Abstract: A seal assembly for a rotary machine. The seal assembly includes a rotor and a stator. The rotor is rotatable about a rotational axis and has a rotor seal face. The stator has a stator seal face. The stator seal face is positioned opposite the rotor seal face and faces the rotor seal face with a gap therebetween. A portion of one of the rotor and the stator is formed of (i) a shape memory alloy or (ii) a first metal and a second metal with the second metal having a coefficient of thermal expansion different from the first metal. The seal assembly is characterized by a seal clearance compliance ratio (SCCR) from 20% to 90%.

Abstract: A centrifugal compressor includes a first stage and a second stage. At least one of the first stage and the second stage includes an impeller and a shroud spaced from the impeller and configured to guide a fluid flow through the impeller. The shroud is selectively moveable between an engaged position and a disengaged position.

Abstract: An ultrasound imaging system includes a thermally conductive frame and a number of electronic components and a display that are sealed within the frame. The frame further includes a plenum extending through the frame with surfaces that are thermally coupled to the electronic components and the display. An active cooling mechanism, such as one or more fans, moves air through the plenum to remove heat generated by the electronic components and display. The plenum is environmentally sealed so that moisture, dust, air or other contaminants drawn into the plenum do not contact the sealed electronic components and display in the frame.

Abstract: A centrifugal pump for lifting clean water or water with suspended solids includes a hollow body having a front opening, a volute with a delivery port, and an impeller accommodated in the body and designed to be coupled to a motor, with blades tips substantially coplanar at an annular peripheral area. A cover of the front opening includes a flange, an annular wear plate, rigidly joined to the flange and located at a predetermined axial distance from an annular peripheral area of the impeller, and an adjustment system, mounted onto the flange and accessible from the outside, to controllably adjust the axial distance of the wear plate, and to both calibrate the axial position of the wear plate and lock the wear plate in the calibrated position. A method of adjusting the axial distance of the wear plate from an impeller in a centrifugal pump.

Abstract: A hydraulically powered rotary actuator is described including: a hydraulic linear actuator which is moveable in both directions between a retracted position and an extended position; a clutch device which is operable between an engaged condition and a disengaged condition; and a rotary output member; wherein the linear actuator is coupled to the rotary output member by way of the clutch.

Abstract: A seal, for use with pump casing elements that are adjustable relative to each other, includes an annular band and a resilient annular flange oriented at a non-perpendicular angle to a first surface of the annular band such that the seal, in use, is able to provide greater adjustment between the adjustable pump elements while maintaining a reliable seal between the pump elements.

Abstract: A turbine has a turbine housing with a receiving region, a turbine wheel which is disposed in the receiving region, a duct formed by the turbine housing, through which exhaust gas of an internal combustion engine can flow and which opens into the receiving region, and a tongue slide which has a tongue which is assigned to the duct and which can be displaced relative to the turbine housing about the rotational axis such that a flow cross section of the duct can be set. The exhaust gas which flows through the duct can be guided via the flow cross section into the receiving region and can be fed to the turbine wheel. The turbine is configured as a half-axial flow turbine in which a respective flow direction runs obliquely with respect to the axial direction and obliquely with respect to the radial direction of the turbine wheel.

Abstract: A turbine engine that includes a rotor assembly including a plurality of rotor blades, an outer case positioned radially outward from the plurality of rotor blades, and an annular ring coupled to the outer case and positioned between the plurality of rotor blades and the outer case. The annular ring is configured to restrict thermal contraction of the outer case towards the plurality of rotor blades.

Abstract: A gas turbine includes: a first cavity inside a stationary body and supplied with cooling air; a second cavity between the stationary body and a rotating body; a first cooling passage between the first and second cavities and having a swirl flow guide nozzle therein by which the cooling air of the first cavity is supplied to the second cavity while being swirled along a rotation direction of the rotating body; a second cooling passage in the rotating body, in communication with the second cavity, and supplied with the cooling air of the second cavity; and a flow regulating passage, different from the first cooling passage, between the first cavity and the second cavity and through which the cooling air is supplied from the first cavity to the second cavity, wherein the flow regulating passage has a flow regulator for regulating a flow rate of the cooling air.

