Multifrequency Nature Research Articles

MF-Net: Multi-frequency intrusion detection network for Internet traffic data

The rapid growth of Internet technology renders intrusion detection an important research topic in the field of pattern recognition. Considering that traffic data relate to not only temporal information, but also attack frequency, this paper presents a novel deep learning framework termed the multi-frequency intrusion detection network (MF-Net). MF-Net regards the pattern of Internet traffic as a superposition of sequential data with various frequencies, and is able to recognize the multi-frequency nature of network traffic data. The core of MF-Net is the multi-frequency LSTM (MF-LSTM) and multi-frequency transformer (MF-Transformer) module, both of which consist of high-frequency and low-frequency layers. In comparison with other state-of-the-art approaches on 4 public datasets, namely UNSW-NB15, KDD Cup 99, NSL-KDD and CICIDS 2017, as well as an IPv6 traffic dataset we created, MF-Net has shown better result in both binary and multi-class classification, which demonstrates the superiority of MF-Net over other compared approaches on network traffic intrusion detection.

Experimental study of a double-circuit optoelectronic generator of radio-frequency signals

An urgent issue is the development of radio frequency generators operating in the microwave range, with high frequency stability, wide tuning band, as well as small size and weight. Microwave signal generators are used as part of radio electronic devices and devices for telecommunication, radio navigation and metrological purposes; therefore, improving their main characteristics is an important goal for the further development of radio electronic devices. A technological feature of optoelectronic generators is the combined use of solid-state components of modern HF and UHF optoelectronics, fiber optics and traditional components of UHF/EHF technology. According to the principle of operation and construction scheme, the optoelectronic generator is similar to the classic radio-frequency self-oscillator with a delay line in the feedback circuit. A feature of its work is the multifrequency nature of the generated oscillations, for which the conditions for amplitude balance and phase balance are satisfied. In the case of an optoelectronic generator, a feedback ring with a resonant system and a delay element is made using a single-mode fiber of a certain length. The signal delay time in the feedback loop is a significant parameter of the optoelectronic generator, which affects the noise and spectral characteristics of the generator. With an increase in the length of the fiber-optic path, the delay time in the feedback loop increases, thereby reducing the level of frequency noise. However, with an increase in the length of the fiber-optic path, the distance between adjacent modes of the optoelectronic oscillator also decreases, increasing the requirements for the bandwidth of the band-pass filter. The solution to this problem was the use of a multi-circuit optoelectronic generator. The paper considers a model created by the authors for a two-circuit optoelectronic generator with fiber-optic paths 1000 m and 30 m long. The available element base did not allow to reduce the generator's weight and dimensions. On this model, the characteristics of the circuit elements have been experimentally studied. The spectral characteristics of the generator have been estimated theoretically, which are in good agreement with the results of practical research. Phase noise is an important parameter in generator evaluation. Oscillators used as reference and measuring oscillators must certainly have a high frequency stability of the generated signal. Oscillations in autogenerators arise due to the effect of intrinsic noise in the circuit elements, which is one of the reasons for the occurrence of noise in the spectrum of the generator output signal. Intrinsic noise includes thermal, shot and flicker noises in semiconductor elements of generators. The article calculates the power spectral density of the phase noise of a single-loop oscillator and a dual-loop oscillator, which confirmed the assumption about a compromise between the noise level and the requirement for the filter bandwidth in a single-loop optoelectronic oscillator. An important advantage of optoelectronic generators, in comparison with generators built according to classical circuitry, is the absence of a compromise between the frequency tuning band of the device generation and the level of frequency noise.

