Misalignment Model Research Articles

Effects of foundation pit excavation on adjacent metro stations and shield tunnel structures: a study on horizontal displacement

PurposeThe aim of this study is to investigate the horizontal displacement effects of foundation pit excavation on adjacent metro stations and shield tunnel composite structures. It seeks to develop a theoretical calculation method capable of accurately assessing these engineering impacts, aiming to provide practical assistance for engineering applications.Design/methodology/approachThis study introduces a model for shield tunnel segments incorporating rotation and misalignment, considering the constraints of metro stations. It establishes a displacement model for tunnel-station combinations during foundation pit excavation, deriving a formula for calculating station-proximal tunnel horizontal displacements. The method's accuracy is validated against field data from three engineering cases. The research also explores variations in tunnel displacement, inter-ring shear force, misalignment and rotation angle under different spatial relationships between pits, tunnels and stations.FindingsThis study models uneven deformation between stations and tunnels due to bending stiffness and shear constraints. It enhances the misalignment model with station-induced shear effects and introduces coefficients for their mutual interaction. Results show varied responses based on pit-station-tunnel positioning: minimal displacement near pit edges (coefficients around 0.1) and significant effects near pit centers (coefficients from 0.4 to 0.5). “Whip effect” from station constraints affects tunnel displacement, shear force, misalignment and rotation, with fluctuations decreasing with distance from excavation areas.Originality/valueThis study demonstrates significant originality and value. It introduces a novel displacement model for tunnel-station combinations considering station constraints, addressing theoretical calculations of horizontal displacement effects from foundation pit excavation on metro stations and shield tunnel structures. Through validation with field data and parameter studies, the concept of influence coefficients is proposed, offering insights into variations in structural responses under different spatial relationships. This research provides crucial technical support and decision-making guidance for optimizing designs and facilitating practical construction in similar engineering projects.

A Broken Duet: Multistable Dynamics in Dyadic Interactions.

Misunderstandings in dyadic interactions often persist despite our best efforts, particularly between native and non-native speakers, resembling a broken duet that refuses to harmonise. This paper delves into the computational mechanisms underpinning these misunderstandings through the lens of the broken Lorenz system-a continuous dynamical model. By manipulating a specific parameter regime, we induce bistability within the Lorenz equations, thereby confining trajectories to distinct attractors based on initial conditions. This mirrors the persistence of divergent interpretations that often result in misunderstandings. Our simulations reveal that differing prior beliefs between interlocutors result in misaligned generative models, leading to stable yet divergent states of understanding when exposed to the same percept. Specifically, native speakers equipped with precise (i.e., overconfident) priors expect inputs to align closely with their internal models, thus struggling with unexpected variations. Conversely, non-native speakers with imprecise (i.e., less confident) priors exhibit a greater capacity to adjust and accommodate unforeseen inputs. Our results underscore the important role of generative models in facilitating mutual understanding (i.e., establishing a shared narrative) and highlight the necessity of accounting for multistable dynamics in dyadic interactions.

Joint Spatial Modeling Bridges the Gap Between Disparate Disease Surveillance and Population Monitoring Efforts Informing Conservation of At-risk Bat Species

AbstractWhite-Nose Syndrome (WNS) is a wildlife disease that has decimated hibernating bats since its introduction in North America in 2006. As the disease spreads westward, assessing the potentially differential impact of the disease on western bat species is an urgent conservation need. The statistical challenge is that the disease surveillance and species response monitoring data are not co-located, available at different spatial resolutions, non-Gaussian, and subject to observation error requiring a novel extension to spatially misaligned regression models for analysis. Previous work motivated by epidemiology applications has proposed two-step approaches that overcome the spatial misalignment while intentionally preventing the human health outcome from informing estimation of exposure. In our application, the impacted animals contribute to spreading the fungus that causes WNS, motivating development of a joint framework that exploits the known biological relationship. We introduce a Bayesian, joint spatial modeling framework that provides inferences about the impact of WNS on measures of relative bat activity and accounts for the uncertainty in estimation of WNS presence at non-surveyed locations. Our simulations demonstrate that the joint model produced more precise estimates of disease occurrence and unbiased estimates of the association between disease presence and the count response relative to competing two-step approaches. Our statistical framework provides a solution that leverages disparate monitoring activities and informs species conservation across large landscapes. Stan code and documentation are provided to facilitate access and adaptation for other wildlife disease applications.

