Geometrical Adjustment Research Articles

Integrative data processing for cyber-physical off-site and on-site construction promoting co-design

The term co-design describes a collaborative design process, usually across the boundaries of individual areas. A major aspect, and often an obstacle in the implementation of the co-design approach, is the establishment of a centralized data management system. In the past, the data management concept has been approached from different perspectives. Current approaches usually are oriented along the process chain and thus reflect a unidirectional flow of information. Neither the information feedback nor the reaction to adjustments in upstream model steps is supported, which makes continuous collaboration more difficult and at best reduces the co-design approach for continuous data usage. This paper addresses these weaknesses while outlining an integrative data processing concept enabling co-design between the domains of construction and industrial prefabrication.Geometrical information generated during architectural design and construction planning is reused for the production of components, manufacturing-related design adjustments are transferred back into the domain of construction. Changes throughout the entire process are centrally recorded. To ensure independence from the software tools used and to consider their great diversity, data exchange is largely based on standards, namely industry foundation classes and the standard for the exchange of product model data. In order to counteract the sequential processing according to a waterfall model and to support the co-design approach, the industrial prefabrication toolchain, consisting of computer-aided manufacturing software and downstream postprocessors, is largely automated, so that reprocessing of a workpiece for minor geometric adjustments no longer requires any interaction of the production planner.

Low-power latch comparator with accurate hysteresis control

Abstract Recent research has focused on finding ways to control hysteresis of dynamic comparators. The current proposed techniques are based on either geometrical dimension adjustment or digital control. The first case does not allow for post fabrication control, while the second has limited accuracy. This paper presents a new dynamic comparator design with external hysteresis adjustment using an analog voltage. This is achieved by proposing an architecture including control devices with a specific sizing. This is performed with no significant increase of the design complexity, keeping the power consumption as low as possible. The design is analyzed, showing that the proposed solution allows accurate hysteresis adjustment without affecting the inherent circuit properties. The dynamic comparator is also implemented using a 180 nm commercially available CMOS technology. The results show that a variation of 550 mV of the control voltage allows an accurate hysteresis adjustment ranging from 0 to 40 mV, according to the input conditions. Moreover, the simplicity of the circuit in conjunction with the use of dynamic technology have allowed the best performances to be achieved compared to the current state of the art, in terms of energy with an FoM equal to 116 fJ/decision and silicon area of 180 µm2 .

Novel multifunctional negative stiffness mechanical metamaterial structure: Tailored functions of multi-stable and compressive mono-stable

Negative stiffness (NS) mechanical metamaterials have excellent application prospect in a broad range of fields such as energy trapping, repeated energy absorption and so on. Although various kinds of NS mechanical metamaterials have been proposed, one configuration cannot simultaneously achieve multi-stability and mono-stability. This paper presented a novel multifunctional NS mechanical metamaterial structure, which possessed tailored functions of multi-stable and compressive mono-stable state without geometrical parameters adjustment. The novel multifunctional NS mechanical metamaterial structure with a conical shape consisted of both soft and hard material part and was fabricated by additive manufacturing technology. NS behaviors were achieved by the instability of the soft counterpart. Mechanical performance of this novel multifunctional NS mechanical metamaterial structure under axial compression was experimentally and numerically investigated. Influences of geometrical parameters tailoring stable state were systematically investigated and the ratio of offset distance, tilt angle, slenderness were found the key factors. Effective methods to make sure the tri-layer metamaterial structure achieving multi-stable after unloading from completely compacted state were proposed.

