bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling and strength analysis of the prototype of the multi-tasking car trailer
Authors: Posiadała Bogdan , Ladra Piotr
Published: March 2018

The subject of the paper is modeling and strength analysis of the prototype of the multi-tasking car trailer. The innovativeness of the solutions applied consists in the combination of several single-purpose trailers into one, allowing for multitasking and the combination of several specialized trailers. Using the author's solution, the prototype of a multi-purpose trailer has been developed, which has the characteristics of several specialized trailers, such as for the transportation of general cargo, kayaks, motorcycles, quads etc. The model has been created by using SolidWorks package and it has been used for full strength analysis by simulation module. The sample analysis results cover various load configurations with respect to selected trailer construction components.
Monitoring the fatigue crack on the test specimen during the cyclic loading
Authors: Sapieta Milan , Šulka Peter , Svoboda Martin
Published: March 2018

The main purpose of this paper is monitoring propagation of plastic area of fatigue crack. There were made notch on specimens and they were cyclically loaded with three-point bending. The record was evaluated after a certain number of loading cycles. The loading force is still constant throughout the measurement time for all specimens. The whole process was recorded using an infrared camera.
Shifted axis angular positioning mechanisms – unconventional use of exact constraint design
Authors: Szykiedans Ksawery , Bujwan Maciej
Published: March 2018

Paper presents some remarks about designing angular positioners having significant angular displacement and shifted axis of rotation. Those driving mechanism are useful in specific applications where mechanism wraps around other object or there is a need of rotation around virtual axis. Examples of those applications like orthotic robots or gimbals for panoramic motions where developed at Faculty of Mechatronics WUT. Usage of exact constraint method was described including its influence to a kinematic structure of designed mechanism.
Investigation of the effects of the equivalent circuit parameters on induction motor torque using three different equivalent circuit models
Authors: Tezcan Mehmet Murat , Yetgin Asim Gökhan , Canakoglu Ali Ihsan , Cevher Bariş , Turan Mustafa , Ayaz Murat
Published: March 2018

In this study, the most vital characteristic properties of induction motor, motor starting, maximum and nominal torque are analyzed for what are affected. For the analysis of torque, L type, T type and IEEE 112 equivalent circuit model is employed. Torque change is investigated with the help of codes developed in MATLAB to be used in electrical machines course. First, the slip-moment characteristic curve of the induction motor is divided into three working zones and it was determined which equivalent circuit model gave the best results in these study zones. Later, such parameters as stator and rotor resistance, stator and rotor reactance, magnetization reactance, core resistance and slip are researched for how torque values are affected from. The obtained values for each of the three equivalent circuit models are given and compared with experimental results. 50 HP squirrel cage induction motor parameters are used in analysis. In the analysis, the most influential parameters on the starting torque are found as rotor resistance and stator and rotor reactance. Change of other parameters’ impact ratio depending upon right proportion and inverse proportion is observed. When nominal torque variations are investigated, again rotor resistance is the most influential parameter and by selecting proper factor effecting rotor resistance during design, the result of acquiring desired rotor resistance is obtained. When the maximum torque variations are examined, it appears that the stator and rotor reactance values are effective. Starting, maximum and nominal torque expressions change with square of voltage alters the effect on them a lot. Therefore, triangle or star connection importance arises during machine design.
Cooperation of axisymmetric connection elements under dynamic load
Authors: Kołodziej Andrzej , Dudziak Marian , Talaśka Krzysztof
Published: March 2018

The article presents a method for determining the parameters that define the cooperation of the elements in the axisymmetic connection. The connection, which constitutes a shaft cooperating with a sleeve, has been tested for reaction forces in the connection during shaft rotation in the static sleeve. The shaft was characterized by deliberately modelled roundness deviations in the form of ovality, triangularity and quadrangularity. In addition, the research programme has taken into account the determination of the impact of tolerance of the outside diameter of the shaft. Determination of reaction forces has been carried out using the FEM software. The shaft has been modelled as a rigid element that rotates with a given rotational speed in the deformable sleeve. The conclusions present the impact of roundness deviation types and the tolerance value on reaction forces in the connection restraint. The method presented in the article can be used to predict the behaviour of the elements of axisymmetic connections under dynamic load, which can contribute to forecasting the durability of the connection.
Fatigue life prediction of mechanical structures under stochastic loading
Authors: Leitner Bohuš , Figuli Lucia
Published: March 2018

Problems of fatigue life prediction of materials and structures are discussed in the paper. Service loading is assumed as a continuous loading process with possible discontinuous events, which are caused by various operating conditions. The damage in a material is due to a cumulative degradation process. The damaging process is then represented either by rain-flow matrices or by a fatigue damage function which is derived using some hypothesis of a fatigue failure criterion. Presented theoretical procedure enables a very effective estimation of a service life and/or reliable evaluation of residual life of any structures under various types of loading and environmental conditions. This approach creates a good basis for powerful expert systems in structural and mechanical engineering. The aim of the paper is to present briefly some results of analysis of load-bearing steel structure loads of special railway crane PKP 25/20i which was utilized in some specific ad relatively hard operating conditions. Virtual models of the structure were being used in an analysis of acting working dynamics loads influence to be able to forecast fatigue life of load-bearing of the crane jib.
Prediction of modal properties of circular disc with pre-stressed fields
Authors: Naď Milan , Ďuriš Rastislav , Nánási Tibor
Published: March 2018

