bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffraction Control Methods of Extended Products’ Diameter
Authors: Fedorov Evgeny , Chicherina Nataliya , Tlusty Josef , Tuzikova Valeriya
Published: January 2019

In this paper the measurement methods for extended objects’ geometry on the basis of effect of light diffraction which can be applied to technological control of products with wide range of diameters from the smallest to the largest are described. During measurement the method that allows to minimize the influence of disturbing factors on the results of measurements of diameter of thin fibers of small diameters of micron is described. Disturbing factors include excessive flare of area of the central maximum range. The diffraction method is considered that allows to increase to units of micrometers the resolution of the optical measuring converters used in devices to perform technological control of cylindrical extended products of a large diameter such as: cables, wires, cords, etc. The transformation function allowing to calculate diameter of cylindrical products irrespective of their location in a control zone on the basis of the diffraction method of delimitation of the product shadow in optical two-coordinate converters with the dispersing laser bunch is offered and experimentally confirmed. The achieved results can be used for development of high-precision optical devices of technological control of outer diameter and eccentricity of products for cable, pipe and other products in different industry fields.
Correlation between Microstructure and Properties of Semi-Solid Products
Authors: Pola Annalisa
Published: January 2019

Since the very first production trials, it was evident that semi-solid components exhibit excellent mechanical properties, comparable to those of forged material and, in any case, better than permanent mold castings. Over the years, these findings have been confirmed by many authors. Most of the papers available in scientific literature deals with the demonstration of this improvement, especially in order to show the reliability of new and alternative production routes. On the contrary, only some studies focus their attention on the relationship between enhanced mechanical properties and the microstructure. However, it is demonstrated that the increased performance of semi-solid components is not only due to the absence of porosity, but there is a clear relationship between microstructure and properties. This paper reports about the state of knowledge in this subject, in particular for what concerns tensile, fatigue, wear and corrosion resistance.
Mechanical Properties of CNTS-Grafted Carbon Fiber/Magnesium Composites Prepared by Liquid-Solid Infiltration Extrusion
Authors: Zhou Ji Ming , Meng Hai Ming , Han Li Jun , Qi Le Hua
Published: January 2019

CNTs-grafted carbon fiber reinforced magnesium composites (CNTs-Cf/Mg) were successfully prepared by liquid-solid infiltration extrusion process, in which the carbon fiber cross-ply preform were grafted with carbon nanotubes (CNTs) by using the injection chemical vapor deposition (ICVD) technique. The mechanical properties of AZ91D matrix alloy and magnesium matrix composite at different states were tested and compared. The results show that the dendrites of the as-cast AZ91D alloy are transformed into granular grains after liquid-solid forming. The composite reinforced by carbon fiber with grafting nanotubes is beneficial to the one reinforced with carbon fiber but without grated CNTs. The nanotubes grafted on carbon fiber improve the bonding property of the fiber-matrix interface and protect the carbon fiber from degradation more effectively. The tensile strength of the CNTS-Cf/Mg composites is 28.3% higher than the Cf/Mg composites.
Influence of Pouring Temperature and Alloy Additions on the Quality of a Semisolid Material Dragged during the Continuous-Casting Strip Processing of Al–Si A413
Authors: de Pádua Lima Filho Antonio , Ferreira Lucas Veronez Goulart , de Oliveira Neto Pedro Barbosa , de Oliveira Cássio Basile , de Oliveira Arantes Carlos Henrique , de Castro Tales Paschoalino , Borodiak Miguel , Quadro Alexandre Leão
Published: January 2019

Al–Si A413 treated and untreated alloys were cast and poured at approximately 720 oC, 700 oC, and 680 oC in a cooling slope to obtain the semisolid material feeding the ceramic nozzle (150 cm3) at the lower roll (single-roll melt-dragged processing)—this drags the metallic slurry via the chill/columnar layers at a rate of 0.2 m/s, forming a molten-metal strip with a thickness of 2 mm and width 45 mm, approximately. The untreated alloy poured at 720 oC formed coarse structures of α-Al dendrites, as well as a coarse eutectic of Al–Si and microshrinking on the surface of the casting strip facing the atmosphere. The Al–Si 413 alloy poured at 680 oC and treated with Al5Ti1B (0.1%) led to microstructural refinement, resulting in α-Al globular structures, the absence of microporosities on the surface facing the atmosphere, and a finer and more homogeneous distribution of the eutectic grains with smaller Si particles. The AlTiB master alloys are not used as a grain refiner in Al–Si alloys because of Si poisoning. This subject is discussed in this paper. The addition of the inoculant and 0.2% of the Al–Si eutectic morphology modifying agent (Al–10%Sr) refined both the α-Al and eutectic phases more efficiently in the cast strip poured at 700 oC and 680 oC. This suggests that the inoculant did not interfere with the action of the modifying agent. As a result, molten metal strips of higher mechanical strengths and ductilities were obtained.
Semisolid Casting of Short Freezing Range Alloys
Authors: Marani Farshid , NIROUMAND BEHZAD
Published: January 2019

