Distortion Analysis Research Articles

Image progressive steganography based on multi-frequency fusion deep network with dynamic sensing

Current deep learning approaches for image steganography primarily focus on single-scale data fusion, often failing to effectively utilize the multi-frequency features of both secret and cover images. Additionally, these methods lack distortion analysis during the data fusion process, which leads to ambiguity issues, resulting in unstable hiding effects and increased susceptibility to detection. To address these challenges, we introduce ProStegNet, a progressive image steganography deep neural network that integrates dynamic sensing and multi-frequency fusion. ProStegNet models the hiding process as a sequence of iterative steps: compression, embedding, correction, re-embedding, and re-correction. We start by designing a multi-stage embedding/extraction module that progressively approaches the optimal stego image by continuously refining the embedding results. This module features a multi-frequency feature processor designed to learn and integrate various frequency features. Additionally, a dynamic sensor corrects the embedding results in real-time based on multi-scale feature variations, guiding subsequent embedding stages. Furthermore, we propose a distribution loss function that effectively captures and constrains the statistical differences between cover-stego pairs and secret-recovery pairs. The performance of the proposed method is assessed using four metrics: imperceptibility, restoration accuracy, anti-detection security, and robustness against attacks. Experimental results show that ProStegNet significantly improves imperceptibility and restoration accuracy compared to existing methods and provides enhanced concealment in terms of anti-detection security. Additionally, the method demonstrates high stability against robust attacks in lossy channels, confirming its effectiveness and practicality for real-world image protection applications.

Research on the Carrier Characteristics of Power Cables Considering the Aging Status of Insulation and Semiconducting Layers

The 10 kV XPLE cable is widely used in highly cabled transmission and distribution networks. It is necessary to closely monitor the transient current, harmonic content, and electric field distribution of each layer of the insulation and semiconductive layers of the cable when they age and deteriorate, so as to promptly carry out circuit breaking treatment and prevent safety accidents. Considering the frequency sensitivity and dielectric sensitivity of the distributed Runit, Lunit, Gunit, and Cunit parameters of long cables, this paper quantitatively analyzes the frequency variation of 10 kV cable parameters under different aging states. Reconstructing the frequency variation process of typical electrical quantities through MATLAB PSCAD joint simulation, constructing fault circuits for cable insulation and semiconducting layers, obtaining transient currents in each layer of the cable under aging conditions, and conducting total harmonic distortion (THD) analysis to provide theoretical guidance for the subsequent monitoring and fault diagnosis of distribution cable status.

Visual Outcomes Following Non-Diffractive Extended-Depth-of-Focus Intraocular Lens Implantation in Patients with Epiretinal Membrane in One Eye and Bilateral Cataracts.

This study aimed to characterize the visual performance in patients with bilateral cataracts and a unilateral epiretinal membrane (ERM) undergoing cataract surgery with non-diffractive extended depth of focus (EDoF) intraocular lens (IOL) placement in both eyes and phacovitrectomy in the eye with ERM. This was a prospective, descriptive, single-arm study. Visual outcomes were measured in monocular and binocular conditions in patients with bilateral cataracts and unilateral ERM stages 2 or 3 implanted with an EDoF IOL. At 6 months, visual acuity (uncorrected and corrected at different distances and contrast levels), contrast sensitivity, and visual disturbances assessed using a Light Distortion Analyzer were determined. We included 22 patients (50% females, mean age of 71.4 ± 5.8 years). Mean monocular best-corrected visual acuities at 100% contrast were 0.07 ± 0.09, 0.23 ± 0.10, and 0.48 ± 0.14 logMAR for eyes with ERM, and 0.02 ± 0.08, 0.19 ± 0.11, and 0.41 ± 0.18 logMAR for fellow eyes for far, intermediate, and near distance vision, respectively. No differences were observed in visual outcomes, contrast sensitivity, or visual disturbances between ERM and non-ERM eyes, except for near distance. No unexpected adverse events were observed. Non-diffractive EDoF IOL can be considered in patients with cataracts and stage 2 or 3 ERM pursuing spectacle independence.

Comparison of single shot and multishot diffusion-weighted imaging in 5-T magnetic resonance imaging for brain disease diagnosis.

