154 results about "Scattering effect" patented technology

Disclosed in the present invention is a salient contour matching-based method for target measurement in a severe imaging environment. The method specifically comprises: (1) acquiring a binocular image of a target; (2) establishing a global-local joint constraint-based background light estimation model, and removing a scattering effect of a medium in an imaging environment to obtain a restored left eye image and a restored right eye image; (3) learning an original image, and on the basis of a residual between a network reconstructed image and the original image, obtaining target localization prediction maps of the left eye image and the right eye image; and (4) respectively extracting contour lines of the target in the left eye image and the right eye image, constructing feature matching descriptors of contour points, performing stereo matching on the two sets of contour lines by minimizing matching cost, and performing three-dimensional reconstruction on the contour lines in light of calibrated intrinsic and extrinsic parameters to complete the measurement of a key size. According to the present invention, the key sizes of different targets in a severe environment can be accurately measured, thereby providing an effective solution for the problem of measuring the sizes of targets in a severe environment.

The invention discloses a real haze image defogging method based on a haze degradation model. The method comprises the following steps: constructing a haze degradation model fusing multiple scattering effects and multiple image degradation factors; using the haze degradation model to construct a training data set including the clear image and the corresponding pseudo haze image; constructing a defogging network for a real haze scene; training the defogging network by adopting the training data set until a preset loss function is converged; and inputting a to-be-defogged image into the trained defogging network to obtain a defogging result. According to the haze degradation model constructed by the invention, the difference between a synthetic domain and a real domain is effectively relieved; a designed space-frequency hybrid module improves the adaptability of the model to complex degradation characteristics; the prior-guided feed-forward network fully excavates and fuses dark channel prior information, and the sensing and modeling capability of the model to the haze area is effectively enhanced.

The invention provides a visual detection method for processing defects of a groove on the surface of a workpiece, which is used for detecting the defects of a slot of a triangle of a circular knitting machine, a lightweight slot defect detection model CSGE-DETR of the triangle of the circular knitting machine is used in the method, the trunk of the model comprises a CGSE module, and the model further comprises an SOEP trunk network and a RepC3 module introducing wavelet convolution WTConv; the detection method comprises the following steps. The method comprises the steps of 1, image acquisition; 2, preprocessing the image; step 3, defect identification; the computer machine vision detection method is optimized for solving the problems that the defect size of the triangle of the circular knitting machine is small, the background is complex, and the imaging quality is reduced due to the optical scattering effect when the defect is captured.

The invention relates to the technical field of additive manufacturing, in particular to a photocuring printing scattering suppression method and system based on acousto-optic modulation. According to the method, in the photocuring printing process, an acousto-optic modulation device is used for generating a focused ultrasonic field in a printing material, specific refractive index distribution is formed in the material based on the photoelastic effect, and therefore a refractive index regulation and control area used for restraining and guiding scattered light propagation is constructed in a local space; therefore, the scattering effect is suppressed, and the forming precision and the structural fidelity are improved. The system comprises a photocuring device, a light source, a printing platform and an acousto-optic modulation device used for achieving the method, the acousto-optic modulation device is composed of an ultrasonic transducer and an acoustic lens, and the acousto-optic modulation device forms a focusing sound field under external excitation and works in cooperation with the light source. The method is suitable for photocuring printing of various high-scattering light-sensitive composite materials, comprises material systems containing particles, cells or components with remarkable refractive index difference, and has good material adaptability.

The invention relates to a method for determining the layer thickness of an at least partially transparent surface coating on the surface of a substrate, using a measuring device for emitting focused radiation. The invention is characterized in that the distance between the surface of the substrate and the measuring device for emitting focused radiation is changed by a relative movement between the measuring device and the substrate, wherein the image of the radiation is captured in different relative positions, wherein in the case of an image with a clear outline edge, focusing is inferred at the interface between the surface coating and the substrate and the current relative position is stored as the first position, and wherein in the case of an image surrounded by scattering effects, focusing is inferred at the interface between the surface coating and the air and the current relative position is stored as the second position, after which the difference between the first and second positions is used to determine theTaking into account the refractive index of the transparent surface coating, the layer thickness of the at least partially transparent surface coating is determined.