Semisolid casting and non-dendritic solidification of commercially pure tin (about 1 °C freezing range) and Zamak 3 alloy (about 10 °C freezing range) by a modified serpentine channel method were studied. It was shown that semisolid casting of very small freezing range metals with a non-dendritic structure was possible using this method. The results showed that the wall of the copper serpentine channel mold acted as a substrate for heterogeneous copious nucleation of primary solid particles and the channel provided sufficient self-steering action to disperse the nuclei in the melt. The average diameter and shape factor of the primary particles in the semisolid cast CP-Sn sample was measured to be about 107 μm and 0.75, respectively. The average diameter and shape factor of the primary particles in the semisolid cast Zamak 3 alloy was measured to be about 16 μm and 0.8, respectively. Hardness of semisolid samples was slightly higher than those of conventional gravity cast samples.
Addition of Swarf to Produce a Semi-Solid Slurry during High Pressure Die-Casting of AS9U3 Aluminum Alloy
Authors: Hadian Hooman , Haddad-Sabzevar M. , Mazinani Mohammad
Published: January 2019

An internal cooling agent is used in rapid slurry forming (RSF) process to produce a high solid fraction slurry for a short period of time. In the process used in this research, the swarf which is known to be a low enthalpy material was added to the melt as the internal cooling agent. During the process, the swarf started to melt and a semi-solid slurry with a relatively high solid fraction was formed. This slurry was formed by exchanging the enthalpies between the low and high enthalpy materials. A commercial Al-Si-Cu alloy, i.e. AS9U3 Aluminum alloy, was used in this investigation. The microscopic examination showed that the Al-Si eutectic colonies start to melt during the melting process of swarf material resulting in the formation of globular Alpha-Al grains due to the multiplication of secondary dendrites arms. The fracture of dendrites arms and the subsequent spheroidization were suggested to be the origin of non-dendritic globular grains in the final microstructure. The amount of primary globular Alpha-phase was measured by the image analysis software. The results showed that during high pressure die-casting of AS9U3 Aluminum alloy using 4 mm thick samples, around 35 percent solid has been formed at the temperature of 580 oC.
Dendrite Fragmentation in Semisolid Casting: Could we Do this Better?
Authors: Flemings Merton C.
Published: January 2019

A summary is given of the history of our understanding of dendrite coarsening, including particularly fragmentation. Much is now understood about this process as it takes place in directional solidification of a quiescent melt. Much less is understood about it in the rapidly cooled, turbulent environment of semi-solid casting. The importance of dendrite fragmentation in semi-solid processing is that it is key to obtaining fine final grain size, grain spheroidicity and rapid production rate. I have chosen in this keynote paper to talk about the fundamentals of an important part of the semisolid casting process ... that of “dendrite fragmentation.” The paper is written with an eye to its possible practical usefulness to researchers in process innovation. If we understood the dendrite fragmentation mechanism better, could we achieve finer, more numerous, grains than we do now Could fully non dendritic structures be obtained industrially in short processing times
Evaluation of Al-5wt%Si-5wt%Zn as Raw Material for Semisolid Forming
Authors: Proni Cecilia Tereza Weishaupt , de Paula Leandro Cássio , Torres Luis , Zoqui Eugênio José
Published: January 2019

Designing new alloys for semisolid processing is key to the success of semisolid materials technology. While aluminium-silicon and aluminium-zinc alloys have been tested as potential raw materials, ternary aluminium alloys containing silicon and zinc have yet to be tested. As such alloys may exhibit the rheological behaviour required for semisolid forming and the excellent final mechanical properties of Al-Zn alloys, we investigated the thermodynamic aspects of the solid-liquid transition of Al-5.5wt%Si-5wt%Zn alloy, the morphological stability of this alloy in the semisolid temperature range and the corresponding rheological behaviour. Thermo-Calc® simulation software was used to evaluate the solid-to-liquid transition and identify the semisolid temperature range within which the liquid-fraction sensitivity is low and the process is therefore controllable. Based on the results of the simulation, a target temperature of 588 °C was chosen. This is sufficient to produce a liquid fraction of 55 % and a corresponding liquid-fraction sensitivity (dfl/dT) of 0.009 C-1. The Al-5wt%Si-5wt%Zn alloy was prepared by conventional casting in a refrigerated copper mould without grain refining, and the alloy was characterized to determine the stability of the microstructure after heating to 588 °C and holding at this temperature for holding times of 0, 30, 60, 90 and 120 s. The same temperature and holding times were used to evaluate the rheological behaviour in hot compression tests. A grain size of 170 μm, globule size of 100 μm and circularity of 0.6 were achieved, leading to a maximum apparent viscosity of 2 x 105 Pa.s, which rapidly decreased to 3 x 104 Pa.s after a shear rate of 9 s-1 was reached.
Modelling and Experimental Investgations of Tooling Issues for Thixoforming of Steel
Authors: Rassili Ahmed
Published: January 2019