Physical and chemical characterization of shock-induced cavitation

A strong impact on a water surface induces a shock wave propagation with a significant pressure variation leading to cavitation bubble formation. A new shock induced cavitation reactor described in this work was characterized by physical and chemical techniques. Water hammer model verification with Joukowsky approach allowed to determine the wave speed propagation and gas fraction in water submitted to shock. These values were used for frequency analysis and compared with direct bubble visualization in order to estimate the influence of the experimental parameters on the shock-induced cavitation. Thereby, the shock wave contains a broad spectrum as decomposed into frequencies. This multi-frequency nature induces heterogeneous bubbles with calculated radii of 0.01 to 3.5 mm and observed radii of 0.01 to 2.8 mm depending on experimental conditions (initial pressure, impact height, gas atmosphere). For the first time, the formation of hydroxyl radicals was proven under impact-induced cavitation. The concentration of radicals increases with increasing number of successive impacts, reaching ca. 1.3 µmol.L−1 after 500 impacts in the presence of 20% O2-Ar as saturating gas. Radical generation seems to be relatively independent of the impact height but strongly depend on the type of gas saturating water, being substantially lower in the presence of air. Moreover, radical generation increases when decreasing the initial pressure and depends on the frequency at which water is impacted by the piston. Nevertheless, yield of OH radicals during shock-induced cavitation remains much lower than that produced by power ultrasound.

Experimental study on band merging of non-linear multi-band piezoelectric energy harvester into single broadband using magnetic coupling

The operational bandwidth of Vibration Energy Harvesters (VEH) is area of concern due to stochastic, time-varying, random and multi-frequency nature of available environmental vibrating sources. Most of the VEH have narrow bandwidth providing usable power at specific frequencies. Efforts have been made to increase the frequency range by introducing non-linear structures and techniques. In this paper, multi-band output of the non-linear Piezoelectric Energy Harvester (PEH) is transformed into single wider band output using additional non-linear phenomenon. Dual region operation of PEH results into two separate band output. First region is the outcome of beam resonance and Centre of Gravity (CoG) shift whereas second region is due to the non-linear behaviour of cylinders. In this work, these separate bands are merged to form a single wider band. For merging these two bands and enhancing the bandwidth of PEH, additional phenomenon is introduced using two permanent magnets. A varying magnetic field by changing the distance between magnets changes stiffness of the cantilever beam and that leads to a change in the resonant frequency of band-I. Thus, the overall process shifts band-I towards band-II. In this work, the two separate bands are merged to have one wider band providing 53.22% more frequency coverage than our previous work with a bandwidth of 47.5 Hz. This band includes vibrational frequency range of 25.65–73.15 Hz at 1.4 g acceleration. Cylinder material and its effect with magnetic interaction is also studied. The magnetic force between two permanent magnets is measured experimentally. Effect of magnetic force on centre resonant frequency of beam is compared with experimental and simulated results. Effect of magnetic force on bandwidth of the device is studied.

Degenerate band edge laser

We propose a class of lasers based on a fourth-order exceptional point of degeneracy (EPD) referred to as the degenerate band edge (DBE). EPDs have been found in parity-time-symmetric photonic structures that require loss and/or gain; here we show that the DBE is a different kind of EPD since it occurs in periodic structures that are lossless and gainless. Because of this property, a small level of gain is sufficient to induce single-frequency lasing based on a synchronous operation of four degenerate Floquet-Bloch eigenwaves. This lasing scheme constitutes a light-matter interaction mechanism that leads also to a unique scaling law of the laser threshold with the inverse of the fifth power of the laser-cavity length. The DBE laser has the lowest lasing threshold in comparison to a regular band edge laser and to a conventional laser in cavities with the same loaded quality $(Q)$ factor and length. In particular, even without mirror reflectors the DBE laser exhibits a lasing threshold which is an order of magnitude lower than that of a uniform cavity laser of the same length and with very high mirror reflectivity. Importantly, this novel DBE lasing regime enforces mode selectivity and coherent single-frequency operation even for pumping rates well beyond the lasing threshold, in contrast to the multifrequency nature of conventional uniform cavity lasers.

Dynamic models of cultivator spring tine performance

The article presents results of spring-tine cultivator blade movement modeling. The basic equation of terraelasticity is taken as the initial one. The new model takes into account the spring tine configuration and the vibration mode. It is noted that the model becomes multifrequent. The field reserach confirmed multifrequency and mixed nature of the spring tine vibration spectrum. It is found that the frequency spectrum with technologically relevant vibration accelerations can be more than 1000 Hz. The authors make a conclusion that it is necessary to use high frequencies to improve the quality of spring-tine cultivator blade performance.

