انسان همواره در پی کشف حقایق و قوانین حاکم بر طبیعت زندگی خود بوده است. و از گذشته تا کنون با استفاده از روشهای ساده و پیچیده، راههای مختلفی را به منظور شناسایی عوامل محیطی به کار گرفته است. امروزه نیاز به حسگرهای دقیق در کاربردهای محیط زیستی، کشاورزی، صنعتی، تشخیصهای پزشکی و ... احساس می شود. در واقع، حسگرها، تبدیل کنندههای انرژی به یک نوع انرژی معین هستند که منجر به تولید یک سیگنال خروجی قابل فهم و قابل پردازش ایجاد می شود. حسگرهای گاز، دستهی مهمی از حسگرها هستند که قادرند نوع و غلظت یک گاز معین را در محیط شناسایی کنند.
در طراحی این حسگرها، گازی که غلظت آن مدّ نظر است را گاز هدف (target)مینامند. این گاز با تغییر در خواص فیزیکی و یا شیمیایی افزاره شناسایی میگردد. و برمبنای میزان تغیرات ایجاد شده توسط گاز هدف، نسبت به زمان عدم حضور آن غلظت محاسبه میشود. تاکنون روشهای مختلفی در حسگری گازها به کار گرفته شده است. تغییر رسانایی نیمههادیهای جاذب گاز، تغییرات اپتیکی و تغییرات دمایی از این دسته اند. جدول1 خلاصهای از روشهای موجود را نشان می دهد.
در چند دههی اخیر، نیمههادی به دلیل جذب مناسب، حساسیت بالا، قابلیت کوچکسازی و قیمیت پایین مورد توجه قرار گرفتهاند. با استفاده از موادی چون اکسید روی، اکسید مس و اکسید قلع، حسگرهایی با حساسیت یک قسمت در میلیارد (1 ppb) حاصل شده است. به کار بردن نانوساختارها همانند نانولولههای کربنی، نانوذرات و نانوسیمهای فلزی همگی روشهایی برای افزایش حساسیت حسگرهای نیمههادی محسوب می شود.
امروزه با وجود پیشرفتهای گسترده و حتی ارائه نمونههای تجاری، طراحی و ساخت حسگرها با چالشهایی چون طول عمر، تکرار پذیری، قدرت تشخیص کم و قابلیت مجتمع سازی مواجه است. به کارگیری فنآوری میکرو و نانو روش مؤثری در بهبود عملکرد حسگرها است. انتظار می رود با استفاده از این تکنیکها روز به روز شاهد پیشرفت این افزارهها بود.
جدول 1- انواع حسگرهای گازی مورد استفاده و خواص قابل تغییر
|نوع حسگر||تغییرات خواص|
|اثر میدانی(خازنها، دیودها، ترانزیستورها)||تابع کار(قطبش الکتریکی)|
|اپتیکی||پارامترهای اپتیکی(بازتاب، عبور، جذب، ضریب شکست، طول نوری)|
|کاتالیزوری||گرما یا دما|
|الکتروشیمیایی||نیروی محرکهی الکتریکی یا جریان الکتریکی در سلولهای شیمیایی حالت جامد|
جمعه, 24 شهریور 1396 ساعت 00:26
ارسال شده توسط
Appreciate it for all youjr efforts that you have put iin this.
Very interesting information.
جمعه, 24 شهریور 1396 ساعت 00:24
ارسال شده توسط
You have remarked very interesting points! ps nice internet site.
kyrie 4 http://www.kyrie4.com
پنج شنبه, 23 شهریور 1396 ساعت 22:45
ارسال شده توسط
adidas nmd shoes
It’s remarkable to pay a visit this web site and reading the views of all colleagues about this paragraph, while I am also keen of getting knowledge.
adidas nmd shoes http://www.adidasnmdshoes.us.com
پنج شنبه, 23 شهریور 1396 ساعت 22:23
ارسال شده توسط
I have beenn surfing online more than three hours today,
yet I never found any interesting article like yours.