Since the early 90’s, and from the very early investigations of steel thixoforming, tool materials as well as different kinds of coatings, including different tool steels and fully ceramic systems have been evaluated. The failure mechanisms have been carefully investigated by experiments and simulations and are nearly fully understood. Analysis of the reported literature on this topic shows that there is still a lot to do in this field and no excellent solution exists now a days for steel thixoforming. The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during steel thixoforming process in order to determine appropriate tool materials and solutions. This evaluation was realized thanks to experimental trials and to the finite elements simulations. The effect of these loadings on the tool’s failure modes are highlighted and compared to the ones observed in classical forming processes. Beyond this, the failure modes of different tool materials and solutions are presented. The tested materials are hot-working tool steels. Other possibilities and tool coating or surface treatments are discussed as well.
Study on Thixoforming Process of 15%SiCp/2A14 Composite for Production of Track Shoe
Authors: Zheng Han Sen , Bai Yue Long , Guan Tian Yang , Zhang Zhi Feng , Xu Jun
Published: January 2019

Semi-solid thixoforming process was applied to produce track shoe of 15%SiCp/2A14 composites. The thixoforming process optimization was simulated by using Deform 3D software. The effects of forging pressure, slug size and reheating temperature on formability of track shoe were investigated. The results showed that a track shoe with better integrity was prepared by optimizing the process, and its microstructure and mechanical properties could meet requirements.
A Study of Anodising Behaviour of Al-Si Components Produced by Rheocasting
Authors: Zhu Bai Wei , Seifeddine Salem , Jarfors Anders E.W. , Leisner Peter , Zanella Caterina
Published: January 2019

This paper aims to investigate the anodising behaviour of Al-Si components produced by rheocasting, to understand the effect of the surface liquid segregation (SLS) on the anodising response. The material investigated was EN AC 42000 Al-alloy with an addition of 150 ppm Sr. The component was rheocast and conventionally liquid cast for benchmarking. The RheoMetalTM process was used to prepare slurry and subsequently cast using a vertical pressure die casting machine. Prior to anodising, mechanical grinding was used as pre-treatment method for selected samples as comparison with components in the as-cast state. Anodising was performed on the components using a constant controlled voltage at 25 V, in 1 M H2SO4, at room temperature. The duration of anodising was varied from 30 mins to 120 mins to examine the relationship between oxide layer thickness and the anodising time. The oxide layer was investigated and characterised. The results demonstrated that the presence of the SLS layer, which was enriched with alloying elements, had a significant influence on the anodising behaviour of the cast component. The oxide layer thickness of the components produced by rheocasting and fully liquid casting was measured and compared. The relations between the oxide layer thickness and anodising time, as well as the casting methods are presented and discussed in this paper.
Recent Advances in Commercial Application of the Rheometal Process in China and Europe
Authors: Jarfors Anders E.W. , Zheng Jin Chuan , Chen Liang , Yang Jie
Published: January 2019

Recent advances in rheocasting have resulted in significant expansion in the types of products currently in full commercial production. The current paper gives an overview of components in production in Europe and in China produced using the RheoMetalTM process, that has taken the lead in a strong drive towards new heavy-duty applications made from aluminium alloys. In China, the dominating applications are found in the telecom industry. The trend in Europe is more towards marine and automotive applications commonly in fatigue loaded applications. The reason for the choice of rheocasting for complicated shape thin-walled electronics components with requirements is dominated by process yield and by the ability to improve thermal conductivity. The heavy-duty truck chassis thick walled components target weight reduction through design and to sustain fatigue load normally requiring forged components. Common in all applications are seen in production yield, reduced tool wear and reduction of die soldering.
Recent Developments of Rheo-Diecast Components for Transportation Markets
Authors: Li Da Quan , Zhang Fan , Midson Stephen P. , Liang Xiao Kang , Yao Hui
Published: January 2019

Recent developments and applications of rheo-diecast components for transportation markets are described. The components have been produced using the SEED (Swirled Enthalpy Equilibrium Device) semi-solid process. The development process typically involves several steps, including (1) an evaluation (and modification) of the component design to ensure it is suitable for semi-solid die casting, (2) the use of flow and solidification simulation to optimize the layout of the gating system, and to ensure that the modified component design can be produced without filling turbulence and shrinkage porosity, (3) stress modeling to ensure that the redesigned component will meet performance targets, and (4) in-plant development of the optimum process parameters. This development process will be described in detail for several commercial components, including two brackets for trucking applications, and connectors used in the frame of an electric bus.
Die Design for Main Bearing Cap of Engine Block Based Semi-Solid Die Casting Process and the Comparison Analysis with Squeeze Casting Process
Authors: Chen Song , Li Da Quan , Zhang Fan , Luo Min , Liang Xiao Kang , Zhu Qiang
Published: January 2019

There are two new processes to development automobile structural components which have certain thickness. In the present paper, taking a main bearing cap product as an example, analyses die design by comparing the experimental and computational numerical simulation results. For the main bearing cap, product structure and mold design were designed to be suitable for characters of SSM die casting and squeeze process. Semi-solid slurry has significantly higher viscosity than liquid metal. This character of fluidity and solid fraction phase make the flow condition more laminar than liquid squeeze casting with the partial fill experiment. And compared with squeeze casting process, the globular shape grain size is smaller than dendritic structure. And mechanical property result shows that the elongation of SSM die casting can achieve more than twice than squeeze casting.
Microstructure and Mechanical Properties of AZ91D Alloy by Three Types of Forging Process
Authors: Tian Wen Tong , Yang Hui
Published: January 2019

