A demodulator processes a continuous-time signal to generate at a plurality of encoded bits. An inner decoder processes a first subset of bits within the plurality of encoded bits to correct selected ones of the first subset of bits to form a corrected first subset of bits and to generate partially corrected data from the plurality of encoded bits based on the corrected first subset of bits. An outer decoder processes the partially decoded data, to correct selected ones of a second subset of the plurality of encoded bits to form a corrected second subset of bits. A bit combiner generates data estimates by combining the corrected first subset of bits and the corrected second subset of bits.

In one embodiment, interference suppression is improved by improving convergence criteria. For some embodiments, convergence is improved by employing non-constant alpha-beta-weighting. For other embodiments, convergence is improved by employing successive interference suppression methods that have guaranteed convergence properties.

A system that incorporates the subject disclosure may include, for example, a process that includes adjusting a filter in electrical communication between an input terminal and a demodulator. The filter is applied to an information bearing signal, e.g., to mitigate interference, received at the input terminal, resulting in a filtered signal. An error signal is received, indicative of errors detected within information obtained by demodulation of a modulated carrier of the filtered signal. A modified filter state is determined in response to the error signal and the filter is adjusted according to the modified filter state, e.g., to improve mitigation of the interference. Other embodiments are disclosed.

Radio frequency (RF) receivers having whitened digital clocks and related methods are disclosed. Disclosed embodiments generate whitened clocks having random variations that are used to operate digital processing blocks so that interference created by the whitened clocks is seen as white noise within the received RF signal spectrum. RF input signals are received by RF front-ends (RFFEs) that output analog signals associated with channels within the RF input signals. These analog signals are converted to digital information and processed by digital receive path circuitry that outputs digital data associated with the channel. The digital receive path circuitry includes a whitened clock generator that generates a whitened clock having random variations and which a digital processing block that operates based upon the whitened clock. Further, the RFFE and the digital receive path circuitry are located within a single integrated circuit.

A very-low intermediate frequency (VLIF) receiver and a method of controlling a VLIF receiver. The method comprises receiving a first signal, the first signal including one or both of an on-channel signal portion and an adjacent channel interferer (ACI) portion; determining that the first signal includes a portion having a strength that is above a threshold; in response to determining that the first signal includes a portion having a strength that is above the threshold, estimating one or more IQ imbalance parameters for at least a portion of the first signal; and compensating for an IQ imbalance in at least the portion of the first signal using the one or more IQ imbalance parameters.

A receiving circuit, use, and method for receiving an encoded and modulated radio signal is provided. The circuit comprise a demodulator and a digital filter connected downstream of the demodulator for moving averaging. The filter has at least two FIFO registers and subtractors. Whereby for subtracting an output value of the FIFO register from an input value of the FIFO register a subtractor is connected to each FIFO register. Wherein the filter has a weighting unit, which is connected downstream of each FIFO register, and wherein the filter has an integrator, which is connected downstream of the subtractors for integration.

A wideband multi-channel receiver comprises an antenna configured to receive a radio frequency band. A band-pass filter is in signal communication with the antenna, and a low-noise amplifier is in signal communication with the band-pass filter. A mixer is in signal communication with the low-noise amplifier and is configured to translate a radio frequency band to an intermediate frequency (IF) band. A tunable local oscillator is in signal communication with the mixer. At least one fixed-frequency notch filter is in signal communication with the mixer, with the notch filter configured to reject at least one interference signal in the IF band while passing remaining signals in the IF band. An analog-to-digital converter is in signal communication with the notch filter and is configured to convert the remaining signals in the IF band to digital signals.

A data transmission apparatus disposed within two network layers operative at different data rates is provided. The data transmission apparatus is coupled to a clock generator which provides a reference clock for a lower network layer and is coupled to a frequency synthesizer with an integer division factor that generates a divided clock for an upper network layer according to the reference clock and the integer division factor. The data transmission apparatus includes a first processing circuit and a second processing circuit. The first processing circuit corresponding to the upper network layer receives and transmits data by using the divided clock as its operation frequency. The second processing circuit corresponding to the lower network layer receives and transmits data from the first processing circuit by using the reference clock as an operation frequency for encoding data. The divided clock is generated from the frequency synthesizer with the integer division factor.