Many structural elements in technical devices, as well as some tools in manufacturing equipment, such as saw blade or, have a geometric shape similar to a circular disc. In many cases, these circular discs must meet the required dynamic properties. One of the techniques to achieve the required dynamic properties of circular disc is based on initiating pre-stressed fields in the disc plane. In-plane residual stresses are created by appropriate technological treatments in selected disc part, for example by rolling of annulus leading to plastic deformation which causes the change of volume distribution in this disc part. The effects of in-plane residual stresses on modal properties of circular disc are analysed. The natural frequencies modifications depending on position and width and also on the change in thickness of the roll-prestressed annulus are investigated in this paper.
Analysis of stress and deformation fields of shape complex beams
Authors: Pástor Miroslav , Lengvarský Pavol
Published: March 2018

In this paper is investigated the analysis of stress and deformation fields of shape complex beams. The shape complex beams are made from load-bearing sheet (trapezoidal sheet) circumferentially connected with strips of sheet metal, these beams are a substitute for more complex and heavier beams. The numerical analysis with static load are performed for these beams. The effect of three different types of connections between load-bearing sheet and strips of sheet metal is investigated. The first type of connection is represented by the trapezoidal sheet perfectly welded to the strips of sheet metal, the second type of connection is represented by the trapezoidal sheet welded to the strips of sheet metal only on the base sides of the trapezoidal sheet. The third one is represented by point welds. The stress and deformation fields for all types of the connections are compared and the suitable variant is chosen.
Missing values reconstruction in sound level monitoring station by means of intelligent computing
Authors: Radziszewski Leszek , Kekez Michał , Sapietová Alžbeta
Published: March 2018

The aim of the paper was to reconstruct the missing data by applying the model which describes variability of sound level in the whole period from 2013 to 2016. To build the model, the computational intelligence methods, like fuzzy systems, or regression trees can be used. The latter approach was applied and we built the model with Cubist regression tree software, using equivalent sound levels recorded in 2013. For the reconstruction of sound level data in short period of time (several days), time series values and day_of_week values together should be used in the training dataset. For the reconstruction of sound level data in long period of time (several months) day_of_week values should be used in the training dataset.
Forced convection and heat transfer around a bounded cylinder
Authors: Skočilasová Blanka , Skočilas Jan , Soukup Josef
Published: March 2018

The article deals with the heat transfer solution in the fluid flow inside a pipe, the small tube is inserted into the pipe and its axis is perpendicular to the axis of the pipe. The fluid is water, the regime of the fluid flow is turbulent. The small tube is loaded by the internal source of the heat, the power of the source is constant and homogenous over the small tube surface and the cold water cools down the small tube. The analysis of the described problem helps to design the experimental model (the heat source above all) to validate the CFD results. The work included the numeric and analytic method. The model was prepared with the aim to investigate large amount of the variants of the geometric set up (the tube and pipe diameters ratio, the geometrical aspect ratio, corresponding stabilization length of the pipe for given diameter), the flow properties (variation of the velocity values, Reynolds number) and the power of the heat source (ensuring the measurable differences of the temperatures on the tube surface, large Nusselt number). The effect of the constrained space has been observed and described, compare to the free fluid flow.
Identifying the cause of cutting tool failure by using simulation software
Authors: Zrak Andrej , Koňár Radoslav
Published: March 2018

The article is focused on the construction problems of cutting tools designed for manufacturing components in high numbers. Analysis of the tool with low lifetime is provided with the use of simulation software to detect the causes of the tool failure. Parameters of the simulation are close to the real conditions of the tool in production. The results from the simulation indicate that the bending moment occurs in the tool because of forces which have opposite direction on different areas. On these basis technological adjustments are made. These adjustments are also analysed by using simulation software.
Simulation of sound transmission through the porous material, determining the parameters of acoustic absorption and sound reduction
Authors: Zvolenský Peter , Grenčík Juraj , Kašiar Ľubomír , Stuchlý Vladimír
Published: March 2018

Currently, the quality of structural design of a railway coach is evaluated by so called acoustic comfort, which is characterized by achieved levels of internal noise. Therefore, acoustic parameters of car body are being developed purposely. The paper presents the results of the computer simulation of noise transmission through the wagon walls and the use of noise tests from the train running. The acoustic properties of the original and new materials in the care body are compared.
Assessment of a rail vehicle running with the damaged wheel on a ride comfort for passengers
Authors: Dižo Ján , Blatnický Miroslav , Steišūnas Stasys , Skočilasová Blanka
Published: March 2018

