Abstract: A system and method are disclosed for reducing the fuel consumption of an engine, particularly during a cold start or an engine warm-up period. A magnetorheological fluid having a low viscosity is used to lubricate the engine. When viscosity is to be increased, a magnetic field is applied to the magnetorheological fluid. The magnetic field can be selectively applied to electromagnets proximate engine bearings.

Abstract: Damping systems and engines including the damping systems are provided. In one embodiment, and by way of example only, the damping system includes a rotor, a bearing assembly mounted to the rotor, a spring cage disposed around the bearing assembly, an axially-extending housing surrounding the spring cage, a first squeeze film damper formed between the bearing assembly and the spring cage, and a second squeeze film damper formed between the spring cage and the axially-extending housing.

Abstract: A bearing assembly for a submersible pump motor has a bearing body, having a hub, an outer portion, and a plurality of wing portions. The wing portions are spaced apart to form a plurality of cavities in the bearing body. A mass damper is mounted to the hub. The mass damper has an upper portion, a lower portion and mass damper prongs connecting the upper and lower portion. The mass damper prongs are disposed in the cavities, and act to reduce the amplitude of the vibrating frequency of the motor shaft.

Abstract: An exemplary bearing for a turbocharger includes one or more thrust pads where each thrust pad includes a portion of a conical well; and a through-bore that includes lubricant channels, each channel configured to direct lubricant from the bore to a corresponding conical well of a thrust pad. Other exemplary technologies are also disclosed.

Abstract: An auxiliary bearing system for a magnetically supported rotor system according to which the auxiliary bearing system includes at least two mounting pad assemblies having compliantly mounted body members.

Abstract: An annular vibration isolator for a rotating shaft supported by a bearing is provided. The annular vibration isolator comprises an outer ring extending substantially entirely around the bearing, an arc portion having a contact portion extending toward the bearing, first and second axial portions enclosing a cavity, a first flange portion forming a first channel, a second flange portion forming a second channel, and the first and second flange portions forming a chamber within the cavity and forming a radial passageway connecting the chamber to the first and second channels, and a bellows disposed in the chamber and coupled to the radial passageway, the bellows adapted to receive a fluid from the first and second channels.

Abstract: A mounting assembly is provided. The mounting assembly comprises an outer ring having a plurality of insert portions, each of the plurality of insert portions extending toward the center of the outer ring and having an insert cavity, a plurality of vibration isolation assemblies, each of the vibration isolation assemblies disposed in one of the insert cavities, each of the plurality of vibration isolation assemblies comprising a first bellows portion and a second bellows portion, a passageway formed therein and connecting the first and second bellows portions, and a contact portion adapted to receive a force, an inner ring having a plurality of contact cavities, each contact cavity adapted to receive a contact portion from one of the plurality of vibration isolation assemblies, and a central ring coupled to the outer ring by the plurality of insert portions, and to the inner ring by a plurality of bridge portions.

Abstract: A lube spacer bearing for a lube and scavenge pump includes a bearing body defining a bore with a central axis. The bearing body has a first axial side, a second axial side, an outer radial side, and an inner radial side at the bore. The outer radial side includes an arcuate portion. A channel is defined in the arcuate portion of the outer radial side and extends a circumferential length about the outer radial side. The channel has a channel width (CW) defined between a first channel wall and a second channel wall and a bearing length (BL) defined between the first axial side and the second axial side. A ratio of CW/BL is between 0.45 and 0.70.

Abstract: A device for centering a tube inside a hollow shaft is disclosed. The device includes a deformable device interposed between the tube and the hollow shaft and including bearing members for bearing against the inside surface of the shaft and suitable for being spaced away from the inside surface of the shaft in order to enable them to be moved inside the shaft. The deformable device is made of a shape-memory material suitable for deforming to press the bearing members against the inside surface of the shaft or to space them away therefrom on being subjected to a predetermined temperature.

Abstract: A support device for a bearing assembly includes a housing with a bore and a centerline and a bearing having a bore for receiving a rotatable shaft. The support device has an annular body disposable within the housing bore and having a central axis and inner and outer surfaces extending circumferentially about the axis, the inner surface defining a central bore for receiving the bearing. One or more first integral spring portions extend generally between the inner and outer surfaces and have a first stiffness and one or more second integral spring portions are each spaced circumferentially from the first spring(s). The second spring extends generally between the inner and outer surfaces and has a second, greater stiffness. The body is adjustably angularly positionable about the body axis to adjust a position of the shaft axis with respect to the housing centerline when disposed within the support bore.

