Horizontal And Vertical Research Articles

Age-group-specific associations between adenoid/tonsillar hypertrophy and craniofacial features

BackgroundAge plays an important role in the association between adenotonsillar hypertrophy and craniofacial morphology. This study aimed to analyse the association of adenoid and tonsillar hypertrophy with craniofacial features in different age groups.MethodsLateral cephalograms were obtained from 942 patients aged 6–15 years (433 boys, 509 girls). They were divided into three age groups: 6–9 years (n = 189), 9–12 years (n = 383), and 12–15 years (n = 370). According to the different sites of pharyngeal obstruction, they were classified as control group (CG), adenoid hypertrophy group (AG), tonsillar hypertrophy group (TG) and adenotonsillar hypertrophy group (ATG). Cephalometric measurements were performed on each enrolled participant. Comparisons between groups and correlations between these cephalometric variables and obstruction sites were evaluated.ResultsAt 6–9 years of age, ATG and TG correlated with increased mandibular height (B = 2.2, p = 0.029; B = 2.6, p = 0.042, respectively). At the age of 9–12 years, AG showed a steep growth direction (B = 1.5, p = 0.002), TG showed a higher probability of Class III skeletal pattern (smaller SNB, ANB and SGn/FH, larger Go-Me) and ATG manifested a higher proportion of Class III skeletal pattern. At 12–15 years of age, there was no significant association between cephalometric measurements and pharyngeal lymphoid tissue enlargement.ConclusionsChildren with isolated adenoid hypertrophy have a vertical growth direction at 9–12 years of age. Isolated adenoid hypertrophy correlated with longer mandibular body, more anterior mandible and horizontal skeletal Class III pattern at 6–12 years. Combination of obstructive adenoids and tonsils manifested similarly to children with isolated tonsil hypertrophy.

Comparative evaulation of condylar guidance obtained by digital panoramic radiographic images with that of obtained during jaw relation and try-in using two different interocclusal record material in completely edentulous patients: an in vivo study

Background In completely edentulous patients, maintaining the patient’s temporomandibular joint (TMJ) health and intraoral components is very essential, which can be achieved by an accurate interocclusal record, which can be taken by various materials and also at various stages. Simulation of the temporomandibular joint anatomy and mandibular movements is possible on a semi-adjustable articulator, which is widely used in prosthodontics. Transferring the record on articulator is a critical step in the fabrication of complete dentures, so it should be done precisely to reduce chair side time and also to avoid complications for patients. This study examines which material is more accurate and records which stage gives more precision by comparing the Condylar guidance on radiographs. This is because it is a relatively consistent bony landmark and can be used to correlate with clinical methods in terms of verification. The objective is to determine the inter occlusal records created during the Jaw Relation stage and Try-in using reinforced wax and Polyvinyl siloxane and compare these values to the condylar guidance obtained by orthopantomogram (OPG). Methods Recording the Condylar Guidance value on OPG by tracing the Glenoid fossa, Articular eminence, and the Frankfurt Horizontal Plane. Followed by conventional steps in making complete dentures at jaw relation and try-in stage. We will record values of condylar guidance with the two different Interocclusal record materials. Expected result It will help the clinicians to gain knowledge about obtaining precise condylar inclination angle by using suitable interocclusal record materials. Conclusions This study will help us to obtain condylar inclination, which in turn helps the patient’s satisfaction as it preserves the intraoral components and health of TMJ.

Solutions to insufficient incentives for developing green tourism by travel agencies: government intervention