Numerical simulation method and deterioration analysis of load-bearing performance of tunnel linings containing cold joints in plain concrete

Cracking in tunnel linings is a common issue in tunnel engineering, with the main cause being construction-induced defects. As a construction-induced defect in a lining, a cold joint affects the bearing capacity of the lining, and the effect of cold joints on the bearing performance deterioration of linings remains unclear. In this study, 180 high-speed railroad tunnels built in Grade III surrounding rock areas were investigated to determine their degradation states, and the distribution of lining cracks in these tunnels was explored on the basis of different factors. Subsequently, three-point bending experiments were conducted on concrete components with different pouring interval cold joint. Based on the experimental results, a computational unit applicable to cold joint simulation was proposed, and the unit parameters were inverted. Finally, the unit was applied to establish a tunnel model with cold joints and to analyze the deterioration effect of cold joints on the bearing performance of the lining. The cracks caused by cold joints in the lining of a structure were found to extend perpendicular to the lining surface, and this can greatly affect the overall strength of the structure. It's important to consider the impact of cold joints on the lining. In order to simulate these cold joints, cohesive elements were used to calculate the maximum stress and stiffness degradation of the lining with and without cold joint elements. The results showed that there were only small differences, indicating that cohesive elements are effective for simulating cold joints. Two cracking patterns were identified, the dorsal tension misalignment model and the medial tension misalignment model, which are related to the stress state of the cold joints. It's necessary to pay attention to cold joints in the inner tensioned area of the lining and those that exceed the final setting time of concrete during pouring.

Effect of the focusing system on measurements in gravitational wave detection telescope

Telescopes primarily transmit and receive laser beams over long distances as part of a gravitational wave interferometric measurement system. Due to factors such as optical design, fabrication, and alignment, the wavefront at the exit pupil of the telescope inevitably experiences distortion, resulting in wavefront aberrations that couple with pointing jitter to generate tilt-to-length (TTL) coupling noise. During the process of gravitational wave detection, the large distance between the primary and secondary mirrors and temperature fluctuations in space can cause significant axial misalignment between them. This results in a substantial displacement of the primary-secondary mirror system’s primary focus along the axial direction, further degrading the wavefront at the exit pupil of the telescope. The TTL coupling noise caused in this scenario will affect the detection of gravitational waves, thus requiring the adjustment of the position of the three-four mirror system through the focusing system to minimize TTL coupling noise. In this paper, the model for TTL coupling noise was established using the first 36 orders of Zernike polynomials. The misalignment model of the primary-secondary mirror system was derived using geometric optics theory. The study investigates the influence of the telescope focusing system before and after focusing on the wavefront aberrations and TTL coupling noise at the exit pupil of the telescope. The analysis indicates that with a misalignment of 7.56 μm in the axial distance between the primary and secondary mirrors, the addition of a focusing system reduces the wavefront error at the exit pupil of the telescope from 0.0328 λ to 0.0046 λ. Furthermore, the maximum coupling noise between wavefront distortion and pointing jitter is reduced from 4 pm Hz−1/2 to 0.4 pm Hz−1/2. This provides valuable insights for the design of gravitational wave detection telescopes and the study of focusing systems.

Dynamic misalignment effects on performance of dynamically loaded journal bearings

The lubrication characteristics of dynamically loaded journal bearings are significantly affected by misalignments. However, existing research on misalignment primarily focuses on fixed misalignment models, and studies on the nonlinear dynamic response of dynamically loaded bearings under dynamic misalignment are yet to be reported. To address this research gap, this study proposed a dynamic misalignment model coupled with rotor dynamics and transient mixed elastohydrodynamic lubrication. The model comprehensively considers factors such as journal eccentric translation, surface topography, oil film cavitation, and bearing elastic deformation. Upon model validation, numerical simulations are conducted to reveal the single-cycle nonlinear tribological characteristics of dynamically loaded bearings subjected to transient time-varying dynamic loads and time-varying misalignment moments. Based on the dynamic misalignment model, a series of parameter studies were conducted to explore the influence of operating conditions such as load magnitude and rotational speed on lubrication characteristics. The research also evaluated the impact of various structural parameters, including surface roughness, bearing bush thickness, and radial clearance, on the performance of dynamically loaded bearings. The numerical results indicate that the impact of fixed-value misalignment on the performance is highly dependent on the manually set deflection angles. Under light-load and high-speed nonstationary operating conditions, the effect of dynamic misalignment on the lubrication characteristics of dynamically loaded journal bearings was significantly amplified. Furthermore, a smoother surface, thicker bearing bush, and smaller radial clearance intensify dynamic misalignment's influence, compared to fixed-value misalignment, on the transient rough contact behavior at the interface. The findings of this study provide valuable guidance and references for the theoretical analysis and optimization design of dynamically loaded journal bearings.

