Informacja

Drogi użytkowniku, aplikacja do prawidłowego działania wymaga obsługi JavaScript. Proszę włącz obsługę JavaScript w Twojej przeglądarce.

Wyszukujesz frazę "Q." wg kryterium: Autor


Tytuł:
Optical solitons in birefringent fibers with parabolic law nonlinearity
Autorzy:
Zhou, Q.
Zhu, Q.
Biswas, A.
Powiązania:
https://bibliotekanauki.pl/articles/174318.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
solitons
parabolic law nonlinearity
birefringent fibers
Jacobian elliptic equation
Riccati
equation
Opis:
This paper studies the propagation of optical solitons through birefringent fibers with parabolic law nonlinearity. The Hamiltonian perturbations that are inter-modal dispersion, self-steepening, third-order dispersion and nonlinear dispersions are taken into account. Both, Riccati equation expansion method and Jacobian elliptic equation expansion method are used. Finally, analytical solutions that are Jacobian elliptic periodic traveling wave solutions, periodic solutions, unbounded solutions, singular solutions, bright and dark soliton solutions are obtained under several constraint conditions.
Źródło:
Optica Applicata; 2014, 44, 3; 399-409
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical properties of Nd:YbVO4 crystal
Autorzy:
Liu, F Q
Sun, S Q
Gao, C Y
Xu, J Q
Powiązania:
https://bibliotekanauki.pl/articles/174689.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Nd
YbVO4 crystal
Judd-Ofelt theory
energy transfer
Opis:
Optical characteristics of a new laser crystal Nd:YbVO4 were studied. The optical parameters of a-cut and c-cut Nd:YbVO4 crystals were calculated by the Judd–Ofelt theory. The absorption crosssection of a-cut Nd:YbVO4 crystal was 5.34×10–20 cm2 at 808 nm, while it was 4.20×10–18 cm2 of c-cut Nd:YbVO4 crystal. The properties of energy transfer between Nd and Yb ions in Nd:YbVO4 crystal were discussed. In the fluorescence spectra, a peak at 472 nm appeared, which resulted from the coupling interaction between two Yb ions.
Źródło:
Optica Applicata; 2015, 45, 1; 63-70
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lignite cleaning in NaCl solutions by the reverse flotation technique
Autorzy:
Zhang, H.
Liu, Q.
Powiązania:
https://bibliotekanauki.pl/articles/110516.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
lignite
reverse flotation
NaCl
kinetics
coal preparation
Opis:
A cleaning possibility of low (BD) and high ash content (IM) lignites in NaCl solutions using a reverse flotation technique was studied. Preliminary test results indicated that BD lignite cannot be cleaned effectively in the traditional manner because gangue was floated first rather than a combustible material. Further studies indicated that the lignite cleaning in NaCl solutions using the reverse flotation technique is possible. However, a large quantity of dodecyl amine hydrochloride (DAH) was required. A lower ash content in a concentrate can be obtained by addition of NaCl. A concentrate yield can be im-proved by addition of starch. Under the test conditions, for BD lignite with the ash content in the feed 15.19%, the ash content in the concentrate 11.44% and the concentrate yield 67.38% were obtained. Similarly, for IM lignite with the ash content in the feed 57.40%, the ash content in the concentrate 32.90% and the concentrate yield 25.08% were obtained. The flotation rate constant k and maximum ash recovery ε∞ significantly increased with the NaCl concentration.
Źródło:
Physicochemical Problems of Mineral Processing; 2015, 51, 2; 695-706
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental study on electrokinetic of kaolinite particles in aqueous suspensions
Autorzy:
Min, F.
Zhao, Q.
Liu, L.
Powiązania:
https://bibliotekanauki.pl/articles/110918.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
kaolinite
zeta potential
pH
immersion time
electrophoresis
Opis:
Influence of aqueous phase properties and process parameters on kaolinite particle zeta potential was quantified by electrophoresis experiments. The results indicated that pH strongly altered the zeta potential of kaolinite and it decreases at the beginning and then increases in the range of pH = 2–13. The activity of different cations changes the zeta potential and has the following tendency of Al3+ > Ca2+ > Mg2+ > Na+ and the zeta potential increases due to heterocoagulation of different mineral particles in suspension. It was found that the zeta potential of kaolinite particles increases after the suspension was stirred and decreases at the beginning, and then increases with soaking time. The FTIR results showed that the zeta potential takes into account ion adsorption and the change of Si–O, Al–O and Al–OH groups on the surface of the kaolinite particles.
