Abstract: The disclosure relates to a method for the measurement of relative air humidity in a fresh air induction tube of an internal combustion engine. Here a concentration of oxygen in the fresh air induction tube is measured by an oxygen sensor and a temperature in the fresh air induction tube is determined. The relative air humidity is determined depending on the measured concentration of oxygen and the determined temperature.

Abstract: Methods and products for controlling exhaust gas recirculation.

Abstract: An engine control system for an engine equipped with a catalyst that purifies exhaust gas includes: a catalyst temperature acquisition section that acquires the temperature of the catalyst; and a control section that controls an engine such that a rate of increase in engine output speed is changed in accordance with the temperature of the catalyst.

Abstract: In a control device and a method for regulating a combustion process in an internal combustion engine, fuel is injected into the internal combustion engine for combustion, wherein exhaust gas is returned in an intake channel, wherein a combustion point of the combustion is detected, wherein the detected point of time is compared to a target value, wherein depending on the comparison result the injection is changed in order to move the combustion toward the target value, wherein part of the change of the injection is translated into an adaptation value for regulating the exhaust gas return in order to move the combustion in the direction of the target value.

Abstract: An internal EGR amount calculation device for an internal combustion engine, which is capable of properly and easily calculating an internal EGR amount, thereby making it possible to achieve improvement of calculation accuracy and reduction of computational load, even when the degree of fluctuation in an exhaust pressure during a valve overlap time period is large. The internal EGR amount calculation device of the engine includes an ECU. The ECU calculates a minimum exhaust pressure which is a minimum value of an exhaust pressure during the valve overlap time period, and calculates a blown back gas amount according to the minimum exhaust pressure. Further, the ECU calculates an average exhaust pressure and calculates a remaining gas amount according to the average exhaust pressure. Then, the ECU calculates the internal EGR amount based on the remaining gas amount and the blown back gas amount.

Abstract: After completion of warm-up of an engine, upon satisfaction of an exhaust gas recirculation condition by setting the drive mode of a hybrid vehicle to a normal mode according to the driver's accelerator operation, when a power difference ?Pe representing a decrease rate of a power demand Pe* required for the engine is less than a preset reference value ?, the engine and motors MG1 and MG2 are controlled to ensure output of a power equivalent to the power demand Pe* from the engine with prohibition for exhaust gas recirculation via an EGR valve and to ensure output of a torque equivalent to a torque demand Tr* to a ring gear shaft or an axle (steps S300 to S330 and step S390).

Abstract: A dynamic feedforward amount to realize a predetermined transient response characteristic by compensating a transient response characteristic of an engine having a Variable Nozzle Turbo (VNT) and an Exhaust Gas Recirculator (EGR) is calculated for a nozzle opening degree of the VNT and a valve opening degree of the EGR. The transient response characteristic of the engine responds to a setting value of an injection quantity or the like. Then, command values of the nozzle opening degree of the VNT and the valve opening degree of the EGR are calculated by using the dynamic feedforward amount. In the transient state, the followingness to the target value is improved.

Abstract: When an abnormality determining process is cancelled when a fuel cut is stopped, an EGR valve (33), which is open wider than normal from the process, is returned to its original opening amount (i.e., fully closed), and fuel injection in an engine (1) is resumed. However, during execution of the abnormality determining process, an EGR passage (32) is full of air. Also, when the EGR valve (33) is returned to the fully closed state, there is a response delay in the change in the flowrate of air that flows from the EGR passage (32) into the air passage (4) following that return, such that excess air flows into the air passage (4). As a result, the intake air amount of the engine (1) becomes excessive for the fuel injection quantity after fuel injection resumes. The fuel injection quantity is thus increase corrected to inhibit this from happening.

Abstract: An automobile-mount diesel engine with a turbocharger is provided, which includes an engine body with the turbocharger, the engine body being mounted in the automobile and supplied with fuel containing diesel fuel as its main component, a fuel injection valve arranged in the engine body so as to be oriented toward a cylinder of the engine body and for directly injecting the fuel into the cylinder, an injection control module for controlling a mode of injecting the fuel into the cylinder through the fuel injection valve, and an EGR amount control module for adjusting an amount of EGR gas introduced into the cylinder. EGR and fuel injection are adjusted based on speed-load conditions of the engine.

