Informacja

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

Wyszukujesz frazę "impurity" wg kryterium: Temat


Tytuł:
COREDIV modelling of JET ILW discharges with different impurity seeding: nitrogen, neon, argon and krypton
Autorzy:
Ivanova-Stanik, I.
Zagórski, R.
Powiązania:
https://bibliotekanauki.pl/articles/148412.pdf
Data publikacji:
2017
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
impurity seeding
integrated modelling
tokamak
Opis:
Numerical simulations with the COREDIV code of JET H-mode discharges with 25 MW of auxiliary heating in the ITER-like wall (ILW) configuration with different impurity seedings – nitrogen (N), neon (Ne), argon (Ar) and krypton (Kr) – are presented. All simulations have been performed with the same transport model and input discharge parameters like auxiliary heating, volume average plasma density, confi nement factor. Only the seeded impurity puff rate was changed in the calculations. It appears that for the considered heating power of 25 MW and relatively low volume electron average density = 6.2 × 1019 m–3, impurity seeding is necessary. It has been found that for every gas at the maximum level of the seeding rate, allowed by the code convergence, the power to the plate is reduced up to 2–4 MW, with electron temperature at the plate of about 2 eV, indicating semi-detached conditions in the divertor region. It should be noted, however, that in cases with low and medium Z impurity (N, Ne and Ar), tungsten radiation is a signifi cant part of radiation losses and stays above 22–32% of the total energy losses, but for high Z impurity (Kr) it is reduced up to 10% of the total losses. The maximum of the Kr radiation is between the pedestal region and separatrix, showing that radiative mantle can be created, which might have a strong influence on the plasma parameters in the pedestal region.
Źródło:
Nukleonika; 2017, 62, 1; 3-7
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tracing Menstruation in British and American Culture. Strategies of Invisibilization, Stigmatization, and a Question of Im-Purity in Historical and Cultural Context
Autorzy:
Kasenko, Jaśmina
Powiązania:
https://bibliotekanauki.pl/articles/601257.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Marii Curie-Skłodowskiej. Wydawnictwo Uniwersytetu Marii Curie-Skłodowskiej
Tematy:
Menstruation, Purity, Impurity, Vocabularies, Power Relations, Otherness
Opis:
An absentee from the Western culture, the phenomenon of menstruation is an unlikely theme to be found in the British and American media and literature. Historically and culturally the Menstrual blood was considered impure and maudit, thus positioning the menstruating women at the bottom of the power hierarchies, and asserting the social status-quo of the male dominance. Menstruation is also subjected to capitalization which has been shaping the Menstrual attitudes and practices.The aim of the article is to draw a sketch of what menstruating means in the British and American cultures, as well as to reflect on its frequent absence from the cultural deliberations.
Źródło:
New Horizons in English Studies; 2019, 4
2543-8980
Pojawia się w:
New Horizons in English Studies
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
"Dead Souls" and "Open Vessel." Is There a Need for a "New" Meaning of the Hebrew Word nefeš?
Autorzy:
Lemański, Janusz
Powiązania:
https://bibliotekanauki.pl/articles/2158385.pdf
Data publikacji:
2022-09-26
Wydawca:
Katolicki Uniwersytet Lubelski Jana Pawła II
Tematy:
nefeš
corpse
deceased
ritual impurity
open vessel
Opis:
The noun nefeš is ascribed the sense of “corpse” in several instances of the Hebrew Bible. All of them are analysed to trace the possible development of the semantic field of this word. It leads to the conclusion that this implied sense arose from the shortening of longer phrases (nefeš 'ādām; nefeš mēt). The noun nefeš used in them, however, retains its basic meaning of “person,” and its reference to a corpse is only apparent from the context. In a similar sense, the author also reads the use of the abbreviated version, which represents a person and not just a corpse (synecdoche) – a person who dies and gradually passes into the hereafter.
