Abstract: In the present work, we revisit the collapse process of a spherically symmetric homogeneous scalar field (in FRW background) minimally coupled to gravity, when the phase-space deformations are taken into account. Such a deformation is mathematically introduced as a particular type of noncommutativity between the canonical momenta of the scale factor and of the scalar field. In the absence of such deformation, the collapse culminates in a spacetime singularity. However, when the phase-space is deformed, we find that the singularity is removed by a non-singular bounce, beyond which the collapsing cloud re-expands to infinity. More precisely, for negative values of the deformation parameter, we identify the appearance of a negative pressure, which decelerates the collapse to finally avoid the singularity formation. While in the un-deformed case, the horizon curve monotonically decreases to finally cover the singularity, in the deformed case the horizon has a minimum value that this value depends on deformation parameter and initial configuration of the collapse. Such a setting predicts a threshold mass for black hole formation in stellar collapse and manifests the role of non-commutative geometry in physics and especially in stellar collapse and supernova explosion.
Abstract: There is a widespread belief in everyday discourse that science subjects (physics, chemistry and biology) are, along with math, the most difficult school subjects in the education of an individual. This assumption is usually justified by the following facts: low GPA in these subjects, the number of pupils who fail these subjects is high in comparison to other subjects, and the number of pupils interested in continuing their studies in the fields with a focus on science subjects is lower compared to non-science-oriented fields. From that perspective, the project: “Could it be different? How do children explore it?” becomes extremely interesting because it is focused on young children and on the introduction of new methods, with aim of arousing interest in scientific literacy development in 10 kindergartens by applying the methodology of an action research, with an ethnographic approach. We define scientific literacy as a process of encouraging and nurturing the research and explorative spirit in children, as well as their natural potential and abilities that represent an object of scientific research: to learn about exploration by conducting exploration. Upon project completion, an evaluation questionnaire was created for the parents of the children who had participated in the project, as well as for those whose children had not been involved in the project. The purpose of the first questionnaire was to examine the level of satisfaction with the project implementation and its outcomes among those parents whose children had been involved in the project (N=142), while the aim of the second questionnaire was to find out how much the parents of the children not involved (N=154) in this activity were interested in this topic.
Abstract: Fundamental basics of pure and applied research in the area of magneto-thermo-mechanical numerical analysis and design of innovative electromagnetic devices (modern induction heaters, novel thermoelastic actuators, rotating electrical machines, induction cookers, electrophysical devices) are elaborated. Thus, mathematical models of magneto-thermo-mechanical processes in electromagnetic devices taking into account main interactions of interrelated phenomena are developed. In addition, graphical representation of coupled (multiphysics) phenomena under consideration is proposed. Besides, numerical techniques for nonlinear problems solution are developed. On this base, effective numerical algorithms for solution of actual problems of practical interest are proposed, validated and implemented in applied 2D and 3D computer codes developed. Many applied problems of practical interest regarding modern electrical engineering devices are numerically solved. Investigations of the influences of various interrelated physical phenomena (temperature dependences of material properties, thermal radiation, conditions of convective heat transfer, contact phenomena, etc.) on the accuracy of the electromagnetic, thermal and structural analyses are conducted. Important practical recommendations on the choice of rational structures, materials and operation modes of electromagnetic devices under consideration are proposed and implemented in industry.
Abstract: A teacher’s attitude to creativity plays an essential role in the thinking development of his/her students. The purpose of this study is to understand if a science teacher's personal creativity can modify his/her ability to produce various kinds of questions. This research used an education activity based on cosmic sketches and pictures by K.E. Tsiolkovsky, the founder of astronautics, to explore if any relationship between individual creativity and the asking questions skill exists. As a screening instrument, which allows an assessment of the respondent's creative potential, a common test of creative thinking was used. The results of the creativity test and the diversity of the questions are mentioned.
