The optical properties of skin in the mid-infrared range are not known, despite their importance for e.g. non-invasive glucose monitoring. In this paper, transmission, absorption, scattering, and reduced scattering coefficients are quantified using a custom-built goniometer based on a quantum cascade laser operated at the glucose absorption band at a wavelength of around 9.7 μm. The measurements show a strong dominance of absorption and moderate contributions from scattering. The scattered radiation is dominated by single scattering events in the forward direction (g = 0.967) within the range of the investigated dermis layer thicknesses of up to 50 μm, whereby the fraction of multiple scattering is expected to increase with the layer thickness.
A detailed knowledge of optical properties of tissue is important for the development of non-invasive monitoring systems for clinical practice. However, tissue optical properties are rarely known in the mid-infrared wavelength range. Goniometry offers an opportunity to determine in particular the scattering properties of tissue. Here, a custom-built setup is presented for goniometric measurements in the mid-infrared based on quantum cascade lasers.
This letter highlights the application of quantum cascade lasers for stand-off detection and remote sensing. In particular, we review the topic of power scaling via beam combining architectures and conclude with remarks on generating axial symmetric irradiance profiles via incoherent aperture beam combining of individual quantum cascade lasers.
Three pyrotechnic compositions based on ytterbium /polytetrafluoroethylene/Viton (R) (YTV) 77/18/5, 82/13/5 and 87/8/5 wt.-% were compared to a baseline magnesium /polytetrafluoroethylene/Viton (R) (MTV) 60/35/5 wt.-% composition. YTV though energetically inferior to MTV both gravimetrically and volumetrically exhibit a radiance L? (W.sr1.cm2) superior to MTV in the important beta-band (? = 3.54.6 mu m). This is assumed to be due to the selective emissivity of Yb2O3 which is formed in the afterburning zone of YTV. The emissivity of Yb2O3 is 710 times higher than that of MgO in the same spectral range. Due to the high density of ytterbium and the formulations based thereon YTV are promising candidates for autophagous nose cones for kinematic blackbody flares.
Modern electronic systems are susceptible to intense electromagnetic fields. Due to the small feature size and the low supply voltage of the electronics, the currents and voltages induced in signal and power lines cause malfunction of electronic circuits and components. During decades high power electromagnetic sources have been developed providing electromagnetic fields in the order of several hundreds of Mega Watts up to the Giga Watts level. For electronic components and smaller electronic systems, protection against the powerful electromagnetic radiation may be realized on a component or on a sub-system level. However, for larger electronic systems or electronic based infrastructures like communication centres, control centres or power plants, provision of a protected “hotel room atmosphere” and therefore shielding of the room or building itself may be mandatory. A new time domain measurement technique has been developed, which allows to measure shielding efficiencies already during the construction phase of a building in order to ensure proper shield installation. High power electromagnetic pulses may also being used to defeat against modern electronic weapon systems and other electronic threats. Various HPEM sources have been developed emitting high power electromagnetic radiation in a single pulse or a burst of pulses targeting the control and computer electronics of modern electronic systems and infra structures. Those sources are able to disrupt the control units of engines and may be used to stop cars, to control admission to sensible or high value areas or to stop speed boats or jet-skis in order to control access to harbours and moored ships from sea side.
In this paper we outline our researches of high- frequency electromagnetic field-coupling to small antennas in cylindrical cavities. This problem has many practical applications in EMC, e.g., for airplanes, etc. (small) radius potential in quantum mechanics (11- 12). The method of MSA is based on the analysis of the integro-differential equation describing the induced current in the neighborhood of the antenna. The corresponding resonator Green's function is splitted into two parts: a singular and a regular part. The singular one is connected with electrostatic and magnetic energy stored in the neighborhood of the antenna, and coincides with the singular part of the Green's function in free space. The regular part is connected with far field and contains all information about the system's resonances. Of course, there is a difference between the free space and resonator Green's functions. However, for both cases the regular part is constant in the neighborhood of the antenna. This circumstance gives the possibility to analytically express the solution for coupling current in the small antenna from solution in free space and to investigate the input impedance of small antenna, current transfer ratio for two small antennas, and also the coupling of penetrated radiation with a small antenna, etc. In literature, the most close method to our is the method described in paper (13) where authors calculate the input impedance of a small dipole antenna in a resonator with further investigation of the statistical properties of the impedance. To obtain the input impedance for the small antenna they practically have used another method of splitting the resonator Green's function - using the Coulomb gauge for the vector and scalar potential.