Forging processes, such as liquid forging, rheoforging and thixoforging process, were used in this study as an effective method for manufacturing high-strength, finely-dispersed and highly-uniform AZ91D alloy parts. It has been found that although the microstructures of the three forging parts are all composed of α-Mg and β-Mg17Al12 phases, their shapes, sizes, numbers and distributions are all different, which also influences their mechanical properties. The tensile fracture morphologies were observed and their energy spectrums were analyzed by scanning electron microscopy. The results show that the cracks are mainly originated from the brittle fracture of the β-Mg17Al12 eutectic phases, whereas their fracture morphologies are greatly different, which indicate the direction for providing a reasonable forging process.
Les toxines des staphylocoques d’origine animale. Préparation et titrage de la toxine β
Authors: Pillet J. , Orta B. , Isbir S. , Mercier P.
Published: January 2019

La toxine staphylococcique β, caractéristique des souches d’origine animale, peut être obtenue en quantité importante en milieu liquide, mais est très généralement associée à des quantités variables de toxine u, ce qui entraîne des difficultés considérables dans les titrages.

Parmi les méthodes permettant d’obtenir la toxine α isolée, la floculation spécifique de la toxine a effectuée sur une toxine mixte α β est la meilleure, le chauffage ou l'action du formol entraînant une perte importante en toxine β.

Nous remercions bien sincèrement les Professeurs Guilhon et Goret, M. Zottner, directeur des Laboratoires des services de l’élevage du Maroc, le vétérinaire commandant Pigoury, M. Dutheil, de Roquefort, ainsi que nos collègues Staub, Chevé et Jacotot, d’avoir bien voulu nous adresser ces souches.
High Power Density, 48V Electrified Drivetrain Technology for Future Hybrid and Electric Vehicles
Authors: Drury William , Patel Chintanbhai , Atkins Andrew , Wearing Anthony
Published: January 2019

A duplex 3-phase (6-phase with 2 star-points) eMachine and associated inverter, including the development of the control algorithm, for a P2 hybrid vehicle was developed. The requirements, relating to power and duty cycle, flow down from the vehicle to the eMachine: these are shown and design issues relating to the use of a 48V system presented. The focus on low cost, compact solutions runs through the work. The inverter is rated at 25 kW to drive an interior permanent magnet eMachine, supplied by a 48V dc-link. The focus of the work presented in this paper is the inverter controller development and powertrain sizing. The test results of the eMachine with the inverter are presented to show the drive system operating the 6-phase current controller and inverter.
Model Guided Application for Investigating Particle Number (PN) Emissions in GDI Spark Ignition Engines
Authors: Lee Kok Foong , Eaves Nick , Mosbach Sebastian , Ooi David , Lai Jiawei , Bhave Amit , Manz Andreas , Geiler Jan Niklas , Noble Jennifer Anna , Duca Dumitru , Focsa Cristian
Published: January 2019

Model guided application (MGA) combining physico-chemical internal combustion engine simulation with advanced analytics offers a robust framework to develop and test particle number (PN) emissions reduction strategies. The digital engineering workflow presented in this paper integrates the kinetics & SRM Engine Suite with parameter estimation techniques applicable to the simulation of particle formation and dynamics in gasoline direct injection (GDI) spark ignition (SI) engines. The evolution of the particle population characteristics at engine-out and through the sampling system is investigated. The particle population balance model is extended beyond soot to include sulphates and soluble organic fractions (SOF). This particle model is coupled with the gas phase chemistry precursors and is solved using a sectional method. The combustion chamber is divided into a wall zone and a bulk zone and the fuel impingement on the cylinder wall is simulated. The wall zone is responsible for resolving the distribution of equivalence ratios near the wall, a factor that is essential to account for the formation of soot in GDI SI engines. In this work, a stochastic reactor model (SRM) is calibrated to a single-cylinder test engine operated at 12 steady state load-speed operating points. First, the flame propagation model is calibrated using the experimental in-cylinder pressure profiles. Then, the population balance model parameters are calibrated based on the experimental data for particle size distributions from the same operating conditions. Good agreement was obtained for the in-cylinder pressure profiles and gas phase emissions such as NOx. The MGA also employs a reactor network approach to align with the particle sampling measurements procedure, and the influence of dilution ratios and temperature on the PN measurement is investigated. Lastly, the MGA and the measurements procedure are applied to size-resolved chemical characterisation of the emitted particles.
Cylinder Head Gasket Fretting Simulation for High Horse Power Engine
Authors: Sangle Dnyaneshwar R. , Ozarde Amit , McNay Gene
Published: January 2019

The head gasket of an internal combustion engine acts as a critical seal between its cylinder block and heads. Typically, and ideally, a high horse power engine head gasket will be composed of elastomer fluid sealing elements in a carrier and combustion seal body composed of aluminum, brass, carbon steel, copper, nickel, and/or stainless steel etc. The head gaskets purpose is to seal high pressure combustion gases, coolant, and oil and to ensure no leakage of gases or fluids out of the block to head joint.

