982 research outputs found
Verification of mathematical model of pressure distribution in artificial knee joint
ArticleThe paper deals with pressure distribution measurement in knee arthroplasty, which is
an artificial replacement of human knee joint. The scope of the article is to verify the accuracy of
a mathematical model by real measurements. The calculated pressure values basing on the
mathematical model are compared with actually measured pressure values in the contact area of
the joint. Hereby maximal load the in the contact area, the distribution of the pressure and any
potentially dangerous pressure deviations during the walk cycle are checked. To enable accurate
pressure distribution measurement without interfering into human’s body, a sophisticated
measuring setup was created: the contact area of the joint was equipped with several pressure
sensors and a machine simulating the human walk cycle was used. The measured pressure data
are finally compared with those from the mathematical model and with the strength limit of the
used material, to verify the accuracy of the mathematical model experimentally
Plantograf V18 – new construction and properties
ArticleThe article describes Plantograf
V18, a planar tactile transducer, which converts the
applied pressure into electric signal and enables a graphical presentation of the measured data;
the new version V18 comes with some significant improvements and modifications. The device
may be used ev
erywhere where the pressure distribution between an object and surface is to be
determined, e.g. in medicine or automotive industry. The article contains the detailed description
of the transducer design and its electronic control circuits, as well as the
yet unpublished
measurements of pressure sensitivity with 3.5
mm electrodes
IoT applications utilizing excess heat in electrical lighting fixtures
The development of IoT instrumentation will always be strongly influenced by the properties of the power supply system. A large number of IoT nodes creates a danger of extra expenditures when changing the battery. For this reason, the development of supply nodes tends to prefer systems capable of battery-less operation, obtaining energy from other sources. This article deals with an alternative method of electrical energy acquisition form the excessive heat appearing in LED lighting fixtures utilizing large-area LED chips. A Peltier cell was used for the conversion of heat energy to electrical energy, connected as thermo-electric generator into the thermal chain
Biochar dosage impact on physical soil properties and crop status
In the context of climate change and the ongoing population growth, current agriculture
inevitably faces many challenges. Long periods of drought are often followed by shorter periods
of heavy precipitation and degraded soil is often unable to retain the rainfall water properly. Apart
from common organic fertilizers, soil amendments are currently considered a promising solution
that might improve soil quality. The most discussed one is biochar, a natural soil conditioner that
might under certain conditions improve soil properties. This study is based on the experiment that
was established in 2017 in order to determine the impact of biochar dosage and it’s effect over
time. Four parcels approximately 15×30 m were designed in Rapotín, Czech Republic. Each of
them was treated with a specific dose of biochar (15, 30, 45, 60 t ha-1
), and selected soil physical
properties such as penetration resistance and reduced bulk density were then measured at the
beginning of the cropping season 2019. In addition, vegetation properties were investigated with
the use of handheld sensors repeatedly during the season on winter wheat. The dataset contained
information about chlorophyll and nitrogen content as well as Normalized Difference Vegetation
Index estimations. Acquired values were later compared with the results obtained from the fifth
variant founded in 2014 with a 15 t ha-1 dose and from the control variant. Although the dosage
levels applied were quite substantial, no significant difference was found when evaluating
selected soil properties. Crop response gave similar results. Any of the examined characteristics
differed among the 2017 variants and control. Nevertheless, when compared to the 2014 variant,
clearly different results were detected. Thus, this study concluded that the effect of biochar dosage
is might not be as significant factor, however, the time effect likely is. Therefore, the study has
to continue and soil/crop properties will be observed in the upcoming season as well
Technical design of complex vision-tactile navigation system for using of blind persons navigation
ArticleThis article presents the system used for navigation and orientation of blind persons in
an unknown terrain. This system called
‘
Tactile Navigation System
’
constitutes a compensation
instrument for blind persons. It is composed from three basic elements: a
camera, a control unit
and a tactile activator. The tactile navigation system converts the image from the camera to the
tactile information and it transfers this information to the blind person. The blind person can
recognize by vibration of the tactile a
ctivator placed on the antebrachium whether he comes on
an impediment or if he can continue free walking. The main advantage of this system is the
possibility of detecting any individual impediment earlier than using other common compensation
tools, such a
s a simple blind stick, which is not a competitor with this device, but a helper. This
way the system facilitates the orientation of a blind person an in an unknown terrain. The article
describes in detail the overall composition and functionality of the s
ystem as well as the principle
and funct
ion of its individual elements
Photoluminescence rings in Corbino disk at quantizing magnetic fields
Spatially resolved photoluminescence of modulation doped AlGaAs/GaAs
heterojunction was investigated in a sample of Corbino disk geometry subject to
strong perpendicular magnetic fields. Significant spatial modulation of the
photoluminescence was observed in form of one or more concentric rings which
travelled across the sample when the magnetic field strength was varied. A
topology of the observed structure excludes the possibility of being a trace of
an external current. The effect is attributed to formation of compressible and
incompressible stripes in a 2DEG density gradient across the sample.Comment: 5 two-column pages, 4 figures (one of them in color
Changes in soil properties and possibilities of reducing environmental risks due to the application of biological activators in conditions of very heavy soils
This study aims at verifying the effect of farmyard manure (FYM) and of selected
activators (Z'fix and NeoSol) on changes of soil properties. Their application should lead to
improvement of soil physical properties and of organic matter fixation, to reduction of
environmental risks, e.g. of tillage energy requirements. Experimental variants (0.7 ha each) were
as follows: I (FYM with Z'fix); II (FYM with Z'fix + NeoSol); III (FYM); IV (Control NPK only).
FYM was applied at rates: 50 t ha-1
(2014); 30 t ha-1
(2016). Additional NPK fertilizer (I–IV) was
applied according to annual crop nutrient normative. The agent Z'fix was used as an activator of
FYM biological transformation (5.5 kg t
-1
). The agent NeoSol was used as soil activator
(200 kg ha-1
; annually). In order to verify the effect, cone index, bulk density, tillage implement
draft and chemical soil components (Humus, C/N ration and Ntot) were measured annually.
Compared to the control, the application of FYM combined with the mentioned agents (I–III)
increased Ntot more than two times. Moreover, it decreased (I–III) bulk density by 8.7%. Tillage
implement draft decreased by 3% after the application of FYM with Z’fix (I, II). The study
confirmed that FYM application combined with utilization of activators positively influenced soil
fertility and helped to reduce environmental risks
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