Estimating a mathematical formula of soil erosion under the effect of rainfall simulation by digital close range photogrammetry technique

A new design of soil erosion and rainfall simulator is presented at this study as an attempt to deduce a mathematical formula of soil surface erosion phenomenon to describe the behavior of the sandy soil under the rainfall simulation, soil deformation such gullies and surface eroding rills are monitored by the Digital Close Range Photogrammetry (DCRP) technique that includes capturing digital images with a smart cellphone camera, and a Terrestrial Laser Scanner (TLS) to digitalize the soil surface as a smart point cloud data to produce Digital Elevation Models (DEM) with accuracy reaches 0.10 mm 3D surface model. The results show that the mentioned methods give typical digital surface feature express especially of using geometrical adjustment that controls the orientation of the digital surface, the digital imaging feature detection technology achieves accurate results despite its small cost compared to the laser scanner that the cost of imaging equipment and software are used did not exceed 12% of TLS cost. Results of the statistical observations, a 3 order polynomial mathematical formula was generated through the digital photogrammetry method that describes the sandy soil behavior under the rainfall simulation as a relation between the eroding rate and the duration through the different slopes.

Convergent Evolution of Broadband Reflectors Underlies Metallic Coloration in Butterflies

Butterfly wings often display structural colors, which are the result of light reflection from chitinous nanostructures that adorn the wing scales. Amongst these structural colors are broadband metallic reflections, which have been previously linked to an ultrathin broadband reflector in the nymphalid butterfly Argyrophorus argenteus. To test if similar optical modes of broadband, specular reflectance have evolved in other butterfly taxa, we characterized the reflective scales of eight species from five Papilionoidea families using microspectrophotometry (MSP), light microscopy in reflected and transmitted modes, and scanning electron microscopy (SEM). In Nymphalidae, Pieridae, and Hesperidae, and Lycaenidae, we find that broadband specularity is due to spatial mixing of densely juxtaposed colorful reflectances that change across microscale distances (e.g. 1-3 µm). These seemingly convergent silver scales are unpigmented, show a continuous upper lamina with reduced windows, and consist of an air-cuticle sandwich of variable thickness, forming an undulatory thin-film. Strikingly, Hypochrysops apelles (Lycaenidae) show a novel mode of silver reflectance with spatial color mixing occurring across the entire proximo-distal length of the scale (>100 µm), transitioning from blue to red hues between the stem and the tip of the scales. Unlike the undulatory type, this reflector shows flat thin-films but this includes a multilayered lower lamina responsible for selective color iridescence in other lycaenids or in sunset moths. Finally, the gold scales of Anteros formosus (Riodinidae) show mixed reflectance in the green-to-red range, seemingly produced by a thin film in the lower lamina. Our comparative study suggests that evolution of metallic broadband reflectance repeatedly involved spatial color mixing and unperforated upper laminae, and is accomplished using at least three types of ultrastructural modifications. Undulatory thin-film systems, based on geometric adjustments of the transverse profile of the upper lamina and scale lumen, are widespread and may have evolved repeatedly from more generic colorless scale morphologies, while lycaenid and riodinid broadband reflectors may be elaborations of pre-existing iridescent states.

Harmonization of categorical maps by alignment processes and thematic consistency analysis

This paper describes an approach for harmonizing historical vector categorical maps with related modern maps. The approach aims at the correction of geometric distortions and semantic disagreements using alignment processes and analysis of thematic coherence. The harmonized version of the map produced by this approach can already be overlaid with other maps, what was unfeasible with the original map. The positional errors of the old map are reduced by two consecutive geometric adjustments, which use transformations usually available in most GIS software. The thematic consistency between the old and the modern map is achieved by harmonizing their classification systems and by the inclusion of specific contents missing in the early map, but represented in the modern map (e.g. small rivers). This approach was tested in the geometric and thematic harmonization of the Portuguese Land Cover/Land Use (LCLU) map for 1990 (COS90). In this test, the 1995 orthorectified aerial images and the 1995 LCLU map (COS95) were used as reference sources of higher positional accuracy, to align the COS90 map. COS90 was firstly adjusted with the 1995 aerial images by an NTV2 grid transformation, developed by the authors. Then, for reduction of the local distortions, the map resulting from the first transformation was aligned with the COS95 by a rubber-sheeting linear interpolation transformation. This geometric harmonization enabled a decrease of the Root Mean Square Error of COS90 from 204 meters to 13 meters. The thematic harmonization of COS90 enabled its comparison with modern related maps, and the integration of 201 river sections, that were missing because the specifications used in the production of the original map did not allow their representation.

