35results about How to "Small measuring force" patented technology

The invention relates to a sensing method and a device for micro inner cavity size and three-dimensional coordinate based on two-dimensional micro-focus collimation, belonging to the technical filed of precise instrument manufacture and measurement, in particular to a sensing method and a device for micro and complex inner cavity size and three-dimensional coordinate in the filed of sub-macroscopy, which is especially suitable for the three-dimensional detection of blind holes with large depth-diameter ratio. The device combines a micro spherical biconvex lens and an optical fiber probe measuring rod, and establishes a point light two-dimensional micro-focus collimation imaging light path by using the micro spherical biconvex lens, thereby realizing the high magnification and the sensing for the three-dimensional displacement of the optical fiber probe measuring rod by utilizing the light path. The invention has the characteristics of small measured force of a single optical fiber probe, easy miniaturization, large measured depth-diameter ratio, simple system structure, good real-time performance, easy practical application, and has obvious advantages for carrying out the quick and ultra-precise measurement and calibration for the inner cavity micro-size and the three-dimensional coordinate. Especially, the top of the resolution capability can reach the deep sub-nanometer magnitude, and an absolute zero position exists in the three-dimensional measurement direction.

The invention relates to a sensing method and a device for micro inner cavity and two-dimensional coordinate based on one-dimensional micro-focus collimation, belonging to the technical filed of precise instrument manufacture and measurement, in particular to a sensing method and a device for micro and complex inner cavity structure size and two-dimensional coordinate in the filed of sub-macroscopy, which is especially suitable for the measurement of micro-holes with large depth-diameter ratio. By using the structure characteristics of super large curvature and micro-cylindrical lens of an optical fiber probe measuring rod, a point light source one-dimensional micro-focus collimation imaging light path is established, thereby realizing the high magnification and the sensing of the two-dimensional displacement of the optical fiber probe measuring rod by utilizing the light path. The invention has the characteristics of small measured force of a single optical fiber probe, easy miniaturization, large measured depth-diameter ratio, simple system structure, good real-time performance, easy practical application, and has obvious advantages for carrying out the quick and ultra-precise measurement and calibration for the inner cavity micro-size and the two-dimensional coordinate. Especially, the top of the resolution capability can reach the deep sub-nanometer magnitude, and an absolute zero position exists in the two-dimensional measurement direction.

The invention discloses a bearing ring optical density air gauge which comprises an electric translator (11), an electric display (12) and a air measurer(2) which adopts a column structure and is arranged on a measuring device; it inlets the condensed air through the grouter(8) of the air measurer(2) into the inner bearing ring (1)optical density, the air measurer(2) can use the electric translator (11) to change and use the electric display (12) to display the measuring value by the change of the length value of the draft force.

The invention discloses a device and method for measuring diameters of internal and external raceways of a wind power bearing. The device comprises a ruler and a meter, wherein the left side and the right side of the ruler are respectively provided with a measuring bar, i.e. a left measuring bar and a right measuring bar respectively; the left measuring bar and the right measuring bar can be moved and fixed on the ruler; the left measuring bar and the right measuring bar can also be arranged on the ruler in the reverse direction for measuring; the left measuring bar and the right measuring are vertical to the ruler; the left measuring bar is provided with a fixed measuring head through a left fixed mount; the right measuring bar is provided with a moving measuring head through a right fixed mount; the meter is fastened and connected with the right measuring bar through a fixed bar; and a contact of the meter and the right end surface of the moving measuring head are in elastic contact. The method comprises the steps of adjusting the measuring device, actually measuring and judging whether the diameters of the raceways are qualified or not. The device can be used for measuring the diameters of the internal and the external raceways of the bearing, thereby improving the efficiency and the convenience of the measuring work.

The invention discloses a pneumatic device for measuring internal diameter and external diameter of a thin-wall bearing ring. A thin-wall bearing ring easily deforms and generates test marks on the surface due to measurement by a traditional mechanical measurement instrument. The device provided by the invention comprises a conveying belt, a stepper motor, a central fixture, an external diameter measuring head, an internal diameter measuring head, a measuring driving device and a central cylinder. The stepping motor drives the conveying belt; the external diameter measuring head and the internal diameter measuring head both include an upper measuring head and a lower measuring head; an upper airway of the upper measuring head is communicated with plurality of lower airways of the lower measuring head; a side wall of each back pressure sensor connection hole is connected with the is communicated with one lower airway; each back pressure sensor connection hole is provided with the hole a pressure sensor; each back pressure sensor connection hole of the external diameter measuring head is provided with a measuring nozzle; and the outer end of each back pressure sensor connection hole of the internal diameter measuring head is provided with a measuring nozzle. The invention adopts pneumatic measurement mode for measuring the internal diameter and external diameter of thin-wall bearing ring, and the surface of the measured part will not be scratched and can keep the geometrical shape.

