Abstract: The engine (10) includes a low spool (16) disposed aft of an air inlet (12) and a high spool (34) disposed aft of the low spool (16). An intake reverse-duct (44) is disposed radially outward of the high spool (34) and reverses direction of low pressure compressed air from the low spool (16) into a forward-flow high pressure compressor (40) of the high spool (34). A discharge reverse-manifold (48) directs flow of an exhaust gas stream (50} from a forward-flow low pressure turbine (20) into a rearward-flow direction and into at least one pulse detonation firing tube (54). An annular bypass air duct (72) directs cooling air along the engine (10)—The at least, one firing tube is positioned radially outward of the high spool (34), overlies the high spool (34) and is also positioned within the bypass air duct (72).

Abstract: A process for treating a waste feedstock using a gasifier and the gasifier for same. Hot exhaust from an engine travels through a series of hollow heating plates stacked vertically within a gasifier reactor with spaces between each set of successive heating plates forming reaction zones. Each reaction zone is divided into an upper treatment area and a lower treatment area by a rotating disk. Waste material travels from an outer feed spot along the top surface of the rotating disk radially inwardly to a drop area located at the radially innermost portion where it drops to the top surface of the hollow heating plate below. The waste material is then conveyed radially outward to a chute to the next reaction zone or once fully processed to an exit from the reactor. Vapors from the waste material are drawn off each reaction zone through an outlet for further processing.

Abstract: A gas turbine engine comprises a fan on an engine central axis. Plural gas generators are downstream of the fan, each along a respective central axis, mutually offset, and offset from the engine central axis. A fan drive turbine is on the engine central axis, downstream of the dual gas generators, and driven by output from the dual gas generators, to drive the fan.

Abstract: A spinner for a fan assembly of a gas turbine engine, a method of fabricating a spinner for a fan assembly of a gas turbine engine, and a gas turbine engine are disclosed. The fan section may include a nosecap. The spinner may include a forward end, an aft end, and a return flange associated with the forward end. The return flange may include a forward flange extending forward towards the nosecap and an aft flange extending aft towards the aft end.

Abstract: Embodiments of a gas bearing for aircraft engines are provided herein. In some embodiments, a gas bearing may include a first shaft; a second shaft disposed concentrically about the first shaft; and a protrusion extending from at least one of an inner surface of the first shaft or the outer surface of the second shaft to form a gap between the first shaft and the second shaft.

Abstract: A heat exchanger in the form of a honeycomb with a plurality of rectangular or otherwise polygon in cross-section passages which share common walls with adjacent passages. Two or more flow paths each comprises a plurality of serially connected passages. Each flow path passes through the heat exchanger in a helical pathway, thus through one passage in a first vertical stack of passages, then through a lower passage in an adjacent second vertical stack of passages, then through a lower passage in the first vertical stack, then through a lower passage in the second vertical stack and in this helical manner to the outlet from the heat exchanger. Thus, the flow path comprises alternate passages in each vertical stack, and another flow path comprises the alternate passages in at least one of the vertical stacks not taken up by the first flow path, whereby the flow paths at least partially overlap each other thereby providing both counter-flow and co-flow.

Abstract: A gas turbine engine including an outer case and an exhaust gas passage defined within the outer case for conducting an exhaust gas flow from a turbine section of the gas turbine engine. A cooling channel is associated with an outer surface of the outer case, the cooling channel having a channel inlet and a channel outlet. An air duct structure is provided and includes an inlet end in fluid communication with the channel outlet and includes an outlet end in fluid communication with an area of reduced pressure relative to the air duct structure inlet end. An exit cavity is located at the air duct structure outlet end, wherein the exit cavity effects a reduced pressure at the outlet end to draw air from the cooling channel into the air duct.

Abstract: A gas turbine engine includes a nacelle, a lower bifurcation structure, and a heat exchanger. The nacelle extends circumferentially around an engine core and defines a fan bypass duct that is substantially annular between an inner wall and an outer wall. The lower bifurcation structure extends between the inner wall and the outer wall, bifurcating the fan bypass duct. The lower bifurcation structure defines a bifurcation duct extending along a central axis of the lower bifurcation structure. A heat exchanger is positioned in the bifurcation duct.