Capacitive Silicon Modulator Design With V-Shaped SiO$_{2}$ Gate Waveguide to Optimize $V_{\pi }\times L$ and Bandwidth Trade-Off

This work presents a capacitive modulator design and modeling of a new waveguide architecture using silicon and poly-si technologies. We use a methodology involving the entire lumped-type modulator design process, from the optical design to the small-signal RF analysis. By means of geometric and physical parameters adjustments, the trade-offs among several figures of merit are analyzed in this paper. Due to the waveguide configuration, it is shown that the modulator can improve the trade-off between $V_{\pi }$ and bandwidth compared to the state-of-the-art for this kind of device. For instance, the best combinations are $V_{\pi }\simeq$ 1 V @ 20.4 GHz and $V_{\pi }$ = 5.7 V @ $\sim$ 31 GHz, with equivalent optical losses of 3 dB and 1.1 dB, respectively.

Simplified geometrical adjustment of bioimpedance measured data to the complex plane with just three parameters

When measurements are made in the field of electrical bioimpedance spectroscopy (EBIS), it is common to fit the raw data to the Cole model. In theory, EBIS data graphed in the impedance locus (resistance -R-on the x axis or abscissa versus reactance -Xc-on the y axis or ordinate) is expected to form an arch of a circle with its center lying below the resistance axis. The fitting process is most commonly made using least square (LS) techniques to obtain the four parameters involved in the Cole model: resistance at zero frequency (R0), resistance at infinite frequency (R∞), a time constant (τ) and a dimensionless exponent (α). In this article, the use of a geometrical approach to fit raw data to the expected arch is explored, where only three parameters are needed: the coordinates of the center in the Cartesian plane (named here as h for the abscissa, and k for the ordinate) and the length of the radius (r). These three parameters are obtained from the R and Xc values at three different frequencies. Data published in other literature was used to explain this approach, which is very simple and straightforward to use, while our own data was used to illustrate the performance of the method which, however, still needs thorough validation.

Design and Validation of an Articulated Sensor Carrier to Improve the Automatic Pipeline Inspection.

Pipeline inspection gauges (PIGs) carry out automatic pipeline inspection with nondestructive testing (NDT) technologies like ultrasound, magnetic flux leakage, and eddy current. The ultrasonic straight beam allows technicians to determine the wall thickness of the pipeline through the time of flight diffraction (TOFD), providing the pipeline reconstruction and allowing the detection of several defects like dents or corrosion. If the pipeline is of a long distance, then the inspection process is automatic, and the fluid pressure pushes the PIG through the pipeline system. In this case, the PIG velocity and its axial alignment with the pipeline cannot be controlled. The PIG geometry, the pipeline deformations, and the girth welds cause a continuous chattering when the PIG is running, removing the transducers perpendicularity with the inspection points, which means that some echoes cannot be received. To reduce this problem, we propose a novel method to design a sensor carrier that takes into account the angularity and distance effects to acquire the straight beam echoes. The main advantage of our sensor carrier is that it can be used in concave and convex pipeline sections through geometric adjustments, which ensure that it is in contact with the inner pipe wall. Our improvement of the method is the characterization of the misalignment between the internal wall of the pipeline and the transducer. Later, we analyzed the conditions of the automatic pipeline inspection, the existing recommendations in state-of-the-art technology, and the different mechanical scenarios that may occur. For the mechanical design, we developed all the equations and rules. At the signal processing level, we set a fixed gain in the filtering step to obtain the echoes in a defined distance range without saturating the acquisition channels. For the validation, we compared through the mean squared error (MSE) our sensor carrier in a straight pipe section and a pipe elbow of steel versus other sensor carrier configurations. Finally, we present the design parameters for the development of the sensor carrier for different pipeline diameters.