The invention discloses a three-dimensional resonance trigger probe based on a quartz tuning fork and a three-dimensional resonance trigger location method. The three-dimensional resonance trigger probe is characterized in that the quartz tuning fork is used as a micro force sensor, a piezoelectric driver is fixed on a fork arm of the quartz tuning fork, a piezoelectric sensor is fixed on the other fork arm; the quartz tuning fork is vertical to the surface of a sample in the vibration direction on the Z direction and is parallel to the surface of the sample in the vibration direction on X and Y directions, an integrated micro measuring bar measurement ball is fixedly arranged on the fork arm close to one side where the sample is in, and a sine alternating-current signal output by a phase-locked loop is applied to the piezoelectric sensor as an excitation signal, and a fork resonance signal is detected by the piezoelectric sensor. When a micro three-dimensional external force causes that the resonance frequency of the probe changes, the resonance frequency of a quarts tuning fork probe changes, and three-dimensional resonance trigger location of the three-dimensional resonance trigger probe is realized through detecting the change of the resonance frequency of the quartz tuning fork.

The invention relates to a variable-stiffness contact micro-nano coordinate measuring machine probe which is characterized in that the variable-stiffness contact micro-nano coordinate measuring machine probe comprises elastic sensitive beams, a central connector, a crane-shaped frame, an H-shaped flexible mechanism, a capacitor upper pole plate, a capacitor lower pole plate and a worktable; the inner end of the elastic sensitive beam is fixed to the head part of the crane-shaped frame; the outer end of the elastic sensitive beam is fixed to the inner end of the midpoint of the H-shaped flexible mechanism; the end of the central connector is fixed to the midpoint of the elastic sensitive beam; two sides of the H-shaped flexible mechanism are fixed to the crane-shaped frame; the capacitor upper pole plate is fixed to the lower surface of the end of the central connector; and the capacitor lower pole plate is fixed to the upper end of the worktable. According to the variable-stiffness contact micro-nano coordinate measuring machine probe, through arranging a probe suspension mechanism, probe system stiffness adjustment and compact spatial arrangement structure are realized; through arranging a piezoelectric driver and the elastic sensitive beam, a measuring force in a measuring process is reduced; through arranging the elastic sensitive beams which are uniformly distributed aroundthe axis of the workpiece and the crane-shaped frame, a requirement for mounting symmetry and consistent pressure of the elastic sensitive beam is reduced; and furthermore the variable-stiffness contact micro-nano coordinate measuring machine probe has advantages of simple structure, convenient operation, high economic performance and high practicability.

The invention discloses a thin wall bearing ring optical density air gauge, which comprises an electric translator (10), an electric display (11) and air measurer(4) which adopts a ring structure and is arranged on a measuring device; it inlets the condensed air through the grouter of the air measurer into the inner bearing ring(1)optical density, the air measurer(4) can use the electric translator (10) to change and use the electric display (11) to display the measuring value by the change of the length value of the draft force.

An exemplary contour measuring probe (10) includes a tip extension (16) and two driving members (13). The tip extension is configured for touching a surface of an object. The driving members are configured for driving the tip extension linearly moving along a first direction. The driving members are tapered and a diameter of each driving member increases along the first direction. The driving members are driven to move by gas pressure acting on an outer side surface thereof.

