bluuebunny/crossref_metadata_2025 huggingface dataset:
L’analyse du non-recours : au-delà du modèle de la relation de service
Authors: Warin Philippe
Published: June 2016

La réalisation des relations de service n’a rien de systématique. Elle se confronte parfois à une résistance des usagers qui produit du non-recours. Dès lors, le modèle de la relation de service doit être écrit autrement s’il veut en tenir compte. En l’espèce, le travail de l’agent prestataire ne consiste pas seulement à agir sur ses rapports avec l’usager, mais aussi avec l’offre proposée. L’analyse du non-recours a donc besoin d’un modèle d’analyse distinct car elle conduit à considérer qu’il n’y a pas d’usager sans tenir compte de son rapport à l’offre, à son contenu normatif au-delà même de l’acte de la prestation. De ce point de vue, le modèle proposé par l’auteur de « rapport social de service » offre une meilleure prise en compte.
Pimavanserin: An Inverse Agonist Antipsychotic Drug
Authors: Howland Robert H.
Published: June 2016

Approximately all clinically useful antipsychotic drugs have known activity as dopamine receptor antagonists, but many of these drugs also are inverse agonists at the serotonin-2A (5HT2A) receptor. Pimavanserin is an inverse agonist at the 5HT2A receptor, with a lower binding affinity at the serotonin-2C receptor and sigma 1 receptor, but no significant binding to dopamine or other receptors. Because of its unique pharmacology, pimavanserin was approved for the treatment of psychosis associated with Parkinson's disease, and it has a low risk for exacerbating motor symptoms compared to standard antipsychotic medications. Whether pimavanserin can treat psychotic symptoms in schizophrenia, psychotic depression, psychotic mania, delirium, or drug-induced psychosis, is not known. Based on its inverse agonist effect at 5HT2A receptors, pimavanserin may have potential for treating symptoms associated with the use of hallucinogen drugs and for treating akathisia associated with antipsychotic medications. [
Journal of Psychosocial Nursing and Mental Health Services, 54
(6), 21–24.]
Les mécanismes de jeu appuyés par les réseaux sociaux dans les communautés web 2.0 d'apprentissage des langues
Authors: Zourou Katerina , Lamy Marie-Noëlle
Published: June 2016

Cette étude examine la dynamique de jeu qui s'observe dans certains réseaux d'apprentissage des langues, et son potentiel pour l'apprentissage linguistique et le soutien par les pairs. Notre terrain comprend quatre catégories de communautés d'apprentissage des langues. Les mécanismes de jeu inscrits dans la conception-même de l'activité constatée dans chacune de ces catégories font l'objet d'une triple interrogation concernant le rôle de l'apprenant, les comportements attendus et la posture d'apprentissage. Notre étude se situe dans le contexte du web 2.0 et cible les évolutions actuelles de la "collaboration collective" ("crowdsourcing", Howe, 2006) qui simultanément encourage l'investissement par l'apprenant d'un espace de liberté et mobilise le talent inhérent de la "foule", que toutefois peuvent exploiter ensuite des sociétés commerciales. Nous démontrons que les mécanismes du jeu précontraignent l'activité de l'utilisateur en facilitant chez les concepteurs des sites une approche subtilement incitative, qui n'est pas clairement déclarée à l'utilisateur au moment de son inscription. Nous montrons que c'est la dynamique de jeu qui induit toute l'activité en ligne, qu'elle peut promouvoir l'apprentissage, mais aussi profiter commercialement aux start-ups du web 2.0 qui sont à l'origine de ces communautés.
Optimization of Water Scrubbing Method for Enhancement of Biogas Quality through Base Solutions Addition
Authors: Sakke Tira Hendry , Padang Yesung Allo , Rachmanto Tri , Syahida Ahmad Alfan
Published: June 2016

The addition of base NaOH and KOH solutions and the application of an air stone and a stirrer to develop turbulence in water scrubbing method were carried out to study the purification process of raw biogas. Various concentrations of the base solutions and constant stirrer speed was applied. The work results showed that the best performance in increasing CH4 content, about 70% improvement, was reached with the addition of NaOH on 2% concentration. On the other hand, about 96% and 100% improvement for CO2 and H2S respectively were obtained under 2% NaOH addition coupled with a stirrer. The addition of base solutions was very effective to increase absorbent pH level, thus maintaining absorption process in longer duration and prevented saturation of absorbent. Moreover, the application of a stirrer in packed bed column further improved the biogas quality. The improvement was resulted from the generated biogas bubble and turbulence which led to prolong contact time between absorbent and biogas.
Modeling of Well Service and Workover to Optimize Scheduling of Oil Well Maintenance
Authors: Kromodihardjo Sudiyono , Kromodihardjo Ergo Swasono
Published: June 2016