Diseño y desarrollo de patrones de la forma de una tenso-estructura

Aiming to create a methodology for geometric adjustments of minimum surfaces, the paper proposes a method that starts with the systematization of steps carried out in a virtual program, to create then scaled and real size physical models of tense structures made of canvas or textile material with the purpose of generating a range of unique designs of said models. The difficult adaptation of the form helps to create pattern designing, since the pattern is subject to the constructive measures of the material; based on this method, geometric adjustments will be generated and modular patter designs will be formed. The method can be synthesized by means of a specialized software called Win Tess that helps to create the analysis and design of this type of structures. For this experimental research, several types of complex models were developed in order to become familiar with the singular form of a double-curved canopy. Consequently, a practical application for the constructive design of a tense structure was achieved.

TGMin: A global-minimum structure search program based on a constrained basin-hopping algorithm

In this article, we introduce Tsinghua Global Minimum (TGMin) as a new program for the global minimum searching of geometric structures of gas-phase or surface-supported atomic clusters, and the constrained basin-hopping (BH) algorithm implemented in this program. To improve the efficiency of the BH algorithm, several types of constraints are introduced to reduce the vast search space, including constraints on the random displacement step size, displacement of low-coordination atoms, and geometrical structure adjustment after displacement. The ultrafast shape-recognition (USR) algorithm and its variants are implemented to identify duplicate structures during the global minimum search. In addition to the Metropolis acceptance criterion, we also implemented a morphology-based constraint that confines the global minimum search to a specific type of morphology, such as planar or non-planar structures, which offers a strict divide-and-conquer strategy for the BH algorithm. These improvements are implemented in the TGMin program, which was developed over the past decade and has been used in a number of publications. We tested our TGMin program on global minimum structural searches for a number of metal and main-group clusters including C60, Au20 and B20 clusters. Over the past five years, the TGMin program has been used to determine the global minimum structures of a series of boron atomic clusters (such as [B26]–, [B28]–, [B30]–, [B35]–, [B36]–, [B39]–, [B40]–, [MnB16]–, [CoB18]–, [RhB18]–, and [TaB20]–), metal-containing clusters Li n (n = 3–20), Au9(CO)8 + and [Cr6O19]2–, and the oxide-supported metal catalyst Au7/γ-Al2O3, as well as other isolated and surface-supported atomic clusters. In this article we present the major features of TGMin program and show that it is highly efficient at searching for global-minimum structures of atomic clusters in the gas phase and on various surface supports.

Lower extremity EMG-driven modeling of walking with automated adjustment of musculoskeletal geometry.

Neuromusculoskeletal disorders affecting walking ability are often difficult to manage, in part due to limited understanding of how a patient’s lower extremity muscle excitations contribute to the patient’s lower extremity joint moments. To assist in the study of these disorders, researchers have developed electromyography (EMG) driven neuromusculoskeletal models utilizing scaled generic musculoskeletal geometry. While these models can predict individual muscle contributions to lower extremity joint moments during walking, the accuracy of the predictions can be hindered by errors in the scaled geometry. This study presents a novel EMG-driven modeling method that automatically adjusts surrogate representations of the patient’s musculoskeletal geometry to improve prediction of lower extremity joint moments during walking. In addition to commonly adjusted neuromusculoskeletal model parameters, the proposed method adjusts model parameters defining muscle-tendon lengths, velocities, and moment arms. We evaluated our EMG-driven modeling method using data collected from a high-functioning hemiparetic subject walking on an instrumented treadmill at speeds ranging from 0.4 to 0.8 m/s. EMG-driven model parameter values were calibrated to match inverse dynamic moments for five degrees of freedom in each leg while keeping musculoskeletal geometry close to that of an initial scaled musculoskeletal model. We found that our EMG-driven modeling method incorporating automated adjustment of musculoskeletal geometry predicted net joint moments during walking more accurately than did the same method without geometric adjustments. Geometric adjustments improved moment prediction errors by 25% on average and up to 52%, with the largest improvements occurring at the hip. Predicted adjustments to musculoskeletal geometry were comparable to errors reported in the literature between scaled generic geometric models and measurements made from imaging data. Our results demonstrate that with appropriate experimental data, joint moment predictions for walking generated by an EMG-driven model can be improved significantly when automated adjustment of musculoskeletal geometry is included in the model calibration process.