Abstract: A component according to an exemplary aspect of the present disclosure includes, among other things, a body portion and a cooling scheme disposed inside the body portion, the cooling scheme including a vascular engineered lattice structure and a heat transfer device adjacent to the vascular engineered lattice structure.

Abstract: A means of attachment applicable to mating parts which have substantially different coefficients of thermal expansion is disclosed. The means of attachment substantially reduces the friction between the mating surfaces while still keeping the mating parts centered with respect to one another. The approach is based on radial recessed faces wherein the radial faces slide relative to each other. There may be three or more recessed/raised faces on each mating component, which when mated, maintain the alignment between the mating parts while allowing differential growth of the mating parts. This approach also the provides a much larger bearing surface for the attachment than a radial pin/slot approach, for example, and substantially eliminates areas of high stress concentration. It is thus a more robust design for components that undergo many thousands of thermal cycles.

Abstract: A fuel injection system for a gas turbine engine includes a fuel nozzle with a fuel injection aperture to inject a fuel jet and a multiple of airflow passages in the fuel nozzle to communicate a multiple of air streams to interact with the fuel jet.

Abstract: A two-shaft gas turbine is provided which includes: a compressor; a combustor having multiple fuel systems and generating combustion gas by combusting fuels from the fuel systems and air compressed by the compressor; a high-pressure turbine coupled coaxially with the compressor and rotated by the combustion gas; a low-pressure turbine having a shaft structure independent of the high-pressure turbine and rotated by exhaust gas from the high-pressure turbine; an air extraction channel for extracting the air compressed by the compressor; an injection flow channel for feeding the air extracted through the air extraction channel back to the combustor; and a controller for controlling the flow rate of the fuel supplied to each of the fuel systems based on the air flow rate of the compressor, on the flow rate of the fuel supplied to the combustor, and on the temperature of the air in the injection flow channel.

Abstract: A geared fuel pump (4?) operates to supply a determined flow but at low or zero pressure rise. It is planned to add gland packing (46) between support bearings (19) of the pinions (11), or between some of them, to provide hydrodynamic lift for these bearings, by delimiting a closed cavity (47) to provide lift by a fluid with better viscosity properties instead of using the fluid itself that is pumped. Possible application to fuel pumps for aircraft engines, in which the pump (4?) is a high pressure pump associated with a low pressure pump.

Abstract: A method for controlling fuel flow to a gas turbine engine during starting includes monitoring acceleration of the gas turbine engine to determine actual acceleration value, and calculating a fuel flow rate for a setpoint acceleration using the actual acceleration value as a factor. The method further includes commanding the calculated fuel flow for the setpoint acceleration to the gas turbine engine.

Abstract: There is described a method and system for in-flight start of an engine. The method comprises rotating a propeller; generating electrical power at an electric generator embedded inside a propeller hub from rotation of the propeller; transmitting the electrical power from the electric generator to an engine starter mounted on a core of the engine via an electric power link; and driving the engine with the engine starter to a sufficient speed while providing fuel to a combustor to light the engine to achieve self-sustaining operation of the engine.

Abstract: A multi spool gas turbine engine with a differential having a selectively rotatable member which rotational speed determines a variable ratio between rotational speeds of driven and driving members of the differential. The driven member is engaged to the first spool and a rotatable shaft independent of the other spools (e.g. connected to a compressor rotor) is engaged to the driving member. First and second power transfer devices are engaged to the first spool and the selectively rotatable member, respectively. A circuit interconnects the power transfer devices and allows a power transfer therebetween, and a control unit controls the power being transferred between the power transfer devices. Power can thus be transferred between the first spool and the selectively rotatable member to change the speed ratio between the first spool and the rotatable shaft.

Abstract: A gas turbine engine has a compressor rotor with blades and a disk. A bore is defined radially inwardly of the disk. A combustor includes a burner nozzle. A tap taps air that has been combusted in the combustor section through a valve, and into the bore of the disk. A method is also disclosed.

