Abstract: The invention relates to a method of determining the complex impedance Z(fm) of a non-steady electrochemical system, comprising the following steps consisting in: bringing the system to a selected voltage condition and applying a sinusoidal signal with frequency fm thereto; immediately thereafter, measuring successive values for voltage and current at regular time intervals ?T; calculating the discrete Fourier transforms for voltage (E(f)) and current (I(f)), the voltage transform being calculated for the single frequency fm of the sinusoidal signal and the current transform being calculated for frequency fm and for two adjacent frequencies fm?1 and fm+1 on either side of frequency fm; and calculating the impedance using the following formula: Z(fm)=E(fm)/I*(fm), wherein I* denotes a corrected current such that Re[I*(fm)]=Re[I(fm)]?{Re[I(fm+1)]+Re[I(fm?1)]}/2, Im[I*(fm)]=Im[I(fm)]?{Im[I(fm+1)]+Im[I(fm?1)]}/2.

Abstract: The subject of the invention is a substrate provided on at least part of at least one of its faces with a coating having photocatalytic properties, containing photocatalytic titanium oxide, especially crystallized in the anatase form, in an essentially mineral binder comprising at least one semiconducting metal oxide.

Abstract: In this process, during at least one phase of the treatment cycle, the gas outflow is increased or decreased locally in at least one marginal region of the packing. Application to drying/CO2 removal of atmospheric air intended to be distilled, or to the separation of gaseous mixtures by pressure modulated adsorption.

Abstract: In this process, during at least one phase of the treatment cycle, the gas outflow is increased or decreased locally in at least one marginal region of the packing.

Abstract: The device comprises an adsorber (1) and three outlet capacities (2-4), first (8, 9) and second (10, 11) structure to establish bidirectional communication between the adsorber and the elution capacity (2) and the repressurization capacity (3), respectively, and third structure (14A, 15; 16) to establish unidirectional communication from the adsorber to the production capacity (4).

Abstract: The device comprises an adsorber (1) and three outlet capacities (2-4), first (8, 9) and second (10, 11) structure to establish bidirectional communication between the adsorber and the elution capacity (2) and the repressurization capacity (3), respectively, and third structure (14A, 15; 16) to establish unidirectional communication from the adsorber to the production capacity (4).

Abstract: A separation process, involving an adsorber containing at least one adsorbent with an inlet and outflow, involves the following stages of the cycle:--stage I, repressurization from the low pressure of the cycle;--stages II and III during one of which the high pressure of the cycle is reached; and stage IV, depressurization/purging, during which the low pressure of the cycle is reached. Each stage (I to IV) involves a fixed gas flow (F) at one end of the adsorber and a free gas flow (.lambda.) at the other end of the adsorber, the fixed flows (F) addressing the inlet (E) and outlet (F) ends of the adsorber from one stage (I to IV) to the next. The process is particularly applicable to the production of oxygen from air.

Abstract: In a process for separating a gas mixture in a pressure swing adsorption device comprising an adsorber, two outlet vessels and a rotary machine at the inlet, the rotation of the rotary machine is reversed during the first depressurization step (c-d) then during the first repressurization step (g-h), so that these first steps are each broken down into two sub-steps in which the inlet for the adsorber successively experiences two opposite flows, whereas the outlet of the adsorber experiences a flow, respectively leaving or entering, of constant direction. The process is particularly useful in the production of oxygen from air.

Abstract: The apparatus for the separation of a gas mixture by pressure swing adsorption (PSA) comprises at least one adsorber A and a first vessel T which can be selectively connected to the adsorber in order temporarily to store the gas which is extracted from the adsorber and reintroduced into it during a cycle, the vessel T having a fixed free internal volume V, a vertical main direction of height h, with the relationship 25.ltoreq.h.sup.3 /V.ltoreq.150, and the gas fraction entering and leaving the vessel T at its lower part, and remaining therein for a time which does not exceed 300 seconds. The apparatus is useful in the production of oxygen or hydrogen.

Abstract: Process for treating a gas mixture by pressure swing adsorption wherein for each adsorber (1), the duration (T.sub.R) of the countercurrent recompression step is much less than that (T.sub.D) of the cocurrent decompression step. The process is particularly useful in the production of oxygen from atmospheric air.

