สถิติ
เปิดเมื่อ28/01/2015
อัพเดท3/05/2022
ผู้เข้าชม790221
แสดงหน้า1022438
ปฎิทิน
October 2022
Sun Mon Tue Wed Thu Fri Sat
      
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
     
สมาชิก

สมัครสมาชิก | ลืมรหัสผ่าน

ทังสเตนคาร์ไบด์

อ่าน 118156 | ตอบ 2613
ทังสเตนคาร์ไบด์
       ทังสเตนคาร์ไบด์ (อังกฤษ: tungsten carbide) มีสูตรเคมีคือ WC ในรูปพื้นฐานจะมีลักษณะเป็นผงสีเทาละเอียด มี 2 โครงสร้างคือแบบหกเหลี่ยม (α-WC) และแบบลูกบาศก์ (β-WC)
 
       ทังสเตนคาร์ไบด์เตรียมได้จากการทำปฏิกิริยาระหว่างทังสเตนกับคาร์บอนที่อุณหภูมิ 1400–2000 °C[3] หรือให้ความร้อนกับทังสเตนไตรออกไซด์และแกรไฟต์โดยตรงที่ 900 °C หรือในแก๊สไฮโดรเจนที่ 670 °C ตามด้วยการคาร์บิวไรเซชันในแก๊สอาร์กอนที่ 1000 °C[4] หรือใช้วิธีการเคลือบด้วยไอเคมี เช่น
  • ทำปฏิกิริยาระหว่างทังสเตนเฮกซะคลอไรด์กับไฮโดรเจนและมีเทนที่อุณหภูมิ 670 °C (1,238 °F)
 WCl6 + H2 + CH4 WC + 6 HCl
  • ทำปฏิกิริยาระหว่างทังสเตนเฮกซะฟลูออไรด์กับไฮโดรเจนและเมทานอลที่อุณหภูมิ 350 °C (662 °F)
                WF6 + 2 H2 + CH3OH → WC + 6 HF + H2O
       ทังสเตนคาร์ไบด์มีจุดหลอมเหลวที่ 2,870 °C (5,200 °F) และจุดเดือดที่ 6,000 °C (10,830 °F) มีความแข็งระดับ 9 ตามมาตราโมสและประมาณ 2600 ตามมาตราวิกเคอส์[5] ทังสเตนคาร์ไบด์มีความแข็งเกร็งมากกว่าเหล็กกล้าประมาณ 2 เท่า มีค่ามอดุลัสของยังประมาณ 530–700 GPa (77,000–102,000 ksi)[2][6][5][7] โมดูลัสของแรงบีบอัด 630–655 GPa และโมดูลัสของแรงเฉือน 274 GPa[8]
 
ด้วยคุณสมบัติความแข็งและทนความร้อนสูง ทังสเตนคาร์ไบด์จึงใช้ทำเป็นเครื่องมือตัดหรือหัวเจาะ ใช้ทำกระสุนเจาะเกราะ เครื่องมือผ่าตัด อุปกรณ์กีฬา เครื่องประดับและอื่น ๆ
 
 
 
 
 
 
 
 
 
 
อ้างอิง
 
  1. Kurlov, p. 22
  2. Blau, Peter J. (2003). Wear of Materials. Elsevier. p. 1345. ISBN 978-0-08-044301-0.
  3. Pierson, Hugh O. (1992). Handbook of Chemical Vapor Deposition (CVD): Principles, Technology, and Applications. William Andrew Inc. ISBN 0-8155-1300-3.
  4. Zhong, Y.; Shaw, L. (2011). 'A study on the synthesis of nanostructured WC–10 wt% Co particles from WO3 , Co3O4 , and graphite'. Journal of Materials Science 46 (19): 6323–6331. Bibcode:2011JMatS..46.6323Z. doi:10.1007/s10853-010-4937-y.
  5. Groover, Mikell P. (2010). Fundamentals of Modern Manufacturing: Materials, Processes, and Systems. John Wiley & Sons. p. 135. ISBN 978-0-470-46700-8.
  6. Kurlov, p. 3
  7. Cardarelli, François (2008). Materials Handbook: A Concise Desktop Reference. Springer Science & Business Media. pp. 640–. ISBN 978-1-84628-669-8.
  8. Kurlov, pp. 30, 135
  9. Sprince, NL.; Chamberlin, RI.; Hales, CA.; Weber, AL.; Kazemi, H. (1984). 'Respiratory disease in tungsten carbide production workers'. Chest 86 (4): 549–557. PMID 6434250. doi:10.1378/chest.86.4.549.
  10. 12th Report on Carcinogens'. National Toxicology Program. http://ntp.niehs.nih.gov/go/roc12. เรียกข้อมูลเมื่อ 2011-06-24.
ความคิดเห็น :
1681
อ้างอิง