Well maintenance (well service and workover) is an operation needed by oil company to guarantee the optimum productionof its oil well.Well maintenance is performed using large equipment called hydraulic workover unit (HWU-Rig) which is available in limited number. Scheduling sequence of the HWU-Rig to do well service must meet the goal of the maintenance that is to minimize the loss of oil well production due to well breakdown. Thus minimizing breakdown time of well with high rate production is a priority. However, scheduling secuence of the HWU-Rig to perform its task for few days ahead become complicated due to the numerous alternatives of secuence to choose. Each alternatives of sequence yields a certain production loss. Arbitrarily scheduling sequence may not yield the goal og minimizing the loss of well production. This research was done by analyzing workover scheduling system and data from Kondur Petroleum such as well location, well production rate, and service time needed to be performed on wells. Algorithm to create schedulling sequence was developed in the research. The algorithm was then implemented in discrete simulation software, and yield the result of absolute global optimal solution, near optimal solution and local optimal solution of the HWU scheduling problem.
Convective Regimes on Porous Media within Sudden Changed Channel due to Tangential Gas Flow
Authors: Siswanto Eko , Veriyawan Rahana Angga , Choiron Moch. Agus , Ryuichi Nagata , Katsurayama Hiroshi , Yasuo Katoh
Published: June 2016

Study of lateral heat distribution in porous media caused by tangentially heated air flow is presented. Purpose of present study is to investigate effect of air velocity streamed tangentially, through a sudden enlarged-contracted channel, over a porous media layer toward heat distribution inside the layer. Air with temperature 373 K, as a heat source, is streamed over upper-facing of the porous layer, while its intake velocities are varied respectively at 0.5 to 2.5 m/s. Lower-facing of the porous layer, temperature is held on 313 K constant, as a heat sink. The consolidated porous layer is made from aluminum with porosity 38%. Important informations are obtained. Sudden enlarged-contracted channel generates non-linear heat transfer inside the porous media, whereas the suddenly enlarged channel enhances the molecular conductance, and the sudden contracted one increases the convective conductance.Thislaminar tangential gas flow yields the heat transfer takes respectively on free-, forced-, and combined-convective regime. It is also known that the combined convection is due to air flow at average Reynolds number 231.26.
Experimental Tests of the Load-Bearing Capacity of the Bottom Reinforcement Bars Passing over the Column
Authors: Wieczorek Barbara
Published: June 2016

In the paper the results of laboratory tests performed on a simplified model of a slab-column connection were presented. The aim of investigations was to find out at which value of the load the destruction of such a connection occurs due to a rupture of the bars above the column. In respective models the column was situated axially or eccentrically with respect to span of bars. In each case the reinforcement passing above the column consisted of bars with a diameter of ø8 mm, ø12 mm or ø16 mm. The obtained results of laboratory tests and calculations permitted to determine the relations between the exerted load and the displacement of the column in time and also were compared with the guidelines contained in the standards CSA A23.3 and ACI 352R. Based on the results, the reduction of the load bearing capacity of the reinforcement bars due to bending was determined.
Seismic Assessment of Unreinforced Masonry Buildings
Authors: Avila-Haro Jorge Arturo , Elshoura Ahmed Saad , Maca Jiří
Published: June 2016

The first case study used in this work is an existing seven-storey unreinforced masonry building (representing a typical residential building located in the district of L ́Example in Barcelona). The accuracy of the non-linear static procedures was evaluated by comparison with non-linear dynamic analyses for seven ground motion records and different levels of seismic intensity. The results obtained from the analyses showed good performance of the static pushover methods on the analysed building. The second case study used in this work is a two-storey unreinforced masonry building which was tested at ELSA in Ispra, Italy. First a modal response spectrum analysis was carried out. Subsequently, non-linear static analysis was performed using two different computer programmes. The results of the present work were compared with experimental results.
Analysis of the Natural Frequencies of a Plexiglass Plate
Authors: Zabakova Vrablova Kristina , Jendzelovsky Norbert , Konecna Lenka
Published: June 2016

In this article we verified the methodology of experimental measurements on plexiglass plate. We compared the natural frequencies of plate. The experiment was done under laboratory conditions using a portable dynamic measuring apparatus. We compared the experimental results with the results from software ANSYS based on finite element method.
Post-Tensioned Composite Bridge: Reliability-Based Optimization of Selected Design Parameters
Authors: Slowik Ondrej , Lehký David , Šomodíková Martina , Novák Drahomír
Published: June 2016

In the paper small-sample double-loop optimization method is employed to find selected design parameters of a single-span post-tensioned composite bridge to ensure its reliability and load-bearing capacity. The selected approach consists in nesting the computation of the failure probability with respect to the current design within the optimization loop. The analyzed bridge is made of precast post-tensioned concrete girders, each composed of six segments that are connected by the transverse joints. Bridge spatial deterioration brings uncertainty into actual values of concrete strength in transversal joints and of actual loss of pre-stressing. Due to their significant effect on the bridge load-bearing capacity, both were considered as uncertain design parameters with the aim to find their critical values corresponding to desired reliability level and load-bearing capacity.
Analysis of Dynamic Parameters of Rail Fastening by Born-Jordan Transformation
Authors: Smutny Jaroslav , Pazdera Lubos
Published: June 2016

