Showing papers by "National Physical Laboratory published in 2013"
TL;DR: The performance of the CS algorithm is further compared with various algorithms representative of the state of the art in the area and the optimal solutions obtained are mostly far better than the best solutions obtained by the existing methods.
Abstract: In this study, a new metaheuristic optimization algorithm, called cuckoo search (CS), is introduced for solving structural optimization tasks. The new CS algorithm in combination with Levy flights is first verified using a benchmark nonlinear constrained optimization problem. For the validation against structural engineering optimization problems, CS is subsequently applied to 13 design problems reported in the specialized literature. The performance of the CS algorithm is further compared with various algorithms representative of the state of the art in the area. The optimal solutions obtained by CS are mostly far better than the best solutions obtained by the existing methods. The unique search features used in CS and the implications for future research are finally discussed in detail.
1,701 citations
TL;DR: An overview of PAH properties, fates, transformations, human exposure, and health effects (acute and chronic) associated with their emission to the atmosphere is offered.
1,658 citations
TL;DR: A new metaheuristic optimization algorithm, called bat algorithm (BA), is used to solve constraint optimization tasks, and the optimal solutions obtained are found to be better than the best solutions provided by the existing methods.
Abstract: In this study, we use a new metaheuristic optimization algorithm, called bat algorithm (BA), to solve constraint optimization tasks. BA is verified using several classical benchmark constraint problems. For further validation, BA is applied to three benchmark constraint engineering problems reported in the specialized literature. The performance of the bat algorithm is compared with various existing algorithms. The optimal solutions obtained by BA are found to be better than the best solutions provided by the existing methods. Finally, the unique search features used in BA are analyzed, and their implications for future research are discussed in detail.
489 citations
Langley Research Center1, Goddard Space Flight Center2, Harvard University3, California Institute of Technology4, Imperial College London5, University of Wisconsin-Madison6, Lawrence Berkeley National Laboratory7, National Physical Laboratory8, University of Michigan9, McGill University10, University of Maryland, College Park11, University of Colorado Boulder12, National Oceanic and Atmospheric Administration13, National Institute of Standards and Technology14, University of Miami15
TL;DR: The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission as discussed by the authors provides a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change.
Abstract: The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Systeme Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5–50 μm), the spectrum of solar radiation reflected by the Earth and its atmosphere (320–2300 nm), and radio occultation refractivity from which...
244 citations
TL;DR: It is shown that blends comprising a small amount of semiconducting polymer mixed into an insulating polymer matrix actually perform very poorly in the undoped state, and that mobility and on/off ratio are improved dramatically upon moderate doping.
Abstract: Polymer transistors are being intensively developed for next-generation flexible electronics. Blends comprising a small amount of semiconducting polymer mixed into an insulating polymer matrix have simultaneously shown superior performance and environmental stability in organic field-effect transistors compared with the neat semiconductor. Here we show that such blends actually perform very poorly in the undoped state, and that mobility and on/off ratio are improved dramatically upon moderate doping. Structural investigations show that these blend layers feature nanometre-scale semiconductor domains and a vertical composition gradient. This particular morphology enables a quasi three-dimensional spatial distribution of semiconductor pathways within the insulating matrix, in which charge accumulation and depletion via a gate bias is substantially different from neat semiconductor, and where high on-current and low off-current are simultaneously realized in the stable doped state. Adding only 5 wt% of a semiconducting polymer to a polystyrene matrix, we realized an environmentally stable inverter with gain up to 60.
242 citations
TL;DR: Although fluctuations in annual temperature have indeed shown substantial geographical variation over the past few decades, the time-evolving standard deviation of globally averaged temperature anomalies has been stable, contradict the view that a warming world will automatically be one of more overall climatic variation.