In certain conditions rail vehicles wheels can be during operation damaged. Then, the profile of wheels is no longer circular, but it is changed depending on the type and severity of defects. When such rail vehicle with the damaged wheel operates, the quality of a ride comfort for passenger is degraded. This article is focused on the assessment of ride comfort for passenger based on results obtained from dynamic analyses. Simulations and calculations were carried out in commercial multibody software. In our research we considered one type of the railway wheel untrueness – wheel-flat. This type of wheel damaging is relatively common and has such influence on the ride comfort for passenger worsening, which needs to be detected and investigated.
Comparation of the impact of selected technical gases on properties of a pneumatic flexible coupling
Authors: Grega Robert , Krajňák Jozef , Harachová Daniela
Published: March 2018

An important part of the oscillating mechanical drives are flexible shaft couplings. The special use of the pneumatic flexible coupling is possibility to serve as mechanical drives tuners. Being examined in tuners mechanical drives there is also a research focus on the impact of industrial gases on the change of dynamic characteristics of pneumatic couplings. The paper investigates five different industrial gases, namely: air, helium (He-4.6), a mixture of propane and butane gas (C3H8+C4H10), argon (Ar) and nitrogen (N2) to see how these gases affect the dynamic characteristics of pneumatic flexible shaft coupling with marking 4-2/70 T-C.
Wear research of railway wheelset profile by using computer simulation
Authors: Smetanka Lukáš , Št’astniak Pavol , Harušinec Jozef
Published: March 2018

The wear of rails and wheels is important problem in rail traffic. The change of the shape of the wheel profile has not only a great influence on the dynamic properties of the vehicle (like stability, safety by passing curved tracks, etc.), but also affects the ride comfort of passengers and environmental insults, in extreme cases it can cause rail derailment. One of the ways to predict these undesired conditions are computer aided simulation analyzes. In this article are presented assessments of wheel profile wear by Archard wear law in Simpack simulation software, when is railway vehicle driving at different velocities.
Kinematic and dynamic analysis and distribution of stress for six-item mechanism
Authors: Vavro Ján , Vavro Ján , Kováčiková Petra , Híreš Jakub
Published: March 2018

This paper presents a kinematic and dynamic analysis and distribution of the stress for six-item planar mechanism by means of the SolidWorks software. Graphic dependence of kinematic and dynamic magnitudes of some points is given in dependence on the angle of rotation of the driving item and in dependence on the time. Distribution of the stress in the items is presented in [Pa]. In relation to the kinematic and dynamic analysis and subsequent simulation of the planar as well as spatial mechanisms, it is great solution to use SolidWorks software program. The considerable advantage of this mentioned program is based on its simplicity from the aspect of modeling and moreover, it is important to point out that utilisation of the mentioned program leads to results which are precise and accurate in the case of the numerical solution of the equations in the whole magnitude referring to motion of mechanism while the given results are obtained in the graphic form.
Use of risk assessment methods in maintenance for more reliable rolling stock operation
Authors: Grenčík Juraj , Poprocký Roman , Galliková Jana , Volna Peter
Published: March 2018

Operation of the rolling stock is associated with a number of risks. The consequences of failures are sometimes very serious - safety or the environment, sometimes only economic. A significant factor affecting the safe operation of railway vehicles is maintenance. The paper presents methods of risks assessment and possibilities of their reduction in design, operation and maintenance of railway vehicles. Special attention is given to the new "silent brakes" and safety related issues for freight wagons.
A new accelerated technique for validation of cyclic plasticity models
Authors: Halama Radim , Gál Petr , Paška Zbyněk , Sedlák Josef
Published: March 2018

This contribution presents a new methodology of fatigue tests evaluation based on digital image correlation application. The full-field strain analysis brings the possibility of 3D strain measurement evaluation on a curved part of specimen standardly used under axial-torsional loading. Resulting strain response curves can subsequently serve for evaluation of cyclic plasticity model predictions. The crucial idea is the way of FE model creation to can evaluate simulation in the same points of the structure as in the DIC measurement. The new methodology saves amount of material and leads to a shorter experimental time.
Tensile and bending test of carbon/epoxy and carbon/geopolymer composites after temperature conditioning
Authors: Krystek Jan , Laš Vladislav , Pompe Vilém , Hájková Pavlína
Published: March 2018

Composites with epoxy matrix cannot be used in high temperature, while geopolymer matrix excel in high temperature resistance. First, prismatic specimens were subjected to conditioning temperature. Second, the tensile and bending test were performed at room temperature. This paper present comparison of mechanical properties of carbon/epoxy and carbon/geopolymer composites. Numerical simulations of tensile and bendidng tests were performed in finite element system Abaqus.
Development of methods for performing the maximum voluntary contraction (MVC) test
Authors: Kukla Mateusz , Wieczorek Bartosz , Warguła Łukasz
Published: March 2018

