Abstract: Earphones and headphones, which are compact electro-acoustic transducers, tend to have a lot of acoustic absorption materials and porous materials known as dampers, which often have a large number of extremely small holes and narrow slits to inhibit the resonance of the vibrating system, because the air viscosity significantly affects the acoustic characteristics in such acoustic paths. In order to perform simulations using the finite element method (FEM), it is necessary to be aware of material characteristics such as the impedance and propagation constants of sound absorbing materials and porous materials. The transfer function is widely known as a measurement method for an acoustic tube with such physical properties, but literature describing the measurements at the upper limits of the audible range is yet to be found. The acoustic tube, which is a measurement instrument, must be made narrow, and the distance between the two sets of microphones must be shortened in order to take measurements of acoustic characteristics at higher frequencies. When such a tube is made narrow, however, the characteristic impedance has been observed to become lower than the impedance of air. This paper considers the cause of this phenomenon to be the effect of the air viscosity and describes an FEM analysis of an acoustic tube considering air viscosity to compare to the theoretical formula by including the effect of air viscosity in the theoretical formula for an acoustic tube.
Abstract: Numerical simulation performed to investigate the behavior of the high pressure hydrogen jetting of air. High pressure hydrogen (30–40 MPa) was injected to air at atmospheric pressure through 2mm orifice. Numerical simulations were performed with Kiva3V code with 2D axisymmetric geometry. Numerical simulations showed that auto ignition of high pressure hydrogen to air are possible due to molecular diffusion. Auto ignition was predicted at hydrogen-air contact surface due to mass and energy exchange between high temperature hydrogen and air heated by shock wave.
Abstract: Considering the increasing need of biofuels in Europe and the legislative requirements of the European Union it is needed to quantify the greenhouse gas emissions of biofuels life cycle. In this article a carbon footprint analysis to quantify these gases emitted during production and use of Romanian rapeseed oil (RO) and biodiesel from rapeseed oil (RME) was conducted. The functional unit was considered the LHV of diesel oil of 42.8 MJ·kg-1 corresponding to 1.15kg. of RO and 1.10 kg. of RME. When the 3 fuels were compared, the results show important benefits when using rapeseed oil or biodiesel instead of diesel. The most impacting stage in terms of GHG emissions is the use of the fuels. In this stage, rapeseed oil registers a total quantity of 3,229 kg CO2eq.·FU-1 and biodiesel register a total quantity of 3,088 kg CO2eq.·FU-1 while mineral diesel registers a total quantity of 3,156 kg CO2eq.·FU-1 emitted in the air. Taking into account that rape plant absorbed during growth stage the same quantity of CO2 as emitted into atmosphere during usage stage of the fuel, when compared the three fuels, rapeseed oil and biodiesel obtain obvious benefits against fossil diesel. Results show that by substituting diesel with RO a total quantity of 5,663 kg. CO2eq.·FU-1 would be saved while using biodiesel a total quantity of 5,570 kg. CO2eq.·FU-1 can be saved.
Abstract: No negative control nor control to prevent microbes from escaping was set when the S-shaped flask experiments were performed by Pasteur. Microscope was not used to observe the media in the flasks. Louis Pasteur’s S-shaped flask experiment was re-examined by using U-shaped flasks, modified S-shaped flasks and microscope. A mixture of microbes was isolated from the room air, from which one rod-shaped Bacillus species with proposed name Bacillus gaso-mobilis sp nov and one grape-shaped Staphylococcus species with proposed name of Staphylococcus gaso-mobilis sp nov were identified. Their penicillin and ampicillin resistant strains containing plasmids were isolated. These bacteria could change color, produce odor and automatically move in the air. They did not form colonies on solid media. They had a high suspension capacity in liquid media. Their light absorbance peaked at the wave length of 320 nm. It was concluded that there were flaws with Louis Pasteur’s S-shaped flask experiments.
Abstract: This work presents a numerical simulation of the interaction of an incident shock wave propagates from the left to the right with a cone placed in a tube at shock. The Mathematical model is based on a non stationary, viscous and axisymmetric flow. The Discretization of the Navier-stokes equations is carried out by the finite volume method in the integral form along with the Flux Vector Splitting method of Van Leer. Here, adequate combination of time stepping parameter, CFL coefficient and mesh size level is selected to ensure numerical convergence. The numerical simulation considers a shock tube filled with air. The incident shock wave propagates to the right with a determined Mach number and crosses the cone by leaving behind it a stationary detached shock wave in front of the nose cone. This type of interaction is observed according to the time of flow.
