Статьи журнала - Siberian Aerospace Journal
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Статья научная
In the production of space rocket technology, electrochemical processes are used, as a result there is pollution of sewage by metal ions. The strict requirements of environmental authorities do not allow sewage, containing metal ions with concentration exceeding the maximum permissible values, to be discharged directly into reservoir or sewers. The greatest difficulties are caused by the purification of water from hexavalent chromium. The proposed methods for purifying from hexavalent chromium, electrocoagulation method, galvanocoagulation method, sorption methods, combined methods, have some disadvantages, such as: significant energy consumption, significant consumption of soluble metal anodes, passivation of the anodes, need for large excesses of reagent (iron salts), large amounts of precipitate and the complexity of its dehydration, high cost and scarcity of sorbents, high consumption of reagents for the regeneration of sorbents, and others. This work shows equipment for experiments, including a diaphragm electrolyzer with a coaxial arrangement of electrodes. Formulas for calculating the chromium ions flux due to migration and diffusion are presented. The difference between the calculated amperage from the practical one is 25 %, and the theoretical degree of purification from the real one is 4 %, which confirms the effectiveness of the proposed cleaning method. The concentration of chromium anions was determined by atomic absorption spectroscopy. The degree of purification of water from chromium ranged from 84 to 96 %. The highest degree of purification (96 %) was obtained with an electrolysis duration of 29 minutes.
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m-aperiodic words on three-letter alphabet
Статья научная
The work is devoted to the study of sets of aperiodic words over a finite alphabet. The set of aperiodic words can be considered as a dictionary of some finite formal language. The existence of infinite words in two-letter or three-letter alphabets that do not contain subwords that are third powers or, respectively, squares of other words was first discovered more than a hundred years ago. S.I. Adyan in 2010 constructed an example of an infinite sequence of irreducible words, each of which is the beginning of the next and does not contain word squares in a two-letter alphabet. S.E. Arshon established the existence of an n-digit asymmetric repetition-free sequence for an alphabet of at least three letters. In the monograph by S.I. Adyan proved that in an alphabet of two symbols there exist infinite 3-aperiodic sequences. In the works of other authors, generalizations of aperiodicity were considered, when not only the powers of some subwords were excluded. In the monograph by A.Yu. Olshansky proved the infinity of the set of 6-aperiodic words in a two-letter alphabet and obtained an estimate for the number of such words of any given length. The author previously considered the case of a three-letter alphabet only in the case of 6-aperiodic words. In this article, we prove the infinity of the set of m-aperiodic words in the three-letter alphabet at m 4 and obtain an estimate for the set of such words. The results can be applied when encoding information in space communications.
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Статья научная
Recently, there has been an increase of interest in satellite orbit raising using electric propulsion subsys-tems. Theoretic analyses and practical experience demonstrate that while orbit raising to the geostationary orbit (GEO) via a transfer orbit is feasible, it requires a certain amount of time due to the thrust of onboard electric thrusters being low (40-300 mN) and thus incomparable with that of propulsion systems of liquid propellant thrusters (22-400 N). Due to low thrust, orbit raising by electric thrusters is time-consuming. However, the associated increase in mass to GEO may counterbalance the long duration of satellite commis-sioning. Calculations demonstrate a potential added satellite mass on GEO of up to several hundred kilo-grams with orbit raising duration of about 6 months. In particular, with satellite mass not exceeding 2500 kg, coupled launch is possible using existing launch vehicles. ISS took into consideration the positive results ob-tained with Express-AM5, and Express-AM6 satellites to design the Express-80 and Express-103 with orbit raising in mind. Such approach allowed for a coupled launch on the Proton-M carrier rocked with a Breeze-M upper stage, and a twofold launch cost saving. To increase thrust during orbit raising and decrease its du-ration, coupled thruster operation in high thrust mode was implemented. The resulting total mass on GEO increase constituted over 700 kilograms with maneuver duration of up to 158 days. This allows performing coupled launches of heavier satellites with orbit raising by means of electric propulsion in a feasible timeframe.
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