We fabricated long-period fiber gratings (LPFGs) using electric arc discharges. We observed that the fiber becomes slightly tapered due to longitudinal tension during the arc: this effect depends on the arc current...We fabricated long-period fiber gratings (LPFGs) using electric arc discharges. We observed that the fiber becomes slightly tapered due to longitudinal tension during the arc: this effect depends on the arc current and time length. We experimentally investigated how these characteristics can influence grating's performances, especially in view of employing the LPFG as gain equalizer for an erbium-doped optical amplifier. As expected, we found that the spectral response of the grating depends on the period A, the intensity of the perturbation, the grating length and the type of mode-coupling induced. Since this last parameter cannot be estimated directly from the transmission spectra, we propose a method to determine the modecoupling occurring in the device and to assess the index modulation induced by the electric arcs. This method combines both experimental and simulated data, and can be used to characterize LPFGs made-up by any method.展开更多
Herein we have employed high-level multi-reference CASSCF and MS-CASPT2 electronic structure methods to systematically study the photochemical mechanism of intramolecularly hydrogen-bonded 2-(2'-hydroxyphenyl)-4-me...Herein we have employed high-level multi-reference CASSCF and MS-CASPT2 electronic structure methods to systematically study the photochemical mechanism of intramolecularly hydrogen-bonded 2-(2'-hydroxyphenyl)-4-methyloxazole. At the CASSCF level, we have optimized minima, conical intersections, minimum-energy reaction paths relevant to the excited-state intramolecular proton transfer (ESIPT), rotation, photoisomerization, and the excited-state deactivation pathways. The energies of all structures and paths are refined by the MS-CASPT2 method. On the basis of the present results, we found that the ESIPT process in a conformer with the OH... N hydrogen bond is essentially barrierless process; whereas, the ESIPT process is inhibited in the other conformer with the OH... O hydrogen bond. The central single-bond rotation of the S1 enol species is energetically unfavorable due to a large barrier. In addition, the excited-state deactivation of the S1 keto species, as a result of the ultrafast ESIPT, is very efficient because of the existence of two easily-approached keto S1/S0 conical intersections. In stark contrast to the S1 keto species, the decay of the S1 enol species is almostly blocked. The present theoretical study contributes valuable knowledge to the understanding of photochemistry of similar intramolecularly hydrogen-bonded molecular and biological systems.展开更多
The velocity of warhead fragment is key criteria to determine its mutilation efficiency.We have designed an optoelectronic system to accurately measure the average velocity of warhead fragments.The apparatus including...The velocity of warhead fragment is key criteria to determine its mutilation efficiency.We have designed an optoelectronic system to accurately measure the average velocity of warhead fragments.The apparatus including two parallel laser screens spaced apart at a known fixed distance for providing time measurement start and stop signals.The large effective screen area is formed by laser source,retro-reflector and large area photo-diode with a central hole.Whenever a moving fragment interrupts two optical screen,the corresponding photometers senses the event,due to partial obscuration of the incident energy.Experiments have been performed to measure velocity of the different kinds of projectiles and fragments within various size and velocity ranges,including 7.62 mm bullet shooting experiments,prefabricated steel-ball exploding experiments.They were proved that the system is adequate to measure the velocity of larger than 5 mm,less than 1 000 m/s in the range,when fixed trajectory,test the velocity of the projectile average relative deviation is less than 4.21%.The system can perform satisfactorily with a lot of advantages such as larger effective light screen area,quick response speed,low uncertainty,strong repetition and reliability,etc.展开更多
This paper describes a kinetic spectrophotometric method for simultaneous determination of three cephalosporin antibiotics,cephradine,cefaclor and cefixime,with the aid of chemometrics. The method relies on their oxid...This paper describes a kinetic spectrophotometric method for simultaneous determination of three cephalosporin antibiotics,cephradine,cefaclor and cefixime,with the aid of chemometrics. The method relies on their oxidation with KMnO4 to produce green manganate with different kinetic rates in alkaline medium. The proposed method was successfully applied to a pharmacokinetic study of three cephalosporin antibiotics in rabbit plasma via intravenous injections. The results indicated that the amount of cephradine,cefaclor and cefixime were reduced rapidly in rabbit blood,showing clear dose-dependency and the half-life of cefixime (160 min) was longer than those of cephradine (60 min) and cefaclor (60 min).展开更多
This paper proposes an unprecedented systematic approach for real-time monitoring the temperature and flow of diesel engine by using embedded fiber Bragg grating(FBG). By virtue of FBG's temperature effect, we des...This paper proposes an unprecedented systematic approach for real-time monitoring the temperature and flow of diesel engine by using embedded fiber Bragg grating(FBG). By virtue of FBG's temperature effect, we design a novel sensitive FBG temperature sensing probe to measure the temperature of cylinder head and inlet flow of diesel engine. We also establish the corresponding software platform for intuitive data analysis. The experimental and complementary simulation results simultaneously demonstrate that the FBG-based optical fiber technique possesses extraordinary reproducibility and sensitivity, which makes it feasible to monitor the temperature and inlet flow of diesel engine. Our work can provide an effective way to evaluate the thermal load of cylinder head in diesel engine.展开更多
文摘We fabricated long-period fiber gratings (LPFGs) using electric arc discharges. We observed that the fiber becomes slightly tapered due to longitudinal tension during the arc: this effect depends on the arc current and time length. We experimentally investigated how these characteristics can influence grating's performances, especially in view of employing the LPFG as gain equalizer for an erbium-doped optical amplifier. As expected, we found that the spectral response of the grating depends on the period A, the intensity of the perturbation, the grating length and the type of mode-coupling induced. Since this last parameter cannot be estimated directly from the transmission spectra, we propose a method to determine the modecoupling occurring in the device and to assess the index modulation induced by the electric arcs. This method combines both experimental and simulated data, and can be used to characterize LPFGs made-up by any method.
