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This paper presents a quantitative analysis of the differences between the various definitions of spatially averaged power densities ( $sIPD_{s}$ ) for localized exposure to electromagnetic near-fields at frequencies from 6 to 100 GHz. The spatially averaged modulus of the complex Poynting vector ( $sIPD_{mod}$ ) and spatially averaged norm of the real part of the complex Poynting vector ( $sIPD_{norm}$ ) were compared using numerical approaches, where their relationships with the spatially averaged absorbed power density (sAPD) and the local peak temperature elevation on skin tissue were analyzed. Our results demonstrated that outside the typical boundary of the reactive near-field, i.e., $> \lambda $ /( $2\pi$ ), which is used as a rough guide of the applicable condition for reference levels in the RF safety guidelines, but at most 10 mm from the radiation source, the maximum difference between $sIPD_{norm}$ and $sIPD_{mod}$ is smaller than 0.7 dB from 6 to 100 GHz. For the appropriate conditions recommended in the RF safety guidelines, the differences between the ratios of sAPD to $sIPD_{s}$ and those for the plane-wave normal incidence, are at most 1.4 dB and 0.9 dB for $sIPD_{norm}$ and $sIPD_{mod}$ , respectively. Under the same condition, the ratios of the temperature rise to $sIPD_{s}$ for the relatively small antennas (total dimension less than $2\lambda$ ) do not significantly exceed that for the plane-wave normal incidence, which means that the expected maximum temperature rise is lower than the temperature rise that is derived from the operational health effect threshold in terms of the temperature rise divided with the reduction factors employed in the RF safety guidelines. The above results provide suggestive evidence that the effect of the definition of $sIPD_{s}$ on the human exposure characteristics is not significant compared with those of the other factors, i.e., the antenna type (size), frequency, distance from the source, and averaging area.

Publisher Copyright: © 1964-2012 IEEE. This article reports on an intercomparison study on the effect of the incidence angle on the spatial average of incident power density (PD) and resultant temperature rise using computational and thermographic measurement approaches. Two definitions of the spatial average of incident PD - the peak spatial-average normal component of the Poynting vector and peak spatial-average norm of the Poynting vector - were compared. First, an intercomparison of incident PD and temperature rise in a layered skin model was conducted for a 4 × 4 dipole array antenna. The variations caused by antenna type, antenna-body distance, and skin model to these definitions were then discussed. The results revealed that both definitions are in good agreement and correlate with the peak temperature rise for small or moderate incidence angles. The heating factor was enhanced for transverse-magnetic-like polarized waves for peak spatial-average normal component of the Poynting vector for large-angle incidences because of the Brewster effect. The normal incidence scenario was confirmed to be essential for considering the peak skin temperature rise.

In this paper, a method to design the power flow and energy management controller is proposed, for a hybrid energy storage system with battery and EDLC on an assumed electric vehicle. Numerical simulation under an assumed speed profile is carried out to reveal the power and the energy profile of the ESDs under the wide frequency range of the load power. The overall loss in the ESDs and the DC/DC converter are evaluated, according to the power and the energy profile of the ESDs. The time constant of the filter $T_{EDLC}$ for the controller is proposed to be set shorter as far to smooth the battery power not to absorb the regenerative power. EDLC is mounted less as far not to increase to the energy loss in the EDLC, under the condition of the designed controller.

This paper proposes the novel approach employing the kernel method as regression model to describe the dependency of magnet flux linkage on applied current, which is suitable for magnet temperature estimation. The model estimates flux linkage values with mean relative error of less than 2% compared to values calculated from finite element analysis (FEA). Magnet temperature is estimated by comparing a magnet flux linkage under loaded condition to the values from the regression models built under fixed temperatures. Results of the magnet temperature estimation method is about the same accuracy of the results using look-up table (LUT), hence it suggests the approach is suitable for non-linear motor property modeling.

Torque measurement/estimation in Variable Leakage Flux Permanent Magnet Synchronous Motors (VLF-PMSMs) is required in many applications. Torque measurement systems are expensive, require extra room, add weight, can introduce resonances into the system and can be sensitive to electromagnetic interference. Alternatively, torque can be estimated, accurate knowledge of machine parameters being often required in this case, which for the case of VLF-PMSMs can be a serious drawback due to the large variation of machine parameters with the operating condition. This paper proposes a torque estimation method for VLF-PMSMs based on stator flux linkage estimation. Machine parameters involved in stator flux linkage estimation are obtained from the response of the machine to a pulsating high frequency current signal and a low frequency and small magnitude, square-wave current signal. Both signals are injected on top of the fundamental excitation and without interfering therefore with the normal operation of the machine.