Abstract: In order to enhance the tracking performance of power generation equipment with respect to a load variation and increase the reliability of the power generation equipment, a dynamic characteristic model simulating the dynamic characteristics of a multi-shaft gas turbine is used to calculate an output prediction value of a first power generator in a case where a combustor is controlled so as to match the output of the first power generator to an output target value; on the basis of the output target value and the output prediction value of the first power generator, a first power generator output instruction value as an instruction value for the output from the first power generator to a power system and a second power generator output instruction value as an instruction value for the output from a second power generator to the power system are calculated; and the combustor is controlled on the basis of the first power generator output instruction value and a frequency convertor is controlled on the basis of t

Abstract: An ecology system includes an ecology tank, a check valve, a shutoff valve, and an ejector pump. The check valve is fluidly connected to the ecology tank and is configured to allow flow from the ecology tank. The shutoff valve is fluidly connected to the check valve, and the ejector pump is fluidly connected to the shutoff valve. The ejector pump is configured to draw fuel from the ecology tank when the shutoff valve is in an open configuration.

Abstract: A control system of at least one flap of a fluid duct of an intake system of an internal combustion engine, including: a swivel axis, at least one flap connected off-center to the swivel axis by which the at least one flap can be swiveled within the fluid duct between positions with different degrees of opening, a swivel lever connected to the swivel axis, the swivel lever pivoting the swivel axis, an elastic working return element connected directly or indirectly to the swivel lever and applying a force to the at least one flap to return the at least one flap toward a home position.

Abstract: A system according to the principles of the present disclosure includes an engine actuator control module and at least one of a valve lift control module and a cylinder activation module. The valve lift control module adjusts a target lift state of a valve actuator of an engine to adjust an amount by which at least one of an intake valve of a cylinder of the engine and an exhaust valve of the cylinder is lifted from a valve seat. The cylinder activation module determines a target number of activated cylinders in the engine. The engine actuator control module that controls a first actuator of the engine at a present time based on at least one of the target lift state at a future time and the target number of activated cylinders at the future time. The first actuator is different than the valve actuator.

Abstract: A controller is applied to such an internal combustion engine that an exhaust throttle valve for controlling the flow volume of exhaust gas of the exhaust passage is provided in the exhaust passage, an intake variable valve mechanism for changing the timing of opening and closing each intake valve or an exhaust variable valve mechanism for changing the timing of opening and closing each exhaust valve is provided, and an overlap period when an opening period of the intake valve and an opening period of the exhaust valve overlap with each other can be provided, and controls the exhaust throttle valve so that an opening degree of the exhaust throttle valve in the overlap period is made smaller than an opening degree of the exhaust throttle valve in a case where the overlap period is not provided.

Abstract: A hydraulic camshaft adjuster for changing the control times of gas exchange valves of an internal combustion engine, designed as a vane cell camshaft adjuster. A control device inserted in the vane selectively opens and interrupts a flow connection between the working chambers. A locking device prevents relative motion between the rotor and the stator in that the rotor is fastened to the stator at a vane position. A switching valve, which has three working ports, a P port and a T port, can be moved into different control positions by an adjusting element,—wherein in the control position, the P port communicates with the working chambers via the A port, the B port is blocked at the switching valve, and the T port communicates with the control device of the vanes via the C port.

Abstract: A reciprocating engine includes an engine body presenting an internal chamber and a fluid intake that supplies intake fluid to the internal chamber. The engine also includes a piston that oscillates within the internal chamber during engine operation. The engine body includes a block and a head that form the internal chamber.

Abstract: Systems and methods for determining operation of a cylinder deactivating/reactivating device are disclosed. In one example, a direction of engine rotation is selected to maximize air flow through the engine while the engine is rotated without combusting air and fuel. Operation of one or more cylinder valve deactivating mechanisms is assessed while the engine is rotated without combusting air and fuel.

Abstract: A gasoline Reid vapor pressure (RVP) detection system includes a fuel pump and a motor operating the fuel pump in a forward direction of rotation to feed a gasoline fuel to a vehicle engine. A control device is in communication with the motor selectively directing change from the forward direction of rotation to a reverse direction of rotation opposite to the forward direction of rotation. A pressure reduction device receives flow of the fuel during operation in the reverse direction of rotation and reduces a pressure of the fuel until fuel vaporization occurs. A pump speed at which vaporization of the fuel occurs at the pressure reduction device when a motor speed and a motor current change non-linearly is correlated to a fuel RVP.

