Twin-rotor hover performance examination using overlap tests

2017 ◽  
Vol 89 (1) ◽  
pp. 155-163
Author(s):  
Farid Shahmiri
Keyword(s):  
Mathematical Models ◽  
Cross Sections ◽  
Test Model ◽  
Test Plan ◽  
Optimal Test ◽  
Content Type ◽  
Hover Performance ◽  
Power Loading ◽  
Overlap Ratio ◽  
Twin Rotor

Purpose The aim of this paper was to experimentally examine twin-rotor hover performance for different rotor overlap ratios at practical rotor loading. Design/methodology/approach The methodology was formed based on data measurements for a designed twin-rotor test model and development of hover performance mathematical models. Thus, measurements were made using a central composite test plan, and then mathematical models for thrust power required power loading (PL) and figure of merit (FM) as functions of collective pitch tip speed; rotor overlap ratio was obtained. In the present paper, the test model consisted of two three-bladed rotors with a diameter of 220 mm and a blade aspect ratio of 16.05. The blades were of a rectangular planform with NACA 0012 cross sections and had no twist or taper. The model was built such that the rear rotor was fixed on the fuselage, and the front rotor could move longitudinally for tests up to about 40 per cent overlap ratio in hover. Findings The best hover aerodynamic efficiency (maximum PL of 14.6 kg/kW) was achieved for non-overlapped rotors at a low value of disc loading (DL) and also at FM of 0.6 at that DL. This result was in agreement with blade element momentum theory predictions. Practical implications Results for the twin-rotor test model can be generalized for actual tandem helicopters through the Reynolds number transformation technique and also some modifications. Originality/value Design and construction of the twin-rotor test model and experimental measurements of hover performance based on an optimal test plan were performed for the first time.

Optimum time-censored simple ramp-stress accelerated life test sampling plan for the log-logistic distribution

2015 ◽  
Vol 21 (1) ◽  
pp. 112-132 ◽  
Author(s):  
Preeti Wanti Srivastava ◽  
Deepmala Sharma
Keyword(s):  
Sample Size ◽  
Asymptotic Variance ◽  
Sampling Plan ◽  
Accelerated Life Test ◽  
Test Plan ◽  
Life Test ◽  
Life Distribution ◽  
Optimal Test ◽  
Content Type ◽  
Accelerated Life

Purpose – Acceptance sampling plans are designed to decide about acceptance or rejection of a lot of products on the basis of sample drawn from it. Accelerating the life test helps in obtaining information about the lifetimes of high reliability products quickly. The purpose of this paper is to formulate an optimum time censored acceptance sampling plan based on ramp-stress accelerated life test (ALT) for items having log-logistic life distribution. The log-logistic life distribution has been found appropriate for highly reliable components such as power system components and insulating materials. Design/methodology/approach – The inverse power relationship has been used to model stress-life relationship. It is meant for analyzing data for which the accelerated stress is nonthermal in nature, and frequently used as an accelerating stress for products such as capacitors, transformers, and insulators. The method of maximum likelihood is used for estimating design parameters. The optimal test plan is obtained by minimizing variance of test-statistic that decides on acceptability or rejectibility of lot. The optimal test plan finds optimal sample size, stress rates, sample proportion allocated to each stress and lot acceptability constant such that producer’s risk and consumer’s risk is satisfied. Findings – Asymptotic variance plays a pivotal role in determining the sample size required for a sampling plan for deciding the acceptance/rejection of a lot. The sample size is minimized by optimally designing a ramp-stress ALT so that the asymptotic variance is minimized. Originality/value – The model suggested is of use to quality control and reliability engineers dealing with highly reliable items.

Information technology investment and innovation performance: does investment paradox exist?