The application provides an optical system and a monitoring method for monitoring stimulated Brillouin scattering effect. The optical system for monitoring stimulated Brillouin scattering effect firstly delivers a narrow linewidth seed source into a laser amplifier through a first optical device to amplify the narrow linewidth laser, and guides stimulated Brillouin scattering light generated by the laser amplifier to a back light monitoring module to detect the back light power and spectral components of the stimulated Brillouin scattering light in real time through the back light monitoring module, so as to realize the purpose of simultaneously and accurately measuring the stimulated Brillouin scattering light power and observing the laser components, and is more conducive to judging whether the stimulated Brillouin scattering effect occurs. Further, the optical system can adjust the light splitting ratio of the first optical device and the back light monitoring module to protect the narrow linewidth seed source and the spectrometer in the back light monitoring module from the damage of the back light to the greatest extent, and achieve the purpose of accurately judging the stimulated Brillouin scattering effect and protecting the system safety.

The invention relates to a film coating device, a film and a preparation method of the film. The film coating device comprises a vacuum chamber, a first-stage rotating disc, a second-stage rotating disc and a film coating source, wherein the first-stage rotating disc, the second-stage rotating disc and the film coating source are located in the vacuum chamber; according to the preparation device system, through the arrangement of the first-stage rotating disc and the second-stage rotating disc, deposition during thin film evaporation has a certain periodic characteristic, so that the expected scattering effect is generated, and the thickness of the scattering thin film only needs several microns when the expected scattering degree is generated; in addition, through the arrangement of the film coating source, the thin film with the high scattering rate can be obtained, the hardness and adhesive force of the obtained thin film can be improved, and the quality of the thin film is improved.

The invention relates to the technical field of underwater imaging, provides a Fourier lamination underwater imaging system and method based on adaptive phase retrieval, and effectively solves the problem of insufficient imaging resolution caused by a strong scattering effect of a water body and aperture limitation of an optical system in a traditional underwater imaging technology. According to the method, the Fourier lamination imaging technology is applied to the underwater environment for the first time, and the spatial resolution is improved by 2.24 times compared with that of a traditional method in combination with the self-adaptive phase retrieval algorithm. Further experiments show that even under the strong scattering condition, the scheme can still keep the resolution performance obviously superior to that of a traditional method. The invention provides a novel underwater high-resolution imaging technical scheme, the imaging performance of marine resource exploration and underwater engineering facility detection can be remarkably improved, and the method has important application value.

The application discloses a deep ultraviolet light emitting diode with light scattering structure and a preparation method thereof. The light emitting diode comprises, in sequence along a wafer epitaxial growth direction, a substrate layer, a buffer layer and an N-type semiconductor transmission layer; wherein the N-type semiconductor transmission layer has an upper and lower part in shape, a multi-quantum well active layer, a P-type semiconductor transmission layer and a P-GaN contact layer are sequentially arranged on the surface of the upper part of the N-type semiconductor transmission layer; and a horizontal direction light scattering structure layer and a vertical direction light scattering structure are respectively arranged in the inner part of the upper and lower parts of the N-type semiconductor transmission layer. The application improves the scattering effect of light in the N-type semiconductor transmission layer, breaks the light waveguide effect of the N-type semiconductor transmission layer, effectively blocks the light propagation to the metal n electrode, simultaneously scatters the light, improves the bottom light extraction efficiency of the deep ultraviolet LED and improves the light extraction efficiency.

The present application relates to the technical field of medical image processing, and particularly relates to a CBCT data enhancement method and system based on anatomical region constraint and physical consistency; a human body region mask is acquired and a data enhancement model only exerting enhancement disturbance on the human body anatomical tissue region is constructed, a plurality of enhancement disturbances conforming to the CBCT imaging physical mechanism are combined, the CBCT data after enhancement is strictly limited to the anatomical range, non-physical disturbance introduced by the air region is avoided, and the CBCT data after enhancement is close to the real imaging degradation process; at least one enhancement disturbance including gray scale shift, Gamma nonlinear transformation, compound noise, low-frequency scattering field and stripe artifact is executed on the CBCT image after preprocessing, real imaging degradation factors such as device calibration error, detector nonlinear response, electronic noise, photon statistical noise, scattering effect and reconstruction artifact can be simulated, and the adaptability and robustness of the model to different devices, scanning parameters and patient individuals are significantly improved.