Developing a misalignment model for folded optical resonators and designing a kilowatt-class disk laser resonator with a short effective length

In this article, a formulation was developed for designing a stable disk laser resonator and achieving a high power and a beam quality close to the fundamental mode with a short effective length. In this regard, by taking a matrix approach and using Gaussian beam propagation based on the ABCD law for Gaussian beams, the fundamental-mode spot size inside a resonator and its sensitivity to misalignment, as well as dynamic stability in multiple folded resonators, were analyzed in order to achieve a short effective length. In the presented method, the optimal geometrical parameters of the resonator were obtained by applying the length limits, permissible level of sensitivity to misalignment, and range of dynamic stability with the help of MATLAB software coding. Using this design algorithm, a Z-shaped resonator with the arm length of 50 cm and fundamental-mode spot size of 2.4 mm on the active media was designed, while the resonator had a good dynamic stability and low sensitivity to misalignment. Considering these specifications, it was possible to design a compact disk laser with a power of 1 kW, which had a beam quality close to the fundamental mode.To the best of our knowledge, the laser disk resonator described in this paper, which is resistant to misalignment and has a short effective length, has not been previously documented in the literature. The model developed in this research is a general model that can be used in much more complex structures with any numbers of optical elements in other lasers.

Mining multi-center heterogeneous medical data with distributed synthetic learning

Overcoming barriers on the use of multi-center data for medical analytics is challenging due to privacy protection and data heterogeneity in the healthcare system. In this study, we propose the Distributed Synthetic Learning (DSL) architecture to learn across multiple medical centers and ensure the protection of sensitive personal information. DSL enables the building of a homogeneous dataset with entirely synthetic medical images via a form of GAN-based synthetic learning. The proposed DSL architecture has the following key functionalities: multi-modality learning, missing modality completion learning, and continual learning. We systematically evaluate the performance of DSL on different medical applications using cardiac computed tomography angiography (CTA), brain tumor MRI, and histopathology nuclei datasets. Extensive experiments demonstrate the superior performance of DSL as a high-quality synthetic medical image provider by the use of an ideal synthetic quality metric called Dist-FID. We show that DSL can be adapted to heterogeneous data and remarkably outperforms the real misaligned modalities segmentation model by 55% and the temporal datasets segmentation model by 8%.

LED array microscopy system correction method with comprehensive error parameters optimized by phase smoothing criterion.

LED array microscopy is a novel computational imaging technique that can achieve two-dimensional (2D) phase imaging and three-dimensional (3D) refractive index imaging with both high resolution and a large field of view. Although its experimental setup is simple, the errors caused by LED array position and light source central wavelength obviously decrease the quality of reconstructed results. To solve this problem, comprehensive error parameters optimized by the phase smoothing criterion are put forward in this paper. The central wavelength error and 3D misalignment model with six freedom degree errors of LED array are considered as the comprehensive error parameters when the spatial positional and optical features of arbitrarily placed LED array are unknown. Phase smoothing criterion is also introduced to the cost function for optimizing comprehensive error parameters to improve the convergence results. Compared with current system correction methods, the simulation and experimental results show that the proposed method in this paper has the best reconstruction accuracy, which can be well applied to an LED array microscope system with unknown positional and optical features of the LED array.

Numerical and experimental analysis of vibration characteristics of spindle system under bearing assembly errors

To research the vibration problem caused by bearing assembly errors in machine tool spindles, a special test rig for rolling bearing misalignment is designed and built. The dynamic model of the spindle-bearing-pedestal system of the test rig is established, and the characterization method for bearing parallel and angular misalignments is given through the Hertz contact theory. The effect rule of the misalignment level on spindle vibration response is studied by simulation and experiment, and the system dynamic model and bearing misalignment model are verified. On this basis, the vibration characteristics of the spindle system under the joint effect of raceway misalignment and waviness are further analyzed. The numerical and experimental results show that when the bearing is in the misalignment state, the excitation of bearing variable compliance increases. The assembly errors of the bearing raceway lead to the deviation of the centroid motion trajectory of the spindle tool end, which seriously affects the machining accuracy of the machine tool. In the case of severe angular misalignment, the system shows chaotic motion, indicating that the instability of the system is enhanced. The impact of angular misalignment on system vibration is greater than parallel misalignment, so bearing ring tilt should be avoided as far as possible in practice. In addition, it is also found that the variation of excitation amplitude of bearing waviness caused by raceway tilt is related to the relationship between the number of waviness and ball number.