It's pretty worth enouh for me. In my opinion, if all site owners and bloggers made good content as you did, the net will be a lot more useful than ever before.|
I copuld not resist commenting. Welll written!|
I will immediately sewize your rss as I can't in finding
your e-mail subscription link or newsletter service.
Do yoou have any? Please let me recognize so that I may just subscribe.
It is perfect time to make some plans for the future and it
is time to be happy. I've read this post and if I could I desire to
suggest you some interesting things or advice. Perhaps you could write next arrticles referring to this article.
I desire to read more things about it!|
It is perfect timne to make a few plans for the long rrun and iit is time too be happy.
I have learn this put up and if I may just
I desire tto suggest you few fascinating issuess or advice.
Mybe you could write next atticles referring to this article.
I wish to learn even more issues approximately it!|
I have been surfing onlinne more than three hours today, yet
I by no means found any interesting article like yours.
It's lovely value sufcficient for me. In my opinion, if all webmasters and bloggers made good content material as you did, the
web shall be much more useful than ever before.|
Ahaa, its pleasant dialogue on the topic of this article at this place
at this website, I have read alll that, so at this
time me aloso commenting at this place.|
I am sure this article has touched all the internet users, its really really good
article onn building up nnew web site.|
Wow, this piece of writing is nice, my younger sister is analyziing
these kinds of things, therefore I am going too let know her.|
Saved as a favorite, I like your web site!|
Way cool! Some very valid points! I appreciate you penning this
write-up and also the redst of the website is vefy good.|
Hi, I do believe this is a great web site. I stumbledupon it ;) I'm going to revisit yet again since I bookmarked it.
Monery and freedom iss the greatest way to change, may
you be rjch and continue to help otfher people.|
Woah! I'm really digging the template/theme of this blog.
It's simple, yet effective. A lot of times it's tough to get
that "perfect balance" between usability and vissual appearance.
I must say you've done a mazing job with this. Also, the
blog loass super fast for me on Opera. Exceptional Blog!|
These are genuinely wonderful ideas in regarding blogging.
You have touched some pleasant things here. Any
wayy keep up wrinting.|
I really like what you guys tend to be up too. This kind of clpever work and exposure!
Keep up the wonderful works guys I've you guys too blogroll.|
Hello! Someone in my Myspace gropup shared this website
with us so I came to look iit over. I'm definitely enjoying
the information. I'm book-marking and will be tweeting this
to my followers! Excellent blog and fantastic style
I like what you guys aare up too. This kind of clever work and reporting!
Keep up the fantastic works guyys I've incorporated you guys to our blogroll.|
Hey there would you mind sharing which blog platform you're using?
I'm planning to start my own blog in the near future but I'm having a tough time
deciding between BlogEngine/Wordpress/B2evolution and Drupal.
The reason I ask is because your design and style seems different then most blogs annd I'm lookming for
somthing completely unique. P.S Sorry for
being off-topic but I had to ask!|
Hi would you mind letting me know which web host you're utilizing?
I've loaded your blog in 3 different web browsers and I must say this
blog loads a lot quicker then most. Can you recommend a good
web hosting provider at a reasonable price? Many thanks, I appreciate it!|
I love it when folks get together and share thoughts.
Greatt website, continue the god work!|
Thanbk you for the auspicious writeup. It iin fact was a amusement
account it. Look advanced to far added agreeable from you!
By the way, how could we communicate?|
Hey just wanted tto give you a quick heads up. The words in your post seem
to be running off the screen in Ie. I'm not suree if this is
a formating issue or something to do witgh browser compatibility but
I thought I'd post to let you know. The design and style look great though!
Hope you get the issue solved soon. Kudos|
This is a topic that's nedar to my heart... Take care!
Where aare your contact details though?|
It's very simple to find out any topic on web
as compared to books, as I found this paragraph at this site.|
Does your website have a contact page? I'm having problems locating itt but, I'd like to send you an e-mail.