Abstract: Evidence from Greenland ice cores shows that year-to-year temperature variability was probably higher in some past cold periods, but there is considerable interest in determining whether global warming is increasing climate variability at present. This interest is motivated by an understanding that increased variability and resulting extreme weather conditions may be more difficult for society to adapt to than altered mean conditions. So far, however, in spite of suggestions of increased variability, there is considerable uncertainty as to whether it is occurring. Here we show that although fluctuations in annual temperature have indeed shown substantial geographical variation over the past few decades, the time-evolving standard deviation of globally averaged temperature anomalies has been stable. A feature of the changes has been a tendency for many regions of low variability to experience increases, which might contribute to the perception of increased climate volatility. The normalization of temperature anomalies creates the impression of larger relative overall increases, but our use of absolute values, which we argue is a more appropriate approach, reveals little change. Regionally, greater year-to-year changes recently occurred in much of North America and Europe. Many climate models predict that total variability will ultimately decrease under high greenhouse gas concentrations, possibly associated with reductions in sea-ice cover. Our findings contradict the view that a warming world will automatically be one of more overall climatic variation.
216 citations
TL;DR: In this article, the surface potential (SP) of graphene is directly measured in Hall bar geometry via a combination of electrical functional microscopy and spectroscopy techniques, which enables calibrated work function measurements of graphene domains in ambient conditions with values Φ 1LG ~4.55 ± 0.02
Abstract: We compare the three most commonly used scanning probe techniques to obtain a reliable value of the work function in graphene domains of different thickness. The surface potential (SP) of graphene is directly measured in Hall bar geometry via a combination of electrical functional microscopy and spectroscopy techniques, which enables calibrated work function measurements of graphene domains in ambient conditions with values Φ1LG ~4.55 ± 0.02 eV and Φ2LG ~ 4.44 ± 0.02 eV for single- and bi-layer, respectively. We demonstrate that frequency-modulated Kelvin probe force microscopy (FM-KPFM) provides more accurate measurement of the SP than amplitude-modulated (AM)-KPFM. The discrepancy between experimental results obtained by different techniques is discussed. In addition, we use FM-KPFM for contactless measurements of the specific components of the device resistance. We show a strong non-Ohmic behavior of the electrode-graphene contact resistance and extract the graphene channel resistivity.
215 citations
TL;DR: The excellent performance of biosensor is attributed to large surface-to-volume ratio and good electrochemical activity of graphene oxide, and good biocompatibility of chitosan, which enhances the DNA immobilization and facilitate electron transfer between DNA and electrode surface (ITO).
Abstract: Graphene oxide (GO)-Chitosan (CHI) nano-composite is employed for the development of DNA based electrochemical biosensor for diagnosis of typhoid. Biosensor has been prepared by covalent immobilization of Salmonella typhi specific 5′-amine labeled single stranded (ss) DNA probe on GO-CHI/ITO via glutaraldehyde. Differential pulse voltammetry (DPV) studies revealed good specificity and ability of ssDNA/GO-CHI/ITO biosensor to distinguish complementary, non-complementary and one base mismatch sequences. The ssDNA/GO-CHI/ITO biosensor showed detection range of 10 fM to 50 nM and LOD 10 fM within 60 s hybridization times for complementary sequence. Further, ssDNA/GO-CHI/ITO bioelectrode is able to detect complementary target present in serum samples with LOD of 100 fM at 25 °C. The excellent performance of biosensor is attributed to large surface-to-volume ratio and good electrochemical activity of graphene oxide, and good biocompatibility of chitosan, which enhances the DNA immobilization and facilitate electron transfer between DNA and electrode surface (ITO).
185 citations
TL;DR: In this paper, the authors demonstrate a very high energy density and high-temperature stability capacitor based on SrTiO3-substituted BiFeO3 thin films with an energy density of 18.6 J/cm 3 at 972 kV/cm.
Abstract: In this work, we demonstrate a very high-energy density and high-temperature stability capacitor based on SrTiO3-substituted BiFeO3 thin films. An energy density of 18.6 J/cm 3 at 972 kV/cm is reported. The temperature coefficient of capacitance (TCC) was below 11% from room temperature up to 200°C. These results are of practical importance, because it puts forward a promising novel and environmentally friendly, lead-free material, for high-temperature applications in power electronics up to 200°C. Applications include capacitors for low carbon vehicles, renewable energy technologies, integrated circuits, and for the high-temperature aerospace sector.