Billy
Who is your favorite singer/actress/famous star? Their net worth can be found easily at net worth
 
Billy [222.254.10.xxx] เมื่อ 18/05/2022 19:42
1682
อ้างอิง

Vikaspuri Escorts
Thank you very much for your blog site is very nice and users for the best website
Escorts Service Vikaspuri is one of the splendid administrations which involves care first and women shine with this calling. You won't find anything out of the ordinary in this calling! You'll find in this aid tasteful, innocent, educated, and fun-loving young women who can be with any man. Regardless of how you reach or become famous if you are looking for a date, generally choose the best-skilled friend. Escorts Girl in Vikaspuri to benefit then choose us. We are one of the most mind-blowing Escort organizations providing the best quality support.
 
Vikaspuri Escorts [103.172.73.xxx] เมื่อ 19/05/2022 11:32
1683
อ้างอิง

Mumbai Escorts

Hey, this is Top Mumbai Escorts service, I read your post, and I would like to tell you that. Thank you for sharing this great and useful blog. I love all your posts, and I am reading all your posts. As an independent call girl in Mumbai this is very helpful for me to enhance my carnival knowledge. I love to explore the world of sex, and tried to satisfying my customer with all pleasure.

Mumbai Escorts Services: Mumbai Escorts | Mumbai Escort Girls | Mumbai Call Girls | Mumbai Escort Models | Mumbai Desi Girl | Foreign Escort Girls in Mumbai | Mumbai Escorts Offer | Mumbai Call Girl Photo | Mumbai Escorts Blog | Mumbai Call Girl Phone Number 

Mumbai Escorts Locations: 
Andheri Escorts | Bandra Escorts | Borivali Escorts | Chembur Escorts | Goregaon Escorts | Mira Road Escorts | Navi Mumbai Escorts | Nerul Escorts |Thane Escorts | Vashi Escorts 

Mumbai Escorts Categories: 
African Call Girls in Mumbai | Mumbai Call Girls Whatsapp Number | Mumbai Erotic Massage | Mumbai Housewife Escort | Mumbai Marathi Call Girls | Mumbai Muslim Call girls | Mumbai Nepali Call Girls | Mumbai Phone Sex Service | Mumbai Sex Aunty Number | Mumbai Whatsapp Sex Chat
 
 
ลิงค์ที่เกี่ยวข้อง : https://www.topmumbaiescorts.in
Mumbai Escorts [106.216.67.xxx] เมื่อ 19/05/2022 19:36
1684
อ้างอิง