The invention discloses an ultra-precision micro-displacement sensing system based on a double-FBG suspended type probe structure. The system is characterized in that a stainless steel needle tube is adopted in a probe to serve as a protective sleeve, two FBG optical fiber measuring bars are arranged in the protective sleeve in the axial direction of the protective sleeve in a parallel mode, one ends of the two optical fiber measuring bars are fixed with the protective sleeve, and the other ends of the two optical fiber measuring bars are suspended in midair to be measured; one of optical fibers is a measuring optical fiber, the end portion of the measuring bar of the measuring optical fiber is provided with a measuring ball stretching out of the protective sleeve, the other of optical fibers is a compensated optical fiber which coats the protective sleeve, and the end portion of the compensated optical fiber forms a closed end through fusion and processing. The ultra-precision micro-displacement sensing system has the advantages of being high in sensitivity, good in stability, large in length-diameter ratio, and strong in anti-interference, and can be widely used for displacement parameter measurement of micro-nano magnitudes of micro devices, microstructures and micro-dimensions.

The invention belongs to the technical field of detection devices, and discloses an automatic detection device for an M-value of a worm and the runout of a tooth surface. The automatic detection device comprises a workbench, wherein the workbench is provided with a clamping unit used for clamping the worm and a measuring unit used for measuring the M-value of the worm and the runout of the tooth surface, the measuring unit comprises a contact portion, a measurement portion, a moving base and a measurement control portion, the contact portion is connected with the measurement portion, the measurement portion is arranged on the moving base, the measurement control portion is connected with the moving base, and the measurement control portion can control the measurement portion and the contact portion to move along a direction parallel to a clamping axis of the worm and a radial direction of the worm so as to enable the contact portion to be contacted with the tooth surface of the worm toperform measurement. The automatic detection device abandons a method of manually detecting the M-value, and improves the detection accuracy through refined component setting. Meanwhile, the automatic detection device is mechanically operated in the whole process, can realize full detection for the M-value of the worm, avoids the risk of manual wrong detection and missed detection and improves the detection efficiency at the same time.

The invention discloses a resonant nano three-dimensional contact measuring head based on an optical fiber Bragg grating. The contact measuring head is characterized in that the structure of the measuring head is designed as follows: an integrated probe with a bulb is fixed in the central point of a suspension support in a T shape, support rods, in the same plane, on the suspension support are in radial distribution. A flexible cantilever and the center of the suspension support are fixed together, far ends of flexible arms, in the same plane, on the flexible cantilever are fixed on an outer connection ring, and a measuring probe is formed. Lower ends of FBG sensors arranged in a packaging layer are fixed at the far ends of the support rods of the suspension support. The upper ends of the FBG sensors are fixed at the edge of a piezoelectric ceramic vibration plate. The piezoelectric ceramic vibration plate is fixedly connected with a displacement output shaft of piezoelectric ceramic through screw threads. The piezoelectric ceramic is fixedly connected onto a bottom surface of a measuring head pedestal through screw threads. The contact measuring head is advantaged by high sensitivity, small measuring force, small microscopic surface active force influence, good long-term stability, good repeatability and low anisotropy.

The invention discloses a quantitative measurement caliper gauge and belongs to measuring instruments. The quantitative measurement caliper gauge is used for measuring the diameters of high-precision shaft type workpieces in the production process in a workshop. The quantitative measurement caliper gauge comprises a dial indicator, a caliper gauge body and a zero calibration device. The caliper gauge body is composed of a web plate, a fixed measuring arm, an elastic measuring arm, a dial indicator fixing frame, a spring and a handle. The zero calibration device is composed of a measurement zero calibration gauge and a measurement zero calibration gauge base. The two edges, in the length direction, of the web plate are parallel. The fixed measuring arm is installed on one edge, in the length direction, of the web plate, the elastic measuring arm and the dial indicator fixing frame are installed on the other edge, in the length direction, of the web plate. A traditional integrated type caliper gauge structure is changed into a separable combination type caliper gauge structure. The quantitative measurement caliper gauge meets the Abbe principle, the measuring force is controlled, the number of links generating errors is reduced, and the measuring precision is improved. The actual sizes of the workpieces can be accurately measured. The quantitative measurement caliper gauge can be used for measurement in the machining process.

The invention discloses a method for high-precision measurement of the sphericity of the micro-spherical probe of a nanometer three-coordinate measuring machine. A tungsten probe with large length-to-diameter ratio and a quartz tuning fork are combined. Scanning probe heads with nanometer-level resolution are constructed based on a precision micro stage. During measurement, the two scanning probe heads are driven by the micro stage to scan the large-section contour of a microsphere in the x-axis direction in a differential manner. Radial error generated in the scanning process can be automatically eliminated in a differential manner, and thus, accurate parameters of the large-section contour of the microsphere can be obtained. After the microsphere is rotated a certain angle, the measurement is repeated to acquire multiple sets of parameters of the large-section contour. A three-dimensional spatial contour of the microsphere is constructed through fitting according to feature points obtained. The geometric parameters of the microsphere are calculated based on the three-dimensional spatial contour. Thus, high-precision measurement of the sphericity of the microsphere is realized. The method has the characteristics of small measuring force, wide measuring range, and high measuring precision.