The aim of the study is to determine the most effective isometric exercises required in order to perform MVC (Maximum Voluntary Contraction) tests under given static muscle contraction conditions. To this end, a group of four muscles was defined and on this basis, a series of exercises was selected. During electromyography studies, the electrical activity of the muscles was recorded. The article presents the results obtained for all exercises in the whole group of subjects. The data obtained provide a basis for evaluating and selecting the method of loading the analysed muscles during MVC tests. This is necessary in order to perform a normalization of raw (unprocessed) EMG signal, thus enabling comparison of results between individual subjects. Analyses concerning this kind of diagnosis of the electrical activity of muscles are widely applied in research related to rehabilitation and medicine, sports science, but also ergonomics.
Utility of an unitary-shredding method to evaluate the conditions and selection of constructional features during grinding
Authors: Macko Marek , Tyszczuk Krzysztof , Śmigielski Grzegorz , Mroziński Adam
Published: March 2018

In order to evaluate and improve the efficiency of the process of grinding, various investigations are conducted, based on the relevant research methodology. One of them is the method in which the crushed sample is subjected to single stroke loads. On this basis, the influence of the geometric features of the chipper system and the dynamic process on the efficiency of the grinding is determined. Charpy hammers instrument were used to perform these modifications so that the momentary force of the resistance could be recorded with varying sample alignment, blade geometry changes and others. In addition, it was proposed to use a super fast camera (up to 1200 fps) to record the deformation of the sample and its destruction, in order to interpretation the burdens there. Under such idealized conditions, a range of variables has been identified that significantly affect the reduction of energy demand during grinding.
Vibration of the steel frame of the primary sand classifier
Authors: Soukup Josef , Skočilasová Blanka , Skočilas Jan
Published: March 2018

Article deals with the presentation of measurement that have been carried out on the steel frame of the primary sand classifier. The aim of the investigation was to identify the sources of the abnormal vibration of the frame. The vibration significantly reduces the effective performance of the classifier. The frame anchorage has been stripped out from concrete footing by these vibrations. The measurement of dynamic properties of the frame were performed. The displacements of the particular trusses have been experimentally investigated by accelerometers. The tensile test were performed in the places of expected maximum amplitude of the vibration. Based on the experiment results and new design calculation of the steel frame (truss construction), the new construction design was developed and improved by frame reinforcing. The new designed construction was investigated by vibration measurements again. The acceleration and total amplitude of particular trusses were recorded. The steel construction of the supporting frame has frequencies in range from 13.07 to 13.10 Hz. The significant enhancement of the noise and vibration of the main bearing have been observed during the classifier operation. The system of precautions was proposed to improve operation of the classifier and after realization the classifier run with no limitation.
Fatigue limit estimation using IR camera
Authors: Stankovičová Zuzana , Dekýš Vladimír , Uhríčik Milan , Novák Pavol , Strnadel Bohumír
Published: March 2018

Determination of fatigue limit by traditional method is associated with testing of large number of specimens. This is caused by more scatter in test results and therefore a higher amount of tests are needed to generate a statistically reliable trend. The paper presents rapid and reliable estimation of fatigue limit using infrared thermography. By analysing the temperature of the material surface during cyclic loading it is possible to evaluate the dynamic behaviour of a structure and determine the fatigue limit. The method provides reliable results using a very little number of specimens in a very short time compared with traditional method.
The experimental measurement of the tyre casing defects for the freight vehicles at the dynamic loading
Authors: Vavro Ján , Vavro Ján , Kováčiková Petra , Híreš Jakub
Published: March 2018

The paper deals with the experimental measurement of the tyre casing defects for the freight vehicles at the dynamic loading. The given investigation was mainly focused on cracks and defects in tyre casing, which is commonly used for freight vehicles. The mentioned measurement or investigation was performed under the strictly specified conditions. The given measurement of crack propagation in car tyre casing was based on changes of speed, changes of loading as well as changes of service time interval. It is important to point out that the pressure in the tyre was predetermined to be the constant value. The experimental procedures were carried out by help of special drum testing machine with designation: IGTT 25 kN – C and with the 1707 mm drum diameter. The mentioned measurement was performed for the area of tyre casing shoulder and it was in the site between the first and the second buffer lining. Using the ITT-1 program relating to non-destructive testing analyser, the CCD camera for testing procedure of tyre casing was used for the camera images which were taken from the internal side of the tyre casing.
Measurement system for special surface mapping using miniature displacement sensors
Authors: Zowade Martyna , Bodnicki Maciej
Published: March 2018

The aim of the work was to design a special system for measurements of elements with repetitive geometry or assemblies with repeating components, set in a linear patterns. The main focus was based on developing a computer program for signal analysis from variable number of miniature displacement sensors. It was set that the response for displacement of measuring tip from each sensor was a 0-5 V voltage signal with possibility of using different type of sensors. Requirements were determined based on projected measurement method. A special design of sensor was made for testing the computer program. If the characteristics of the sensor is known, it is possible to compute the type A evaluation of uncertainty. The results are presented in XY chart on computer screen. The program allows the user to choose any number of the sensors and determine the distance between them. Also, the possibility of calibration of sensors’ set was provided. The test were conducted on a prototype handle for sensors, made on a 3D printer.
An alternative J2 material model with isotropic hardening for coupled thermal-structural finite-strain elastoplastic analyses
Authors: Écsi Ladislav , Élesztos Pavel , Jančo Roland
Published: March 2018

