112 research outputs found
Stimulated Raman gain spectra measured by a cavity-ringdown technique
No full textWe report a novel form of high-resolution coherent-Raman spectroscopy which detects stimulated Raman gain effects using a cavity-ringdown technique. This is demonstrated by recording molecular rovibrational Raman spectra of methane gasFlorian V. Englich, Yabai He, and Brian J. Or
Continuous-wave cavity-ringdown detection of stimulated Raman gain spectra
No full textCavity ringdown (CRD) spectroscopy, with its high sensitivity, provides a novel way to perform continuous-wave (cw) stimulated Raman gain (SRG) spectroscopy, rather than by conventional optically detected coherent Raman techniques. Tunable cw laser light at ∼ 1544 nm is used to probe ringdown decay from a rapidly-swept, high-finesse optical cavity containing a gas-phase sample of interest and itself located inside the cavity of a cw single-longitudinal-mode Nd:YAG ring laser operating at ∼ 1064.4 nm. This approach is used to measure cw SRG spectra of the ν 1 fundamental rovibrational Raman band of methane gas at ∼ 2916.5 cm-1. The resulting SRG-CRD resonances have ringdown times longer than in the off-resonance case, in contrast to the usual shorter ringdown times arising from absorption and other loss processes. Previously reported noise-equivalent sensitivities have been substantially improved, by using a second ringdown cavity to facilitate subtraction of infrared-absorption background signals. Moreover, by employing a ringdown cavity in the form of a ring, the SRG-pump and CRD-detected Stokes beams can co-propagate uni-directionally, which significantly reduces Doppler broadening. © 2008 Springer-Verlag.F.V. Englich, Y. He and B.J. Or
Multi-wavelength, rapidly swept continuous-wave cavity ringdown spectroscopy, applied to sensing of greenhouse gases
No full textThe greenhouse gas molecules CH4, CO2, and H 2O are detected by using a cavity ringdown laser spectrometer with rapidly swept optical cavity and multi-wavelength coherent radiation. This sensitive portable instrument is applicable to environmental monitoring. ©2009 Optical Society of America.Yabai He, Ruifeng Kan, Florian V. Englich, Wenqing Liu and Brian J. Or
Photoinduced electron transfer based ion sensing within an optical fiber
No full textA supplementary file is also included.We combine suspended-core microstructured optical fibers with the photoinduced electron transfer (PET) effect to demonstrate a new type of fluorescent optical fiber-dip sensing platform for small volume ion detection. A sensor design based on a simple model PET-fluoroionophore system and small core microstructured optical fiber capable of detecting sodium ions is demonstrated. The performance of the dip sensor operating in a high sodium concentration regime (925 ppm Na+) and for lower sodium concentration environments (18.4 ppm Na+) is explored and future approaches to improving the sensor’s signal stability, sensitivity and selectivity are discussed.Florian V. Englich, Tze Cheung Foo, Andrew C. Richardson, Heike Ebendorff-Heidepriem, Christopher J. Sumby and Tanya M. Monr
Vergelijking van de bereidingswijzen van 60 gew.% en 80 gew.% salpeterzuur
No full textDocument(en) uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science
Mandibular kinematics in dentofacial deformities before orthognathic surgery
No full textAIM: Changes in facial morphology may cause disturbances in stomatognathic functions. The aim of the current investigation was to quantitatively assess the three-dimensional condylar paths during standardized mandibular movements in patients with dentofacial deformities before orthognathic surgery and in healthy subjects.
METHODS: Patients with dentofacial deformity were divided in two groups: DG-II (n = 15 with class II, mean age 26.3 years) and DG-III (n= 15 with class III, mean age 26.2 years), with 3 men and 12 women each, were assessed during the preoperative orthodontic treatment. Fifteen healthy young adults, paired for age and sex, were selected for control group. Mandibular kinematics were recorded during maximum mandibular border movements: mouth opening (MMO) and closing, lateral excursions and protrusion, using an infrared optoelectronic 3D-motion analyzer (BTS SMART System), with a 500 Hz sampling rate.