Three major failure modes [1] for cylinder head gasket joint are; 1. Fluid or gas leakage due to low sealing pressure. 2. Head gasket (bead) cracking due to high gap alternation and 3. Gasket scrubbing/fretting due to pressure and temperature fluctuations causing relative movement in the joint. During engine operation, the head gasket design should be robust enough to prevent all failure modes and provide acceptable performance. Sealing analysis method to address low sealing pressure failure mode is well developed and common within the industry. This paper is focused on the development and utilization of an analytical method for the 3rd failure mode mentioned above i.e., scrubbing/fretting. Single layer metal gasket is considered during the scope of mentioned method. Single layer metal gasket gets locally yielded due to the design feature provided on the cylinder liner, called as bite ring.

During the scope of work, head gasket fretting mechanism is investigated. Based on the understanding of the fundamental fretting mechanism, considering Ruiz model [2], an analysis procedure is developed and finite element analysis results are correlated with actual failures and measured data. Finite element analysis results shows very good correlation in terms of relative sliding magnitude and failure location prediction. Commercial software ANSYS is used here. Actual gasket crushing is simulated by using 3D solid elements with non-linear material and geometric non linearity captured.
Solutions for Emission Robustness of BS VI Phase II Respecting the Market Specific Requirements
Authors: Raser Bernhard , Daum Steffen , Hadl Klaus , Hasenbichler Gernot , Wabnig Armin
Published: January 2019

Most stringent emission legislations have been implemented in all major markets to improve air quality across the past years. This effects the product cost of the vehicles which is considered being critical and needs to be minimized. India suffers from bad air quality and countermeasures have been defined. One being the implementation of similar emission standards than EU VI. By doing so, India takes a large step going from the currently effective BS IV directly to BS VI. Emission reduction is currently mainly handled by the usage of EGR, thus no engine aftertreatment system has been applied. BS VI will require an aftertreatment (EAS) concept with several catalysts and corresponding control system.

India is a very cost sensitive market and a carry over of solutions from the EU needs to be evaluated carefully and new approaches need to be found.

While the enforcement of BS VI Phase I does not dictate any in-service conformity factors yet, phase II (planned implementation 2023) possibly enforces a conformity factor of 1,5 for pollutants as well as more stringent OBD requirements.

In this paper different engine + EAS concepts will be presented and evaluated in terms of emission compliance and product cost. One interesting technology route for N3 applications could be a non EGR approach. In order to master the challenges for that approach AVL´s unique controls and diagnosis concept with focus on emission robustness will be presented and explained.
Numerical Investigation of Pressure Drop for Various Models of Catalytic Converter to Capture CO2 Emission using Activated Carbon
Authors: Mohan kumar S. , Satish S.
Published: January 2019

Internal combustion engines are found to be extensively used in both mobile and stationary applications. The major drawbacks in diesel engines are the release of harmful gases like HC, CO, NOx and PM into atmosphere. There is several pre combustion and post combustion techniques are available to control these emissions effectively. Although CO2 emissions from I.C engines considered as a regulated emission but it is a leading contributor towards Greenhouse gases. In this work a numerical investigation on backpressure was carried out by varying porosity factor of activated carbon. Activated Carbon seems to be viable substance to capture CO2 emission from diesel exhaust. To evaluate the backpressure an analysis was carried out using CFD ANSYS fluent software. In the present investigation an analysis is carried out by placing activated carbon at three different variations. Then the analysis are done by varying three different porosity percentages 30,35 and 45 by placing activated carbon at three different locations. Final study reveals that activated carbon placed at PC35-3 layout shows optimum backpressure and high filtration efficiency while compared with other two layouts.
Performance and Emission Characteristics of a CI Engine Fuelled with Palm and Sesame Oil Blended Diesel
Authors: Tejesh Pala , Kotebavi Vinod , Shyam Pamarthi , Siva Durga Prasad P.
Published: January 2019

Biodiesel can be considered as a clean, renewable and domestically produced diesel fuel. At present, a lot of research is being carried out to make biodiesel more efficient so that it can be substituted for conventional diesel. In the present investigation, biodiesel is extracted from palm and sesame oil by transesterification method. The different properties of biodiesel like flash point, fire point, density, viscosity, pour point, cloud point and calorific value are measured. The obtained values are meeting the standards of biodiesel. This dual biodiesel was blended (0-40%) with diesel and was tested in a 4 stroke single cylinder diesel engine at different loads. The performance characteristics like thermal efficiency and BSFC are compared. BSFC increases and thermal efficiency decreases with the percentage increase in the blends at higher loads. At part loads, biodiesel blends are more efficient. Emission contents like carbon monoxide, carbon dioxide, hydrocarbon, oxides of nitrogen and smoke density are recorded. For B10 and for B20 blends these contents are more comparable to diesel fuel.
Heat Transfer Enhancement and Pressure Drop Performance for Fin and Tube Compact Heat Exchangers with Radiantly Arranged Rectangular Winglet-Type Vortex Generators
Authors: Raj Singh Rimjhim , Thakur H.C.
Published: January 2019

