Improvement of Etalon-fringe Immunity in Diode-laser Derivative Spectroscopy

In a sensitive spectrometry with lead-salt diode lasers, etalon-fringe phenomena often intervene in the measured absorption spectrum. Derivative methods are employed for the purpose of high resolution where the pertaining wavelength is modulated. This paper presents results of mathematical examination on a possible improvement of immunity from the etalon-fringes by choosing the profile of the wavelength modulation

The Seedling Sanctuary: Automated Cold Frame for Gardner Elementary

The purpose of this report is to provide the details of the Seedling Sanctuary, a mechanical engineering senior design project. The project in question is an automated cold frame designed specifically for Gardner Academy, a local elementary school in San Jose. A cold frame is a miniature greenhouse that opens like a chest and is made from clear plastic. Automated ventilation and watering systems create a microclimate within this greenhouse structure to create the ideal growing conditions for seeds. The main purposes of the cold frame are to lengthen the growing season, be maintenance free, and enhance garden education. From testing, the project goals were verified to have been achieved through several performance metrics. First, the system’s ability to lengthen the growing season is dependent on germinating seedlings that can be planted earlier in the season. The automated system maintained the seedlings at the proper soil moisture levels to grow. The system also implemented passive temperature control systems to maintain the plants in ideal conditions. With the ventilation and thermal mass, the system is able to be cooler at the hottest times of day and warmer at night than unprotected plants. The system has also successfully automated the care of the seedlings, achieving our goal of being maintenance free. Finally, the enhancement of garden education was incorporated through community engagement with the design and building of the cold frame, as well as the Bluetooth application which will be used in the school curriculum

Fast Spectrometry System with Using Tunable Laser Diode

Basic prohlems are discussed about a local, realtime and very sensitive air-pollution monitoring using a laser diode. The method employs the second derivative spectrometry replacing the incoherent light source and mechanical choppers in a traditional method with the laser diode and a newly developed electronic system. Etalon fringes at this system becomes the dominant noise source and its statistic and dynamical features are to be understood. Numerical examination was done for the optimal width of optical frequency modulation. A very fast measurement of weak absorption spectra became possible by the development of lock-in-amplifiers with finite integration time instead of a low-pass filter. Spectra of methane in 7.6 μm region and a time-dependent spectrum of the etaIon fringe are shown

Time-domain sensitivity enhancement in pulsed Pb-TDL gas monitors

A Pb-salt tunable diode laser (TDL) has found many applications in the field of atmospheric gas analysis. Its continuous tunablility and fine spectral purity in the mid infrared region are outstanding from other lasers. The only shortcoming is that it requires cryogenic operating temperatures, though, it is improved year by year towards the room temperature operation. A repeated pulse operation of Pb salt diode lasers is possible with a thermoelectric cooling device, which allows an instrument a portable geometry disusing a heavy, bulky and power consuming mechanical refrigerator. A derivative spectrometry was exploiting the quick tunability of Pb salt diode lasers, though they are continuous wave (cw) operated with refrigerator or liquid nitrogen so far. A new system for derivative spectrometry with a pulsed diode laser will extend its field of applications because of reduced weights and size of measuring instruments. A preliminary results is shown that demonstrates the feasibility of an attempt to implement the derivative spectrmetry with repeatedly pulse driven diode lasers. Atmospheric methane was measured with 8 ppm/m sensitivity. Further results of parametric optimization for the best signal to noise ratios under any given device characteristics as well as for available real devices is given

Nonword Repetition Tasks in Japanese as Clinical Markers for Discrimination between Specific Language Impairment and Typically Developing Children

Purpose: Nonword repetition (NWR) tasks could be used to discriminate between specific language impairment (SLI) and typically developing children (TDC) in English-speaking children. I propose to use NWR task in Japanese language and to establish a standard to discriminate SLI at a younger age. Method: Participants were children who had attended nursery school. The 117 subjects ranged in age from 3-years, 1-month to 6-years, 1-month, and were thought to be TDC, but may have included some with SLI. They were examined to investigate their ability in phonological working memory. As well, an NWR task in Japanese was compared with different tasks associated with language development testing. These included a Picture Vocabulary Test (PVT), naming, digit span, and articulation errors. Results: The NWR task correlated with age, vocabulary age, naming, and digit span. The group less then one-and-a-half-years-old showed individual variations. The mean percentage of correct answer in the NWR task of four syllables comprised almost 70% by age three-and-a-half. In addition, the subjects made phoneme errors only with one-syllable words, those being the least significant, i.e., replacing /t/ with /k/. Conclusion: The results suggested that a Japanese NWR task is a useful clinical marker in discriminating between SLI and TDC