175 citations
TL;DR: An atom chip is realized that enables the integration of laser cooling and trapping into a compact apparatus, and delivers ten thousand times more atoms than previous magneto-optical traps with microfabricated optics and can reach sub-Doppler temperatures.
Abstract: Laser-cooled atoms are central to modern precision measurements1,2,3,4,5,6. They are also increasingly important as an enabling technology for experimental cavity quantum electrodynamics7,8, quantum information processing9,10,11 and matter–wave interferometry12. Although significant progress has been made in miniaturizing atomic metrological devices13,14, these are limited in accuracy by their use of hot atomic ensembles and buffer gases. Advances have also been made in producing portable apparatus that benefits from the advantages of atoms in the microkelvin regime15,16. However, simplifying atomic cooling and loading using microfabrication technology has proved difficult17,18. In this Letter we address this problem, realizing an atom chip that enables the integration of laser cooling and trapping into a compact apparatus. Our source delivers ten thousand times more atoms than previous magneto-optical traps with microfabricated optics and, for the first time, can reach sub-Doppler temperatures. Moreover, the same chip design offers a simple way to form stable optical lattices. These features, combined with simplicity of fabrication and ease of operation, make these new traps a key advance in the development of cold-atom technology for high-accuracy, portable measurement devices. An atom chip that enables the integration of laser cooling and trapping is demonstrated.
159 citations
TL;DR: In this paper, the authors compare the performance of ZnO nanorod/poly(methyl methacrylate) (PMMA) and ZnNorod poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) devices, and show that despite an open-circuit voltage nearly three times lower the PEDOT-PSS device generates 150 times more power on an optimum load.
Abstract: Electromechanical energy harvesting converts mechanical energy from the environment, such as vibration or human activity, into electrical energy that can be used to power a low power electronic device. Nanostructured piezoelectric energy harvesting devices, often termed nanogenerators, have rapidly increased in measured output over recent years. With these improvements nanogenerators have the potential to compete with more traditional micro- or macroscopic energy harvesting devices based on piezoelectric ceramics such as lead zirconate titanate (PZT), polymers such as polyvinylidene fluoride (PVDF) or electrostatic, electret or electromagnetic kinetic energy harvesters. Power output from a nanogenerator is most commonly measured through open-circuit voltage and/or short-circuit current, where power may be estimated from the product of these values. Here we show that such measures do not provide a complete picture of the output of these devices, and can be misleading when attempting to compare alternative designs. In order to compare the power output from a nanogenerator, techniques must be improved in line with those used for more established technologies. We compare ZnO nanorod/poly(methyl methacrylate) (PMMA) and ZnO nanorod/poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) devices, and show that despite an open-circuit voltage nearly three times lower the ZnO/PEDOT:PSS device generates 150 times more power on an optimum load. In addition, it is shown that the peak voltage and current output can be increased by straining the device more rapidly and therefore time-averaged power, or time-integrated measures of output such as total energy or total charge should be calculated. Finally, the internal impedance of the devices is characterised to develop an understanding of their behaviour and shows a much higher internal resistance but lower capacitive impedance for the ZnO/PMMA device. It is hoped that by following more rigorous testing procedures the performance of nanostructured piezoelectric devices can be compared more realistically to other energy harvesting technologies and improvements can be rapidly driven by a more complete understanding of their behaviour.
TL;DR: The electrochemical sensing results of the anti-AFB1/RGO/ITO based immunoelectrode obtained as a function of aflatoxin concentration show high sensitivity and improved detection limit and the association constant for antigen-antibody interaction obtained as 5 × 10(-4) ng mL(-1) indicates high affinity of antibodies toward the antigen ( AFB1).