Abstract: A gas turbine engine bearing assembly for a portion of a shaft that rotates around an axis, including a substantially cylindrical bearing having a length extending between a first end and a second end along the axis of the rotating shaft. A plurality of segmented damper springs are positioned around an exterior perimeter of a portion of the cylindrical bearing. Each spring has a width along the axis of the rotating shaft and a portion of each spring defines an outer spherically contoured joint. The width of each spring is less than the length of the bearing.

Abstract: A bearing damper includes: (a) an annular sleeve having spaced-apart grooves formed in a radially-facing surface therein; (b) an annular bearing race received in the sleeve; and (c) a resilient seal ring disposed in each of the grooves, wherein the seal rings cooperate with the sleeve and a radially-facing surface of the bearing race to define a closed annular gap, and further wherein the seal rings are sized so as to urge the bearing race towards a coaxial position relative to the sleeve.

Abstract: A squeeze-film damper arrangement comprising: concentric inner and outer components defining an annular gap there between for accommodating radial motion of the inner component within the outer component; and a fluid filling the annular gap around the outside of the inner component for damping said radial motion of the inner component, the fluid being axially contained between spaced-apart, radially-compliant first and second face-seals provided between the inner and outer components; wherein the first face-seal is provided between the opposing faces of a first pair of radially overlapping circumferential sealing elements associated with the inner and outer components respectively, a first one of the circumferential sealing elements in said pair being mounted for axial movement relative to the associated inner or outer component and being axially biased against the second of said circumferential sealing elements in said pair to form the first face-seal.

Abstract: To provide a bearing support structure and a gas turbine that prevent damage of device induced by a rotor shaft when the rotor shaft is unbalanced, the bearing support structure and the gas turbine includes: a casing (7) formed in a cylindrical shape; a bearing unit (8) formed in a cylindrical shape and housed in the casing (7); a rotation shaft (5) rotatably supported by the bearing unit (8); and a reaction-force decreasing unit (13) that connects the casing and the bearing unit, and is configured to decrease a radial reaction force on the bearing unit side.

Abstract: An exemplary anisotropic member (625, 1200, 1600, 1700, 1800, 1950) supports a bearing in a bore and can reduce non-synchronous vibration (NSV) of the bearing in the bore. An exemplary anisotropic member includes an annular body configured to receive a bearing and to space the bearing a distance from a bore surface and is configured to impart anisotropic stiffness and damping terms to the bearing when positioned in the bore. Such a member is suitable for use in a rotating assembly for a turbocharger where the bearing may be a floating bearing, a semi-floating bearing or a ball bearing. Various exemplary members, bearings, housings, assemblies, etc., are disclosed.

Abstract: A compliant hybrid gas journal bearing includes compliant hybrid bearing pads having a hydrostatic recess and a capillary restrictor for providing a flow of pressurized gas to the bearing. The bearing also includes an inner rim adjacent the bearing pads, an outer rim and a damper bridge between the inner and outer rims. The damper bridge has an axial length that is less than an axial length of the bearing pads and the outer rim to form a damper cavity on each side of the damper bridge. An integral wire mesh damper is situated within the damper cavity on each side of the damper bridge. Integral centering springs are located between the inner and outer rims to provide radial and rotational compliance to the bearing pads. The oil-free bearing design addresses the low damping and low load capacity characteristics that are inherent in present day compliant air foil bearing designs, while retaining the compliance to changes in rotor geometry.

Abstract: A hydrostatic gas bearing capable of easily adjusting a clearance between a rotor and a radial bearing pad is provided. This hydrostatic gas bearing comprises a radial bearing pad radially supporting a rotor, a linear motion guide moving the radial bearing pad and a ball stud swingably coupling the radial bearing pad to the linear motion guide. The linear motion guide moves the radial bearing pad in a direction intersecting with a direction connecting the center of rotation of the rotor and the ball stud with each other. The quantity of adjustment in movement of the radial bearing pad caused by the linear motion guide is larger than the quantity of change in the clearance between the outer peripheral surface of the rotor and the radial bearing pad, whereby a small quantity of the bearing clearance can be precisely adjusted.