Development and multi-institutional validation of a convolutional neural network to detect vertebral body mis-alignments in 2D x-ray setup images.

Misalignment to the incorrect vertebral body remains a rare but serious patient safety risk in image-guided radiotherapy (IGRT). Our group has proposed that an automated image-review algorithm be inserted into the IGRT process as an interlock to detect off-by-one vertebral body errors. This study presents the development and multi-institutional validation of a convolutional neural network (CNN)-based approach for such an algorithm using patient image data from a planar stereoscopic x-ray IGRT system. X-rays and digitally reconstructed radiographs (DRRs) were collected from 429 spine radiotherapy patients (1,592 treatment fractions) treated at six institutions using a stereoscopic x-ray image guidance system. Clinically-applied, physician approved, alignments were used for true-negative, "no-error" cases. "Off-by-one vertebral body" errors were simulated by translating DRRs along the spinal column using a semi-automated method. A leave-one-institution-out approach was used to estimate model accuracy on data from unseen institutions as follows: All of the images from five of the institutions were used to train a CNN model from scratch using a fixed network architecture and hyper-parameters. The size of this training set ranged from 5,700 to 9,372 images, depending on exactly which five institutions were contributing data. The training set was randomized and split using a 75/25 split into the final training/ validation sets. X-ray/ DRR image pairs and the associated binary labels of "no-error" or "shift" were used as the model input. Model accuracy was evaluated using images from the sixth institution, which were left out of the training phase entirely. This test set ranged from 180 to 3,852 images, again depending on which institution had been left out of the training phase. The trained model was used to classify the images from the test set as either "no-error" or "shifted", and the model predictions were compared to the ground truth labels to assess the model accuracy. This process was repeated until each institution's images had been used as the testing dataset. When the six models were used to classify unseen image pairs from the institution left out during training, the resulting receiver operating characteristic area under the curve values ranged from 0.976 to 0.998. With the specificity fixed at 99%, the corresponding sensitivities ranged from 61.9% to 99.2% (mean: 77.6%). With the specificity fixed at 95%, sensitivities ranged from 85.5% to 99.8% (mean: 92.9%). This study demonstrated the CNN-based vertebral body misalignment model is robust when applied to previously unseen test data from an outside institution, indicating that this proposed additional safeguard against misalignment is feasible. This article is protected by copyright. All rights reserved.

Study on deterioration, cracking mechanism and treatment measures of plain concrete lining with cold joints in high-speed railroad tunnel

Cracks in lining will lead to derivative diseases even seriously threaten the safety of high-speed trains. Construction-induced defects and external environmental changes are the main causes of lining cracks. From a typical high-speed railroad tunnel with a large number of lining cracks in China, construction cold joints are the main cause of its lining cracks. Based on the current research, both microscopic model and macroscopic model of concrete with cold joints were established to verify the applicability of the macroscopic model to simulate concrete elements with cold joints. Besides, finite element models with single and multiple cold joints were constructed to analyze the bearing performance and cracking mechanism of lining with cold joints. Finally, measures were proposed for the lining cracks caused by the expansion of cold joints. The results showed that: Using macroscopic model to simulate concrete elements with cold joints is reasonable. The tension area with cold joints has the most obvious deterioration, which is consistent with the cracking characteristics of field lining. Therefore, it is necessary to detect the cold joint defects in tensile area and where the pouring intervals exceed the initial setting time. The cracking of lining with single cold joints can be divided into two patterns, the back-side tension misalignment model and the inner-side tension misalignment model. While the cracking model with multiple cold joints can be regarded as a combination of single cold joint cracking models. The stress distribution and performance deterioration of lining with multiple cold joints is more complicated than that of single cold joints, more researches can be carried out by the method of this study.

Accuracy of Direct Composite Veneers via Injectable Resin Composite and Silicone Matrices in Comparison to Diagnostic Wax-Up.