Performance Evaluation of Time-Frequency Distributions for ECG Signal Analysis

The non-stationary and multi-frequency nature of biomedical signal activities makes the use of time-frequency distributions (TFDs) for analysis inevitable. Time-frequency analysis provides simultaneous interpretations in both time and frequency domain enabling comprehensive explanation, presentation and interpretation of electrocardiogram (ECG) signals. The diversity of TFDs and specific properties for each type show the need to determine the best TFD for ECG analysis. In this study, a performance evaluation of five TFDs in term of ECG abnormality detection is presented. The detection criteria based on extracted features from most important ECG signal components (QRS) to detect normal and abnormal cases. This is achieved by estimating its energy concentration magnitude using the TFDs. The TFDs analyse ECG signals in one-minute interval instead of conventional time domain approach that analyses based on beat or frame containing several beats. The MIT-BIH normal sinus rhythm ECG database total records of 18 long-term ECG sampled at 128Hz have been analysed. The tested TFDs include Dual-Tree Wavelet Transform, Spectrogram, Pseudo Wigner-Ville, Choi-Williams, and Born-Jordan. Each record is divided into one-minute slots, which is not considered previously, and analysed. The sample periods (slots) are randomly selected ten minutes interval for each record. This result with 99.44% detection accuracy for 15,735 ECG beats shows that Choi-Williams distribution is most reliable to be used for heart problem detection especially in automated systems that provide continuous monitoring for long time duration.

Persistent energy–time entanglement covering multiple resonances of an on-chip biphoton frequency comb

We investigate the time-frequency signatures of an on-chip biphoton frequency comb (BFC) generated from a silicon nitride microring resonator. Using a Franson interferometer, we examine the multifrequency nature of the photon pair source in a time entanglement measurement scheme; having multiple frequency modes from the BFC results in a modulation of the interference pattern. This measurement together with a Schmidt mode decomposition shows that the generated continuous variable energy-time entangled state spans multiple pair-wise modes. Additionally, we demonstrate nonlocal dispersion cancellation, a foundational concept in time-energy entanglement, suggesting the potential of the chip-scale BFC for large-alphabet quantum key distribution.

Counter-evidence against multiple frequency nature of 0.75 mHz oscillation in V4743 Sgr

All X-ray light curves of nova V4743 Sgr (2002), taken during and after outburst, contain a 0.75 mHz periodic signal that can most plausibly be interpreted as being excited by the rotation of the white dwarf in an intermediate polar system. This interpretation faces the challenge of an apparent multifrequency nature of this signal in the light curves taken days 180 and 196 after outburst. We show that the multisine fit method, based on a superposition of two sine functions, yields two inherently indistinguishable solutions, i.e. the presence of two close frequencies, or a single signal with constant frequency but variable modulation amplitude. Using a power spectrum time map, we show that on day 180, a reduction of the modulation amplitude of the signal coincides with a substantial overall flux decline, while on day 196, the signal is present only during the first half of the observation. Supported by simulations, we show that such variations in amplitude can lead to false beating, which manifests itself as a multiple signal if computing a periodogram over the full light curve. Therefore, the previously proposed double-frequency nature of both light curves was probably an artefact, while we consider a single signal with frequency equal to the white dwarf rotation as more plausible.

Shock-induced cavitation as a way of accelerating phenol oxidation in aqueous media

Shock-induced cavitation phenomena, resulting from the propagation of the trail of shock-waves generated upon the impact of a solid piston on a liquid surface, was used as an innovative way of intensifying the oxidation of phenol in aqueous media. The amount of energy communicated by the impact was found to be proportional to the impact height, and was directly related to the maximal pressure attained, i.e. in the order of several tens of bars. This peak was followed by a rarefaction period that results in the origination of several cavitation phenomena, which continued upon piston rebound and further shock-wave generation and propagation. The multi-frequency nature of shock-induced cavitation, capable of exciting a wide range of frequencies between 1kHz and 100kHz, was confirmed by means of wavelet analysis. Under shock-induced cavitation conditions, phenol degradation was found to be possible even in the absence of any oxidizing agent. High extents of mineralization, i.e. 45.3 and 56.2% TOC elimination, 50mg/L solution, neutral pH, were obtained in the presence of H2O2 (aprox. 10% vol.), pointing to an acceleration of the oxidation reaction based in a faster and more efficient creation of radical species.