In this paper an alternative J2 material model with isotropic hardening for finite-strain elastoplastic analyses is presented. The model is based on a new nonlinear continuum mechanical theory of finite deformations of elastoplastic media which allows us to describe the plastic flow in terms of various instances of the yield surface and corresponding stress measures in the initial and current configurations of the body. The approach also allows us to develop thermodynamically consistent material models in every respect. Consequently, the models not only do comply with the principles of material modelling, but also use constitutive equations, evolution equations and even ‘normality rules’ during return mapping which can be expressed in terms of power conjugate stress and strain measures or their objective rates. Therefore, such models and the results of the analyses employing them no longer depend on the description and the particularities of the material model formulation. Here we briefly present an improved version of our former material model capable of modelling ductile-to brittle failure mode transition and demonstrate the model in a numerical example using a fully coupled thermal-structural analysis.
The fractography analysis of IN718 alloy after three-point flexure fatigue test
Authors: Belan Juraj , Vaško Alan , Kuchariková Lenka , Tillová Eva
Published: March 2018

In this study, the high cycle fatigue (HCF) properties of IN718 superalloy with given chemical composition were investigated at three-point flexure fatigue test at room temperature. INCONEL alloy 718 is nickel-chromium-iron hardenable alloy and due to its unique combination of mechanical properties (high-strength; corrosion-resistant and so on) used for production of heat resistant parts of aero jet engine mostly. Mechanical properties of this alloy are strongly dependent on microstructure and on presence of structural features such are principal strengthening phase gamma double prime, gamma prime and due to its morphology less desired delta phases. The mentioned phases precipitate at various temperature ranges and Nb content as well. The three-point flexure fatigue test was performed on ZWICK/ROELL Amsler 150 HFP 5100 test equipment with approximate loading frequency f=150 Hz. The S – N (Stress – Number of cycles) curve was obtained after testing. With the help of scanning electron microscope (SEM), fractography analyses were performed to disclose the fracture features of specimens in different life ranges. The brief comparison of three-point flexure and push-pull fatigue loading modes and its influence on fatigue life is discussed as well.
Porosity formation and fatigue properties of AlSiCu cast alloy
Authors: Kuchariková Lenka , Tillová Eva , Uhríčik Milan , Belan Juraj
Published: March 2018

The need for aluminium alloys having a good toughness, high strength, adequate damage tolerance capability, good fatigue resistance and good corrosion resistance for use in the industries applications of aerospace, automotive and even commercial products led to study of the properties and structure of the AlSi9Cu3 cast alloy. The most important metallurgical parameters affecting the aluminium alloy’s resistance to fatigue load are the amount, types and size of casting defects. Therefore quantitative analysis was used for determination of casting defects size by optical microscopy on metallographic sections and an analysis of the size distribution by extreme value statistics. The software NIS Elements was used for quantitative analysis of casting defects and results show that porosity have a great influence on to the fatigue properties of AlSi9Cu3 cast alloy.
Optical attributes influence on mechanical properties of laser cutted PMMA
Authors: Meško Jozef , Nigrovič Rastislav
Published: March 2018

The article describes and characterizes the technology and principle of laser cutting PMMA material. Experimental samples with thickness t = 3 mm of PMMA were made with a constant optimized technological parameters of laser cutting. In the experimental part are compared values of hardness of cutted surface, tensile strength of different colour variations and impact on selected mechanical properties by change of technological procedures of selected material processing - tempering of plastics.
Study of the fatigue behaviour of synthetic nodular cast irons at low and high frequency cyclic loading
Authors: Vaško Alan , Belan Juraj , Tillová Eva
Published: March 2018

The paper presents the results of low and high frequency fatigue tests carried out on nodular cast iron. The specimens of synthetic nodular cast irons from three different melts were studied in the high cycle fatigue region (from 105 to 108 cycles) using fatigue experimental equipments for low and high frequency cyclic loading. Low frequency fatigue tests were carried out at frequency f ≈ 120 Hz using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100. High frequency fatigue tests were carried out at frequency f ≈ 20 kHz using the ultrasonic fatigue testing device KAUP-ZU. Both of them were carried out at sinusoidal cyclic push-pull loading (stress ratio R = -1) at ambient temperature (T ≈ 20 °C). The relationship σa = f (N) and fatigue strengths were determined experimentally; mechanical properties, microstructures and fracture surfaces were investigated.
Experimental research on biomass cutting process
Authors: Wilczyński Dominik , Talaśka Krzysztof , Malujda Ireneusz , Jankowiak Piotr
Published: March 2018