Abstract: The paper deals with the development of portable aerosol concentrator and its application for the determination of nitrites and nitrates. The device enables the continuous trapping of pollutants in the air. An extensive literature search has been elaborated which aims at the development of samplers and the possibilities of their application in the continuous determination of volatile organic compounds. The practical part of the paper is focused on the development of the portable aerosol concentrator. The device using the Aerosol Enrichment Unit has been experimentally verified and subsequently realized. It operates on the principle of equilibrium accumulation of pollutants from the gaseous phase using absorption liquid polydisperse aerosol. The device has been applied for monitoring nitrites and nitrates in the air. The chemiluminescence detector was used for detection; the achieved detection limit for nitrites was 28 ng/m3 and for nitrates 78 ng/m3.
Abstract: This study presents design of a carbon silicon electrode
for iontophorsis treatment towards alopecia. The alopecia is a medical
description means loss of hair from the body. For solving this problem,
the drug need to be delivered into the scalp, therefore, the
iontophoresis was chosen to use in this treatment. However, almost
common electrodes of iontophoresis device are made with metal
material, the electrodes could give patients hurt when they using it, and
it is hard to avoid the hair for attaching the hair. For this reason, an
electrode is made with silicon material to decrease the hurt from the
electrodes, and the carbon material is mixed in it for increasing
conductance. The several cones with stainless material on the
electrode make the electrode is able to void hair to attach the affected
part. According to the results of a vivo-experiment, the carbon silicon
electrode showed a good performance and in treatment comfortably.
Abstract: This article is presented an experimental and modeling
study of a four-bed pressure swing adsorption process using
zeolite13X to provide oxygen-enriched air. The binary mixture N2/O2
(79/21 vol %) was used as a feed stream. The effects of purge/feed
ratio (P/F), adsorption pressure, cyclic time and product flow rate on
product purity and recovery under nonisothermal condition were
studied. The adsorption dynamics of process were determined using
a mathematical model incorporated mass and energy balances. A
Mathlab code using finite difference method was developed to solve
the set of coupled differential-algebraic equations, and the simulation
results are agreed well with experimental results.
Abstract: This paper presents a cold flow simulation study of a small gas turbine combustor performed using laboratory scale test rig. The main objective of this investigation is to obtain physical insight of the main vortex, responsible for the efficient mixing of fuel and air. Such models are necessary for predictions and optimization of real gas turbine combustors. Air swirler can control the combustor performance by assisting in the fuel-air mixing process and by producing recirculation region which can act as flame holders and influences residence time. Thus, proper selection of a swirler is needed to enhance combustor performance and to reduce NOx emissions. Three different axial air swirlers were used based on their vane angles i.e., 30°, 45°, and 60°. Three-dimensional, viscous, turbulent, isothermal flow characteristics of the combustor model operating at room temperature were simulated via Reynolds- Averaged Navier-Stokes (RANS) code. The model geometry has been created using solid model, and the meshing has been done using GAMBIT preprocessing package. Finally, the solution and analysis were carried out in a FLUENT solver. This serves to demonstrate the capability of the code for design and analysis of real combustor. The effects of swirlers and mass flow rate were examined. Details of the complex flow structure such as vortices and recirculation zones were obtained by the simulation model. The computational model predicts a major recirculation zone in the central region immediately downstream of the fuel nozzle and a second recirculation zone in the upstream corner of the combustion chamber. It is also shown that swirler angles changes have significant effects on the combustor flowfield as well as pressure losses.
Abstract: A solar powered air heating system using one ended evacuated tubes is experimentally investigated. A solar air heater containing forty evacuated tubes is used for heating purpose. The collector surface area is about 4.44 m2. The length and outer diameters of the outer glass tube and absorber tube are 1500, 47 and 37 mm, respectively. In this experimental setup, we have a header (heat exchanger) of square shape (190 mm x 190 mm). The length of header is 1500 mm. The header consists of a hollow pipe in the center whose diameter is 60 mm through which the air is made to flow. The experimental setup contains approximately 108 liters of water. Water is working as heat collecting medium which collects the solar heat falling on the tubes. This heat is delivered to the air flowing through the header pipe. This heat flow is due to natural convection and conduction. The outlet air temperature depends upon several factors along with air flow rate and solar radiation intensity. The study has been done for both up-flow and down-flow of air in header in similar weather conditions, at different flow rates. In the present investigations the study has been made to find the effect of intensity of solar radiations and flow rate of air on the out let temperature of the air with time and which flow is more efficient. The obtained results show that the system is highly effective for the heating in this region. Moreover, it has been observed that system is highly efficient for the particular flow rate of air. It was also observed that downflow configuration is more effective than up-flow condition at all flow rates due to lesser losses in down-flow. The results show that temperature differences of upper head and lower head, both of water and surface of pipes on the respective ends is lower in down-flow.
