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The wavelength modulation‐active laser heterodyne spectroscopy (WM‐ALHS), which introduces wavelength modulation technique into active laser heterodyne spectroscopy, is reported to enhance the gas standoff detection capability of weak return optical power. The ALHS gas standoff detection system is developed using a 1.65 μm butterfly packaged distributed feedback laser with tail fiber and an all‐fiber structure, which successfully detects methane concentrations at a distance of 35 cm using an aluminum plate as the reflective surface. Allan variance analysis shows that the system has good stability, and the detection limit at 29.2 s integration time is 0.84 ppm m. Standoff detection experiments with direct absorption‐active laser heterodyne spectroscopy (DA‐ALHS) and wavelength modulation spectroscopy (WMS) are carried out on the basis of the WM‐ALHS system and the detection limits of 4.49 and 1.64 ppm m were achieved within integration times of 18.6 and 29 s for DA‐ALHS and WMS, respectively. The superiority of the WM‐ALHS method compared to these two spectral detection methods is demonstrated. Furthermore, the feasibility of applying WM‐ALHS to gas standoff detection has been verified, laying the foundation for the development of this spectroscopic technology. [ABSTRACT FROM AUTHOR]

Simultaneous measurement of ammonia and ethylene is of great significance for atmospheric environmental monitoring, industrial process controlling and medical respiratory diagnosing. A wavelength modulation spectroscopy based on a 9.56 μm quantum cascade laser (QCL) and a hollow waveguide with a length of 5 m is reported for simultaneous gas sensing of ammonia (NH3) and ethylene (C2H4). The strong absorption lines of NH3 and C2H4 located at 1046.4 and 1045.97 cm−1, respectively, are selected, which can be covered by current tuning of the QCL. Based on the measured frequency modulation characteristics of the QCL, the modulation amplitude is optimized. The sensor performance evaluation shows that it has a sensitivity of 63.2 ppb and 0.775 ppm for NH3 and C2H4 respectively, with time resolution of 1 s. Furthermore, Allan variance analysis shows that the detection limit of NH3 and C2H4 can reach 7 ppb and 45 ppb, respectively, for about 100 s averaging time. The system is stable and robust, thus could be used in real‐time monitoring of atmospheric environment and extended to the field of exhaled breath analysis in the future. [ABSTRACT FROM AUTHOR]

The survey on hot topics was added in 2007 to the annual survey of state directors of community colleges conducted by the University of Alabama Education Policy Center. The survey data provided an opportunity for examining the personal attitudes toward the hot topics and the associations between these attitudes and state contexts. This study finds five clear interpretable factors of personal attitudes, and it provides support for the sound psychometric properties of the survey questionnaire. As a group, state directors had an optimistic view toward the increased attention to student success, the development of new data systems to track student success, and the enrollment capacity of community colleges. On the other hand, state directors were less optimistic toward state funding policies and the growth of four-year degree programs at community colleges. They recognized that funding for facilities was a priority, and federal support was needed. The findings indicate that the availability of local tax support influenced state directors' attitude toward state funding policies. Implications for practitioners and researchers are discussed. (Contains 2 tables.)

This quantitative study investigated the extent to which doctoral leadership programs are practically relevant. Results revealed that community college leaders and leadership program faculty did not differ significantly on the importance ratings on the American Association of Community Colleges (AACC) competencies. The subsequent analysis, however, showed a significant gap between what were rated by faculty as important and what were emphasized in the leadership programs. The findings suggest possible reasons for the gap and raise important questions for future research. (Contains 3 tables.)