This paper proposes a test procedure to determine safety distance of systems containing EID in a pulsed electromagnetic environment (EME). The test procedure is based on a radiative emission measurement in order to capture maximum EMC generated EID bridgewire temperature. The paper describes the test setup, the dynamic measurement requirements, the calibration and test routine and the derivation of the EID safety distance for pulsed EME. As an example, the safety distance has been determined experimentally for a generic EID test setup at high power damped-sinusoid (DS) irradiation.
5H-Perfluoroalkyltetrazoles (alkyl = CF3, C2F5, C3F7) react with aqueous Ca(OH)2 to give the corresponding calcium salts 1, 2 and 3. Compounds 1 – 3, which form hydrates, were characterized by elemental analyses, differential heat flow calorimetry, multinuclear NMR, FTIR and Raman spectroscopy. A crystal structure determination was carried out on the solvate 2 ·2H2O·4CH3OH. Compounds 1 – 3 were tested as oxidizers in ternary pyrolant mixtures with magnesium and VitonTM. The burn rates, u (g s−1), of the pyrolants based on 1 show a distinct influence of the exothermicity of the primary reaction, whereas the burn rates of 2- and 3-based pyrolants do not show such behavior but display a steady increase of burn rate with increasing Mg content. At stoichiometries below 40 wt.-% Mg, the specific intensity Eλ (J g−1 sr−1) of the pyrolants based on 2 and 3 is superior to that of the standard mixture magnesium/polytetrafluoroethylene/VitonTM (MTV). This is assumed to be due to the expansion of the flame envelope by nitrogen.
A robust autopilot design methodology using linear parameter varying transformations is presented and applied to a high-agile surface launched air defence missile, which is currently developed by Diehl-BGT-Defence. The lateral dynamics of the tail/thrust vector controlled missile are modelled as a second-order quasi-linear parameter varying (LPV) system. The incidence angle is used as exogenous variable, which is assumed to be estimated during missile flight. Decoupled lateral dynamics are assumed because of the application of a bank-to-turn manoeuvre plane angle control approach. Lateral single channel flight controllers are designed via H ∞ -optimal control and μ-synthesis with the LPV lateral dynamics, which are extended by uncertain models of control actuating system, time-delay and body bending model. The flight controllers for lateral dynamics are designed at a number of operating points described by the LPV model over the MACH flight envelope. The controllers are implemented using a gain scheduling approach, where an altitude dependent gain loss in the control loop is compensated with the inverse normalised air density. The flight controllers were implemented in the nonlinear simulation environment and tested in extreme flight manoeuvres. All flight controllers showed good damping and acceleration tracking performance and were stable during nonlinear simulations.
Different approaches to power scaling of 4.5- to 5-mum emitting quantum cascade (QC) lasers by multiemitter beam combining are investigated. Spectral beam combining of linear arrays of QC lasers consisting of several individual emitters located side by side is demonstrated as a first variant, using an external cavity equipped with a diffraction grating and a partially transmitting output mirror providing wavelength-selective feedback to each emitter. In this way, spectral beam combining of up to eight individual QC lasers is achieved with an optical coupling efficiency of 60% for an array of six emitters. The resulting beam quality (M 2 < 2 for both fast and slow axes) is close to that observed for single emitters. As a second approach, a linear array of QC lasers is coupled to a custom-made array of silicon microlenses positioned in front of the output facets of the QC lasers. This technique produces a set of closely spaced parallel output beams, strongly overlapping in the far field, without introducing any coupling losses. The resulting beam divergence is given by the aperture size of the microlenses, which is limited by the center-to-center spacing of the QC lasers (500 mum in our case).
Asymmetric attacks against maritime platforms often emerge suddenly, non-predictably and from civil environments. Adequate reaction to intercept possible threats requires a quick and overall perception of the emerging situation. For this purpose close-in range surveillance systems capable of day- and night imaging can provide powerful support with respect of enhancing operator's situational awareness and therefore platform security. We report here on a two-stage concept for a maritime surveillance system. A staring wide area sensor package equipped with uncooled infrared sensors is intended to continuously provide high quality imagery of the platform surrounding. The image data is permanently evaluated using signal processing algorithms particularly suited for the detection of potentially asymmetric threats in maritime environments. In case of threat detection an alarm is generated automatically. In a second step, objects found in the ships vicinity are verified by an electro-optical sensor platform possessing higher resolution and sufficient agility for multi-target tracking. The components of the sensor suite including the staring wide area surveillance sensor, the agile electro-optical sensor platform and the processing cabinet are connected via Ethernet. Both, fully autonomous operation of the sensor suite with stand-alone HMI capability as well as integration into an existing combat management system are possible. The system provides robustness against maritime environmental conditions and requires little maintenance and is suited for integration to military and civil maritime platforms.