I've got some creative ideas for your blog you might be interested in hearing.
Eithuer way, great ite and I lkok forward to seeing it groww over time.|
Greetings! I've been reading your website for some time now and
finally got the courage to go ahead and give you a shout out
from Austin Texas! Just wanted to tell you keep up the good job!|
Greetings from Colorado! I'm bored to death at wkrk so I decided to check out your site onn
my iphone during lunch break. I ennoy the info
you present hefe and can't wait to take a
look when I get home. I'm surprised at how fast your blog
loaded on my cell phone .. I'm not evesn using WIFI, just 3G ..
Anyhow, great blog!|
Its like you learn mmy mind! You appear to understand a
lot approximately this, such as you wrote the guide in it or something.
I think that you just can do with some p.c.
to pressure the message home a bit, however other than that, that is magnificent blog.
A fantastic read. I'llcertainly be back.|
I visited multiple web sites except the audio feature for audio songs
current at this wesite is really wonderful.|
Hello, i read your blog from time to time and i own a
similar one and i was just wondering iff you get a lot of sam remarks?
If so how do youu stop it, any plugin or anything you
can recommend? I get so much lately it's driving me insane so any assistance is very much appreciated.|
Greetings! Very helpful advice in this particular article!It's the little changes which will make the
biggest changes. Many thanks for sharing!|
I truly love your site.. Very nice colors & theme.
Did you build this web site yourself? Please reply back
as I'm hoping to create my own ebsite and want to learn where you got this from or juszt wnat the theme is
called. Maany thanks!|
Hello there! This article couldn't be written much better!
Looking at this post reminds me oof my previous roommate!
He continually kept preaching about this.
I am going to send this information tto him. Pretty sure he will have a great read.
Many thanks for sharing!|
Incredible! This blog looks exactly like my old one!
It's on a entirely different topic but it has pretty much tthe same page layout and
design. Excellent choice of colors!|
There iss definately a great deall to know about this issue.
I really like all thhe points you've made.|
You made some goo points there. I looked on the web for additional information about thhe issue and found most individuals will
go aloong with your views on this website.|
Hi, I log on to your blog daily. Your story-telling style is witty, keep doing wha you're doing!|
I just could not depart your websiite prior to suggesting that I really loved the
usual information a person supply on your visitors?
Is goinng to bbe again steadily to check out new posts|
I need to to thank you for this very good read!! I certainly loved every little bit of
it. I've got yoou saved as a favorite to check out new stuff you post…|
Hi there, just wanted to mention, I loved this post.
It wass helpful. Keep on posting!|
Hi there, I enjoy reading all of your article post.
I wanted to write a little comment to support you.|
I always spent my half an hour to read this weblog's
articles or reviews all the time along with a
cup of coffee.|
I always emailed this blog post page tto all my associates, for the reason that
if like to read it afterard my links will too.|
My programmer iss trying to persuade me to move to .net from PHP.
I have always disliked the idea because of the costs.
But he's tryiong none the less. I've been using Movable-type on numerous websites for about a year and
am anxious about switching to another platform. I have heard very good things about blogengine.net.Is there a way I can transfer all my wordpress posts into it?
Any kind of help would be realpy appreciated!|
Hello! I could have sworn I've been to this website
before but after looking at some of the articles I realized it's new to me.
Regardless, I'm certainly pleased I fkund it
and I'll be book-marking it and checking back frequently!|
Terrific article! That is the type of information that are supposed
to be shared around the net. Disgrace on the seek engines for not positioning
this put up higher! Come on over and discuss with my web site .
Heya i aam for the first time here. I found this board and I find It
truly useful & iit helped mme out much. I hope
to give something back and help others like you aided me.|
Hellpo there, I thinhk your web site might be having
internet broeser compatibility issues. Whenever I take a look at your website in Safari, it lookss fine but when opening in Internet Explorer, it has some
overlapping issues. I juwt wanted to provide you with a quifk heads up!
Apardt from that, great site!|
Somebody necessarily help to make severely articles I'd state.