The invention relates to a PVDF-based tapping-mode high-sensitivity SPM measuring head and a measuring method thereof. The PVDF-based tapping-mode high-sensitivity SPM measuring head is characterized in that a PVDF piezoelectric membrane is taken as a vibrating beam and a tungsten probe is taken as scanning probe; the vibrating beam is set to be a simply supported beam with bended radian; the left end and the right end of the vibrating beam are fixed on front ends of oppositely arranged piezoelectric drivers on both sides through clamping structures respectively; rear ends of the piezoelectric drivers on both sides are fixed on respective cantilever beams respectively; one end of each of the cantilever beams is suspended on a measuring head holder; and the scanning probe is fixed on a center position on the lower surface of the vibrating beam. The measuring method takes the variation of electric charges outputted by the vibrating beam to represent the amplitude variation of the vibrating beam caused by a micrometering force, and performs multipoint micrometering force tapping scanning on a surface to be measured to realize measurement of the surface of a sample. The PVDF-based tapping-mode high-sensitivity SPM measuring head and the measuring method can realize high spatial resolution and low measuring force, are suitable for various materials, and can measure under air environment.

The invention relates to a sensing method and a device for micro inner cavity and two-dimensional coordinate based on one-dimensional micro-focus collimation, belonging to the technical filed of preciThe invention relates to a sensing method and a device for micro inner cavity and two-dimensional coordinate based on one-dimensional micro-focus collimation, belonging to the technical filed of precization, large measured depth-diameter ratio, simple system structure, good real-time performance, easy practical application, and has obvious advantages for carrying out the quick and ultra-precise mezation, large measured depth-diameter ratio, simple system structure, good real-time performance, easy practical application, and has obvious advantages for carrying out the quick and ultra-precise measurement and calibration for the inner cavity micro-size and the two-dimensional coordinate. Especially, the top of the resolution capability can reach the deep sub-nanometer magnitude, and an absoluasurement and calibration for the inner cavity micro-size and the two-dimensional coordinate. Especially, the top of the resolution capability can reach the deep sub-nanometer magnitude, and an absolute zero position exists in the two-dimensional measurement direction.te zero position exists in the two-dimensional measurement direction.se instrument manufacture and measurement, in particular to a sensing method and a device for micro and complex inner cavity structure size and two-dimensional coordinate in the filed of sub-macroscopse instrument manufacture and measurement, in particular to a sensing method and a device for micro and complex inner cavity structure size and two-dimensional coordinate in the filed of sub-macroscopy, which is especially suitable for the measurement of micro-holes with large depth-diameter ratio. By using the structure characteristics of super large curvature and micro-cylindrical lens of an opty, which is especially suitable for the measurement of micro-holes with large depth-diameter ratio. By using the structure characteristics of super large curvature and micro-cylindrical lens of an optical fiber probe measuring rod, a point light source one-dimensional micro-focus collimation imaging light path is established, thereby realizing the high magnification and the sensing of the two-dimeical fiber probe measuring rod, a point light source one-dimensional micro-focus collimation imaging light path is established, thereby realizing the high magnification and the sensing of the two-dimensional displacement of the optical fiber probe measuring rod by utilizing the light path. The invention has the characteristics of small measured force of a single optical fiber probe, easy miniaturinsional displacement of the optical fiber probe measuring rod by utilizing the light path. The invention has the characteristics of small measured force of a single optical fiber probe, easy miniaturi

An exemplary contour measuring probe (10) includes a tip extension (16) and two driving members (13). The tip extension is configured for touching a surface of an object. The driving members are configured for driving the tip extension linearly moving along a first direction. The driving members are tapered and a diameter of each driving member increases along the first direction. The driving members are driven to move by gas pressure acting on an outer side surface thereof.