The recent break-through in semiconductor laser-module technology in the infrared region between 2 mu m and 10 mu m opens up new windows of opportunity for active sensing, imaging, and modulated power projection. Optically pumped semiconductor disk lasers and quantum cascade lasers cover the infrared spectral range continuously, either with tuneable small bandwidths for active spectral sensing or with broad bandwidth, high power (Watt level), and good diffraction properties (M-2<2) for modulated power projection and (3D) imaging. This paper reviews the physics of infrared semiconductor disk lasers and quantum cascade lasers, explains the challenges of the module technology (the next higher integration level after chip technology) and outlines several security and defence related issues for future applications.
Pyrolants containing magnesium and guanidinium 5-(perfluoropropyl)-5H-tetrazolate (1) and ammonium 5-(perfluoropropyl)-5H-tetrazolate (2) as oxidizers yield superior spectral efficiency compared to MTV. This is assumed to be due to the expansion of the radiating core zone with nitrogen which reduces the optical thickness in comparison to the core zone of MTV. In addition, the exothermal decomposition of the tetrazolate entity favors a burn rate that is dependent on heat feedback from the gas phase and thus proves to be a function of the flame temperature thus facilitating high burn rates at low Mg contents which is contrary to common metal based pyrolants. For part X., see Ref. .
A melt casting technique for ammonium dinitramine (ADN) and ADN/aluminum was developed. ADN proved relatively easy to cast, when 1% of magnesium oxide was used as a stabilizer and crystallization kernels. Densities of ADN/MgO 99/1 were 92 to 97% of theoretical mean density (TMD) and those of ADN/Al/MgO 64/35/1 were between 95 and 99% of TMD. Sedimentation of Al in the melt was prevented and the particle wetting was ensured by selecting a suitable particle size for Al. No gelling agents or other additives were used. The casting process and factors influencing it are discussed.
Point Spread Function (PSF), Modulation Transfer Function (MTF) and Ensquared Energy (EE) are important performance indicators of optical systems for surveillance, imaging and target tracking applications. We report on the development of a new measurement method which facilitates fast real time measurement of the two dimensional PSF and related performance parameters of a MWIR optical module under room temperature as well as under extreme temperature conditions. Our new measurement setup uses the law of reversibility of optical paths to capture a highly resolved, magnified image of the PSF. By using of an easy add-on thermally insulating enclosure the optical module can be exposed to and measured under both variable high and low temperatures (-50°C up to 90°C) without any external impact on the measurement. Also line of sight and various off-axis measurements are possible. Common PSF and MTF measurement methods need much more correction algorithms, whilst our method requires mainly a pinhole diameter correction only and allows fast measurements of optical parameters under temperature as well as fast and easy adjustment. Additionally comparison of the captured, highly resolved PSF with optical design data enables purposeful theoretical investigation of occurring optical artifacts.
A possible technique to determine EMC safety distance of electro-initiated devices (EID) is the use of fiber-optic temperature sensors which are thermocoupled to the EID bridgewire . Despite of excellent measurement properties, e.g. temperature range (typ. -100°C - 300°C) and temperature resolution (typ. 0.1°C)  theirs basic disadvantage is the limited speed of about 1 ms measurement rate. Therefore, this technique is an ideal candidate for EMC immunity tests in a continuous wave (CW) environment where only steady-state temperature measurements are required but not in a pulsed environment where the measurement rate needs to be much shorter than the thermal time constant of the EID in order to capture maximum EMC generated bridgewire temperature. To overcome the limited measurement rate, radiative temperature measurement techniques seem most promising . This paper investigates the application of an infrared mercury-cadmium-telluride (MCT) based radiation thermometer within a pulsed high-power electromagnetic (HPEM) environment in order to measure induced EID energy and to determine EID safety distance.
The paper investigates electromagnetic effects on an extended generic CAN-bus network during HPEM exposure. The major point of entry represents the network cable which is performed either as an unshielded parallel wire, an unshielded twisted pair or as a shielded twisted pair.
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