Abstract: PSA process for the separation of nitrogen from a gaseous mixture containing nitrogen by selective adsorption of nitrogen from the gaseous mixture in an adsorbent mass with cyclic pressure variations. At least one nitrogen adsorption phase is carried out at high pressure and at least one nitrogen desorption phase is carried out at low pressure. The adsorbent mass is arranged in a rotating adsorber and at least 50% of the adsorbent mass is constituted by a zeolite exchanged with lithium by more than 50%.

Abstract: The present invention relates to copolymers, to a process for their preparation and to their use for the production of ionically conductive materials. A copolymer according to the invention consists of monomer units corresponding to the formula --CH.sub.2 --O--CHR--CH.sub.2 O (I) and monomer units corresponding to the formula --CH.sub.2 --CHR'--O-- (II), in which: R denotes a hydrogen atom, a linear or branched alkyl radical containing from 1 to 8 carbon atoms or a radical CH.sub.3 (--O--CH.sub.2 --CH.sub.2).sub.n --O--CH.sub.2 --, in which 1.ltoreq.n.ltoreq.10; R' denotes an aliphatic radical containing an unsaturation which can be polymerized by a radical route and inert in the conditions of cationic polymerization. The copolymers can be obtained by cationic polymerization of the appropriate oxirane and dioxolane. Application to the production of ionically conductive materials.

Abstract: In a "vacuum" type cycle, the depressurization of a first adsorber at the high pressure of the cycle is effected by placing it in communication with the outlet of a second adsorber at the low pressure of the cycle. This communication takes place simultaneously with countercurrent pumping in a first stage for the second adsorber and in a second stage for the first adsorber, the recompression to the high pressure of the cycle being effected by production gas. Used for the production of oxygen from air.

Abstract: In a pressure-swing adsorption-type gas separation unit, a distinct intermediate gas passageway is formed between a first water retaining bed (A) and a second separating adsorbent bed (B), a controlled heat flow being supplied to prevent the formation of a very cold area between both beds. The unit is particularly useful in the production of oxygen from air.

Abstract: A rotary device including a plurality of vertical prismatic sectors mounted on a first annular plate comprising two arrays of gas passages which communicate with the outer and inner collectors of respective sectors, and interacting with a second plane annular plate on a housing defining a set of inner chambers. The second plate comprises two concentric arrays of apertures which communicate with corresponding chambers in the set of chambers, and are spread out along the path of the two gas passage arrays of the first plate. The device is particularly useful for producing oxygen.

Abstract: According to this process, compressed air is cooled and purified by adsorption by passing same in a first direction through a mass of adsorbent material (8), then a residual gas from the distillation apparatus passes in opposite direction through this mass to regenerate same. During the entire regeneration, the residual gas is at a constant regeneration temperature which is between the temperature of the air entering into the mass of adsorbent material and at a temperature which is about 50.degree. C. above this temperature.

Abstract: The air distillation double column (1,2) includes an apparatus for vaporizing oxygen and condensing nitrogen which comprises on one hand a running type main heat exchanger (7) which is partially immersed during stoppage of the equipment and on the other hand an auxiliary heat exchanger (20) which alone is responsible for liquid vaporization when the equipment is restarted.

Abstract: Process for measuring the forces between the working rolls of a roll stand, in which several extended load cells (51, 52, 53) placed between the working rolls (13, 14) are aligned in a plane passing through the axes of these rolls and distributed symmetrically with respect to the central plane of the stand, a pressing force is exerted on the balances by adjusting systems (27, 28), the value of the forces exerted simultaneously on each load cell is read and the values of the resulting pressing forces are deduced. Preferably, a device comprising two half-shell shaped pieces of malleable material such as copper is used, and this holds the load cells in alignment and serves as a bearing plate which can be cold-rolled. The process is applied to the adjustment of the gauges of a roll stand for flat products and to the precise determination of the yield curves.

Abstract: A proximity detector is provided with an oscillating circuit generating cyclically an unsustained pseudo-oscillation. The detector includes a processing circuit having a comparator which compares the relaxation voltage of the oscillating circuit with a predetermined threshold and a logic circuit which generates control pulses with low duty ratio for a switch in series with the oscillating circuit and also an output signal as a function of the measurement pulses delivered by the comparator. The closure duration of the switch is substantially equal to half the pseudo-oscillation period.

Abstract: The air distillation double column (1,2) includes an apparatus for vaporizing oxygen and condensing nitrogen which comprises on one hand a running type main heat exchanger (7) which is partially immersed during stoppage of the equipment and on the other hand an auxiliary heat exchanger (20) which alone is responsible for liquid vaporization when the equipment is restarted.