tinongthitruong
[url=https://tinnongthitruong.net/bo-tui-cach-dau-tu-finhay-hieu-qua-cho-nguoi-moi-bat-dau.html]cách dùng finhay[/url] [url=https://tinnongthitruong.net/du-doan-gia-dat-nam-2022-mang-not-thang-hay-tram.html]dự báo thị trường bất đông sản 2022[/url] [url=https://tinnongthitruong.net/dau-tu-finhay-co-an-toan-khong-hay-tim-hieu-truoc-khi-xuong-tien.html]đầu tư finhay là gì[/url] [url=https://tinnongthitruong.net/5-y-tuong-bat-xu-huong-kinh-doanh-2022-2025.html]xu hướng kinh doanh 2025[/url] [url=https://tinnongthitruong.net/co-bao-nhieu-tien-thi-nen-mua-nha-chung-cu.html]chung cư bao nhiêu tiền[/url] [url=https://tinnongthitruong.net/lam-phat-nen-dau-tu-gi-de-bao-ve-tai-san-cua-ban.html]lạm phát nên đầu tư gì[/url] [url=https://tinnongthitruong.net/dau-tu-finhay-co-an-toan-khong-hay-tim-hieu-truoc-khi-xuong-tien.html]có 500 triệu nên làm gì[/url] [url=https://tinnongthitruong.net/cach-dau-tu-co-phieu-dai-han-mang-lai-hieu-qua-cao.html]nắm giữ cổ phiếu dài hạn[/url] [url=https://tinnongthitruong.net/du-doan-gia-dat-nam-2022-mang-not-thang-hay-tram.html]tình hình giá đất năm 2022[/url] [url=https://tinnongthitruong.net/bi-quyet-kinh-doanh-thoi-4-0-mang-lai-nhieu-tien.html]kinh doanh thời 4.0[/url] [url=https://tinnongthitruong.net/du-doan-gia-dat-nam-2022-mang-not-thang-hay-tram.html]giá đất 2022 có tăng không[/url] [url=https://tinnongthitruong.net/du-doan-gia-dat-nam-2022-mang-not-thang-hay-tram.html]giá đất đầu năm 2022[/url] [url=https://tinnongthitruong.net/bo-tui-cach-dau-tu-finhay-hieu-qua-cho-nguoi-moi-bat-dau.html]đầu tư finhay như thế nào[/url] [url=https://tinnongthitruong.net/du-doan-gia-dat-nam-2022-mang-not-thang-hay-tram.html]dự báo đất nền 2022[/url] [url=https://tinnongthitruong.net/mua-dat-voi-50-trieu-van-de-nan-giai-khong-cua-rieng-ai.html]bán nhà 50 triệu[/url] [url=https://tinnongthitruong.net/nen-dau-tu-vang-hay-chung-khoan-de-sinh-loi-hieu-qua-hien-nay.html]nên đầu tư vàng hay chứng khoán[/url] [url=https://tinnongthitruong.net/dau-tu-finhay-co-an-toan-khong-hay-tim-hieu-truoc-khi-xuong-tien.html]finhay có đáng tin cậy không[/url] [url=https://tinnongthitruong.net/dau-tu-finhay-co-an-toan-khong-hay-tim-hieu-truoc-khi-xuong-tien.html]app finhay có an toàn không[/url] [url=https://tinnongthitruong.net/du-doan-gia-dat-nam-2022-mang-not-thang-hay-tram.html]dự báo giá đất 2022[/url] [url=https://tinnongthitruong.net/bo-tui-cach-dau-tu-finhay-hieu-qua-cho-nguoi-moi-bat-dau.html]chiến lược đầu tư finhay[/url] [url=https://tinnongthitruong.net/dau-tu-finhay-co-an-toan-khong-hay-tim-hieu-truoc-khi-xuong-tien.html]gửi tiền vào finhay có an toàn không[/url] [url=https://tinnongthitruong.net/du-doan-gia-dat-nam-2022-mang-not-thang-hay-tram.html]dự báo nhà đất 2022[/url]
 
ลิงค์ที่เกี่ยวข้อง : https://tinnongthitruong.net
tinongthitruong [1.52.206.xxx] เมื่อ 20/05/2022 09:38
1685
อ้างอิง

tinongthitruong
 
ลิงค์ที่เกี่ยวข้อง : https://tinnongthitruong.net
tinongthitruong [1.52.206.xxx] เมื่อ 20/05/2022 09:38
1686
อ้างอิง

cheesecake canada
Hi, thank you for sharing your valuable site with us in such an understandable site.      
cheesecake canada
 
cheesecake canada [49.149.83.xxx] เมื่อ 20/05/2022 13:23
1687
อ้างอิง

Priyakr

How To Get Best Low Rate Call Girls in Noida Escort Service?

Noida escort agency never takes advance payment. Whenever you take service from any of our agents. So our agent’s driver himself will come to drop the girl at the location mentioned by you, at the same time you will give the payment cash or online to our driver. You can take online through us. You will have to come to our website online for a contact with our agent, after that you will contact our agent, our agent will give you all the information over the phone. Our agent will give you a full information phone and after showing the images of on WhatsApp, you will leave your girl at the location mentioned only when you are full certified. You can take service in this way.

