Temperature compensation of fluorescence intensity-based fiber-optic oxygen sensors using modified Stern–Volmer model

In practical sensing applications, temperature effects are of particular concern, and hence it is necessary to develop the means to correct the fluorescence intensity measurement in accordance with the working temperature. Accordingly, this study develops a modified Stern–Volmer model to compensate for the temperature drift of oxygen concentration measurements obtained using fiber-optic sensors. The oxygen sensors considered in this study are based on teraethylorthosilane (TEOS)/n-octyltriethoxysilane (Octyl-triEOS) or n-propyltrimethoxysilane (n-propyl-TriMOS)/3,3,3-trifluoropropyltrimethoxysilane (TFP-TriMOS) composite xerogels doped with platinum meso-tetrakis(pentafluorophenyl)porphine (PtTFPP).

The experimental results are fitted to the modified Stern–Volmer model in order to compute suitable values for a temperature compensation coefficient at different working temperatures. It is found that the proposed temperature compensation method reduces the difference in the oxygen concentration measurement for working temperatures in the range of 25–70 °C as compared to data without compensation. The linearity and sensitivity of PtTFPP-doped n-propyl-TriMOS/TFP-TriMOS sensor are better than PtTFPP-doped TEOS/Octyl-triEOS sensor for working temperatures in the range of 25–70 °C.

The proposed approach could provide a straightforward and effective means of improving the accuracy of fiber-optic oxygen sensors if a variable attenuator is designed according to the temperature compensation coefficient. Thus, the fiber-optic oxygen sensor with a variable attenuator could work in a broad temperature range without using a temperature sensor.     

Synthesis of an active vibrational-protection system

The synthesis of active vibrational-protection systems is considered for the example of a spring in longitudinal-transverse flexure whose static force-displacement characteristic corresponds approximately to a cubic parabola. The operational characteristics and parameters of a pneumatic damper introduced in a vibrational-protection system are determined.     

System for the creation of complex impact loads

Existing systems for the creation of impact loads are modified by adding vibrations in tests of electronic equipment, without changing the basic operating conditions.     

Assessment of human physchophysiological states based on methods for heart rate variability analysis

We investigate certain parameters that characterize heart rate variability, as well as combinations of these parameters in terms of assessing their information value for regulating the current psychophysiological state of an operator during a mental stress test. An algorithm has been developed and optimized for dynamic assessment of an operator??s psychological stress level and the stability of his psychophysiological state.     

Solid-Fuel Combustion in the Sintering of Siderite Ore

Two technologies are considered for the preparation of solid fuel used in sintering: crushing with portions of roasted siderite ore whose strength is less than that of the fuel; or crushing of the fuel alone and subsequent mixing with the ore portions. On the basis of derivatographic data, kinetic equations are written for the high-temperature combustion of coke fines in a fuel–ore mixture obtained by the two methods. The most flammable fuel fraction in sintering is established. The results indicate that crushing of the fuel mixed with weaker additives is more effective in terms of decreasing the content of fines in the fuel and hence intensifying the combustion of large pieces.     

Quality of bulk-quenched rail after double tempering

Repeated tempering of bulk-quenched rail reduces the residual stress without significant change in the mechanical properties and hardness of the metal. Double tempering with optimal cold straightening is suitable for the manufacture of rail that is resistant to corrosion-fatigue cracks.     

Production of superpearlitic rail

Means of extending rail life are considered: optimizing the chemical composition of the steel; eliminating nonmetallic inclusions by vacuum treatment; reduction and modification of the steel; and optimization of heat treatment to attain the required required linearity, hardness, and mechanical properties.