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Статті в журналах з теми "Local Density Shadow Wave Function"
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REATTO, L., and D. E. GALLI. "WHAT IS A ROTON?" International Journal of Modern Physics B 13, no. 05n06 (March 10, 1999): 607–16. http://dx.doi.org/10.1142/s0217979299000497.
Повний текст джерелаАнотація:
Many models of a roton in superfluid 4 He have been proposed over the years but no general consensus has been reached yet on the nature of such excitation. We present a number of new results relating to this question. We have developed an accurate representation of the wave function of such excitation which is based on a shadow function. This allows to treat the short range backflow effects in a non perturbative way. The theory gives results in quantitative agreement with experiment. Starting from such eigenstates of momentum we build wave–packets and study local quantities like density, momentum and vorticity. No model agrees with our results for the excitations in the roton minimum region because we find that the excitations have in a varying degree characters of single particle, of non quantized smoke ring and of collective excitation. We have also considered 4 He in two dimensions and we find similar results. In 2D we have studied also maxon and high frequency phonon wave–packets.
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REATTO, L., M. ROSSI, and D. E. GALLI. "BOSE–EINSTEIN CONDENSATION IN BULK AND CONFINED SOLID HELIUM." International Journal of Modern Physics B 20, no. 30n31 (December 20, 2006): 5081–92. http://dx.doi.org/10.1142/s0217979206036120.
Повний текст джерелаАнотація:
We address the question if the ground state of solid 4 He has the number of lattice sites equal to the number of atoms (commensurate state) or if it is different (incommensurate state). We point out that energy computation from simulation as performed by now cannot be used to decide this question and that the presently best variational wave function, a shadow wave function, gives an incommensurate state. We have extended the calculation of the one–body density matrix ρ1 to the exact Shadow Path Integral Ground State method. Calculation of ρ1 at ρ = 0.031 Å-3 shows that Vacancy–Interstitial pair processes are present also in the exact computation but the simulated system size is too small to infer the presence of off–diagonal long range order. Variational simulations of 4 He confined in a narrow cylindrical pore are also discussed.
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Nguyen-Truong, Hieu T., Tan-Tien Pham, Nam H. Vu, Dang H. Ngo, and Hung M. Le. "Energy-loss Function for Lead." Communications in Physics 27, no. 1 (May 17, 2017): 65. http://dx.doi.org/10.15625/0868-3166/27/1/9201.
Повний текст джерелаАнотація:
We study the energy-loss function for lead in the framework of the time-dependent density functional theory, using the full-potential linearized augmented plane-wave plus local orbitals method. The ab initio calculations are performed in the adiabatic local density approximation. The comparison between the obtained energy-loss function for zero momentum transfer with those from reflection electron energy loss spectroscopy measurements and from first-principles calculations shows good agreement.
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FALCÓN, CLAUDIO, and STÉPHAN FAUVE. "LOCAL DYNAMICS OF DEFECTS IN PARAMETRICALLY EXCITED WAVES." International Journal of Bifurcation and Chaos 19, no. 10 (October 2009): 3553–59. http://dx.doi.org/10.1142/s0218127409024992.
Повний текст джерелаАнотація:
We present an experimental study on the local dynamics of parametrically excited waves at an air–water interface when defects are present in the wave pattern. The probability density function (PDF) of the local wave amplitude displays an exponential part for values close to the average amplitude and decreases sharply to zero for large amplitudes. The power spectral density (PSD) of the local amplitude fluctuations shows a power-law behavior over one decade which we relate to a regime of defect-mediated turbulence.
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Onwuagba, B. N. "Localization of the 4f wave-function in cesium." Canadian Journal of Physics 74, no. 9-10 (September 1, 1996): 565–67. http://dx.doi.org/10.1139/p96-083.
Повний текст джерелаАнотація:
The local spin density approximation is used in the study of the localization of the 4f wave function in cesium, by superimposing the radial part of the kinetic-energy term on the self-consistent field potential VSCF(r). The results obtained show a collapsed 4f wave function in Cs+, but not in neutral Cs, which compares favourably with the previous findings and provide good insight into the understanding of the collapsed 4f wave function in cesium.
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Ran, Lingkun, and Shouting Gao. "A Three-Dimensional Wave-Activity Relation for Pseudomomentum." Journal of the Atmospheric Sciences 64, no. 6 (June 2007): 2126–34. http://dx.doi.org/10.1175/jas3931.1.