Diffusion-weighted imaging (DWI) with single-shot echo-planar imaging (ssEPI) is a valuable tool for detecting acute brain lesions but does suffer from image distortions. Multishot echo-planar imaging (msEPI) is a technique for reducing such distortions. This study aimed to compare the image quality and diagnostic efficacy of ssEPI- and msEPI-DWI at 5.0 T for brain disease detection. This study retrospectively reviewed images of 107 consecutive patients with suspected brain diseases who underwent ssEPI- and msEPI-DWI at 5.0 T at the First Affiliated Hospital of University of Science and Technology of China from August 2023 to September 2023. Two radiologists independently graded image quality and measured the image distortion. Signal-to-noise ratio, contrast-to-noise ratio, and apparent diffusion coefficient (ADC) were calculated and compared between ssEPI- and msEPI-DWI. Image quality scores were compared using the Wilcoxon test and other continuous variables by the paired t-test. The diagnostic accuracy of ADC values in distinguishing lesions from normal-appearing tissues was measured with the area under the curve (AUC). Image quality evaluation and distortion analysis revealed that msEPI-DWI significantly outperformed ssEPI-DWI (two-sided P<0.001). No significant difference was observed in signal-to-noise ratio, contrast-to-noise ratio, or ADC values between msEPI- and ssEPI-DWI (two-sided P≥0.601). The ADC values of msEPI- and ssEPI-DWI showed strong correlations for both lesions (r=0.97) and contralateral normal tissues (r=0.91) (two-sided P<0.001). Compared to those of the contralateral white matter, ADC values of low-grade gliomas (LGGs) were significantly higher [ssEPI-DWI: 1,119.9±273.1 vs. 805.1±73.9; msEPI-DWI: 1,196.2±355.6 vs. 757.3±98.0 (unit: ×10-6 mm2/s)], while the ADC values of acute cerebral infarction (ACI) lesions were significantly lower [ssEPI-DWI: 603.9±273.2 vs. 888.9±212.0; msEPI-DWI: 538.0±281.2 vs. 905.0±188.9 (unit: ×10-6 mm2/s)] (two-sided P≤0.003). The AUCs for detecting LGGs were excellent for both ssEPI-DWI [AUC =0.934; 95% confidence interval (CI): 0.84-1.00] and msEPI-DWI (AUC =0.944; 95% CI: 0.86-1.00) (two-sided P<0.001; two-sided DeLong test: P=0.833). As compared to ssEPI-DWI, msEPI-DWI, when performed at 5.0 T, demonstrated superior image quality and less anatomical distortion in a wide spectrum of brain diseases and showed promising diagnostic performance for LGGs and ACI. In the future, msEPI-DWI at 5.0 T could become clinically routine in the diagnosis and grading of brain disorders.

A DFT Mechanistic Study on the Aza-Aldol Reaction of Boron Aza-Enolates: Relative Stability of Six-Membered Transition State and Its Relevance to the Coordination Mode of the Leaving Group.

The mechanism of the aza-aldol reaction between boron aza-enolate and benzaldehyde is investigated by using density functional theory calculations. The result shows that the syn-E isomer is preferentially formed, consistent with experimental observations. The six-membered ring transition state (TS) with the boat form leads to the E isomer, while the more unstable chair TS does to the Z isomer. The preference of the syn isomer is determined by the interactions between the substituents of aza-enolate and benzaldehyde. Structural distortion and intrinsic reaction coordinate analyses of simplified model systems provide insights into the origin of the relative stability of the rate-determining TS with boat and chair forms. The boat TS is an early TS; thus, minimal structural distortions of the reactant are required to reach this TS. The Lewis pair interactions between the boron and imine groups during B-N elimination also influenced the relative stability of the TSs. This interaction involves the nitrogen lone pair in the boat TS, while the π(N═C) orbital is involved in the chair TS. The Lewis pair with the lone pair stabilizes the TS more than that with the π orbital. The boron aza-enolate with 9-BBN generates an ate complex and forms C-C bonds sequentially, whereas that with Bpin does not generate an ate complex and exhibits the concerted formation of B-O and C-C bonds. Thus, the higher electrophilicity of boron such as 9-BBN enhances the reactivity by facilitating the formation of the ate complex. A reaction design is proposed to reverse the syn/anti selectivity. Proof-of-concept DFT calculations suggested that the modification of the imine group would change the relative stability of the boat/chair TSs and give the anti-product.

Block Copolymer-Directed Single-Diamond Hybrid Structures Derived from X-ray Nanotomography.