Źródło:
Verbum Vitae; 2022, 40, 3; 661-674
1644-8561
2451-280X
Pojawia się w:
Verbum Vitae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of polyacrylamide on the process of removing impurities in the rare earth leachate
Autorzy:
Wu, Xiaoyan
Zhou, Fang
Liu, Chufan
Feng, Jian
Zhang, Zhenyue
Chi, Ruan
Powiązania:
https://bibliotekanauki.pl/articles/1448504.pdf
Data publikacji:
2021
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
polyacrylamide
rare earth leachate
impurity removal
flocs
Opis:
The impurity removal process of the rare earth (RE) leachate is usually accompanied by the formation of flocs, and a certain amount of polyacrylamide flocculant needs to be added in this process. However, few studies have investigated the effect of the flocculant on the impurity removal process. Therefore, this paper compares the influence on the process of removing impurities with or without the adding of polyacrylamide (PAM). The results showed that the addition of PAM had little effect on the removal rate of impurities, but it was conducive to the recovery of RE. When ammonium bicarbonate was firstly adopted to regulate the solution pH to 5.0, and then sodium sulfide was used to adjust the pH to 5.2, and 0.5 mL/100 mL of PAM was added to the leachate, 96% $Al^{3+}$ and 98% $Zn{2+}$ were removed from the leachate, while 95% RE was maintained. In addition, PAM could accelerate the settlement of flocs and then shorten the production cycle. The increase in RE recovery rate may be due to the addition of PAM to shorten the settling time of the flocs, thereby reducing the RE ions adsorbed during the flocculation process and increasing the recovery rate of the RE.
Źródło:
Physicochemical Problems of Mineral Processing; 2021, 57, 1; 182-191
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Process Optimization for the Gas-Liquid Heterogeneous Reactive Crystallization Process Involved in the Preparation of the Insensitive High Explosive TATB
Autorzy:
Nandi, A. K.
Kshirsagar, A. S.
Thanigaivelan, U.
Bhattacharyya, S. C.
Mandal, A. K.
Pandey, R. K.
Bhattacharya, B.
Powiązania:
https://bibliotekanauki.pl/articles/358228.pdf
Data publikacji:
2014
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
TATB
TCTNB
amination
reaction crystallization
chloride impurity
particle size
Opis:
The thermally stable, insensitive, high explosive 1,3,5-triamino-2,4,6- trinitrobenzene (TATB) is manufactured by amination of 1,3,5-trichloro-2,4,6- trinitrobenzene (TCTNB) in toluene with NH3 gas. It is an isothermal, single-feed, semi-batch, gas-liquid heterogeneous, reaction crystallization process. The amination process is discussed by applying the chemical engineering methodology of mass transfer and reactive crystallization processes based on Two-Film Mass- Transfer (TFMT) theory. Kinetic expressions have been developed to define the chemical reactions as well as the physical phenomena (mass transfer) associated with this process. A single expression has been derived to explain the dependence of the ammonia consumption rate on various process parameters. Subsequently, the influence of various process parameters on the product quality (particle size and chloride impurity content) has been studied on the laboratory scale. Finally, the process has been established in the pilot plant, with optimized process conditions, to realize TATB of desired particle size and chloride content. The effects of feeding excess ammonia, and the presence of mercaptans/hydrogen sulphide impurities in poor quality toluene on the formation of certain undesirable by-products in TATB, are also discussed.
Źródło:
Central European Journal of Energetic Materials; 2014, 11, 1; 31-57
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quality Assessment of Palm Oil from Different Palm Oil Local Factories in Imo State, Nigeria
Autorzy:
Chinedu, Enyoh Emmanuel
Ebere, Enyoh Christian
Emeka, Amaobi Collins
Powiązania:
https://bibliotekanauki.pl/articles/1178270.pdf
Data publikacji:
2017
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Factory
Health
Imo State
Impurity
Palm oil
Storage
dulteration
Opis:
Palm oil is the most commonly used vegetable oil in Nigeria due to its numerous benefits. Therefore, it is very important to investigate the quality of palm oil. In this study, oil samples were collected from different oil mills in Imo state. Physical and chemical properties of the oil samples were evaluated using standard procedures. The result showed that the moisture content ranged from 0.26% to 0.33%, specific gravity ranged from 0.8900 to 0.9250 while the density ranged from 0.8700 g/ml to 0.9100 g/ml. The saponification value (SV), Free fatty acid and Acid value ranged from 192.49 mg KOH/g to 202.73 mg KOH/g, 10.38 mg KOH/g to 18.80 mg KOH/g and 20.76 mg/g to 37.59 mg/g respectively, while the Smoke point and Refractive index ranged from 114.0 °C to 116.2 °C and 1.4615°Bx to 1.4640°Bx respectively. The peroxide value, Iodine value and Ester value ranged from 14.10 mEq./g to 24.80 mEq./g, 0.48wij’s to 2.84wij’s and 160.86 to 172.86 respectively. All samples showed > 35% SV suggesting the palm oil will be good in soap production. It is recommended that oil palm factories in Imo state processing and storage method should be properly monitored to prevent major contamination or adulteration which might have an adverse effect on the future of oil palm industry in Imo state, Nigeria.