Повний текст джерелаАнотація:
A three-dimensional, nonhydrostatic local wave-activity relation for pseudomomentum is derived from the nonhydrostatic primitive equations in Cartesian coordinates by using an extension of the momentum–Casimir method. The stationary and zonally symmetric basic states are chosen and a Casimir function, which is the single-valued function of potential vorticity and potential temperature, is introduced in the derivation. The wave-activity density and wave-activity flux of the local wave-activity relation for pseudomomentum are expressed entirely in terms of Eulerian quantities so that they are easily calculated with atmospheric data and do not require the knowledge of particle placements. Constructed in the ageostrophic and nonhydrostatic dynamical framework, the local wave-activity relation for pseudomomentum is applicable to diagnosing the evolution and propagation of mesoscale weather systems.
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MODANESE, GIOVANNI. "LOCAL CONTRIBUTION OF A QUANTUM CONDENSATE TO THE VACUUM ENERGY DENSITY." Modern Physics Letters A 18, no. 10 (March 28, 2003): 683–90. http://dx.doi.org/10.1142/s0217732303009812.
Повний текст джерелаАнотація:
We evaluate the local contribution gμνL of coherent matter with Lagrangian density L to the vacuum energy density. Focusing on the case of superconductors obeying the Ginzburg–Landau equation, we express the relativistic invariant density L in terms of low-energy quantities containing the pairs density. We discuss under which physical conditions the sign of the local contribution of the collective wave function to the vacuum energy density is positive or negative. Effects of this kind can play an important role in bringing the local changes in the amplitude of gravitational vacuum fluctuations — a phenomenon reminiscent of the Casimir effect in QED.
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Mestel, L., and K. Subramanian. "Galactic Dynamos and Density Wave Theory." Symposium - International Astronomical Union 140 (1990): 135. http://dx.doi.org/10.1017/s0074180900189764.
Повний текст джерелаАнотація:
A steady density wave in the stellar background of a disk–like galaxy is supposed to force a spiral shock wave in the interstellar gas. The jump in vorticity across the shock leads to a locally enhanced helicity, and so to an α–effect which is steady but azimuth–dependent in the frame rotating with the angular velocity ω of the density wave. This is simulated by the adoption of the form for the local dynamo growth rate arising when the standard kinematic dynamo equation is treated by the thin–disk approximation (Ruzmaikin et al 1988). The global magnetic field is proportional to the function Q satisfying where η is the turbulent resistivity (for simplicity assumed uniform) and is the laminar angular velocity of the gas in the inertial frame. We look for solutions of the form where is a global eigen-value, and the non-vanishing of couples all odd or all the even m-values. Anticipating that the strong differential rotation will ensure that in the modes with the largest growth-rate the higher-m parts are weak, the equations are truncated, leaving just a pair in q1, q-1, to describe a basically bisymmetric (m = 1) mode. Approximate treatment by the WKBJ technique suggests that a corotating growing mode (with Γ real and positive) will differ significantly from zero over the range between the points where Numerical solutions have been found for a set of illustrative parameters with corotation occurring at 6.67 kpc, and the turbulence parameters close to those in the M51 mode studied by Ruzmaikin et al which extends over = 1 kpc. Three growing corotating modes were found, the fastest extending for ~ 3 kpc, the other two for over 4 kpc. The first two grow 2-3 times faster, the third somewhat slower, than the M51 mode.
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Naim, Carmelo, and Claudio Amovilli. "Extraction of a One-Particle Reduced Density Matrix from a Quantum Monte Carlo Electronic Density: A New Tool for Studying Nondynamic Correlation." Computation 9, no. 12 (December 9, 2021): 135. http://dx.doi.org/10.3390/computation9120135.
Повний текст джерелаАнотація:
In this work, we present a method to build a first order reduced density matrix (1-RDM) of a molecule from variational Quantum Monte Carlo (VMC) computations by means of a given correlated mapping wave function. Such a wave function is modeled on a Generalized Valence Bond plus Complete Active Space Configuration Interaction form and fits at best the density resulting from the Slater-Jastrow wave function of VMC. The accuracy of the method proposed has been proved by comparing the resulting kinetic energy with the corresponding VMC value. This 1-RDM is used to analyze the amount of correlation eventually captured in Kohn-Sham calculations performed in an unrestricted approach (UKS-DFT) and with different energy functionals. We performed test calculations on a selected set of molecules that show a significant multireference character. In this analysis, we compared both local and global indicators of nondynamic and dynamic correlation. Moreover, following the natural orbital decomposition of the 1-RDM, we also compared the effective temperatures of the corresponding Fermi-like distributions. Although there is a general agreement between UKS-DFT and VMC, we found the best match with the functional LC-BLYP.
