Accurate Transition Research Articles

Study on the optical properties for the F-type color center in BeO crystal with first-principles

In this paper, we calculated the defect formation energy of oxygen vacancies with different charge states (0, +1, +2) in beryllium oxide crystal by using density functional theory (DFT). Based on defect formation energy, the positions of charge transition levels are obtained. However, there is a well-known problem that DFT will underestimate the band gap, which leads to the positions of charge transition levels are arguable. To obtain more accurate charge transition levels, we employ the hybrid functionals (HSE) to relieve the band edge problem, as well as use the finite-size corrections (FNV) to correct the defect formation energy. After obtaining the location of the charge transition level, we obtain a reliable description of the optical line shape of the F/F[Formula: see text] center containing electron–phonon coupling. The absorption spectra of the F center and F[Formula: see text] center peak at 7.1 eV and 6.3 eV, respectively. The luminescence band of the F center peaks at 4.7 eV. Furthermore, we speculate that the luminescence band near 3.7 eV is assigned to the F[Formula: see text] center.

Valence Bond Alternative Yielding Compact and Accurate Wave Functions for Challenging Excited States. Application to Ozone and Sulfur Dioxide.

A novel state-averaged version of ab initio nonorthogonal valence bond method is described, for the sake of accurate theoretical studies of excited states in the valence bond framework. With respect to standard calculations in the molecular orbital framework, the state-averaged breathing-orbital valence bond (BOVB) method has the advantage to be free from the penalizing constraint for the ground and excited state(s) to share the same unique set of orbitals. The ability of the BOVB method to faithfully describe excited states and to compute accurate transition energies from the ground state is tested on the five lowest-lying singlet electronic states of ozone and sulfur dioxide, among which 11B2 and 21A1 are the challenging ones. As the 11A2, 11B1, and 11B2 states are of different symmetries than the ground state, they can be calculated at the state-specific BOVB level. On the other hand, the 21A1 states and the 11A1 ground states, which are of like symmetry, are calculated with the state-averaged BOVB technique. In all cases, the calculated vertical energies are close to the experimental values when available, and at par with the most sophisticated calculations in the molecular framework, despite the extreme compactness of the BOVB wave functions, made of no more than 5-9 valence bond structures in all cases. The features that allow the combination of compactness and accuracy in challenging cases are analyzed. For the "ionic" 11B2 states, which are the site of important charge fluctuations, it is because of the built-in dynamic correlation inherent to the BOVB method. For the 21A1 ones, this is the fact that these states have the degree of freedom of having different orbitals than the ground states, even though they are of like symmetry and calculated simultaneously using the newly implemented state-average BOVB algorithm. Finally, the description of the excited states in terms of Lewis structures is insightful, rationalizing the fast ring closure for the 21A1 state of ozone and predicting some diradical character in the so-called "ionic" 11B2 states.

ExoNet Database: Wearable Camera Images of Human Locomotion Environments.

ExoNet Database: Wearable Camera Images of Human Locomotion Environments.

GaN-Based Megahertz Single-Phase Inverter With a Hybrid TCM Control Method for High Efficiency and High-Power Density

Compared with traditional frequency limitation method DCM and QCFTCM for TCM-based inverter, this article proposes a hybrid TCM method, which can achieve both full range ZVS and frequency variation limitation. An accurate resonant transition model is established and the switching frequency variation range can be obtained for TCM. The hybrid control can be implemented according to the variation ratio γ. In order to determine the optimal γ, an offline optimization algorithm based on loss estimation is proposed. Therefore, an accurate analytical loss model for GaN HEMTs considering the nonlinear junction capacitance is given for TCM and hybrid TCM. The loss model shows that the total losses of hybrid TCM inverter are reduced compared with TCM. Moreover, an interleaved GaN-based megahertz single-phase inverter with digital control is demonstrated with 120 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density. The aforementioned benefits are experimentally verified in the optimal hybrid TCM. With this hybrid control, the measured peak efficiency is 98%. Compared with pure TCM mode, there is a 70% reduction in the switching frequency and the related efficiency is 0.8% higher at light loads. Higher power density (135 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) can be achieved in hybrid TCM through further increasing the switching frequency compared with pure TCM.

Commissioning and performance testing of the first prototype of AlignRT InBore™ a Halcyon™ and Ethos™-dedicated surface guided radiation therapy platform.