The method using Born-Jordan transformation has been developed for the evaluation of response signals obtained by rail fastening analysis. In the paper the laboratory measurements and dynamic parameters analyses of flexible fastening of Vossloh SKL14 type have been descripted. This method can also be used for designing new fastening systems and their parts, for comparison of various rail fastening types and so on.
Analysis of Abrasive Particle Trajectories during Single-Sided Lapping Process with Driven Conditioning Ring
Authors: Barylski Adam , Piotrowski Norbert
Published: June 2016

In this paper new kinematics systems were studied for a single lapping process. In order to ensure the constant profile wear of the tool a standard kinematic system can be changed. Lapping is carried out by applying loose abrasive grains between two surfaces and causes a relative motion between them. The result is a finish of multi-directional lay. During process, the mechanism of surface formation are decisively affected by a pressure force, a process time and a motion type of grains. It has been proven, that providing the additional movements of the conditioning ring affects the profile wear of the lapping plate. First of all, the kinematics equations of the lapping process have been developed and the process has been simulated. A type of the abrasive particle trajectories in standard single-disk lapping depends on rotational speed ratio of a tool and a conditioning ring. In addition, two new kinematic systems were presented: with radial and secant movement of the conditioning ring. Finally, comparison and analysis of abrasive trajectories were carried out.
The New Approach to Optimization of Production – Technological Base of a Public Transport Enterprises Network on an Example of City Hanoi
Authors: Rementsov Andrey Nikolaevich , Egorov Victor Akimovich , Manh Nguen Huang
Published: June 2016

In the article application of queuing systems model in the field of operation of motor transport is presented. The system of maintenance service (MS) and operating repair (OR) of the cars on technological base is considered as multichannel multiphase queuing system. The mathematical model allows to receive necessary parameters of system MS and OR and to optimize them on technical-economic criterion.
Causes of Engine Oil Humidification
Authors: Laushkin Andrey Vyacheslavovich , Khaziev Anvar Ashatovich , Solntsev Alexey Aleksandrovich
Published: June 2016

The article discusses the causes of humidification of engine oil from vehicles and provides quantitative estimates of transferring of water into oil.
The Simulator for the Gas Fuel System – Calibration Process
Authors: Panov Yury Vladimirovich , Pronnikov Aleksey Nikolaevich , Lapinski Krzysztof
Published: June 2016

The article reviews issues of training process effectiveness increase by means of implementation and adaptation of the simulator of gas injection control system for petrol engine performed by applying LPG TECH Co technologies, when technical training relates to the use of alternative fuels on the motor transport.
Mathematical Model of Tire Life Calculation in Real Conditions
Authors: Yanchevskiy Vadim , Yanchevskaya Elena
Published: June 2016

In this article we answer questions on how to control tire life. We propose the method of calculating the standard mileage rate of the tires in specific conditions. We describe how to determine the remaining mileage of each tire in operation and therefore determine the date of its decommissioning. And in this way make the balanced forecast of the tires demand for the future period to replace the unusable tires.
Energy and Exergy Analysis of Thermal Energy Storage Prototype by Using Concrete Material in Thailand
Authors: Boonsu Rungrudee , Sukchai Sukruedee
Published: June 2016

The research was performed on thermal energy storage prototype in Thailand. Concrete was used as the solid media sensible heat material in order to fulfill local material utilization which is easy to handle and low cost. Saturated steam was used for heat transfer fluid. The thermal energy storage prototype was composed of pipes embedded in a concrete storage block. The embedded pipes were used for transporting and distributing the heat transfer medium while sustaining the pressure. The heat exchanger was composed of 16 pipes with an inner diameter of 12 mm and wall thickness of 7 mm. They were distributed in a square arrangement of 4 by 4 pipes with a separation of 80 mm. The storage prototype had the dimensions of 0.5 x 0.5 x 4 m. The charging temperature was maintained at 180°C with the flow rates of 0.009, 0.0012 and 0.014 kg/s whereas the inlet temperature of the discharge was maintained at 110°C. The performance evaluation of a thermal energy storage prototype was investigated in the part of charging/discharging. The experiment found that the increase or decrease in storage temperature depends on the heat transfer fluid temperature, flow rates, and initial temperature. The energy efficiency of the thermal energy storage prototype at the flow rate of 0.012 kg/s was the best because it dramatically increased and gave 41% of energy efficiency in the first 45 minutes after which it continued to rise yet only gradually. Over 180 minutes of operation time, the energy efficiency at this flow rate was 53% and the exergy efficiency was 38%.
Availability Study of Large Scale Grid Connected Photovoltaic Power Plants in Thailand
Authors: Phanukan Phairot , Ketjoy Nipon
Published: June 2016

This article presents the availability of 4 large scale grid connected photovoltaic (PV) power plants that located in Petchaboon, Nakhon Sawan, and Chai Nat province of Thailand. These power plant size are 4.5 MW and 6.5 MW. In addition, they are constructed with the same platform, component, and commercial operation date (COD) in the same year. The data were collected during 1st August 2012 to 31st October 2014. The study result found that availability of these power plant is over 97 % every year except Nakhon Sawan 1 plant in the first year. The internal unavailability trend is quickly reduce while external unavailability is randomly fluctuation.
Development of Mathematical Equation for Photovoltaic Array Internal Resistance Measurement under Operating Conditions
Authors: Khaosaad Nattawut , Ketjoy Nipon , Vaivudh Sarayooth , Sriprapha Kobsak
Published: June 2016