Abstract: Reduced graphene oxide (RGO) due to its excellent electrochemical properties and large surface area, has recently aroused much interest for electrochemical biosensing application. Here, the chemically active RGO has been synthesized and deposited onto an indium tin oxide (ITO) coated glass substrate by the electrophoretic deposition technique. This novel platform has been utilized for covalent attachment of the monoclonal antibodies of aflatoxin B1 (anti-AFB1) for food toxin (AFB1) detection. The electron microscopy, X-ray diffraction, and UV-visible studies reveal successful synthesis of reduced graphene oxide while the XPS and FTIR studies suggest its carboxylic functionalized nature. The electrochemical sensing results of the anti-AFB1/RGO/ITO based immunoelectrode obtained as a function of aflatoxin concentration show high sensitivity (68 μA ng−1 mL cm−2) and improved detection limit (0.12 ng mL−1). The association constant (ka) for antigen–antibody interaction obtained as 5 × 10−4 ng mL−1 indicates high affinity of antibodies toward the antigen (AFB1).
TL;DR: Significant room temperature coupling is demonstrated by monitoring changes in ferroelectric domain patterns induced by magnetic fields in a newly discovered room temperature multiferroic.
Abstract: Single-phase magnetoelectric multiferroics are ferroelectric materials that display some form of magnetism. In addition, magnetic and ferroelectric order parameters are not independent of one another. Thus, the application of either an electric or magnetic field simultaneously alters both the electrical dipole configuration and the magnetic state of the material. The technological possibilities that could arise from magnetoelectric multiferroics are considerable and a range of functional devices has already been envisioned. Realising these devices, however, requires coupling effects to be significant and to occur at room temperature. Although such characteristics can be created in piezoelectric-magnetostrictive composites, to date they have only been weakly evident in single-phase multiferroics. Here in a newly discovered room temperature multiferroic, we demonstrate significant room temperature coupling by monitoring changes in ferroelectric domain patterns induced by magnetic fields. An order of magnitude estimate of the effective coupling coefficient suggests a value of ~1 × 10(-7) sm(-1).
TL;DR: The variability of the global gamma index (γ) analysis in various commercial IMRT/VMAT QA systems and the impact of measurement with low resolution detector arrays on γ indicates that the detector array configuration and resolution have greater impact on the experimental calculation of γ due to under-sampling of the dose distribution, blurring effects, noise, or a combination.
TL;DR: The energy spectroscopy of emitted electrons indicates that at high magnetic field these electrons can be transported over several microns without inelastic electron-electron or electron-phonon scattering.
Abstract: We demonstrate the energy- and time-resolved detection of single-electron wave packets from a clock-controlled source transmitted through a high-energy quantum Hall edge channel. A quantum dot source is loaded with single electrons which are then emitted $\ensuremath{\sim}150\text{ }\text{ }\mathrm{meV}$ above the Fermi energy. The energy spectroscopy of emitted electrons indicates that at high magnetic field these electrons can be transported over several microns without inelastic electron-electron or electron-phonon scattering. Using a time-resolved spectroscopic technique, we deduce the wave packet size at picosecond resolution. We also show how this technique can be used to switch individual electrons into different electron waveguides (edge channels).
TL;DR: In this article, an analysis is made of the sputtering yields of materials for argon gas cluster ion beams used in SIMS and XPS as a function of the beam energy, E, and the cluster size, n.
Abstract: An analysis is made of the sputtering yields of materials for argon gas cluster ion beams used in SIMS and XPS as a function of the beam energy, E, and the cluster size, n. The analysis is based on the yield data for the elements Si and Au, the inorganic compound SiO2, and the organic materials Irganox 1010, the OLED HTM-1, poly(styrene), poly(carbonate), and poly(methyl methacrylate). The argon primary ions have cluster sizes, n, in the range 100–16 000 and beam energies, E, from 2.5 to 80 keV. It is found that the elemental and compound data expressed as the yields, Y, of atoms sputtered per primary ion may all be described by a simple universal equation: Y/n = (E/An)q/[1 + (E/An)q−1] where the parameters A and q are established by fitting. The sputtering yields of the three organic materials are given as yield volumes expressed in nm3. For these, an extra parameter B is included multiplying the right-hand side of the equation where B is found by fitting to be of the order (0.18 nm)3 to (0.26 nm)3. This...
TL;DR: This work presents the first implementation of mid-infrared dual-comb spectroscopy with an optical parametric oscillator, and opens up unique opportunities to perform broadband spectroscopic measurements with high resolution, high requisition rate, and high detection sensitivity.