Źródło:
Physicochemical Problems of Mineral Processing; 2013, 49, 2; 659-672
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A known-plaintext attack on iterative random phase encoding in fractional Fourier domains
Autorzy:
Yin, F.
He, Q.
Liu, Z.
Powiązania:
https://bibliotekanauki.pl/articles/174043.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
image encryption
phase encoding
known-plaintext attack
Opis:
Known-plaintext attack is considered for decrypting the image generated by iterative random phase encoding in fractional Fourier transform domains. The double random phase encoding in Fourier domains is introduced to design the known-plaintext attack procedure. The decryption test is explored without both fractional order and these random phase masks. Some numerical simulations are made to demonstrate the validity of the known-plaintext attack.
Źródło:
Optica Applicata; 2017, 47, 1; 131-139
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on self-repairing and non-diffraction of Airy beams in slant atmospheric turbulence
Autorzy:
Li, Y.-Q.
Wang, L.-G.
Powiązania:
https://bibliotekanauki.pl/articles/174867.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
atmospheric turbulence
Airy beam
self-repairing
non-diffraction
numerical simulation
Opis:
The Airy beams propagation in atmospheric turbulence along a slant path was simulated numerically, based on the split-step Fourier method. Also, the self-repairing and non-diffraction characteristics of Airy beams were investigated and compared with beams propagation on a horizontal path. The effects of parameters including zenith angle, propagation distance, radii of Gaussian aperture and turbulence intensity on the two characteristics of beams were revealed. Additionally, the two characteristics of the Airy beam were compared with those of a Bessel–Gauss beam. The results showed that the two beams obscured by Gaussian apertures can be repaired after propagating some distance along a slant path. However, the non-diffraction characteristic of an Airy beam was stronger than that of a Bessel–Gauss beam and the amplitude attenuation rate of the Bessel–Gauss beam was greater than that of the Airy beam in the process of self-repairing. Results obtained can provide a theoretical basis for an outdoor experiment as well as theoretical guidance for various practical applications including laser communications, laser warning systems, and remote sensing.
Źródło:
Optica Applicata; 2018, 48, 3; 435-447
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Preparation and cytological study of collagen/nano-hydroxyapatite/graphene oxide composites
Autorzy:
Wang, J.
Wang, Y.
Liu, D.
Yang, Q.
Huang, C.
Yang, C.
Zhang, Q.
Powiązania:
https://bibliotekanauki.pl/articles/307450.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
nanohydroksyapatyt
tlenek grafitu
mineralizacja
kolagen
nano-hydroxyapatite
graphene oxide
biomimetic mineralization
collagen
Opis:
Biomimetic mineralized composite scaffolds are widely used as natural bone substitute materials in tissue engineering by inducing and assembling bonelike apatite. In this study, the single lamellar structure of graphene oxide (GO) powder was prepared via an improved Hummers’ method. Methods: To better mimic natural bone, the collagen (COL)/Nano-hydroxyapatite (nHA)/graphene oxide (GO) composite material was prepared by simulated body fluid (SBF) method using COL/GO as a matrix template. Hydroxyapatite (HA) with calcium ion deficiency was achieved via biomimetic mineralization, and it had properties closer to those of natural bone than pure HA has. Results: The mineralized COL/nHA/GO composites exhibited loose porous structures, and the connectivity of the holes was good and thus beneficial to the exchange of nutrients and excreted metabolites. Conculsions: Antibacterial and MTT experiment confirmed that the COL/nHA/GO composite material had excellent antibacterial property and biocompatibility. Hence, these results strongly suggested the mineralized COL/nHA/GO composite is a good candidate biomaterial to be applied in bone tissue engineering.
Źródło:
Acta of Bioengineering and Biomechanics; 2018, 20, 4; 65-74
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on relationship between carbon dioxide emissions, imports, exports, and population in China
Autorzy:
Jin, Q.-Y.