Best Call Girl NoidaBest Call Girl Service NoidaBest Call Girl Site NoidaBest Call Girls NoidaBest Escort Service In IndiaBest Low Rate Call Girls Noida Escort ServiceBest Escort Service NoidaBest Escort Services NoidaBest Escorts Service NoidaCal Girls NoidaCall Gairl NoidaCall Girl Agency NoidaCall Girl Agent NoidaCall Girl Agent Number NoidaCall Girl At Low Price NoidaCall Girl At NoidaCall Girl Booking NoidaCall Girl Broker NoidaCall Girl Charge NoidaCall Girl Charges NoidaCall Girl Cheap Noida

Best Call Girl NoidaBest Call Girl Service NoidaBest Call Girl Site NoidaBest Call Girls NoidaBest Escort Service In IndiaBest Escort Service NoidaBest Escort Services NoidaBest Escorts Service NoidaCal Girls NoidaCall Gairl NoidaCall Girl Agency NoidaCall Girl Agent NoidaCall Girl Agent Number NoidaCall Girl At Low Price NoidaCall Girl At NoidaCall Girl Booking NoidaCall Girl Broker NoidaCall Girl Charge NoidaCall Girl Charges NoidaCall Girl Cheap Noida

Call Girls in Noida

Housewife call girls in noidaCollege call girls in noidaHigh profile call girls in noidaIndependent call girls in noidaRussian call girls in noidaModel call girls in noidaAirhostess call girls in noidaForeigner call girls in noidacheap call girls in noidacall girl in noidanoida call girls servicecall girl number in noidaindependent call girls in noidacall girl number noidanoida call girl noescort service in noidaescort girls in noidanoida call girl numberGirls for sex in noidaGirls in noidaCall girls in noidaNoida escortsEscorts in noidaNoida call girlsNoida Escorts serviceEscort Service in noidaHousewife escorts in noidaCollege call girls in noidaHigh profile escorts in noidacall girl in noidacall girl in noidaIndependent call girls in noidaRussian escorts in noidaModel escorts in noida

Call Girl Cheap Price NoidaCall Girl Cheap Rate NoidaCall Girl Contact NoidaCall Girl Contact No NoidaCall Girl Contact No. NoidaCall Girl Contact Number NoidaBest Low Rate Call Girls Noida Escort ServiceCall Girl Contacts NoidaCall Girl Cost NoidaCall Girl Detail NoidaCall Girl Details NoidaCall Girl Direct Number NoidaCall Girl Escort NoidaCall Girl Escort Service NoidaCall Girl Escorts NoidaCall Girl Fee NoidaCall Girl Fees NoidaCall Girl For Night NoidaCall Girl For One Night NoidaCall Girl For Sex Noida

Call Girl Full Night NoidaCall Girl Home Service NoidaCall Girl Images NoidaCall Girl In Cheap Price NoidaCall Girl In Cheap Rate NoidaCall Girl In IndiaCall Girl In Low Price NoidaCall Girl In Low Rate NoidaCall Girl In NoidaCall Girl IndiaCall Girl IndianCall Girl Ka Number NoidaCall Girl Ka Rate NoidaCall Girl Ke Number NoidaCall Girl Ki Photo NoidaCall Girl Low Budget NoidaCall Girl Low Cost NoidaCall Girl Low Price NoidaCall Girl Low Rate NoidaCall Girl Lowest Price NoidaCall Girl Noida

Call Girl Mobile Number NoidaCall Girl Model NoidaCall Girl Model Town NoidaCall Girl Nambar NoidaCall Girl Namber NoidaCall Girl Near By NoidaCall Girl Near By Me NoidaCall Girl Near NoidaCall Girl Near Me Low Price NoidaCall Girl Near Me NoidaCall Girl Nearby NoidaCall Girl Nearly NoidaCall Girl Need NoidaCall Girl Night NoidaCall Girl Night Service NoidaCall Girl No In Justdial NoidaCall Girl No In NoidaCall Girl No NoidaCall Girl No. NoidaCall Girl Number Low Price Noida