Abstract: We present the first implementation of mid-infrared dual-comb spectroscopy with an optical parametric oscillator. Methane absorption spectroscopy was demonstrated with a resolution of 0.2 cm(-1) (5 GHz) at an acquisition time of ~10.4 ms over a spectral coverage at 2900-3050 cm(-1). The average power from each individual mid-infrared comb line was ~1 μW, representing a power level much greater than typical difference-frequency-generation sources. Mid-infrared dual-comb spectroscopy opens up unique opportunities to perform broadband spectroscopic measurements with high resolution, high requisition rate, and high detection sensitivity.
TL;DR: It is shown that pores formed by antimicrobial peptides in supported lipid bilayers are not necessarily limited to a particular diameter, nor they are transient, but can expand laterally at the nano-to-micrometer scale to the point of complete membrane disintegration.
Abstract: Antimicrobial peptides are postulated to disrupt microbial phospholipid membranes. The prevailing molecular model is based on the formation of stable or transient pores although the direct observation of the fundamental processes is lacking. By combining rational peptide design with topographical (atomic force microscopy) and chemical (nanoscale secondary ion mass spectrometry) imaging on the same samples, we show that pores formed by antimicrobial peptides in supported lipid bilayers are not necessarily limited to a particular diameter, nor they are transient, but can expand laterally at the nano-to-micrometer scale to the point of complete membrane disintegration. The results offer a mechanistic basis for membrane poration as a generic physicochemical process of cooperative and continuous peptide recruitment in the available phospholipid matrix.
TL;DR: In the last ten years extraordinary results in time and frequency metrology have been demonstrated as discussed by the authors, and the state-of-the-art in optical clock research has been established.
Abstract: In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femtosecond optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today’s best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in 1018. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.
TL;DR: A monolithic, fixed-barrier single-electron pump made entirely from graphene that performs at frequencies up to several gigahertz is presented, bringing an all-graphene closure of the quantum metrological triangle within reach.
Abstract: A single electron pump made entirely from graphene that performs at frequencies up to several gigahertz is now realized
TL;DR: In this paper, the authors describe extensive studies on a family of perovskite oxides that are ferroelectric and ferromagnetic at ambient temperatures, including x-ray diffraction and Raman spectroscopy.
Abstract: We describe extensive studies on a family of perovskite oxides that are ferroelectric and ferromagnetic at ambient temperatures. The data include x-ray diffraction, Raman spectroscopy, measurements of ferroelectric and magnetic hysteresis, dielectric constants, Curie temperatures, electron microscopy (both scanning electron microscope and transmission electron microscopy (TEM)) studies, and both longitudinal and transverse magnetoelectric constants α33 and α31. The study extends earlier work to lower Fe, Ta, and Nb concentrations at the B-site (from 15%–20% down to 5%). The magnetoelectric constants increase supralinearly with Fe concentrations, supporting the earlier conclusions of a key role for Fe spin clustering. The room-temperature orthorhombic C2v point group symmetry inferred from earlier x-ray diffraction studies is confirmed via TEM, and the primitive unit cell size is found to be the basic perovskite Z = 1 structure of BaTiO3, also the sequence of phase transitions with increasing temperature from rhombohedral to orthorhombic to tetragonal to cubic mimics barium titanate.
TL;DR: In this article, the Boltzmann constant kB was derived from measurements of the speed of sound in argon gas which can be related directly to the mean molecular kinetic energy.
Abstract: The Comite international des poids et mesures (CIPM) has projected a major revision of the International System of Units (SI) in which all of the base units will be defined by fixing the values of fundamental constants of nature. In preparation for this we have carried out a new, low-uncertainty determination of the Boltzmann constant, kB, in terms of which the SI unit of temperature, the kelvin, can be re-defined. We have evaluated kB from exceptionally accurate measurements of the speed of sound in argon gas which can be related directly to the mean molecular kinetic energy, . Our new estimate is kB = 1.380 651 56 (98) × 10−23 J K−1 with a relative standard uncertainty uR = 0.71 × 10−6.