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Peinan Ji ◽  
Xiangbin Yan ◽  
Yan Shi
Keyword(s):  
Information Technology ◽  
Time Lag ◽  
Innovation Performance ◽  
Test Model ◽  
It Investment ◽  
Firm Innovation ◽  
Data Set ◽  
Content Type ◽  
Lag Effect ◽  
Enterprise Innovation

Purpose The purpose of this study is to deepen the understanding of the effects of information technology (IT) investment on firm innovation performance and examining the investment paradox effect in China. Design/methodology/approach Using a sample of China’ public firms IT investment data between 2010 and 2016, the authors establish a test model of IT investment and innovation performance. Findings The result indicates that IT investment in firms have no effect on innovation performance in the investment period. However, in the full sample and manufacturing sample, the IT investment has a significant positive effect on innovation performance in the post-investment years. In addition, this study finds that large companies and low-age companies may contribute more to innovation when firm investment in IT. Research limitations/implications There are several limitations in this research. First, the authors are failed to obtain a larger sample about the IT investment information data set in China, so this study was compelled to use limited sample data from China, hence, this could lead to errors of too early generalization. Second, the authors use the number of invention patent applications to represent the performance of enterprise innovation, which may not show enterprise innovation effectively. Third, the firms in the sample are all in China Listed Companies, so this may not accurately reflect the entire environment of firm innovation performance, and could possibly. Practical implications The research confirms that there is a paradox and time lag effect in IT investment, which enterprises should pay attention to. Originality/value Existing research confirms that corporate IT investments can bring new products or services. However, the authors still do not know whether IT investment has improved the company’s ability of innovation. This study will fill this gap and the industry effect and time lag effect of the influence of IT investment on innovative performance are also examined.

Printing with mechanically interlocked extrudates using a custom bi-extruder for fused deposition modelling

2018 ◽  
Vol 24 (6) ◽  
pp. 921-934 ◽  
Author(s):  
Mohammad Abu Hasan Khondoker ◽  
Asad Asad ◽  
Dan Sameoto
Keyword(s):  
Cross Sections ◽  
Acrylonitrile Butadiene Styrene ◽  
Easy Access ◽  
Fused Deposition Modelling ◽  
Content Type ◽  
Immiscible Polymers ◽  
Fused Deposition ◽  
Functionally Gradient ◽  
Different Sources ◽  
Butadiene Styrene

Purpose This paper aims to target to print functionally gradient materials (FGM) devices made of immiscible polymers in multi-material fused deposition modelling (FDM) systems. The design is intended to improve adhesion of dissimilar thermoplastics without the need for chemical compatibilization so that filaments from many different sources can be used effectively. Therefore, there is a need to invent an alternative solution for printing multiple immiscible polymers in an FDM system with the desired adhesion. Design/methodology/approach In this study, the authors have developed a bi-extruder for FDM systems which can print two thermoplastics through a single nozzle with a static intermixer to enhance bonding between input materials. The system can also change the composition of extrudates continuously. Findings The uniqueness of this extruder is in its easy access to the internal channel so that a static intermixer can be inserted, enabling deposition of mechanically interlocked extrudates composed of two immiscible polymers. Without this intermixer, the bi-extruder extrudes with simple side-by-side co-extrusion having no mechanical interlocking. The bi-extruder was characterized by printing objects using pairs of materials including polylactic acid, acrylonitrile butadiene styrene and high impact polystyrene. Microscope images of the cross-sections of the extrudates confirm the ability of this bi-extruder to control the composition as desired. It was also found that the mechanically interlocked extrudates composed of two immiscible polymers substantially reduces adhesion failures within and between filaments. Originality/value In this study, the first-ever FDM extruder with a mechanical blending feature next to the nozzle has been designed and used to successfully print FGM objects with improved mechanical properties.

scholarly journals Development of a New Bead Movement-Based Computational Framework Shows that Bacterial Amyloid Curli Reduces Bead Mobility in Biofilms

2020 ◽  
Vol 202 (18) ◽  
Author(s):  
K. Malhotra ◽  
T. Hunter ◽  
B. Henry ◽  
Y. Ishmail ◽  
P. Gaddameedi ◽  
...  
Keyword(s):  
Mathematical Models ◽  
Open Source ◽  
Material Properties ◽  
Laser Scanning ◽  
Cell Movement ◽  
Laser Scanning Confocal Microscopy ◽  
Critical Parameters ◽  
Gastrointestinal Microbiota ◽  
Content Type ◽  
Scanning Confocal Microscopy