Systems and methods for discrete signal synchronization based on a known bit pattern are described. In one aspect of the present subject matter, a discrete signal synchronization system is configured to synchronize a preprocessed discrete signal with a modified discrete signal. The system comprises a processor and a synchronization module coupled to the processor. The synchronization module comprises an extraction module and comparison module. The extraction module determines a bit pattern from the modified discrete signal using Discrete Wavelet Transformation (DWT) and Singular Value Decomposition (SVD). The comparison module compares the determined bit pattern with a known bit pattern of the preprocessed discrete signal and records a time point at which the determined bit pattern matches with the known bit pattern of the preprocessed discrete signal as a synchronization point.

Described herein are systems and methods for accurately estimating and removing a carrier frequency offset. One exemplary embodiment relates to a system comprising a frequency offset detection circuit detecting a carrier frequency offset in an optical signal, and a frequency testing circuit calculating an estimated frequency offset value of the carrier frequency offset, wherein the frequency testing circuit removes a carrier phase based on the estimated frequency offset value and recovers the optical signal. Another exemplary embodiment relates to a method comprising detecting a carrier frequency offset in an optical signal, calculating an estimated frequency offset value of the carrier frequency offset, removing a carrier phase based on the estimated frequency offset value, and recovering the optical signal.

In a wireless network, plural downlink signals from plural base stations are transmitted to a terminal. The plural downlink signals all carry the same information to the terminal. The terminal provides feedback on the downlink channels. The feedback provides information on the taps of the channels. The amount of information fed back is constrained. Based on the feedback, transmission parameters of the downlink signals are adjusted. The process of transmitting, providing feedback, and adjusting the parameters continue so that the energy of the downlink signal is enhanced at the terminal location and suppressed elsewhere. Beam forming can be used to further suppress the energy signature at locations other than the terminal location.

A decoder receives a bitstream containing quantized coefficients representative of blocks of video representative of a plurality of pixels and decodes the bitstream using context adaptive binary arithmetic coding that includes at least two decoding modes, the first mode decoding the bitstream based upon a probability estimate which is based upon at least one of spatially and temporally adjacent syntax element values to a current syntax element being decoded, the second mode decoding the bitstream not based upon a probability estimate based upon other syntax elements to the current syntax element being decoded. The coding decodes the current syntax element using the first mode if the current syntax element is intra-coded and selecting between sets probable modes with different probabilities. The coding decodes the current syntax element using the second mode if the current syntax element is intra-coded and if selecting among one of the second set of probable modes.

A method is provided for improving synchronization and information transmission in a communication system, including: generating a signal with a centrally symmetric part s(k) exploitable for synchronization; and sending the signal over a communication channel. The signal is based on a uniquely identifiable sequence c(l) from a set of sequences exploitable for information transmission. The centrally symmetric part s(k) is centrally symmetric in the shape of absolute value thereof. The centrally symmetric part s(k) is of arbitrary length N.

An image processing apparatus includes a system managing unit configured to manage an apparatus status of apparatus hardware; an acquiring unit configured to acquire application status information of an application from the application and apparatus status information from the system managing unit; an input unit configured to accept a display request for displaying a status monitor screen indicating an overall system status; a screen generating unit configured to receive the display request and generate the status monitor screen based on the application status information and the apparatus status information acquired by the acquiring unit, the status monitor screen including an application status display and an apparatus status display; and a display unit configured to display the status monitor screen generated by the screen generating unit.

A display apparatus includes a first substrate, a second substrate facing the first substrate, and a plurality of pixels including a first pixel. The first substrate includes first openings through which a light is transmitted. The pixels are disposed on at least one of the first substrate and the second substrate. The first pixel includes a first flexible electrode, a second flexible electrode, and a shutter including second openings and disposed between the first and second flexible electrodes. The first flexible electrode receives a first voltage. The second flexible electrode receives a second voltage different from the first voltage. The shutter receives a third voltage. The shutter moves to the first flexible electrode or the second flexible electrode according to a level of the third voltage, thereby controlling the position of the second openings relative to the first openings to control the transmission of the light.

An image-based georeferencing system comprises an image receiver, an image identification processor, a reference feature determiner, and a feature locator. The image receiver is configured for receiving a first image for use in georeferencing. The image comprises digital image information. The system includes a communicative coupling to a georeferenced images database of images. The image identification processor is configured for identifying a second image from the georeferenced images database that correlates to the first image. The system includes a communicative coupling to a geographic location information system. The reference feature determiner is configured for determining a reference feature common to both the second image and the first image. The feature locator is configured for accessing the geographic information system to identify and obtain geographic location information related to the common reference feature.