In this paper, heat transfer enhancement has been numerically investigated for fin and tube compact heat exchangers with radiantly arranged rectangular winglets and has been compared with the existing structures. In the proposed structure, there are total 12 winglets, 3 on each tube arranged radiantly with an attack angle of 60ï‚° each. Investigation has been carried out on low Reynolds number from 400-800 heat transfer is compared with other structures without winglet as baseline arrangement, prevailing rectangular winglet arrangement and wavy down rectangular winglet arrangement. The simulation results show that the radiantly arranged winglet that guides the fluid from main flow to the wall creates collision and leads to turbulence behind the tube. It is found that newly proposed structure with radiantly arranged winglets has the highest heat transfer rate, as compared to the existing structures and this can replace the previous structures. The heat transfer characteristics and flow structures are numerically investigated in ANSYS.
All-cause mortality of metabolically healthy or unhealthy obese: risk stratification using myocardial perfusion imaging
Authors: Lorenzo Andrea De , Carazza Mariana , Lima Ronaldo
Published: January 2019

Introduction

There is still controversy about the favorable prognosis of “metabolically healthy” (MH) obese. This study evaluated mortality and the use of myocardial perfusion scintigraphy (MPS) for risk stratification of MH or metabolically unhealthy (MU) obese or nonobese patients.

Material and methods

Patients without dyslipidemia, hypertension, or diabetes were considered MH, and those with ≥ 1 of these risk factors were considered MU. The MPS was categorized as normal, abnormal or ischemic. Patients were followed for 4.0 ±1.0 years for all-cause death.

Results

Of 2450 patients, 613 were obese. The MH obese patients less often had ischemia than MU obese, but there was no significant difference in the prevalence of ischemia compared to all nonobese. The annualized death rate of MH obese was 1.3% and of nonobese 1.0% (p = 0.4). An abnormal MPS and the MU status were independently associated with death, with hazard ratios of 1.85 and 1.72, respectively. A normal MPS identified patients with low risk among all subgroups; annualized rates of death were 1.0%, 1.1% and 1.0% for all nonobese, MH obese and MU obese, respectively (p = 0.63).

Conclusions

The annualized death rate of MH obese patients was not significantly different from that of nonobese individuals. Myocardial perfusion scintigraphy was able to stratify prognosis in the overall patient population. These data may be helpful to identify high-risk individuals, thereby improving patient management.
Pulse wave velocity and its gender-related associations with cardiovascular risk factors in a high cardiovascular risk population
Authors: Zemtsovskaja Galina , Abina Jelena , Meigas Kalju , Pilt Kristjan , Viigimaa Margus
Published: January 2019

Introduction

Associations found between pulse wave velocity (PWV) and cardiovascular risk factors (CVrF) are diverse. We aimed to evaluate whether differences in PWV and its associations with CVrF in a high cardiovascular risk population exist between genders and between the whole population (WHgr) and groups of apparently healthy (AHgr) and those of hypertensive, obese or diabetics (Rgr).

Material and methods

Pulse wave velocity measured by Arteriograph was investigated in 805 adults aged 20–65, randomly selected from the Tallinn Population Register.

Results

Pulse wave velocity was the highest in Rgr and no differences were found between genders of the same group. In women of WHgr and AHgr age and SBP with addition of BMI and apolipoprotein B (ApoB) were associated with 54% and 48%, and without ApoB in Rgr with only 30% of PWV values. In men aged ≥ 50 of WHgr with elevated SBP odds ratios for increased PWV were 25.3 and 3.5, in Rgr 21.2 and 2.2, in those aged ≥ 50 AHgr 28.4. In women aged ≥ 50 of WHgr with elevated SBP and diabetes odds ratios were 5.5, 4.9 and 4.0, in Rgr with elevated SBP and diabetes 3.6 and 3.7, in those aged ≥ 50 AHgr 29.3.

Conclusions

The associations of ApoB and BMI with PWV and diabetes with elevated PWV indicative of increased aortic stiffness were unique for women. Aging and SBP were related to PWV even in AHgr, although age ≥ 50 years in Rgr women and normal SBP in AHgr were not associated with elevated PWV.
Effects of selenium supplementation on paraoxonase-1 and myeloperoxidase activity in subjects with cardiovascular disease: the Selenegene study, a double-blind randomized controlled trial
Authors: Mirmohammadsadeghi Amirhossein , Gharipour Mojgan , Roohafza Hamidreza , Dianatkhah Minoo , Sadeghi Masoumeh
Published: January 2019

Introduction

We previously highlighted the potential link between supplementation with selenium, as an antioxidant trace element, and changes in the levels of paraoxonase (POX1) and myeloperoxidase (MPO), as an antioxidant enzyme, in patients with documented cardiovascular disease (CVD). The aim of this study was to determine the effects of selenium supplementation on POX1 and MPO activity in patients with cardiovascular diseases (CVDs).

Material and methods

A total of 160 eligible patients were enrolled in the study. After performing some laboratory tests, including the measurement of blood selenium, triglyceride, cholesterol, and low- and high-density lipoprotein levels, the patients received 200 mg tablets of either selenium yeast or placebo. The medicines were taken orally, once daily after a meal for 60 days. Four weeks after the initial visit, the patients were invited for a follow-up visit, and interviews and non-laboratory evaluations, similar to those performed at baseline, were repeated. Compliance of patients for using selenium and placebo was measured by telephone. Medication compliance rates were monitored by telephone. The final assessments were conducted eight weeks after the beginning of the study.