A novel technique has been developed for PV array internal resistance measurement while keeping the plant in operation in contrary to flash test or basic equation (Eb) for which the modules need to be disconnected from the system. We present an equation developed for the array’s internal resistance measurement for PV technologies namely Amorphous Silicon (a-Si), Poly Crystalline Silicon (p-Si) and Hybrid Crystalline Silicon (HIT). Monthly Measured I-V characteristic curves of PV Array were converted to Standard Test Conditions following the IEC 60891 standard. Multiple regression analysis and linear regression technique were used to develop the equation for estimating the PV array internal resistance. The developed equations (Ed) will find the relationships of the 4 variables that are Series resistance (Rs), Shunt resistance (Rsh), maximum voltage (Vm) and maximum current (Im). The results revealed that the Ed can be applied to measure the PV array internal resistance value with low error margin than Eb. The series resistance calculated using Ed is higher than Eb about 1.11 %, 1.88 % and 0.87 % for a-Si, p-Si and HIT respectively. The shunt resistance calculated using Ed is higher than Eb about 0.07 %, 0.09 % and 0.09% for a-Si, p-Si and HIT respectively.
Determination of Biodiesel Prices in Thailand
Authors: Laung-Iem Kornkamol , Thanarak Prapita
Published: June 2016

Biodiesel is a diesel equivalent fuel produced from biological feed stocks, acting as a substitute for petroleum or fossil diesel. Biodiesel production in Thailand began in 2005, with prices stabilizing after 2008. Biodiesel, along with other biofuels, plays a role in Thailand’s Alternative Energy Development Plan (AEDP). The purpose of this study is to examine factors in the Thai biodiesel prices (2009-2014). The study assessed factors in downstream biodiesel prices at consumer locations like gas stations. The price factors assessed in the study included ex-refinery prices, excise taxes, municipal taxes, oil fund contributions, energy conservation fund conributions, marketing margin and exchange rate (USD). Regression results showed that all of these factors were significant (r2 = 0.867). The implication of the study is that while most of the retail price of biodiesel in Thailand is attributable to cost factors, there is some unexplained variance in price. This offers an opportunity for future research.
Application of Interval Arithmetic in Numerical Modeling of Microscale Heat Transfer
Authors: Mochnacki Bohdan , Piasecka-Belkhayat Alicja
Published: June 2016

Thermal processes in the domain of a thin metal film which are subjected to a laser pulse are considered. The mathematical model based on the dual phase lag equation (DPLE) results from the generalized form of the Fourier law. The governing equation is supplemented by appropriate boundary and initial conditions. The numerical model of metal heating is constructed using the explicit scheme of the finite difference method for hyperbolic equations. The thermophysical parameters of the material (gold) are treated as interval numbers and at the stage of the FDM algorithm construction the rules of interval arithmetic are applied. In this way the numerical solution is obtained in the fuzzy form. Such an approach gives interesting practical information about the course of the process because the values of thermophysical parameters collected in the literature often differ significantly. In the final part of the paper an example for a numerical solution is presented.
Numerical Study of External Flow over Ducts with Various Cross-Sections
Authors: Maleki Erfan , Sadrhosseini Hani
Published: June 2016

In this article a comprehensive numerical study is performed to compare the effect of fluid flow across a duct with various cross sectional shapes and with different velocities of the flow. Circular, elliptical and rectangular cross sections have been chosen for the ducts and air flows across them with four values of low Reynolds numbers in the range of Re = 1 to Re = 1000. Continuity and momentum equations with proper boundary conditions are solved in two dimensions. Streamlines, pressure distribution and Velocity profiles are obtained and creation of vortices, boundary layers, separation region, wake region, reattachment point and stagnation points are studied in detail and the results are compared for various cases. The value of the Reynolds number which the flow transits from steady to unsteady has been compared for the different cross sectional shapes.
Curvature Effect Radius Analysis in a Two Flow Leak Pipeline
Authors: Sarmento Lígia Rafaely Barbosa , Barbosa E.S. , Leite B.E. , Tavares Daniela Passos Simões de Almeida , de O. Buriti Cidronia Janiclebia , de Farias Neto Severino Rodrigues , Gilson Barbosa de Lima Antonio
Published: June 2016

The oil industry has sought to minimize the environmental impact from mining activities and oil transportation. Oil transportation by pipelines is subject to failures and leaks which cause financial losses and environmental damage, often irreparable. Currently, the study of leaks in pipelines has attracted the attention of many researchers. The aim of this study is to evaluate the influence of the curved curvature radius connection in pipeline leakage. We used a mathematical model of multiphase flow to describe the two-phase flow, based on the particle model. Oil is the continuous phase while water a dispersed phase. To model this effect we used the turbulence model SST. All simulations were carried out using the Ansys CFX ® commercial code. Results of the total pressure and pressure drop are presented and discussed. The results confirm the influence of the bending radius of curved connection on the behavior of the total pressure and the total pressure drop in two-phase flow in pipelines with and without leakage.
Analysis of Two-Phase Pressure Drop Fluctuation Characteristics in a Single Mini-Channel
Authors: Zhang Bei Chen , Li Qing Lian , Wang Yuan , Zhang Jian Qiang
Published: June 2016