This study investigated the definition of power density for local exposure to electromagnetic fields (EMFs) by an antenna positioned near-by a human body at frequencies over 6 GHz. The relationship between the surface temperature elevation and the power densities in various near-field exposure conditions was analyzed. The results show that the applicability of the incident power density limits depends on the many factors, such as frequency, antenna, and antenna to body separation distance. Moreover, the analysis of heating factors of the absorbed power density demonstrated the dependence of locality of exposure. The findings obtained in this study may support the local exposure limits on the spatially-averaged power densities in safety guidelines and standard above 6 GHz.

In this study, we focus on a measurement method to assess power density near by upcoming wireless communication devices operating using quasi-millimeter wave and millimeter wave frequencies, e.g., 5G mobile devices. The measured power density is used to assess the applicability to radio-frequency exposure guidelines: compliance assessment. Here, incident power in the near-field radiated from a phased array antenna was estimated using reconstruction algorithm based on the plane wave expansion technique. It was found that the reconstruction error for maximum values of the spatially averaged power density is smaller than 0.4 dB at 2 mm and larger distances from the antenna. In addition, the effects of the electric field measurement uncertainties for each amplitude and phase to the power density were estimated by Monte Carlo simulation.

Use of Millimeter wave (MMW) frequencies in 5G and WiGig wireless devices will increase the public concerns on human safety for electromagnetic fields exposure. Major health effects due to MMW exposure are the local temperature elevation on the skin surface. To evaluate the heating effects caused by wireless devices employing MMW frequencies, it is essential to develop a human-skin equivalent phantom to represent the required surface temperature elevation on a multi-layer skin model.

This study aims to develop an experimental approach to estimate the transmitted power density inside human body for dosimetry study of millimeter wave exposure. We developed a temperature measurement system comprised of a millimeter wave generation apparatus at 60 GHz, a semi-solid glycerin phantom and an infrared camera. Based on this system, an estimation method of transmitted power densities was proposed by analyzing the temporal trend of temperature elevation on phantom surface. The validity of the proposed method was confirmed for the case of using a standard horn, and some results of using multi-element patch array antennas were demonstrated.

Biological tissue has its own complex permittivity. Measurement of the complex permittivity of biological tissue has been conducted in many studies, however it is a macroscopic level study. On the other hand, when evaluating electromagnetic field exposure for the cell scale, data on the complex permittivity for the molecular level is required. The purpose of this study is to establish the scheme to estimate macroscopic complex permittivity of bio-molecules from microscopic molecular simulations. If the complex permittivity is obtained from theoretical simulation, induced electromagnetic fields within biological-cells will be predicted, and it helps to discuss possible effects of electromagnetic field on the biological systems.

This paper presents the human exposure assessment to electromagnetic field at millimeter wave frequencies. The analysis of steady-state skin temperature elevation in various exposure conditions is introduced. The impact of the definition of the power density on dosimetric characteristics is also discussed for human safety guidelines.

Dynamic manipulation of magnetization state (MS) in variable flux permanent magnet synchronous machines (VF-PMSMs) during normal operation based on the torque-speed operating conditions has been shown to significantly reduce machine losses over urban driving cycles. However, the additional losses that are induced during the dynamic MS manipulation have not been evaluated. This paper presents a combination of finite element analysis (FEA) and experimental high bandwidth measurement techniques to estimate the transient losses during dynamic MS manipulation. The effect of these losses on the magnet temperature is analyzed experimentally and also by using a thermal equivalent circuit.

Variable flux permanent magnet synchronous machine (VF-PMSM) traction drives are capable of significant loss reduction over an electrical vehicle drive cycle using dynamic magnetization state (MS) manipulation. A continuous, online MS estimation method is desirable for VF-PMSM drives to optimally utilize the loss minimization capability with precise MS control. This paper presents a MS estimation method that uses flux observers and a structured neural network (SNN) based machine model to achieve high accuracy with low sensitivity to load current and a fast dynamic response. The steady state performance of the proposed method in the presence of load current is evaluated experimentally in the current plane as well as in the torque-speed plane. The effect of magnet temperature on MS estimation accuracy is also evaluated experimentally. The transient performance of the proposed method during MS manipulation transients is evaluated using FE methods.