Deficiencies in existing attempts at educational software solutions are addressed by providing systems, methods, and devices that both replicate and facilitate the necessary elements of successful classroom-based learning, while taking advantage of the platform-specific benefits of handheld computing devices. Various applications address the issue of the limited screen size of mobile devices by using the motion sensors of the devices both to move from one part of a program to another, thus eliminating the need for on-screen navigation buttons and allowing the entire screen to be used for content, and also to reinforce learning through the use of mnemonics. In these applications, the user rotates the device after completing each step, in sequence, of a process-based series of problem solving techniques. Group learning dynamics are also reproduced through a study group feature.

View definitions are created for deterministic performance analysis in real-time computing systems, and can then be used to present views for analyzing outliers that occur during run-time execution. Trace data created by a real-time application is compared to a set of view definitions to determine whether the trace data matches the view definition. If so, then related records from the trace are gathered according to specifications in the matched view definition, and calculations (such as elapsed time) can then be performed using the related records. A view definition may be created by prompting a user for selection of parameters to be programmatically inserted into a markup language document. A capability may be provided whereby a user can receive additional information (which is extracted from the trace data, according to specifications in the matched view definition) upon a user gesture such as hovering a selection means over a displayed view.

A method and apparatus for shader data repair utilizing a Redundant Shader Switch (RSS). The RSS consists of an input and output section whereby when a defective shader pipe is detected, the RSS multiplexes shader pipe data destined to the defective shader pipe to a redundant shader pipe array for processing. Once processed, the shader pipe data is multiplexed back to the RSS where the processed shader pipe data is directed to the corresponding output column of the RSS. The RSS contains delay pipes used to re-align and synchronize the repaired shader pipe data with output export data.

Generating a digital-media-enhanced electronic record of a locate and/or marking operation performed by a locate technician. The locate and/or marking operation comprises locating and/or identifying, using at least one physical locate mark, a presence or an absence of at least one underground facility within a dig area, wherein at least a portion of the dig area may be excavated or disturbed during excavation activities. A location of the at least one underground facility and/or the at least one physical locate mark is electronically rendered on a display device so as to generate an electronic visual representation of the locate and/or marking operation. At least one digital media file representation of a corresponding digital media file relating to at least one aspect of the locate and/or marking operation or an environment of the dig area is also electronically rendered on the display device, so as to generate a digital-media-annotated representation of the locate and/or marking operation. Information relating to the digital-media-annotated representation of the locate and/or marking operation is electronically transmitted and/or stored so as to generate the digital-media-enhanced electronic record of the locate and/or marking operation.

A transceiver includes an antenna, an impedance adjustment device, an RF (Radio Frequency) front-end circuit, a storage device, and a processor. The antenna receives an RF signal. The impedance adjustment device is coupled to the antenna, and includes a plurality of branch circuit with different impedance values and a switch module. The processor is coupled to the RF front-end circuit and controls the switch modules. In a comparison mode, the switch module selects to connect to the branch circuits individually, and the processor detects each RSSI (Received Signal Strength Indications) value corresponding to the branch circuit and records all of the RSSI values to the storage device respectively. In the comparison mode, the processor further compares the RSSI values to for highest one. Finally, the switch module selects the branch circuit corresponding to the highest RSSI value as a transmission branch.

A circuit card is provided that includes ground traces that extend from a resistor to a commoning bar, where a resultant electrical length between the resistor and the commoning bar and is configured to reduce energy carried on the ground terminals that could otherwise result in cross-talk. In an embodiment, the ground trace may be configured in a meandering manner. In another embodiment, the ground trace may be split and joined by an inductor.

A transmission line is provided in which a first portion of the transmission line is configured to be connected to a source, and a second portion of the transmission line is configured to be connected to a load. A capacitive element is coupled to the transmission line and is configured to compensate for an impedance difference between the load and at least one of the source or the transmission line, at a frequency within a frequency bandwidth of the load. A difference between an internal capacitance of the first portion of the transmission line and the second portion of the transmission line substantially matches the capacitance of the capacitive element.

