Informacja

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

English (EN)·Polski (PL)·Yкраїнський (UK)
Przejdź do strony domowej biblioteki Centralna Biblioteka Wojskowa Link otwiera się w nowym oknie Logo biblioteki Prolib Integro - strona głównaCentralna Biblioteka Wojskowa

Wyszukujesz frazę "Xu, Y." wg kryterium: Autor

  Lista filtrów
Wyrównaj
Wyświetlanie 1-15 z 89
Tytuł:
Intervalley Transfer of Electrons in ZnS-Type Thin Film Electroluminescent Devices
Autorzy:
Zhao, H.
Wang, Y.
Xu, Z.
Xu, X.
Powiązania:
https://bibliotekanauki.pl/articles/2011094.pdf
Data publikacji:
1999-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.-i
78.60.-b
Opis:
Based on the calculation about intervalley scattering rates in ZnS, the intervalley transfer process in ZnS-type thin film electroluminescent devices is investigated through the Monte Carlo simulation. The transient time of intervalley transfer is about 0.2-0.3 ps, it coincides with that of electron average energy. Intervalley distribution shifts to high valleys as the electric field increased. The electron kinetic energy distributions in different valleys are also gained. We propose that high valleys could store energies, which could prolong the decay of the electron average energy as the field was removed. These results could be used as the basic data on the study of electroluminescent process and the citation of valley parameters in analytic models should be carefully considered.
Źródło:
Acta Physica Polonica A; 1999, 96, 3-4; 475-482
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analytical Band Model in Monte Carlo Simulation of Electric Transport in ZnS Thin Film Electroluminescent Devices
Autorzy:
Zhao, H.
Wang, Y.
Xu, X.
Powiązania:
https://bibliotekanauki.pl/articles/2014087.pdf
Data publikacji:
2000-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.60.-b
72.20.-i
Opis:
In this paper, an analytical band model is introduced in Monte Carlo simulation of electric transport process in thin film electroluminescent devices. The band structure of ZnS calculated from the empirical pseudopotential method is fitted by using polynomials. The density of states and scattering rates are also calculated from these polynomials. Based on these results, the electric transport process in ZnS-type thin film electroluminescent devices is simulated through the Monte Carlo method. By comparison with others, this model is as fast as the nonparabolic model and as accurate as the full band model. Furthermore, the influence of the band model on the simulation results is also investigated. We show that the dispersion relation and density of states are all important in the simulation.
Źródło:
Acta Physica Polonica A; 2000, 98, 1-2; 123-130
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Practical issues in frequency disturbance recorder design for wide-area monitoring
Autorzy:
Xu, Ch.
Zhong, Z.
Centeno, V.
Conners, R.
Liu, Y.
Powiązania:
https://bibliotekanauki.pl/articles/262637.pdf
Data publikacji:
2005
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
power system
wide-area monitoring
phasor analysis
frequency tracking
Opis:
To maintain power system operation in a balanced and stable condition, the frequency deviation and the rate of frequency change information are highly desired in monitoring and protection applications of the power grid. How to obtain frequency information more accurately and efficiently has been the topic discussion for decades. PMUs (Phaser Measurement Unit) are the most widely-used devices for measuring phase angle differences and they also provide very accurate frequency information. However, the high installation cost of PMUs limits their applications for wide area control and stability analysis of power system. Thanks to commercial GPS receivers and the fast developments in Ethernet networks, an affordable wide area, quasi real-time, GPS synchronized frequency measurement is now possible. This paper introduces a portable networked Frequency Disturbance Recorder (FDR) device, which can be used at any 110V wall outlet and transmit measured frequency data remotely via the Ethernet. The practical issues and challenges of the device design and implementation are analyzed and discussed. Based on these low cost FDRs, a US-wide Frequency Network (FNET) has been implemented at Virginia Tech and some power system monitoring applications are being developed by taking fully advantage of the FDRs.
Źródło:
Electrical Power Quality and Utilisation. Journal; 2005, 11, 1; 69-76
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Zastosowania nadprzewodników wysokotemperaturowych do ograniczania prądu
Applications of HTc superconductors for current limitation
Autorzy:
Sosnowski, J.
Horyń, R.