Abstract: An improvement for a turbine generator or pump having main bearings separated by a span of shaft and a thrust equalizing mechanism adjacent one of said main bearings, the improvement comprising a stationary length compensator interposed between the thrust equalizing mechanism and its adjacent main bearing to reduce the span between said main bearings. Preferably the length compensator is composed of material that shrinks less than the shaft of the generator, and the height of the length compensator, i.e., the compensating dimension, is selected according to desired thrust equalizing mechanism operating parameters over a temperature range.

Abstract: A laying head for forming coils using continuous and substantially rectilinear rolled products such as rods or wire, having vibration damping means integrated in one of two rotor supports (3), preferably the one on the rolled product outlet side. Said means comprise a plurality of coils (6, 6?, 6?) arranged around the rotor (3), rotating about its axis (X), which generate a magnetic field actively controlled by a computer, the resultant force of which is perpendicular to the axis (X) and of a predetermined intensity so as to eliminate the inertial forces generated by the mass imbalances. Alternatively, the damping means incorporated in one of the supports are comprised of oil film bearings.

Abstract: There is disclosed a bearing to support a rotating shaft. The bearing includes a cylindrical housing defining a central opening. A plurality of bearing pads integrally coupled to the housing with each bearing pad having a circumferential surface defining a portion of the central opening. A plurality of pins disposed in a bore defined in the housing, with each pin aligned as a pivot for each corresponding pad. Each pad can tilt about the pin in relation to the rotating shaft. Each pad is coupled to the housing by a pair of webs defined by a plurality of cuts forming a plurality of openings in the housing substantially parallel to a line tangent with the circumferential surface of the pad. Each pin is aligned parallel with the rotating pad.

Abstract: Chambers for a bushing bearing with damping means include outer sleeve and inner bearing part, accommodated in the outer sleeve with rigid bearing core and elastomeric bearing body surrounding the core. The expanding walls of the chambers are disposed transversely to the bearing axis (A). The inner bearing part is segmented with respect to the longitudinal axis (A) of the bearing and includes a center main segment with bearing core and bearing body and two end segments, each having an inner ring, an outer ring, and an interposed elastomeric element forming expanding wall of a chamber. The end segments are pressed with inner ring onto axial ends of the bearing core so that the material overlaps between the elastomeric elements of the end segments and the ribs of the bearing body. The channel is formed outside of the bearing body in a channel carrier element.

Abstract: A damping system for a gas turbine engine comprises a bearing mounted to a rotor shaft and a support connected to an outer race of the bearing. The support has a wall secured to a casing of the gas turbine engine at a connection portion. The wall has a first surface positioned against a surface of the casing with the first surface being in a non-parallel relation with the rotational axis of the rotor shaft. A cavity is defined in the first surface by a narrowing of a thickness of the wall. The cavity contains a damping fluid to dampen elastic deformation of the wall at the cavity resulting from axial oscillations of the rotor shaft. An abutment is provided to limit an amplitude of the elastic deformation of the wall.

Abstract: An exemplary method for limiting movement of an outer race of a bearing cartridge includes positioning the bearing cartridge in a substantially cylindrical bore having a longitudinal axis, an inner diameter exceeding an outer diameter of the outer race, a proximate end and a distal end; limiting axial movement of the outer race at the distal end of the cylindrical bore with a counterbore substantially coaxial to the cylindrical bore and having an inner diameter less than the outer diameter of the outer race; limiting axial movement of the outer race at the proximate end of the cylindrical bore with a plate positioned substantially orthogonal to the longitudinal axis; and limiting rotation of the outer race with a pin positioned in a pin opening accessible via a lubricant drain. Various exemplary bearing cartridges, housings, assemblies, etc., are also disclosed.

Abstract: A roller bearing assembly is configured to rotatably support a machine component connected with a shaft in a position relative to a reference component. The roller bearing assembly includes a radial bearing, an axially-displaceable axial bearing and an adjusting device configured to adjust an axial gap between the machine component and the reference component by automated axial displacement of the axial bearing. The adjusting device includes a hydraulic regulating device configured to axially displace the axial bearing.