Block copolymers are recognized as a valuable platform for creating nanostructured materials. Morphologies formed by block copolymer self-assembly can be transferred into a wide range of inorganic materials, enabling applications including energy storage and metamaterials. However, imaging of the underlying, often complex, nanostructures in large volumes has remained a challenge, limiting progress in materials development. Taking advantage of recent advances in X-ray nanotomography, we noninvasively imaged exceptionally large volumes of nanostructured hybrid materials at high resolution, revealing a single-diamond morphology in a triblock terpolymer-gold composite network. This morphology, which is ubiquitous in nature, has so far remained elusive in block copolymer-derived materials, despite its potential to create materials with large photonic bandgaps. The discovery was made possible by the precise analysis of distortions in a large volume of the self-assembled diamond network, which are difficult to unambiguously assess using traditional characterization tools. We anticipate that high-resolution X-ray nanotomography, which allows imaging of much larger sample volumes than electron-based tomography, will become a powerful tool for the quantitative analysis of complex nanostructures and that structures such as the triblock terpolymer-directed single diamond will enable the generation of advanced multicomponent composites with hitherto unknown property profiles.

Cyclic mechanical response of LPBF Hastelloy X over a wide temperature and strain range: Experiments and modelling

Additive manufacturing (AM) of high-temperature alloys through processes such as laser powder bed fusion (LPBF) has gained significant interest and is rapidly expanding due to its exceptional design freedom, which enables the fabrication of complex parts that contribute to the increased efficiency of aerospace and energy systems. The materials produced through this process exhibit unique microstructures and mechanical properties, which necessitate dedicated study and characterization. In this context, our research focuses on the experimental characterization of the isothermal cyclic viscoplastic mechanical response of Hastelloy X (HX) over the temperature range of 22 to 1000 °C and at various strain rates, addressing a current gap in the literature. Recognizing the need for material models that can accurately represent the cyclic mechanical response of LPBF HX across a broad temperature range, we developed a robust extension of the viscoplastic isotropic-kinematic hardening Chaboche model, intended for applications in the thermomechanical simulation of the LPBF process for the analysis of residual stress and distortion, as well as for assessing the mechanical integrity of LPBF components. The extension involves expressing the entire set of model parameters explicitly with analytical functions to account for their temperature dependence. Consequently, the model includes a relatively large number of parameters to represent the isotropic-kinematic hardening viscoplastic response of the alloy over a wide temperature range, and hence to overcome the endeavor of its systematic calibration, a dedicated calibration approach was introduced. The model ultimately demonstrated its capability to precisely represent the isothermal response of the alloy over the examined temperatures and strain rates. To evaluate the model’s predictiveness for non-isothermal conditions, out-of-phase thermomechanical cyclic experiments were also conducted as independent benchmark tests, where the model’s predictions were fairly consistent with the experimental results. As a part of this study, the derived material model has been integrated into the UMAT subroutine, complete with an analytical derivation of the consistent Jacobian matrix.

Dynamic Harmonic Distortion Analysis and Mitigation Strategies for DC Third Rail Systems

Harmonic distortions in DC third rail systems can cause overheating of electric motors and transformers. Single-tuned filters and shunt active harmonic filters (SAHFs) are often used to mitigate the harmonic distortions. However, there is a lack of studies on the effects of train dynamics on harmonic distortions. This paper aims to investigate the influence of dynamic train behaviors for a DC third rail system and provide recommendations for the design of single-tuned filters and SAHFs to mitigate the harmonic distortions. The traction power supply system of a DC third rail system in Malaysia is modeled using ETAP-eTraX and MATLAB-Simulink software for the investigation. The ETAP-eTraX software is used to accurately compute the dynamic behavior of the train, while MATLAB-Simulink allows for the assessment of the impact of train behavior on the rail track, as well as the harmonic effect of the railway power network on the train. The findings showed that the SAHF exhibits strong adaptability and superior filtering performance compared to the single-tuned filter in addressing dynamic harmonic distortion in traction power supply systems. This study emphasizes the significance of incorporating harmonic mitigation devices, particularly for managing dynamic harmonic distortion based on actual train consumption patterns.

Harnessing forward multiple scattering for optical imaging deep inside an opaque medium

As light travels through a disordered medium such as biological tissues, it undergoes multiple scattering events. This phenomenon is detrimental to in-depth optical microscopy, as it causes a drastic degradation of contrast, resolution and brightness of the resulting image beyond a few scattering mean free paths. However, the information about the inner reflectivity of the sample is not lost; only scrambled. To recover this information, a matrix approach of optical imaging can be fruitful. Here, we report on a de-scanned measurement of a high-dimension reflection matrix R via low coherence interferometry. Then, we show how a set of independent focusing laws can be extracted for each medium voxel through an iterative multi-scale analysis of wave distortions contained in R. It enables an optimal and local compensation of forward multiple scattering paths and provides a three-dimensional confocal image of the sample as the latter one had become digitally transparent. The proof-of-concept experiment is performed on a human opaque cornea and an extension of the penetration depth by a factor five is demonstrated compared to the state-of-the-art.