TL;DR: Temperature plays a crucial role in controlling the magnetism as well as the defects in graphene and at 600 °C the self-repair mechanism helps the defects to mend but resulting in the decrement of magnetization and providing a good quality graphene with less defects.
Abstract: The existence of ferromagnetism in the wonder material graphene has opened up the path for many future spintronics and memory applications. But simultaneously it is very important to understand the variation of these properties with temperature in regards to the device applications. Here we observed defect induced ferromagnetism in chemically reduced graphene and the effect of temperature on it. Several theoretical studies have proved that the main cause of ferromagnetism in graphene is due to various defects. The observed results established that these defects can be mended by treating the samples at elevated temperatures but sacrificing the ferromagnetism simultaneously. Hence, temperature plays a crucial role in controlling the magnetism as well as the defects in graphene. In this study we revealed that at 600 °C the self-repair mechanism helps the defects to mend but resulting in the decrement of magnetization and providing a good quality graphene with less defects.
TL;DR: In this paper, a three dimensional, covalently-grafted graphene-polyaniline nanocomposites have been reported, where numerous nucleation sites are introduced by diazotization with p-aminobenzoic acid followed by amination using Schmidt reaction.
TL;DR: This review identifies and discusses the most important gaps of knowledge and future needs of action, e.g. more systematic nationwide monitoring for precursor and ozone formation over Indian region.
TL;DR: In this paper, a method for determining the lateral resolution of areal surface topography measuring instruments using a type ASP (star-shaped) material measure is presented. And the resolution of a phase shifting interferometer was determined based on the ISO definition of the lateral period limit.
Abstract: Calibration of the scales of areal surface topography measuring instruments requires testing of the resolution. Several designs of artefact that allow testing of the resolution of such instruments are currently available; however, analysis methods need to be developed to provide comparable results. A novel method for determining the lateral resolution of areal surface topography measuring instruments is presented. The method uses a type ASP (star-shaped) material measure. To demonstrate the validity of the method, the resolution of a phase shifting interferometer was determined based on the ISO definition of the lateral period limit. Using the proposed method, the type ASP material measure, which is often used to judge qualitatively an instrument's resolution, can be used to quantitatively estimate the resolution of instruments using the topography data.
TL;DR: The dose response ratios of the majority of the detectors agreed within the measurement uncertainty when irradiated with FF- and FFF-beams, and the microDiamond and the unshielded diodes would require only small corrections which make them suitable candidates for small field dosimetry in FF-
TL;DR: In this paper, the theory of optical transfer functions in 3D imaging is presented, with a focus on suitable methods for the establishment of calibration standards for 3D images and surface topography measurements.
Abstract: A significant number of areal surface topography measuring instruments, largely based on optical techniques, are commercially available. However,implementation of optical instrumentation into production is currently difficult dueto the lack of understanding of the complex interaction between the light and the component surface. Studying the optical transfer function of the instrument can help address this issue. Herea review is given of techniques for the measurement of optical transfer functions. Starting from the basis of a spatially coherent, monochromatic confocal scanning imaging system, the theory of optical transfer functions in three-dimensional (3D) imaging is presented. Further generalizations are reviewed allowing the extension of the theory to the description of conventional and interferometric 3D imaging systems. Polychromatic transfer functions and surface topography measurements are also discussed. Following presentation of theoretical results, experimental methods to measure the optical transfer function of each class of system are presented, with a focus on suitable methods for the establishment of calibration standards in 3D imaging and surface topography measurements.
01 Jan 2013
TL;DR: This chapter reviews some of the latest metaheuristics in design optimization, which have become increasingly popular in the last two decades.
Abstract: Design optimization in engineering tends to be very challenging, partly due to the complexity and high nonlinearity of the problem of interest and partly due to stringent design codes in engineering. Conventional algorithms are not the best tools for highly nonlinear global optimization, as they are local search algorithms and thus often miss the global optimality. In addition, design solutions have to be robust and subject to uncertainty in the parameters and tolerance of available components and materials. Metaheuristic algorithms have become increasingly popular in the last two decades. This chapter reviews some of the latest metaheuristics.