have been considered for ultrasonic testing of plates and pipes. HOMC guided waves consist of higher order Lamb wave modes that travel together as a single nondispersive wave packet. The objective of this paper is to investigate the effect of frequency-thickness value on the contribution of Lamb wave modes in an HOMC guided wave. This is an important issue that has not been thoroughly investigated before. The contribution of each Lamb wave mode in an HOMC guided wave is studied by using a two-dimensional finite element model. The level of contribution of various Lamb wave modes to the wave cluster is verified by using a 2D FFT analysis. The results show that by increasing the frequency-thickness value, the order of contributing modes in the HOMC wave packet increases. The number of modes that comprise a cluster also increases up to a specific frequency-thickness value and then it starts to decrease. Plotting of the cross-sectional displacement patterns along the HOMC guided wave paths confirms the shifting of dominant modes from lower to higher order modes with increase of frequency-thickness value. Experimental measurements conducted on a mild steel plate are used to verify the finite element simulations. The experimental results are found to be in good agreement with simulations and confirm the changes observed in the level of contribution of Lamb wave modes in a wave cluster by changing the frequency-thickness value.
Stability of caisson-type breakwater subjected to strong hydrodynamic impacts using discontinuous deformation analysis method
Authors: Ding Dong , Ouahsine Abdellatif
Published: August 2021

A numerical study using the Discontinuous Deformation Analysis (DDA) method is proposed to analyze the effect of the caisson sliding subjected to a hydrodynamic loading in the stability of the rear side of the caisson-type breakwater. The study takes into account the slope inclination of the breakwater as well as the contact between the armour units constituting the shoreward of the breakwater, where the contact stresses are imposed through a penalty method. A dimensionless displacement parameter, [Formula: see text], is defined to investigate the instability of armor units. The results of the simulation show that the shape of the armour units plays an important role in the stability of the breakwater, where the tetrapods and the acropods give better stability than the cubic shapes, with a clear superiority of the tetrapods. They also show that the reduction in the slope clearly contributes to the stability of caisson up to a slope of 1: 2, but below this ratio of 1: 2 this stability is no longer obvious. Furthermore, a new relation of the displacement of the armour units according to the slope is established.
Epoxy-matrix nanocomposites reinforced by electrospun polymeric nanofibrous layers: PAN, PA-6,6, and hybrid PAN/PA-6,6
Authors: Arpatappeh Farzin Asghari , Gharehaghaji Ali Akbar , Nosraty Hooshang
Published: August 2021

Composite materials with nanofibrous reinforcements are capable of high mechanical performance and enhanced properties despite their low volume fraction of reinforcement. In this study, tensile properties of epoxy-matrix nanocomposites were investigated after reinforcing by hand layup method implementation of randomly oriented electrospun nanofiber layers. The reinforcements were produced from polyacrylonitrile (PAN), Polyamide-6,6 (PA-6,6), and their 50/50 hybrid. The results indicated that PAN enhanced the tensile toughness of the matrix by almost 4 times, increasing both the ductility (an expected 23% due to fiber being more elastic than the matrix) and the ultimate tensile strength (a surprising 35% even though the fibers were less stiff than the matrix). These results indicate significant improvements in the impact properties for advanced applications. The results revealed that PA-6,6 did not show the characteristics of a promising reinforcement whether used solely or added to PAN.
Comparative assessment on weldability of Al 6061 to polycarbonate for dissimilar sheets placement in friction stir lap welding using sensor signals
Authors: Goswami Nisith , Pal Kamal
Published: August 2021

The thermoplastic polymers and precipitation hardened aluminium alloys are highly popular in the aerospace and automobile sectors as a replacement of metallic materials to improve the strength to weight ratio. Thus, the unlike aluminium alloy to polycarbonate assembled structures are often necessary for which mechanical fastening and adhesive bonding are the primary methods for joining as fusion welding processes are inadequate. However, the dissimilar joint efficiency is found to be less. Thus, the ultrasonic and friction welding processes are developed. The friction stir welding is one such advanced material stirring technique without any melting of base materials. The present work addresses metallic aluminium (Al6061) to polycarbonate sheet materials joining using friction stir welding in overlap configuration using tapered H13 tool steel. The thrust force with associated tool stirring torque has been acquired in real time during plunging followed by welding phase. The weld bead profile with respective force-torque signals was analysed for the process monitoring. The tensile test has been carried out on the lap welds. The weld interface of the unlike sheets have also been scrutinised. Initially, the aluminium sheet was partially overlapped on polycarbonate for the parametric study. The highest joint efficiency was found to be 40.2% at 1400 rpm tool rotational speed and 75 mm/min traverse speed due to improper material mixing at the weld interface. Therefore, the feasibility of the process have been tested by placing thermoplastic polycarbonate over aluminium alloy through which the joint efficiency was further improved (48.57%) at comparatively low tool rotational speed (1100 rpm) with lower welding speed (55 mm/min) as the minute metallic particles uniformly mixed with melted and solidified polycarbonate due to more uniform torque in the welding phase. The tool stirring torque and axial thrust was found to be higher in this overlap position.
Fatigue life prediction of pre-corroded AZ31 magnesium alloy based on surface topology
Authors: Shamsarjmand Madjid , Adibnazari Saeed
Published: August 2021

This research explored the corrosion effect of NaCl solution on the surface quality of AZ31 magnesium alloy. Cubic-shaped specimens were immersed in standard 3.5% NaCl solution for 1, 2, 3, and 4 hours. The size of corrosion pits, fatigue crack propagation area, and surface topology were characterized. Fatigue tests were carried out on pre-corroded AZ31 specimens under different stress amplitudes. The correlation between the corrosion time and the virtual crack size was obtained. The virtual crack size is a new parameter that can relate the corrosion to the fatigue life. A new model was proposed to map the surface topology on the virtual crack size of pre-corroded AZ31 magnesium alloy. The fatigue life of 1-4-hour pre-corroded AZ31 specimens could be predicted accurately by this new model. The Levenberg-Marquardt and curve-fitting methods were used to obtain the constant parameters. The relative error between the crack size corresponding to the immersion time and the virtual crack size calculated by the proposed model was less than 1%.
Loss prediction of axial compressors using genetic algorithm–back propagation neural network in throughflow method
Authors: Li Jian , Teng Jinfang , Zhu Mingmin , Qiang Xiaoqing
Published: August 2021

While the consistent advance in computational power has enabled the Computational Fluid Dynamics (CFD) an effective tool for compressor performance characterization, the need for quick performance estimates at initial design phase of compressor still requires the use of low order models. Thus, the throughflow method remains the backbone of compressors design process. The accuracy of the throughflow calculation mainly depends on the adopted empirical correlations. However, the traditional empirical models are just accurate for the conventionally loaded compressor at normal working conditions. In this article, the mechanism of blade profile loss generation and the formation mode of existing empirical correlation are studied, and the reason why the traditional diffusion factor based empirical models are not applicable for modern high-loading compressors or conventional-loading blades at negative incidence is also discussed. Then, the Genetic Algorithm assisted Back Propagation Neural Network (GA-BPNN) is used to train the surrogate model for the design and off-design loss prediction along the blade span of the compressor. Based on the test data of four transonic compressor stages, a database containing 72 sets of blade element geometry and about 1400 sets of blade element performance data is established. Considering the different mechanisms of rotor and stator losses at different working conditions, the entire database and surrogate model are divided into four components according to the rotor and stator at positive incidence and negative incidence. Comparing the prediction results of the surrogate model with the traditional empirical correlations and experimental data, the results show that the GA-BPNN is an alternative solution for developing the empirical model.