The invention relates the Mikrokator damping oil and preparing method, comprising 40 parts dimethyl silicon oil and 1.8 parts smoke-silica gel. The Mikrokator has the advantages of gapless, zero friction and high sensibility, the core of Mikrokator is damper system, and the core of damper system is damping oil. The product can be used in Mikrokator.

The invention relates to a method for measuring inside and outside diameter deflection of a soft bearing retainer by means of three-point fix circle-formation. The measurement is conducted by adopting the principle of three-point fix circle-formation. Firstly, an adjustable hand wheel 1 is released so that spherical pivots 4 at two movable rods can move freely. Then, a tightening bolt 7 is released; a meter 6 is pulled outwards along a horizontal sliding groove on a meter bracket mother plate 8; a standard retainer subject to identification is horizontally placed on and stably contacted with a measurement mother plate 3; the positions of the two spherical pivots and a measuring head plate 5 are adjusted so that the spherical pivots and the measuring head plate can be closely contacted with the inside or the outside diameter of the standard retainer; the standard retainer is gently rotated by a hand so as to limitedly rotate within three points defined by the two spherical pivots and the measuring head plate, and meanwhile the meter is adjusted to be at zero; and according to the already-performed positioning, the retainer needing measurement is positioned on the measurement motherplate and then gently rotated for directly measuring whether the outside diameter deflection scope of the measured retainer, which is obtained directly from the meter, conforms to the required scope of the tolerance technique. The method is simple and novel and achieves strong universality, wide application scope and high measurement accuracy.

The invention relates to a sensing method and a device for micro inner cavity size and three-dimensional coordinate based on two-dimensional micro-focus collimation, belonging to the technical filed oThe invention relates to a sensing method and a device for micro inner cavity size and three-dimensional coordinate based on two-dimensional micro-focus collimation, belonging to the technical filed oe, easy miniaturization, large measured depth-diameter ratio, simple system structure, good real-time performance, easy practical application, and has obvious advantages for carrying out the quick ande, easy miniaturization, large measured depth-diameter ratio, simple system structure, good real-time performance, easy practical application, and has obvious advantages for carrying out the quick andultra-precise measurement and calibration for the inner cavity micro-size and the three-dimensional coordinate. Especially, the top of the resolution capability can reach the deep sub-nanometer magni ultra-precise measurement and calibration for the inner cavity micro-size and the three-dimensional coordinate. Especially, the top of the resolution capability can reach the deep sub-nanometer magnitude, and an absolute zero position exists in the three-dimensional measurement direction.tude, and an absolute zero position exists in the three-dimensional measurement direction.f precise instrument manufacture and measurement, in particular to a sensing method and a device for micro and complex inner cavity size and three-dimensional coordinate in the filed of sub-macroscopyf precise instrument manufacture and measurement, in particular to a sensing method and a device for micro and complex inner cavity size and three-dimensional coordinate in the filed of sub-macroscopy, which is especially suitable for the three-dimensional detection of blind holes with large depth-diameter ratio. The device combines a micro spherical biconvex lens and an optical fiber probe measur, which is especially suitable for the three-dimensional detection of blind holes with large depth-diameter ratio. The device combines a micro spherical biconvex lens and an optical fiber probe measuring rod, and establishes a point light two-dimensional micro-focus collimation imaging light path by using the micro spherical biconvex lens, thereby realizing the high magnification and the sensing fing rod, and establishes a point light two-dimensional micro-focus collimation imaging light path by using the micro spherical biconvex lens, thereby realizing the high magnification and the sensing for the three-dimensional displacement of the optical fiber probe measuring rod by utilizing the light path. The invention has the characteristics of small measured force of a single optical fiber probor the three-dimensional displacement of the optical fiber probe measuring rod by utilizing the light path. The invention has the characteristics of small measured force of a single optical fiber prob

The invention provides a vertical variable shear force type direct shear creepmeter which comprises an instrument table, a shear box, a dial indicator and a pressurization system; the shear box is composed of a first box body and a second box body, and the second box body slides downwards relative to the first box body under the action of gravity and a second weight set; the pressurizing system comprises a horizontal axial pressure weight system and a vertical shearing force weight system; the horizontal axial pressure weight system comprises a first weight group; the vertical shearing force weight system comprises a second weight set, the second weight set is placed in a weight container, the weight container is placed in a liquid container, and the bottom of the liquid container is communicated with a plurality of stress control containers in series through pipelines. Cut-off and communication mechanisms are arranged between the adjacent stress control containers and between the liquid container and the stress control containers. According to the invention, the loss of a force value of a traditional direct shear apparatus for converting vertical gravity into horizontal shear force can be avoided, and the shear stress of a soil sample in the shearing process can be controlled to be constant.

