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International audience; The use of structural adhesive bonding is under development for offshore applications and more specifically for fastener connection to existing steel structures. For this application, creep appears to be one of the main long-term phenomena that needs to be considered during the design approach. To investigate this issue, experimental creep investigations were realised at real scale for two bonded fastener geometries at different stress levels and under different load situations (tension and shear). Local measurements were carried out during these investigations to better describe the long-term behaviour of the bonded fasteners. Despite the non-uniform adhesive thickness in the assembly, numerical investigations have highlighted that the stress field mainly depends on the fastener geometry and the applied load level. This article is dedicated to the description of a methodology that relies on a precise inverse identification of creep parameters and on simplifying hypotheses on the stress field to be able to use simple analytical tools. The methodology enables to identify creep parameters much quicker than a method coupling an optimisation algorithm and a finite element analysis and could easily be used for more complex and precise models.

Parcel lockers and collection and delivery points are not new concepts and are recognized by many firms; however, they are not broadly utilized worldwide. The employment of this concept can provide a solution to failed deliveries. In this study, parcel lockers and similar concepts are reviewed quantitatively and analytically. Parcel lockers have been widely studied; however, quantitative approaches are lacking. Therefore, mathematical models, spatial analysis, optimization, and simulation studies on location and routing problems have been extensively examined. This study aims to indicate the current state and future directions. After a rigorous elimination process in the Scopus database, 72 papers were reviewed, and descriptive, bibliometric, and content analyses were performed. This study shows that parcel lockers and collection and delivery points offer various advantages as solutions to last-mile delivery problems, such as regulating traffic congestion, reducing faulty deliveries and the resulting costs, and increasing consolidation.

The discrete circle map is the archetypical example of a driven periodic system, showing a complex resonance structure under a change of the forcing frequency known as the devil's staircase. Adler's equation can be seen as the direct continuous equivalent of the circle map, describing locking effects in periodic systems with continuous forcing. This type of locking produces a single fundamental resonance tongue without higher-order resonances, and a devil's staircase is not observed. We show that, with harmonically modulated forcing, nonlinear oscillations close to a Hopf bifurcation generically reproduce the devil's staircase even in the continuous case. Experimental results on a semiconductor laser driven by a modulated optical signal show excellent agreement with our theoretical predictions. The locking appears as a modulation of the oscillation amplitude as well as the angular oscillation frequency. Our results show that by proper implementation of an external drive, additional regions of stable frequency locking can be introduced in systems which originally show only a single Adler-type resonance tongue. The induced resonances can be precisely controlled via the modulation parameters.

In recent years, the economic circumstances spur many companies in changing their traditional product-oriented value proposition toward a more customised and sustainable offer referred as Product-Service Systems (PSS). The main advantages of the new solutions are related to their customisation which can grant an improved customer experience. However, while pursuing greater differentiation from competitors and ‘locking-in’ customers and ‘locking-out’ competitors, many of the above-cited companies either miss interesting business opportunities or bet on the wrong solution concept. Early stage engineering phase plays a crucial role concerning the subsequent lifecycle phases, guiding the identification and the selection of valuable solutions while preventing commitment of resources on poor design alternatives. In the light of the criticality of this phase, this paper builds on empirical studies in the manufacturing industry and highlights the need for systematic procedures, methods and metrics able to encompass customer satisfaction together with the producer's value perspective during the early design assessment. The outcome of the paper is the Engineering Value Assessment (EVA) method. It is a 2 step procedure composed of multi-criteria decision-making methods with specific criteria for a comprehensive value assessment of PSS from both the customers’ and the provider's perspectives. The EVA also guides the identification of trade-off between the two through the Importance-Performance Analysis. Verification activities in the power and automation industry highlight the main benefits and the implications of the EVA method in guiding the decision making in the early stages of design and in balancing the trade-off between customer and provider value during the PSS assessment phase. Further developments and improvements are also discussed. © 2018 CIRP open access