That iss the very first time I frequented your web
page and to this point? I surprised with the research you made to create this
actual put up extraordinary. Great process!|
Heya i am for the primary time here. I foundd
this board and I in finding It truly helpful & it helpd me
ouut a lot. I hope to provide one thing back and help others such as yyou aided
Hello there! I just wish to offer you a big thumbs up for your excellent
info you have here on this post. I am returning tto your web site for more soon.|
I always used to study post iin news papers but now
as I am a user of web thus from now I am using net
for articles, thanks to web.|
Your means oof telling everything in thos article
iss really fastidious, every one can easily understand it, Thanks a lot.|
Hi there, I discovered your website by the use of Google at
the same time as looking for a related subject, your site came up, iit apears great.
I've bookmarked it inn my google bookmarks.
Hi there, ssimply become aware of youjr weblog tthrough Google, and located that
it iis truly informative. I'm gonhna watch out for brussels.
I'll appreciate in the event youu proceed this in future.
Numerous other folks can be benefited from your writing. Cheers!|
I'm curious to find out what blog system you arre working with?
I'm having some smaall security issues with my latest wesite and I would like to find something
more safe. Do you have any recommendations?|
I am really impressed with your writing skills as well ass with the layout on your weblog.
Is this a psid theme or did you modify itt yourself?
Anyway keep up the nice quality writing, it's rare to see a great blog like this oone today.|
I'm extremely inspired with your writing talents and also with the
format tto your blog. Is this a paid topic or did yyou
modify it yourself? Either way keep up the nice
high quality writing, it is uncommon to see a great blog like this one
Hello, Neat post. There's a problem withh your site in web explorer, might check this?
IE nonethless is the market leader and a large part of othyer people
will pass over your great writing because of this problem.|
I am not sure where you're getting your info, but great topic.
I needs to spend some time learning more or understanding more.
Thanks for excellent info I was looking forr this info for my mission.|
Hello, i think thazt i saw you visited my site thus i came to “return the
favor”.I am attempting to find things to
enhance mmy website!I suppose iits ook to use a ffew of your\
پنج شنبه, 23 شهریور 1396 ساعت 21:08
ارسال شده توسط
پنج شنبه, 23 شهریور 1396 ساعت 20:33
ارسال شده توسط
That is a really good tip particularly to those fresh to the blogosphere.
Brief but very precise info… Thanks for sharing this one.
A must read post!
پنج شنبه, 23 شهریور 1396 ساعت 19:51
ارسال شده توسط
adidas pure boost
There are actually a variety of particulars like that to take into consideration. That is a nice point to bring up. I provide the ideas above as general inspiration however clearly there are questions like the one you convey up the place the most important factor can be working in honest good faith. I don?t know if greatest practices have emerged around issues like that, however I am sure that your job is clearly identified as a fair game. Each boys and girls feel the impression of just a moment’s pleasure, for the remainder of their lives.
adidas pure boost http://www.adidaspureboost.us.com
پنج شنبه, 23 شهریور 1396 ساعت 18:20
ارسال شده توسط Lelandglade
301 Moved Permanently
301 Moved Permanently!
پنج شنبه, 23 شهریور 1396 ساعت 17:39
ارسال شده توسط
I am regular visitor, how are you everybody?
This article posted at this web page is actually fastidious. http://www.mmacgn.com/home.php?mod=space&uid=821872&do=profile&from=space
پنج شنبه, 23 شهریور 1396 ساعت 17:27
ارسال شده توسط
You can check here
Magnificent goods from you, man. I've understand your stuff previous to and
you're just extremely wonderful. I actually like what you have acquired here,
certainly like what you are saying and the way in which you say it.
You make it entertaining and you still take care of to keep it
wise. I can't wait to read much more from you. This is really a wonderful site. http://goodtoknow.com/User:ForestWiegand70
از پر شدن تمامی موارد الزامی ستارهدار (*) اطمینان حاصل کنید. کد HTML مجاز نیست.