The LOFAR Multifrequency Snapshot Sky Survey (MSSS)

We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky LOFAR imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR's multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the "MSSS Verification Field" (MVF), a region of 100 square degrees centered at J2000 (RA,Dec)=(15h,69deg). The MSSS results from the MVF are compared with previous radio survey catalogs. We assess the flux and astrometric uncertainties in the catalog, as well as the completeness and reliability considering our source finding strategy. We determine the 90% completeness levels within the MVF to be 100 mJy at 135 MHz with 108" resolution, and 550 mJy at 50 MHz with 166" resolution. Images and catalogs for the full survey, expected to contain 150,000-200,000 sources, will be released to a public web server. We outline the plans for the ongoing production of the final survey products, and the ultimate public release of images and source catalogs.

Electromagnetic fields from mobile phone base station – variability analysis

The article describes the character of electromagnetic field (EMF) in mobile phone base station (BS) surroundings and its variability in time with an emphasis on the measurement difficulties related to its pulse and multi-frequency nature. Work also presents long-term monitoring measurements performed recently in different locations in Poland – small city with dispersed building development and in major polish city – dense urban area. Authors tried to determine the trends in changing of EMF spectrum analyzing daily changes of measured EMF levels in those locations. Research was performed using selective electromagnetic meters and also EMF meter with spectrum analysis.

Ships with ventilated cavitation in seaways and active flow control

Bottom ventilated cavitation has been proven as a very effective drag reduction technology for river ships and planning boats. The ability of this technology to withstand the sea wave impact usual for seagoing ships depends on the ship bottom shape and could be enhanced by some active flow control devices. Therefore, there is the need in numerical tools to estimate the effects of bottom changes and to design such devices. The fundamentals of active flow control for the ship bottom ventilated cavitation are considered here on the basis of a special model of cavitating flows. This model takes into account the air compressibility in the cavity, as well as the multi-frequency nature of the incoming flow in wavy seas and of the cavity response on perturbations by incoming flow. The numerical method corresponding to this model was developed and widely manifested with an example of a ship model tested in a towing tank at Froude numbers between 0.4 and 0.7.The impact of waves in head seas and following seas on cavities has been studied in the range of wavelengths from 0.45 to 1.2 of the model (or ship) length. An oscillating cavitator-spoiler was considered as the flow controlling devices in this study. The oscillation magnitude and the phase shift between cavitator oscillation and the incoming waves have been varied to determine the best flow control parameters. The main results of the provided computational analysis include oscillations of cavity surface, of the pressure in cavity and of the moment of hydrodynamic load on the cavitator. The major part of computations has been carried out for the flap oscillating at the frequency coinciding with the wave frequency, but the effect of a frequency shift is also analyzed.

Distributed lock-in drives broadband vortex-induced vibrations of a long flexible cylinder in shear flow

AbstractA slender flexible body immersed in sheared cross-flow may exhibit vortex-induced vibrations (VIVs) involving a wide range of excited frequencies and structural wavenumbers. The mechanisms of broadband VIVs of a cylindrical tensioned beam of length-to-diameter aspect ratio 200 placed in shear flow, with an exponentially varying profile along the span, are investigated by means of direct numerical simulation. The Reynolds number is equal to 330 based on the maximum velocity, for comparison with previous work on narrowband vibrations in linear shear flow. The flow is found to excite the structure at a number of different locations under a condition of wake–body synchronization, or lock-in. Broadband responses are associated with a distributed occurrence of the lock-in condition along the span, as opposed to the localized lock-in regions limited to the high inflow velocity zone, reported for narrowband vibrations in sheared current. Despite the instantaneously multi-frequency nature of broadband responses, the lock-in phenomenon remains a locally mono-frequency event, since the vortex formation is generally synchronized with a single vibration frequency at a given location. The spanwise distribution of the excitation zones induces travelling structural waves moving in both directions; this contrasts with the narrowband case where the direction of propagation toward decreasing inflow velocity is preferred. A generalization of the mechanism of phase-locking between the in-line and cross-flow responses is proposed for broadband VIVs under the lock-in condition. A spanwise drift of the in-line/cross-flow phase difference is identified for the high-wavenumber vibration components; this drift is related to the strong travelling wave character of the corresponding structural waves.