Purpose: To evaluate the discrepancy between the diagnostic wax-up and the resulting direct veneers using different matrices. Materials and method: A total of 48 identical misaligned models, 12 wax-up models and one ‘every other tooth’ wax-up model were 3D printed. Group 1: Transparent silicone matrices with holes for the injection of the flowable composite. Group 2: The same procedure as group 1, but the first three teeth were restored using the matrix constructed from the ‘every other tooth’ wax-up model. Group 3: Transparent silicone matrices cut for each tooth and preheated resin composite. Group 4: The same procedure as group 3, but the loaded matrix was placed first in the clear plastic tray, which was used for the matrix’s fabrication. Group 5: Wax-up models (control group). Scans from the veneers were superimposed with the scans from the wax-up and compared using the Patient Monitoring software. Measurements were made at the incisal, middle and cervical third. Kruskal-Wallis test and Dunn post-hoc test (p < 0.05) were used to analyze the results. Results: No statistically significant differences were found between groups 1 and 2 and the control. Group 3 was different from the control in the incisal and middle third, and group 4 was different in the cervical third. Conclusions: (1) Use of one or two matrices and the injection of flowable composite were accurate techniques. (2) Use of a matrix for each tooth combined with a pre-heated composite was the most inaccurate technique, but the use of the clear tray in combination with the matrix improved the accuracy.

A realistic guide misalignment model for the Second Target Station instruments at the Spallation Neutron Source

The Second Target Station (STS) at the Spallation Neutron Source, including a suite of initial instrument concepts, are being designed in Oak Ridge. The moderator size at STS is significantly smaller than that of the First Target Station, making the guide misalignment a more prominent concern. A realistic misalignment model based on Monte Carlo neutron ray tracing simulation was developed to evaluate the impacts of both the random misalignment and floor settlement on the performance of a toy model of 150 m straight guide system, and MENUS, an STS instrument concept with a typical guide design of two opposing Montel mirrors. The study shows that longer instruments, and instruments with complex curved mirrors/guides are sensitive to significant performance penalties due to misalignments.

Efficient MIMO Configuration for Bi-Directional Vertical FSO Link with Multiple Beam Induced Pointing Error

We proposed the statistical misalignment model and the power-efficient configuration of transceivers for bi-directional multi-input and multi-output (MIMO) based vertical free space optical (FSO) links. Spatial diversity based MIMO FSO systems could be used to mitigate atmospheric fading issues. However, the increased number of channels can cause additional pointing error in pointing, acquisition and tracking (PAT) systems. The statistical misalignment model for detecting misalignment error is derived from the multiple transceivers. For the bi-directional characteristics of non-terrestrial back-haul networks, transmission performance is down-leveled to the worse in the asymmetric MIMO configuration of transceivers. The symmetric structure can mitigate the effect of increased pointing error to improve transmission performance. The proposed technique can be applied to the design of power-efficient FSO systems for non-terrestrial wireless back-haul networks.

Long-term environmental exposure of darkness induces hyperandrogenism in PCOS via melatonin receptor 1A and aromatase reduction.

Polycystic ovary syndrome (PCOS) is a common and complex disorder impairing female fertility, yet its etiology remains elusive. It is reported that circadian rhythm disruption might play a crucial role in PCOS pathologic progression. Here, in this research, we investigated the effect of environmental long-term circadian rhythm dysfunction and clarified its pathogenic mechanism in the development of PCOS, which might provide the targeted clinical strategies to patients with PCOS. Female SD rats were used to construct a circadian rhythm misalignment model with constant darkness (12/12-h dark/dark cycle), and the control group was kept under normal circadian rhythm exposure (12/12-h light/dark cycle) for 8 weeks. We measured their reproductive, endocrinal, and metabolic profiles at different zeitgeber times (ZTs). Different rescue methods, including melatonin receptor agonist and normal circadian rhythm restoration, and in vitro experiments on the KGN cell line were performed. We found that long-term darkness caused PCOS-like reproductive abnormalities, including estrous cycle disorder, polycystic ovaries, LH elevation, hyperandrogenism, and glucose intolerance. In addition, the expression of melatonin receptor 1A (Mtnr1a) in ovarian granulosa cells significantly decreased in the darkness group. Normal light/dark cycle and melatonin receptor agonist application relieved hyperandrogenism of darkness-treated rats. In vitro experiments demonstrated that decreased MTNR1A inhibited androgen receptor (AR) and CYP19A1 expression, and AR acted as an essential downstream factor of MTNR1A in modulating aromatase abundance. Overall, our finding demonstrates the significant influence of circadian rhythms on PCOS occurrence, suggests that MTNR1A and AR play vital roles in pathological progression of hyperandrogenism, and broadens current treatment strategies for PCOS in clinical practice.