A robust approach to excitation and control of large amplitude standing magnetization waves in an easy axis ferromagnetic by starting from a ground state and passage through resonances with chirped frequency microwave or similar alternative drives (spin torque, additional periodic anisotropy) is proposed. The formation of these waves involves two stages, where in the first stage, a spatially uniform, precessing magnetization is created via passage through a resonance followed by a self-phase-locking (autoresonance) with a constant amplitude drive. In the second stage, the passage through an additional resonance with a spatial modulation of the driving amplitude yields transformation of the uniform solution into a doubly phase-locked standing wave, whose amplitude is controlled by the variation of the driving frequency. The stability of this excitation process is analyzed both numerically and via Whitham's averaged variational principle. © 2019 American Physical Society.

International audience; Deep space missions keep pushing for new frontiers affecting a wide spectrum of disciplines. To support the scientific achievements expected from new missions, communication technology is being pushed towards its limits [1]. A need to increase communication links data rate as well as to lower the operative signal-to-noise ratio (SNR) are identified. The adoption of advanced coding schemes such as turbo codes and low-density parity-check (LDPC) codes (e.g., Consultative Committee for Space Data Systems (CC-SDS) standards) allows receivers to operate at lower SNRs. However, in order to exploit the full potential of the coding gain, the receiver must be able to acquire and track a signal with a SNR much lower than expected in nominal conditions of state-of-the-art systems. The target operating point is given by the candidate LDPC codes [2], where the codeword error rate is set to WER ≤ 10 -5 , achieved at the bit energy to noise density ratio E b /N 0 ≥ 5.2 dB, ≥ 3.6 dB for LDPC(128,64) and LDPC(256,128), respectively. In [3] the first receiver bottleneck related with frame synchronization, a functionality required previous to channel decoding, was identified. Even though frame synchronization enhancements were proposed beyond standard correlation techniques [3], [4], [1], it was recommended to increase the synchronization word length in order to achieve the target performance. The recommendation was recently adopted by the CCSDS. In this work, the focus lies on the receiver synchronization stages (i.e., acquisition and tracking). Not only from a research standpoint, but also for the design of next generation Telemetry Tracking & Command (TT&C) transponders, it is of capital importance to understand the performance limitations of state-of-the-art deep space communications architectures, clearly identifying possible bottlenecks and the synchronization stages (i.e., acquisition and tracking) to be improved. Digital carrier and timing synchronization have been an active research field for the past three decades in applications such as satellite-based positioning or terrestrial wireless communications systems. In those scenarios, the limitations of standard delay, frequency, and phase-locked loop (delay-locked loop, frequency-locked loop (FLL), and phase-locked loop (PLL), respectively) architectures have been clearly overcome by Kalman filter (KF) based solutions [5], which provide an inherent adaptive bandwidth, robustness, flexibility, and an optimal design methodology. Despite the advances in the field, synchronization architectures for deep space communications links, implemented in current TT&C transponders, still rely on well-known conventional architectures, which may be insufficient if limits are pushed to extremely low SNR or harsh propagation conditions. With the advent of powerful software defined radio receivers and new system design rules, it is now possible to adopt new robust architectures that may enable going beyond the performance and reliability provided by legacy solutions.

To develop the metal-organic framework (MOF)-based sensing of triethylamine (TEA) in an aqueous phase, Al-MIL-101-NH2 (MIL: Material Institute Lavoisier) with a tripod-like cavity was utilized based on a lock-and-key model. Al-MIL-101-NH2 (Al-MOF) was found to be an excellent fluorescent sensor for the TEA molecules in the range of 0.05-0.99 mM. The limit of detection (LOD) and linear calibration range of this probe towards TEA were found to be 3 μM and 0.05-0.40 mM, respectively. The mechanism of the sensing process indicates the dominant role of physical processes (e.g., non-covalent bond interactions). In addition, the exact fit of the TEA molecule (6.5 Å) in the tripod-like cavity (6.78 Å) supported the strong interaction between three ethyl groups (TEA) and aromatic rings (MOF). This kind of specific suitability between size/shape of the TEA and tripod-like cavity of MOF (ΔG: −46.7 kJ mol−1) was not found in other molecules such as ethylamine (ΔG: −2.20 kJ mol−1 and size: 3.7 Å), formaldehyde (ΔG: +1.50 kJ mol−1 and size: 2.8 Å), and ammonia (ΔG: +0.71 kJ mol−1 and size: 1.6 Å). As such, Al-MOF was found to be a selective and stable sensor for TEA. © The Royal Society of Chemistry. The rst author KV acknowledges Department of Science and Technology (DST) for providing Nano science and Technology (NST) post-doctoral fellowship (JNC/AO/A.0610(36)2017-2620) and the corresponding author acknowledge Department of Science and Technology (DST), Government of India for providing research funding DST/TN/WTI/WIC/2K17/82.