Variable flux permanent magnet synchronous machines (VF-PMSMs) use permanent magnet magnetization as an additional degree-of-freedom to reduce losses based on operating conditions (e.g., at medium to high speeds, losses are reduced by using a lower magnetization). Magnet properties are known to be dependent on temperature; therefore, the magnet temperature effects on magnetization manipulation and maximum torque properties in VF-PMSMs are investigated in this paper with FEA simulations and experiments. Increased magnet temperature changes the available range of attainable magnetization levels and makes demagnetization occur more easily; therefore, a different current angle and magnetization are needed for maximum torque operation. The temperature effects on high speed magnetization manipulation methods, which are needed for driving cycle loss reduction and full power capability, are evaluated with simulation and experiments on a prototype 80 kW traction machine. A closed loop method for magnetization manipulation that mitigates the effect of temperature is proposed.

Variable flux permanent magnet synchronous machines (VF-PMSMs) in which the magnetization state (MS) of low coercive force (low-H c ) permanent magnets can be actively controlled to reduce losses in applications that require wide-speed operation have been proposed recently. While prior focus has been on achieving MS manipulation without over-sizing the inverter and obtaining higher torque capability, this paper extends the design objectives to include the power requirements of an electric vehicle traction motor over its entire speed range. Finite element methods are used to study the effect of combinations of low-H c and high-H c permanent magnets arranged in either series or parallel on the performance of VF-PMSMs. It is shown that while both configurations help improve the torque density, only the series configuration can help improve the high speed power capability. Experimental results showing the variable MS property, torque-speed capability and loss reduction capability of a series magnet configuration VF-PMSM test machine are presented.

This paper discusses various transient trajectories for increasing the magnetization state (MS) of variable flux permanent magnet synchronous machines (VF-PMSMs), a class of PMSM where the magnets are demagnetized and remagnetized using the drive inverter during drive cycle operation. To manipulate MS, a magnetizing current pulse can be used, which may drive a large amount of flux linkage in the machine. As a result, above low speed operation, a large voltage may be required from the inverter. This paper extends several existing methods for improved voltage properties, and proposes and experimentally evaluates a new method — a straight line stationary frame flux linkage trajectory (SLλsT) — for higher speed capability. The presented trajectories, along with existing trajectories, are organized into families and compared regarding their required voltage, high speed capability, torque ripple, and time duration.

The dielectric properties of skin layers, which are the epidermis, dermis, and subcutaneous fat, were measured using several measurement systems. Measurements were conducted in vitro from 0.5 GHz to 1 THz. Measurement results indicated good agreement between each measurement system at a tissue temperature of approximately 35 oC.

The absorption spectra of dried porcine dermis were measured under different sample handling conditions in a terahertz band from 0.3 to 12 THz. The spectral shapes and polarization properties depended on the drying and impurity conditions at approximately 3 THz. We inferred that the configuration changes of collagen fibers inside the dermis caused the spectral variations.

Nowadays, trials to use even higher frequencies are pursued to realize high-speed wireless communications. In order to respond to such a trend, dielectric properties of insulating polymers at high frequencies have to be clarified, although the importance of clarifying low-frequency properties is still very high, especially for use as high voltage insulators. In this regard, complex permittivity spectra in an ultrawide frequency range were obtained for various insulating polymers. These spectra are important, because they can be a valuable database that provide important information on dielectric characteristics. Furthermore, by analyzing the temperature dependence of permittivity in a relatively low frequency range, thermal expansion coefficients of polymers were estimated.

The ocular damage caused by MMW exposure is highly depends on the temperature elevation in the anterior part of the ocular tissue with the complicated structure. Especially, aqueous humor in the anterior chamber affects the nature of heat transport under the MMW exposure. In this study, we have originally developed the coupled analysis system on electromagnetic field (EMF) and heat transport (HT) including the fluid convection model. As an example of non-linear HT analysis, distributions of temperature elevation and aqueous humor flow are calculated in the condition of 75GHz, 150mW/cm2 MMW exposure.

We analyzed temperature increase in the post-wall waveguide type millimeter-wave exposure apparatus in vitro. This results show a similar tendency to the experimental results. The cooling effect in a state of natural cooling was 35–55 % by using heat sink as a basic cooling element. It allows the evaluations for non-thermal effects to expose MMWs of higher intensity than conventional exposure apparatus.

It has been demonstrated that millimeter waves (MMW) are absorbed by surface tissue, such as skin or cornea. It was shown in our laboratory that damage from MMW exposure was related to heat accumulation and transport. To study the relationship between relative humidity and ocular damage, we investigated the effect of relative humidity during MMW exposure. The ocular temperatures of rabbits were measured during exposure to 40 GHz MMW (200 mW/cm2). To visualize the dynamic change of temperature and distribution in the anterior chamber, 0.2% microencapsulated thermochromic liquid crystal (MTLC) was injected into the anterior chamber of rabbit eye. We showed that low humidity during exposure decreased heat accumulation and transfer.