To commission and assess the performance of AlignRT InBore™, a Halcyon™ and Ethos™-dedicated Surface Guided Radiation Therapy (SGRT) platform which combines ceiling-mounted cameras for patient setup and bore-mounted cameras for in-bore tracking. To check the potential impact of InBore™ cameras on dose delivery, 16 SRS, H&N, breast and pelvis patients' quality assurance (QA) treatment plans were measured with/without AlignRT InBore™ and using ArcCHECK® and SRS MapCHECK®. Impact on image quality was determined using Catphan® 540 phantom and considering all available MV and CBCT protocols (head, breast, chest and pelvis). The stability, accuracy and overall performance of AlignRT InBore™ was assessed using an MV Cube and anthropomorphic phantoms. Comparison of 2D dose distributions with/without AlignRT InBore™ showed no impact on treatment delivery for all 16 QA checks (p-value>0.25). 2D and CBCT images showed no artefacts or change in the contrast-to-noise ratio, resolution and noise values measured with Catphan® 540. Anti-collision sensors were unaffected by the bore-mounted cameras. Additionally, AlignRT InBore™ cameras allowed for motion detection with sub-0.5mm accuracy and sub-0.4mm stability with surface coverage of >50×60×35 cc. Accurate transition (sub-0.3mm) from virtual to treatment isocentres was achieved. Finally, Halcyon™ rotations during CBCT and beam delivery resulted in limited camera vibrations with translation uncertainty <0.5mm in left-right and anterior-posterior directions and <0.1mm in head-feet direction. AlignRT InBore™ provides SGRT setup and intrafraction monitoring capabilities with a performance comparable to standard SGRT solutions while having no adverse effect on Halcyon™.

Transition rates, branching ratio, and lifetime of the 2p33sS2∘5 metastable state in O I

Based on the multiconfiguration Dirac-Hartree-Fock method, the accurate line strengths, transition rates, branching ratio, branching fraction, and lifetime of the $2{p}^{3}3s\phantom{\rule{0.16em}{0ex}}^{5}S_{2}^{\ensuremath{\circ}}$ metastable state of neutral oxygen atom (O i), together with the uncertainties evaluated from the residual electron correlation effects, are determined by taking into account the effects of core-core, core-valence, and valence correlations, the Breit interaction, and QED effect. It is shown that the core correlation effect has a certain influence if the separation between $^{3}S^{\ensuremath{\circ}}$ and $^{5}S^{\ensuremath{\circ}}$ in the ${p}^{3}s$ configuration is accurately calculated. It is found that the calculations of branching ratio of $^{5}S_{2}^{\ensuremath{\circ}}$ remain stable in different electron correlation models. We infer that it is a peculiar intrinsic property leading to results useful for plasma diagnostics and other applications. The transition rates from $^{5}S_{2}^{\ensuremath{\circ}}$ change considerably as a result of the Breit interaction, because the line strengths of $^{3}P_{2}$--$^{5}S_{2}^{\ensuremath{\circ}}$ ($\ensuremath{\lambda}135.560$ nm) and $^{3}P_{1}$--$^{5}S_{2}^{\ensuremath{\circ}}$ ($\ensuremath{\lambda}135.851$ nm) are different in sensitivity to this effect. This affects the calculations of the branching ratio and lifetime. There exist large discrepancies among several calculations of lifetimes, such as the MCHF calculation by [C. Froese Fischer and G. Tachiev, At. Data Nucl. Data Tables 87, 1 (2004)]. The main reasons are ascribed to the neglected electron correlation and relativistic effects. In addition, by checking different calculations with various sets of multireference configurations, we find that the calculations of the electric dipole matrix elements for $^{5}S_{2}^{\ensuremath{\circ}}$ in the length gauge are much more sensitive to electron correlation effects than in the velocity gauge. This may also lead to some errors in the calculations of the lifetime of $^{5}S_{2}^{\ensuremath{\circ}}$ in the length gauge.