The embodiment of the invention discloses a display system, and the system comprises an optical fiber scanning array which comprises a plurality of optical fiber scanning units, the optical fiber scanning units are densely arranged in the transverse direction of the optical fiber scanning array, the number of the optical fiber scanning units arranged in the transverse direction is far greater than the number of the optical fiber scanning units arranged in the longitudinal direction, and the number of the optical fiber scanning units arranged in the longitudinal direction is greater than the number of the optical fiber scanning units arranged in the longitudinal direction. The included angle between the adjacent optical fiber scanning units in the transverse direction and the display center is related to the divergence angle of the emitted light. The directional scattering screen is configured to perform directional scattering in the longitudinal direction; light emitted by the optical fiber scanning array forms a display space range for imaging on the other side of the directional scattering screen through the directional scattering effect of the directional scattering screen.

The present application belongs to the field of automobile head-up display technology, and relates to a vehicle-mounted head-up display optical film with light scattering function and a preparation method thereof. The present application adopts a heat-sensitive shape memory idea, utilizes the light-sensitive characteristics and shape memory function of a light-heat effect type shape memory material, and sets a dynamic scattering layer scattering part. When the front sunlight is irradiated, the scattering part is raised, so that the sunlight is scattered to other directions through the scattering effect of light. Further, the scattering layer substrate is set as an encapsulated scattering solution. The shape memory material in the scattering solution is deformed and curled when irradiated by sunlight, absorbs and reflects part of the light, thereby further reducing the penetration of sunlight into the display film into the driver's line of sight. Moreover, reflective particles and light-absorbing particles are added in the scattering solution, further reducing the penetration of sunlight into the display film, thereby preventing or reducing sunlight from directly entering the driver's eyes from multiple aspects, and further improving the safety of driving.

The invention relates to high-fog and high-light-transmittance diffusion resin and a preparation method thereof, and belongs to the technical field of high polymer materials. A mixed system with certain refraction and scattering effects is formed by utilizing the incompatibility between polypropylene and polycarbonate, and the surface of talcum powder is coated with organic silicon and polypropylene chain segments, so that the nucleating effect of the talcum powder can be exerted, the transparency and mechanical strength of the material are improved, and the mechanical property of the material is improved. The compatibility of the talcum powder and a resin system can also be improved, the dispersion uniformity of the talcum powder is further improved, so that the light transmission uniformity and the mechanical property are improved, and the organic silicon layer and the polypropylene layer coated on the surface of the talcum powder can enable light to be refracted and penetrated for multiple times, so that the light dispersion effect and the dodging and light transmission effects are improved.

The invention provides a method for evaluating the influence of damage to a wave-absorbing coating of an aircraft on the low scattering performance of the wave-absorbing coating, and belongs to the field of material performance evaluation.The method comprises the steps that regional decomposition is conducted on the aircraft, the aircraft is divided into a plurality of regions according to parts, each region is further decomposed into a plurality of sub-regions, and therefore targeted analysis can be conducted on damage of different parts; the method comprises the following steps: pre-estimating the low scattering performance of an aircraft wave-absorbing coating before damage, and calculating the radiation sectional area of each region by establishing a radiometer radiation sectional area model, so as to determine the low scattering performance reference of an aircraft in an undamaged state; carrying out radiation calculation on the passive millimeter wave absorbing coating; implementing brightness temperature imaging simulation of the passive millimeter wave absorbing coating; the low scattering performance of the airplane wave-absorbing coating after damage is evaluated, the influence of damage on the low scattering performance is quantified through a low scattering effect concept, and a basis is provided for repair decision making.

According to the method, a surface gravity wave and inner interface wave velocity potential field is analyzed into a product form of a vertical characteristic item and a horizontal diffraction field, and dimensionality reduction solution of a three-dimensional wave problem is realized; a vertical characteristic function orthogonal system meeting free liquid level, seabed boundary and interface coupling conditions is constructed, horizontal diffraction potential is decomposed into an incident field, a local column and an adjacent column scattering effect, and a Bessel function addition theorem is applied to construct a closed linear equation set of a multi-column interference field; establishing an extended dispersion equation containing density spring layer parameters, and revealing a modulation rule of layered strength on complex wave propagation characteristics; and finally, through tensor product coupling of a vertical mode and a horizontal diffraction field, constructing a full-three-dimensional diffraction velocity potential analytical solution, synthesizing a cross-layer pressure field integral by adopting a domain decomposition technology, and establishing a multi-column array generalized wave excitation force forecasting model. According to the method, efficient analytical calculation of the wave load of the multi-column system in the layered fluid is innovatively achieved.