Źródło:
World Scientific News; 2017, 88, 2; 152-167
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative study on removal of metallurgical silicon impurities by different acid leaching methods
Autorzy:
Gao, Zijie
Luo, Dawei
Powiązania:
https://bibliotekanauki.pl/articles/24085856.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
metallurgical-grade silicon
hydrometallurgy
acid leaching
impurity removal efficiency
Opis:
Hydrometallurgy is considered a promising method to produce solar-grade silicon (SOG-Si) from metallurgical-grade silicon (MG-Si) due to its advantages of low cost, simple operation, and easy control. In this paper, the effects of particle size of MG-Si, type of acid, leaching time, temperature, and liquid-to-solid ratio on the purification efficiency were investigated in an external field environment with the addition of ultrasound. The purification efficiencies of the two acid-leaching methods were compared. It was found that the simultaneous use of HCl + HNO3 was more effective than using only HCl for impurity removal in MG-Si: the extraction efficiencies of impurities Fe and Al were increased by 2.2% and 13.4%, respectively. The impurity contents in MG-Si before and after calcination pretreatment were also compared. This paper is expected to help researchers select the appropriate hydrometallurgical technique to reduce the impurity content in MG-Si.
Źródło:
Physicochemical Problems of Mineral Processing; 2023, 59, 2; art. no. 162331
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dotyk kobiety. Interpretacja postaci kobiecej w japońskich wyobrażeniach parinirwany
Touch of a Woman. Study on a Female Figure in Japanese Images of Parinirvana
Autorzy:
Sobczyk, Małgorzata
Powiązania:
https://bibliotekanauki.pl/articles/37536564.pdf
Data publikacji:
2024
Wydawca:
Akademia Ignatianum w Krakowie
Tematy:
nirwana
Ānanda
kobieta
dotyk
skalanie
nirvana
woman
touch
impurity
Opis:
Celem niniejszego artykułu jest interpretacja postaci starszej kobiety ukazanej na japońskich przedstawieniach parinirwany przy stopach Buddy (ze szczególnym uwzględnieniem wersji z Myōhō-ji oraz jej kontynuacji). Jak wykazał przegląd chińskich przekładów sutr, za potencjalne źródło inspiracji posłużyło tu piśmiennictwo hinajany, z którego japońska tradycja buddyjska przejęła przekonanie o kalających właściwościach kobiecego dotyku. Następnie, w poszukiwaniu odpowiedzi na pytanie, jakie treści wnosi obecność staruszki na graficznych przedstawieniach parinirwany, posłużono się wybraną literaturą buddyjską podejmującą ten motyw. W toku analizy wykazano, że jej rola polegała na sprowokowaniu dyskusji pomiędzy Mahākāśyapą a Ānandą o miejscu kobiet w gronie uczniów Buddy – świeckich, na przykładzie jej samej, oraz duchownych, na przykładzie pierwszej mniszki Gautami.
This study delves into the portrayal of the female figure depicted at the feet of the Buddha in Japanese parinirvana images, with a specific focus on the Myōhō-ji rendition and its subsequent resumptions. Through an examination of Chinese translations of pertinent sutras, the research explores the potential influence of hinayana texts as a source for this motif, which conveys the notion that impurity can be transmitted through a woman’s touch. To elucidate a more profound comprehension of the significance attributed to the presence of an elderly woman in visual depictions of parinirvana, an array of literary sources were scrutinized. The findings indicate that her inclusion likely served as a catalyst for a discourse between Mahākāśyapa and Ānanda concerning the position of women within the Buddha’s assembly of disciples, encompassing their roles as lay devotees, epitomized by the elderly woman, and as ordained nuns, symbolized by Gautami.