A double-scan-head was developed combining two pairs of galvo-mirrors into one device. One pair controls the laser beam's position, while the other in this setup is used for a pyrometer. Thus, a pyrometer's optical path can be controlled independently from a laser's path as well as being locked to the same geometrical path during CFRP processing. Using such a double-scan-head, a comparison between locked pyrometry and independent scanning pyrometry is performed during multi-pass laser cutting on multiple geometries. Carbon fibre reinforced epoxy and PPS are cut with pre-selected threshold surface temperatures ranging from T = 80-120 °C to interrupt and optimise the process in order to reduce the material's thermal strain. Both locked and scanning pyrometry are compared based on total processing time, heat affected zone, and the influence of fibre orientation. The study shows a double-scan-head allows improved process monitoring strategies leading towards more efficient laser material processing in terms of quality and time.

In this paper we investigate the dynamics of the classic synchronous reference frame phase-locked-loop (PLL) from a non-linear perspective. First, we demonstrate the nonlinear differential equations that describe the PLL under balanced conditions can be represented as a dissipative Hamiltonian system (DHS). After that, we find the equilibrium points of this system and their stability properties. Additional properties are investigated such as the attraction region, the conditions for exponential stability and the performance for small unbalances an d/or transients in the grid. Simulations results complement the theoretical analysis. We do not propose a new type of PLL, instead, we propose a non-linear analysis for the classic synchronous reference frame PLL. This analysis is useful for theoretical and practical studies since this PLL is widely used in industrial applications. In addition, it can give insights for better understanding of the dynamics of the phase-locked-loop1 1The presentation of this paper in the COMPEL2018 was partially supported by the Maestrfa en Ingeniería Eléctrica Universidad Tecnologica de Pereira. © 2018 IEEE. 1The presentation of this paper in the COMPEL2018 was partially supported by the Maestría en Ingeniería Eléctrica Universidad Tecnologica de Pereira

In this article, we study the size-dependent interactions of quasi-spherical nanocrystals with voids of concave nanoparticles of complementary sizes and shapes. Experimental insights into a system with key and lock particles with smaller dimensions than 15 nm are presented, which provide evidence for key-lock specific interaction on this length scale. Using depletion attraction as a driving force, the key-lock interaction is shown to be reversible and independent of the material composition of the key particles. Poly(ethylene glycol) methacrylate was utilized as a depletion agent in toluene, the solvent of the studied key-lock system. For this work, a model system of specifically developed concave manganese oxide nanocrystals, synthesized via a cast-mold approach, in combination with highly monodisperse quasi-spherical gold nanocrystals, was investigated with transmission electron microscopy, optical UV/vis/NIR spectroscopy and powder X-ray diffraction. Size-dependent key-lock interactions are clearly identified to occur. For geometrical reasons, only key particles with smaller particle diameters than the voids of the complementary lock particles are able to enter the void. So the void diameter of the lock particles sets a diameter threshold for the key-lock interaction. Additionally, other key particles like silver, iron oxide and even core-shell structured gold-nickel sulfide nanocrystals show key-in-lock assemblies with concave manganese oxide nanocrystals. This behaviour might open up new routes for size-selective particle sensing.