This paper contains the results of the biomass cutting process in which wheat straw was used. Tests were made on the prototype test stand which made it possible to control the parameters of the cutting process and based on that define its energy consumption. During the research the following parameters were measured: rotational speed of electric motor, which drives the rotor with a set of cutting knives, electric current supply and torque on the shaft. Tests were made for the variable moisture content of the biomass and with knives with three different back-rake angles 5°, 15° and 30°. Using these measured parameters it was possible to calculate the power and the cutting force necessary to disintegrate biomass. The main goal was to find out if there is any influence of moisture content and the back-rake angle of the cutting knife on the dynamic parameters of the process - power and cutting force. The presented results can be very useful in a design process for a working assembly of biomass disintegrating machines which are directed to the energetic efficiency.
Euler-Lagrange optimization of electric drives with DTM method
Authors: Oršanský Pavol , Ftorek Branislav , Šamajová Helena , Vittek Ján
Published: March 2018

Euler-Lagrange optimization method is exploited here to develop energy saving position control strategy valid for a.c. drives. The optimization principle respects copper losses minimization only. Boundary value problem for Euler-Lagrange equations is solved by Differential transformation method (DTM).
Numerical modeling of the contact between three-dimensional regions with the use of FEM
Authors: Skrzypczak Tomasz , Węgrzyn-Skrzypczak Ewa , Sowa Leszek
Published: March 2018

The numerical approach based on the finite element method (FEM) for modeling of mechanical interaction between three-dimensional objects is presented in the paper. The model of contact is based on the assumption that the nodes of the region which is the source of contact cannot overlap with the nodes of the region being the target. The procedure of the detection of collision between surfaces of the source and the target is discussed in details. The behaviour of surfaces being in contact depends on their rigidity and is numerically modeled in the case of perfectly rigid source and deformable target. Each modeled object has an independent mesh of finite elements. These meshes can be freely moved relative to each other. Example of calculation using original program written in C++ is presented and discussed.
Focus Section Health IT Usability: Applying a Task-Technology Fit Model to Adapt an Electronic Patient Portal for Patient Work
Authors: Ali Sana , Romero Juana , Morrison Kevin , Hafeez Baria , Ancker Jessica
Published: March 2018

Objectives Although electronic patient portals are offered by most health care organizations, poor usability and poor fit to patient needs may pose barriers to adoption. We collaborated with an academic hospital to conduct iterative user evaluation of a newly deployed portal designed to deliver inpatient data upon hospital discharge.

Methods Three evaluators applied heuristic usability evaluation and conducted 23 individual user testing sessions with patients with chronic disease or managing the care of family members with chronic disease. Evaluation and development/improvement were conducted iteratively. User testing and analysis of qualitative data were both conducted from the perspective of a task-technology fit framework, to assess the degree of fit between the portal and patient work.

Results Ability to complete health information management tasks, perceived usability, and positive comments from users improved over the course of the iterative development. However, patients still encountered significant difficulties accomplishing certain tasks such as setting up proxy accounts. The problems were most severe when patients did not start with a clear understanding of tasks that they could accomplish. In exploring the portal, novice users frequently described anecdotes from their own medical history or constructed fictional narratives about a hypothetical patient.

Conclusion Chronic illness imposes a significant workload on patients, and applying a task-technology framework for evaluation of a patient portal helped improve the portal's fit to patient needs. However, it also revealed that patients often lack a clear understanding of tasks that would help them accomplish personal health information management. Portal developers may need to educate patients about types of patient work involving medical centers, in a way that developers of clinical information systems do not need to do. An approach to doing this might be to provide narratives about hypothetical patients.
Validation and Refinement of a Pain Information Model from EHR Flowsheet Data
Authors: Westra Bonnie , Johnson Steven , Ali Samira , Bavuso Karen , Cruz Christopher , Collins Sarah , Furukawa Meg , Hook Mary , LaFlamme Anne , Lytle Kay , Pruinelli Lisiane , Rajchel Tari , Settergren Theresa , Westman Kathryn , Whittenburg Luann
Published: March 2018

Background Secondary use of electronic health record (EHR) data can reduce costs of research and quality reporting. However, EHR data must be consistent within and across organizations. Flowsheet data provide a rich source of interprofessional data and represents a high volume of documentation; however, content is not standardized. Health care organizations design and implement customized content for different care areas creating duplicative data that is noncomparable. In a prior study, 10 information models (IMs) were derived from an EHR that included 2.4 million patients. There was a need to evaluate the generalizability of the models across organizations. The pain IM was selected for evaluation and refinement because pain is a commonly occurring problem associated with high costs for pain management.

Objective The purpose of our study was to validate and further refine a pain IM from EHR flowsheet data that standardizes pain concepts, definitions, and associated value sets for assessments, goals, interventions, and outcomes.

Methods A retrospective observational study was conducted using an iterative consensus-based approach to map, analyze, and evaluate data from 10 organizations.