The power transmission stability and efficiency of V-belts

The V-belt drive is a rather popular, widely used form of power transmission in agricultural and food industry engineering. At the same time, its stability, the lifetime of V-belt is influenced by several environmental factors, namely in the food industry by the contamination affecting the belt sides, the ambient temperature, humidity and the occasionally aggressive (acidic, alkaline air, air saturated with gases, etc.) medium. In the case of agricultural machinery, the vibration caused by uncertainly oriented pulleys with bearing in different plate structures (often being shaken in the fields) as well as alignment adjustment inaccuracies jeopardize the reliability of the parameters of the drive. Furthermore, the efficiency is determined by several factors together: the slippage occurring during drive transmission, the hysteresis loss resulting from the external and internal friction occurring with the belt entering and exiting the pulley. Experimental equipment and calculation methods were developed to determine the dynamics of temperature increase generated by the belt and pulley relationship. The temperature generated in the V-belt was measured as a function of pretension, pulley diameter and bending frequency. The so-called damping factor characterizing the contact with the pulley (the external friction when entering and exiting the groove) and the hysteresis loss (inner friction) are also determined. On the basis of the damping factor (ζ ≈ 400 Ns/m2) of the V-belt involved in the experiments the other losses (Poth) occurring from the pulley—V-belt contact and internal friction may be estimated. The drive parameters may be optimized with the mathematical model describing the effect of the pulley diameter and belt frequency on the increase in temperature. A standardized calculation method as well as design factors valid for the properly adjusted drive and normal operating conditions determined through empirical and laboratory experiments are used for the sizing of V-belt drives. The lifetime of V-belt drives designed in this way, used in extreme conditions typical of agricultural machinery will not be appropriate and will not provide clear, predictable information for maintenance planning. In such cases the results of our own many lifetime tests conducted in the given circumstances can be safely relied on. The agricultural harvesting machines are large plate-body self-propelled structures on which most of the power supply of the (threshing, cleaning, moving, etc.) machine units handling the crop is realized via belt drives. The distance and angular displacement of the axes involved in the drive can vary within wide limits. The misalignment and angular displacement of the pulleys can be the result of installation instability — due to the plate structure — and the deformation of the plate structure occurring during the operation as well. V-belt drives operate satisfactorily under such conditions as well, however these faults are unfavourable in terms of belt lifetime and result in the reduction of drive efficiency. A further aim of our research is to examine through experiments the lifetime and efficiency of V-belts used in agricultural machines as a function of drive adjustment errors. According to the results of the measurements of the geometrical adjustment errors of V-belt drives performed in the field, the pulleys of agricultural equipment are not always positioned in the medium plane of the drive. In our experiments these data served as independent variables. Figure 1 shows the arrangement of a V-belt drive in a grain harvester with the laser pulley alignment measuring instrument installed as an accessory. In the case of many machine types in 80% of the tested drives three times the permissible error was measured, and because of off-road use, due to dynamic load these errors further increased as a result of the frame deformation. The results of both the belt bending testing and the geometrical adjustment testing of the drive offer great help in the design of belt drives. At the same time they can be the source of lifetime and efficiency forecasts.

Importance of the variable periodontal ligament geometry for whole tooth mechanical function: A validated numerical study

When mammalian teeth breakdown food, several juxtaposed dental tissues work mechanically together, while balancing requirements of food comminution and avoiding damage to the oral tissues. One important way to achieve this is by channeling mastication forces into the surrounding jaw bone through a thin and compliant soft tissue, the periodontal ligament (PDL). As a result, during a typical chewing stroke, each tooth moves quite substantially in its anchor-site. Here we report a series of experiments, where we study the reaction of three-rooted teeth to a single chewing event by finite element (FE) modelling. The nonlinear behaviour of the PDL is simulated by a hyperelastic material model and the in silico results are validated by our own in vitro experiments. We examine the displacement response of the complete tooth-PDL-bone complex to increasing chewing loads. We observe that small spatially-varying geometric adjustments to the thickness of the PDL lead to strong changes in observed tooth reaction movement, as well as PDL strain and bone stress. When reproducing the regionally varying thickness of the PDL observed in vivo, FE simulations reveal subtle but significant tooth motion that leads to an even distribution of the stresses in the jaw bone, and to lower strains in the PDL. Our in silico experiments also reproduce the results of experiments performed by others on different animal models and are therefore useful for overcoming the difficulties of obtaining tooth-PDL-bone loading estimates in vivo. This data thus enhances our understanding of the role the variable PDL geometry plays in the tooth-PDL-bone complex during mastication.