Influence of a Forward-Facing Step Surface Irregularity on Swept Wing Transition

An experimental study has been carried out to determine the influence of a forward facing-step (FFS) on the laminar–turbulent transition of a swept wing boundary layer. Wind tunnel experiments were conducted at a fixed 3 deg angle of attack and varying Reynolds number between 2.5 and 4.5 million. Moreover, the FFS influence was investigated under unforced (i.e., smooth leading edge) and forced conditions (i.e., using discrete roughness elements). For each test case infrared thermography was used to determine the transition location and spatial organization of the crossflow vortices. In addition, the change in amplification factor was calculated using linear stability theory. Results reveal the importance of considering multiple parameters when estimating the critical FFS height. The unforced cases indicate that one-parameter correlations (i.e., based on the crossflow vortex core height or boundary-layer displacement thickness) might not be sufficient to universally capture the dynamics of these complex flows. Analysis of the forced cases shows that in addition to local parameters (i.e., step height and vortex core height), the FFS influence on transition depends on the stability characteristics of the incoming instability mode. These findings suggest a complex nonlinear interaction between instabilities and surface irregularities, which highlight the need for multiparameter correlations for accurate transition prediction.

Millimeter- and submillimeter-wave spectroscopy of thioformamide and interstellar search toward Sgr B2(N)

Context.Thioformamide NH2CHS is a sulfur-bearing analog of formamide NH2CHO. The latter was detected in the interstellar medium back in the 1970s. Most of the sulfur-containing molecules detected in the interstellar medium are analogs of corresponding oxygen-containing compounds. Therefore, thioformamide is an interesting candidate for a search in the interstellar medium.Aims.A previous study of the rotational spectrum of thioformamide was limited to frequencies below 70 GHz and to transitions withJ ≤ 3. The aim of this study is to provide accurate spectroscopic parameters and rotational transition frequencies for thioformamide to enable astronomical searches for this molecule using radio telescope arrays at millimeter wavelengths.Methods.The rotational spectrum of thioformamide was measured and analyzed in the frequency range 150−660 GHz using the Lille spectrometer. We searched for thioformamide toward the high-mass star-forming region Sagittarius (Sgr) B2(N) using the ReMoCA spectral line survey carried out with the Atacama Large Millimeter/submillimeter Array.Results.Accurate rigid rotor and centrifugal distortion constants were obtained from the analysis of the ground state of parent,34S,13C, and15N singly substituted isotopic species of thioformamide. In addition, for the parent isotopolog, the lowest two excited vibrational states,v12 = 1 andv9 = 1, were analyzed using a model that takes Coriolis coupling into account. Thioformamide was not detected toward the hot cores Sgr B2(N1S) and Sgr B2(N2). The sensitive upper limits indicate that thioformamide is nearly three orders of magnitude at least less abundant than formamide. This is markedly different from methanethiol, which is only about two orders of magnitude less abundant than methanol in both sources.Conclusions.The different behavior shown by methanethiol versus thioformamide may be caused by the preferential formation of the latter (on grains) at late times and low temperatures, when CS abundances are depressed. This reduces the thioformamide-to-formamide ratio, because the HCS radical is not as readily available under these conditions.

Toward a Practical Method for Hypersonic Transition Prediction Based on Stability Correlations

An accurate boundary-layer transition prediction method integrated with computational fluid dynamics (CFD) solvers is pursued for hypersonic boundary-layer flows over slender hypersonic vehicles at flight conditions. The geometry and flow conditions are selected to match relevant trajectory locations from the ascent phase of the HIFiRE-1 flight experiment, namely, a 7 deg half-angle cone with 2.5 mm nose radius, freestream Mach numbers in the range of 3.8–5.5, and freestream unit Reynolds numbers in the range of . Earlier research had shown that the onset of transition during the Hypersonic International Flight Research Experimentation 1 (HIFiRE-1) flight experiment correlated with an amplification factor of for the planar Mack modes. However, to incorporate the -factor correlations into a CFD code, we investigate surrogate models for disturbance amplification that avoids the direct computation of stability characteristics. The results demonstrate that the application of the commonly used approach, which is based on a database of stability characteristics for locally similar profiles, leads to large, unacceptable errors in the predictions of amplification factors. We propose and demonstrate an alternate approach that employs the stability computations for a canonical set of blunt cone configurations to train a convolutional neural network model that is shown to provide substantially improved transition predictions. The excellent performance of the neural network model is also confirmed for cone configurations with nose radius and half-angle values outside of those used to build the database. Finally, the convolutional neural network model is found to outperform the linear stability calculations for underresolved basic states.