Abstract: The paper describes ergonomics problems trend of
student at B5101 classroom building 2, Suranaree University of
Technology. The objective to survey ergonomics problems and effect
from use chairs for sitting in class room. The result from survey
method 100 student they use lecture chair for sitting in classroom
more than 2 hours/ day by RULA[1]. and Body discomfort survey[2].
The result from Body discomfort survey contribute fatigue problems
at neck, lower back, upper back and right shoulder 2.93, 2.91, 2.33,
1.75 respectively and result from RULA contribute fatigue problems
at neck, body and right upper arm 4.00, 3.75 and 3.00 respectively
are consistent. After that the researcher provide improvement plan
for design new chair support student fatigue reduction by prepare
data of sample anthropometry and design ergonomics chair prototype
3 unit. Then sample 100 student trial to use new chair and evaluate
again by RULA, Body discomfort and satisfaction. The result from
trial new chair after improvement by RULA present fatigue reduction
average of head and neck from 4.00 to 2.25 , body and trunk from
3.75 to 2.00 and arm force from 1.00 to 0.25 respectively. The result
from trial new chair after improvement by Body discomfort present
fatigue reduction average of lower back from 2.91 to 0.87, neck from
2.93 to 1.24, upper back 2.33 to 0.84 and right upper arm from 1.75
to 0.74. That statistical of RULA and Body discomfort survey
present fatigue reduction after improvement significance with a
confidence level of 95% (p-value 0.05). When analyzing the
relationship of fatigue as part of the body by Chi – square test during
RULA and Body discomfort that before and after improvements were
consistent with the significant level of confidence 95% (p-value 0.05)
. Moreover the students satisfaction result from trial with a new chair
for 30 minutes [3]. 72 percent very satisfied of the folding of the
secondary writing simple 66% the width of the writing plate, 64% the
suitability of the writing plate, 62% of soft seat cushion and 61%
easy to seat the chair.
Abstract: In this experimental study, performance of a counter
flow Ranque-Hilsch vortex tube (RHVT) with threads cut on its inner
surface was investigated experimentally (pitch is 1 and 2 mm). The
inner diameter of the vortex tube used was D=9 mm and the ratio of
the tube’s length to diameter was L/D=12. The experimental system
was a thermodynamic open system. Flow was controlled by a valve
on the hot outlet side, where the valve was changed from a nearly
closed position to its nearly open position. Fraction of cold flow (ξ) =
0.1-0.9, was determined under 300 and 350 kPa pressurized air. All
experimental data were compared with each other, the maximum
heating performance of the RHVT system was found to be 38.2 oC
and the maximum cooling performance of the RHVT in this study
was found to be -30.9 oC at pitch 1 mm.
Abstract: The previous researches focused on the influence of
anthropogenic greenhouse gases exerting global warming, but not
consider whether desert sand may warm the planet, this could be
improved by accounting for sand's physical and geometric properties.
Here we show, sand particles (because of their geometry) at the desert
surface form an extended surface of up to 1 + π/4 times the planar area
of the desert that can contact sunlight, and at shallow depths of the
desert form another extended surface of at least 1 + π times the planar
area that can contact air. Based on this feature, an enhanced heat
exchange system between sunlight, desert sand, and air in the spaces
between sand particles could be built up automatically, which can
increase capture of solar energy, leading to rapid heating of the sand
particles, and then the heating of sand particles will dramatically heat
the air between sand particles. The thermodynamics of deserts may
thus have contributed to global warming, especially significant to
future global warming if the current desertification continues to
expand.
Abstract: the paper presents the optimization results for several
electrical machines dedicated for powered electric wheel-chairs. The
optimization, using the Hook-Jeeves algorithm, was employed based
on a design approach which takes into consideration the road
conditions. Also, through numerical simulations (based on finite
element method), the analytical approach was validated. The
optimization approach gave satisfactory results and the best suited
variant was chosen for the motorization of the wheel-chair.
Abstract: Stochastic comparison has been an important
direction of research in various area. This can be done by the use of
the notion of stochastic ordering which gives qualitatitive rather than
purely quantitative estimation of the system under study. In this
paper we present applications of comparison based uncertainty
related to entropy in Reliability analysis, for example to design
better systems. These results can be used as a priori information in
simulation studies.