Two-phase pressure drop fluctuations during flow boiling in a single mini-channel were experimentally investigated. Degassed water was tested in circular cross section mini-channels with the hydraulic diameter of 1.0 mm at liquid mass fluxes range of 21.19-84.77 kg m-2 s-1 and heat fluxes of 0~155.75 kW m-2. Effects of heat flux and mass flux on pressure drop fluctuations were discussed based on the time and frequency domain analysis of the measured pressure drop. Two types of fluctuations were identified, which are the incipient boiling fluctuation (IBF) and the explosive boiling fluctuation (EBF) respectively. The IBF is a low frequency low amplitude fluctuation, which relates to the bubble dynamics when incipient boiling occurs. It is sensitive to the thermal and flow conditions. With the increase of heat flux and mass flux, the IBF is suppressed. The EBF is a low frequency high amplitude fluctuation, which occurs near the critical heat flux.
Continuous-Flow DNA Amplification Device Employing Microheaters
Authors: Chen Jyh Jian , Sheu Tsung Sheng , Wang Yuan Jyun
Published: June 2016

Since polymerase chain reaction (PCR) was invented, it has become one of the most significant approaches for generic identification during the last few decades. PCR is a useful procedure to magnify the number of copies of a specific DNA template exponentially. Integrated microfluidic DNA amplification devices that employ a serpentine polydimethylsiloxane microchannel, a glass cover with micro heaters and sensors, and a cooling polymethylmethacrylate channel are demonstrated in the present study. With the aid of commercial computational fluid dynamics software, we design the continuous-flow DNA amplification device. The influences of various chip materials, water cooling conditions and geometric parameters on the temperatures of the chip are expressed. Using the MEMS process, two micro aluminum heaters and sensors are fabricated. This device represents the first demonstration of Al heaters and sensors integrated in continuous-flow PCR microfluidics. The LabVIEW control module is used to manage the temperatures of the micro-domain heating. One important feature of this system is the temperature of the annealing zone is controlled by the flow rate of the fluid inside a water channel under the glass chip. The cooling channel cannot only provide great thermal insulation between two temperature zones at the opposite sides of the chip, but also improve the temperature uniformity at the chip center temperature zone. By utilizing an IR thermometer, the images of the surface temperature distributions are captured to show the effects of the employed microheaters and the cooling channel on the thermal field of the PCR device. Finally, we find the temperature regions generated in the present device are suitable for completing the PCR process.
Optimization of a Sensible Thermal Storage System by a Lumped Approach
Authors: Andriotty Tiago Haubert , Rodrigues Letícia J. , Rocha Luiz Alberto Oliveira , Schneider Paulo Smith
Published: June 2016

This study is focused on the optimization of a sensible thermal storage system subjected to a cyclic energy source. The objective is to minimize the system heat storage mass and its geometry to guarantee its operation within an admissible temperature range. The storage medium is modeled as a Lumped system and the working fluid by a non-capacitive energy balance. The storage medium is composed of an array of parallel flat plates submitted to an air stream. The optimization is based on an exhaustive search method. It is observed that the minimum heat storage mass is proportional to the mass airflow rate. An optimal relationship between the superficial heat transfer rate and the fluid flow inertia, given by the dimensionless parameter NTU, is found to be constant (4.03) and independent in respect to the mass flow rate. The system time constant was invariable (3,230 s) for the optimal relationship between the interface heat transfer rate and the system inertia.
Improvement on Aerodynamic Characteristics and Drag Reduction for Supermileage Cars with Wide View Field
Authors: Wu Pey Shey , Young Min Jho , Wu Jun Yun , Wang Chia Chian , Hu Hao Yu , Chang Chih Fei
Published: June 2016

Aerodynamic characteristics of three supermileage car chassis with new design concepts for improving the driver’s view field and driving comfort is investigated and compared with that of one with traditional low-height design. New car shapes with shorter axle distance and higher center of gravity are created. Feasibility of the new design is verified from the aspects of rollover safety, due to the maximum crosswind speed of 40 km/h, and the drag coefficient at straight driving up to 40 km/h. The analytical verification is conducted with a commercial CFD software. Comparing to the traditional design, the analysis shows that it is possible to obtain a lower drag coefficient and lower total drag, while rollover safety is still guaranteed, for a supermileage car with wider view field and taller appearance. Reduction of the form drag is intimately related to the decrease of velocity curl in the flow direction and the size of the vortices in the wake. Results of this study can provide new concepts that are different from those used in the past for the development of supermileage cars.
Comparative Measurements of the Thermal Properties of Solid Materials on a New Device and Using a New Non-Stationary Method
Authors: Kušnerová Milena , Gola Lukáš , Valíček Jan , Václavík Vojtěch , Harničárová Marta , Pandová Iveta , Koštial Pavol
Published: June 2016