This application discloses a driving substrate and a display panel. The driving substrate includes a substrate, a first gate, a buffer layer, an active layer, a gate insulating layer, a second gate, an interlayer dielectric layer, a source, and a drain. The active layer includes a first active sublayer and a second active sublayer sequentially disposed on the buffer layer. The band gaps of the first and second active sublayers are different. Since the active layer includes a first active sublayer and a second active sublayer with different band gaps, the first and second active sublayers form a heterojunction. Due to the bending of the band gap at the heterojunction interface, a two-dimensional electron gas is formed at the contact interface between the first and second active layers. The two-dimensional electron gas is confined to move within a two-dimensional plane, thereby reducing the scattering effect of ionized impurity centers and thus exhibiting good transport properties, effectively improving the carrier mobility of the driving substrate.

This invention relates to the field of laser particle size analyzer technology, and more particularly to a method for measuring particle refractive index in a laser particle size analyzer. By modulating a solution containing particles of different concentrations as the measurement sample, and acquiring concentration measurement data sequences and scattered light intensity data sequences in real time, while dynamically adjusting the laser particle size analyzer parameters based on the real-time calculated signal-to-noise ratio and concentration variation coefficient, the method achieves the ability to acquire high-quality scattered light data under multiple concentration conditions. This effectively overcomes the data distortion problem that may occur in single-concentration measurements due to inter-particle complex scattering effects or weak signals. Through systematic concentration sequence design and real-time parameter optimization, a rich and reliable data foundation is provided for subsequent refractive index inversion, improving the accuracy and reliability of the measurement results. This method solves the technical problem that existing methods for determining particle refractive index mainly rely on experience, resulting in strong subjectivity and difficulty in guaranteeing accuracy.

Embodiments of this disclosure provide a method, apparatus, and storage medium for electron beam exposure correction. The method includes: determining a first dose distribution for electron beam exposure by performing electron beam proximity effect correction on a target pattern based on a predetermined dose distribution, the first dose distribution indicating a set of dose adjustment values ​​for compensating for scattering effects during electron beam exposure on the target pattern; determining a second dose distribution for electron beam exposure by performing electron beam haze effect correction on the target pattern based on the first dose distribution, the second dose distribution indicating a set of dose adjustment values ​​for compensating for haze effects during electron beam exposure on the target pattern; and determining a target dose distribution for electron beam exposure by performing electron beam proximity effect correction on the target pattern based on the first and second dose distributions.

A palm prosthesis suitable for infrared detection is characterized in that the palm prosthesis comprises a skin imitation body which has a scattering effect on infrared light; the vein imitation body is located in the skin imitation body; and the surface film layer is positioned on the surface of the skin imitation body and is provided with textures. According to the utility model, through imaging, a vein imaging effect close to a real palm can be realized, and the vein imaging effect of an optical system can be quantitatively evaluated.

The present application discloses a display panel and electronic device. The display panel includes: an array substrate; a display array disposed on the array substrate, the display array including a plurality of light-emitting elements; a microlens layer disposed on the side of the display array facing away from the array substrate, the microlens layer including a plurality of microlens structures for adjusting the light emission direction of the light-emitting elements; the microlens layer including: a first light-transmitting medium layer having a hollow region, the first light-transmitting medium layer being located on the side of the display array facing away from the array substrate; a second light-transmitting medium layer, the second light-transmitting medium layer filling the hollow region and covering the surface of the first light-transmitting medium layer facing away from the display array; and light-transmitting particles filled in the second light-transmitting medium layer, the refractive index of the light-transmitting particles being greater than the refractive index of the second light-transmitting medium layer. The present application's technical solution fills the second light-transmitting medium layer of the microlens layer with light-transmitting particles. The light-transmitting particles can further enhance the scattering effect of the second light-transmitting medium layer, thereby resolving the diffraction problem of the display panel.