Abstract: The selection of diffractive events in the ALICE experiment during the first data taking period (RUN-I) of the Large Hadron Collider (LHC) was limited by the range over which rapidity gaps occur. It would be possible to achieve better measurements by expanding the range in which the production of particles can be detected. For this purpose, the ALICE Diffractive (AD0) detector has been installed and commissioned for the second phase (RUN-II). Any new detector should be able to take the data synchronously with all other detectors and be operated through the ALICE central systems. One of the key elements that must be developed for the AD0 detector is the Detector Control System (DCS). The DCS must be designed to operate safely and correctly this detector. Furthermore, the DCS must also provide optimum operating conditions for the acquisition and storage of physics data and ensure these are of the highest quality. The operation of AD0 implies the configuration of about 200 parameters, from electronics settings and power supply levels to the archiving of operating conditions data and the generation of safety alerts. It also includes the automation of procedures to get the AD0 detector ready for taking data in the appropriate conditions for the different run types in ALICE. The performance of AD0 detector depends on a certain number of parameters such as the nominal voltages for each photomultiplier tube (PMT), their threshold levels to accept or reject the incoming pulses, the definition of triggers, etc. All these parameters define the efficiency of AD0 and they have to be monitored and controlled through AD0 DCS. Finally, AD0 DCS provides the operator with multiple interfaces to execute these tasks. They are realized as operating panels and scripts running in the background. These features are implemented on a SCADA software platform as a distributed control system which integrates to the global control system of the ALICE experiment.
Abstract: The GERmanium Detector Array (GERDA) experiment,
located at the Laboratori Nazionali del Gran Sasso (LNGS) of
INFN, searches for 0νββ of 76Ge. Germanium diodes enriched to
∼ 86 % in the double beta emitter 76Ge(enrGe) are exposed being
both source and detectors of 0νββ decay. Neutrinoless double beta
decay is considered a powerful probe to address still open issues
in the neutrino sector of the (beyond) Standard Model of particle
Physics. Since 2013, just after the completion of the first part of its
experimental program (Phase I), the GERDA setup has been upgraded
to perform its next step in the 0νββ searches (Phase II). Phase II aims
to reach a sensitivity to the 0νββ decay half-life larger than 1026 yr
in about 3 years of physics data taking. This exposing a detector
mass of about 35 kg of enrGe and with a background index of about
10^−3 cts/(keV·kg·yr). One of the main new implementations is the
liquid argon scintillation light read-out, to veto those events that only
partially deposit their energy both in Ge and in the surrounding LAr.
In this paper, the GERDA Phase II expected goals, the upgrade work
and few selected features from the 2015 commissioning and 2016
calibration runs will be presented. The main Phase I achievements
will be also reviewed.
Abstract: The fluid-structure coupling is a natural phenomenon which reflects the effects of two continuums: fluid and structure of different types in the reciprocal action on each other, involving knowledge of elasticity and fluid mechanics. The solution for such problems is based on the relations of continuum mechanics and is mostly solved with numerical methods. It is a computational challenge to solve such problems because of the complex geometries, intricate physics of fluids, and complicated fluid-structure interactions. The way in which the interaction between fluid and solid is described gives the largest opportunity for reducing the computational effort. In this paper, a problem of fluid structure interaction is investigated with two-way coupling method. The formulation Arbitrary Lagrangian-Eulerian (ALE) was used, by considering a dynamic grid, where the solid is described by a Lagrangian formulation and the fluid by a Eulerian formulation. The simulation was made on the ANSYS software.