Results

There was no significant difference in cholesterol levels between intervention and control groups (p = 0.87). No significant changes in selenium levels were observed in either the selenium or the placebo group after the intervention (p = 0.44 and p = 0.48, respectively). The two groups had a significant difference in terms of POX1 level (p = 0.039). No such difference was present in the case of MPO levels. Moreover, comparison of the values before and after the intervention showed no significant differences in the mean levels of any of the measured parameters.

Conclusions

According to the obtained results, the increased POX1 levels after selenium supplementation could be attributed to the positive effect of selenium on inhibiting lipid peroxidation as part of the complicated pathophysiology of CVD.
Comparison of results of whole-body magnetic resonance imaging scans and traditional imaging modalities in diagnostic management of chronic recurrent multifocal osteomyelitis
Authors: Sułko Jerzy , Oberc Artur
Published: January 2019

Introduction

The diagnosis of chronic recurrent multifocal osteomyelitis (CRMO) is frequently the result of excluding other diseases. The only methods that provide images of the multicentricity of radiologically active foci are whole body bone scintigraphy (SCI) and whole body MRI (WBMRI). The objective of the study was to compare the results of WBMRI and traditional imaging modalities in CRMO.

Material and methods

The study group consisted of 20 children with the mean age of 9.5 years. WBMRI imaging was performed between June and December of 2014. The mean follow-up period after completion of the study was 35 months. All the patients included in the study were additionally subjected to examination of clinically active CRMO foci by computed tomography, classic radiographic diagnostic management and scintigraphy.

Results

All the patients manifested clinically active foci. In the group of the investigated patients, the highest number of foci in concordance with the clinical picture was noted in SCI – 29, followed by CT – 22 and WBMRI – 21, while plain X-ray yielded the lowest number of positive results – 12.

Conclusions

The results of the present study do not confirm the highest sensitivity of WBMRI in determining possible disease foci in CRMO as compared to other imaging modalities. Higher sensitivity in detection of radiologically active foci in CRMO was noted in bone system scintigraphy. During the 35-month follow-up, none of the WBMRI-detected radiologically active and clinically silent foci underwent clinical activation.
Comparison of moxifloxacin-based therapies and standard bismuth-based quadruple therapy for first-line treatment of Helicobacter pylori infection
Authors: Akpinar Muhammet Yener , Aksoy Evrim Kahramanoglu , Sapmaz Ferdane , Goktas Zeynep , Uzman Metin , Nazligul Yasar
Published: January 2019

Introduction

Helicobacter pylori antibiotic resistance continues to be an important issue for decisions regarding eradication treatment. The aim of our study was to compare the efficacy of two bismuth-containing quadruple regimens: one including moxifloxacin, and the other including metronidazole, tetracycline and triple therapy with moxifloxacin as a first-line regimen.

Material and methods

A total of 332 patients received three different regimens: (a) moxifloxacin-containing bismuth quadruple therapy, BMAR (bismuth subsalicylate 562 mg, BID, moxifloxacin 500 mg QD, amoxicillin 1 g, BID, rabeprazole 20 mg, BID); (b) standard bismuth quadruple therapy, BTMR (bismuth subsalicylate 562 mg, BID, tetracycline 500 mg, QID, metronidazole 500 mg, TID, rabeprazole 20 mg, BID, for 2 weeks); or (c) moxifloxacin-containing triple therapy, MAR (moxifloxacin 500 mg, QD, amoxicillin 1 g, BID and rabeprazole 20 mg, BID).

Results

The eradication rates of the three groups using ITT analysis were BMAR 93.6%, BTMR 78.4% and MAR 90.8%. Rates were 98.9%, 87% and 99.1%, respectively, using PP analysis. The eradication rate was significantly higher in the BMAR group than in the other groups based on ITT analysis (p < 0.001). There was no significant difference between the BMAR and MAR groups based on PP analysis (p > 0.05); however, the eradication rate was significantly higher in both of the groups than in the BTMR group (p < 0.001).

Conclusions

Moxifloxacin-containing regimens are efficacious choices for first-line therapy of H. pylori eradication. Adding bismuth therapy to moxifloxacin-based therapies only increases adverse events without increasing the eradication rate.
Dilatation of benign anastomotic strictures after colorectal surgery with bougies
Authors: Dincer Mürşit
Published: January 2019

Introduction

The development of benign anastomotic strictures after colon-rectum operations is one of the complications. Endoscopic balloon and bougie dilatations are applied primarily in the treatment. In this study, we aimed to investigate the causes of benign anastomosis after low anterior resection and present the results of bougie dilatation in anastomosis stenosis.

Material and methods

The patients with anastomosis after low anterior resection in the last year were retrospectively evaluated. Anastomosis and dilatation after the development of the cases were examined. The patients who underwent bougie dilatation were included in the study. Demographic characteristics of the patients, indications of surgery, causes of stenosis, duration of development of stenosis, level of stenosis and number of operations were recorded. Dilatation was performed under sedation. Polyvinyl bougies with a guide wire were used during the procedure. The dilatation process was continued starting with the smallest diameter bougie that could pass through the anastomosis, up to the maximum diameter bougie.