ABSTRACT Biofilms exist in complex environments, including the intestinal tract, as a part of the gastrointestinal microbiota. The interaction of planktonic bacteria with biofilms can be influenced by material properties of the biofilm. During previous confocal studies, we observed that amyloid curli-containing Salmonella enterica serotype Typhimurium and Escherichia coli biofilms appeared rigid. In these studies, Enterococcus faecalis, which lacks curli-like protein, showed more fluid movement. To better characterize the material properties of the biofilms, a four-dimensional (4D) model was designed to track the movement of 1-μm glyoxylate beads in 10- to 20-μm-thick biofilms over approximately 20 min using laser-scanning confocal microscopy. Software was developed to analyze the bead trajectories, the amount of time they could be followed (trajectory life span), the velocity of movement, the surface area covered (bounding boxes), and cellular density around each bead. Bead movement was found to be predominantly Brownian motion. Curli-containing biofilms had very little bead movement throughout the low- and high-density regions of the biofilm compared to E. faecalis and isogenic curli mutants. Curli-containing biofilms tended to have more stable bead interactions (longer trajectory life spans) than biofilms lacking curli. In biofilms lacking curli, neither the velocity of bead movement nor the bounding box volume was strictly dependent on cell density, suggesting that other material properties of the biofilms were influencing the movement of the beads and flexibility of the material. Taken together, these studies present a 4D method to analyze bead movement over time in a 3D biofilm and suggest curli confers rigidity to the extracellular matrix of biofilms. IMPORTANCE Mathematical models are necessary to understand how the material composition of biofilms can influence their physical properties. Here, we developed a 4D computational toolchain for the analysis of bead trajectories, which laid the groundwork for establishing critical parameters for mathematical models of particle movement in biofilms. Using this open-source trajectory analyzer, we determined that the presence of bacterial amyloid curli changes the material properties of a biofilm, making the biofilm matrix rigid. This software is a powerful tool to analyze treatment- and environment-induced changes in biofilm structure and cell movement in biofilms. The open-source analyzer is fully adaptable and extendable in a modular fashion using VRL-Studio to further enhance and extend its functions.

Evaluation of some mathematical models of solar radiation received by a ground collector

2016 ◽  
Vol 13 (4) ◽  
pp. 376-380 ◽  
Author(s):  
Abdelouahab Zaatri ◽  
Norelhouda Azzizi
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Mathematical Models ◽  
Design Methodology ◽  
Energy Systems ◽  
Ground Level ◽  
Content Type ◽  
Design And Optimization ◽  
Best Fit ◽  
Complex Influence

Purpose Using modeling approaches, this paper aims to propose different mathematical models for estimating the different components of the solar radiation as well as the received solar energy by a collector. Design/methodology/approach In this article, the authors consider three mathematical models to estimate the solar radiation captured at ground level by a solar collector. These models are Capderou model, Liu & Jordan model and R.sun model. In the context of the design of experiments, we performed measurements of solar radiation received by a collector using a pyranometer. The obtained measurements were compared with the three mathematical models. Findings The comparison enabled the subsequent evaluation to determine the most appropriate model that best fit for our region. As a result, the Capderou model reveals to be the most suitable for our region. Originality/value Estimation of solar radiation at ground level (received by a collector) is of paramount importance for the design and optimization of solar energy systems. Nevertheless, many factors influence the amount of energy received by a collector situated at a ground, such as the longitude of the location, latitude, altitude, tilt collector orientation, temperature and humidity of the environment, wind speed, etc. Because of the complex influence of these parameters, the received solar radiation by the collector is a dynamical and a random process.

Farmland transfer and agricultural economic growth nexus in China: agricultural TFP intermediary effect perspective

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yuan-pei Kuang ◽  
Jia-li Yang ◽  
Meseret-Chanie Abate
Keyword(s):  
Economic Growth ◽  
Agricultural Economic ◽  
Test Model ◽  
Promoting Effect ◽  
Content Type ◽  
Effect Model ◽  
Intermediary Role ◽  
Multidimensional Effects ◽  
The Impact