Abstract: An EGR apparatus includes a EGR passage for allowing part of exhaust gas discharged from a combustion chamber of an engine to an exhaust passage to flow in an intake passage and recirculate back to the combustion chamber, and an EGR valve provided in the EGR passage to regulate an EGR passage in this passage. The EGR valve includes a valve seat, a valve element to be seatable on the valve seat, and a step motor for driving the valve element to open and close. An electronic control device controls the EGR valve to repeat opening and closing of the valve element between a closing position and a small opening position in order to remove foreign matters adhered to the valve seat or valve element during deceleration fuel cutoff of the engine.

Abstract: An EGR apparatus includes a EGR passage and an EGR valve provided in the EGR passage to regulate an EGR flow rate in the EGR passage. An ECU closes the EGR valve from an open state prior to start of deceleration of the engine based on engine rotation speed detected by a rotation speed sensor, accelerator opening degree detected by an accelerator sensor, and actual opening degree of the EGR valve. During deceleration of the engine, the ECU obtains a target opening degree of the EGR valve according to the separately detected engine rotation speed and accelerator opening degree from a target opening degree map and starts to close the EGR valve when a difference between an actual opening degree and the target opening degree of the EGR valve exceeds a predetermined value.

Abstract: Provided is a control apparatus of the internal combustion engine capable of removing deposited foreign matters accumulated on an EGR valve without deteriorating a combustion state of the internal combustion engine. When the vehicle is under deceleration and under fuel cut operation, the ECU opens an EGR shutoff valve and obtains an intake pressure “Pclose” under the EGR valve in the fully closed state. Then, the ECU opens the EGR valve and obtains an intake pressure “Popen” under the EGR valve in the fully opened state. Then, the ECU calculates a difference ?P between “Popen” and “Pclose”, and closes the EGR shutoff valve on the condition that the difference ?P is equal to or smaller than a threshold value “Pth1”. Then, the ECU opens the EGR valve, and subsequently opens the EGR valve.

Abstract: An exhaust gas recirculation device for an internal combustion engine includes a return line, which branches off an exhaust tract and leads into an intake tract. A separator component is arranged in the return line. Downstream of the separator component, a gas line, via which additional gas can be supplied, leads into the return line.

Abstract: Method for controlling the power plant of a motor vehicle with partial exhaust gas recirculation in which the fresh air flow rate and the partially recirculated gases flow rate are regulated either on a rich mixture control structure or on a lean mixture control structure and in which the flow rates are set, on the rich mixture control structure, to the setpoint values equal to the flow rate setpoint values of the lean mixture control structure during a transition from a rich mixture control structure to a lean mixture control structure.

Abstract: A method for controlling a fuel injector of a diesel engine having a predefined control time from a control start, in which a setpoint value of a combustion start of a combustion chamber charge of the diesel engine is ascertained. The method is characterized in that an ignition delay between the control start and the combustion start is estimated from performance parameters of the diesel engine using a computing model, and the control start is formed on the basis of the setpoint value of the combustion start and the estimated ignition delay. A control unit controls the sequence of the method.

Abstract: Systems, methods and techniques for exhaust gas recirculation are provided. The system includes a variable venturi device that connects an inlet air supply line and recirculating exhaust gas supply line to an intake manifold supply. A controller in communication with at least one pumping pressure sensor and a flow control element position sensor associated with the variable venturi mixing device is operable to determine a flow rate of the recirculating exhaust gas. The flow rate determination may be used to control NOx emissions during operation of the internal combustion engine.

Abstract: An exhaust gas recirculation control apparatus includes: an EGR valve adjusting a flow rate of EGR gas recirculated from an exhaust manifold to an intake manifold; a manifold absolute pressure (MAP) sensor measuring pressure inside the intake manifold; a throttle valve controlling the amount of inflow air; an igniter spraying fuel; an acceleration pedal angular position sensor; a crank position sensor measuring engine RPM; a vehicle speed sensor measuring a speed of a vehicle; and a control portion receiving a pressure signal from the MAP sensor, calculating a ratio of the EGR gas for a total volume of the intake manifold by using pressure variance inside the intake manifold, calculating pressure of the EGR gas by multiplying the pressure of the intake manifold and the ratio of the EGR gas, and converting the pressure of the EGR gas to a flow rate of the EGR gas.