Low Rate Escort Service in Noida

Call Girl Number NoidaCall Girl Numbers NoidaCall Girl One Night NoidaCall Girl One Night Price NoidaCall Girl Online Service NoidaCall Girl Ph No NoidaCall Girl Phone No NoidaCall Girl Phone Number NoidaCall Girl Photo NoidaCall Girl Photos NoidaCall Girl Pic NoidaCall Girl Pics NoidaCall Girl Price In IndiaCall Girl Price NoidaCall Girl Prices NoidaCall Girl Prize NoidaCall Girl Profile NoidaCall Girl Rate In IndiaCall Girl Rate List NoidaCall Girl Rate NoidaCall Girl Rates Noida

Call Girl Rate in Noida

Call Girl Sarvice NoidaCall Girl Service Centre NoidaCall Girl Service In NoidaCall Girl Service NoidaCall Girl Service Near Me NoidaCall Girl Service Number NoidaCall Girl Service Online NoidaCall Girl Services NoidaCall Girl Sex NoidaCall Girl Sex Price NoidaCall Girl Site NoidaCall Girl Top NoidaCall Girl Under 500 NoidaCall Girl Website NoidaCall Girl With Photo NoidaCall Girl With Price NoidaCall Girl With Rate NoidaCall Girls Agent Noida

Call Girls at Cheap Rate in Noida

Call Girls At Low Price NoidaCall Girls Cheap NoidaCall Girls Cheap Price NoidaCall Girls Cheap Rate NoidaCall Girls Contact NoidaCall Girls Contact No NoidaCall Girls Contact Number NoidaCall Girls Cost NoidaCall Girls Details NoidaCall Girls Escort Service NoidaCall Girls For One Night NoidaCall Girls Image NoidaCall Girls Images NoidaCall Girls In Cheap Rate NoidaCall Girls In IndiaCall Girls In Low Price NoidaCall Girls In Noida

Call Girls Low Budget Noida

Call Girls Low Cost NoidaCall Girls Low Price NoidaCall Girls Low Rate NoidaCall Girls NoidaCall Girl’S NoidaCall Girls Near Me NoidaCall Girls No NoidaCall Girls No. NoidaCall Girls Number NoidaCall Girls Numbers NoidaCall Girls Phone Numbers NoidaCall Girls Photo NoidaCall Girls Photos NoidaCall Girls Pic NoidaCall Girls Pics NoidaCall Girls Price NoidaCall Girls Prices NoidaCall Girls Rate NoidaCall Girls Rates NoidaCall Girls Service In Noida

Call Girls With Price NoidaCall Girls With Rate NoidaCall Grils NoidaCall.Girl NoidaCallgirl NoidaCallgirl Near Me NoidaCallgirl No NoidaCallgirl Price NoidaCallgirl Rate NoidaCallgirls NoidaCallgirlservice NoidaCheap Call Girl NoidaCheap Call Girl Near Me NoidaCheap Call Girls NoidaCheap Call Girls Near Me NoidaCheap Callgirl NoidaCheap Escort Service NoidaCheap Escorts NoidaCheap Girls For Sex Noida

Cheap Price Call Girls in Noida

Cheap Price Call Girls NoidaCheap Rate Call Girl NoidaCheap Rate Call Girl Near Me NoidaCheap Rate Call Girls NoidaCheap Rate Call Girls Near Me NoidaCheap Rate Escort Service NoidaCheap Rate Girls NoidaCheapest Call Girl NoidaCheapest Call Girl Near Me NoidaCheapest Call Girls NoidaCheapest Call Girls Near Me NoidaCheapest Escort Service NoidaColl Girl No NoidaColl Girl Number NoidaCost Of Call Girl NoidaEscort Call Girl NoidaEscort Call Girl Service Noida

Escort Girl Image Noida

Escort Girl Images NoidaEscort Girl In NoidaEscort Girl NoidaEscort Girl No NoidaEscort Girl Photo NoidaEscort Girl Pic NoidaEscort Girl Pics NoidaEscort Girl Price NoidaEscort Girl Rate NoidaEscort Girl Service NoidaEscort Girls NoidaEscort Girls Photos NoidaEscort Girls Price NoidaEscort In NoidaEscort NoidaEscort Near Me NoidaEscort Number NoidaEscort Service Call Girl NoidaEscort Service Contact Number Noida