Abstract: A system for modulating turbine blade tip clearance is provided. The system may comprise an actuation control system having at least one actuator configured to modulate turbine blade tip clearance. Each actuator may comprise a solid-state motion amplification device such as a flextensional actuator. Each actuator may be in operable communication with a blade outer air seal (BOAS) segment or a BOAS mounting block. The actuators may be configured to move the BOAS segment and/or the BOAS mounting block in a radial direction from a first position to a second position to control tip clearance.

Abstract: A system for modulating turbine blade tip clearance is provided. The system may comprise an actuation control system having at least one actuator configured to modulate turbine blade tip clearance between a turbine blade tip and a blade outer air seal (BOAS). Each actuator may be coupled to the BOAS. Each actuator may comprise a solid-state motion amplification device such as a flextensional actuator. The actuators may be configured to move the BOAS in a radial direction from a first position to a second position to control tip clearance.

Abstract: According to one aspect, an apparatus includes a first member that has a first aperture and a second member adjacent to the first member and having a second aperture extending between opposed first and second faces of the second member and aligned with the first aperture to define a combined aperture that has a longitudinal extent. The second aperture is defined by a surface that has a portion having an extent transverse to the longitudinal extent. The apparatus further includes at least a portion of a fastener disposed in the combined aperture. The fastener has a first end proximal the first member and a second end proximal the second member and includes a first retaining member in contact with the first member, a second retaining member in interfering relationship with the portion, and a third retaining member in contact with the second face.

Abstract: A method for the positioning of a cover disk with respect to an open impeller of a pump arranged in a pump housing. An adjustment bolt is first screwed so far into a threaded bore of the cover disk until it comes into contact with the pump housing. An identifier is subsequently applied which indicates a position of a first marking of the adjustment bolt. The adjustment bolt is then screwed in further until a second marking reaches the identifier. The described steps are repeated for at least one further adjustment bolt.

Abstract: A turbine housing of an exhaust-gas turbocharger may include at least two spiral-shaped exhaust-gas channels separated from one another via a partition. The at least two channels may be delimited radially to the outside by the turbine housing and radially to the inside by at least two spiral tongues. A first spiral tongue may be associated with one of the channels and a second spiral tongue may be associated with the other of the channels. The at least two spiral tongues may extend in opposite directions away from the partition in a direction towards the turbine housing. According to an example, the at least two spiral tongues may be configured such that, under an increasing thermomechanical loading, the first spiral tongue fails before the second spiral tongue.

Abstract: An adjustment assembly for pump casing of a pump, the pump casing including a main part and a side part having a main axis and a side wall section extending laterally with respect to the main axis. The adjustment assembly is operable to cause relative displacement between the side part and the main part of the pump casing. The adjustment assembly includes a drive device and an actuator which can be activated externally of the pump, the drive device being operable to cause the relative displacement of the side part in response to activation of said actuator, the relative displacement capable of being a combination of axial and rotational movement.

Abstract: A centrifugal pump for a slurry combines design changes with respect to conventional configurations that produce quasi-laminar flow and materially extend the life of the casing. The cutwater clearance of the casing is increased to a range of 0.20 to 0.25 times the diameter of the impeller. The casing includes a redesigned removable annular liner with a diameter increased to at least 1.15 times the diameter of the impeller. The pump preferably also has an axially adjustable wear ring with a diameter increased such that it extends by at least 10% over the diameter of the area of interface between the wear ring and the impeller.

Abstract: A casing for a turbine engine compressor, including: cavities in a thickness of the casing, extending in parallel to one another from an inner face of the casing along a circumference thereof, the cavities not being in communication with one another. The cavities, which are elongate and extend along a main direction of orientation between two side walls, are closed upstream and downstream by upstream and downstream faces respectively, and an upstream border and a downstream border are formed at the intersections between same and the inner face of the casing. The upstream border of the cavities takes a form of a wavy line including at least two alternate undulations over a length thereof between the side walls.

Abstract: A mechanical coolant pump for an internal combustion engine includes a pump rotor wheel comprising rotor blades configured to pump a coolant radially outward. A non-rotating ring of pump stator blades is configured to encircle the pump rotor wheel. At least one of the pump stator blades is a static blade. At least one of the pump stator blades is a pivotable blade configured to pivot about a pivot axis arranged within the pivotable blade.