The aim of the publication is the comparative measurements of changes in temperature of the significant material coefficient - thermal conductivity for newly developed construction materials (lightweight concrete). The aim is met by using a newly proposed method and a newly developed device by the approximation modelling of the temperature dependence of the thermal conductivity coefficient of the new composites and also the interpretation of measurement results in the context of optimally desired characteristics of thermal insulation concrete. Construction materials for residential buildings should have good thermal insulation properties, i.e. relatively low coefficients of thermal conductivity. With regard to the relatively most important property of concrete – strength, however, the reduction in thermal conductivity of concrete is limited. Thermal conductivity of concrete can be reduced very effectively by increasing its porosity; on the other hand, by increasing the porosity, the strength of concrete is significantly reduced. The publication, therefore, compares the results of temperature dependences of thermal conductivity for three newly designed concretes, namely in the context of their compressive strength.
Empirical Heat Transfer Correlations during Frost Deposition on a Triangular Tube Banks Arrangement
Authors: da Silva Raquel da Cunha Ribeiro , Sedano Carlos Salinas , Ismail Kamal A.R. , Delgado Maldonado Paúl Adrian
Published: June 2016

An experimental study was reported earlier on the development of frost formation by humid flow passing over the cylinder. In this study, dimensionless correlations used in previous experimental data, and reported empirical correlations of the Nusselt number, were used. This paper reports results of an experimental and numerical investigation where the emphasis was placed on obtaining empirical correlation for the Nusselt number. In this work some experimental results of the frost thickness around every cylinder in a triangular arrangement are presented, an estimated experimental correlation to find Nusselt number. This correlation is based on the experimental measurements in a wind tunnel situated in the Laboratory of Thermal storage and Fluids in the Mechanical Engineering Faculty at Unicamp. A numerical study is performed to study the frost formation in the cylindrical system.
Effect of Interfacial Heat Transfer Coefficient on Dendritic Growth and Microhardness during Horizontal Directional Solidification of an Aluminum-Copper Alloy
Authors: Barros A.S. , Silva Adrina P. , Ferreira Ivaldo Leão , Rocha O.L. , Moreira A.L.
Published: June 2016

This paper presents a theoretical-experimental study for the prediction of the interfacial heat transfer coefficient during the horizontal directional solidification of an Al-3wt.%Cu alloy on water cooled stainless steel chill under transient heat flow conditions. Eight thermocouples were connected with the casting and the time-temperature data were recorded automatically. The thermocouples were placed at 5, 10, 15, 20, 30, 50, 70 and 90 mm from the metal-mold interface. A numerical technique which compares theoretical and experimental thermal profiles was used to measure the heat transfer coefficient values. This has permitted the evaluation of the variation of this thermal parameter along the solidification which is represented by a power equation that shows the time dependence during the process given by hi = constant (t)-n, which represents the best fit between the experimental and calculated curves. The obtained results also include the variation of both primary and secondary dendritic arm spacings of alloy analyzed as a function of heat transfer coefficient. These dendrite arm spacings were found to decrease as the values of this coefficient are increased. Finally, an experimental law of the Hall-Petch type is proposed relating the resulting microhardness to the heat transfer coefficient investigated.
Identification of Casting Conditions Influence on the Structure and Properties of Al-Si-X Alloy Castings by Experimental and Virtual Way
Authors: Ignaszak Zenon , Hajkowski Jakub
Published: June 2016

The paper describes influence of the structure type and its parameters on the mechanical properties of cast products (not subjected to plastic forming), made out of Al-Si-X alloys. The special attention has been focused on the dendritic structure parameters: dendritic arms spacing of the first order (DAS 1) and the second order (DAS 2). The results of investigations of mechanical properties of the test castings made using three basic casting technologies: gravity sand casting (GSC), gravity die casting (GDC) and high pressure die casting (HPDC), are presented. All the castings were made out of the same AlSi9Cu3 alloy. The test castings (adherent samples and separately cast samples) were subjected to a static tensile test and their mechanical properties were determined. In the next stage, the samples fractures and zones near the fractures (metallographic specimen) were subjected to visual testing, penetrating testing PT and metallographic microscopic tests. The microstructure, including the size of the DAS 2, was determined. Evaluation of the porosity state was also undertaken. A customer casting was also manufactured and subjected to the metallographic, tomographic (CT) and strength tests. The castings solidification simulation tests were performed for all the three casting technologies (GSC, GDC and HPDC) using the Nova Flow &Solid system. The results were used for estimation of the correlation between the cooling rate of the particular casting solidifying in the above mentioned mould types and for the DAS size. The coupled influence of the structure parameters on the mechanical properties, regarding the occurrence of porosity, was also analyzed.
Identification of the Moisture Distribution in the Intensively Heated Porous Sand Mould
Authors: Ignaszak Zenon , Popielarski Paweł
Published: June 2016