Abstract: A rotor bearing system for a rotating machine includes a housing having a bore that provides an inner surface. A bearing assembly is disposed within the bore and includes an outer surface. An annular cavity is provided radially between the outer surface and the inner surface. At least one protrusion extends radially outwardly from at least one of the inner and outer surfaces to an apex and into the annular cavity. A radial gap is arranged between the apex and the opposite surface from which the protrusion extends. In the disclosed example, the annular cavity is filled with an oil to provide a squeeze film damper between the housing and the bearing assembly. The protrusions exert a hydrodynamic preload on the bearing assembly, which reduces vibration during operation of the rotating machine.

Abstract: A bearing system for reducing end clearance and axial vibrations includes a bearing housing and a bearing. The bearing is a thrust bearing and may be of any type, such as a flat thrust face, a taper land thrust bearing or a tilt pad thrust bearing. The bearing housing includes a cavity to hold the bearing. A fluid cavity is formed between the bearing and the bearing housing. At least one fluid passageway extends through the bearing housing to feed fluid to the fluid cavity. As fluid is introduced to the fluid cavity the pressure in the cavity moves the bearing outward, away from the bearing housing and towards the rotating thrust collar, reducing the clearance, or space, between the face of the bearing and the thrust collar, reducing or eliminating the vibrations.

Abstract: A fluid distribution system for use in a gas turbine engine includes a fan shaft, a damper, a bearing, and a pump. The damper supports the bearing, and the bearing supports the fan shaft. The pump is connected to and driven by the fan shaft. The pump is also fluidically connected to the damper.

Abstract: A squeeze film damper assembly having a variable stiffness and damping control. The squeeze film damper includes a damper chamber formed by two flexible bellows chambers of the sides. A first pressure source is applied to the damper chamber to regulate the damping. A second pressure source is applied to the flexible bellows chambers to vary the stiffness of the damper. The flexible bellows chambers are secured between an outer member and an inner member of the damper assembly and form the sealed damper chamber. A pressure ratio between the bellows chambers and the damper chamber can vary to control the stiffness of the squeeze film damper.

Abstract: A bearing assembly comprises an inner ring and an outer ring assembly having an upstream face and a downstream face. The outer ring assembly comprises an outer ring rotatably coupled to the inner ring, and a plurality of rolling elements that resides between the inner ring and the outer ring. At least one flow bypass channel extends through the outer ring assembly.

Abstract: A support damper is provided for a bearing assembly to improve the damping capabilities of an uncentered squeeze film damper and to provide a support structure stiffness to minimize rotor to structure unbalance response. In one embodiment, and by way of example only, the support damper includes an inner ring, an outer ring, and U-shaped beams. The inner ring is configured to be disposed around the bearing assembly and to extend axially along a portion thereof. The outer ring is spaced apart from the inner ring and extends radially outwardly relative thereto. The U-shaped beams couple the inner ring to the outer ring. Methods of manufacturing the support damper are also provided.

Abstract: Hydrodynamic bearing with four lobes with centres of curvature that are eccentric relative to its geometrical centre, said lobes being separated by oil feed grooves wherein the lobes are dissymmetrical and present;—angular apertures of at least two different values;—at least two different eccentricities relative to the geometrical centre of the bearing; the centres of two opposing lobes being aligned with the geometrical centre of the bearing.

Abstract: A rotary pump having thrust bearings includes a system for equalizing the loading on the thrust bearings. The thrust bearings are each supported on pistons that are in fluid communication with a hydraulic circuit. The hydraulic circuit has substantially the same pressure throughout, thereby floating each piston at the same pressure to provide an equal support force to each thrust bearing via each piston.

Abstract: An exemplary bearing for a turbocharger includes one or more thrust pads where each thrust pad includes a portion of a conical well; and a through-bore that includes lubricant channels, each channel configured to direct lubricant from the bore to a corresponding conical well of a thrust pad. Other exemplary technologies are also disclosed.

Abstract: A squeeze film damper is provided that includes a fluid source, a shaft, a bearing assembly, a static bearing support, and a dam. The shaft includes openings formed therein and an annular channel in communication therewith that is configured to receive fluid from the fluid source. The bearing assembly is disposed concentric to the shaft and includes an inner race coupled to the shaft, an outer race disposed concentric to the inner race, and a rolling element disposed between the inner and outer races. Each of the inner and outer races includes openings configured to receive fluid from the shaft opening. The static bearing support housing is spaced apart from the outer race to define a clearance therebetween. The dam is disposed adjacent the bearing assembly and extends radially inwardly relative to the bearing support housing defining a shelf for receiving the fluid from the race openings and directing the fluid into the clearance.