Abstract: In a pump arrangement, each adjusting screw has first and second end portions, a third intermediate raised portion, and a fourth portion to allow each adjusting screw to be rotated clockwise/counterclockwise. Each first end portion passes through a suction liner aperture so left-handed threads couple to a respective left-handed seal ring aperture. Each second portion passes through a suction half casing aperture so the fourth portion can be accessed to allow clockwise/counterclockwise rotation of each adjusting screw. Each adjusting screw rotates clockwise and moves until the third portion pushes against the suction half casing, so the screw stops moving and the seal ring moves away from the suction liner as the screw is rotated clockwise, or rotates counterclockwise and moves until the third portion pushes against the suction liner, so the screw stops moving and the seal ring moves towards the suction liner as the screw is rotated counterclockwise.

Abstract: A coupling pin for use in a pump housing, the pump housing including an outer casing and an inner pump liner, the coupling pin being suitable for locating the liner and casing relative to one another, the coupling pin including a shank and a head at one end of the shank. The head includes a cammed surface thereon which is adapted to co-operate with a follower on the liner, and a locating section on a remote or terminal end of the head which is adapted to be positioned against a seat in the outer casing when fitted. The arrangement is such that rotation of the coupling pin causes the follower to track along the cammed surface so as to cause relative movement between the outer casing and the inner pump liner.

Abstract: A fluid pump device, in particular for a medical application, is described having a compressible pump housing and rotor, as well as with a drive shaft which runs in a sleeve and on whose end the fluid pump is arranged. In order to utilize all possibilities of a space-saving arrangement of the respective pump housing of the rotor, which is compressible per se, and as the case a bearing arrangement, the mentioned elements are displaceable to one another in the axial direction compared to an operation position. In particular these elements may be end-configured by way of an axial movement of the drive shaft after the assembly.

Abstract: A method is provided for adjusting a position of a blade ring relative to a rotor in a gas turbine engine. An outer casing surrounds the blade ring and the blade ring surrounds the rotor. The method comprises: determining an amount of vertical movement needed to reposition the blade ring relative to the rotor so that the blade ring is at a desired position relative to the rotor; providing at least one torque pin assembly comprising a torque pin and a variable thickness defining structure; determining a change in the thickness of the variable thickness defining structure so as to effect the necessary vertical movement of the blade ring; changing the thickness of the variable thickness defining structure; and coupling the at least one torque pin assembly to the outer casing such that at least one torque pin engages the blade ring. A gas turbine engine is provided having structure for adjusting a position of a blade ring relative to a rotor.

Abstract: An adjustment assembly for pump casing of a pump, the pump casing including a main part and a side part having a main axis and a side wall section extending laterally with respect to the main axis. The adjustment assembly is operable to cause relative displacement between the side part and the main part of the pump casing. The adjustment assembly includes a drive device and an actuator which can be activated externally of the pump, the drive device being operable to cause the relative displacement of the side part in response to activation of said actuator, the relative displacement capable of being a combination of axial and rotational movement.

Abstract: The nacelle of the invention includes an air-inlet front section, a middle section for encasing the fan of the turbofan (7) and a rear section including means for connection to a pylon to be connected to the rigid structure or an airplane. The rear section includes a structural framework (18) having at least one aerodynamic smoothing and acoustic panel (21). The acoustic panel (21) is secured on the structural framework (18) by floating or elastic fixation means so that said acoustic panel (21) can be deformed in a direction (31) essentially centrifugal and radial relative to the turbofan (7) in the presence of overpressure air (3) in the engine compartment.

Abstract: A pump comprising a housing, an impeller within the housing defining an axis, a front head connected to the housing, a liner disposed between the front head and the impeller, and at least one actuator operatively connected between the front head and the liner to move the liner axially with respect to the impeller, the actuator being adapted for connection to an actuation system.

Abstract: A liner for an interior surface of an engine casing, comprises a number of liner panels disposed radially outwardly of a rotatable component of the engine, such as a fan blade, and the panels are mounted on the interior surface of the casing, wherein each panel is individually adjustable, such that the clearance between the panel and the rotatable component of the engine may be varied individually for each panel.

Abstract: A turbomachine casing assembly includes a first casing element locatable radially outward of one or more rotating aerofoil elements of a turbomachine, a second casing element located radially distal to the first casing element and one or more arcuate fence elements positioned between the first and second casing elements. Following impact of a detached fan blade, a radially outward movement of the first casing element causes the or each fence element to project into the air flow passing through the turbomachine.