Stacked compact ring‐coupled rectangular microstrip antenna for multiband applications

AbstractThe investigations on stacked compact ring coupled rectangular microstrip antenna which are able to generate multiple resonant frequencies in the wireless communication bands, are reported. In these antennas by embedding various shapes of slots the size reduction is obtained. Also, the stacking on the ring‐coupled patch has been made to achieve wide bandwidth. The multifrequency nature of the stacked slotted patch is studied using IE3D software. The proposed antennas exhibits broadside radiation pattern. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1387–1391, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26842

Mono- and multi-frequency vortex-induced vibrations of a long tensioned beam in shear flow

The mono-frequency as well as multi-frequency vortex-induced vibrations of a tensioned beam of aspect ratio 200, immersed in a linear shear flow at Reynolds number 330 and free to move in both the in-line and cross-flow directions, are studied by means of direct numerical simulation. The structural responses are composed of mixed standing–traveling wave patterns. We observe a switch between mono- and multi-frequency vibrations when the mass ratio changes from a value of 3 to 6, while keeping constant the non-dimensional cable and beam phase velocities. This switch is attributed to the accompanying change in the time-averaged in-line curvature of the beam, which alters the oncoming flow velocity component normal to the structure configuration. It is shown, in general, that the mono- or multi-frequency nature of the response is controlled by the form of the profile of the normal component of the oncoming flow.Mono- and multi-frequency vibrations may occur in both the in-line and cross-flow directions, with a frequency ratio close to 2. Each excited frequency is associated with a single structural wavenumber. The local synchronization between the vortex shedding and the cross-flow oscillation, i.e. the lock-in condition, occurs in the high velocity zone and covers a similar spanwise extent in both the mono- and multi-frequency cases. Counter-clockwise figure-eight trajectories are very likely to occur within the lock-in region. In both the mono- and multi-frequency types of response, the flow excites the structural vibrations within the lock-in region and damps the structural motions in the non-lock-in region. The multi-frequency character of the response impacts both the lock-in phenomenon and the fluid–structure energy transfer.

A unified approach to orbital, solar, and lunar forcing based on the Earth’s latitudinal insolation/temperature gradient

Widespread empirical evidence suggests that extraterrestrial forcing influences the Earth’s climate, but how this could occur remains unclear. Here we describe a new approach to this problem that unifies orbital, solar and lunar forcing based on their common control of the Earth’s latitudinal insolation gradient (LIG). The LIG influences the climate system through differential solar heating between the tropics and the poles that gives rise to the latitudinal temperature gradient (LTG), which drives the Earth’s atmospheric and (wind driven) ocean circulation. We use spectral analysis of recent changes in the Earth’s LTG to support earlier work on orbital timescales ( Davis and Brewer, 2009) that suggests the climate system may be unusually sensitive to changes in the LIG. Identification of LIG forcing of the LTG is possible because the LIG varies according to seasonally specific periodicities based on obliquity in summer (41 kyr orbital and 18.6 yr lunar cycle), and precession (21 kyr orbital cycle) and total solar irradiance (11 yr solar cycle) in winter. We analyse changes in the Northern Hemisphere LTG over the last 120 years and find significant (99%) peaks in spectral frequencies corresponding to 11 years in winter and 18.6 years in summer, consistent with LIG forcing. The cross-seasonal and multi-frequency nature of the LIG signal, and the diffuse effect of the LTG driver on the climate system may account for the complexity of the response to extraterrestrial forcing as seen throughout the climatic record. This hypersensitivity of the LTG to the LIG appears poorly reproduced in climate models, but would be consistent with the controversial theory that the LTG is finely balanced to maximise entropy.