Structure of solvation water around the active and inactive regions of a type III antifreeze protein and its mutants of lowered activity.

Water molecules from the solvation shell of the ice-binding surface are considered important for the antifreeze proteins to perform their function properly. Herein, we discuss the problem whether the extent of changes of the mean properties of solvation water can be connected with the antifreeze activity of the protein. To this aim, the structure of solvation water of a type III antifreeze protein from Macrozoarces americanus (eel pout) is investigated. A wild type of the protein is used, along with its three mutants, with antifreeze activities equal to 54% or 10% of the activity of the native form. The solvation water of the ice-binding surface and the rest of the protein are analyzed separately. To characterize the structure of solvation shell, parameters describing radial and angular characteristics of the mutual arrangement of the molecules were employed. They take into account short-distance (first hydration shell) or long-distance (two solvation shells) effects. The obtained results and the comparison with the results obtained previously for a hyperactive antifreeze protein from Choristoneura fumiferana lead to the conclusion that the structure and amino acid composition of the active region of the protein evolved to achieve two goals. The first one is the modification of the properties of the solvation water. The second one is the geometrical adjustment of the protein surface to the specific crystallographic plane of ice. Both of these goals have to be achieved simultaneously in order for the protein to perform its function properly. However, they seem to be independent from one another in a sense that very small antifreeze activity does not imply that properties of water become different from the ones observed for the wild type. The proteins with significantly lower activity still modify the mean properties of solvation water in a right direction, in spite of the fact that the accuracy of the geometrical match with the ice lattice is lost because of the mutations. Therefore, we do not observe any correlation between the antifreeze activity and the extent of modification of the properties of solvation water.

Analysis of the mass balance time series of glaciers in the Italian Alps

Abstract. This work presents an analysis of the mass balance series of nine Italian glaciers, which were selected based on the length, continuity and reliability of observations. All glaciers experienced mass loss in the observation period, which is variable for the different glaciers and ranges between 10 and 47 years. The longest series display increasing mass loss rates, which were mainly due to increased ablation during longer and warmer ablation seasons. The mean annual mass balance (Ba) in the decade from 2004 to 2013 ranged from −1788 to −763 mm w.e. yr−1. Low-altitude glaciers with low range of elevation are more out of balance than the higher, larger and steeper glaciers, which maintain residual accumulation areas in their upper reaches. The response of glaciers is mainly controlled by the combination of October–May precipitations and June–September temperatures, but rapid geometric adjustments and atmospheric changes lead to modifications in their response to climatic variations. In particular, a decreasing correlation of Ba with the June–September temperatures and an increasing correlation with October–May precipitations are observed for some glaciers. In addition, the October–May temperatures tend to become significantly correlated with Ba, possibly indicating a decrease in the fraction of solid precipitation, and/or increased ablation, during the accumulation season. Because most of the monitored glaciers have no more accumulation area, their observations series are at risk due to their impending extinction, thus requiring a replacement soon.

A Measurement Study of BLE iBeacon and Geometric Adjustment Scheme for Indoor Location-Based Mobile Applications

Bluetooth Low Energy (BLE) and the iBeacons have recently gained large interest for enabling various proximity-based application services. Given the ubiquitously deployed nature of Bluetooth devices including mobile smartphones, using BLE and iBeacon technologies seemed to be a promising future to come. This work started off with the belief that this was true: iBeacons could provide us with the accuracy in proximity and distance estimation to enable and simplify the development of many previously difficult applications. However, our empirical studies with three different iBeacon devices from various vendors and two types of smartphone platforms prove that this is not the case. Signal strength readings vary significantly over different iBeacon vendors, mobile platforms, environmental or deployment factors, and usage scenarios. This variability in signal strength naturally complicates the process of extracting an accurate location/proximity estimation in real environments. Our lessons on the limitations of iBeacon technique lead us to design a simple class attendance checking application by performing a simple form of geometric adjustments to compensate for the natural variations in beacon signal strength readings. We believe that the negative observations made in this work can provide future researchers with a reference on how well of a performance to expect from iBeacon devices as they enter their system design phases.