Complete ZVS Analysis in Dual Active Bridge

Zero-voltage-switching (ZVS) has been widely applied in widebandgap devices based on high-switching-frequency converters, for instance, dual-active-bridge isolated dc-dc converter, which consists of two H-bridges. To secure ZVS for all eight switches, previous literature mostly focuses on half-bridge to analyze switching transitions, which, however, is rather incomplete due to ignoring the impact of modulation strategies and cannot fulfill all circumstances. In this letter, the whole H-bridge is used as a unit to analyze the ZVS transient process, addressing the ZVS setting in different modulation strategies. The minimal initial inductor energy to complete the ZVS process is also quantified, which in return can reduce the transformer current, thereby enhancing the efficiency. Furthermore, the accurate ZVS transition time is derived incorporating with the nonlinearity of switch output capacitance, which can be further used to set the dead-band time. An H-bridge prototype with SiC devices is built up to verify the theory proposed in this letter.

Improving the k–ω–γ–Ar transition model by the field inversion and machine learning framework

Accurate simulation of transition from the laminar to the turbulent flow is of great importance in industrial applications. In the present work, the framework of field inversion and machine learning has been applied to improve the four-equation k–ω–γ–Ar transition model. The low-speed transitional flows past two airfoils were numerically simulated. Based on the experimental transition locations, the regularizing ensemble Kalman filtering (EnKF) was performed to obtain the distributions of space-varied correction terms for the first mode time scale in the transitional flows over a natural-laminar-flow (NLF) airfoil, NLF(1)-0416. Then, two machine learning methods, random forest (RF) and artificial neutral network (NN), were adopted to construct the mapping from the mean flow variables to the correction terms. Finally, the learned models were embedded into the original solver. The results show that the regularizing EnKF can efficiently obtain the posterior distribution of the correction terms only by the transition locations. Meanwhile, both the RF- and NN-augmented transition models can predict more accurate transition locations past NLF(1)-0416 at both interpolated and extrapolated angles of attack. Moreover, the RF-augmented model can predict more accurate transitional flows on both the windward and leeward sides of NACA0012 at the same angle of attack. It indicates that the discrepancies within the model are learned and reduced. The modified model has good applicability and generalization ability. Furthermore, by analyzing the relative importance of the features in the RF model, it is found that the streamwise pressure gradient plays the most important role in the physical information and interpretation of the learned model.

Parameter uncertainty quantification for a four-equation transition model using a data assimilation approach

A majority of the simulation discrepancies for RANS models are due to parameter uncertainties. In this paper, a data assimilation approach called the ensemble Kalman filtering (EnKF), was used to investigate the parameter uncertainties of a four-equation k-ω-γ-A r transition/turbulence integrated model. The transitional flows past two wind-turbine airfoils were analyzed, while the transition onset and end locations, as well as the skin friction coefficients, were taken as the observation variables. The results show that the posterior distributions of the parameters can be efficiently obtained through the filtering process, while the estimated parameter variations are observed among different angles of attack (AoAs), as well as different sides at the same AoA. After the EnKF analysis, the most sensitive parameter, C 2 , is changed into an adaptive parameter, which demonstrates the pressure gradients effects through a modified shape factor. More accurate transition locations are calculated by the adaptive C 2 at different AoAs for NLF(1)-0416, and on both sides for NACA-0012 than the original model having constant C 2 . • The EnKF is used to investigate the parameter uncertainties of a transition model. • The estimated parameter variations are observed among different cases. • The most sensitive parameter is modified based on the boundary layer shape factor. • The modified model demonstrates more accurate transition prediction.

Cavity ring-down spectroscopy of CO2 near λ = 2.06 µm: Accurate transition intensities for the Orbiting Carbon Observatory-2 (OCO-2) “strong band”

The λ = 2.06 µm absorption band of CO2 is widely used for the remote sensing of atmospheric carbon dioxide, making it relevant to many important top-down measurements of carbon flux. The forward models used in the retrieval algorithms employed in these measurements require increasingly accurate line intensity and line shape data from which absorption cross-sections can be computed. To overcome accuracy limitations of existing line lists, we used frequency-stabilized cavity ring-down spectroscopy to measure 39 transitions in the 12C16O2 absorption band. The line intensities were measured with an estimated relative combined standard uncertainty of ur = 0.08 %. We predicted the J-dependence of the measured intensities using two theoretical models: a one-dimensional spectroscopic model with Herman-Wallis rotation-vibration corrections, and a line-by-line ab initio dipole moment surface model [Zak et al. JQSRT 2016;177:31-42]. For the second approach, we fit only a single factor to rescale the theoretical integrated band intensity to be consistent with the measured intensities. We find that the latter approach yields an equally adequate representation of the fitted J-dependent intensity data and provides the most physically general representation of the results. Our recommended value for the integrated band intensity equal to 7.183 × 10−21 cm molecule−1 ± 6 × 10−24 cm molecule−1 is based on the rescaled ab initio model and corresponds to a fitted scale factor of 1.0069 ± 0.0002. Comparisons of literature intensity values to our results reveal systematic deviations ranging from −1.16 % to +0.33 %.