The problem presented in the paper concerns physical properties of porous multi-component mould material, into which a liquid metal is poured. The aim of the study was to determine the distribution of moisture in an intensively heated porous sand mould. In the past, several measuring methods have been developed, consisting in water evaporation out of a test sample (at a given time moment , the selected position coordinates of a sample), to determine the accumulated amount of water in the sample, which is a percentage of moisture content. The study described in the paper includes experiments of heating a green sand sample. Moisture distribution in a moisture transfer zone of the sample (temperature of the molding sand is approx. 100°C) was determined. In order to determine the moisture distribution, an original method was used. This method allows interfere in various layers of material of predetermined thickness, parallel to the surface of the mould in contact with a heat source. The classical measurement method (gravimetric method) was used for determining the moisture content of each layer.
Self and Chemical Diffusion in Liquid Al-Ag
Authors: Engelhardt Marc , Meyer Andreas , Yang F. , Simeoni G.G. , Kargl Florian
Published: June 2016

Self-and chemical diffusion coefficients are reported for molten Al-Ag on the Al-rich side of the phase diagram for Ag concentrations of up to 45at% and for pure liquid Ag. Temperature dependent Ag self-diffusion coefficients were obtained using quasi-elastic neutron scattering. Chemical diffusion coefficients were measured in situ by means of X-ray radiography of a long-capillary furnace. A detailed error analysis for the long-capillary experiments is reported. It is shown that perturbing effects can be detected and that accurate chemical diffusion coefficients can be measured with high precision. It is demonstrated based on Al-Ag20at% that the Darken equation appears to be valid for this system with a thermodynamic factor lower than unity. Furthermore, in Al-Ag it appears that Ag self-diffusion for small Ag concentrations is faster than Al-self-diffusion in liquid Al. This contrasts with observations made for other Al-based melts like Al-Ni and Al-Cu.
Microwave Drying of Sweet Potato (Ipomoea batatas (L.)) Slices: Influence of the Osmotic Pretreatment
Authors: Junqueira J.R.J. , Mendonça K.S. , Corrêa J.L.G.
Published: June 2016

Drying of sweet potato (Ipomoea batatas (L.)) slices by microwave with and without osmotic dehydration (OD) as a pretreatment was studied. Three osmotic agents (sucrose, sorbitol and fructose) were employed. Drying continued until final moisture content of 20 kg water 100 kg-1 sample. Two different microwave output powers (180 and 350W) were used. The drying kinetics was modeled by mathematical models from the literature. The use of OD and higher microwave power carried out to shorter drying time. Among the tested mathematical models, the Weibull distribution model presented good fitness for drying kinetics obtained in both microwave power.
Improving Surface Roughness of Steel Parts XC48 by Tribofinishing Process
Authors: Saidi D. , Bouaziz M. , Babichev A.P. , Djema M.A. , Hamouda K.
Published: June 2016

The present paper examines the influence of the tribofinishing process on the surface state of steel parts XC48, while taking into account the variation in hardness and mass. The tribofinishing process is a mechanical-chemical process, which comprises the use of low frequency impact vibration in the presence of abrasive and chemical additives [1]. The treatment regime (frequency and amplitude) has a great influence on geometrical, mechanical and metallographic treated surfaces. The improvement of the surface quality is determined as a function of the treatment time from 30 to 240 minutes. The tribofinishing process has many technical and economic advantages for the treatment of mechanical parts of simple and complex shapes, which have a better surface finish and improved life of parts etc.
Formation and Characterization of Hard Coatings on Ductile Iron Grade 100-70-03
Authors: López-Perrusquia N. , Doñu Ruiz M.A. , Sánchez Huerta D. , Noriega-Zenteno J. , Cortés-Suarez J.V.
Published: June 2016

This paper studies the formation of iron boride on the surface in ductile iron 100-70-03 class exposed to a thermochemical treatment boron dehydrated paste. The formation of iron boride layers Fe2B/FeB-type were obtained at temperatures of 1173 K, 1223 K and 1273 K, with exposure times of 8 hours of treatment. The study consisted in evaluating the growth kinetics of the boride layer on the surface of ductile iron boriding. Also the boride layers were determined by the XRD method, EDS. Also evaluated fracture toughness technique Vickers microindentation 15 and 30 microns from the surface with different loadings of iron boride microindentation formed on the surface.
Fatigue Crack Growth in Specimens with Rectangular Section under Torsion and Bending with Torsion
Authors: Faszynka Sebastian , Rozumek Dariusz
Published: June 2016

The paper presents the test results on the fatigue crack growth under torsion and proportional bending with torsion in the aluminium alloy EN AW-2017A-T4. The tests were performed at the fatigue test stand MZGS-100 at the constant amplitude of moment MB = MT = MBT = 15.84 N⋅m and stress ratio R = -1. Plane specimens with stress concentrators in form of the external one-sided blunt notch were tested. The results of experiments were described on graphs of the fatigue crack length „a” versus numbers of cycles N. A non-uniform fatigue cracks growth on both lateral surfaces of specimens was observed during experimental tests.
Energy Based Approach Calculations of Machine Components Fatigue Life
Authors: Ligaj Bogdan , Szala Grzegorz
Published: June 2016

The purpose of this paper is to present a method for fatigue life calculations in energy based approach (hybrid method) and its experimental verification. Tests were performed for C45 steel. It was found, on the basis of experimental tests, that the diagram of fatigue life in energy approach is characterized by higher value of determination coefficient R2 than the diagram of fatigue life in stress based approach (both for constant amplitude and programmable loading). A comparative analysis of calculation results and experimental tests results revealed that for two-step loading the relative difference in results depends on the maximal value of stresses in the spectrum.
Accelerated Determination of the Fatigue Limit and the S-N Curve by Means of the Thermographic Method for C45 Steel
Authors: Lipski Adam
Published: June 2016