Abstract: A diesel engine system includes a cylinder, an exhaust manifold, an exhaust gas recirculation (EGR) manifold, and a valve. The exhaust manifold is fluidly coupled with the cylinder and directs exhaust generated in the cylinder to an exhaust outlet that delivers the exhaust to an external atmosphere. The EGR manifold is fluidly coupled with the cylinder and recirculates the exhaust generated in the cylinder back to the cylinder as at least part of intake air that is received by the cylinder. The valve is disposed between the cylinder and the exhaust manifold and between the cylinder and the EGR manifold. The valve has a donating mode and a non-donating mode. The valve fluidly couples the cylinder with the EGR manifold when the valve is in the donating mode and fluidly couples the cylinder with the exhaust manifold when the valve is in the non-donating mode.

Abstract: A valve control apparatus sets a certain soft landing start target position to a drive control unit for carrying out driving of a DC motor 2 as a target open position in response to a fully close command, and sets the target open position which the valve control apparatus acquires by gradually decreasing the soft landing start target position to the above-mentioned drive control unit at a time when the difference between an actual open position and the soft landing start target position becomes equal to a first threshold.

Abstract: In an engine such as an engine for driving a pump or dynamo, in which a load increasing state does not appear as an accelerating state of rotation speed, it is intended to prevent the smoke emission in an abruptly load-increasing state, which might otherwise be caused by the suppression or interruption of an EGR quantity. The engine 10 comprises a supercharger 11 and an exhaust gas recirculation (EGR) device 12. The engine 10 makes an isochronous control or a droop control, when its rotation speed N is shifted from a no-load (idle) or light-load run to a high-load (load-increasing) state. In case it is detected, when the state of the engine 10 shifts to a load state, that the actual rotation speed N becomes lower by a predetermined rotation speed ?N than a target rotation speed Nm, an EGR valve 13 of the exhaust gas recirculation (EGR) device 12 is either throttled to an opening smaller by a predetermined opening ?F than the ordinary set opening F corresponding to the load state or fully closed.

Abstract: An exhaust system and method for optimizing the efficiency of an internal combustion engine from which spent gas emerges. Spent gas is fed to an exhaust housing that accommodates a venturi. Part of the spent gas travels through the venturi and part travels outside the venturi. Across the mouth of the venturi sits a directing valve plate that can be moved, thereby opening or closing the path through the venturi. Some of the spent gas is reflected rearwardly from the venturi and thus reenters the cylinder. Upon doing so, the reflected spent gas occupies some of the space above the piston, lowers combustion pressure and reduces the velocity and pressure of the gas flow emerging therefrom.

Abstract: Methods and systems are provided for improving fuel usage while addressing knock by adjusting the use of spark retard and direct injection of a fluid based on engine operating conditions and the composition of the injected fluid. One or more engine parameters, such as EGR, VCT, boost, throttle position, are coordinated with the direct injection to reduce torque and EGR transients.

Abstract: An EGR control unit for enhancing the performance as to the EGR rate and the engine acceleration, the unit being configured so as to control the EGR valve and the intake air valve with a simple control command signal that makes both the valves be operated in a coupled mode, whereby the response performance as to the engine speed during acceleration as well as the EGR gas flow rate is enhanced by means of compensation regarding the dead zones inherent in the intake air throttle valve and the EGR valve.

Abstract: A valve system includes a conical valve body disposed in an engine gaseous fluid stream and having a first fluid passageway, where the conical valve body is a cone or a frustum of a cone. The system includes a fluid inlet conduit fluidly coupled to the conical valve body on an upstream side, a first fluid outlet conduit, and a second fluid outlet conduit. The first and second fluid outlet conduits are fluidly coupled to the conical valve body on a downstream side. The valve system includes a valve actuator operatively coupled to the conical valve body and that rotates the conical valve body, and a controller that provides a valve actuator command and thereby selectively flows the engine gaseous fluid stream through the first fluid outlet conduit and the second fluid outlet conduit.