Abstract: Advanced combustion modes, such as PCCI, operate near the system stability limits. In PCCI, the combustion event begins without a direct combustion trigger in contrast to traditional spark-ignited gasoline engines and direct-injected diesel engines. The lack of a direct combustion trigger encourages the usage of model-based controls to provide robust control of the combustion phasing. The nonlinear relationships between the control inputs and the combustion system response often limit the effectiveness of traditional, non-model-based controllers. Accurate knowledge of the system states and inputs is helpful for implementation of an effective nonlinear controller. A nonlinear controller is developed and implemented to control the engine combustion timing during diesel PCCI operation by targeting desired values of the in-cylinder oxygen concentration, pressure, and temperature during early fuel injection.

Abstract: A target first air amount for achieving a requested torque by an operation of an intake property variable actuator is calculated by using a first parameter. A target second air amount for achieving the requested torque by an operation of a turbocharging property variable actuator is calculated by using a second parameter. A value of a first parameter changes to a value that reduces a conversion efficiency of an air amount into torque in response to the requested torque decreasing to a first reference value or lower. Further, a value of the second parameter starts to change to a direction to reduce the conversion efficiency in response to the requested torque decreasing to a second reference value that is larger than the first reference value, or lower, and gradually changes to a direction to reduce the conversion efficiency in accordance with the requested torque further decreasing from the second reference value to the first reference value.

Abstract: The systems, methods, and apparatuses provided herein disclose interpreting a performance criteria for a vehicle, wherein the performance criteria is indicative of a desired operating parameter for the vehicle; interpreting a good driver definition value indicative of a good driver profile for the interpreted performance criteria; determining a performance value indicative of how an operator of the vehicle is performing with respect to the good driver definition value; and in response to the performance value indicating that the vehicle is not satisfying the performance criteria, managing an actuator output response value for at least one actuator in the vehicle to facilitate achievement of the good driver definition value.

Abstract: An engine device executes the control of the opening degree of a main throttle valve when engine load is in a low load area. In contrast, when the engine load is in a medium-to-high load area, the engine device sets the main throttle valve to a predetermined opening degree and executes the control of the opening degree of an air supply bypass valve.

Abstract: Methods and systems are provided for operating a split exhaust engine system that provides blowthrough air and exhaust gas recirculation to an intake passage via a first exhaust manifold and exhaust gas to an exhaust passage via a second exhaust manifold. In one example, a first set of exhaust valves coupled to the first exhaust manifold may be operated at a different timing than a second set of exhaust valves coupled to the second exhaust manifold. Further, a position of a first valve positioned in a first passage coupled between the intake passage and the first exhaust manifold and/or a timing of the first set of exhaust valves may be diagnosed based on an output of a pressure sensor positioned in the first exhaust manifold.

Abstract: A method for correcting an air-fuel ratio deviation for each cylinder in an engine of a vehicle includes measuring a signal of an oxygen sensor mounted on an exhaust pipe of the vehicle using a low-pass filter and a moving-average filter; calculating an oxygen sensor roughness based on the measured signal of the oxygen sensor modulating a fuel injection amount of fuel injected into each cylinder in the engine; detecting a variation of the oxygen sensor roughness according to the modulated fuel injection amount; determining an optimal fuel injection amount based on a relationship between the fuel injection amount and the oxygen sensor roughness; performing fuel injection amount control based on the determined optimal fuel injection amount to correct the air-fuel ratio deviation for each cylinder.

Abstract: A method to adjust an oil control valve actuation response time using cylinder valve diagnostic results includes commanding an engine cylinder to deactivate/reactive when conditions are met and then detecting if a deactivation/reactivation response time failure has occurred by analyzing the cylinder diagnostics results. If a predetermined number of failures are detected at the cylinder within a predetermined number of engine cycles then the engine controller operates to adjust the oil control valve response time to improve the response time accuracy.

Abstract: A variety of methods and arrangements are described for controlling transitions between firing fractions during skip fire or other dynamic firing level modulation operation of an engine. In general, actuator first transition strategies are described in which an actuator position (e.g., cam phase, TCC slip, etc.) is changed to, or close to a target position before a corresponding firing fraction change is implemented. When the actuator change associated with a desired firing fraction change is relatively large, the firing fraction change is divided into a series of two or more firing fraction change steps. A number of intermediate target selection schemes are described as well.

Abstract: A method of regenerating a selective catalytic reduction catalyst on a diesel particulate filter (SDPF) includes predicting a reducing agent amount oxidized in the SDPF during regeneration of the SDPF if the regeneration of the SDPF is necessary; calculating a quantity of heat generated from the reducing agent amount oxidized in the SDPF; calculating a temperature change from the generated quantity of heat; calculating a target temperature when regenerating the SDPF; and performing the regeneration according to the target temperature.