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Gomes, André Severo Pereira, Christoph R. Jacob, and Lucas Visscher. "Calculation of local excitations in large systems by embedding wave-function theory in density-functional theory." Physical Chemistry Chemical Physics 10, no. 35 (2008): 5353. http://dx.doi.org/10.1039/b805739g.
Повний текст джерелаТези доповідей конференцій з теми "Local Density Shadow Wave Function"
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Feng, Qin, and Richard Large. "Prediction of Fatigue Life of Shallow Water Offshore Platforms Using Spectral Fatigue Analysis Method." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20796.
Повний текст джерелаАнотація:
Spectral fatigue analysis approach is highly recommended for fixed offshore platform design and reassessment by API. This method is a computationally efficient method, being able to handle the random nature of environmental ocean wave conditions during calculating wave loads on the offshore platforms and subsequent structural responses. However, its fundamental theory is based on the assumption of linearity of both structural system and wave loading mechanism. Although this method is critically appropriate to be applied in offshore platform design and fatigue assessment for deep water scenarios where wave and force nonlinearities are not very severe, it has still been widely utilized for the design and assessment of shallow water platforms in offshore industry without carefully considering possible errors caused by strong nonlinear factors between ocean waves and forces. The source giving rise to the errors is because of the difficulties in choosing suitably correct wave heights for a series of wave periods required for producing transfer functions between sea state spectra and structural response spectra. Therefore, the studies to justify the possible errors of the spectral fatigue analysis method for shallow water platforms have been provoked. This paper presents the results of the studies of investigating the errors from currently existing spectral fatigue analysis method. A new technical approach that can reduce the errors in the spectral fatigue analysis of shallow water platforms is introduced. The proposed technical approach is mainly focused on producing realistic transfer functions between sea state spectra and structural response spectra, which can reasonably reflect the individually local sea state data by using wave height-period joint probability density function. Hence the fatigue damage and life at the tubular joints of offshore platforms can be more precisely predicted. The spectral fatigue analysis of a practical shallow water jacket platform in the recent platform design project has been performed using the proposed approach and the results are discussed.
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Röpke, G. "Quartetting wave function approach to 20Ne: Shell model and local density approximation." In 6TH INTERNATIONAL CONFERENCE ON PRODUCTION, ENERGY AND RELIABILITY 2018: World Engineering Science & Technology Congress (ESTCON). Author(s), 2018. http://dx.doi.org/10.1063/1.5078827.
Повний текст джерела
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Manchu, Ge, Lou Yiping, and Yu Zhengti. "A Method for Transonic Inverse Cascade Design With a Stream Function Equation." In ASME 1986 International Gas Turbine Conference and Exhibit. American Society of Mechanical Engineers, 1986. http://dx.doi.org/10.1115/86-gt-189.
Повний текст джерелаАнотація:
A new profile design method is developed on the basis of Refs.1–3 for transonic flow. The rotational dynamic stream function equation, which is expressed in functional form of calculated coordinates, is deduced. This method can be used for the calculation of cascade and S1 stream surface of a transonic flow with local shock wave on the blade suction surface. This method consists of two parts. One is a inverse method with a given velocity distribution along the suction surface and a given thickness distribution. Another is a inverse method with given velocity distributions on suction and pressure surfaces. Using this method it is easy to get the blade profile with prescribed velocity and thickness distributions. The design of optimal profile may then be done with the calculated optimal velocity distribution on the blade surface. The rotational condition is satisfied when the stream function equation is adopted with the entropy term. If the compatibility condition can be fulfilled between the S1 and S2 equations. The iterative calculations of two kinds of stream surfaces of 3-D flow will be convergent. In this paper a unique value of density can be determined from the known stream function value. The computational programme is written with this method and several transonic examples have been calculated. These results are quite good.
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Singha, Angshuman, Puneet Agarwal, Wei Xu, Bharath R V, Saswata Mukhopadhyay, Brad Campbell, and Christopher Curtis. "Shape Optimization of Steel Lazy Wave Risers for Slugging Fatigue." In Offshore Technology Conference. OTC, 2022. http://dx.doi.org/10.4043/32022-ms.