The paper presents a new thermographic method that enables simultaneous accelerated determination of the fatigue limit and the S-N curve. In the presented method, the fatigue limit was determined assuming a constant rate of temperature rise occurring in the second phase of a specimen fatigue life. The S-N curve was developed based on energy-related parameter with the assumption of its dependency on the stress amplitude. The tests made on C45 steel under reversed bending revealed that the fatigue limit value obtained from accelerated thermographic tests as compared to the value obtained using Staircase method differs by 10.0% maximum.The S-N curve obtained by accelerated thermographic method fits inside 95% confidence interval for the S-N curve obtained from the full test.
Experimental and Numerical Modeling of the Phenomenon of Delamination Cracking in S235 Steel
Authors: Pala Robert , Galkiewicz Jarosław , Dzioba Ihor
Published: June 2016

In the paper was compared the stress state in front of the crack for SEN(B) specimens of S235RJ steel without and with delamination cracks. Stress distribution and characteristics of stress state triaxiality were calculated for both type of specimens. It was showed a reduction in the stress fields and triaxiality parameters in front of the main crack in the presence of delamination cracking.
Stress Intensity Factor Calculation by Smoothed Finite Element Method
Authors: Rokach Ihor
Published: June 2016

Accuracy of stress intensity factor (SIF) determination by three types of smooth finite element method (namely, ES-FEM, NS-FEM and α-FEM) has been investigated. Two types of simple benchmark problems (uniaxial tension of the specimens with central and edge cracks) have been considered. SIF values were calculated by virtual crack extension and modified crack closure integral methods on almost uniform meshes. It has been shown that utilizing of ES-FEM and α-FEM significantly improves accuracy of the results compared with the traditional FEM.
Evaluation of Fatigue Failure of S960QL Steel in the Conditions of Plastic Strain
Authors: Slezak Tomasz , Sniezek Lucjan , Torzewski Janusz , Hutsaylyuk Volodymyr
Published: June 2016

The article presents the results of research on low cycle fatigue strength of high-strength structural steel S960QL. During the tests, controlled force was applied using the different total strain amplitude εac and strain ratio Rε = 0.1. The obtained results allowed to determine the value of the cyclic strain hardening exponent n' and the cyclic strength coefficient K' and to draw the cyclic stress-strain curve. Analysis was also carried out of fatigue life based on the Manson-Coffin-Basquin equation. Fatigue values were also determined. Fractographic tests of fatigue fractures allowed to identify the causes of crack initiation and the course of their propagation.
Verification of the Charpy Impact Test Capability to Determine the Constants of the Johnson-Cook Model
Authors: Stopel Michal Stopel , Skibicki Dariusz
Published: June 2016

Feasibility analysis of replacing split Hopkinson bars test by Charpy impact test for determination of Johnson-Cook’s material model parameters. The results show that the Charpy impact test may, due to the strain rates achieved, successfully replace the mentioned experimental test. Moreover the results shows that some further studies should be conducted to improve efficiency of the proposed method.
Verification of FEM Modelling Capabilities Allowing for the Effects of Strain Rate
Authors: Stopel Michal Stopel , Skibicki Dariusz , Mocko Wojciech
Published: June 2016

The effects of strain rate on the changes in material properties are commonly known [2,5]. This phenomena is also the subject of studies related to composite materials due to fact that composites are widely used as an energy absorbers in road safety structures [6]. Those effects are more often considered as required to be included in the design of structures subject to dynamic loads [1,3]. The example structure is the road infrastructure subject to high strain due to the vehicle impact characterized by a high strain rate [1].Various numerical methods are being employed at the design stage to reduce the costs of experiments on actual structures. One of the most important factors in preparation of the analysis is to select a suitable material model to allow for the effects of strain rate on the changes in material properties. One of the material models allowing for the effects of strain rate is the model developed by G.R. Johnson and W.H. Cook.The study aims to verify the FEM modelling capabilities of the effects characterized by the effects of high strain rate on the material properties. Thus, the strength tests required to determine the material constants for Johnson-Cook model were performed and modelled using FEM method and the results including the effects of strain rate on the mechanical properties were compared.
The Influence of the Grade of Materials and their State on the Thermo-Mechanical Behaviour of the Chosen Power Plant Components
Authors: Twardawa Mariusz , Okrajni Jerzy
Published: June 2016

The paper discusses the issue of the influence of the growth of the operation parameters of power plant components on the fatigue phenomena that take place under mechanical and thermal loading. The loading characteristics have been taken as measurements results in industrial conditions. Stress-strain characteristics of such components, which take into consideration the changeable properties of materials subject to fatigue, have been described. The hardening processes of the materials, which are assumed to be used in designed power plants, have also been discussed. The aim of the paper is the description of the mechanical behaviour of the power plant components taking into consideration the real industrial conditions of their operation and changeable mechanical properties of the components’ materials.