RESULTS: Patients and healthy subjects had similar age (1-way ANOVA, p≥0.05). The DG-II showed larger laterotrusion asymmetry than CG (Table 1). At MMO, the percentage of mandibular movement explained by condylar rotation was larger in the DG-III than DG-II (2-way ANOVA, p=0.001; Bonferroni post-hoc test, p=0.045, Figure.1).
CONCLUSION: The outcomes suggest that the proposed method could be a useful diagnostic tool to detect altered function in DG patients before orthognathic surgery. ACKNOWLEDGEMENT: Provost’s Office for Research of the University of São Paulo.
*The first author received a scholarship from CNPq (Science without Borders), Brazil.
Table 1: Kinematics indices of mandibular motion, mean±SD, 1-way ANOVA.
Measure
Control
DG-II
DG-III
p-value
Mean
SD
Mean
SD
Mean
SD
Maximum opening – MMO (mm)
47.8
4.0
44.8
5.5
46.5
7.2
0.360
MMO deviation (mm)
2.7
1.1
3.6
1.6
3.4
2.3
0.358
Maximum laterotrusion
9.7
2.1
8.9
1.7
8.1
1.7
0.068
Laterotrusion asymmetry
0.7*
0.7
2.6*
2.6
1.1
1.1
0.011
Maximum Protrusion
7.7
1.7
7.4
1.6
6.5
2.0
0.196
*=Bonferroni post-hoc test, p=0.014.
Figure 1: Percentage of mandibular rotation during mouth opening and closin
The Aero-Hydrodynamic Characteristics of Yachts Sailing Upwind in Waves
No full textA common practice during the design of a sailing yacht is to assume an ideal environment. The wind is constant in intensity and direction and the sea is calm. In this situation, an equilibrium between the aerodynamic and hydrodynamic forces and moments can be found. The equations of equilibrium are thus solved to find the best setup (combination of sails, sail trim, etc.) in order to achieve the maximum boat speed. This procedure is the core of a 'traditional' Velocity Prediction Program (VPP), which was first introduced in 1976. Since then many improvements have been made and nowadays VPPs are capable of dealing with the most diverse designs. However, in nearly forty years of life, the nature of these programs has not changed and, still, important dynamic effects caused by the real environment, are not taken into account. Investigating the performance of a yacht taking into account these effects, is far from easy. Indeed, the equations of equilibrium should be replaced by the more complicated equations of motion which need to be solved in the time domain. However, in recent years, the dynamic characteristics of a yacht sailing in waves and shifting winds (real environment) have become a more popular topic in the sailing yacht community. In the wake of the increasing interest towards this subject, the present work aims to investigate some important dynamic aspects. The effect of the surge motion and of the heeling angle on the motions of heave and pitch, and on the mean added resistance, are studied by means of towing-tank tests. These are performed on two models of series 4 of the Delft Systematic Yacht Hull Series. Then, time-domain simulations are performed to study the effect of a pitch-induced oscillating aerodynamic force on the seakeeping of yachts sailing upwind in waves. The aerodynamic force is calculated using a quasi-steady as well as an unsteady method, whereas the hydrodynamic part of the problem is tackled using a strip-theory program which is capable of considering asymmetric hull shapes (e.g. hulls with a heeling angle). The results show that surge has a small influence on the motions and on the mean added resistance alike. The heeling angle on the other hand, prove to have a large effect on the seakeeping of the models. This effect can be qualitatively predicted by the strip-theory program, although the trend is not always correct. Finally, in same cases, the aerodynamic force significantly affects the pitch and heave motions and this results in a considerable reduction of the added resistance in waves.Ship Hydromechanics and StructuresMaritime and Transport TechnologyMechanical, Maritime and Materials Engineerin
Stofoverdrachtsproblemen in geroerde gas-vloeistof-vast systemen
No full textApplied SciencesKramers Laboratorium voor Fysische Technologi
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