Źródło:
Perspektywy Kultury; 2024, 44, 1; 463-478
2081-1446
2719-8014
Pojawia się w:
Perspektywy Kultury
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dissolution Behavior of Metal Impurities and Improvement of Reclaimed Semiconductor Wafer Cleaning by Addition of Chelating Agent
Autorzy:
Ryu, Keunhyuk
Kim, Myungsuk
Roh, Jaeseok
Lee, Kun-Jae
Powiązania:
https://bibliotekanauki.pl/articles/2049175.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
reclaimed silicon wafer
wafer cleaning
metal impurity
metal complex
chelating agent
Opis:
As a wafer cleaning process, RCA (Radio Corporation of America) cleaning is mainly used. However, RCA cleaning has problems such as instability of bath life, re-adsorption of impurities and high-temperature cleaning. Herein, we tried to improve the purity of silicon wafers by using a chelating agent (oxalic acid) to solve these problems. Compounds produced by the reaction between the cleaning solution and each metal powder were identified by referring to the pourbaix diagram. All metals exhibited a particle size distribution of 10 μm or more before reaction, but a particle size distribution of 500 nm or less after reaction. In addition, it was confirmed that the metals before and after the reaction showed different absorbances. As a result of elemental analysis on the surface of the reclaimed silicon wafer cleaned through such a cleaning solution, it was confirmed that no secondary phase was detected other than Si.
Źródło:
Archives of Metallurgy and Materials; 2021, 66, 4; 977-981
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Impurity-concentration dependence of seebeck coefficient in silicon-on-insulator layers
Autorzy:
Salleh, F.
Asai, K.
Ishida, A.
Ikeda, H.
Powiązania:
https://bibliotekanauki.pl/articles/385169.pdf
Data publikacji:
2009
Wydawca:
Sieć Badawcza Łukasiewicz - Przemysłowy Instytut Automatyki i Pomiarów
Tematy:
Seebeck coefficient
ultrathin silicon-on-Insulator layers
nanostructure
impurity band
Opis:
We measured the Seebeck coefficient of P-doped ultrathin silicon-on-insulator (SOI) layers with thicknesses of 6-100 nm. The dependence of the coefficient on the impurity concentration was investigated, and was shown to be in good agreement with that of bulk Si. In addition, it was found to decrease with increasing impurity concentration, as is usual in semiconductor materials. However, for doping levels above 3.5x1019 cm-3, the Seebeck coefficient was observed to increase. This is likely to be due to the influence of an impurity band.
Źródło:
Journal of Automation Mobile Robotics and Intelligent Systems; 2009, 3, 4; 134-136
1897-8649
2080-2145
Pojawia się w:
Journal of Automation Mobile Robotics and Intelligent Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantitative analysis of α-CL-20 polymorphic impurity in ε-CL-20 using Dispersive Raman Spectroscopy
Autorzy:
Ghosh, M.
Venkatesan, V.
Sikder, N.
Sikder, A. K.
Powiązania:
https://bibliotekanauki.pl/articles/951498.pdf
Data publikacji:
2013
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
CL-20
polymorphs
α-CL-20 impurity
Dispersive Raman Spectroscopy
Opis:
α-CL-20 polymorphic impurity in ε-CL-20 studies have been carried out using Dispersive Raman Spectroscopy. ε-, β-, α- and γ-CL-20 polymorphs were produced using crystallization methods with sample recovery from the solution being >90%, and chemical purity of about 99%. The polymorphs prepared were characterized using Dispersive Raman Spectroscopy over the Raman shift region of 100-3500 cm-1 using a 514 nm argon ion laser. The experimental studies were supported by ab initio computations performed at B3LYP level using a 6-31+G** basis set. The computed vibrational frequencies of the CL-20 conformers correspond to the ε, β and α or γ-CL-20 polymorphs when compared with the observed frequencies. α-CL-20 shows a distinct feature at 280 cm-1 as compared with those of the ε-CL-20 polymorph. Using Dispersive Raman Spectroscopy, a linear relationship was demonstrated for the absolute peak height and absolute peak area ratio of α-CL-20 versus the weight percent of α-CL-20. This method enables a detection limit of this polymorphic impurity down to 2 wt%.