Investigations of BLDC motor speed characteristics via THD under conventional and advanced hybrid controllers

This project investigates brushless direct current (BLDC) motor speed control through total harmonic distortion (THD) analysis, employing proportional integral (PI), fuzzy logic (FLC), adaptive neuro-fuzzy inference system (ANFIS), and an innovative hybrid ANFIS-PD/PI controller. Considering the vital role of BLDC motors in precision-dependent industries like robotics, electric vehicles, and industrial automation, our primary focus is on understanding BLDC motor operation and recognizing THD's significance as a performance metric. Controllers are meticulously implemented in real-time, fine-tuned, and optimized to achieve desired speed characteristics, incorporating considerations like response time, accuracy, and energy efficiency. The project's core involves THD analysis, quantifying harmonic content in the BLDC motor's speed waveform. This facilitates a comprehensive comparative evaluation of controller performance, assessing their capability to maintain speed stability and influence power quality. The discussion covers the merits and limitations of each controller, with a special emphasis on the hybrid ANFIS-PD/PI controller, seamlessly blending ANFIS adaptability with PD/PI control stability. Results illustrate the hybrid controller's excellence in optimizing BLDC motor speed control, demonstrating superior performance in speed accuracy, disturbance rejection, and THD reduction. These findings drive advancements in motor control technology, providing practical guidance for selecting controllers tailored to specific application requirements. Simulation results can be analyzed using MATLAB/Simulink 2018a Software.

Analysis of Nonlinear Distortions of Dphemt Structures Based on a GaAs/InGaAs Compound with Double-Sided Delta-Doping

The paper presents the results of studies of C–V characteristics of GaAs/In0.53Ga0.47As HEMT before and after neutron irradiation with a fluence of (6.3 ± 1.3) × 1014 cm–2. Based on the experimentally obtained characteristics, the effective electron distribution profiles of the structure were calculated before and after radiation impact. The effect of radiation defects on the δ-layers of the structure was analyzed.

Welding Distortions Analysis Considering the Hardening Model, Deposition Processes, and Dissimilar Mechanical Behavior of the Base and Filler Metal

Welding Distortions Analysis Considering the Hardening Model, Deposition Processes, and Dissimilar Mechanical Behavior of the Base and Filler Metal

Virus Infected Papaya Plants Differentially affects Oxidative Stress and Survival in Caenorhabditis elegans

Carica papaya (papaya) leaves has significant nutraceutical properties. However, it is speculated that papaya leaf curl virus (PaLCuV) and papaya ring spot virus (PRSV) can severely affect the therapeutic properties and alter the overall nutraceutical potential of papaya leaves. Therefore, we evaluated the bioactivity of the virus infected papaya leaves extract (PLE) compared to healthy PLE in C. elegans. Viruses infection were confirmed by visual inspection and PCR based detection. Anatomical changes and elemental analysis were analyzed through SEM-EDS. PLE were tested for life span extension and ROS scavenging activity on C. elegans. Infected leaves displayed typical symptoms of curling, distortion and anatomical analysis revealed closed and less number of stomata. Healthy PLE extended (24%) the life span of C. elegans with no significant change in ROS generation while in PaLCuV and PRSV infected PLE, were observed to have significant reduction in the mean life span of 15.4% and 17% with 1.2-fold and 1.9-fold increase in ROS generation.

Single-cell topographical profiling of the immune synapse reveals a biomechanical signature of cytotoxicity

Immune cells have intensely physical lifestyles characterized by structural plasticity and force exertion. To investigate whether specific immune functions require stereotyped mechanical outputs, we used super-resolution traction force microscopy to compare the immune synapses formed by cytotoxic T cells with contacts formed by other T cell subsets and by macrophages. T cell synapses were globally compressive, which was fundamentally different from the pulling and pinching associated with macrophage phagocytosis. Spectral decomposition of force exertion patterns from each cell type linked cytotoxicity to compressive strength, local protrusiveness, and the induction of complex, asymmetric topography. These features were validated as cytotoxic drivers by genetic disruption of cytoskeletal regulators, live imaging of synaptic secretion, and in silico analysis of interfacial distortion. Synapse architecture and force exertion were sensitive to target stiffness and size, suggesting that the mechanical potentiation of killing is biophysically adaptive. We conclude that cellular cytotoxicity and, by implication, other effector responses are supported by specialized patterns of efferent force.