Bukowska, E.
Koblischka, M.R.
Xu, Y.
Boreta, B.
Powiązania:
https://bibliotekanauki.pl/articles/159126.pdf
Data publikacji:
2006
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Elektrotechniki
Tematy:
nadprzewodnictwo wysokotemperaturowe
ograniczniki prądu
ekran nadprzewodnikowy
Opis:
W pracy przedyskutowano zastosowania nadprzewodników wysokotemperaturowych w ogranicznikach prądowych. Przedstawiono konstrukcję modelu rezystywnego, nadprzewodnikowego ogranicznika prądu zwarcia, przeznaczonego do ograniczania prądu o natężeniu rzędu kilkudziesięciu amperów oraz przygotowania do konstrukcji indukcyjnego ogranicznika. Przedstawiono model matematyczny działania ogranicznika. W rezystywnej konstrukcji wykorzystano taśmy nadprzewodnikowe z nadprzewodnika typu Bi:2223 pracujące w otoczeniu ciekłego azotu, podczas gdy przewiduje się wykonać prototyp indukcyjnego ogranicznika w oparciu o ekrany nadprzewodnikowe również z nadprzewodnika opartego na bizmucie. Przedstawiono rezultaty prac technologicznych nad uzyskaniem tych ekranów i analizę dyfraktograficzną otrzymanych proszków bizmutowych typu Bi:2212, spieczonych z polskich surowców. Jakkolwiek uzyskano jednorodny rentgenograficznie materiał typu Bi:2212, to jednak przejście nadprzewodzące zmierzone metodami magnetycznymi było dość rozmyte. Wymaga to kontynuacji prac nad uzyskaniem materiałów o odpowiednich parametrach nadprzewodnikowych.
Applications of HTc superconductors in the fault current limiters has been discussed. A model of the constructed resistive type superconducting fault current limiter has been presented, which is devoted to current limitation at the level of several dozen of amperes, as well as the preparation for construction of the inductive type superconducting current limiter. The mathematical model of limiters has been discussed. In the resistive model the HTc superconducting Bi:2223 tapes have been used, working in liquid nitrogen environment. It is expected too built a model of inductive fault current limiter in which the active element would be the superconducting shields. Results of the technological work on the design of these superconducting shields, using the commercially available powders are presented. The diffractographic analysis of prepared materials was presented too. Although a homogeneous (from the crystallographic point of view) material of the type Bi:2212 was obtained, the superconducting transition curves were relatively wide. Continuation of the work on the superconducting materials technology process is recessary.
Źródło:
Prace Instytutu Elektrotechniki; 2006, 226; 125-147
0032-6216
Pojawia się w:
Prace Instytutu Elektrotechniki
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A note on the p-domination number of trees
Autorzy:
Lu, Y.
Hou, X.
Xu, J.-M.
Powiązania:
https://bibliotekanauki.pl/articles/255183.pdf
Data publikacji:
2009
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
p-domination number
trees
Opis:
Let p be a positive integer and G = (V (G), E(G)) a graph. A p-dominating set of G is a subset S of V (G) such that every vertex not in S is dominated by at least p vertices in S. The p-domination number ϒp(G) is the minimum cardinality among the p-dominating sets of G. Let T be a tree with order n ≥ 2 and p ≥ 2 a positive integer. A vertex of V (T) is a p-leaf if it has degree at most p - 1, while a p-support vertex is a vertex of degree at least p adjacent to a p-leaf. In this note, we show that ϒp(T) ≥ (n + /Lp(T)/ - /Sp(T)/)/2, where Lp(T) and Sp(T) are the sets of p-leaves and p-support vertices of T, respectively. Moreover, we characterize all trees attaining this lower bound.
Źródło:
Opuscula Mathematica; 2009, 29, 2; 157-164
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Catalytic performances of cross-linking humic acids supported Pd/Ni bimetallic catalyst for heck reaction
Autorzy:
Xu, Q.
Zhang, L.
Shi, W.
Cui, Y.