43rd. European Conference on Optical Communication (ECOC 2017), Gothemburg, 17-21 Sept., We demonstrate ultrafast harmonically mode-locked fiber lasing in up to 6-km-long rings at 1.56μm with InN SESAM. Fundamental mode-locking with pulse width of 239fs, pulse energy of 155nJ and peak power of 650kW is achieved with a 1-km-long cavity., European Commission, Ministerio de Economía y Competitividad, Comunidad de Madrid

An actively mode-locked fiber laser with regenerative stabilization established through a feed-back electronic amplifier operated in the saturation regime is reported in this paper. Compared to the regenerative stabilization schemes that employ phase-locked loops (PLL), a saturated amplifier has been used for inhibiting the transmission of amplitude noise through the feed-back chain. Such a laser system has been constructed, studied and characterized as a function of its design variables. Specifically, the electronic phase shift in the feed-back circuit and the RF power applied to the modulator have been varied to study their effect on the mode-locked pulse train. The influence of these parameters on super-mode noise is studied and the optimum values of phase shift and RF power of the recovered carrier at which the noise is found to be a minimum (-48 dB) has been determined. A comparison of systems with and without regenerative mode-locking under controlled conditions reveals that a regenerative system has at-least an order of magnitude better noise performance compared to a system without regeneration. � 2014 Elsevier Ltd. All rights reserved.

Space-to-Earth telemetry (TM) links have extensively exploited advanced coding schemes, from convolutional codes to Reed-Solomon codes. The Next Generation Uplink Coding Techniques (NEXCODE) study, funded under the Technology Research Program of the European Space Agency (ESA), aimed at research, design, development, and demonstration of a TC receiver chain for scientific missions, including new channel codes. Agencies and researchers investigated and compared a number of possible alternatives, including binary and non-binary LDPC codes even in the presence of jamming. The schemes were evaluated taking into account the peculiar characteristics of TC links in terms of coding gain and complexity. Commands from Earth to space are sent in the payload of TC transfer frames (TFs). A TF is divided into blocks, each as long as 56 bits and individually BCH encoded. The TC transmission protocol includes an additional mechanism that guarantees a minimum number of symbol transitions to keep symbol synchronization. In acquisition mode, the TC standard [15] specifies the use of a symmetric triangular carrier sweeping procedure with the purpose of locking to the carrier frequency. In this stage, the ground station (G/S) transmits an unmodulated carrier whose frequency is swept around the nominal carrier frequency. Carrier tracking in the baseline receiver is performed with a 2nd order PLL, which is compromised in the DS scenario by the noise reduction versus dynamic range trade-off.

Independent tuning of emission energy and decay time of neutral excitons confined in single self-assembled In(Ga)As/GaAs quantum dots is achieved by simultaneously employing vertical electric fields and lateral biaxial strain fields. By locking the emission energy via a closed-loop feedback on the piezoelectric actuator used to control the strain in the quantum dot, we continuously decrease the decay time of an exciton from 1.4 to 0.7 ns. Both perturbations are fully electrically controlled and their combination offers a promising route to engineer the indistinguishability of photons emitted from spatially separated single photon sources. © 2017 Author(s).

Soliton mode-locking in microresonators enables chip-scale coherent optical frequency comb generation. However, it usually leads to multi-soliton combs with a structured spectrum. Instead, the smooth spectrum of a single soliton is favored for applications. Here, we introduce, experimentally and numerically, a passive mechanism for single temporal soliton formation arising from spatial mode-interaction in microresonators. Deterministic single soliton generation is observed for microresonators with strong mode-interaction in experiments and simulations. Further simulations demonstrate that the soliton number is reduced to one in order to lower the nonlinear loss into mode-interaction induced Cherenkov radiation (CR). Our results give important insights into soliton–CR interaction in cavities.