Results

After low anterior resection, seven patients with anastomosis were included in the study. In four cases, the only successful session was after the bougie dilatation. In one case, anastomosis was detected after multiple operations. In two cases, the bougie dilatation failed.

Conclusions

As a result, bougie dilatation in anastomotic stenosis is a feasible, effective and safe minimally invasive method with a low complication rate.
Mentalization in borderline individuals: an attempt to integrate contradictory research results
Authors: Jańczak Monika
Published: January 2019

Researchers have been striving to explore the functioning of patients with borderline personality disorder from the perspective of their capacity to mentalize. Analyzing the expanding body of literature, it is nevertheless difficult to reach a clear conclusion. There are studies that confirm mentalization deficits in this group; however, there are also reports suggesting better or at last equal mentalizing in borderline individuals compared to controls. This paper discusses a hypothetical explanation of these contradictory results by analyzing three fundamental issues. It is assumed that: (1) different aspects of mentalization are measured in studies – some of them are disordered, while others remain intact in borderline individuals; (2) mentali­zation can be understood not only as a trait but also as a state, and its level may differ in the same person depending on measurement conditions; (3) the borderline group is heterogeneous in terms of mentalizing because other variables determine the level of this capacity.
System Dynamics Approach to Mitigating Skilled Labour Shortages in the Construction Industry: A South Africa Context
Authors: Aiyetan Olatunji Ayodeji , Dillip Das
Published: January 2019

Skilled labour shortage in construction industry is a major challenge in South Africa. Therefore, the objective of the study is to assess the factors that cause skilled labour shortage, its consequent effects on the construction industries and how the scenario can be improved. The study was conducted by considering construction industry in the Eastern Cape of South Africa and using a survey research method and conceptual System Dynamics (SD) modelling. Findings reveals that investment, wage challenges, talent management, work environment, training, experience, and Government policy are the important challenges for the skilled labour shortage. Inadequacy of skilled labour considerably impacts the quality of work, productivity, and scheduling. The causal loop diagrams show that enhancement in investment in the labour wages will strengthen the availability of skilled labourers leading to higher productivity, and vice versa. Talent management based on appropriate recruitment and retention policy, staff development programmes and investment in these aspects will augment the skilled labour pool. Also, a better work environment through a policy of health and safety, investment in working condition and supported by Government policy will reduce the attrition of the labourer because of job dissatisfaction, which consequently will reduce the skilled labour shortage in the industry.
Growth in mid-monsoon dry phases over Indian region:
Prevailing influence of anthropogenic aerosols
Authors: Chakraborty Rohit , Guha Bijay Kumar , Talukdar Shamitaksha , Venkat Ratnam Madineni , Maitra Animesh
Published: January 2019

Abstract. A detailed investigation on the potentially drought prone regions over India has been presented in this study based on the balance between precipitation and potential evapotranspiration (PET) during the South West Asian mid-monsoon season. We methodically introduce a parameter named dry day frequency (DDF) which is found suitable to present the drought index (DI) in mid-monsoon season hence strongly associated with the possibility of drought occurrences. The present study investigates the probable aspects which influence the DDF over these regions revealing that the abundance of anthropogenic aerosols especially over urbanized location have prevailing role on the growth of DDF during last few decades. The prominent increasing trend in DDF over Lucknow (26.84° N, 80.94° E), a densely populated urban location situated in the Indo-Gangetic plain, strongly reflects the dominant association of man-made aerosols with the increasing dry phase occurrences. Increase in DDF (~ 90 %) during the last 60 years is observed over this urban area compared to a broader region in its surroundings. In addition, periodic impacts of synoptic scale phenomena like ENSO (El Niño–Southern Oscillation) or SSN (Sun spot number) become weaker when the study location is downscaled towards an urbanized region. However, there still remains some unclear role of air-mass transport on DDF over the potential drought prone region of north-west India. Finally, when long term projections of DDF are drawn using the high urbanization scenario of RCP 8.5 a huge rise in dry days are seen during mid-July to mid-September (reaching up to 50 dry days by the year 2100 over Lucknow) which will be a very crucial concern for policy makers in future.
Bathymetric maps from multi-temporal analysis of Sentinel-2 data: the case study of Limassol, Cyprus
Authors: Evagorou Evagoras , Mettas Christodoulos , Agapiou Athos , Themistocleous Kyriacos , Hadjimitsis Diofantos
Published: January 2019

Abstract. During the last years, various methods and techniques have been used to
estimate the seafloor topography with high accuracy. The topography is
considered an important component for marine applications since several
activities and infrastructures are being carried out at the bottom, column
and surface of the sea. In this, study, freely and open distributed optical
satellite images were used to obtain bathymetric data for shallow waters,
(until 30 m below sea level) based on timeseries analysis of multispectral
Sentinel-2 datasets. The ratio transform algorithm was implemented for twelve
(12) monthly images covering thus a whole year. The different generated
Digital Terrain Models (DTMs) were compared with high resolution LIDAR
measurements. The results showed that bathymetry can be obtained from
satellite data within a Root Mean Square Error (RMSE) ranging from 1.39 up to
2.56 m while more accurate results were generated during the summer period.