Powiązania:
https://bibliotekanauki.pl/articles/778727.pdf
Data publikacji:
2009
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
kwas humusowy
epichlorohydryna
katalizator bimetaliczny Pd/Ni
katalizator nośnikowy
reakcja Hecka
cross-linking humic acid
epichlorohydrin
Pd/Ni bimetallic catalyst
supported catalyst
Heck reaction
Opis:
The cross-linking humic acids (CL-HAs), epichlorohydrin as the cross-linking reagent and the supported Pd/Ni bimetallic catalysts (CL-HAs-Pd/Ni) were prepared and characterized by IR, AAS, XPS, TEM. The effects of reaction time, temperature, base, solvent and the amount of catalyst on the properties of the catalyst were studied. These catalysts could catalyze the Heck reaction of aryl halides and substituted aryl halides with acrylic acids or styrene successfully; the yields were all above 95%.
Źródło:
Polish Journal of Chemical Technology; 2009, 11, 3; 22-26
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhancing CNC Manufacturing Interoperability with Step-NC
Autorzy:
Rauch, M.
Laguionie, R.
Hascoet, J.-Y.
Xu, X.
Powiązania:
https://bibliotekanauki.pl/articles/971256.pdf
Data publikacji:
2009
Wydawca:
Wrocławska Rada Federacji Stowarzyszeń Naukowo-Technicznych
Tematy:
STEP-NC
advanced CNC
programming CAD/CAM/CNC data interoperability
Opis:
Despite substantial improvements CNC manufacturing is still based on dated practices and habits. This is mostly due to the use of ISO 6983 standard (G-codes) combined with vendor specific formats to exchange CAD/CAM/ CNC information. The manufacturing sector is consequently made of a collection of disconnected elements that are difficult to make communicate together. On the contrary STEP-NC approach offers many opportunities to overtake the current situation and rethink CAD/CAM/CNC numerical chains. However, the actual integration of STEP-NC in industrial concerns is quite limited. It is essential to couple this innovative approach with existing equipments. This paper shows how STEP-NC can be an efficient way to reconcile today's interoperability and efficiency demands by introducing the association of two manufacturing platforms: SPAIM, developed at IRCCyN (France), and which controls current industrial machine tools directly from STEP-NC files and IIMP from the University of Auckland (New Zealand), which realizes data portability between heterogeneous proprietary formats, process interoperability. As a result, both approaches lead to improved supervision and integration of the machining systems.
Źródło:
Journal of Machine Engineering; 2009, 9, 4; 26-38
1895-7595
2391-8071
Pojawia się w:
Journal of Machine Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Lifting Wavelet Domain Audio Watermarking Algorithm Based on the Statistical Characteristics of Sub-Band Coefficients
Autorzy:
Tao, Z.
Zhao, H.
Wu, J.
Gu, J.
Xu, Y.
Wu, D.
Powiązania:
https://bibliotekanauki.pl/articles/177956.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
audio watermarking
lifting wavelet transform
statistical characteristics
sub-band coefficients
Opis:
In this paper, a new lifting wavelet domain audio watermarking algorithm based on the statistical characteristics of sub-band coefficients is proposed. First of all, an original audio signal was segmented and each segment was divided into two sections. Then, the Barker code was used for synchronization, the LWT (lifting wavelet transform) was performed on each section, a synchronization code and a watermark were embedded into the first section and the second section, respectively, by modifying the statistical average value of the sub-band coefficients. The embed strength was determined adaptively according to the auditory masking property. Experiments show that the embedded watermark has better robustness against common signal processing attacks than present algorithms based on LWT and can resist random cropping in particular.
Źródło:
Archives of Acoustics; 2010, 35, 4; 481-491
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new troodontid theropod from the Late Cretaceous of central China, and the radiation of Asian troodontids
Autorzy:
Lu, J
Xu, L.
Liu, Y.
Zhang, X.
Jia, S.
Ji, Q.