Повний текст джерелаАнотація:
Abstract While Steel Lazy Wave Risers (SLWRs) are an attractive riser system from wave fatigue perspective in deep waters, it has recently been found that they can be susceptible to fatigue from slugging. Slugging may occur under certain combination of gas and liquid rates for multiphase (oil-gas-water) flow. For a given flow rate, the magnitude of slugging fatigue is a function of the SLWR shape, i.e., length and location of the hog bend that is created by the buoyancy modules, as well as the length of the lower catenary. The objective of this paper is to present a methodology to optimize the SLWR shape against slugging fatigue. The first step was to generate candidate riser shapes by varying key geometrical parameters for SLWR, which included the hang-off angle, length of the buoyancy, and the location of the buoyancy. For this purpose, an automated riser design tool was developed in the intelligent Deepwater Advanced Solutions Hub. This produced several hundred SLWR shapes. Static strength analysis and dynamic wave fatigue analysis were performed for all these shapes, and the shapes that passed both criteria were selected for slugging fatigue analysis. Slugging fatigue consists of first running the flow assurance software Olga which produced time series of mixture density at each riser node. This spatial and temporal density data was used to compute gravity loads due to slug flow (centrifugal and Coriolis forces were found to be negligible), which were fed into the OrcaFlex software as an external load. Time domain dynamic analysis was performed and results post- processed to compute fatigue as well as extract stress time series at key locations for detailed assessment and sense checks. All these steps were coded in a Python module with parallel running capability. This enabled running hundreds of cases in a few days. Slugging fatigue was combined with other sources of fatigue (wave, VIV, and installation) to select riser shapes that meet fatigue requirements. Results showed that the slugging fatigue can vary by up to a factor of 28 among various riser shapes for a given flow rate, demonstrating the value of shape optimization from slugging perspective. However, in scenarios involving sour service and production profiles with low flow rates causing severe slugging fatigue, even the optimized SLWR shape may require cladding or other solutions requiring further fatigue mitigation. It was found that a longer riser or a flatter arch gives higher slugging fatigue lives. Higher arch flatness alleviates long period slugging, which drives the slugging fatigue due to integral effect over the lower catenary, and increases fatigue life. Another interesting finding was that the shorter period slugging, which are due to local weight variations, provides an upper bound on slugging fatigue lives.
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Kasahara, Naoto, Nobuyuki Kimura, and Hideki Kamide. "Thermal Fatigue Evaluation Method Based on Power Spectrum Density Functions Against Fluid Temperature Fluctuation." In ASME 2005 Pressure Vessels and Piping Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/pvp2005-71307.
Повний текст джерелаАнотація:
Fluid temperature fluctuates at an incomplete mixing area of high and low temperature fluids in nuclear components. It induces random variations of local temperature gradients in structural walls, which lead to cyclic thermal stresses. When thermal stresses and cycle numbers are large, there are possibilities of fatigue crack initiations and propagations. It is recognized that there are attenuation factors depending on fluctuation frequency in the transfer process from fluid temperature to thermal stresses. If a frequency of fluctuation is very low, whole temperature of the wall can respond to fluid temperature, because thermal diffusivity homogenizes structural temperature. Therefore, low frequency fluctuations do not induce large thermal stress due to temperature gradients in structures. On the other hand, a wall surface cannot respond to very high frequency fluctuation, since a structure has a time constant of thermal response. High frequency fluctuations do not lead to large thermal stress. Paying attention to its attenuation mechanism, Japan Nuclear Cycle Development Institute (JNC) has proposed a fatigue evaluation method related to frequencies. The first step of this method is an evaluation of Power Spectrum Density (PSD) on fluid, from design specifications such as flow rates, diameters of pipes and materials. In the next step, the PSD of fluid is converted to PSD of thermal stress by the frequency transfer function. Finally, the PSD of thermal stress is transformed to time history of stress under an assumption of random phase. Fatigue damage factors can be evaluated from stress ranges and cycles obtained by the rain flow wave count method. Proposed method was applied to evaluate fatigue damage of piping junction model tests conducted at Oarai Engineering Center. Through comparison with direct evaluation from measurements and predictions by conventional methods, the accuracy of the proposed method was validated.
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Swillens, Abigail, Liesbeth Taelman, Joris Degroote, Jan Vierendeels, and Patrick Segers. "Assessing the Accuracy of Non-Invasive Measuring Methods of Pulse Wave Velocity: An Analysis Based on Fluid-Structure Interaction Simulations in the Carotid Artery." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80160.
Повний текст джерелаАнотація:
Pulse wave velocity (PWV) is the propagation speed of pressure and flow waves in the arterial system induced by the contracting left ventricle. PWV is a measure of arterial stiffness, and has been shown to predict cardiovascular events. In a clinical setting, PWV is usually associated with carotid-femoral PWV, reflecting the propagation speed over the aorta. It is, however, also possible to assess local PWV at a given measuring location, which reflects the stiffness of the artery under investigation at that particular location. When locally assessing PWV, single-location techniques are commonly used, which rely on the fact that in uniform elastic tubes, the relationship between a change in pressure (dP) and velocity (dU) is constant in the absence of wave reflections. As such, when plotting the pressure P as a function of the velocity U in an artery, a PU-loop is obtained, where reflection-free instants emerge as a straight line (typically during early systole), with a slope given by ρPWV (ρ = blood density). The original method relied on pressure and velocity data (PU-method), but alternative methods have been introduced based on cross-sectional area (A) and flow (Q) (QA-method), or diameter (D) and velocity (U) (ln(D)U-method).