Abstract: A rotational speed control apparatus for an engine that drives an air conditioning compressor includes an electronic control unit. The electronic control unit corrects a calculated value of a load torque of a compressor in accordance with a deviation between a rotational speed of the engine and a target rotational speed, as a changeover transition period control, in a changeover transition period. The electronic control unit also sets an execution period of the changeover transition period control such that the execution period in a changeover transition period from the stopped state to the driven state of the compressor is longer than an execution period of the changeover transition period control in a changeover transition period from the driven state to the stopped state of the compressor.

Abstract: A control apparatus for an internal combustion engine (i) acquires a rotational speed signal correlated with a rotational speed of the internal combustion engine, (ii) extracts, from the acquired rotational speed signal, at least first-order and lower-order than the first-order components of the rotational speed signal, (iii) extracts, from the acquired rotational speed signal, at least an n-th-order component of the rotational speed signal, (iv) determines that no disturbance has occurred when a first-order parameter regarding a magnitude of an amplitude of the extracted first-order and lower-order than the first-order components is smaller than a first threshold, and (v) determines that a disturbance has occurred when the first-order parameter is equal to or larger than the first threshold and an n-th-order parameter regarding an amplitude of the extracted n-th-order component is equal to or larger than a second threshold.

Abstract: A method and system for blending between different torque maps of a vehicle so that step changes of torque output are avoided as accelerator pedal position is changed. Different blending rates are provided so as to reduce the blending time if driver demand is in the direction of torque change.

Abstract: An internal combustion engine control device to control a fuel injection valve includes: valve-close delay time acquisition circuitry configured to acquire a valve-close delay time of the fuel injection valve; first learning value calculation circuitry configured to calculate a first learning value based on the valve-close delay time when a running state of an internal combustion engine satisfies a predetermined learning condition; valve-open time calculation circuitry configured to calculate a valve-open time of the fuel injection valve based on the first learning value; second learning value calculation circuitry configured to calculate a second learning value based on the valve-close delay time irrespective of the running state of the internal combustion engine; and learning state determination circuitry configured to determine a learning state of the first learning value based on a relationship between the first learning value and second learning value.

Abstract: Various methods are provided for operating a fuel pump. In one example, a method of operating a fuel pump comprises iteratively reducing an on-duration of a low pressure fuel pump pulse, until a peak outlet pressure of the fuel pump decreases from a peak outlet pressure corresponding to a previous pulse, to identify a minimum pulse duration, and applying a pulse having the minimum pulse duration to the fuel pump.

Abstract: Methods and systems are provided for reducing fueling errors resulting from pressure pulsations in a port injection fuel rail. The pressure pulsations result from pressure pulsations generated in a high pressure fuel pump delivering fuel to both the port injection fuel rail and a direct injection fuel rail. A center of a port injection fuel pulse is repositioned on a nearest fuel rail pressure sampling point in the advanced direction to improve the accuracy of the delivered fuel pulse.

Abstract: Controlling a marine engine includes operating the engine according to an initial set of mapped parameter values to achieve a first target fuel-air equivalence ratio, determining a first actual fuel-air equivalence ratio, and using a feedback controller to minimize a difference between the first target and actual ratios. Feedback controller outputs are used to populate an initial set of adapt values to adjust combustion parameter values from the initial set of mapped parameter values. The method includes transitioning to operating the engine according to a subsequent set of mapped parameter values to achieve a different target fuel-air equivalence ratio. The method includes determining a second actual fuel-air equivalence ratio, using the feedback controller to minimize a difference between the second target and actual ratios, and using feedback controller outputs to populate a subsequent set of adapt values to adjust combustion parameter values from the subsequent set of mapped parameter values.

Abstract: Technical solutions are described for measuring fuel injection to an engine of a vehicle. For example, an engine control unit (ECU) that controls the operation of the engine, is equipped with a first direct memory address channel to store rail pressure values that are received from the engine in a first buffer. The ECU further includes a second direct memory address channel configured to copy a first subset of the rail pressure value from the first buffer to a filter module in response to an angle-based interrupt request. The ECU further includes a third direct memory address channel configured to copy filtered pressure values from the filter module to a second buffer. The ECU also includes a processor that computes a pressure drop based on the filtered pressure values from the second buffer, and compute a quantity of fuel injected into the engine based on the pressure drop.