Zhang, J.
Gao, Y.-Q.
Su, X.
Fu, Y.-S.
Powiązania:
https://bibliotekanauki.pl/articles/207318.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
population statistics
carbon dioxide
global warming
carbon dioxide emissions
total carbon
statystyki ludności
dwutlenek węgla
globalne ocieplenie
emisja dwutlenku węgla
węgiel całkowity
Opis:
Empirical relationships between carbon dioxide emission, imports, exports, and population have been investigated. An empirical model with carbon dioxide emissions, structure and scale of import and exports, populations was built Using ridge regression analysis and observed data from 1985 to 2006 in China, we examined the relationship between each part of carbon dioxide emission and corresponding coefficients, including GIV (gross imports value), GXV (gross exports value), and P (populations). The results have shown that the increasing trend in TCOE (total carbon dioxide emissions) was determined by the exports, while its standard level is determined by population. Increasing the imports may reduce TCOE. Considering working to expand economy, the best ways for China to reduce TCOE are to introduce advanced technology and take actions to guarantee strict execution of cut-emission policy. Although the increasing imports also can reduce TCOE, it is not reasonable for the global cut-emission policy. To control population is not applicable as the immense population base, so government's publicity for low-carbon live is a necessary and feasible way to reduce carbon dioxide emission.
Źródło:
Environment Protection Engineering; 2014, 40, 2; 75-85
0324-8828
Pojawia się w:
Environment Protection Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of unstable elements with different hardness on lower limb loading
Autorzy:
Li, F.
Mei, Q.
Gu, Y.
Powiązania:
https://bibliotekanauki.pl/articles/307265.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
ciśnienie podeszwowe
stopa
staw kolanowy
twardość
knee adduction moment
plantar pressure
unstable elements
hardness
foot
Opis:
Purpose: Osteoarthritis of the knee is one of the most common diseases. For this chronic disease, modified footwear structure can effectively prevent and relieve disease of the knee. The aim of this study was to explore the effects of shoe surface elastic modulus on external knee adduction moment and ground reaction force and foot loading characteristics. Methods: Sixteen healthy female volunteers were recruited, and each subject performed five walking trials under two shoes condition. The lower limb loading data was collected using force platform and in-sole pressure measurement system. Results: The results showed that the external knee adduction moment was decreased in all stance phase when wearing SS (unstable shoes with soft unstable elements), compared with HS (unstable shoes with hard unstable elements). The ground reaction force showed no obvious change under two shoes condition. Additionally, compared with HS, plantar pressure transferred from medial foot to lateral foot when wearing SS. Along with changes of contact areas, average pressure and impulse had also presented this tendency. Conclusions: These results can provide some scientific evidence and suggestions for footwear companies, and for the foot plantar medial injury disease has also certain applicability.
Źródło:
Acta of Bioengineering and Biomechanics; 2015, 17, 2; 85-92
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oil-assisted flotation of fine hematite using sodium oleate or hydroxamic acids as a collector
Autorzy:
Li, H.
Liu, M.
Liu, Q.
Powiązania:
https://bibliotekanauki.pl/articles/109749.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
hematite
sodium oleate
kerosene
Batch Flotation
Octyl hydroxamic acid
Oleoyl hydroxamic acid
Opis:
Micro-flotation and batch flotation tests were carried out on fine (-20 µm) hematite to investigate the influences of non-polar oil when sodium oleate, octyl hydroxamic acid, or oleoyl hydroxamic acid was used as a collector. Both micro-flotation and batch flotation tests were performed using single hematite mineral and/or artificial mixed minerals (hematite:quartz = 1:1), and kerosene was utilized as the neutral oil. The experimental results showed that the addition of a kerosene emulsion benefited hematite recovery in the micro-flotation tests where a froth layer did not exist. In the batch flotation where a froth layer existed, kerosene behaved differently when used in conjunction with the three collectors. Kerosene helped improve the batch flotation when sodium oleate or oleoyl hydroxamic acid was used as a collector. However, it reduced concentrate weight yield, grade and recovery to a noticeable extent when octyl hydroxamic acid was used as a collector, especially at low dosages. In addition, single hematite batch flotation kinetics tests coupled with water recovery measurement were carried out to study the role of kerosene at different collector dosages. It was observed that water drainage and the resulting froth destabilization by kerosene was dominant at low collector dosages, especially in the flotation using octyl hydroxamic acid. At higher collector dosages, the water drainage and froth destabilization effect by kerosene was possibly counter-balanced by the higher hematite surface hydrophobicity and bubble surface tension gradient, which led to more stable froth layer.