Abstract: An arrangement for optimizing the running clearance for turbomachines of the axial type, such as turbocompressors, gas turbines, and steam turbines, in particular for compressors of stationary gas turbines, by controlling the inner diameter, which is relevant to the running clearance, of at least one stator structure that surrounds a rotor blade ring, including: the stator structure has a closed, circular inner ring, a circular outer ring that is situated concentric to the inner ring at a radial distance therefrom, and a plurality of links that integrally connect the inner ring to the outer ring, the links being circumferentially inclined at a defined angle (?) to the radial direction and distributed around the circumference of the stator structure, and the arrangement includes an adjustment device for rotating the inner ring relative to the outer ring with elastic modification of the running clearance-relevant inner diameter (D) of the inner ring.

Abstract: The present invention relates to a submersible centrifugal pump assembly comprising an impeller suspended in the end of a drive shaft, and driven in rotation relative to an impeller seat which is stationary in normal operation and which defines an axial intake for liquid to be transported by the impeller in rotation. The pump assembly is characterized in that the impeller seat is journalled in a pump housing for limited rotational movements in opposite directions of rotation relative to the pump housing, and in rotation controlled in guide means for limited linear displacements in opposite axial directions relative to the impeller.

Abstract: A clamping and support system for a turbine is disclosed. The clamping and support system may include a support bar coupled with a lower diaphragm portion of the turbine. The support bar may have a protuberance extending from a first end portion thereof that may at least partially extend into a slot formed in the lower diaphragm portion of the turbine. The clamping and support system may also include a clamping bar coupled with a second end portion of the support bar. The clamping bar may at least partially extend into a slot formed in an upper diaphragm portion of the turbine such that at least a portion of the lower diaphragm portion and at least a portion of the upper diaphragm portion are interposed between the clamping bar and the protuberance of the support bar, thereby coupling the lower diaphragm portion with the upper diaphragm portion.

Abstract: A variable inlet area turbine employs a volute with a discharge area for flow of exhaust gas carried in the volute into a turbine inlet area. A flexible dividing wall having an end is movable along a path defined adjacent the turbine inlet area and transitioning in a smooth curve into an outer wall of the volute. The dividing wall is selectively positionable by insertion and withdrawal along the path to vary the discharge area from substantially closed to substantially open.

Abstract: A guide system for translating components of an aircraft engine nacelle includes a track assembly and a slider assembly. The track assembly includes a track guide member having a track channel. The slider assembly translatably engages the track assembly. The slider assembly includes a slider body configured to be received within the track channel. The slider assembly further includes a slider arm member pivotably coupled to the slider body with a hinge joint disposed within the track channel. The slider arm member extends from the body portion and outwardly of the track assembly. Associated apparatuses are also provided.

Abstract: A system includes a gas turbine engine, a nozzle structure located adjacent to the gas turbine engine, a flexible annular seal linking the gas turbine engine and the nozzle structure, the flexible annular seal having a plurality of corrugate sections arranged about a centerline, and a connection device secured to the gas turbine engine and to the nozzle structure. The connection device is adjustable to select a length of the flexible annular seal measured along the centerline.

Abstract: The invention relates to a clearance control system for adjusting a running clearance (L) between a rotor (12) having rotor blades (10) of a turbomachine (14), especially a gas turbine, and a casing (18) that surrounds at least sections thereof and comprises at least two segments (16a-d), the clearance control system having at least one adjusting device (20), which can be coupled to at least one segment (16a-d) of the casing (18), and by means of which the at least one segment (16a-d) can be moved radially in relation to a rotational axis (D) of the rotor (12) for adjusting the running clearance (L), wherein each segment (16a-d) of the casing (18) is coupled to at least three adjusting devices (20) of the clearance control system. The invention also relates to a turbomachine (14), especially a gas turbine, as well as to a method for adjusting a running clearance (L).

Abstract: An impeller fixing mechanism is provided in a centrifugal pump for immobilizing the impeller, relative to the pump shaft and drive shaft of the pump, while effecting repairs to the pump, thereby eliminating much of the labor-intensive need for realigning the pump shaft and drive shaft and assuring accurate positioning of the impeller relative to the pump shaft. A method for effecting repairs of centrifugal pumps employs use of the impeller fixing mechanism of the invention to immobilize the impeller relative to the pump shaft, thereby facilitating the repair.