Non-conforming curved finite element schemes for time-dependent elastic–acoustic coupled problems

High-order numerical methods for solving time-dependent acoustic-elastic coupled problems are introduced. These methods, based on Finite Element techniques, allow for a flexible coupling between the fluid and the solid domain by using non-conforming meshes and curved elements.Since characteristic waves travel at different speeds through different media, specific levels of granularity for the mesh discretization are required on each domain, making impractical a possible conforming coupling in between. Advantageously, physical domains may be independently discretized in our framework due to the non-conforming feature. Consequently, an important increase in computational efficiency may be achieved compared to other implementations based on conforming techniques, namely by reducing the total number of degrees of freedom. Differently from other non-conforming approaches proposed so far, our technique is relatively simpler and requires only a geometrical adjustment at the coupling interface at a preprocessing stage, so that no extra computations are necessary during the time evolution of the simulation.On the other hand, as an advantage of using curvilinear elements, the geometry of the coupling interface between the two media of interest is faithfully represented up to the order of the scheme used. In other words, higher order schemes are in consonance with higher order approximations of the geometry. Concerning the time discretization, we analyze both explicit and implicit schemes. These schemes are energy conserving and, for the explicit case, the stability is guaranteed by a CFL condition.In order to illustrate the accuracy and convergence of these methods, a set of representative numerical tests are presented.

Measurement of methane concentration with cryptophane E infiltrated photonic crystal microcavity

A miniaturized, high-sensitive, and high-precision gas sensor for the measurement of methane concentration was realized in a cryptophane E infiltrated photonic crystal (PC) microcavity, by combing selective adsorption property of cryptophane E to methane and excellent resonant property of PC microcavity. The concentration variation of methane would change the refractive index (RI) of cryptophane E that infiltrated in defected holes of PC microcavity, and then induce a shift in resonant wavelength, allowing precision measurement of methane concentration. Simulation results of PC microcavity showed that the RI sensitivity of 363.8nm/RIU, quality factor of 12,923, and transmission of 0.9122 could be obtained by increasing the radii of defected holes, which does not require sophisticate geometrical adjustment and high-precision requirement for fabrication. However, its resonant property is comparable to other subtle-tuned PC microcavities. Besides, the designed methane sensor is only in response to methane, which can prevent the interrupt of other gases and enhance the measurement accuracy. Benefiting from the high RI sensitivity and high quality factor of the microcavity, a theoretical detection limit of 697.35ppm for methane sensing can be achieved.

Mapping Forest Degradation due to Selective Logging by Means of Time Series Analysis: Case Studies in Central Africa

Detecting and monitoring forest degradation in the tropics has implications for various fields of interest (biodiversity, emission calculations, self-sustenance of indigenous communities, timber exploitation). However, remote-sensing-based detection of forest degradation is difficult, as these subtle degradation signals are not easy to detect in the first place and quickly lost over time due to fast re-vegetation. To overcome these shortcomings, a time series analysis has been developed to map and monitor forest degradation over a longer period of time, with frequent updates based on Landsat data. This time series approach helps to reduce both the commission and the omission errors compared to, e.g., bi- or tri-temporal assessments. The approach involves a series of pre-processing steps, such as geometric and radiometric adjustments, followed by spectral mixture analysis and classification of spectral curves. The resulting pixel-based classification is then aggregated to degradation areas. The method was developed on a study site in Cameroon and applied to a second site in Central African Republic. For both areas, the results were finally evaluated against visual interpretation of very high-resolution optical imagery. Results show overall accuracies in both study sites above 85% for mapping degradation areas with the presented methods.