Abstract: An abnormality determination system for an internal combustion engine includes a plurality of EGR gas supply sections, an EGR gas supply control unit, an air-fuel ratio sensor placed downstream of an exhaust collecting portion, and an abnormality determining unit that determines an abnormality in the internal combustion engine. The abnormality determining unit obtains a change rate corresponding value during shutoff of the EGR gas or during supply of the EGR gas, as an EGR-OFF corresponding value or an EGR-ON corresponding value. The abnormality determining unit obtains a normalized EGR-OFF corresponding value, and obtains a normalized EGR-ON corresponding value. The abnormality determining unit makes an abnormality determines whether one of the EGR gas supply sections is in an abnormal condition in which the EGR gas supply section is blocked, based on a relationship between the normalized EGR-OFF corresponding value and the normalized EGR-ON corresponding value.

Abstract: A control system for an engine includes a feedback determination module, a feed-forward determination module, and a valve control module. The feedback determination module generates an exhaust gas recirculation (EGR) feedback value based on engine speed and a difference between desired and measured combustion phasing. The feed-forward determination module generates an EGR feed-forward value based on a difference between desired and measured mass air flow (MAF) rates. The valve control module controls an EGR valve based on the EGR feedback and feed-forward values, an intake manifold absolute pressure (MAP), an engine speed, and an exhaust back pressure (EBP).

Abstract: An exhaust gas control system for an internal combustion engine includes a turbocharger that includes a compressor arranged in an intake passage, and a turbine arranged in an exhaust passage; a low-pressure EGR unit that recirculates a portion of exhaust gas back to the internal combustion engine through a low-pressure EGR passage that provides communication between the exhaust passage, at a portion downstream of the turbine, and the intake passage, at a portion upstream of the compressor; a low-pressure EGR valve that is provided in the low-pressure EGR passage, and that changes the flow passage area of the low-pressure EGR passage; and a valve control unit that executes an opening/closing control over the low-pressure EGR valve. When it is determined that the internal combustion engine is under a predetermined low-temperature environment, the low-pressure EGR valve is kept closed while the internal combustion engine is in the fuel-supply cutoff operation mode.

Abstract: A method for operating an internal combustion engine includes providing at least one gas exchange valve that is used by at least one of the working cylinders of the internal combustion engine as an exhaust-gas recirculation valve. In a predetermined operating state of the internal combustion engine, the exhaust-gas recirculation valve is opened at least twice within a working cycle of 720 degrees of the crankshaft, wherein an opening duration of the first opening of the exhaust-gas recirculation valve at least overlaps in time with an opening of the outlet valve during the exhaust stroke and wherein an opening duration of the second opening of the exhaust-gas recirculation valve at least overlaps in time with an opening duration of the inlet valve during the intake stroke, wherein the exhaust-gas recirculation valve is closed between the first opening and the second opening.

Abstract: In a low-pressure EGR system, a mechanical stopper limits a rotation range of a low-pressure EGR regulating valve at a limit opening degree of the low-pressure EGR regulating valve on its fully-open side and outside an EGR amount adjustment opening degree range of the low-pressure EGR regulating valve. After an engine is stopped, a failure detection unit rotates the low-pressure EGR regulating valve to its fully-open position to such an extent that rotation of a linking device is prevented by the mechanical stopper, and is configured to determine that a failure has occurred when an opening degree of the low-pressure EGR regulating valve detected by a low-pressure EGR opening sensor is different from the limit opening degree of the low-pressure EGR regulating valve.

Abstract: A control system for a homogeneous charge compression ignition (HCCI) engine includes a timing adjustment module and a combustion control module. The timing adjustment module, per combustion event, advances timings of N fuel injections and retards timings of M fuel injections and spark during a transition from HCCI combustion to mixed-mode combustion. The combustion control module subsequently retards the timings of the N fuel injections and advances the timings of the M fuel injections and the spark to desired timings, respectively, wherein the N fuel injections and the M fuel injections occur sequentially during each combustion event of the HCCI engine, and wherein N and M are integers greater than or equal to zero.

Abstract: A system and method for measuring an EGR flow rate for an engine having an EGR valve with a selectable EGR valve position and a venturi sensor situated to take a differential pressure measurement relative to recirculated exhaust gas includes determining an EGR valve effective area based on the EGR valve position, determining a weighting factor based on the effective area, calculating a first EGR flow estimate based on the effective area, and calculating a second EGR flow estimate based on the differential pressure measurement of the venturi sensor. A final EGR flow rate is determined based on the weighting factor, the first EGR flow estimate, and the second EGR flow estimate.