Results The aggregated metadata from the EHRs of 8 large health care organizations and the design build in 2 additional organizations represented flowsheet data from 6.6 million patients, 27 million encounters, and 683 million observations. The final pain IM has 30 concepts, 4 panels (classes), and 396 value set items. Results are built on Logical Observation Identifiers Names and Codes (LOINC) pain assessment terms and extend the need for additional terms to support interoperability.

Conclusion The resulting pain IM is a consensus model based on actual EHR documentation in the participating health systems. The IM captures the most important concepts related to pain.
Klassenklima, schulisches Wohlbefinden und Gesundheit von Schülerinnen und Schülern in Deutschland: Ergebnisse des Nationalen Bildungspanels (NEPS)
Authors: Rathmann Katharina , Herke Max , Hurrelmann Klaus , Richter Matthias
Published: March 2018

Ziel Ziel des Beitrags ist es, erstmalig mit den Daten des Nationalen Bildungspanels den Zusammenhang zwischen Merkmalen des Klassenklimas und des schulischen Wohlbefindens mit der selbstberichteten Gesundheit und krankheitsbedingten Schulfehltagen von Schülern in deutschen Regelschulen zu untersuchen.

Methodik Datenbasis bildet das Nationale Bildungspanel (NEPS). Die Stichprobe umfasst (n=7348) Schüler der siebten Klassen in Regelschulen (Startkohorte 3, Welle 3, 2012). Merkmale des Klassenklimas umfassen Anforderungen, Kontrolle und Lernorientierung im Unterricht, Autonomie und Interaktion der Schüler sowie die Unterrichtsqualität, jeweils auf die Lehrkräfte in Deutsch bezogen. Das schulische Wohlbefinden wird über die Schulzufriedenheit sowie Hilflosigkeit in zentralen Schulfächern erfasst. Es werden sowohl bivariate Analysen als auch logistische Mehrebenenmodelle, unter Kontrolle von Alter, Geschlecht und besuchter Schulform, durchgeführt.

Ergebnisse Die Ergebnisse der Mehrebenenmodelle zeigen, dass insbesondere Schüler mit einer höheren Schulzufriedenheit eine bessere Gesundheit und weniger krankheitsbedingte Fehltage berichten. Eine höhere Hilflosigkeit und Lernorientierung sind dagegen negativ mit beiden Zielgrößen assoziiert. Hauptschüler besitzen zudem ein erhöhtes Risiko krankheitsbedingter Fehltage im Vergleich zu Gymnasiasten.

Schlussfolgerung Die Ergebnisse unterstreichen, dass insbesondere das schulische Wohlbefinden in Form der Schulzufriedenheit sowie der Hilflosigkeit in zentralen Schulfächern eng mit der subjektiven Gesundheit und krankheitsbedingten Fehltagen assoziiert ist. Maßnahmen zur Gesundheitsförderung sollten daher v. a. auf das schulische Wohlbefinden gerichtet werden sowie Schüler adressieren, die eine andere Schulform als das Gymnasium besuchen.
Akute Lungenembolie – Update 2018
Authors: Lankeit Mareike , Hobohm Lukas , Konstantinides Stavros
Published: March 2018

Die akute Lungenembolie ist die dritthäufigste akute kardiovaskuläre Erkrankung und geht mit einer durchschnittlichen Letalitätsrate von bis zu 10% innerhalb der ersten 3 Monate einher. Themen dieses Übersichtsartikels sind insbesondere die risikoadaptierte Diagnostik und Therapie der akuten Lungenembolie.
Radio-frequency characteristic variation of interdigital capacitor having multilayer graphene of various widths
Authors: Lee Hee-Jo , Hong Young-Pyo
Published: March 2018

In this paper, a radio-frequency circuit model of an interdigital capacitor (IDC) with a multilayer graphene (MLG) width variation is proposed. The circuit model with three sample configurations, i.e., a bare IDC, IDC-MLG with a width of 5 μm, and IDC-MLG with a width of 20 μm, is constructed via a fitted method based on the measured samples. The simulated results of the circuit model are validated through the RF characteristics, e.g., the capacitance and the self-resonance frequency, of the measured samples. From the circuit model, all samples show not only a similar capacitance behavior but also an identical self-resonance frequency of 10 GHz. Moreover, the R, L, and C values of MLG with a 5 μm width (MLG with a 20 μm width) alone are approximately 0.8 kΩ (0.5 kΩ), 0.5 nH (0.9 nH), and 0.3 pF (0.1 pF), respectively. As a result, we find that the simulated results are in good agreement with RF characteristics of the measured samples. In the future, we expect that the proposed circuit model of an IDC with MLG will offer assistance with performance predictions of diverse IDC-based 2D material applications, such as biosensors and gas sensors, as well as supercapacitors.
Theoretical study of native point defects in strained-layer superlattice systems
Authors: Krishnamurthy S. , Yu Zhi Gang
Published: March 2018