文摘Herein we have employed high-level multi-reference CASSCF and MS-CASPT2 electronic structure methods to systematically study the photochemical mechanism of intramolecularly hydrogen-bonded 2-(2'-hydroxyphenyl)-4-methyloxazole. At the CASSCF level, we have optimized minima, conical intersections, minimum-energy reaction paths relevant to the excited-state intramolecular proton transfer (ESIPT), rotation, photoisomerization, and the excited-state deactivation pathways. The energies of all structures and paths are refined by the MS-CASPT2 method. On the basis of the present results, we found that the ESIPT process in a conformer with the OH... N hydrogen bond is essentially barrierless process; whereas, the ESIPT process is inhibited in the other conformer with the OH... O hydrogen bond. The central single-bond rotation of the S1 enol species is energetically unfavorable due to a large barrier. In addition, the excited-state deactivation of the S1 keto species, as a result of the ultrafast ESIPT, is very efficient because of the existence of two easily-approached keto S1/S0 conical intersections. In stark contrast to the S1 keto species, the decay of the S1 enol species is almostly blocked. The present theoretical study contributes valuable knowledge to the understanding of photochemistry of similar intramolecularly hydrogen-bonded molecular and biological systems.
基金supported by the Science and Technology on Electronic Test & Measurement Laboratory,China(No.9140C1204041009)Science and Technology on Electronic Test & Measurement Laboratory Fund for Young Scholars,China
文摘The velocity of warhead fragment is key criteria to determine its mutilation efficiency.We have designed an optoelectronic system to accurately measure the average velocity of warhead fragments.The apparatus including two parallel laser screens spaced apart at a known fixed distance for providing time measurement start and stop signals.The large effective screen area is formed by laser source,retro-reflector and large area photo-diode with a central hole.Whenever a moving fragment interrupts two optical screen,the corresponding photometers senses the event,due to partial obscuration of the incident energy.Experiments have been performed to measure velocity of the different kinds of projectiles and fragments within various size and velocity ranges,including 7.62 mm bullet shooting experiments,prefabricated steel-ball exploding experiments.They were proved that the system is adequate to measure the velocity of larger than 5 mm,less than 1 000 m/s in the range,when fixed trajectory,test the velocity of the projectile average relative deviation is less than 4.21%.The system can perform satisfactorily with a lot of advantages such as larger effective light screen area,quick response speed,low uncertainty,strong repetition and reliability,etc.
基金support from the National Natural Science Foundation of China (21065007)the State Key Labo-ratory of Food Science and Technology of Nanchang University (SKLF-MB-200807 & SKLF-TS-200919)
文摘This paper describes a kinetic spectrophotometric method for simultaneous determination of three cephalosporin antibiotics,cephradine,cefaclor and cefixime,with the aid of chemometrics. The method relies on their oxidation with KMnO4 to produce green manganate with different kinetic rates in alkaline medium. The proposed method was successfully applied to a pharmacokinetic study of three cephalosporin antibiotics in rabbit plasma via intravenous injections. The results indicated that the amount of cephradine,cefaclor and cefixime were reduced rapidly in rabbit blood,showing clear dose-dependency and the half-life of cefixime (160 min) was longer than those of cephradine (60 min) and cefaclor (60 min).
基金supported by the National Natural Science Foundation of China(Nos.61271073 and 61473175)the Fundamental Research Funds of Shandong University(No.2015JC040)
文摘This paper proposes an unprecedented systematic approach for real-time monitoring the temperature and flow of diesel engine by using embedded fiber Bragg grating(FBG). By virtue of FBG's temperature effect, we design a novel sensitive FBG temperature sensing probe to measure the temperature of cylinder head and inlet flow of diesel engine. We also establish the corresponding software platform for intuitive data analysis. The experimental and complementary simulation results simultaneously demonstrate that the FBG-based optical fiber technique possesses extraordinary reproducibility and sensitivity, which makes it feasible to monitor the temperature and inlet flow of diesel engine. Our work can provide an effective way to evaluate the thermal load of cylinder head in diesel engine.