PurposeThis research aims to develop an improved model with government intervention and find the government policy for developing green tourism to induce the travel agencies have incentives to produce green tourism products.Design/methodology/approachThis research employs Stackelberg game theory to study two travel agencies in the horizontal direction of the tourism supply chain. Two deterministic, price-sensitive linear demand functions are utilized for these two different tourism products to derive possible analytical solutions.FindingsNo travel agency is willing to produce green tourism products without government intervention. The solution proposed in this paper is that a government should subsidize green travel agencies for their production of green tourism products, and create a tax for non-green traditional travel agencies for the production of non-green traditional tourism products. The amount of government subsidies for green tourism products plus the tax on non-green traditional tourism products equals the difference in unit cost of the two products. The travel agency that produces green tourism products has incentive to produce if there is government intervention.Practical implicationsThis paper provides the stakeholders with three practical implications. The first one is that the amount of subsidy for green travel agencies can be paid by taxing non-green ones. This is the optimal solution. The second one for both the tourism sector and government is that technological innovation in cooperation between government and tourism industry such as low-carbon technology is critical to reduce the cost difference between green travel agency products and non-green ones. The third one is that green travel agencies that produce green tourism products can also fulfill their corporate social responsibilities and enhance their social image.Originality/valueThis paper is unique in that it develops a model to resolve the problem of insufficient incentives. In terms of government intervention, this article also considers tax policy in addition to subsidy policy which is different from previous literature.

On Linear Combinations Of Harmonic Mappings Convex In The Horizontal Direction

The process of creating univalent harmonic mappings which are not analytic is not simple or straightforward. One efficient method for constructing desired univalent harmonic maps is by taking the linear combination of two suitable harmonic maps. In this study, we take into account two harmonic, univalent, and convex in the horizontal direction mappings, which are horizontal shears of $\Psi_{m}(z)=\frac{1}{2i\sin \gamma_{m}}\log \left( \frac{ 1+ze^{i\gamma_{m}}}{% 1+ze^{-^{i\gamma_{m}}}}\right),$ and have dilatations $\omega _{1}(z)=z,$ $\omega _{2}(z)=\frac{z+b}{1+bz},$ $b\in (-1,1).$ We obtain sufficient conditions for the linear combination of these two harmonic mappings to be univalent and convex in the horizontal direction. In addition, we provide an example to illustrate the result graphically with the help of Maple.

Station-Keeping Control of Stratospheric Balloons Based on Simultaneous Optimistic Optimization in Dynamic Wind

Stratospheric balloons serve as cost-effective platforms for wireless communication. However, these platforms encounter challenges stemming from their underactuation in the horizontal plane. Consequently, controllers must continually identify favorable wind conditions to optimize station-keeping performance while managing energy consumption. This study presents a receding horizon controller based on wind and balloon models. Two neural networks, PredRNN and ResNet, are utilized for short-term wind field forecast. Additionally, an online receding horizon controller, based on simultaneous optimistic optimization (SOO), is developed for action sequence planning and adapted to accommodate various constraints, which is especially suitable due to its gradient-free nature, high efficiency, and effectiveness in black-box function optimization. A reward function is formulated to balance power consumption and station-keeping performance. Simulations conducted across diverse positions and dates demonstrate the superior performance of the proposed method compared with traditional greedy and A* algorithms.

A meso- to micro-scale coupled model under typhoon conditions considering vortex structure and coriolis effect for wind farms

Accurate simulations of typhoon-induced wind speeds on wind farms are crucial for the refined assessment of typhoon risks in wind turbines. Southeastern coastal area in China is rich in wind resources but is also severely threatened by typhoons. As an extremely destructive weather system with complex structures, the refined near-surface wind fields of typhoons are difficult to simulate by meso-scale models for risk assessment. Therefore, a coupled meso- and micro-scale model under typhoon conditions is proposed to simulate typhoon-induced winds on a wind farm. The Coriolis force is considered in the coupled model to reflect the rotating effect of typhoons caused by the vortex structure. A coupling algorithm based on objective analysis is proposed to construct boundary conditions at the coupling interface, to consider the variation of inflow variables in the vertical and cross-wind directions. Model constants of the two-equation turbulence model are calibrated based on typhoon field observations, to more reasonably simulate typhoons. A validation study is conducted, and the results show that the maximum wind speed on the wind farm simulated by the coupled model exhibits an increased accuracy compared with that of the meso-scale model, where the absolute error decreases by 34%.