Abstract: During manned exploration of space, missions will require astronaut crewmembers to perform Extra Vehicular Activities (EVAs) for a variety of tasks. These EVAs take place after long periods of operations in space, and in and around unique vehicles, space structures and systems. Considering the remoteness and time spans in which these vehicles will operate, EVA system operations should utilize common worksites, tools and procedures as much as possible to increase the efficiency of training and proficiency in operations. All of the preparations need to be carried out based on studies of astronaut motions. Until now, development and training activities associated with the planned EVAs in Russian and U.S. space programs have relied almost exclusively on physical simulators. These experimental tests are expensive and time consuming. During the past few years a strong increase has been observed in the use of computer simulations due to the fast developments in computer hardware and simulation software. Based on this idea, an effort to develop a computational simulation system to model human dynamic motion for EVA is initiated. This study focuses on the simulation of an astronaut moving the orbital replaceable units into the worksites or removing them from the worksites. Our physics-based methodology helps fill the gap in quantitative analysis of astronaut EVA by providing a multisegment human arm model. Simulation work described in the study improves on the realism of previous efforts, incorporating joint stops to account for the physiological limits of range of motion. To demonstrate the utility of this approach human arm model is simulated virtually using ADAMS/LifeMOD® software. Kinematic mechanism for the astronaut’s task is studied from joint angles and torques. Simulation results obtained is validated with numerical simulation based on the principles of Newton-Euler method. Torques determined using mathematical model are compared among the subjects to know the grace and consistency of the task performed. We conclude that due to uncertain nature of exploration-class EVA, a virtual model developed using multibody dynamics approach offers significant advantages over traditional human modeling approaches.
Abstract: Electric field is an important fundamental concept in
electrostatics. In high-school, generally Thai students have already
learned about definition of electric field, electric field due to a point
charge, and superposition of electric fields due to multiple-point
charges. Those are the prerequisite basic knowledge students holding
before entrancing universities. In the first-year university level,
students will be quickly revised those basic knowledge and will be
then introduced to a more complicated topic—electric field due to
continuous charged distributions. We initially found that our
freshman students, who were from the Faculty of Science and
enrolled in the introductory physic course (SCPY 158), often
seriously struggled with the basic physics concepts—superposition of
electric fields and inverse square law and mathematics being relevant
to this topic. These also then resulted on students’ understanding of
advanced topics within the course such as Gauss's law, electric
potential difference, and capacitance. Therefore, it is very important
to determine students' understanding of electric field due to
continuous charged distributions. The open-ended question about
sketching net electric field vectors from a uniformly charged
insulating rod was administered to 260 freshman science students as
pre- and post-tests. All of their responses were analyzed and
classified into five levels of understandings. To get deep
understanding of each level, 30 students were interviewed toward
their individual responses. The pre-test result found was that about
90% of students had incorrect understanding. Even after completing
the lectures, there were only 26.5% of them could provide correct
responses. Up to 50% had confusions and irrelevant ideas. The result
implies that teaching methods in Thai high schools may be
problematic. In addition for our benefit, these students’ alternative
conceptions identified could be used as a guideline for developing the
instructional method currently used in the course especially for
teaching electrostatics.
Abstract: Searching the “Island of stability” is a topic of
extreme interest in theoretical as well as experimental modern
physics today. This “island of stability” is spanned by superheavy
elements (SHE's) that are produced in the laboratory. SHE's are
believed to exist primarily due to the “magic” stabilizing effects of
nuclear shell structure. SHE synthesis is extremely difficult due to
their very low production cross section, often of the order of pico
barns or less. Stabilizing effects of shell closures at proton number
Z=82 and neutron number N=126 are predicted theoretically. Though
stabilizing effects of Z=82 have been experimentally verified, no
concluding observations have been made with N=126, so far. We
measured and analyzed the total evaporation residue (ER) cross
sections for a number of systems with neutron number around 126 to
explore possible shell closure effects in ER cross sections, in this
work.
Abstract: Average temperatures worldwide are expected to
continue to rise. At the same time, major cities in developing
countries are becoming increasingly populated and polluted.
Governments are tasked with the problem of overheating and air
quality in residential buildings. This paper presents the development
of a model, which is able to estimate the occupant exposure
to extreme temperatures and high air pollution within domestic
buildings. Building physics simulations were performed using the
EnergyPlus building physics software. An accurate metamodel is
then formed by randomly sampling building input parameters and
training on the outputs of EnergyPlus simulations. Metamodels are
used to vastly reduce the amount of computation time required when
performing optimisation and sensitivity analyses. Neural Networks
(NNs) have been compared to a Radial Basis Function (RBF)
algorithm when forming a metamodel. These techniques were
implemented using the PyBrain and scikit-learn python libraries,
respectively. NNs are shown to perform around 15% better than RBFs
when estimating overheating and air pollution metrics modelled by
EnergyPlus.