The invention discloses an anti-dazzle semitransparent organic photovoltaic glass window based on thermal nanoimprint lithography and a preparation method of the anti-dazzle semitransparent organic photovoltaic glass window, and belongs to the technical field of photovoltaic building integration. A submicron grating structure is prepared on the surface of a ternary blending active layer through a thermal nanoimprint process, and a device structure with a metasurface light field regulation effect is formed after spin coating of an electron transport layer and evaporation of a metal top electrode. By introducing a grating structure and utilizing diffraction and scattering effects, energy of reflected light is redistributed to a non-mirror direction, zero-order mirror reflection is remarkably inhibited, glare is effectively inhibited, light pollution is reduced, and meanwhile, the polarization degree of the reflected light is reduced and the visual comfort is improved by differentially modulating S and P polarized light; for transmission light, the grating excites multi-order diffraction, resulting in angle dispersion of a light beam propagation path, increase of the optical path of light in the active layer, and enhancement of photon capture and absorption, thereby significantly improving the short-circuit current density and power conversion efficiency of the device while ensuring high light transmission.

The invention discloses a method for rapidly evaluating conventional nutritional ingredients of whole corn silage based on NIRS. The method comprises the following steps: S1, collecting and processing a whole corn silage sample; S2, determining the conventional nutritional ingredients; S3, collecting a near infrared spectrogram; according to the method disclosed by the invention, the calibration model of mathematical correlation between the near-infrared spectrogram characteristics and the conventional nutritional ingredient content is constructed, so that the rapid evaluation of the conventional nutritional ingredients of the whole corn silage new sample is realized, the detection capability is efficient, the multi-component synchronous analysis is realized, and the detection flux is remarkably improved; on the basis of the high penetration characteristic and scattering effect of near-infrared light, various physical state samples can be directly analyzed without sample pretreatment; the operation cost is low, the robustness is good, no reagent participates in the whole process, and pollution to the environment is avoided.

The invention relates to an underwater optical hybrid imaging method and device for a complex ocean scene, and the method comprises the steps: presetting any clean image as an undistorted image, simulating the light absorption and scattering effects of a plurality of water bodies at a preset water depth for the undistorted image based on a pre-constructed multi-stage attenuation underwater physical imaging model, and carrying out the simulation of the light absorption and scattering effects of the undistorted image; obtaining an initial underwater optical image; performing style adjustment considering color deviation on the initial underwater optical image by using a pre-trained underwater image detail migration model to obtain a final underwater optical image; wherein the underwater image detail migration model comprises a style generator and a style discriminator, and the style generator and the style discriminator perform cooperative training based on an adversarial learning strategy. Compared with the prior art, high-quality, self-adaptive and robust underwater optical imaging of a complex ocean scene is realized.

The invention relates to the technical field of power device design, in particular to a silicon carbide super-junction Schottky diode structure with alternating wide and narrow table tops and a preparation method thereof.The silicon carbide epitaxial layer of the diode is provided with a first conductive structure table top, and the first conductive structure table top comprises first table tops and second table tops which are arranged alternately; the table top width of the first table top is greater than that of the second table top; the doping concentration of the P-type doped region of the first table top is gradually reduced from the surface to the inside, and the P-type doping of the second table top forms uniform doping due to the scattering effect. A periodically changing table top width structure (wide table tops and narrow table tops are alternately arranged) is adopted, the wide table tops mainly bear a current conduction function and form a low-resistance main current channel, and the narrow table tops mainly optimize electric field distribution and charge balance, enhance a transverse depletion effect and improve the voltage endurance capability of the device; and secondly, the width ratio of the two mesas is adjustable, and the width-narrow mesa ratio is adjusted according to the application performance, so that the optimized forward conduction performance and reverse voltage endurance capability are obtained.

The invention relates to the technical field of liquid metal nuclear reactors, in particular to a method, a device and equipment for measuring the void fraction of the inner section of liquid metal. The method comprises the following steps: acquiring N ultrasonic coda wave signals of to-be-detected liquid metal; wherein the N ultrasonic coda wave signals are formed based on N ultrasonic pulse signals emitted into the liquid metal to be detected; on the basis of the N ultrasonic coda wave signals, the bubble characteristic tensor in the liquid metal to be detected is determined; and inputting the bubble feature tensor into a void fraction prediction model to obtain a section void fraction prediction value output by the void fraction prediction model. According to the method, the ultrasonic code wave signal can represent the collective scattering effect of the bubble group more completely and more meticulously, and the bubble feature tensor constructed based on the ultrasonic code wave signal contains the spatio-temporal feature information of the bubbles in the liquid metal, so that the accuracy of the obtained section void fraction can be improved.