Assessment and Validation of Small-Scale Tropospheric Delay Estimations Based on NWP Data

This paper investigates the applicability of the Numerical Weather Prediction (NWP) data for characterizing the gradient of zenith wet delay in horizontal direction observed on short baselines over larger territories. A three-year period of data for an area covering Scandinavia and Finland is analyzed, and maximum gradients during the considered period are identified. To assess the quality of the NWP-based estimates, results for a smaller region are compared with the estimates obtained using Global Navigation Satellite System (GNSS) measurements processed by the GipsyX/RTGx software package (version 2.1) from a cluster of GNSS reference stations. Additionally, the NWP data from 7 to 9 August 2023 covering a period that includes a storm with high rain intensities over Southern Norway leading to sustained flooding are processed and analyzed to assess if the gradient of zenith wet delay in the horizontal direction increases significantly during such events. The results show that maximum gradients in the range of 40–50 mm/km are detected. When comparing NWP-based estimates to GNSS-based estimates, the tropospheric delays show a very strong correlation. The tropospheric gradients, however, show a weak correlation, probably due to the uncertainty in the NWP data exceeding the gradient values. The data captured during the storm show that while the tropospheric delay increases significantly it is difficult to see increases in the gradient of zenith wet delay in the horizontal direction using this data source and resolution.

Periodically modulated solitary waves of the CH–KP-I equation

We consider the CH–KP-I equation. For this equation, we prove the existence of steady solutions, which are solitary in one horizontal direction and periodic in the other. We show that such waves bifurcate from the line solitary wave solutions, i.e. solitary wave solutions to the Camassa–Holm equation, in a dimension-breaking bifurcation. This is achieved through reformulating the problem as a dynamical system for a perturbation of the line solitary wave solutions, where the periodic direction takes the role of time, then applying the Lyapunov–Iooss theorem.

Intelligent identification of defective regions of voids in tunnels based on GPR data

Quantitatively detecting voids behind tunnel linings presents significant challenges in identifying the range of width and depth. This paper develops an innovative method for identifying defective regions of voids based on Ground Penetrating Radar (GPR) data. This method involves three steps: Firstly, the void-identifying-feature-set (VIFS) is constructed by extracting the Amplitude peak (AT), Signal energy (ET), and Amplitude peak of the first intrinsic mode function (IMF1) component (AH) of every A-scan signal. Secondly, the Support Vector Machine (SVM) is utilized to identify defect signals and normal signals, contributing to the width identification of void in the horizontal direction. Thirdly, an innovative Three-Stage-Boundary-Extraction (TSBE) algorithm is proposed to identify the depth range of voids in the vertical direction. Experimental results conducted on both field data and simulated data demonstrated that the Intersection over Union (IOU) value and consumption time of three groups of GPR data (Data I, Data II, and Data V) are 0.739 and 0.888 s, respectively. The average IOU and consumption time of the TSBE algorithm are 0.739 and 0.058 s, respectively.

Evaluating Surgical Accuracy in Bimaxillary Surgery: A Systematic Review and Meta-Analysis of Mandible-First versus Maxilla-First Approaches.

Mandible-first surgery (MdFS) has gained attention as an alternative to the traditional maxilla-first surgery (MxFS) in bimaxillary procedures. Given the distinct sequence of operations between these approaches, evaluating the clinical advantages of MdFS compared to MxFS is crucial for optimizing surgical decision-making. This systematic review and meta-analysis examine intraoperative achievability and postoperative stability between these two surgical approaches. A thorough literature search was performed using PubMed, Embase, Web of Science, and MEDLINE, covering articles published from 2013 to 2023. Studies included were retrospective, prospective, and randomized trials that compared the accuracy and/or stability of MdFS with MxFS. The primary endpoint for the meta-analysis was the standardized mean difference in surgical accuracy for translational movements, with a secondary focus on rotational accuracy. A total of 11 studies encompassing 712 patients met the inclusion criteria. The analysis suggested that MdFS might reduce accuracy in the sagittal dimension (CI, 0.05 to 0.74) but offered greater achievability in the vertical direction (CI, - 0.47 to - 0.07). Additionally, MdFS was associated with a relatively posterior (CI, - 1.18 to - 0.60) and inferior (CI, - 0.64 to - 0.07) positioning of the maxillomandibular complex. Despite certain limitations, our findings indicate that MdFS can achieve clinical outcomes similar to MxFS in terms of both accuracy and stability. However, further researches with larger sample sizes and more rigorous study designs are necessary to validate these conclusions. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of contents or the online Instructions to Authors www.springer.com/00266 .