Źródło:
Central European Journal of Energetic Materials; 2013, 10, 3; 419-438
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Scouring of Sheep Wool Using an Acoustic Ultrasound Wave
Autorzy:
Czaplicki, Zdzisław
Matyjas-Zgondek, Edyta
Strzelecki, Stanisław
Powiązania:
https://bibliotekanauki.pl/articles/2056291.pdf
Data publikacji:
2021
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Biopolimerów i Włókien Chemicznych
Tematy:
sheep wool
wool scouring
ultrasounds
scouring agent
impurity of wool
Opis:
The paper describes a method of scouring sheep wool using ultrasound.The inspiration to start work on the use of ultrasound in the process of scouring sheep wool was positive results that had already been achieved for alpaca wool. Due to the fact that sheep wool has many more impurites than alpaca wool, the scouring process is divided into two stages. The first involves the removal of faeces from the wool, which may be up to about 35% of the impurities of sheep wool, while the second stage involves the scouring cycle, wherein the remaining impurities are removed. The ultrasonic scouring process uses domestic merino wool heavily clad, particularly, by faeces. In this study, detergent solutions, alkali soap and sodium carbonate were used. The scouring of wool was carried out with a special apparatus equipped with an ultrasonic generator, at a frequency of 40 kHz. To determine the optimal conditions for scouring sheep wool that could affect the amount of impurities removed, the following parameters were examined: the effect of the scouring time, the concentration of detergents, and the scouring bath ratio. The study resulted in achieving optimal scouring parameters that ensured a satisfactory level of the removal of wool impurities.
Źródło:
Fibres & Textiles in Eastern Europe; 2021, 6 (150); 44--48
1230-3666
2300-7354
Pojawia się w:
Fibres & Textiles in Eastern Europe
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on Distribution and Morphology of Primary Si Under the Effect of Direct Current
Autorzy:
Li, Jiayan
Njuguna, Benson Kihono
Ni, Ping
Wang, Liang
Tan, Yi
Powiązania:
https://bibliotekanauki.pl/articles/2049663.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
silicon source
direct current
Joule heating
Si morphology
Fe impurity
Opis:
A source of pure silicon was added into an alloy refining system during a refining process with the application of a direct electric current. The effect of the temperature difference between the graphite electrodes and the alloy was decreased. The temperature increase value (ΔT) of the Al-28.51wt.%Si alloy sample caused by Joule heating was calculated by weighing the mass of primary silicon. When the current density was 5.0×105A/m2, the overall temperature increase in the alloy was about 90°C regardless of the alloy composition. Adequate silicon atoms recorded the footprint of the electric current in the alloy melt. The flow convection generated by the electric current in the melt during the solidification process resulted in the refinement of primary silicon. The Fe impurity content in alloy refining without the electric current density was 2.16 ppm. However, it decreased to 1.27 ppmw with the application of an electric current density of 5.0×105A/m2.
Źródło:
Archives of Metallurgy and Materials; 2021, 66, 2; 367-372
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of fuzzy programming techniques to solve solid transportation problem with additional constraints
Autorzy:
Halder (Jana), Sharmistha
Jana, Biswapati
Powiązania:
https://bibliotekanauki.pl/articles/406403.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
non-linear solid transportation problem
impurity constraints
fuzzy programming technique
Opis:
An innovative, real-life solid transportation problem is explained in a non-linear form. As in real life, the total transportation cost depends on the procurement process or type of the items and the distance of transportation. Besides, an impurity constraint is considered here. The proposed model is formed with fuzzy imprecise nature. Such an interesting model is optimised through two different fuzzy programming techniques and fractional programming methods, using LINGO-14.0 tools followed by the generalized gradient method. Finally, the model is discussed concerning these two different methods.
Źródło:
Operations Research and Decisions; 2020, 30, 1; 67-84
2081-8858
2391-6060
Pojawia się w:
Operations Research and Decisions
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A method of impurity diagnostics in dense plasma systems
Autorzy:
Tsarenko, A. V.
Chebotarev, V. V.
Sadowski, M. J.
Tereshin, V. I.
Powiązania:
https://bibliotekanauki.pl/articles/146854.pdf
Data publikacji:
2001
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
impurity diagnostics
local thermodynamical equilibrium
plasma accelerator
plasma-target interaction
spectral line
Opis:
The analysis of a plasma impurity composition in many plasma systems (such as coaxial plasma accelerators, magnetic- plasma compressors, plasma-focus devices, and others) is of great importance for plasma physics. In this work we have proposed a new spectral method for the determination of impurity concentrations in relation to the concentration of the main plasma (made of hydrogen in our case). This technique can be used e.g. for diagnostics of a peripheral zone in Plasma-Focus (PF) discharges, where LTE conditions must be fulfilled. Advantages of this method in comparison with other methods, as well as possible errors, are considered and discussed.
Źródło:
Nukleonika; 2001, 46, suppl. 1; 37-40
0029-5922
1508-5791
Pojawia się w:
Nukleonika
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