Abstract: Microcantilevers are the basic MEMS devices, which
can be used as sensors, actuators and electronics can be easily built
into them. The detection principle of microcantilever sensors is based
on the measurement of change in cantilever deflection or change in its
resonance frequency. The objective of this work is to explore the
analogies between mechanical and electrical equivalent of
microcantilever beams. Normally scientists and engineers working in
MEMS use expensive software like CoventorWare, IntelliSuite,
ANSYS/Multiphysics etc. This paper indicates the need of developing
electrical equivalent of the MEMS structure and with that, one can
have a better insight on important parameters, and their interrelation of
the MEMS structure. In this work, considering the mechanical model
of microcantilever, equivalent electrical circuit is drawn and using
force-voltage analogy, it is analyzed with circuit simulation software.
By doing so, one can gain access to powerful set of intellectual tools
that have been developed for understanding electrical circuits Later
the analysis is performed using ANSYS/Multiphysics - software based
on finite element method (FEM). It is observed that both mechanical
and electrical domain results for a rectangular microcantlevers are in
agreement with each other.
Abstract: The current statuses of lifetime test of LaB6 hollow
cathode at the Lanzhou Institute of Physics (LIP), China, was
described. 5A LaB6 hollow cathode was design for LIPS-200 40mN
Xenon ion thruster, and it could be used for LHT-100 80 mN Hall
thruster, too. Life test of the discharge and neutralizer modes of LHC-5
hollow cathode were stared in October 2011, and cumulative operation
time reached 17,300 and 16,100 hours in April 2015, respectively. The
life of cathode was designed more than 11,000 hours. Parameters of
discharge and key structure dimensions were monitored in different
stage of life test indicated that cathodes were health enough. The test
will continue until the cathode cannot work or operation parameter is
not in normally. The result of the endurance test of cathode
demonstrated that the LaB6 hollow cathode is satisfied for the required
of thruster in life and performance.
Abstract: The objective of this work is to carryout critical
comparison of different actuation mechanisms like electrostatic,
thermal, piezoelectric, and magnetic with reference to a micro
cantilever. The relevant parameters like force generated,
displacement are compared in actuation methods. With these results,
helps in choosing the best actuation method for a particular
application. In this study, Comsol/Multiphysics software is used.
Modeling and simulation is done by considering the micro cantilever
of same dimensions as an actuator using all the above mentioned
actuation techniques. In addition to their small size, micro actuators
consume very little power and are capable of accurate results. In this
work, a comparison of actuation mechanisms is done to decide the
efficient system in micro domain.
Abstract: Sub-Saharan Africa is described as the second fastest
growing in mobile phone penetration in the world more than in the
United States or the European Union. Mobile phones have been used
to provide a lot of opportunities to improve people’s lives in the
region such as in banking, marketing, entertainment, and paying for
various bills such as water, TV, and electricity. However, the
potential of mobile phones to enhance teaching and learning has not
been explored. This study presents an experience of developing and
delivering SMS based quiz questions used to assess mastery of
subject content knowledge of science and mathematics secondary
school teachers in Tanzania. The SMS quizzes were used as a follow
up support mechanism to 500 teachers who participated in a project
to upgrade subject content knowledge of teachers in science and
mathematics subjects in Tanzania. Quizzes of 10-15 questions were
sent to teachers each week for 8 weeks and the results were analyzed
using SPSS. Results show that teachers who participated in chemistry
and biology subjects have better performance compared to those who
participated in mathematics and physics subjects. Teachers reported
some challenges that led to poor performance, This research has
several practical implications for those who are implementing or
planning to use mobile phones in teaching and learning especially in
rural secondary schools in sub-Saharan Africa.