Powiązania:
https://bibliotekanauki.pl/articles/20912.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
new theropod
Late Cretaceous
Central China
Asian troodontid
troodontid
Theropoda
Troodontidae
Xixiasaurus
Cretaceous
Henan province
China
paleontology
Opis:
A new troodontid dinosaur, Xixiasaurus henanensis gen. et sp. nov., from the Upper Cretaceous Majiacun Formation of the Xixia Basin, Henan Province, is erected, based on a partial skull. It is characterized by bearing 22 maxillary teeth, a distinct opening on the lateral surface of the base of nasal process of the premaxilla, the rostral end of the upper jaw forming a tapered U−shape, and the mandibular symphyseal region slightly inflected medially. Xixiasaurus is most closely related to the Mongolian Byronosaurus among troodontids. Byronosaurus, Urbacodon, and Xixiasaurus may form a new clade, suggesting an endemic radiation of troodontids across Asia, including multiple taxa without dental serrations. The discovery of Xixiasaurus in the Xixia Basin may imply that the Xixiasaurus−bearing Majiacun Formation is Campanian in age.
Źródło:
Acta Palaeontologica Polonica; 2010, 55, 3; 381-388
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infuence of Iron Ion on Thermal Behavior of Ammonium Nitrate and Emulsion Explosives
Autorzy:
Xu, Z.
Liu, D.
Hu, Y.
Ye, Z.
Wei, Y.
Powiązania:
https://bibliotekanauki.pl/articles/357932.pdf
Data publikacji:
2010
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
Accelerating Rate Calorimeter (ARC)
ammonium nitrate
critical temperature
emulsion explosives
thermal stability
Opis:
The infuence of ferric nitrate on the thermal stability of ammonium nitrate and emulsion matrix were used to study with Accelerating Rate Calorimeter (ARC) and constant temperature thermal decomposition experiment in this paper. It is shown that ferric nitrate has signifcant catalytic property to the ammonium nitrate and emulsion matrix, which decrease the initial decomposition temperature of ammonium nitrate by 60.16 C and emulsion matrix by 30.33 C. The results of the infuence of ferric nitrate on catalysis of ammonium nitrate using ARC and constant temperature thermal decomposition experiment are the same. The most probable mechanism function, activation energy and the preexponential factor of ammonium nitrate with ferric nitrate were determined to be f(α) = 1-α, E = 195.41 kJ/mol, A = 2.08×1019 s-1. The kinetics of ammonium nitrate decomposition can be used to calculate the critical temperatures for ammonium nitrate decomposition with and without the presence of ferric nitrate, based on the Frank-Kamenetskii model of thermal explosion. Furthermore, as the iron-plate experiment shows, ferric nitrate can signifcantly reduce the critical temperature of emulsion matrix decomposition. Once the ferric nitrate interfuses in the ammonium nitrate and emulsion matrix, the thermal stability of ammonium nitrate and emulsion matrix is decreasing.
Źródło:
Central European Journal of Energetic Materials; 2010, 7, 1; 77-93
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on Hybrid Filtering Solution for Marine Electric Network
Autorzy:
Xu, X - Y.
Mindykowski, J.
Chen, C. L. P.
Powiązania:
https://bibliotekanauki.pl/articles/259582.pdf
Data publikacji:
2010
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
electrical engineering
marine vehicle power systems
power system harmonics
power system measurements
quality control
Opis:
This paper presents a Hybrid APF/PFC/PPF Circuit (active power filtering and power factor correction circuit aided by shunt passive filter) for harmonic suppression and power factor correction in a marine electric network. By employing the proposed hybrid circuit, marine electric power network voltage and current can be maintained as being sinusoidal, and the power factor is close to 1. The effectiveness of the proposed method that is applied to a marine electric network is demonstrated through a simulation experiment. The results show that the expected performances are achieved.
Źródło:
Polish Maritime Research; 2010, 2; 72-78
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
HGRP: hybrid grid routing protocol for heterogeneous hierarchical wireless networks
Autorzy:
Shen, Y.
Pei, Q.
Xu, Q.
Xi, N.
Ma, J.
Powiązania:
https://bibliotekanauki.pl/articles/206219.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
hybrid grid routing protocol
mobile ad hoc networks
heterogeneous wireless networks
ad hoc on-demand distance vector routing protocol
zone routing protocol
Opis:
The heterogeneous mobile terminals coexist in the next generation wireless networks. The most common routing schemes for mobile ad hoc networks are designed for homogeneous wireless networks. The heterogeneous wireless network routing protocols are needed urgently in many important applications. This paper improves the routing scheme utilizing different capability of terminals and the Hybrid Grid Routing Protocol (HGRP) is proposed. The network is organized in the grid form, that is, the network deployment area is divided into square cells according to the location. Each cell contains one backbone node and several ordinary nodes. This proposed protocol consists of four parts: grid construction, local routing, global routing, and routing correction. Analysis and simulation results indicate that the proposed protocol has the advantages of lower routing cost, lower energy consumption, smaller delay and higher throughput, compared to AODV and ZRP.