PurposeThe multidimensional effects of farmland transfer in China have been profoundly unstudied. The purpose of this paper is to provide insights on the effects of the intermediary role of agricultural total factor productivity (TFP) of farmland transfer on agricultural economic growth in China.Design/methodology/approachBased on the agricultural data of 30 provinces in China over the period 2005–2018, this paper uses the intermediary effect model to test the relationship between farmland transfer, agricultural TFP and agricultural economic growth. This paper employed an intermediary effect test model to investigate the intermediary role of agricultural TFP in the influence of farmland transfer on agricultural economic growth.FindingsThe findings indicated that farmland transfer has a significant effect on promoting agricultural economic growth. There is a significant “inverted U-shaped” relationship between farmland transfer and agricultural TFP. The sample value of 84.3% of farmland transfers in China is still within the TFP promoting effect range. In addition, farmland transfer has an indirect impact on agricultural economic growth through the channel of agricultural TFP. Agricultural TFP plays a significant intermediary role, but the effect is relatively lowOriginality/valueThis paper is the first to provide fundamental evidence on the impact of farmland transfers on agricultural economic growth in China, driven by agricultural TFP as an intermediary factor. Agricultural TFP can reduce the involution effect of farmland transfer and promote an indirect effect on agricultural economic growth.

Contractional salt tectonics and role of pre-existing diapiric structures in the Southern Pyrenean foreland fold–thrust belt (Montsec and Serres Marginals)

2021 ◽  
pp. jgs2020-085 ◽  
Author(s):  
Laura Burrel ◽  
Antonio Teixell
Keyword(s):  
Cross Sections ◽  
Foreland Basin ◽  
Salt Tectonics ◽  
Structural Development ◽  
Field Observations ◽  
Content Type ◽  
Growth Strata ◽  
Structural Style ◽  
Supplementary Material

Triassic Keuper evaporites have long been recognized as the main detachment level for thrusting in the Pyrenean fold–thrust belts. The deformed Late Cretaceous–Eocene foreland basin of the Southern Pyrenees has structures and stratal geometries that can be interpreted as related to salt tectonics (e.g. unconformities, rapid thickness variations, long-lived growth fans and overturned flaps), although they have been overprinted by shortening and thrusting. Based on field observations and published maps, we build new structural cross-sections reinterpreting two classic transects of the Southern Pyrenees (Noguera Ribagorçana and Noguera Pallaresa river transects). The sequential restoration of the sections explores the variations in structural style, addressing the role of halokinesis in the tectonic and sedimentary development. In the Serres Marginals area, we propose that salt pillows and diapirs started developing locally during the Mesozoic pre-orogenic episode, evolving into a system of salt ridges and intervening synclines filled with early synorogenic sediments. Rapid amplification of folds recorded by widespread latest Cretaceous–Paleocene growth strata is taken as marking the onset of contractional folding in the area. During Pyrenean compression, folding mechanisms transitioned from dominantly halokinetic to a combination of buckling and differential sedimentary loading. Squeezing of salt diapirs and thrust welding occurred as salt ridges were unroofed. We provide new field observations that lead to a reinterpretation of the regional structural development and contribute to the debate about the role of salt tectonics in the Pyrenees.Supplementary material: Table S1, giving the thickness of the main stratigraphic units, is available at https://doi.org/10.6084/m9.figshare.c.5287737

DRG-based payment system and management accounting changes in an Indonesian public hospital: exploring potential roles of big data analytics

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Heru Fahlevi ◽  
Irsyadillah Irsyadillah ◽  
Mirna Indriani ◽  
Rina Suryani Oktari
Keyword(s):  
Big Data ◽  
Mathematical Models ◽  
Data Analytics ◽  
Public Hospital ◽  
Cost Control ◽  
Management Accounting ◽  
Big Data Analytics ◽  
Content Type ◽  
Patient Costs ◽  
Accounting Changes