The present invention is directed to an impedance transformation device for use in a system having a characteristic system impedance, the device being characterized by a predetermined bandwidth having a center frequency. The device housing size is one-eighth wavelength of the center frequency. A first coupler is characterized by an even mode impedance and an odd mode impedance. The bandwidth is a function of the even mode impedance and the odd mode impedance substantially corresponds to the component port impedance. At least one second coupler is disposed in parallel with the first coupler and is characterized by the even mode impedance and the odd mode impedance.

There is provided a high frequency switch having a reduced circuit scale while maintaining satisfactory harmonic characteristics in a transfer path of a high frequency signal. The high frequency switch includes: at least one transmission port; at least one reception port; a common port; transmission side series switches each including a body contact type FET; transmission side shunt switches each including a body contact type FET; reception side series switches each including a body contact type FET; and reception side shunt switches each including at least one floating body type FET.

A three dimensional (3D) branchline coupler using through silicon vias (TSV), methods of manufacturing the same and design structures are disclosed. The method includes forming a first waveguide structure in a first dielectric material. The method further includes forming a second waveguide structure in a second dielectric material. The method further includes forming through silicon vias through a substrate formed between the first dielectric material and the second dielectric material, which connects the first waveguide structure to the second waveguide structure.

A SAW filter circuit having improved ESD resistance is specified, in which a series interconnection composed of SAW resonators is interconnected between a first signal port and a dual-mode SAW filter port. The static capacitance of the series interconnection is at most four times the static capacitance of the dual-mode SAW filter transducers interconnected therewith.

A frequency tunable filter is disclosed. The frequency tunable filter includes a filter unit that can tune a frequency band of a frequency signal being filtered, a communication module that receives a control signal for controlling the tuning of the frequency band, and a control unit that controls the tuning of the frequency band based on the control signals. The disclosed filter can control the tuning of the filter's frequency band wirelessly.

An attenuation reduction control structure for high-frequency signal transmission lines of a flexible circuit board includes an impedance control layer formed on a surface of a substrate. The impedance control layer includes an attenuation reduction pattern that is arranged in an extension direction of the high-frequency signal transmission lines of the substrate and corresponds to bottom angle structures of the high-frequency signal transmission lines in order to improve attenuation of a high-frequency signal transmitted through the high-frequency signal transmission lines. An opposite surface of the substrate includes a conductive shielding layer formed thereon. The conductive shielding layer is formed with an attenuation reduction pattern corresponding to top angle structures of the high-frequency signal transmission lines.

An electronic component includes: a first circuit connected to a first common terminal for inputting/outputting a first signal set, a second common terminal for inputting/outputting a second signal set having a frequency higher than the first signal set, and a third common terminal for being connected to an antenna; and a second circuit connected in parallel to the first circuit between the first and second common terminals, wherein the first circuit includes a first filter transmitting the first signal set and reflecting the second signal set, and a second filter transmitting the second signal set and reflecting the first signal set, the third common terminal is located between the first and second filters, and the second circuit reflects a first transmission signal and a second transmission signal, transmits parts of the first and second transmission signals, and inverts phases of the parts of the first and second transmission signals.

To provide a capacitive device capable of accurately securing a capacitance value, a variable capacitive device capable of sufficiently securing a capacity variability rate, and a resonance circuit that uses the capacitive devices. A capacitive device includes a capacitive device body constituted of a dielectric layer and at least a pair of capacitive device electrodes that sandwich the dielectric layer and cause a desired electric field in the dielectric layer; and stress adjustment portions to adjust a stress caused in the dielectric layer of the capacitive device body.

Implementations for exciting two or more modes via modal decomposition of a pulse by a wave launcher are generally disclosed.

An unbalanced-balanced conversion circuit element includes an inductor connected in series between an unbalanced terminal and a first balanced terminal. The first balanced terminal side of the inductor is grounded via a capacitor. A capacitor is connected in series between the unbalanced terminal and a second balanced terminal. An inductor is connected between the first balanced terminal side of the inductor and the second balanced terminal side of the capacitor. In a laminate defining the unbalanced-balanced conversion circuit element, the capacitor is spaced far from a mounting surface of the laminate in comparison with other circuit elements.

Crimp-imbalanced fabric systems are accomplished by varying the levels of yarn crimp within a single fabric layer and across layers of a multi-layer fabric system. The method includes developing a crimp in the yarn (utilized for producing a fabric layer) by optionally pulling the yarn through a solution that substantially coats the yarn. The optionally removable coating has a thickness that ensures a proper amount of crimp in the yarn. The tension in the yarn is controlled; the yarn is weaved; and a crimp is applied in the yarn. Once the crimp is applied, families of the crimped yarn are utilized as a single layer or multiple layer system to increase performance attributes including enhanced energy absorption.