Theoretical studies of energy levels and transition data for Zr III

Aims. We seek to present accurate and extensive transition data for the Zr III ion. These data are useful in many astrophysical applications. Methods. We used the multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction (RCI) methods, which are implemented in the general-purpose relativistic atomic structure package GRASP2018. The transverse-photon (Breit) interaction, vacuum polarization, and self-energy corrections are included in the RCI computations. Results. Energy spectra were calculated for the 88 lowest states in the Zr III ion. The root-mean-square deviation obtained in this study for computed energy spectra from the experimental data is 450 cm−1. Electric dipole (E1), magnetic dipole (M1), and electric quadrupole (E2) transition data, line strengths, weighted oscillator strengths, and transition rates are computed between the above states together with the corresponding lifetimes. The computed transition rates are smaller than the experimental rates and the disagreement for weaker transitions is much larger than the experimental error bars. The computed lifetimes agree with available experimental values within the experimental uncertainties.

Determination of accurate rest frequencies and hyperfine structure parameters of cyanobutadiyne, HC5N

Very accurate transition frequencies of HC5N were determined between 5.3 and 21.4 GHz with a Fourier transform microwave spectrometer. The molecules were generated by passing a mixture of HC3N and C2H2 highly diluted in neon through a discharge valve followed by supersonic expansion into the Fabry-Perot cavity of the spectrometer. The accuracies of the data permitted us to improve the experimental 14N nuclear quadrupole coupling parameter considerably and the first experimental determination of the 14N nuclear spin-rotation parameter. The transition frequencies are also well suited to determine in astronomical observations the local speed of rest velocities in molecular clouds with high fidelity. The same setup was used to study HC7N, albeit with modest improvement of the experimental 14N nuclear quadrupole coupling parameter. Quantum chemical calculations were carried out to determine 14N nuclear quadrupole and spin-rotation coupling parameters of HC5N, HC7N, and related molecules. These calculations included evaluation of vibrational and relativistic corrections to the non-relativistic equilibrium quadrupole coupling parameters; their considerations improved the agreement between calculated and experimental values substantially.

The Quest for Highly Accurate Excitation Energies: A Computational Perspective.

We provide an overview of the successive steps that made it possible to obtain increasingly accurate excitation energies with computational chemistry tools, eventually leading to chemically accurate vertical transition energies for small- and medium-size molecules. First, we describe the evolution of ab initio methods employed to define benchmark values, with the original Roos CASPT2 method, then the CC3 method as in the renowned Thiel set, and more recently the resurgence of selected configuration interaction methods. The latter method has been able to deliver consistently, for both single and double excitations, highly accurate excitation energies for small molecules, as well as medium-size molecules with compact basis sets. Second, we describe how these high-level methods and the creation of representative benchmark sets of excitation energies have allowed the fair and accurate assessment of the performance of computationally lighter methods. We conclude by discussing possible future theoretical and technological developments in the field.

Extensive and accurate energy levels, transition rates, lifetimes, hyperfine structures and isotope shifts for the Rb XXXVI spectrum of plasma interest

We present relativistic multiconfiguration Dirac-Hartree-Fock (MCDHF) spectrum calculations for Rb XXXVI with correlations within the n = 8 complex. An extensive and accurate set of energy levels, wavelengths, line strengths, weighted oscillator strengths, lifetimes, isotope shifts, hyperfine structure and Landé gJ factors has been calculated for lower 127 odd- and even-parity states arising from the 1s2 and 1snl(n=1−8,0≤l≤n−1) configurations in He-like-Rb. Transition rates for electric-multipole (dipole (E1), quadrupole (E2), and octupole (E3)) and magnetic-multipole (dipole (M1), quadrupole (M2), and octupole (M3)) have been also calculated. For the accuracy of our results, we have implemented parallel calculations using a Flexible Atomic Code (FAC) by introducing the Second-Order Many-Body Perturbation Theory (MBPT) method. Additionally, Breit interaction and leading quantum electrodynamic effects (QED) have been included as perturbations in extensive relativistic configuration interaction (RCI) calculations. The results arising in the two sets of calculations MCDHF and MBPT are quite close. Our results are compared with other available theory reported in the literature as well as the experimental data listed in the Atomic Spectra Database (ASD) of the National Institute of Standards and Technology (NIST) online database. Good agreement between them has been found. The present complete and consistent results can be used in line identification, plasma modeling and diagnostics of astrophysical plasma.