Abstract: A drive mechanism comprising a first sprocket encircled by a tensioned chain and an orbit sprocket arranged to orbit the first sprocket in response to a resynchronisation signal. The orbit sprocket is arranged to displace the tensioned chain relative to the first sprocket. The first sprocket is rotatable and is coupled to an output drive sprocket by the tensioned chain such that the first and output drive sprockets are rotatable in synchronicity, whereby the orbit of the orbit sprocket alters the relative angular orientation of the first and output drive sprockets.

Abstract: Sensors (32, 52, 72) for determining a gap between a conductive member (34, 54, 74) such as a blade in a gas turbine engine and a seal segment (31, 51) are known to use capacitive variants in order to create an electrical signal indicative of the gap width. Thermal disparities can create problems with regard to sensor aging and accuracy. By creating a sensor incorporating a metal rod (33, 53, 74) typically integrally formed or associated with the seal segment (31, 51) and coupled through inductive coupling loops (35, 36; 55, 56; 75) it is possible to create a tuned circuit with a Q value which is more stable and therefore acceptable with regard to producing more accurate results at elevated temperatures with less problems with regard to thermal disparities.

Abstract: Convex sealing bottom (10) for a twin-shaft turbine of the type comprising a series of convex disks constrained to each other by means of a series of pins, each disk of said disks comprises an outer shaped edge which is engaged with a corresponding annular surface (71) of an inner grooved surface (72) of a ring (70) for obtaining an axial seal. The series of disks comprises three disks, a first disk (12), a second disk (13) and a third disk (14) respectively. The three disks are fixed to each other centrally by means of a series of spokes (30) and are constrained in pairs respectively by means of a series of pins which are arranged orthogonally to the three disks to minimize the relative movements of the three disks in an axial direction at the same time allowing the radial dilatations of the three disks themselves.

Abstract: A self-monitoring adjustment system is provided for evaluating and effecting adjustment of the leakage restricting mechanism between the rotating and non-rotating elements of a rotodynamic pump to restrict leakage and to establish desired gap dimensions between the rotating and non-rotating elements of the pump. The adjustment system is structured to be self-monitoring for determination of when an adjustment of the leakage restricting mechanism is warranted by the conditions of the pump, and is structured with adjusting mechanisms that are self-adjusting responsive to the monitored conditions of the pump, though manual adjustment is also enabled.

Abstract: A blade gap control system configured to move a blade ring of a turbine engine relative to a blade assembly to reduce the gaps between the tips of the blades and the blade rings to increase the efficiency of the turbine engine is provided. The blade rings can be at an acute angle with respect to the rotational axis of the blade assembly. The axial movement of the blade ring can be done by a pressure differential supplied across the blade ring, the thermal expansion and/or contraction of a linkage or by a piston.

Abstract: An apparatus and method for controlling a blade tip clearance for a compressor of a turbo-engine, in particular of an aircraft engine, is disclosed. A blade tip clearance control device, which has a rotor and a housing surrounding the rotor forming a blade tip clearance, includes a sealing element that is movable into the blade tip clearance and an actuator unit, where the sealing element is designed as a circumferential shroud liner made of a flexible rubbery material in which at least one tubular diaphragm that is also circumferential is arranged. The diaphragm is acted upon with hydraulic fluid via the actuator unit. This makes it possible to counteract degradation that occurs during operation due to erosion, aging, etc. As a result, efficiency is maintained and the pump limit interval is retained.

Abstract: A device for varying the section of the throat of a turbine nozzle, the nozzle being formed by a plurality of stationary vanes extending radially between outer and inner annular platforms and spaced apart from one another in order to define a throat presenting a minimum flow section. The device comprises an annular element having a coefficient of expansion that is less than that of the platforms of the nozzle, the annular element being secured to the outer platform and being capable of taking up two positions: one position corresponding to no expansion of the platforms, in which the element provides continuity for the profile of the flow passage; and another position corresponding to the platforms having expanded, in which position the element projects into the flow passage so as to reduce its section.