RF, harmonic distortion and linearity analysis of core-shell junctionless-FET using NQS small signal model

Abstract This paper deals with the performance analysis of Core-Shell (C-S) Junctionless (JL) FET structure in the RF domain application. The analysis begins with the non-quasi static (NQS) small signal model representation and from there the extraction of RF-parameters; and there after the harmonic distortions, linearity FOMs and Y-parameter are analyzed in detail. The device is investigated based on the variations of core/shell-thicknesses and shell-dopant concentrations. Y-parameters are evaluated from the NQS small signal model. In the RF domain analysis, the parameters such as, Cgs, Cgd, Rgs, Rgd, fT and τm are assessed to determine its RF merits. Using the two-port equivalent model, the Y-parameters (Y11, Y12, Y21, Y22) are evaluated and investigated. The second and third order harmonic distortions (HD2, HD3) are calculated using IFM method and studied in detail. In addition to that, second, third harmonic intercept voltages (VIP2, VIP3) and third order intermodulation distortion (IMD3) are also assessed for its linearity performances in domain specific applications. The proposed device is designed using the Silvaco ATLAS TCAD. The device is calibrated with the experimental data that shows a close match between the two. The proposed device is found to exhibit good linearity and very low harmonic distortion behavior by modulating the shell-doping and thickness.

Norwid in studies by Rolf Fieguth

This article aims discusses Rolf Fieguth’s studies of works by Norwid, focusing primarily on the German Slavist’s interpretations of the cycle Vade-mecum and the long poem Quidam. The first work reconstructed here, along with its assumptions and conclusions, is Fieguth’s 1985 study on “poetry in a critical phase”and the second is the 2005 essay on the comparative contexts of Norwid’s famous cycle (the latter was published in Polish in 2011). A lot of room is devoted in this section to Fieguth’s analysis of distortions introduced by Norwid at various levels of the poem’s organization. These remarks are complemented with an account of Fieguth’s comparatist conceptof “cultural confrontation,” which goes beyond dualistic accounts of literary creativity, revealing the invariably broad, European context of meetings between poets and texts, facilitated by the process of national cultures permeating each other. The second part of the article is devoted to Fieguth’s 2014 book Zaproszenie do „Quidama”. Portret poematu Cypriana Norwida [An invitation to Quidam. A portrait of Cyprian Norwid’s long poem]. Reflections on this publication concern not only its detailed findings about Norwid’s long poem but also the critic’s methodological assumptions, which have helped him to update the long-standing genre in the history of literature, namely the “author and his particular work” type of monograph. Among the issues addressed in the book, the article discusses, in particular, the difficulties accompanying interpretations of Quidamand the question of Norwid’s classicism. The third part of the article draws attention to Fieguth’s remarks onNorwid made in recent years (2017, 2018, 2020). The article thus summarizes Rolf Fieguth’s thirty years of research on the most important poetic achievements of the Polish poet.

Computational image analysis of distortion, sharpness, and depth of field in a next-generation hybrid exoscopic and microsurgical operative platform.

The development of surgical microscope-associated cameras has given rise to a new operating style embodied by hybrid microsurgical and exoscopic operative systems. These platforms utilize specialized camera systems to visualize cranial neuroanatomy at various depths. Our study aims to understand how different camera settings in a novel hybrid exoscope system influence image quality in the context of neurosurgical procedures. We built an image database using captured cadaveric dissection images obtained with a prototype version of a hybrid (microsurgical/exoscopic) operative platform. We performed comprehensive 4K-resolution image capture using 76 camera settings across three magnification levels and two working distances. Computer algorithms such as structural similarity (SSIM) and mean squared error (MSE) were used to measure image distortion across different camera settings. We utilized a Laplacian filter to compute the overall sharpness of the acquired images. Additionally, a monocular depth estimation deep learning model was used to examine the image's capability to visualize the depth of deeper structures accurately. A total of 1,368 high-resolution pictures were captured. The SSIM index ranged from 0.63 to 0.85. The MSE was nearly zero for all image batches. It was determined that the exoscope could accurately detect both the sharpness and depth based on the Laplacian filter and depth maps, respectively. Our findings demonstrate that users can utilize the full range of camera settings available on the exoscope, including adjustments to aperture, color saturation, contrast, sharpness, and brilliance, without introducing significant image distortions relative to the standard mode. The evolution of the camera incorporated into a surgical microscope enables exoscopic visualization during cranial base surgery. Our result should encourage surgeons to take full advantage of the exoscope's extensive range of camera settings to match their personal preferences or specific clinical requirements of the surgical scenario. This places the exoscope as an invaluable asset in contemporary surgical practice, merging high-definition imaging with ergonomic design and adaptable operability.