Abstract: A rotor mount assembly for an electrical machine, such as a high speed aerospace generator, comprises a spring having a simple annular structure together with an oil squeeze film damper (SFD). The spring is engineered to move the rotor critical speeds outside of the extremes of the operating speed range and the SFD damps out the rotor responses as the speed passes through these points.

Abstract: A device for supporting and guiding a rotating shaft, in particular a rotor shaft of an airplane turboprop or turbojet, the device comprising an oil squeeze damper around each bearing of the shaft, said damper comprising an annular space surrounding the outer ring of the bearing and defined by annular sealing elements, each having a small number of calibrated oil outlet orifices formed in its outer periphery.

Abstract: A compliant hybrid gas journal bearing includes compliant hybrid bearing pads having a hydrostatic recess and a capillary restrictor for providing a flow of pressurized gas to the bearing. The bearing also includes an inner rim adjacent the bearing pads, an outer rim and a damper bridge between the inner and outer rims. The damper bridge has an axial length that is less than an axial length of the bearing pads and the outer rim to form a damper cavity on each side of the damper bridge. An integral wire mesh damper is situated within the damper cavity on each side of the damper bridge. Integral centering springs are located between the inner and outer rims to provide radial and rotational compliance to the bearing pads. The oil-free bearing design addresses the low damping and low load capacity characteristics that are inherent in present day compliant air foil bearing designs, while retaining the compliance to changes in rotor geometry.

Abstract: A squeeze film damper for a bearing and a vibration damping mechanism capable of damping the vibration of a rolling bearing are provided. The squeeze film damper is small in construction and can be easily made by mass production. The vibration damping mechanism is capable of damping both radial and axial vibrations. A bearing housing 15 is provided with a bearing holding bore 16 of a diameter greater than the outside diameter of the outer ring 14 of a bearing, and an oil hole 19 through which oil is supplied into the bearing holding bore 16. A vibration damping mechanism 1 is formed by inserting a thin, flat sheet 17 provided with slits into an annular space formed between the inner wall of the bearing holding bore 16 and the outside surface of a bearing held in the bearing holding bore 16 so as to surround the bearing. Parts of the thin, flat sheet extending between the adjacent slits serve as elastic beams. The elastic beams center the bearing and support the centered bearing elastically.

Abstract: The bearing assembly includes an annular bearing in which the shaft is disposed and a support structure for supporting the bearing. The bearing support is mounted about and radially supports the bearing. The bearing support at least in part defines a squeeze film annulus of the bearing assembly. A plurality of centering elements is associated with the bearing and bearing support and act to center the bearing within the squeeze film annulus. The centering elements are provided at radially spaced locations around the bearing. The centering elements may also be cylinder springs provided at uniformly spaced locations around the bearing. The centering elements may additionally be load cell springs provided at uniformly spaced locations around the bearing. In an alternative embodiment, a singular annular wave spring may be provided in place of the plurality of centering elements.

Abstract: The present invention provides a rotating-body support structure that is capable of obtaining a damping effect of a rotating body with a simple configuration. To this end, the rotating-body support structure is configured to include a housing (21) and a bush portion (24) which is supported by the housing (21) and which rotatably supports a boring bar (11); and to have oil filled between the housing (21) and the bush portion (24).

Abstract: A squeeze-film damper arrangement comprising: concentric inner and outer components defining an annular gap there between for accommodating radial motion of the inner component within the outer component; and a fluid filling the annular gap around the outside of the inner component for damping said radial motion of the inner component, the fluid being axially contained between spaced-apart, radially-compliant first and second face-seals provided between the inner and outer components; wherein the first face-seal is provided between the opposing faces of a first pair of radially overlapping circumferential sealing elements associated with the inner and outer components respectively, a first one of the circumferential sealing elements in said pair being mounted for axial movement relative to the associated inner or outer component and being axially biased against the second of said circumferential sealing elements in said pair to form the first face-seal.