Źródło:
Physicochemical Problems of Mineral Processing; 2018, 54, 4; 1130-1145
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Removal of clofibric acid and diclofenac during anaerobic digestion of sewage sludge
Autorzy:
Zhou, H.
Zhang, Q.
Zhang, Q
Ma, L.
Tu, B.
Li, H.
Zhou, Y.
Powiązania:
https://bibliotekanauki.pl/articles/207894.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
fermentacja beztlenowa
osady ściekowe
farmaceutyki
kwas klofibrowy
diklofenak
anaerobic digestion
sewage sludge
pharmaceuticals
clofibric acid
diclofenac
Opis:
Removal of two acidic pharmaceuticals, clofibric acid and diclofenac, present in sewage sludge using two kinds of anaerobic digestions was investigated. The effective isolation and purification pretreatment to extract the target compounds from the sewage sludge samples was firstly established, followed by gas chromatography-mass spectrometry (GC-MS) analysis to identify and quantify them. Under mesophilic conditions, the removal efficiencies for clofibric acid and diclofenac with the initial concentrations of 5 μg /dm3 were up to 95% and 97%. After thermophilic anaerobic digestion, the removal efficiency could be increased to 99.3% for clofibric acid, however, it did not increase for diclofenac. In general, anaerobic digestion could effectively remove the target compounds from the sewage sludge (all above 90%).
Źródło:
Environment Protection Engineering; 2013, 39, 4; 63-77
0324-8828
Pojawia się w:
Environment Protection Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pre-concentration of graphite and LiCoO2 in spent lithium-ion batteries using enhanced gravity concentrator
Autorzy:
Zhu, X,-N.
Tao, Y.-J.
He, Y.-Q.
Zhang, Y.
Sun, Q.-X.
Powiązania:
https://bibliotekanauki.pl/articles/109609.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
spent lithium-ion batteries
electrode material
resource utilization
pre-concentration
enhanced gravity concentrator
Opis:
The pre-concentration of electrode material of spent lithium-ion battery has great significance on the resource utilization and environmental protection. The feasibility of separation of graphite and LiCoO2 based on density difference using the enhanced gravity concentrator was verified in this paper. Combustion characteristics of LiCoO2 and graphite were used to propose a simple evaluation index of separation efficiency. Separation tests were carried out to specify the influence of operating parameters on the separation efficiency. Moreover, the effect of particle size on the separation performance was studied. Combustion characteristics results showed that mass loss of graphite was much greater than that of LiCoO2. Thus, mass loss were used to evaluate the purity of product. Effective separation of graphite and LiCoO2 was achieved by the enhanced centrifugal separator. Separation results showed that increasing centrifugal force decreased the overflow yield and increased the graphite content of the overflow stream. In addition, yield of overflow grew an increase in fluidization water pressure, while the purity of graphite in overflow decreased. The effect of particle size on the separation efficiency was also significant, the separation efficiency decreased with the decreasing of particle size.
Źródło:
Physicochemical Problems of Mineral Processing; 2018, 54, 2; 293-299
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis, structure and performance of calcium silicate ion exchangers from recycled container glass
Autorzy:
Coleman, N. J.
Li, Q.
Raza, A.
Powiązania:
https://bibliotekanauki.pl/articles/109960.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
tobermorite
sorbent
hydrothermal synthesis
cullet
recycling
ion exchange
Opis:
Numerous technical, economic and societal factors limit the recycling of waste soda-lime-silica glass back into the primary production process and accordingly alternative applications for this material are sought. This study demonstrates that waste soda-lime-silica container glass is a suitable feedstock material for the production of tobermorite, a calcium silicate cation exchanger. Tobermorites were synthesised at 100 °C from stoichiometric mixtures of container glass and lime under alkaline hydrothermal conditions. Increasing concentrations of sodium hydroxide (between 1.0 M and 4.0 M) in the reaction mixture promoted the formation and crystallisation of tobermorite, and also resulted in greater fragmentation of the silicate chains along the b-axis direction. The maximum removal capacities of these tobermorite specimens for Cd2+ (441 mg g-1) and Zn2+ (122 mg g-1) compared well with those of other waste-derived sorbents. Superior Cd2+- and Zn2+-uptake capacities and kinetics were observed for the least crystalline tobermorite specimen, indicating that stacking defects facilitate the transport and exchange of cations within the lattice.