The invention discloses a p-type copper doped antimony bismuth tellurium thermoelectric material, a preparation method, a module and a system, and belongs to the technical field of thermoelectric materials. The chemical formula of the material is Bi < 0.5 > Sb < 1.5 > Te < 3 > Cu < x >, wherein x is equal to 0.0025. A trace amount of copper element is accurately doped into a Bi0. 5Sb1. 5Te3 matrix, so that the carrier concentration is remarkably improved, the bipolar effect is inhibited, and meanwhile, the lattice thermal conductivity is effectively reduced by utilizing point defects and the phonon scattering effect of second-phase CuTe, so that collaborative optimization of electrical and thermal properties is realized. The average dimensionless thermoelectric figure of merit (ZT) of the material in a temperature zone of 30-100 DEG C is up to 1.46, which is superior to that of the existing commercial material. The preparation method combines vacuum melting, ball milling and spark plasma sintering (SPS) processes, and is simple and convenient in process and high in repeatability. And further high-pressure torsion (HPT) post-treatment can further refine the grains and reduce the heat conductivity. The material is particularly suitable for an energy recovery and self-energized monitoring system of converter valve low-temperature waste heat.

The invention discloses a thermosensitive intelligent device capable of regulating and controlling sunlight reflectivity in a large range and a preparation method of the thermosensitive intelligent device, and belongs to the field of intelligent materials and energy-saving buildings. The device is composed of an upper thermosensitive phase change layer and a lower sunlight reflecting layer. Wherein the lower layer takes polyvinylidene fluoride (PVDF) as a matrix, Al2O3 and SiO2 nanoparticles with two different sizes are doped, and a composite structure with a multi-stage scattering effect is formed through curing, so that the full-band sunlight reflecting capacity can be remarkably improved. And the upper layer is a reversible thermochromic interlayer formed by dissolving crystal violet lactone (CVL), bisphenol A and tetradecanol in a transparent substrate. The core mechanism is that at low temperature, the lower layer can serve as a light trap layer, light absorption of the upper layer is enhanced through multiple reflections, and the heating efficiency is improved; at high temperature, the upper layer becomes transparent, the overall reflectivity of the device is dominated by the lower layer, and efficient refrigeration is achieved. The device can regulate and control the sunlight reflectivity (greater than 60%) according to the environment temperature, and has a good application prospect in the field of energy conservation.

The application provides an EUV photoresist topography and roughness control method and device based on automatic parameter optimization, related products, and relates to extreme ultraviolet lithography technology and semiconductor manufacturing field. The method comprises constructing a random exposure model, simulating secondary electron random walk and scattering effect, and establishing a near neighbor condensation crosslinking mechanism based on lattice topological constraints; a discrete random development model is constructed based on the Gillese ratio algorithm, and the competitive reaction between the developing solution and the metal oxide core is simulated; the quantum yield, the electron blur length, and the number of development critical sites are used as optimization variables, a fitness function is constructed based on the three-dimensional topographic feature parameters of the photoresist, and the target parameter combination is calculated and output by an optimization algorithm. The application can realize fine control of photoresist topography and effective suppression of roughness, and improve the process window and manufacturing yield of extreme ultraviolet lithography.

This invention discloses a universal detection method applicable to coal with multiple particle sizes. It includes: first, acquiring a coal sample set under a target scenario, along with the corresponding near-infrared diffuse reflectance spectra and analytical properties of each coal sample, where all coal samples in the set have the same particle size; second, determining the property analysis model and reference wavelength based on the near-infrared diffuse reflectance spectra and analytical properties of each coal sample in the set; finally, acquiring the near-infrared diffuse reflectance spectrum of an unknown coal sample, preprocessing the spectrum using the reference wavelength to obtain the corresponding standardized spectrum, and inputting it into the property analysis model, which then outputs the analytical properties of the unknown coal sample. The method proposed in this invention is applicable to coal particle sizes ranging from ultrafine powder, medium particles, and coarse particles to in-situ rough surfaces and in-situ smooth surfaces, significantly eliminating spectral scattering effects caused by the physical state of the sample and improving the accuracy of quantitative coal quality analysis.