Abstract: A simple model for studying convectional lifting
processes in the tropics is described in this paper with some tests of
the model in dry air. The model consists of the density equation, the
wind equation, the vertical velocity equation, and the temperature
equation. The model domain is two-dimensional with length 100 km
and height 17.5 km. Plan for experiments to investigate the effects of
the heating surface, the deep convection approximation and the
treatment of velocities at the boundaries are discussed. Equations for
the simplified treatment of moisture in the atmosphere in future
numerical experiments are also given.
Abstract: Air conditioning is mainly to be used as human
comfort medium. It has been use more often in country in which the
daily temperatures are high. In scientific, air conditioning is defined
as a process of controlling the moisture, cooling, heating and cleaning
air. Without proper estimation of cooling load, big amount of waste
energy been used because of unsuitable of air conditioning system are
not considering to overcoming heat gains from surrounding. This is
due to the size of the room is too big and the air conditioning has to
use more energy to cool the room and the air conditioning is too
small for the room. The studies are basically to develop a program to
calculate cooling load. Through this study it is easy to calculate
cooling load estimation. Furthermore it-s help to compare the cooling
load estimation by hourly and yearly. Base on the last study that been
done, the developed software are not user-friendly. For individual
without proper knowledge of calculating cooling load estimation
might be problem. Easy excess and user-friendly should be the main
objective to design something. This program will allow cooling load
able be estimate by any users rather than estimation by using rule of
thumb. Several of limitation of case study is judged to sure it-s
meeting to Malaysia building specification. Finally validation is done
by comparison manual calculation and by developed program.
Abstract: This paper presents a synthetic jet air blower actuated
by PZT for air blowing for air-breathing micro PEM fuel cell. The
several factors to affect the performance of air-breathing PEM fuel cell
such as air flow rate, opening ratio and cathode open type in the
cathode side were studied. Especially, an air flow rate is critical
condition to improve its performance. In this paper, we developed a
synthetic jet air blower to supply a high stoichiometric air flow. The
synthetic jet mechanism is a zero mass flux device that converts
electrical energy into the momentum. The synthetic jet actuation is
usually generated by a traditional PZT actuator, which consists of a
small cylindrical cavity, in/outlet channel and PZT diaphragms. The
flow rate of the fabricated synthetic jet air blower was 400cc/min at
550Hz and its power consumption was very low under 0.3W. The
proposed air-breathing PEM fuel cell which installed synthetic jet air
blower was higher performance and stability during continuous
operation than the air-breathing fuel cell without auxiliary device to
supply the air. The results showed that the maximum power density
was 188mW/cm2 at 400mA/cm2. This maximum power density and
durability were improved more than 40% and 20%, respectively.
Abstract: In the last decade, energy based control theory has undergone a significant breakthrough in dealing with underactated mechanical systems with two successful and similar tools, controlled Lagrangians and controlled Hamiltanians (IDA-PBC). However, because of the complexity of these tools, successful case studies are lacking, in particular, MIMO cases. The seminal theoretical paper of controlled Lagrangians proposed by Bloch and his colleagues presented a benchmark example–a 4 d.o.f underactuated pendulum on a cart but a detailed and completed design is neglected. To compensate this ignorance, the note revisit their design idea by addressing explicit control functions for a similar device motivated by a vector thrust body hovering in the air. To the best of our knowledge, this system is the first MIMO, underactuated example that is stabilized by using energy based tools at the courtesy of the original design idea. Some observations are given based on computer simulation.
Abstract: A simple approach is demonstrated for growing large
scale, nearly vertically aligned ZnO nanowire arrays by thermal
oxidation method. To reveal effect of temperature on growth and
physical properties of the ZnO nanowires, gold coated zinc substrates
were annealed at 300 °C and 400 °C for 4 hours duration in air. Xray
diffraction patterns of annealed samples indicated a set of well
defined diffraction peaks, indexed to the wurtzite hexagonal phase of
ZnO. The scanning electron microscopy studies show formation of
ZnO nanowires having length of several microns and average of
diameter less than 500 nm. It is found that the areal density of wires
is relatively higher, when the annealing is carried out at higher
temperature i.e. at 400°C. From the field emission studies, the values
of the turn-on and threshold field, required to draw emission current
density of 10 μA/cm2 and 100 μA/cm2 are observed to be 1.2 V/μm
and 1.7 V/μm for the samples annealed at 300 °C and 2.9 V/μm and
3.7 V/μm for that annealed at 400 °C, respectively. The field
emission current stability, investigated over duration of more than 2
hours at the preset value of 1 μA, is found to be fairly good in both
cases. The simplicity of the synthesis route coupled with the
promising field emission properties offer unprecedented advantage
for the use of ZnO field emitters for high current density
applications.