Źródło:
Physicochemical Problems of Mineral Processing; 2014, 50, 1; 5-16
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigating biomechanical function of toes through external manipulation integrating analysis
Autorzy:
Mei, Q.
Fernandes, J.
Hume, P.
Gu, Y.
Powiązania:
https://bibliotekanauki.pl/articles/306943.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
palec nogi
uchwyt
przyczepność
uszkodzenia
toes
grip
windlass mechanism
metatarsal injury
Opis:
Purpose: This study was aimed to investigate the function of toes while running through comparing bound toes by external-manipulation with natural separate toes by evaluating kinematics and plantar pressure analysis. Methods: Seven habitually barefoot male runners participated in the running test under toes binding and non-binding conditions, and Vicon and Novel insole plantar pressure measurement were conducted synchronously to collect kinematics and foot loading. Results: Ankle kinematics showed larger non-significant range of motion in the frontal plane while running with toes non-binding.The medial forefoot had a smaller force time integral, and with hallux had a larger force time integral than those of running with toes binding, with significance level p < 0.05. Conclusions: While no significance existed between bound and non-bound toes in kinematics, the medial forefoot had a smaller foot impulse and the hallux had a larger foot impulse for those with non-binding feet. This suggests that other functions such as the active gripping action of toes might be important for the efficiency of the foot windlass mechanism (the plantar fascia support), which would be beneficial for running performance improvement and foot injury prevention.
Źródło:
Acta of Bioengineering and Biomechanics; 2016, 18, 1; 97-102
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
How foot morphology changes influence shoe comfort and plantar pressure before and after long distance running?
Autorzy:
Mey, Q.
Gu, Y.
Sun, D.
Fernandez, J.
Powiązania:
https://bibliotekanauki.pl/articles/306388.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
ciśnienie podeszwowe
obuwie
kształt stopy
komfort
bieg długodynstansowy
foot shape
plantar pressure
footwear
comfort
long distance running
Opis:
Prolonged running has been popularized globally in recent decades. This study was aimed to reveal information about foot morphology, shoe comfort and plantar loading among recreational heel-strike runners. Methods: Twenty-six runners participated in foot morphology, perceived scores and peak pressure tests after 10- and 20-km track running. The foot morphology was measured using a 3D foot scanner, perceived scores were recorded using a visual analogue scale and plantar pressure was measured via insole plantar pressure measurement system. The statistical significance level was set at 0.05. Results: The heel midsole materials properties were measured before and after 20 km. Significant changes were observed in ball width and girth, arch height and foot volume. The perceived scores showed significance in overall, forefoot and heel comfort, arch support and forefoot width. Peak pressure to the heel, medial mid-foot and metatarsal greatly increased. The first metatarsal showed consecutive increase from static to 10 km, and 20 km, while big-toe showed a decrease. Conclusions: The morphology variations and forefoot loading concentration may lead to discomfort and possibly imply dermatological problems and metatarsal bone stress, particularly on the first metatarsal. Combining changes of heel midsole property, knowledge of foot shape, shoe perception and plantar pressure is of great value for recreational long-distance running shoes design and materials selection.
Źródło:
Acta of Bioengineering and Biomechanics; 2018, 20, 2; 179-186
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł

Ta witryna wykorzystuje pliki cookies do przechowywania informacji na Twoim komputerze. Pliki cookies stosujemy w celu świadczenia usług na najwyższym poziomie, w tym w sposób dostosowany do indywidualnych potrzeb. Korzystanie z witryny bez zmiany ustawień dotyczących cookies oznacza, że będą one zamieszczane w Twoim komputerze. W każdym momencie możesz dokonać zmiany ustawień dotyczących cookies