Abstract: A control apparatus for an internal combustion engine is configured, during a slightly stratified-charge lean-burn operation, to: calculate a basic total fuel injection amount based on a required torque; calculate a compression stroke injection amount based on an ignition delay index value; calculate, as a basic main injection amount, a value obtained by subtracting a compression stroke injection amount from the basic total fuel injection amount; calculate, based on an output value of an in-cylinder pressure sensor, an actual specified combustion index value that represents a main combustion speed or a combustion fluctuation rate; calculate a main injection correction term based on a result of a comparison between a target specified combustion index value or a tolerable specified combustion index value, and the actual specified combustion index value; and calculate a main injection amount by adding the main injection correction term to the basic main injection amount.

Abstract: A method of operating an internal combustion engine is provided. The method includes combusting a mixture of fresh air and fuel within multiple cylinders. The method also includes directing a first portion of exhaust gases into a first-stage turbine and a second-stage turbine of a turbocharger for expanding the exhaust gases, directing a second portion of exhaust gases from the exhaust manifold via an exhaust channel bypassing the first-stage turbine and recirculating a third portion of exhaust gases into an intake manifold after mixing with fresh air. The method includes controlling at least one of: reducing a normal engine speed at each engine power setting while maintaining constant engine power level by increasing a fuel injection per cycle; concurrently increasing a flow rate of the third portion of exhaust gas during recirculation; and advancing a fuel injection timing for reducing emission levels that meets Tier 4 requirements.

Abstract: Cylinder liners, methods of forming the same, and outer surface designs of a cylinder liner having as-cast projections with certain functional shapes are provided. The as-cast projections increase the clamping performance of the cylinder liner and do not result in any air gaps between a cast aluminum block and the cylinder liner.

Abstract: The invention relates to a cylinder head (1) for an internal combustion engine having at least one fire-face-side first cooling chamber (5a) and one second cooling chamber (5b), which adjoins the first cooling chamber (5a) in the axial direction of the cylinder, the first and second cooling chambers (5a, 5b) being separated from each other by means of an intermediate plate (7), a central receptacle (4) being arranged for an injection nozzle or ignition device for each cylinder (Z), and the first and second cooling chambers (5a, 5b) being flow-connected to each other in the region of the central receptacle (4); and having at least two, preferably four gas exchange valve openings (2, 3) per cylinder (Z), the first cooling chamber (5a) having a radial cooling duct (11, 12, 13, 14) in the region of at least one valve bridge (20, 21, 22, 23) between two gas exchange valve openings (2, 3).

Abstract: A galleryless piston for an internal combustion engine is provided. The piston has a monolithic piston body including an upper wall forming an upper combustion surface with first and second portions. The first portion extends annularly along an outer periphery of the upper wall and the second portion includes a combustion bowl. The first portion can also include valve pockets formed therein to reduce weight. The upper wall has an undercrown surface directly opposite the second portion of the upper combustion surface. To enhance cooling, a center portion of the undercrown surface is concave, such that oil is channeled during reciprocation of the piston from one side to the opposite side of the piston.

Abstract: An exemplary forming assembly includes a mold having a cavity to form a component, and an insert having first, second, and third regions. The first region provides a first passageway opening in the component. The second region provides a second passageway opening in the component. The third region provides a passageway in the component. The insert is rotatable from a first position within the passageway to a second position outside the passageway. An exemplary component forming method includes positioning a material around an insert, curing the material to provide a component, and rotating the insert relative to the component from a first position where at least some of the insert is received within a passageway of the component to a second position where the entire insert is outside the passageway.

Abstract: A metal static gasket and method of construction thereof is provided. The gasket includes at least one metal layer. At least one of the metal layers has opposite sides with at least one through opening extending through the opposite sides, with the through opening being configured to register with an opening to be sealed. At least one metal layer of the gasket has least one raised annular seal bead extending adjacent the through opening. A plurality of protrusions extend outwardly from at least one of the opposite sides, wherein the plurality of protrusions are formed from separate pieces of metal from the at least one metal layer and are individually fixed to the at least one metal layer via separate bond joints.