Abstract: An EGR flow rate control apparatus of an internal combustion engine is provided that can correct with high accuracy an EGR gas flow rate measured by a gas flow rate measurement apparatus in an EGR passage and control with high accuracy a gas flow rate regulating valve to reduce discharge amounts of PM and NOx in exhaust gases. An EGR flow rate control apparatus 10 of an internal combustion engine includes a gas flow rate correction unit 45 that corrects the EGR gas flow rate based on a first operating state parameter relating to pressure fluctuations of the intake pipe or exhaust pipe of the internal combustion engine and a second operating state parameter relating to a flow channel resistance of the EGR flow channel.

Abstract: An internal combustion engine includes at least two cylinders, an intake duct, an exhaust gas section and an exhaust gas recirculation line. The cylinders include a combustion chamber. The intake duct communicates with the combustion chambers via a cylinder inlet channel of the intake duct depending upon a switch position of a gas inlet valve. The exhaust gas section communicates with the combustion chambers depending upon a switch position of at least one gas outlet valve. Exhaust gas is guided back to the inlet channels via the exhaust gas recirculation line dependent upon a switch position of the exhaust gas recirculation valve. To detect a mixing air temperature in the inlet channels, a mixing air temperature sensor is provided. The determined mixing air temperatures are compared. Exhaust gas guided back due to uneven distribution is identified if a difference between the determined mixing air temperature is greater than a predetermined threshold value.

Abstract: An engine control system for a homogeneous charge compression ignition (HCCI) engine includes a position determination module, a position correction module, and a valve control module. The position determination module determines an initial position of an exhaust gas recirculation (EGR) valve based on a predetermined function of a desired EGR flow, intake manifold pressure, exhaust manifold pressure, and exhaust gas temperature. The position correction module determines a position correction for the EGR valve based on pressure in a cylinder of the HCCI engine. The valve control module commands the EGR valve to the initial position during a transition from spark ignition (SI) combustion to HCCI combustion, and commands the EGR valve to a final position within a predetermined period after the transition, wherein the final position includes a sum of the initial position and the position correction.

Abstract: To accurately specify an EGR rate from an output value of an in-cylinder pressure sensor, a specifying method of an EGR rate in an internal combustion engine of the present invention acquires an output value of an in-cylinder pressure sensor at an intake stroke to calculate comparison data related to an in-cylinder pressure at the intake stroke from the acquired sensor output value. An output value of the in-cylinder pressure sensor at an exhaust stroke of the same cycle is also acquired to calculate comparison data related to the in-cylinder pressure at the exhaust stroke from the acquired sensor output value. Two comparison data are compared to specify the EGR rate of an air-fuel mixture provided for combustion from a difference between the values.

Abstract: An engine starting method is disclosed. In one example, engine operation is adjusted to reduce catalyst light off time. Exhaust temperatures may be increased until a threshold engine temperature is reached.

Abstract: Methods and systems are provided for improving fuel usage while addressing knock by adjusting the use of spark retard and direct injection of a fluid based on engine operating conditions and the composition of the injected fluid. One or more engine parameters, such as EGR, VCT, boost, throttle position, are coordinated with the direct injection to reduce torque and EGR transients.

Abstract: A method for operating an engine is disclosed. In one example, the method adjusts a torque limit of the engine in response to an amount of EGR in an engine cylinder. The approach may reduce the possibility of pre-ignition for boosted engines.

Abstract: An internal combustion engine and control system are provided having improved efficiency through improved exhaust flow control. The engine includes at least one bank of combustion cylinders and a respective exhaust manifold for conveying exhaust to the atmosphere. Further included is an exhaust gas restriction valve (ERV) associated with the exhaust manifold for selectively increasing backpressure on the associated bank of combustion cylinders and for redirecting a portion of the exhaust into an exhaust gas conditioning system for conditioning the portion of the exhaust and returning it to an air intake of the engine. An engine exhaust gas recirculation (EGR) valve in the exhaust gas recirculation system restricts the flow of conditioned exhaust, and an EGR flow controller operates the EGR valve in one of a substantially open and substantially closed condition and controls the flow of conditioned exhaust to the air intake by modulating the ERV.

Abstract: The present invention provides for a method and apparatus for measuring and controlling the EGR rate in a combustion engine system, comprising an EGR cooler, an EGR valve and a turbine, and determining the EGR mass flow (dmEGR) from the difference between the total exhaust gas mass flow (dmTot) across the engine cylinders, and the turbine mass flow (dmTurb) across the turbine.