Abstract: A turbofan gas turbine engine (10) comprises a compressor rotor (24) carrying a plurality of circumferentially spaced radially extending rotor blades (26) and a casing (28) surrounding the compressor rotor (24) and compressor rotor blades (26). A compressor rotor blade tip seal (48) comprises an annular member (30) secured to and arranged within the casing (28). The annular member (40) has a plurality of circumferentially spaced axially extending corrugations (32) and a plurality of radially spaced circumferentially extending corrugations (34). A lining (40) is secured to and arranged within the annular member (30). The lining (40) is spaced radially from the tips (27) of the compressor rotor blades (26) to form a clearance (29). An actuator (56) is provided to move the annular member (30) and lining (40) radially to control the size of the clearance (29).

Abstract: A rotor system is provided whereby a rotary assembly such as a fan blade combination in a jet engine is brought into rub contact with a casing such that sensors detect vibration. The casing is then retreated in order to open the gap to a desired value for engine performance. In such circumstances, the rub contact position is defined as a base datum reference from which distance the casing is displaced in order to provide the specified gap for engine performance and efficiency.

Abstract: A turbine shroud segment attachment with a casing (1) and several shroud segments (2) arranged in the casing (1), wherein the individual shroud segments (2) are located in the casing (1) with a circumferential clearance (3) between the individual shroud segments (2), in that the clearance (3) is reduced to zero at a given temperature difference between the casing (1) and the shroud segments (2), and in that the shroud segments (2) are retained on the casing (1) by way of an elastically deformable locating arrangement.

Abstract: A centrifugal pump assembly that includes an inlet housing that defines a inlet chamber and at least one inlet port in fluid communication with the inlet chamber. A volute forming part of the assembly defines an outlet port. An impeller is mounted for rotation at least partially within the volute and operative upon rotation to convey fluid from the inlet port to the outlet port. The inlet housing defines mounting structure by which the inlet housing can be secured to the volute in any one of a plurality of positions with respect to the volute so that the spatial relationship between the inlet port and the outlet port can be changed by changing the relative position of the inlet housing with respect to the volute. The inlet housing also mounts a pump insert which may be either a dedicated clean-out assembly or structure defining an axial inlet port.

Abstract: An air pump has a casing, a motor assembly, a fan assembly, a faceplate and a sliding valve assembly. The motor assembly is mounted in the casing and has a motor. The fan assembly has a fan housing, an inlet manifold, an inlet plate and a centrifugal impeller. The centrifugal impeller is mounted rotatably in the fan housing and connects to the motor. The sliding valve assembly is hollow, is mounted slidably between the faceplate and the motor assembly and has a rear, a partition and an air passage. The partition extends into the sliding valve assembly. The air passage is formed between the partition and the rear. The air pump inflates when the air passage aligns with in the inlet manifold. The air pump deflates when the air passage aligns with the fan housing.

Abstract: In one aspect, there is provided a wear plate for use in combination with a centrifugal pump and impeller. The wear plate has a wear surface defined by a substantially flat surface, a truncated conic section, and/or a curvilinear solid of revolution formed by revolving an area bounded by a curve around a center axis of the wear plate, wherein a notch or recess is provided. The notch or recess extends in a first direction perpendicular to a predetermined direction of rotation of an impeller and a second direction crossing against a direction of rotation of the impeller.

Abstract: A pump casing for a centrifugal pump of the type that is used to process abrasive slurries is disclosed having at least one side or side liner that has a radially extending portion oriented toward the cutwater of the pump casing to localize the abrasive wear caused by the abrasive slurries to the side of the pump casing. The side liner of the pump is configured with a perimeter edge that is non-circular. The pump casing may preferably be configured with an open cutwater configuration or other suitable configuration for localizing wear to the sides of the casing.

Abstract: A centrifugal pump having an adjustable clean-out assembly (60), the position of which determines the face clearance between a wear plate (72) and an impeller (20). The clean-out assembly includes an end cover (63) that threadedly mounts a plurality of adjustment assemblies. The adjustment assembly includes an adjuster (104) that defines a through bore for slidably receiving a retaining stud (66) that extends from the pump housing. Each adjuster includes an abutment surface (108) which engages a pump surface and which establishes the face clearance between the wear plate and the impeller. Each adjuster includes a hex-shaped head which is engageable by an associated locking member (120) secured to the end cover. Each locking member includes a locking collar (120a) having 18 teeth which allows the collar to engage the hex-shaped head of the adjuster in 18 different postions.