Escort Service Girls Noida

Escort Service In NoidaEscort Service Low Price NoidaEscort Service NoidaEscort Service Near Me NoidaEscort Service No NoidaEscort Service Number NoidaEscort Service Photo NoidaEscort Service Pic NoidaEscort Service Price NoidaEscort Service Rate NoidaEscort Services In NoidaEscort Services NoidaEscort Services Near Me NoidaEscorts Agency NoidaEscorts Girl NoidaEscorts Girls NoidaEscorts Images Noida

Escorts NoidaEscorts Near Me NoidaEscorts Service In NoidaEscorts Service NoidaEscorts Services In NoidaEscorts Services NoidaFemale Escort In NoidaFemale Escort Service NoidaGirl Escort NoidaGirl Escort Service NoidaGirl Service NoidaGirls Escort NoidaGirls Escort Service NoidaGirls For Sex In NoidaGirls In NoidaGirls Service NoidaHigh Profile Call Girl NoidaHigh Profile Escort Service Noida

Home Service Call Girls in Noida

How To Contact Call Girl NoidaHow To Get A Call Girl NoidaHow To Get Call Girl NoidaI Need A Call Girl NoidaI Need Call Girl NoidaI Want A Call Girl NoidaI Want Call Girl NoidaI Want Call Girls NoidaIndia Call Girl NoidaIndia Call GirlsIndian Call GirlIndian Call Girl ImageIndian Call Girl ImagesIndian Call Girl Photo NoidaIndian Call Girl PhotosIndian Call Girl PicIndian Call Girl PicsIndian Call Girl PictureIndian Call Girl PriceIndian Call Girl RateIndian Call GirlsIndian Call Girls Images

Indian Call Girls PhotosIndian Call Girls PicIndian Call Girls PicsIndian Escort Pic NoidaIndian Escort PicsIndian Escort Service NoidaIndian Escorts Pics NoidaIndian Paid Girl Images NoidaIndian Top Call Girl NoidaLocal Call Girl NoidaLocal Call Girl Service NoidaLow Budget Call Girl NoidaLow Budget Call Girls NoidaLow Class Call Girl NoidaLow Cost Call Girl NoidaLow Cost Call Girls NoidaLow Price Call Girl NoidaLow Price Call Girl Near Me NoidaLow Price Call Girl Number NoidaLow Price Call Girls Noida

Low Price Escort in Noida

Low Price Escort Service NoidaLow Price Escorts NoidaLow Price Sex Girl NoidaLow Rate Call Girl NoidaLow Rate Call Girls NoidaLow Rate Escort Service NoidaLowest Price Call Girl NoidaLowest Price Call Girls NoidaNoida Call GirlNoida Call Girl Contact NumberNoida Call Girl NoNoida Call Girl NumberNoida Call Girl ServiceNoida Call GirlsNoida Call Girls NumberNoida EscortNoida Escort GirlNoida Escort GirlsNoida Escort ServiceNoida Escort ServicesNoida EscortsNoida Escorts Service

 
ลิงค์ที่เกี่ยวข้อง : https://www.yamithakur.com/noida.html
Priyakr [171.50.145.xxx] เมื่อ 20/05/2022 15:37
1688
อ้างอิง

Ronald
Heyy!!
Are you looking for some good high quality celeb porn video, we have hundreds of videos with different categories. Click on the link to enjoy the best videos.
<a href=https://unceleb.com/>unceleb</a>
 
Ronald [138.199.63.xxx] เมื่อ 20/05/2022 15:41
1689
อ้างอิง

Ronald
Heyy!!
Are you looking for some good high quality celeb porn video, we have hundreds of videos with different categories. Click on the link to enjoy the best videos.
unceleb
 
Ronald [138.199.63.xxx] เมื่อ 20/05/2022 15:43
1690
อ้างอิง

mina
 
mina [157.119.202.xxx] เมื่อ 21/05/2022 01:57
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262
ความคิดเห็นของผู้เข้าชม
ชื่อผู้แสดงความคิดเห็น :
สถานะ : รหัสผ่าน :
ลิงค์ที่เกี่ยวข้อง :
รหัสความปลอดภัย :