We developed a theoretical approach that employs first-principles Hamiltonians, tight-binding Hamiltonians, and Green's function techniques to obtain energy levels arising from native point defects (NPDs) in InAs-GaSb and InAs-InAs1-xSbx strained layer superlattice (SLS) systems. In InAs and GaSb regions, we considered four types of NPDs—anion vacancy, cation vacancy, anion anti-site, and cation anti-site—as well as isoelectronic substitution at anion sites (Sb at the As site and As at the Sb site). Additionally, we considered three types of defects—the cation at the second anion site, the second anion at the cation site, and second anion vacancy—in the InAs1-xSbx alloy region of the SLS. For a selected few designs, we studied NPDs both in the bulk region and near the interfaces of the SLS. We have considered 12 designs of InAs-GaSb systems and two designs of InAs-InAs0.7Sb0.3 systems lattice-matched to the GaSb substrate. The calculated defect levels not only agreed well with available measurements, but also revealed the connection between mid-gap levels and specific NPDs. We further calculated defect formation energies both in compounds and in all superlattices considered above. Since the absolute value of defect formation energy depends considerably on growth conditions, we evaluated the formation energies in SLS with respect to their value in the corresponding bulk or alloy. The calculated defect formation energies, together with defect energy level results, allow us to identify a few promising SLS designs for high-performing photodetectors.
Ground states for fractional Schrödinger equations with critical growth
Authors: Li Quanqing , Teng Kaimin , Wu Xian
Published: March 2018

In this paper, we study the following critical fractional Schrödinger equation: (−Δ)su+V(x)u=|u|2s*−2u+λf(x,u), x∈RN, where λ > 0, 0 < s < 1, N > 2s, 2s*=2NN−2s, (−Δ)s denotes the fractional Laplacian of order s, and f is a continuous superlinear but subcritical function. When V and f are asymptotically periodic in x, we prove that the equation has a ground state solution for large λ by the Nehari method.
Self-assembly of silica microparticles in magnetic multiphase flows: Experiment and simulation
Authors: Li Xiang , Niu Xiao-Dong , Li You , Chen Mu-Feng
Published: March 2018

Dynamic self-assembly, especially self-assembly under magnetic field, is vital not only for its marvelous phenomenon but also for its mechanisms. Revealing the underlying mechanisms is crucial for a deeper understanding of self-assembly. In this paper, several magnetic induced self-assembly experiments by using the mixed magnetic multiphase fluids comprised of silica microspheres were carried out. The relations of the strength of external magnetic field, the inverse magnetorheological effect, and the structures of self-assembled particles were investigated. In addition, a momentum-exchanged immersed boundary-based lattice Boltzmann method (MEIB-LBM) for modeling multi-physical coupling multiphase flows was employed to numerically study the magnetic induced self-assembly process in detail. The present work showed that the external magnetic field can be used to control the form of self-assembly of nonmagnetic microparticles in a chain-like structure, and the self-assembly process can be classified into four stages with magnetic hysteresis, magnetization of nonmagnetic microparticles, self-assembly in chain-like structures, and the stable chain state. The combination of experimental and numerical results could offer a method to control the self-assembled nonmagnetic microparticles, which can provide the technical and theoretical support for the design and fabrication of micro/nanomaterials.
Elastic Wannier-Stark ladders and Bloch oscillations in 1D granular crystals
Authors: Shi Xiaotian , Chaunsali Rajesh , Wu Ying , Yang Jinkyu
Published: March 2018

We report the numerical and experimental study of elastic Wannier-Stark ladders and Bloch oscillations in a tunable one-dimensional granular chain consisting of cylindrical particles. The Wannier-Stark ladders are obtained by tuning the contact angles to introduce a gradient in the contact stiffness along the granular chain. These ladders manifest as resonant modes localized in the space. When excited at the corresponding resonant frequencies, we demonstrate the existence of time-resolved Bloch oscillations. The direct velocity measurements using laser Doppler vibrometry agree well with the numerical simulation results. We also show the possibility of further tailoring these Bloch oscillations by numerical simulations. Such tunable systems could be useful for applications involving the spatial localization of elastic energy.
Optically pumped lasing of an electrically active hybrid OLED-microcavity
Authors: Meister S. , Brückner R. , Sudzius M. , Fröb H. , Leo K.
Published: March 2018

Highly conductive electrodes are a prerequisite for electrically pumped organic lasers. We investigate the influence of very thin metal contacts in an electrically active organic microcavity. We test different deposition techniques and seed layers to decrease the thickness of the metal layers and reduce possibly harmful absorption. For such very thin contacts, the spectral position of the modes is modeled by simulated modes using the transfer-matrix-algorithm. The input-output characteristics of the device without, with bottom, with top, and with both metal layer(s) are recorded. These measurements allow us to understand and improve the impact on the functionality. With these results and the help of a theoretical approximation, we determine the minimal current density needed to reach the lasing threshold for electrical pumping in this sample structure.