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Mutsuda, Hidemi, and Yasuaki Doi. "Numerical Simulation of Dynamic Response of Structure Caused by Wave Impact Pressure Using an Eulerian Scheme With Lagrangian Particles." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79736.
Повний текст джерелаАнотація:
This study focuses on the development of computational techniques for computing fluid-structure interaction with wave breaking. This is of practical relevance in both ocean, and ship hydrodynamics. This paper also presents a prediction of the local highly pressure load impacting on a rigid and elastic structure caused by fluid force including impact pressure. We have developed a new numerical scheme that combines a Eulerian scheme with Lagrangian particles, i.e. free surface particles and SPH particles, to compute fluid-structure interaction caused by impact pressure. In this model, we employed two kinds of particles. One is free surface particle located near the free surface to capture air-water interface accurately. The other one is SPH particle to compute solid motion and elastic deformation. The air-water mixing flow is treated on a fixed Eulerian grid with the free surface particles to rebuild the density function for capturing the interface in filamentary regions that are under-resolved. Conversely, the structure is solved using the particle method, SPH. These Lagrangian particles are useful and available to capture the interface between different phases. In this paper, the proposed method was applied to the water entry problems of a V-shaped wedge, a horizontal flat-plate, a circular cylinder, an elastic cylindrical shell and impact pressure acting on an elastic wall caused by wave breaking. The free surface and elastic deformation are compared with both numerical and experimental results. The pressure and strain predictions are also compared with experimental results obtained by other researchers.
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Banik, A. K., and T. K. Datta. "Stochastic Response and Stability Analysis of Two-Point Mooring System." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49714.
Повний текст джерелаАнотація:
The stochastic response and stability of a two-point mooring system are investigated for random sea state represented by the P-M sea spectrum. The two point mooring system is modeled as a SDOF system having only stiffness nonlinearity; drag nonlinearity is represented by an equivalent linear damping. Since no parametric excitation exists and only the linear damping is assumed to be present in the system, only a local stability analysis is sufficient for the system. This is performed using a perturbation technique and the Infante’s method. The analysis requires the mean square response of the system, which may be obtained in various ways. In the present study, the method using van-der-Pol transformation and F-P-K equation is used to obtain the probability density function of the response under the random wave forces. From the moment of the probability density function, the mean square response is obtained. Stability of the system is represented by an inequality condition expressed as a function of some important parameters. A two point mooring system is analysed as an illustrative example for a water depth of 141.5 m and a sea state represented by PM spectrum with 16 m significant height. It is shown that for certain combinations of parameter values, stability of two point mooring system may not be achieved.
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Avouris, Phaedon. "STM Imaging of Electron Scattering and Confinement at Metal Surfaces." In Microphysics of Surfaces: Nanoscale Processing. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/msnp.1995.msaa3.
Повний текст джерелаАнотація:
Electrons in Shockley-type metal surface states act as a quasi-two-dimensional free-electron gas (2DFEG). We show that scanning tunneling microscopy (STM) and spectroscopy (STS) can be used to study the interactions of this 2DFEG with features such as individual steps and adsorbed or embedded atoms1,2. Two approaches were utilized in our studies. One is based on the fact that an incident surface electron-wave when partially reflected by localized potentials such as those produced by steps, can interfere with the incident wave. This interference leads to an oscillatory local density-of-states near the step. Such oscillations were observed in dI/dV maps of Au(111) and Ag(111) surfaces. From dI/dV images as a function of the bias voltage the dispersion of the surface states and the scattering phase-shifts were obtained. Point-defects lead to isotropic scattering which appears in the form of concentric circles surrounding the defect. Because of the finite penetration depth of the surface state, not only adsorbed but also ebbeded species were found to act as scatterers. The electron oscillations observed at 300K decay exponentially as a function of the distance from the scattercr. We attribute this to the temperature-dependent Δk-width of the STS measurement which leads to the dephasing of the thus formed wave-packet. Another approach we used to study the interactions of the 2DFEG involves the spectroscopy of the onset region of the surface state band as a function of the distance from the scatterer2. In this way, the range of strong perturbation of the surface state was estimated to be 15-20 Å, and evidence was found for defect-induced bulk-surface state mixing.