The excitation of large amplitude, strongly nonlinear ion acoustic waves from trivial equilibrium by a chirped frequency drive is discussed. Under certain conditions, after passage through the linear resonance in this system, the nonlinearity and the variation of parameters work in tandem to preserve the phase-locking with the driving wave via excursion of the excited ion acoustic wave in its parameter space, yielding controlled growth of the wave amplitude. We study these autoresonant waves via a fully nonlinear warm fluid model and predict the formation of sharply peaked (extreme) ion acoustic excitations with local ion density significantly exceeding the unperturbed plasma density. The driven wave amplitude is bound by the kinetic wave-breaking, as the local maximum fluid velocity of the wave approaches the phase velocity of the drive. The Vlasov-Poisson simulations are used to confirm the results of the fluid model, and Whitham's averaged variational principle is applied for analyzing the evolution of autoresonant ion acoustic waves. © 2017 Author(s).

We demonstrate, what is to our knowledge, the shortest pulses directly generated to date from a solid-state laser, mode locked with a graphene saturable absorber (GSA). In the experiments, a low-threshold diode-pumped Cr3+: LiSAF laser was used near 850 nm. At a pump power of 275 mW provided by two pump diodes, the Cr3+: LiSAF laser produced nearly transform-limited, 19-fs pulses with an average output power of 8.5 mW. The repetition rate was around 107 MHz, corresponding to a pulse energy and peak power of 79 pJ and 4.2 kW, respectively. Once mode locking was initiated with the GSA, stable, uninterrupted femtosecond pulse generation could be obtained. In addition, the femtosecond output of the laser could be tuned from 836 nm to 897 nm with pulse durations in the range of 80-190 fs. We further performed detailed mode locking initiation tests across the full cavity stability range of the laser to verify that pulse generation was indeed started by the GSA and not by Kerr lens mode locking., European Research Council (ERC)

One of the main problems of magnonics is finding the ways of efficiently spin waves excitation in a magnet. This paper considers the method of nonlinear amplification by phase locking of amplitude of dynamic magnetization in yttrium-iron garnet film performed by micromagnetic modeling with MuMAX3 software taking into account the real materials parameters. It is shown that the excited magnetization precession can be considered as a autoresonance phenomena. The intensity of the autoresonance in ferrimagnetic yttrium-iron garnet films has threshold dependence on the chirp rate of the exciting magnetic field. © Published under licence by IOP Publishing Ltd. Russian Foundation for Basic Research, RFBR: 19-32-90014 Ural Branch, Russian Academy of Sciences, UB RAS: МК-4959.2018.2 The work was carried out within the framework of the state assignment on the topic "Spin" №АААА-А18-118020290104-2, "Alloys" № АААА-А19-119070890020-3 and project №18-10-2-37 of the Program of the UB RAS, supported by Grant of the President of the Russian Federation № МК-4959.2018.2, also the reported study was funded by RFBR, project number 19-32-90014.