Abstract: When a constant driving voltage is applied to a motor driving an EGR valve so that the EGR opening degree is varied, an angular speed of the EGR valve becomes minimal at a position where the driving torque of the EGR valve becomes maximal. In view of this, while an opening degree of the EGR valve is varied with a constant driving voltage applied to the motor, the EGR opening degree where the angular speed becomes minimal is learned as a full-close position.

Abstract: An internal combustion engine exhaust gas system includes a filter arranged in an exhaust passage of the internal combustion engine, a fuel adding valve which is arranged upstream of the filter and supplies fuel into the exhaust passage, and a low-pressure exhaust gas recirculation apparatus that removes some of the exhaust gas from downstream of the filter as EGR gas. An EGR rate is controlled taking into account the amount of fuel supplied by the fuel adding valve such that an oxygen concentration of intake gas, which is drawn into a cylinder of the internal combustion engine in a state in which the EGR gas that is introduced by the low-pressure exhaust gas recirculation apparatus is mixed with air introduced into an intake passage, is constant before and after fuel is supplied by the fuel adding valve.

Abstract: A valve module for a combustion engine breathing system, and products and systems using the same.

Abstract: An apparatus, system, and method are disclosed for efficiently operating an engine utilizing exhaust gas recirculation (EGR). The apparatus includes an exhaust manifold receiving exhaust gas from a first cylinder set, an EGR manifold receiving exhaust gas from a second cylinder set, and a passage comprising a variable restriction. The passage fluidly couples the exhaust manifold to the EGR manifold. The apparatus further includes a controller with modules for interpreting engine operating conditions and controlling actuators in response to the engine operating conditions.

Abstract: A working gas circulation type engine includes a combustion chamber in which a working gas having a ratio of specific heats higher than that of air can be expanded by combustion of a fuel, a circulation path capable of circulating a gas containing the working gas from a gas exhaust side to a gas suction side of the combustion chamber and supplying the gas containing the working gas to the combustion chamber again, and a control device that changes a control parameter for controlling the combustion of the fuel based on a ratio of specific heats of the gas circulating in the circulation path. Therefore, there can be provided the working gas circulation type engine capable of obtaining a stable output.

Abstract: First, an amount of external EGR gas is adjusted so that an amount, by which an amount of internal EGR gas is adjusted, falls within a predetermined range (S102 to S104), and, then, the amount of internal EGR gas is adjusted when the amount, by which the amount of internal EGR gas is adjusted, falls within the predetermined range (S105 to S109) in order to execute a feedback control so that an EGR rate, which indicates a proportion of EGR gas including the external EGR gas and the internal EGR gas to intake air that is supplied to the internal combustion engine, matches a target EGR rate.

Abstract: An engine starting method is disclosed. In one example, engine operation is adjusted to reduce catalyst light off time. Exhaust temperatures may be increased until a threshold engine temperature is reached.

Abstract: In an EGR valve provided in an exhaust gas recirculation passage for recirculating the exhaust gas of an engine, a filter 26b is provided on the side of an exhaust gas passage 22 of a bearing 26a supporting a valve rod 25, while a diameter-reduced section 25a is provided in an area on the valve rod 25 in proximity to the filter 26b.

Abstract: A condensation control system for a vehicle comprises a short route (SR) target module, a long-route (LR) target module, and a humidity adjustment module. The SR target module controls a first opening target for opening of a first exhaust gas recirculation (EGR) valve and a first throttle valve based on a SR target and a SR adjustment. The LR target module controls a second opening target for opening of a second EGR valve and a second throttle valve based on a LR target and a LR adjustment. The humidity adjustment module adjusts the SR and LR adjustments based on a humidity adjustment when condensation is detected in a system that provides a gas to an engine for combustion and determines the humidity adjustment based on a difference between a humidity within the system and a predetermined humidity.

Abstract: Systems and methods for using pedal position and/or pedal change rate in the fuel side and/or air side control of an engine. By knowing the pedal position and/or pedal rate, an engine controller may anticipate future fuel and/or air needs of the engine, and adjust the fuel profile and/or air profile to meet those anticipated needs. This may help improve the responsiveness, performance and emissions of the engine.