The Methyl Torsion in Unsaturated Compounds.

How the methyl torsion transition energy in unsaturated systems is affected by its environment is investigated. It is strongly influenced by both its immediate neighborhood, (the number of methyl groups present in the molecule) and the intermolecular interactions. It is clear that the intermolecular interactions have a major influence on the torsion transition energy, as demonstrated unambiguously previously for mesitylene and also seen here for other systems. In part, this may be caused by the fact that the methyl torsion is rarely a pure mode (unless enforced by symmetry). Where the crystal structure is available, the assignments have been supported by CASTEP calculations of the unit cell. The agreement between the observed and calculated spectra is generally good, although not perfect, toluene being a case in point, and highlights just how demanding it is to obtain accurate transition energies for low energy modes. The disagreement between observed and calculated inelastic neutron scattering spectra for meta-xylene and 9,10 dimethylanthracene is so severe that it would suggest that there are additional phases to those presently known. Comparison between the full periodic calculations and those for the isolated molecule shows that intermolecular interactions raise the methyl torsion transition energy by at least 8% and in some cases by more than 50%. The presence of more than one methyl group in the molecule generally raises the average torsion energy from the <100 cm–1 seen for single methyl groups to 150–200 cm–1.

Extended Dynamically Weighted CASPT2: The Best of Two Worlds.

We introduce a new variant of the complete active space second-order perturbation theory (CASPT2) method that performs similarly to multistate CASPT2 (MS-CASPT2) in regions of the potential energy surface where the electronic states are energetically well separated and is akin to extended MS-CASPT2 (XMS-CASPT2) in case the underlying zeroth-order references are near-degenerate. Our approach follows a recipe analogous to that of XMS-CASPT2 to ensure approximate invariance under unitary transformations of the model states and a dynamic weighting scheme to smoothly interpolate the Fock operator between state-specific and state-average regimes. The resulting extended dynamically weighted CASPT2 (XDW-CASPT2) methodology possesses the most desirable features of both MS-CASPT2 and XMS-CASPT2, that is, the ability to provide accurate transition energies and correctly describe avoided crossings and conical intersections. The reliability of XDW-CASPT2 is assessed on a number of molecular systems. First, we consider the dissociation of lithium fluoride, highlighting the distinctive characteristics of the new approach. Second, the invariance of the theory is investigated by studying the conical intersection of the distorted allene molecule. Finally, the relative accuracy in the calculation of vertical excitation energies is benchmarked on a set of 26 organic compounds. We found that XDW-CASPT2, albeit being only approximately invariant, produces smooth potential energy surfaces around conical intersections and avoided crossings, performing equally well to the strictly invariant XMS-CASPT2 method. The accuracy of vertical transition energies is almost identical to MS-CASPT2, with a mean absolute deviation of 0.01–0.02 eV, in contrast to 0.12 eV for XMS-CASPT2.

Predicting distributed roughness induced transition with a four-equation laminar kinetic energy transition model

A four-equation laminar kinetic energy transition model is developed to predict the distributed roughness induced transition using local variables. Based on the laminar kinetic energy transition model (kT-kL-ω model), three key improvements are devised in the work. Firstly, an additional transport equation for roughness amplification factor is combined with the laminar kinetic energy transition model. Secondly, the effective length scale is modified through the roughness amplification factor to consider the enhancement of the first and second unstable mode characteristic timescale. Additionally, for the sake of modeling the roughness effects in the full turbulent zone, the wall boundary condition for the specific turbulence dissipation rate is amended. Numerical results, including flat plate with distributed roughness, sharp biconic configuration with large roughness and hemisphere with different roughness heights, demonstrate that the proposed four-equation transition model is competent for accurate transition prediction at different roughness heights and Reynolds numbers. Besides, with the modification for the wall boundary condition of the specific turbulence dissipation rate, the present model outperforms the original model in simulating turbulent augmentations of skin friction and turbulent heating over rough surfaces. Thus, the present model has attraction and feasibility for simulating distributed roughness induced transition. While more physical mechanisms of roughness induced transition should be considered to further refine this four-equation laminar kinetic energy transition model.