Attenuation of seismic waves using resonant metasurfaces: A field study on an array of rubber oscillators

Resonant metasurfaces (RMS) have garnered increasing attention as a type of seismic metamaterial for attenuating seismic waves. To date, most research has been limited to numerical simulations with few experimental studies. Here, we first used Comsol Multiphysics to simulate and identify an RMS structure, which is a periodic array of rubber column oscillators, and then conducted a field experiment on a granular layer. The results indicate that our RMS can effectively attenuate seismic waves in both horizontal and vertical directions across an ultra-wide bandgap. Additionally, the RMS demonstrates greater efficiency in attenuating Love waves compared to Rayleigh waves. This observation is well-accounted for by the resonator model we developed. This work demonstrates that even a simple and cost-effective ground-based RMS is capable of mitigating seismic wave-induced vibrations.

Stable and unstable fall motions of plate-like ice crystal analogues

Abstract. The orientation of ice crystals affects their microphysical behaviour, growth, and precipitation. Orientation also affects interaction with electromagnetic radiation, and through this it influences remote sensing signals, in situ observations, and optical effects. Fall behaviours of a variety of 3D-printed plate-like ice crystal analogues in a tank of water–glycerine mixture are observed with multi-view cameras and digitally reconstructed to simulate the falling of ice crystals in the atmosphere. Four main falling regimes were observed: stable, zigzag, transitional, and spiralling. Stable motion is characterised by no resolvable fluctuations in velocity or orientation, with the maximum dimension oriented horizontally. The zigzagging regime is characterised by a back-and-forth swing in a constant vertical plane, corresponding to a time series of inclination angle approximated by a rectified sine wave. In the spiralling regime, analogues consistently incline at an angle between 7 and 28°, depending on particle shape. Transitional behaviour exhibits motion in between spiral and zigzag, similar to that of a falling spherical pendulum. The inclination angles that unstable planar ice crystals make with the horizontal plane are found to have a non-zero mode. This observed behaviour does not fit the commonly used Gaussian model of inclination angle. The typical Reynolds number when oscillations start is strongly dependent on shape: solid hexagonal plates begin to oscillate at Re =237, whereas several dendritic shapes remain stable throughout all experiments, even at Re > 1000. These results should be considered within remote sensing applications wherein the orientation characteristics of ice crystals are used to retrieve their properties.

Ensemble width estimation in HRTF-convolved binaural music recordings using an auditory model and a gradient-boosted decision trees regressor

Binaural audio recordings become increasingly popular in multimedia repositories, posing new challenges in indexing, searching, and retrieval of such excerpts in terms of their spatial audio scene characteristics. This paper presents a new method for the automatic estimation of one of the most important spatial attributes of binaural recordings of music, namely “ensemble width.” The method has been developed using a repository of 23,040 binaural excerpts synthesized by convolving 192 multi-track music recordings with 30 sets of head-related transfer functions (HRTF). The synthesized excerpts represented various spatial distributions of music sound sources along a frontal semicircle in the horizontal plane. A binaural auditory model was exploited to derive the standard binaural cues from the synthesized excerpts, yielding a dataset representing interaural level and time differences, complemented by interaural cross-correlation coefficients. Subsequently, a regression method, based on gradient-boosted decision trees, was applied to the formerly calculated dataset to estimate ensemble width values. According to the obtained results, the mean absolute error of the ensemble width estimation averaged across experimental conditions amounts to 6.63° (SD 0.12°). The accuracy of the method is the highest for the recordings with ensembles narrower than 30°, yielding the mean absolute error ranging between 0.8° and 10.2°. The performance of the proposed algorithm is relatively uniform regardless of the horizontal position of an ensemble. However, its accuracy deteriorates for wider ensembles, with the error reaching 25.2° for the music ensembles spanning 90°. The developed method exhibits satisfactory generalization properties when evaluated both under music-independent and HRTF-independent conditions. The proposed method outperforms the technique based on “spatiograms” recently introduced in the literature.