Abstract: A damper element of the present invention is applied to a bearing damper element disposed between a rotating object and a supporting object. The damper element includes a slit that is formed between an inner surface and an outer surface of an annulus being supported by the supporting object, and a viscous fluid that is filled in the slit. The slit is extended substantially along a circumferential direction of the annulus. The annulus is, for example, an outer ring or an inner ring of a rolling element bearing, a plane bearing, or a collar that holds a bearing.

Abstract: A method for assembling a gas turbine engine is provided. The method includes coupling a high-pressure compressor to a high-pressure turbine using a first shaft, coupling a fan assembly to a low-pressure turbine using a second shaft, and coupling a differential squeeze film damper assembly between the first and second shafts.

Abstract: A bearing assembly for use between two components in a transmission includes an inner member located within an outer member. The inner member includes a plurality of bearing element windows and a bearing element is located within each bearing element window. The inner member is biased against the outer member by a spacer member. Fluid is able to flow through and/or around the spacer member between the two components of the transmission.

Abstract: A laying head for forming coils using continuous and substantially rectilinear rolled products such as rods or wire, having vibration damping means integrated in one of two rotor supports (3), preferably the one on the rolled product outlet side. Said means comprise a plurality of coils (6, 6?, 6?) arranged around the rotor (3), rotating about its axis (X), which generate a magnetic field actively controlled by a computer, the resultant force of which is perpendicular to the axis (X) and of a predetermined intensity so as to eliminate the inertial forces generated by the mass imbalances. Alternatively, the damping means incorporated in one of the supports are comprised of oil film bearings.

Abstract: The present invention relates to a bearing support for a rotating engine such as a gas turbine engine, with a rotating shaft supported by at least one bearing and a frame, capable of running at least two different running speeds, characterised in that it comprises at least two mechanical supporting structures with different stiffnesses combined so as to support the bearing at one of these stiffnesses. The invention has the advantage that the use of mechanical structures avoids the presence of any hydraulic equipment, since the stiffness forces thus introduced can directly oppose excitation forces generated by the unbalanced mass of the engine shaft.

Abstract: A centering ring may be used to provide a resilient mounting system with uniform stiffness for rotating machinery. The centering ring may have first and second exterior raised ridges on one surface and a central raised ridge on the other surface. The centering ring may be disposed between the housing of the rotating machinery and a bearing provided therein. Due to its uniform cross-sectional geometry about its entire circumference, the centering ring may provide uniform stiffness in any radial direction. The centering ring may be useful in any rotating machinery, including generators, turbo machines and turbine engines.

Abstract: A squeeze film damper assembly having a variable stiffness and damping control. The squeeze film damper includes a damper chamber formed by two flexible bellows chambers of the sides. A first pressure source is applied to the damper chamber to regulate the damping. A second pressure source is applied to the flexible bellows chambers to vary the stiffness of the damper. The flexible bellows chambers are secured between an outer member and an inner member of the damper assembly and form the sealed damper chamber. A pressure ratio between the bellows chambers and the damper chamber can vary to control the stiffness of the squeeze film damper.

Abstract: An exemplary method for limiting movement of an outer race of a bearing cartridge includes positioning the bearing cartridge in a substantially cylindrical bore having a longitudinal axis, an inner diameter exceeding an outer diameter of the outer race, a proximate end and a distal end; limiting axial movement of the outer race at the distal end of the cylindrical bore with a counterbore substantially coaxial to the cylindrical bore and having an inner diameter less than the outer diameter of the outer race; limiting axial movement of the outer race at the proximate end of the cylindrical bore with a plate positioned substantially orthogonal to the longitudinal axis; and limiting rotation of the outer race with a pin positioned in a pin opening accessible via a lubricant drain. Various exemplary bearing cartridges, housings, assemblies, etc., are also disclosed.

Abstract: A hydrostatic gas bearing capable of easily adjusting a clearance between a rotor and a radial bearing pad is provided. This hydrostatic gas bearing comprises a radial bearing pad radially supporting a rotor, a linear motion guide moving the radial bearing pad and a ball stud swingably coupling the radial bearing pad to the linear motion guide. The linear motion guide moves the radial bearing pad in a direction intersecting with a direction connecting the center of rotation of the rotor and the ball stud with each other. The quantity of adjustment in movement of the radial bearing pad caused by the linear motion guide is larger than the quantity of change in the clearance between the outer peripheral surface of the rotor and the radial bearing pad, whereby a small quantity of the bearing clearance can be precisely adjusted.