Catalytic epoxidation of olefins in the presence of a vanadyl porphyrin complex

It was found that vanadyl porphyrin complexes synthesized from petroleum metal porphyrin concentrates stimulated epoxidation during the olefin oxygenation process. The yields of obtained oxiranes turned out to be 38–75%, depending on the olefin structure. An epoxidation mechanism that suggests the formation of a protonated dioxygen adduct as an intermediate during oxygenation of olefins in the presence of vanadyl porphyrin complexes was proposed. An analogy is drawn between the epoxide formation reaction upon the catalytic oxygenation of olefins and the Prilezhaev reaction.     

Electrical and photoelectric properties of electrochemically fabricated SnO2/Cd0.4Zn0.6S/CdTe solar cells

Solar cells based on SnO₂/Cd_0.4Zn_0.6S/CdTe heterostructures are fabricated by electrochemical deposition, and the dependences of their electrical and photoelectric properties on the thermal annealing conditions are studied. It is shown that thermal annealing reduces the tunnel currents by almost two orders of magnitude. The best conditions of thermal annealing are determined (t = 300°C and τ = 9 min). These conditions provide the highest photosensitivity of the heterostructures under study (I _sc ≈ 21.2 mA/cm², U _oc ≈ 813 mV, and η = 14.7%).     

A fiber optic phase modulator with an optical frequency shift of up to 20 GHz

A fiber optic phase modulator is described in which the phase of a light wave traveling in an optical fiber is modulated by a composite electromechanical resonator with Q≌1000. The instantaneous frequency of the wave at the modulator output varies according to a harmonic law. The interval of tuning of the instantaneous light wave frequency achieved in the experiment is 20 GHz, which corresponds to a modulation index of ≌10⁶. It is demonstrated that a maximum value of the frequency tuning range is determined by the elastic limit of the resonator material.     

Electroplating of Lead Coatings Containing Small Amount of Tellurium

Plating conditions and some physicochemical properties of lead-tellurium coatings from a fluoboric acid bath are studied. The electroplates exhibit high microhardness, and a corrosion resistance in sulfuric acid media of 2–3 times that of pure electrolytic lead.     

Dynamic characterization and modification of dynamic properties of a micro scanner

Micro electro mechanical systems (MEMS) are used in many application areas in different disciplines and took their place among the most promising technologies. The performance of such systems is primarily related to their dynamical characteristics. This study presents the dynamic characterization techniques that are used to identify the modal parameters of a MEMS device and the methods that can be implemented to change its dynamic response. An electrostatic scanner is chosen as the case study to demonstrate the developed methodologies. Initially, the micro scanner is characterized using experimental modal analysis techniques to obtain frequency response function, modal damping, resonance frequencies, and mode shapes. Then, velocity and position feedback control loops are implemented to the scanner system to alter the damping and stiffness characteristics. A closed-loop Simulink model of the scanner is developed to verify the experimental measurements. Several curve fitting methods are used in order to have an accurate representation of the scanner system. Using the model, the influence of both position and velocity feedback on the effective damping, resonance frequency and the transient behavior of the scanner is investigated. The stability limits of the scanner under velocity feedback are also studied via numerical simulations. Based on the experimental and simulation results, the methodology developed in this study proves itself to be very efficient to alter the dynamical characteristics of the MEMS structures and it can be easily adapted to other MEMS applications.     

Experimental reprocessing of waste cast-iron chips to the powder form

We have studied the possibility of producing powders from gray cast-iron chips formed during the production of home air conditioners. The particle morphology, structure, physicotechnical, mechanical, and antifriction properties of the cast iron powder are studied and compared to those of powdered iron. It is shown that the sample obtained from the cast-iron powder have worse mechanical properties than the samples prepared from iron but they have better antifriction properties than the latter.Bakkonditsioner Scientific-Industrial Complex. Translated from Poroshkovaya Metallurgiya, No. 2(362), pp. 93–98, February, 1993.     

Thermal-conductivity coefficients of six liquid aromatic hydrocarbons

Using experimental and data, equations are developed for six aromatic hydrocarbons which describe within the limits of experimental accuracy over the temperature range 298–573°K at pressures up to 500 bar.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 34, No. 3, pp. 465–469, March, 1978.     

Synthesis of N-substituted derivatives of arylsulfonyl hydrazides and their investigation as additives for lubricating oils

The reaction between arylsulfonyl chlorides and hydrazine has been studied, and it has been found that in the presence of excess hydrazine, the bis-derivatives are produced in small amounts along with monoarylsulfonyl hydrazides. It has been revealed that the reaction of monosulfonyl hydrazides with alkyl bromides in the presence of a base results only in N-alkylation of the sulfamide nitrogen, although the reaction in the presence of HCl proceeds at the amine group with the formation of quaternary ammonium salts. A method for the preparation of sulfonyl hydrazides by oxidation of N-alkyl sulfamides in the presence of iodine has been developed. Some arylsulfonyl hydrazide derivatives have been examined as antioxidant, antirust, and antiwear additives. These sulfonyl hydrazides also exhibit a high bactericidal and fungicidal activity.