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Wyświetlanie 1-9 z 9
Tytuł:
Temporal and dynamic changes in plantar pressure distribution, as well as in posture during slow walking in flat and high-heel shoes
Autorzy:
Jandova, Sona
Gajdoš, Miloslav
Urbanová, Katarína
Mikuľáková, Wioletta
Powiązania:
https://bibliotekanauki.pl/articles/306474.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
cykl chodu
postawa
płaszczyzna
gait cycle
stance
swing
frontal plane
sagittal plane
Opis:
The aim of the study was to assess the differences in plantar pressure distribution and in posture during slow and very slow walking on the treadmill in flat and high-heeled shoes. Methods: The Pedar-X® (Novel, Munich, Germany) measuring insoles were used to measure the plantar pressure distribution and to assess temporal parameters during walking on the treadmill with the speed v1 = 0.97 ms–1 and v2 = 0.56 ms–1 in flat shoes (FS) and HH. For postural measurement, the SonoSens Monitor Analyzer (Gefremed, Chemnitz, Germany) was used. Thirty healthy females who only occasionally wear HH volunteered to participate in the study (age: 21.8 ± 2.09 years, weight: 55.7 ± 4.05 kg, height: 1.66 ± 0.03 m). For statistical analysis the ANOVA, and paired t-test were used. Results: Significant differences in walking in HH were detected in temporal and plantar pressure variables, compared to FS. The walking speed influenced the temporal variables, but not the measured dynamic parameters, in either shoes. In the sagittal plane, significant differences in all sections of the spine were identified for v1 and v2. While walking in HH, lordosis at lumbar spine decreased significantly as well as at cervical spine, and kyphosis increased in the thoracic spine. In HH statistically significant differences between the walking speeds were observed particularly in the thoracic spine. Conclusions: Walking in high heels caused a plantar pressure changes and curvature of the spine, and the slowing of walking speed did not prevent these changes.
Źródło:
Acta of Bioengineering and Biomechanics; 2019, 21, 4; 131-138
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tutorial on operating characteristics of microprocessor-based multiterminal line current differential relays
Autorzy:
Kasztenny, B
Benmouyal, G
Altuve, H J
Fischer, N
Powiązania:
https://bibliotekanauki.pl/articles/410604.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
protective relaying
differential protection
Alpha Plane principle
Opis:
Line current differential (87L) protection schemes face extra challenges compared with other forms of differential protection, in addition to the traditional requirements of sensitivity, speed, and immunity to current transformer saturation. Some of these challenges include data communication, alignment, and security; line charging current; and limited communications bandwidth. To address these challenges, microprocessor-based 87L relays apply elaborate operating characteristics, which are often different than a traditional percentage differential characteristic used for bus or transformer protection. These sophisticated elements may include adaptive restraining terms, apply an Alpha Plane, use external fault detection logic for extra security, and so on. While these operating characteristics provide for better performance, they create the following challenges for users: x Understanding how the 87L elements make the trip decision. x Understanding the impact of 87L settings on sensitivity and security, as well as grasping the relationship between the traditional percentage differential characteristic and the various 87L operating characteristics. x Having the ability to transfer settings between different 87L operating characteristics while keeping a similar balance between security and dependability. x Testing the 87L operating characteristics. These issues become particularly significant in applications involving more than two currents in the line protection zone (multiterminal lines) and lines terminated on dual-breaker buses. This paper is a tutorial on this relatively new protection topic and offers answers to the outlined challenges.
Źródło:
Present Problems of Power System Control; 2013, 3; s. 5-73
2084-2201
Pojawia się w:
Present Problems of Power System Control
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Identification of anisotropic criteria for stratified soil based on triaxial tests results
Autorzy:
Tankiewicz, M.
Kawa, M.
Powiązania:
https://bibliotekanauki.pl/articles/178919.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
strength
anisotropy
varved clay
Pariseau criterion
weakness plane
Opis:
The paper presents the identification methodology of anisotropic criteria based on triaxial test results. The considered material is varved clay – a sedimentary soil occurring in central Poland which is characterized by the so-called “layered microstructure”. The strength examination outcomes were identified by standard triaxial tests. The results include the estimated peak strength obtained for a wide range of orientations and confining pressures. Two models were chosen as potentially adequate for the description of the tested material, namely Pariseau and its conjunction with the Jaeger weakness plane. Material constants were obtained by fitting the model to the experimental results. The identification procedure is based on the least squares method. The optimal values of parameters are searched for between specified bounds by sequentially decreasing the distance between points and reducing the length of the searched range. For both considered models the optimal parameters have been obtained. The comparison of theoretical and experimental results as well as the assessment of the suitability of selected criteria for the specified range of confining pressures are presented.
Źródło:
Studia Geotechnica et Mechanica; 2017, 39, 3; 59-65
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A note on the differences between Drucker-Prager and Mohr-Coulomb shear strength criteria
Autorzy:
Wojciechowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/178873.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Mohr-Coulomb
Drucker-Prager
elasto-plasticity
shear strength
plane strain conditions
Opis:
A systematic approach to measure the differences between Mohr-Coulomb (MC) and Drucker-Prager (DP) shear strength criteria used commonly in soil and rock mechanics is presented. It is shown that the DP criterion generates a shear strength between 0.6 and 3 times the MC strength, for the same friction angle and cohesion parameters. The appropriate conditions for obtaining equal shear strengths are given. Moreover, some new DP failure surfaces are proposed which minimize the differences relative to the MC predictions. The equivalence of the DP and MC criteria under plane strain conditions is also examined.
Źródło:
Studia Geotechnica et Mechanica; 2018, 40, 3; 163-169
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Image encryption combining discrete fractional angular transform with Arnold transform in image bit planes
Autorzy:
Zhou, Z.