Purpose This study aims to provide insights into management accounting changes (MACs) and potential roles of big data analytics (BDA) in accelerating the MACs in an Indonesian public hospital as a response towards the adoption of the diagnosis-related groups (DRG)-based payment system. Design/methodology/approach A mixed-method approach was used to collect and analyse data from a referral public hospital in Indonesia. First, a BDA simulation was carried out to reveal its usefulness in predicting and evaluating patient costs, and finally improving the cost recovery rate (CRR) of each DRG case. This part formulated and tested the mathematical models that predict patient cost, the CRR and determinants (length of stay/LOS, severity/SEV, patient age/AGE and gender/SEX). For this purpose, data of the top ten inpatient cases of 2018 were collected and analysed. Second, semi-structured interviews with senior staff and doctors were carried out to understand cost control strategies implemented in the hospital and the management and doctors’ perceptions regarding the application of tested mathematical models for cost control. Old institutional economics and new institutional sociology were used to gain insight about how and why management accounting practices changed in the hospital. Findings The findings show that the absence of detailed per-case/patient cost information has not only hindered further evolvement of MACs but also stimulate tensions between managerial and medical worlds in the studied Indonesian public hospital. The simulation of BDA in this study was not only discovering the determinants of case cost recovery but also enabling the prediction of CRR of patients immediately after admission. The application of BDA and casemix accounting in the hospital will potentially become catalysts of discussion and mutual learning between managerial and medical staff in controlling patient costs. Originality/value This paper provides a more comprehensive picture of the potential roles of BDA in cost control practices. The study assesses the feasibility of BDA application in the hospital and evaluates the potential roles and acceptance of BDA application by both management and doctors.

Design variation of thin-walled composite beam cross-section properties

2016 ◽  
Vol 12 (3) ◽  
pp. 558-576 ◽  
Author(s):  
Aníbal J.J. Valido ◽  
João Barradas Cardoso
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Laminated Composite ◽  
Adjoint System ◽  
Design Sensitivity ◽  
Content Type ◽  
Design Elements ◽  
Thin Walled ◽  
The Cross ◽  
Cross Section Geometry

Purpose The purpose of this paper is to present a design sensitivity analysis continuum formulation for the cross-section properties of thin-walled laminated composite beams. These properties are expressed as integrals based on the cross-section geometry, on the warping functions for torsion, on shear bending and shear warping, and on the individual stiffness of the laminates constituting the cross-section. Design/methodology/approach In order to determine its properties, the cross-section geometry is modeled by quadratic isoparametric finite elements. For design sensitivity calculations, the cross-section is modeled throughout design elements to which the element sensitivity equations correspond. Geometrically, the design elements may coincide with the laminates that constitute the cross-section. Findings The developed formulation is based on the concept of adjoint system, which suffers a specific adjoint warping for each of the properties depending on warping. The lamina orientation and the laminate thickness are selected as design variables. Originality/value The developed formulation can be applied in a unified way to open, closed or hybrid cross-sections.

Optimal feedback control of twin rotor MIMO system with a prescribed degree of stability

2016 ◽  
Vol 4 (4) ◽  
pp. 226-238 ◽  
Author(s):  
Santosh Kumar Choudhary
Keyword(s):  
Optimal Control ◽  
Tracking Control ◽  
Mimo System ◽  
Control Solution ◽  
Content Type ◽  
Degree Of Stability ◽  
Twin Rotor Mimo System ◽  
Posture Stabilization ◽  
Twin Rotor ◽  
Stability Concept

Purpose The purpose of this paper is to investigate an optimal control solution with prescribed degree of stability for the position and tracking control problem of the twin rotor multiple input-multiple output (MIMO) system (TRMS). The twin rotor MIMO system is a benchmark aerodynamical laboratory model having strongly non-linear characteristics and unstable coupling dynamics which make the control of such system for either posture stabilization or trajectory tracking a challenging task. Design/methodology/approach This paper first describes the dynamical model of twin rotor MIMO system (TRMS) and then it adopts linear-quadratic regulator (LQR)-based optimal control technique with prescribed degree of stability to achieve the desired trajectory or posture stabilization of TRMS. Findings The simulation results show that the investigated controller has both static and dynamic performance; therefore, the stability and the quick control effect can be obtained simultaneously for the twin rotor MIMO system. Originality/value The articles on LQR optimal controllers for TRMS can also be found in many literatures, but the prescribed degree of stability concept was not discussed in any of the paper. In this work, new LQR with the prescribed degree of stability concept is applied to provide an optimal control solution for the position and tracking control problem of TRMS.

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