Advanced testbed to assess disturbances in electrical grids with DERs using relays/meters with varying sampling frequencies

Distributed energy resources (DERs) are vital to achieve clean energy goals, but in some cases, their rapid deployment has led to negative effects on their reliability because of possible voltages and/or current disturbances that need to be analyzed in detail. This study created an advanced testbed with a real-time simulator and synchronized time and trigger event systems was created to compare event disturbances from intelligent electronic devices (IEDs) with different sampling frequencies and locations in an electrical grid containing DERs. This testbed is capable of capturing the recorded events of multiple IEDs and the real-time simulator to assess the effect of the disturbances and IEDs’ behaviors, including phase voltages, phase current waveforms, and total harmonic distortion (THD) analysis. In this study, a three-line-to-ground electrical fault was simulated, the disturbance event was detected, and recorded events (from 4 to 133 samples per cycle) were collected from meters and relays located at different sites. A harmonic peak algorithm, which was based on measuring the phase voltage and phase current THD peaks at the first one-cycle of the disturbance events, was created to assess and detect the fault states and locations. Several important findings resulted from performing this study, such as selecting IEDs with high sampling frequencies, installing all IEDs with similar sampling frequencies, assessing the software limitations for computing THD, studying the effect of the IEDs’ locations (downstream or upstream) with respect to the electrical fault site and the distance from the disturbance event point, evaluating the percentage errors of the phase voltage THD peaks at the first one-cycle of disturbance events, and installing synchronized time source and trigger event signal systems for recording the IEDs’ events.

Linearity and intermodulation distortion analysis of single and dual metal gate junctionless transistor

Linearity and intermodulation distortion are very crucial parameters for RFICs design. Therefore, in this work, a detailed comparative analysis on linearity and intermodulation distortion of single metal (SMG) and double metal (DMG) double gate junction less transistor (JLT) is done using TCAD silvaco suite. Furthermore, the effects of temperature fluctuation, gate length variation, and gate material engineering on the linearity performance of both devices are also studied. A few significant figures of merit, including Voltage Intercept Point 2 (VIP2), Voltage Intercept Point 3 (VIP3), Third Order Intercept Power (IIP3), 1 dB Compression Point (P1dB), Third Order Intermodulation Distortion (IMD3), and the transconductance derivative parameters First Order Transconductance (gm1), Second Order Transconductance (gm2), and Third Order Transconductance (gm3) are used to assess the device linearity and intermodulation distortion of SMG and DMG JLT's. The findings show that higher VIP2, VIP3, IIP3, 1-dB compression point and lower gm3, IMD3 values are obtained for the SMG JLT device when compared to its counterpart DMG JLT. SMG JLT, which assures strong linearity and low distortion.

Origin of Chemoselectivity of Halohydrin Dehalogenase-Catalyzed Epoxide Ring-Opening Reactions.

By performing molecular dynamics (MD), quantum mechanical/molecular mechanical (QM/MM) calculations, and QM cluster calculations, the origin of chemoselectivity of halohydrin dehalogenase (HHDH)-catalyzed ring-opening reactions of epoxide with the nucleophilic reagent NO2- has been explored. Four possible chemoselective pathways were considered, and the computed results indicate that the pathway associated with the nucleophilic attack on the Cα position of epoxide by NO2- is most energetically favorable and has an energy barrier of 12.9 kcal/mol, which is close to 14.1 kcal/mol derived from experimental kinetic data. A hydrogen bonding network formed by residues Ser140, Tyr153, and Arg157 can strengthen the electrophilicity of the active site of the epoxide substrate to affect chemoselectivity. To predict the energy barrier trends of the chemoselective transition states, multiple analyses including distortion analysis and electrophilic Parr function (Pk+) analysis were carried out with or without an enzyme environment. The obtained insights should be valuable for the rational design of enzyme-catalyzed and biomimetic organocatalytic epoxide ring-opening reactions with special chemoselectivity.