Yu, J.
Liao, Q.
Gong, L.
Powiązania:
https://bibliotekanauki.pl/articles/173704.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Arnold transform
bit plane
discrete fractional angular transform
image encryption algorithm
Opis:
A new image encryption algorithm by using a discrete fractional angular transform and Arnold transform in image bit planes is investigated. In the image encryption algorithm, the original image is encrypted by the Arnold transform in image bit planes firstly, and then the resulting image is encrypted by the discrete fractional angular transform further. The key of the image encryption algorithm includes the parameters of the Arnold transform and the order of the discrete fractional angular transform. It is shown that the proposed image encryption algorithm is of high security and strong enough to counteract some conventional image attack manners.
Źródło:
Optica Applicata; 2018, 48, 2; 225-236
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
X-ray microtomography (μCT) as a useful tool for visualization and interpretation of shear strength test results
Autorzy:
Stefaniuk, D.
Tankiewicz, M.
Stróżyk, J.
Powiązania:
https://bibliotekanauki.pl/articles/178870.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
X-ray microtomography
shear strength
shear plane
fine-grained soil
triaxial test
Opis:
The paper demonstrates the applicability of X-ray microtomography (μCT) to analysis of the results of shear strength examinations of clayey soils. The method of X-ray three-dimensional imaging offers new possibilities in soil testing. The work focuses on a non-destructive method of evaluation of specimen quality used in shear tests and mechanical behavior of soil. The paper presents the results of examination of 4 selected clayey soils. Specimens prepared for the triaxial test have been scanned using μCT before and after the triaxial compression tests. The shear strength parameters of the soils have been estimated. Changes in soil structure caused by compression and shear failure have been presented as visualizations of the samples tested. This allowed for improved interpretation and evaluation of soil strength parameters and recognition of pre-existing fissures and the exact mode of failure. Basic geometrical parameters have been determined for selected cross-sections of specimens after failure. The test results indicate the utility of the method applied in soil testing.
Źródło:
Studia Geotechnica et Mechanica; 2014, 36, 4; 47-55
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Water contact angle on corresponding surfaces of freshly fractured fluorite, calcite and mica
Autorzy:
Kowalczuk, P. B.
Akkaya, C.
Ergun, M.
Janicki, M.
Sahbaz, O.
Drzymala, J.
Powiązania:
https://bibliotekanauki.pl/articles/110595.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
contact angle
surface properties
cleaving plane
surface composition
corresponding halves
fluorite
calcite
mica
Opis:
Advancing and receding contact angles of water with corresponding surfaces of freshly fractured calcite, fluorite and mica were measured. The corresponding surfaces were obtained by mechanical splitting of a small lump of each mineral into two pieces. Theoretical considerations revealed that depending on the mineral cleaving plane, surfaces created by splitting into halves can be either identical or entirely different as far as their surface chemical composition is concerned. It was experimentally established that receding and advancing contact angles measured on the corresponding surfaces of fluorite, calcite and mica were identical for the sessile drop method. When the contact angle was measured by the captive bubble approach, there were small differences in the contact angles measured on the corresponding surfaces of fluorite. It was most probably due to surface irregularities and roughness, and therefore different times needed to rupture the liquid film between the bubble and solid surface.
Źródło:
Physicochemical Problems of Mineral Processing; 2017, 53, 1; 192-201
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Deep data analysis in gigabit passive optical networks
Autorzy:
Horvath, T.
Krkos, R.
Dubravec, L.
Powiązania:
https://bibliotekanauki.pl/articles/174869.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
GPONXpert
gigabit passive optical networks
GPON
signalling
user plane
frame structure
payload analysis
Opis:
This paper focuses on practical aspects of gigabit passive optical networks (GPON) diagnostics during deployment, for root-cause analysis and for research purposes. While GPON signalling analysis is already quite commonly used for diagnostics, the aim of this work is a holistic approach, including both signalling and user plane (payload) analysis. User plane analysis, especially if targeted at payload Ethernet, IP and transport layers, enables detection of additional group of problems that could limit or even prevent GPON internetworking and thus degrade the user perceived service quality. Integrated signalling and payload analysis is also interesting from the research point of view, leading to the ability to study equipment idiosyncrasies that would be hard to detect otherwise and it is also one of the enablers of equipment security verification. The mentioned theories were tested during a practical diagnostic session on a real GPON network deployment and this paper presents the findings.
Źródło:
Optica Applicata; 2017, 47, 1; 157-170
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characteristic parameters of soil failure criteria for plane strain conditions – experimental and semi-theoretical study
Autorzy:
Sławińska-Budzich, Justyna
Powiązania:
https://bibliotekanauki.pl/articles/1845147.pdf
Data publikacji:
2021
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
soil failure criteria
soil peak strength
plane strain conditions
true triaxial apparatus
plastic flow rule
Opis:
The paper concerns the characteristic parameters of the selected isotropic failure criteria, i.e. Mohr–Coulomb, Drucker–Prager, Matsuoka–Nakai and Lade–Duncan. The parameters are determined directly from the failure criteria and stress measurements or by semi-theoretical approach, assuming that the soil obeys the associated flow rule and using the plane strain condition. In the latter case, the parameters can be expressed as functions of the plane strain internal friction angle, which is determined from measurements. The principal stress tensor components, corresponding to the soil peak strength and necessary to obtain the failure criteria parameters, are measured in a series of true triaxial, plane strain tests, on coarse Skarpa sand samples of different initial relative density, subjected to various confining pressures.
Źródło:
Studia Geotechnica et Mechanica; 2021, 43, 3; 237-254
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-9 z 9

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