Metal parts and residues from machining processes are usually polluted with cutting or grinding oil and have to be cleaned before further use. Supercritical carbon dioxide can be used for extraction processes and precision cleaning of metal parts, as developed at Forschungszentrum Karlsruhe. For optimizing and efficiently conducting the extraction process, in-line analysis of oil concentration is desirable. Therefore, a monitoring method using fiber-optic NIR spectroscopy in combination with PLS calibration has been developed. In an earlier paper we have described the instrumental set-up and a calibration model using the model compound squalane in the spectral range of the CH combination bands from 4900 to 4200 cm−1. With this model only poor prediction results were obtained if applied to technical oil samples in supercritical CO2. In this paper we describe a new calibration model, which was set up for the squalane/carbon dioxide system covering the 323–353 K temperature and the 16–35.6 MPa pressure range. Here, calibration data in the spectral range from 6100 to 5030 cm−1 have been used. This range includes the 5100 cm−1 CO2 band of the Fermi triad as well as the hydrocarbon 1st overtone CH stretching bands, where spectral features of oil compounds and squalane are more similar to each other.
The root mean-squared error of prediction obtained with this model is 4 mg cm−3 for carbon dioxide and 0.4 mg cm−3 for squalane, respectively. The utilizability of the newly developed PLS calibration model for predicting the oil concentration and CO2 density of solutions of technical oils in supercritical carbon dioxide has been tested. Three types of “real world” cutting and grinding oil formulations were used in these experiments. The calibration proved to be suitable for determining the technical oil concentration with an error of 1.1 mg cm−3 and the CO2 density with an error of 6 mg cm−3. Therefore, it seems possible to apply this in-line analytical approach on the basis of a cost-effective and time-saving model compound calibration for the surveillance of real world de-oiling and other extraction process based on supercritical carbon dioxide, and furthermore to establish an automated process termination criterion based on this technique. 相似文献
Optical fiber bend sensor with photonic crystal fiber (PCF) based Mach-Zehnder interferometer (MZI) is demonstrated experimentally. The results show that the PCF-based MZI is sensitive to bending with a sensitivity of 3.046 nm/m−1 and is independent on temperature with a sensitivity of 0.0019 nm/°C, making it the best candidate for temperature insensitive bend sensors. To that end, another kind of bend sensor with higher sensitivity of 5.129 nm/m−1 is proposed, which is constructed by combining an LPFG and an MZI with zero offset at the second splice mentioned above. 相似文献
In this paper, we describe the development and application of a pH-sensitive plasmonics-active fiber-optic nanoprobe suitable
for intracellular bioanalysis in single living human cells using surface-enhanced Raman scattering (SERS) detection. The effectiveness
and usefulness of SERS-based fiber-optic nanoprobes are illustrated by measurements of intracellular pH in HMEC-15/hTERT immortalized
“normal” human mammary epithelial cells and PC-3 human prostate cancer cells. The results indicate that fiber-optic nanoprobe
insertion and interrogation provide a sensitive and selective means to monitor cellular microenvironments at the single cell
level. 相似文献
The fluid mechanics of water entry is studied through investigating the underwater acoustics and the supercavitation. Underwater
acoustic signals in water entry are extensively measured at about 30 different positions by using a PVDF needle hydrophone.
From the measurements we obtain (1) the primary shock wave caused by the impact of the blunt body on free surface; (2) the
vapor pressure inside the cavity; (3) the secondary shock wave caused by pulling away of the cavity from free surface; and
so on. The supercavitation induced by the blunt body is observed by using a digital high-speed video camera as well as the
single shot photography. The periodic and 3 dimensional motion of the supercavitation is revealed. The experiment is carried
out at room temperature.
The project supported by the “BaiRen Plan” of Chinese Academy of Sciences 相似文献
Here we propose two methods using conventional evaporation process to produce tailored Pd/Au composite thin films for hydrogen sensing. In the first method Pd and Au are evaporated simultaneously using different evaporation rate. In the other, alternated nano-layer of Pd and Au are evaporated. Some characteristics of the thin films and their response to hydrogen when they are deposited over optical fibers are experimentally analyzed. Optical fiber sensors for detection of hydrogen concentration lower than 4% and response time of 10 s approximately are demonstrated. The possibility to precisely control the proportion of the constituents of Pd-alloys thin films to produce optical fiber hydrogen sensors with fast response makes these methods very attractive. 相似文献