The invention relates to a PVDF-based tapping-mode high-sensitivity SPM measuring head and a measuring method thereof. The PVDF-based tapping-mode high-sensitivity SPM measuring head is characterized in that a PVDF piezoelectric membrane is taken as a vibrating beam and a tungsten probe is taken as scanning probe; the vibrating beam is set to be a simply supported beam with bended radian; the left end and the right end of the vibrating beam are fixed on front ends of oppositely arranged piezoelectric drivers on both sides through clamping structures respectively; rear ends of the piezoelectric drivers on both sides are fixed on respective cantilever beams respectively; one end of each of the cantilever beams is suspended on a measuring head holder; and the scanning probe is fixed on a center position on the lower surface of the vibrating beam. The measuring method takes the variation of electric charges outputted by the vibrating beam to represent the amplitude variation of the vibrating beam caused by a micrometering force, and performs multipoint micrometering force tapping scanning on a surface to be measured to realize measurement of the surface of a sample. The PVDF-based tapping-mode high-sensitivity SPM measuring head and the measuring method can realize high spatial resolution and low measuring force, are suitable for various materials, and can measure under air environment.

The invention discloses a V-shaped positioning type inner diameter and outer diameter comparison measuring instrument, which belongs to the technical field of measuring instruments. It has a base and a sliding shaft measurement assembly. The cross-sectional shape of the base is an isosceles right triangle or an ordinary isosceles triangle. There is a rectangular slot along the length direction, and a pair of positioning posts are installed symmetrically on both sides of the axis of the rectangular slot at one end of the base table, and the sliding shaft measuring assembly is installed in the rectangular slot, and the sliding shaft measuring assembly includes a sliding shaft , Install the sliding shaft seat and the clamping table sliding seat on the sliding shaft, install the clamping table seat for clamping the indicator table on the clamping table sliding seat, install a fixed measuring head on one end of the sliding shaft, and the upper and lower ends of the sliding shaft have Eyelets for tying knots. Compared with the prior art, the present invention does not need to readjust the position of the positioning contact for the tested pieces with different diameters, it can measure both the inner diameter and the outer diameter, and has good measurement repeatability and high measurement accuracy.

The invention discloses a device and method for measuring diameters of internal and external raceways of a wind power bearing. The device comprises a ruler and a meter, wherein the left side and the right side of the ruler are respectively provided with a measuring bar, i.e. a left measuring bar and a right measuring bar respectively; the left measuring bar and the right measuring bar can be moved and fixed on the ruler; the left measuring bar and the right measuring bar can also be arranged on the ruler in the reverse direction for measuring; the left measuring bar and the right measuring are vertical to the ruler; the left measuring bar is provided with a fixed measuring head through a left fixed mount; the right measuring bar is provided with a moving measuring head through a right fixed mount; the meter is fastened and connected with the right measuring bar through a fixed bar; and a contact of the meter and the right end surface of the moving measuring head are in elastic contact. The method comprises the steps of adjusting the measuring device, actually measuring and judging whether the diameters of the raceways are qualified or not. The device can be used for measuring the diameters of the internal and the external raceways of the bearing, thereby improving the efficiency and the convenience of the measuring work.

The invention belongs to the technical field of detection devices, and discloses an automatic detection device for the M value of a worm and the runout of a tooth surface. A beating measuring unit, the measuring unit includes a contact part, a measuring part, a moving base and a measuring control part, the contact part is connected with the measuring part, the measuring part is arranged on the moving base, the measuring control part is connected with the moving base, and the measuring control part can be The measuring part and the contact part are controlled to move along the direction parallel to the clamping axis of the worm and the radial direction of the worm, so that the contact part is in contact with the tooth surface of the worm to measure. The invention abandons the method of manually detecting the M value, improves the detection accuracy by refining the setting of the parts, and at the same time, the whole mechanical operation can realize the full inspection of the M value of the worm, avoid the risk of manual error and missed detection, and at the same time improve the detection efficiency.