Quantum equations of motion for multimode laser generation with a spatial dependence of the atom interaction with the field taken into account

We derive equations of motion for the electromagnetic field operators a + aq for a three-level multimode laser with a spatial dependence of the interaction of atoms with the field of a standing wave in a cavity taken into account. We calculate and analyze the dynamics of means of photon numbers in the field modes and of the correlation function of field modes. We explore the effect of intermode correlations on the dynamics of establishing stationary laser generation. We find that taking the spatial dependence of the interaction of atoms with the field and the intermode correlation into account in investigating the means of photon numbers leads to revealing new properties of laser generation, such as saturation of the laser radiation intensity in a single-mode regime and generation of short light pulses of side below-threshold modes with the amplitudes depending on the initial state of the field in a cavity. Under the condition that the width of a laser amplification line (the rate of damping of the active medium polarization) is of the order of or greater than the intermode gap of eigenfrequencies in a cavity, laser generation has a multimode (multifrequency) nature. In real conditions, a small increase above the generation threshold, when the pumping is relatively small, can already lead to excitation of several eigen- modes of the laser cavity. With an increase in pumping, the number of modes involved in the generation and having intensities comparable to each other rapidly increases and can attain large values (up to sev- eral hundreds). The complicated dynamics of the multimode generation of different lasers are currently widely investigated both theoretically and experimentally. The theoretical analysis of multimode genera- tion encounters major complications because we must take intermode interactions into account, together with the spatial dependence of the interaction of the active medium atoms with a spatially inhomogeneous electromagnetic (EM) field in the cavity, which shows up, in particular, in the effect of spatial burning of a hole. The semiclassical theory of multimode (multifrequency) laser generation was developed in (1)-(10), where the Maxwell equations for a classical EM field were considered and the active medium was described quantum-mechanically in terms of a density matrix (operator) and an ensemble of two-level atoms. A full quantum mechanical theory of multimode generation was considered in (1), (11)-(16). The approximation of identical modes was used in (12)-(16). We note that in (1)-(4) in the semiclassical theory, the phenomenon of spatial burning of a hole in the population inversion of an active medium was regarded as the main reason and the necessary condition for the occurrence of stable multimode laser generation with a homogeneously broadened line. The approximation of identical modes, broadly used in the theory of multimode laser generation (12)- (16), in some cases allows assessing the generation dynamics qualitatively, but in the general case and for a

Image reconstruction using spectroscopic and hyperspectral information for compressive terahertz imaging

Terahertz (THz) time-domain imaging is an emerging modality and has attracted a lot of interest. However, existing THz imaging systems often require a long scan time and sophisticated system design. Recently, a new design incorporating compressed sensing (CS) leads to a lower detector cost and shorter scan time, in exchange for computation in an image reconstruction step. In this paper, we develop two reconstruction algorithms that can estimate the underlying scene as accurately as possible. First is a single-band CS reconstruction method, where we show that by making use of prior information about the phase and the correlation between the spatial distributions of the amplitude and phase, the reconstruction quality can be significantly improved over previously published methods. Second, we develop a method that uses the multi-frequency nature of the THz pulse. Through effective use of the spatial sparsity, spectroscopic phase information, and correlations across the hyperspectral bands, our method can further enhance the recovered image quality. This is demonstrated by computation on a set of experimental THz data captured in a single-pixel THz system.

Multifrequency nature of the 0.75 mHz feature in the X-ray light curves of the nova V4743 Sgr

We present timing analyses of eight X-ray light curves and one optical/UV light curve of the nova V4743 Sgr (2002) taken by CHANDRA and XMM on days after outburst: 50 (early hard emission phase), 180, 196, 302, 371, 526 (super soft source, SSS, phase), and 742 and 1286 (quiescent emission phase). We have studied the multifrequency nature and time evolution of the dominant peak at ~0.75 mHz using the standard Lomb-Scargle method and a 2-D sine fitting method. We found a double structure of the peak and its overtone for days 180 and 196. The two frequencies were closer together on day 196, suggesting that the difference between the two peaks is gradually decreasing. For the later observations, only a single frequency can be detected, which is likely due to the exposure times being shorter than the beat period between the two peaks, especially if they are moving closer together. The observations on days 742 and 1286 are long enough to detect two frequencies with the difference found for day 196, but we confidently find only a single frequency. We found significant changes in the oscillation frequency and amplitude. We have derived blackbody temperatures from the SSS spectra, and the evolution of changes in frequency and blackbody temperature suggests that the 0.75-mHz peak was modulated by pulsations. Later, after nuclear burning had ceased, the signal stabilised at a single frequency, although the X-ray frequency differs from the optical/UV frequency obtained consistently from the OM onboard XMM and from ground-based observations. We believe that the late frequency is the white dwarf rotation and that the ratio of spin/orbit period strongly supports that the system is an intermediate polar.