A direct feeding apparatus for impedance matching of a wireless power transmission device includes a helical type resonator, and a feeding unit configured to directly feed power to a region having a relatively small current value as compared to a center of a conductive line of the resonator.

A battery system is disclosed. The battery system includes a plurality of battery cells, and a battery cell balancing unit, configured to adjust voltages across each of the battery cells to reduce variation among the voltages across the battery cells. The battery cell balancing unit includes a controller configured to receive a DC reference current and to generate an AC current based on the DC reference current, a transformer, a rectifier circuit including a rectifier connected to the output coil, and a switching unit including a plurality of switches, each configured to selectively connect the rectifier to one of the battery cells.

A battery pack and an electronic device are disclosed. The battery pack includes a battery for storing electric energy, and a non-contacting discharging unit for receiving the stored electric energy from the battery and for transferring the stored electric energy to a power receiving unit in a non-electrically contacting manner. The electronic device includes a main body and the battery pack. The main body includes a power receiving unit. The battery pack is for mounting to and supplying power to the main body.

A rotary electric machine for a vehicle that is capable of starting synchronous rectification through switching elements after having ensured absence of a short circuit fault. The rotary electric machine includes a multi-phase armature winding, a switching element set that includes a plurality of pairs of upper-arm and lower-arm switching elements to form a bridge rectification circuit together with the armature winding, an on/off-timing setter that sets on/off-timing of each switching element, a switching element driver that drives each switching element at the on/off-timing set by the on/off-timing setter; and a synchronous control start determiner that determines timing when an energization period for the upper-arm switching element and an energization period for the lower-arm switching element occur alternately as start timing of the synchronous rectification.

The present invention provides a method and a device for primary frequency regulation based on bang-bang control, the method comprises: obtaining in real-time a power grid frequency of a steam turbine generator set; performing a subtraction operation on a rated power grid frequency and said power grid frequency to generate a power grid frequency difference; performing a dead zone process on the power grid frequency difference according to a dead zone fixed value to generate a frequency difference; performing a frequency difference compensation operation on the frequency difference to generate a frequency difference compensation instruction; and combining an original primary frequency regulation output instruction with the frequency difference compensation instruction and outputting the result to a steam turbine speed regulation system when a selecting switch is 1.

A generator system includes a generator having a stationary portion and a rotating portion. The generator includes a permanent magnet based exciter with permanent magnets disposed on the stationary portion. A first channel includes a first main field winding and a first main field power converter disposed on a rotating portion. The first main field power converter selectively delivers voltage from the exciter winding to the first main field winding. A second channel includes a second main field winding and a second main field power converter disposed on the rotating portion. The second main field power converter selectively delivers voltage from the exciter winding to the second main field winding. A generator control unit is connected to the first channel and the second channel. The generator control unit monitors an output voltage at each of the first channel and the second channel and generates the first and second control signals based on the output voltage.

An electrical machine includes a stator having a main armature winding, an exciter field winding, and a transformer primary winding. A rotor is operatively connected to rotate relative to the stator, wherein the rotor includes an exciter armature winding operatively connected to the exciter armature winding for field excitation therebetween, a main field winding operatively connected to the main armature winding for field excitation therebetween, and a transformer secondary winding operatively connected to the transformer primary winding to form a rotating transformer. A generator control unit is operatively connected to the main armature winding, exciter field winding, and transformer primary winding to control the main armature and exciter field windings based on excitation in the primary winding received from the transformer secondary winding.

A method of controlling a generator (110) of an electric drive (104) associated with an engine (102) is provided. The method may determine an operational state of the electric drive (104) based on a speed of the engine (102), and selectively engage one of a map-lookup control scheme (150) and a fixed-theta off control scheme (152) for operating the generator (110) based on the operational state of the electric drive (104).

Systems and methods for reducing current imbalance between parallel bridge circuits used in a power converter of a doubly fed induction generator (DFIG) system are provided. A control system can monitor the bridge current of each of the bridge circuits coupled in parallel and generate a feedback signal indicative of the difference in bridge current between the parallel bridge circuits. Command signals for controlling the bridge circuits can then be developed based on the feedback signal to reduce current imbalance between the bridge circuits. For instance, the pulse width modulation of switching devices (e.g. IGBTs) used in the bridge circuits can be modified to reduce current imbalance between the parallel bridge circuits.