Experimental and Numerical Study on Mixed Lubrication Performance of Journal Bearing Considering Misalignment and Thermal Effect

The shaft misalignment under mixed lubrication is an important factor affecting the running performance of the bearing, which can occur under heavy load and unsatisfactory assembly. This paper presents a misaligned journal mixed lubrication model coupling for the asperity contact effect, elastic deformation, viscosity–temperature, and viscosity–pressure effect. The finite difference method was employed to calculate the model, and an experimental apparatus designed in this paper was used to test the friction and temperature characteristics of the specimens. The results show that the pressure field, film thickness, and elastic deformation of the bearing conformed to asymmetric distribution along the axial direction under misalignment conditions and there was a notable end side effect. In addition, the frictional force and side leakage flow were evidently enhanced with the increase in the inclination angle in a certain range. The experimental results showed that there was a visible wear phenomenon on the end sides of the bush and shaft. The research results are beneficial for understanding the mixed lubrication mechanism of misaligned journal bearing.

Minimizing Misalignment Effects in Finite Length Journal Bearings

This paper focuses on a method to reduce the detrimental effects that occur due to the misalignment in journal bearings by approaching it with the more complete model of a finite length bearing. Such a drawback is quite common in industrial applications, and it is generally accepted that misalignment causes a significant thinning in the film thickness in the area that is close to the bearing edges. Therefore, removing a certain volume of material from the inner surface of the bearing (bushing) over a distance that is at the bearing edges provides an additional clearance to compensate for the clearance reduction that is due to misalignment. A numerical solution that is used in this work is based on the finite difference method where the Reynolds boundary conditions are considered in the solution scheme, thereby, using an iterative procedure to identify the cavitation zone. A three-dimensional misalignment model is incorporated in the solution in order to provide a more realistic presentation of the deviations and errors that there are in comparison with the ideal aligned case. It has been found in the present work that the edge modification increases the thickness of the lubricant layer considerably and reduces the pressure spikes that are associated with the presence of misalignment. The suggested design also reduces the coefficient of friction in comparison with that of the misaligned case. Furthermore, this method helps in reducing the asymmetry of the hydrodynamic pressure field that results from the misalignment. This method enables the operation of journal bearings over a wider range of misalignment levels without sacrificing the load-carrying capacity of the bearing by maintaining a relatively thicker layer of lubricant at the critical positions that are not so due to the effects of misalignment.

Estimation and performance analysis of multiple incident beam misalignment in spatial diversity based FSO transmissions

A novel approximated misalignment model of an alignment error with multiple incident beams in the position detection of the pointing, acquisition, and tracking (PAT) system is developed for spatial diversity based free-space optical (FSO) communication system. A centroid algorithm used in position detection of the incident beam to align transceivers for the PAT system can make additional pointing errors when multiple beams are incident on the position detector. The centroid algorithm measures the alignment errors through the ratio of the segmented received powers from the position detector. Therefore, the distant arrangement of transmitters and the atmospheric fading affect the alignment error, and the pointing loss of FSO communication increases. We propose a statistical misalignment model with multiple incident beams and analyze the transmission performance using this model to achieve power-efficient FSO communication. The optimum beam width with the misalignment model can reduce the transmit power required to satisfy system demands and outage probability with redundant power for reliable FSO communication.

A Tb/s Indoor MIMO Optical Wireless Backhaul System Using VCSEL Arrays

In this paper, the design of a multiple-input multiple-output (MIMO) optical wireless communication (OWC) link based on vertical cavity surface emitting laser (VCSEL) arrays is systematically carried out with the aim to support data rates in excess of 1 Tb/s for the backhaul of sixth generation (6G) indoor wireless networks. The proposed design combines direct current optical orthogonal frequency division multiplexing (DCO-OFDM) and a spatial multiplexing MIMO architecture. For such an ultra-high-speed line-of-sight (LOS) OWC link with low divergence laser beams, maintaining alignment is of high importance. In this paper, two types of misalignment error between the transmitter and receiver are distinguished, namely, radial displacement error and orientation angle error, and they are thoroughly modeled in a unified analytical framework assuming Gaussian laser beams, resulting in a generalized misalignment model (GMM). The derived GMM is then extended to MIMO arrays and the performance of the MIMO-OFDM OWC system is analyzed in terms of the aggregate data rate. Novel insights are provided into the system performance based on computer simulations by studying various influential factors such as beam waist, array configuration and different misalignment errors, which can be used as guidelines for designing short range Tb/s MIMO OWC systems.