Źródło:
Control and Cybernetics; 2012, 41, 2; 353-371
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Review of the Photodecomposition of Some Important Energetic Materials
Autorzy:
Sun, Y.
Shu, Y.
Xu, T.
Shui, M.
Zhao, Z.
Gu, Y.
Wang, X.
Powiązania:
https://bibliotekanauki.pl/articles/358397.pdf
Data publikacji:
2012
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
photodecomposition mechanisms
energetic materials
Opis:
The photodecomposition mechanisms of energetic materials vary with molecular structure, photodissociation wavelength, the phase of the material, experimental pressure and temperature etc. In this paper, the significant progress on photodecomposition studies of some important energetic materials achieved in recent years is introduced in detail, including nitromethane, DMNA (dimethylnitramine), TATB (1,3,5-triamino-2,4,6-trinitrobenzene), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), HMX (1,3,5,7-tetranitro-1,3,5,7- tetrazacycloctane) and CL-20 (2,4,6,8,10,12-hexanitrohexaazaisowurtzitane). The difficulties and prospects of photodecomposition research of energetic materials are also indicated.
Źródło:
Central European Journal of Energetic Materials; 2012, 9, 4; 411-423
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis of the cross-linked humic acid supporting palladium catalyst and its catalytic properties for Heck reaction
Autorzy:
Xu, Q.
Shi, W.
Cui, Y.
Powiązania:
https://bibliotekanauki.pl/articles/779729.pdf
Data publikacji:
2012
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
kwasy humusowe
epichlorohydryna
reakcja Hecka
humic acid
epichlorohydrin
supporting palladium catalyst
Heck reaction
Opis:
Cross-linked humic acid supporting palladium (CL-HA-Pd) catalyst was prepared readily and characterized by infrared analysis (IR) and thermogravimetric analysis (TG). The catalyst could catalyze the Heck reaction of aryl halide or substituted aryl halide with vinyl compounds in N2 atmosphere; the yields were above 95%. The catalyst could be recovered and reused 7 times with the Heck reaction of iodobenzene with acrylic acid, and the yield was above 75.6%. The results showed that the catalyst had high catalytic activity even at low temperature of 62°C or with a small amount of the catalyst.
Źródło:
Polish Journal of Chemical Technology; 2012, 14, 2; 75-79
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A practical application of kernel-based fuzzy discriminant analysis
Autorzy:
Gao, J. Q.
Fan, L. Y.
Li, L.
Xu, L. Z.
Powiązania:
https://bibliotekanauki.pl/articles/908344.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
analiza dyskryminacyjna
algorytm najbliższego sąsiada
SVD
kernel fuzzy discriminant analysis
fuzzy k-nearest neighbor
QR decomposition
singular value decomposition (SVD)
fuzzy membership matrix
t-test
Opis:
A novel method for feature extraction and recognition called Kernel Fuzzy Discriminant Analysis (KFDA) is proposed in this paper to deal with recognition problems, e.g., for images. The KFDA method is obtained by combining the advantages of fuzzy methods and a kernel trick. Based on the orthogonal-triangular decomposition of a matrix and Singular Value Decomposition (SVD), two different variants, KFDA/QR and KFDA/SVD, of KFDA are obtained. In the proposed method, the membership degree is incorporated into the definition of between-class and within-class scatter matrices to get fuzzy between-class and within-class scatter matrices. The membership degree is obtained by combining the measures of features of samples data. In addition, the effects of employing different measures is investigated from a pure mathematical point of view, and the t-test statistical method is used for comparing the robustness of the learning algorithm. Experimental results on ORL and FERET face databases show that KFDA/QR and KFDA/SVD are more effective and feasible than Fuzzy Discriminant Analysis (FDA) and Kernel Discriminant Analysis (KDA) in terms of the mean correct recognition rate.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2013, 23, 4; 887-903
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 89

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