The dielectric property values of biological tissues are used for the safety analysis and development of medical applications. A previous study conducted by Gabriel et al. has provided reference dielectric databases. To the best of our knowledge, no other databases have been constructed that allow a comprehensive measurement to be conducted with such a large number of tissues and organs. To this end, we present the development of a novel database for adaptation to recent research, permitting the validation of measured dataset by Gabriel et al. In this paper, we introduce measurement systems for further developing the database and summarize our findings with a discussion on the remaining challenges.

In vivo ocular temperatures in rabbits were measured during 40 GHz millimeter-wave exposure (400–100 mW/cm2). To visualize aqueous humor convection, 0.2% microencapsulated thermochromic liquid crystals (MTLCs) were injected into the anterior chambers of rabbit eyes. Exposure to 40 GHz increased corneal, lens and retrobulbar temperature, with aqueous humor convection having an important role in heat transfer from the cornea to the lens. These findings show that dynamic changes in temperature and distribution in the anterior chamber occur in living rabbit eyes during exposure to 40 GHz millimeter-waves.

The last mile solutions for high-speed high-capacity optical networks capable of securely supporting large number of simultaneous users by minimal hardware requirements are needed but it seems that any such solutions are still far away. Access networks based only on a wavelength-division multiplexing (WDM), optical timedivision multiplexing (OTDM) or optical code-division multiplexing (OCDM) schemes can't do it as the standalone systems. Here we present a proof-of-concept field demonstration of the implementation of an incoherent OCDMA over OTDMA system (iOCDM-OTDM) using a 17km long bidirectional fiber link installed between the Strathclyde and Glasgow Universities. The performed system performance analyses include system scalability calculations and a system reach under the influence of transmission link physical impairments.

This paper presents results of our extensive investigation of OCDMA system performance under the influence of varying transmission link chromatic dispersion. The investigations were carried out using incoherent 2-dimensional wavelength-hopping/time-spreading (2D-WH/TS) OCDMA codes based on picosecond pulses on a 17 km long bidirectional fiber link installed between the Strathclyde and Glasgow University. From the BER data obtained during these studies we showed that a high penalty in terms of system performance can incurred for even small deviation from the link full chromatic dispersion compensation.

An incoherent OCDMA test-bed based on FBR technology with implemented 2D-TW OCDMA codes was used to investigate the influence of interference noise (IN) on the system BER performance. An all-optical signal processing technique was investigated to eliminate MAI+IN in this type of systems. The results demonstrate that this form of noise introduces significant system power penalties but its impact can be lowered by a combination of proper design of network parameters and by use of all-optical signal processing techniques.

High speed and secure optical code division multiple access signals were successfully transmitted over 160 meters free space and 20 km optical fiber links. This shows possibility of covering area where geographical complexities make fiber installation difficult.

The results of a range of experimental characterization exercises of interferometric noise (IN) for the case of a representative 2-D time spreading wavelength-hopping (2-D TW) optical code family are presented. Interferometric noise is evaluated at a data rate of 2.5 Gbps within an OCDMA network emulation test bed established utilising fibre Bragg grating encoders/decoders. The results demonstrate that this form of noise introduces significant system power penalties and must be taken into consideration in any OCDMA network designs and implementations.

We proposed and demonstrated 40Gbps, 256-label optical packet switching employing a clockless serial optical code label processing. Eight different SSFBGs label recognizers with high auto- to cross-correlation peak ratio were used for optical label correlation.

Synchronized optical code division multiplexing system using 128-chip orthogonal sequence SSFBG en/decoder was experimentally demonstrated. Multiplexing for more than 17 users is experimentally demonstrated with changing interference levels using orthogonal codes for reducing cross-correlation noise.

Optical code generation and discrimination at 40 Gbps were experimentally demonstrated using longitudinal mode modulation of MLLD in time-spread/wavelength-hopping optical code. The crosstalk of cross correlation after fiber transmission for 30 km was less than 10 dB.

For the first time, we experimentally demonstrated asynchronous ultrahigh speed optical label switching using 4 SSFBGs label recognizers with the guard time of 3 ns. We also confirmed that the optical label recognizer/processor can operate for optical label after 40 km of SMF transmission without dispersion compensation.