When a rotating external field larger than a critical strength is applied to a meandering spiral with frequency close to the spiral frequency, the spiral may phase-lock to the applied field and perform rigid rotation instead. We show that this conversion happens by stabilization of an unstable circular-core spiral due to the external field. From calculating overlap integrals of adjoint critical modes (response functions), the Arnold tongue for phase-locking is predicted, matching the outcome from direct numerical simulations. © 2019 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft. Teng-Chao Li Bing-Wei Li Bo Zheng Hong Zhang Alexander Panfilov Hans Dierckx Teng-Chao Li Bing-Wei Li Bo Zheng Hong Zhang Alexander Panfilov Hans Dierckx Zhejiang Institute of Modern Physics and Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China Department of Physics and Astronomy, Ghent University, Krijgslaan 281, B-9000, Gent, Belgium Department of Physics, Hangzhou Normal University, Hangzhou 311121, People's Republic of China Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People's Republic of China Laboratory of Computational Biology and Medicine, Ural Federal University, Ekaterinburg, Russia Author to whom any correspondence should be addressed. Teng-Chao Li, Bing-Wei Li, Bo Zheng, Hong Zhang, Alexander Panfilov and Hans Dierckx 2019-04-01 2019-04-08 07:10:30 cgi/release: Article released cgi/article: new .article bin/incoming: New from .zip Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence . Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Natural Science Foundation of Zhejiang Province https://doi.org/10.13039/501100004731 LY16A050003 National Natural Science Foundation of China https://doi.org/10.13039/501100001809 11675141 11775186 China Postdoctoral Science Foundation https://doi.org/10.13039/501100002858 No. 2018M632444 yes When a rotating external field larger than a critical strength is applied to a meandering spiral with frequency close to the spiral frequency, the spiral may phase-lock to the applied field and perform rigid rotation instead. We show that this conversion happens by stabilization of an unstable circular-core spiral due to the external field. From calculating overlap integrals of adjoint critical modes (response functions), the Arnold tongue for phase-locking is predicted, matching the outcome from direct numerical simulations. General Scientific Summary Introduction and background . Spiral waves have been observed in diverse systems, from the well-known Belousov-Zhabotinsky reaction to cardiac tissue, where they cause life-threatening cardiac arrhythmias. The dynamics of a spiral wave is determined by the motion of its tip, also known as a "topological defect" or "phase singularity". Tip orbits are often not circular but follow complex cycloidal orbits, which is called "meander". It was hypothesized that spiral wave meander is the cause of a potentially lethal cardiac arrhythmia "Torsade de Pointes", which often occurs as a result of adverse drug action or genetic mutations. Thus, control of spiral wave meander is an important scientific question. Until now, several control schemes have been proposed to control or suppress meandering of spiral waves. Nevertheless, most of previous works are purely phenomenological and lack quantitative explanation. Main results . We propose a new way to control spiral wave meander, by application of a rotating external field which converts the spiral to a rigidly rotating spiral via phase-locking. Based on a response functions approach, we develop a quantitative theory to predict the stabilization regime and the conditions of phase locking and show that our theory is in excellent agreement with numerical simulations. Wider implications . We believe that the methodology presented here will be applicable to control spiral wave dynamics not only in chemical systems but also in other excitable systems in physics, chemistry and biology (e.g. cardiac tissue). 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A short pulse train with pulsewidth < 1 ps was generated in a quantum dot mode-locked laser (QD MLL). Due to the short dispersion length, it is required to include group-velocity dispersion (GVD) in modeling pulse train generation and evolution from QD MLLs. On the other hand, Kerr effect is also required to consider due to high peak power density in the laser cavity, and its induced self-phase modulation (SPM) also contributes to the pulse evolution. In this paper, a time domain traveling wave model, including the effect of GVD and SPM, combined with rate equations, is established to model the pulse evolution in a single-section QD MLL. It is shown that the pulse evolution calculated by this model is in reasonable agreement with the experiments. The contribution to the pulse evolution by the GVD and SPM impact is discussed.

International audience; This paper presents an energy-momentum method for nonlinear dynamics of 2D Bernoulli corotational beams. It is shown that the time stepping algorithm conserves energy, linear momentum and angular momentum. To be consistent in the corotational approach, cubic interpolations of Bernoulli element are employed to derive both inertia and elastic terms. The shallow arch strain definition is used to get an element which produce accurate results for less number of elements. To avoid membrane locking, we use a constant and average value of the axial strains. In addition, the energy-momentum method is used to preserve the conserving properties, which is able to maintain the stability and accuracy in a non-dissipative system for a long period. The midpoint velocities of kinematic fields and strains are used to tackle any non-linear form of strain displacement relations. Finally, two examples including large overall displacement are presented to illustrate the stability and efficiency of the proposed algorithms.

Object category localization is a challenging problem in computer vision. Standard supervised training requires bounding box annotations of object instances. This time-consuming annotation process is sidestepped in weakly supervised learning. In this case, the supervised information is restricted to binary labels that indicate the absence/presence of object instances in the image, without their locations. We follow a multiple-instance learning approach that iteratively trains the detector and infers the object locations in the positive training images. Our main contribution is a multi-fold multiple instance learning procedure, which prevents training from prematurely locking onto erroneous object locations. This procedure is particularly important when using high-dimensional representations, such as Fisher vectors and convolutional neural network features. We also propose a window refinement method, which improves the localization accuracy by incorporating an objectness prior. We present a detailed experimental evaluation using the PASCAL VOC 2007 dataset, which verifies the effectiveness of our approach., Comment: To appear in IEEE Transactions on Pattern Analysis and Machine Intelligence (TPAMI)

