Severity: Warning
Message: file_get_contents(https://...@pubfacts.com&api_key=b8daa3ad693db53b1410957c26c9a51b4908&a=1): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 176
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 176
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 250
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 1034
Function: getPubMedXML
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3152
Function: GetPubMedArticleOutput_2016
File: /var/www/html/application/controllers/Detail.php
Line: 575
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 489
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
In this paper, we demonstrate a flexible leaky hollow core fiber (LHCF) photoacoustic (PA) gas sensor based on an embedded acoustic resonant structure. The sensor employs a part of a gas conduit as the buffer chamber to construct an equivalent T-type half-open PA cell. The LHCF is installed inside of the gas conduit and the LHCF is hence replaceable. Also, the flexibility of the LHCF and the gas conduit make the gas sensor flexible to reduce spatial size. The inner diameter and length of the LHCF are 1.6 mm and 70 mm, respectively. The inner diameter and length of the gas conduit are 4 mm and 210 mm, respectively. The total gas volume of the sensor is only ∼2.6 mL. Trace acetylene (CH) is selected as the target gas to evaluate the performance of the PA gas sensor. A near-infrared distributed feedback (DFB) laser is utilized to generate the PA signal, and an electrical micro-electro-mechanical system (MEMS) microphone is employed to extract the PA signal. The experimental results show that the minimum detection limit (MDL) can be as low as 21.1 ppb when the lock-in integration time is 200 s. And the normalized noise equivalent absorption coefficient (NNEA) is calculated to be 5.7 × 10·W/cm·Hz.
Download full-text PDF |
Source |
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http://dx.doi.org/10.1021/acs.analchem.3c01476 | DOI Listing |
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