An appliance holder system for electrical handheld appliances of the type having a flexible electrical power cord attached thereto is provided. The appliance holder system includes an appliance holder assembly having at least one receptacle for receiving and storing at least one electrical handheld appliance having a flexible electrical power cord attached thereto. A power cord storage assembly of the system has a pair of spaced apart cord wrapping elements about which the flexible electrical power cord may be wrapped for storage. At least one of the cord wrapping elements is movable between a storage and release position. The cord wrapping elements are configured to retain the wrapped power cord upon the power cord storage assembly when the at least one of the cord wrapping elements is in the storage position and wherein the wrapped power cord may be removed from the power cord storage assembly without unwrapping the wrapped power cord when the at least one of the cord wrapping elements is moved to the release position.

A power cord management system for managing flexible electrical power cords associated with hair or bathroom handheld appliances includes a power cord storage body. A pair of spaced apart cord wrapping elements are coupled to the power storage body about which the flexible electrical power cord may be wrapped for storage. At least one of the cord wrapping elements is movable between a storage and release position. The cord wrapping elements are configured to retain the wrapped power cord upon the power cord storage body when the at least one of the cord wrapping elements is in the storage position and wherein the wrapped power cord may be removed from the power cord storage body without unwrapping the wrapped power cord when the at least one of the cord wrapping elements is moved to the release position. A power cord coupling mechanism is coupled to the power cord storage body for facilitating releasable retaining of a free end or other portion of the flexible electrical power cord to the power cord storage body.

A method of controlling combustion of a gas appliance includes the following steps: a) Read a first burning data in a database; b) Burn gas according to the first burning data; c) Obtain a burning efficiency of the gas appliance; and d) Compare the burning efficiency with a predetermined value, and repeat the step b to the step d when the burning efficiency is higher than the value, or read a second burning data in the database and burn gas according to the second burning data when the burning efficiency is lower than the value. The present invention provides plural stages of burning according to the main component of the gas to be burned to increase the total burning efficiency.

A steam generator includes a substantially horizontal gas conduit (1) to guide a heating gas flow (2) and an evaporator unit positioned at least partially in the horizontal gas conduit for transferring heat from the heating gas to a flow medium which flows through the evaporator unit. The heat transfer section of the evaporator unit of the steam generator is bottom fed, which means that the inlet conduit is arranged at a lower region of the heat transfer section. The outlet conduit is arranged at an upper region. The inlet conduit allows an once through operation of the evaporator section which is necessary to enable operation under supercritical circumstances. The evaporator unit includes at least two evaporator stages (3, 4) which are arranged in a cascade. Each evaporator stage includes a heat transfer section (12, 21) and a separator (14, 23). The presence of the separators (14, 23) subdivides the evaporator unit into evaporator stages (3, 4).

A condensing fuel-fired appliance has a condensate trap that includes a trap body; a float; a flue gas inlet port for the introduction of flue gas into the interior region of the trap body; a condensate outlet port for the discharge of condensate from the interior region; and a flue gas outlet port for the discharge of flue gas from the interior region of the trap body. The float is configured to move in response to condensate collected in the interior region of the trap body to a position to substantially block the discharge of flue gas from the interior region through the flue gas outlet port. The float is also configured to move to a position to substantially block the discharge of flue gas from the interior region through the condensate outlet port when there is little or no condensate in the interior region of the trap body.

An apparatus includes an inner rim, a base wall, a side wall and an outer rim. The inner rim has a first opening formed therein. The base wall extends outward from an inner edge of the inner rim and is integral with the inner rim. The side wall extends outward from an outer edge of the inner rim and is integral with the inner rim. The outer rim has a second opening formed therein and an inner edge integral with the side wall. The inner rim, base wall, side wall and outer rim are formed to prevent liquid seepage to one or more surrounding components of an appliance in which the apparatus is installed.

The efficiencies of illustrative embodiments of vertical center flue type fuel-fired base water heaters are improved by installing in the water heaters variously configured tubular condensing type secondary heat exchangers of smaller diameters than the associated center flues. The efficiency increases are achieved with components and manufacturing processes similar to those utilized in the base water heaters and secondary heat exchanger materials similar to those in the tank portions of the base water heaters.