International audience; The generation of mid-infrared (mid-IR) radiation, ranging from 2 - 5 μm, is getting much attention in recent years thanks to many applications it can be used for, e.g. in free space optical communication, range finding, counter measures and remote chemical sensing systems. It also plays an increasing role in medicine, for instance in optical tissue ablation or optical coherence tomography, owing to the high water absorption in that wavelength range. In this research study, a ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fluoride fiber is pumped by a Q-switched mode-locked (QML) thulium (Tm3+)-doped double-clad silica fiber laser, emitting at around 2 μm, to generate mid-IR supercontinuum (SC). Further spectral broadening of this SC radiation is achieved by coupling it into a chalcogenide arsenide-selenide (AsSe) photonic crystal fiber (PCF). An output power of 24 W at 2 μm has been achieved in QML operation for the Tm3+-doped fiber laser. The SC output power from the ZBLAN fiber has been 7.8 W with a spectrum extending to approximately 4.1 μm. For further wavelength broadening experiments, a long-wave-pass filter with a 3 dB edge around 3.6 μm has been implemented between the ZBLAN and the AsSe fiber to cut out the residual pump light at 2 μm and the radiation between 2 μm and 3.5 μm. The pump power was approximately 120 mW with a spectrum from 3.5 μm to 3.9 μm. First proof of principal experiments has been performed with 20 mW of averaged output power and a spectrum extending to 4.9 μm. The coupling efficiency of the SC radiation from the ZBLAN fiber into the AsSe fiber has been around 30%. © 2016 SPIE.

We propose and demonstrate a new autolocking scheme using a three-mirror ring cavity consisting of a linear quadratic regulator and a time-varying Kalman filter. Our technique does not require a frequency scan to acquire resonance. We utilize the singular perturbation method to simplify our system dynamics and to permit the application of linear control techniques. The error signal combined with the transmitted power is used to estimate the cavity detuning. This estimate is used by a linear time-varying Kalman filter which enables the implementation of an optimal controller. The experimental results validate the controller design, and we demonstrate improved robustness to disturbances and a faster locking time than a traditional proportional-integral controller. More important, the time-varying Kalman filtering approach automatically reacquires lock for large detunings, where the error signal leaves its linear capture range, a feat which linear time-invariant controllers cannot achieve. © 2016 American Physical Society.

Macromolecular degeneration and biochemical changes in tissue can be quantified using rotating frame relaxometry in MRI. It has been shown in several studies that the rotating frame longitudinal relaxation rate constant (R1ρ) and the rotating frame transverse relaxation rate constant (R2ρ) are sensitive biomarkers of phenomena at the cellular level. In this comprehensive review, existing MRI methods for probing the biophysical mechanisms that affect the rotating frame relaxation rates of the tissue (i.e. R1ρ and R2ρ) are presented. Long acquisition times and high radiofrequency (RF) energy deposition into tissue during the process of spin-locking in rotating frame relaxometry are the major barriers to the establishment of these relaxation contrasts at high magnetic fields. Therefore, clinical applications of R1ρ and R2ρ MRI using on- or off-resonance RF excitation methods remain challenging. Accordingly, this review describes the theoretical and experimental approaches to the design of hard RF pulse cluster- and adiabatic RF pulse-based excitation schemes for accurate and precise measurements of R1ρ and R2ρ. The merits and drawbacks of different MRI acquisition strategies for quantitative relaxation rate measurement in the rotating frame regime are reviewed. In addition, this review summarizes current clinical applications of rotating frame MRI sequences. © 2016 John Wiley & Sons, Ltd.

A ductile damage model for sheet bulk metal forming processes and its efficient and accurate treatment in the context of the Finite Element Method is presented. The damage is introduced as a non-local field to overcome pathological mesh dependency. Since standard elements tend to show volumetric locking in the bulk forming process a mixed formulation is implemented in the commercial software simufact.forming to obtain better results. DFG/SFB/TR 73