Abstract: Well logging records can help to answer many
questions from a wide range of special interested information and
basic petrophysical properties to formation evaluation of oil and gas
reservoirs. The accurate calculations of porosity in carbonate
reservoirs are the most challenging aspects of the well logging
analysis. Many equations have been developed over the years based
on known physical principles or on empirically derived relationships,
which are used to calculate porosity, estimate lithology, and water
saturation; however these parameters are calculated from well logs by
using modern technique in a current study. Nasiriya oil field is one of
the giant oilfields in the Middle East, and the formation under study
is the Mishrif carbonate formation which is the shallowest
hydrocarbon bearing zone in this oilfield. Neurolog software was
used to digitize the scanned copies of the available logs.
Environmental corrections had been made as per Schlumberger charts
2005, which supplied in the Interactive Petrophysics software. Three
saturation models have been used to calculate water saturation of
carbonate formations, which are simple Archie equation, Dual water
model, and Indonesia model. Results indicate that the Mishrif
formation consists mainly of limestone, some dolomite, and shale.
The porosity interpretation shows that the logging tools have a good
quality after making the environmental corrections. The average
formation water saturation for Mishrif formation is around 0.4-
0.6.This study is provided accurate behavior of petrophysical
properties with depth for this formation by using modern software.
Abstract: Let us consider that the entire universe is composed of
a single hydrogen atom within which the electron is moving around
the proton. In this case, according to classical theories of physics,
radiation, photons respectively, should be absorbed by the electron.
Depending on the number of photons absorbed, the electron radius of
rotation around the proton is established. Until now, the principle of
photons absorption by electrons and the electron transition to a new
energy level, namely to a higher radius of rotation around the proton,
is not clarified in physics. This paper aims to demonstrate that
radiation, photons respectively, have mass and negative electrostatic
charge similar to electrons but infinitely smaller. The experiments
which demonstrate this theory are simple: thermal expansion,
photoelectric effect and thermonuclear reaction.
Abstract: The modeling lung respiratory system that has complex anatomy and biophysics presents several challenges including tissue-driven flow patterns and wall motion. Also, the pulmonary lung system because of that they stretch and recoil with each breath, has not static walls and structures. The direct relationship between air flow and tissue motion in the lung structures naturally prefers an FSI simulation technique. Therefore, in order to toward the realistic simulation of pulmonary breathing mechanics the development of a coupled FSI computational model is an important step. A simple but physiologically relevant three-dimensional deep long geometry is designed and fluid-structure interaction (FSI) coupling technique is utilized for simulating the deformation of the lung parenchyma tissue that produces airflow fields. The real understanding of respiratory tissue system as a complex phenomenon have been investigated with respect to respiratory patterns, fluid dynamics and tissue viscoelasticity and tidal breathing period.
Abstract: Bringing forth a survey on recent higher order spline
techniques for solving boundary value problems in ordinary
differential equations. Here we have discussed the summary of the
articles since 2000 till date based on higher order splines like Septic,
Octic, Nonic, Tenth, Eleventh, Twelfth and Thirteenth Degree
splines. Comparisons of methods with own critical comments as
remarks have been included.
Abstract: To understand the friction stir welding process, it is
very important to know the nature of the material flow in and around
the tool. The process is a combination of both thermal as well as
mechanical work i.e. it is a coupled thermo-mechanical process.
Numerical simulations are very much essential in order to obtain a
complete knowledge of the process as well as the physics underlying
it. In the present work a model based approach is adopted in order to
study material flow. A thermo-mechanical based CFD model is
developed using a Finite Element package, Comsol Multiphysics.
The fluid flow analysis is done. The model simultaneously predicts
shear strain fields, shear strain rates and shear stress over the entire
workpiece for the given conditions. The flow fields generated by the
streamline plot give an idea of the material flow. The variation of
dynamic viscosity, velocity field and shear strain fields with various
welding parameters is studied. Finally the result obtained from the
above mentioned conditions is discussed elaborately and concluded.