Research on the Dynamic Leaking and Diffusion Law of Hydrogen-Blended Natural Gas under the Soil–Atmosphere Coupled Model

With the breakthrough in mixing hydrogen into natural gas pipelines for urban use, the widespread application of hydrogen-blended natural gas (HBNG) in energy delivery is imminent. However, this development also introduces significant safety concerns due to notable disparities in the physical and chemical properties between methane and hydrogen, heightening the risks associated with gas leaks. Current models that simulate the diffusion of leaked HBNG from buried pipelines into the atmosphere often employ fixed average leakage rates, which do not accurately represent the dynamic nature of gas leakage and diffusion. This study uses computational fluid dynamics (CFD) 2024R1 software to build a three-dimensional simulation model under a soil–atmosphere coupling model for HBNG leakage and diffusion. The findings reveal that, in the soil–atmosphere coupling model, the gas diffusion range under a fixed leakage rate is smaller than that under a dynamic leakage rate. Under the same influencing factors in calm wind conditions, the gas primarily diffuses in the vertical direction, whereas under the same influencing factors in windy conditions, the gas mainly diffuses in the horizontal direction.

Study of upright patient positioning reproducibility in image-guided proton therapy for head and neck cancers

PurposeTo evaluate the patient’s positioning reproducibility during upright treatment with image-guided adaptive proton therapy (IGAPT) for head and neck cancers. Materials and methods10 head and neck (H&N) patients were treated with gantry-less IGAPT, which includes daily 3D computed tomography (CT) and two 2D kilovoltage radiographs before treatment and weekly 3DCT immediately after irradiation. All procedures were performed in the carbon chair on the 6 degrees of freedom robotic positioner. ResultsPrior to treatment we registered shifts in patient positioning using 3D/3D registration at the imaging isocenter: X = -0.1 ± 3.9 (mean ± standard deviation) mm, Y = −3.7 ± 3.5 mm, Z = 0.5 ± 6.2 mm. The corresponding vector was applied to the robotic positioner to compensate for the registered shifts, after which the patients were moved to the treatment isocenter and the following shifts were obtained there using 2D/3D registration: X = -0.31 ± 1.37 mm, Y = −0.02 ± 1.33 mm, Z = 0.59 ± 1.55 mm. Finally, the weekly follow-up 3D/3D registration showed X = -0.2 ± 1.2 mm, Y = −0.0 ± 1.4 mm, Z = 2.3 ± 2.0 mm. ConclusionsA novel image-guided gantry-less PT facility showed reliable results in terms of patient positioning for H&N cases during clinical trials. This fact confirmed the suitability of using gantry-less PT for H&N treatment. A small, systematic shift in the vertical direction was detected in the follow-up 3D/3D registration. The effect of this shift will be investigated in further studies with pre/post treatment 2D/3D registration. The next phase of the clinical trial of this facility is dedicated to the thorax region.

Darcy-Brinkman Flow of a Micropolar Fluid through an Anisotropic Porous Channel

This study investigates the Darcy-Brinkman flow of micropolar fluid through an anisotropic porous channel, a configuration relevant to various industrial and natural processes involving complex fluid flow. The anisotropy of the porous medium is characterized by its permeability aligned along two principal axes, with one axis forming an angle with the horizontal direction. The model applies no-slip and no-spin boundary conditions at the channel’s impermeable walls. Using a combination of analytical techniques and graphical analysis, we explore how key parameters such as the Darcy number, anisotropy angle, permeability ratio, and micropolar material parameters affect the flow behavior. Results reveal that increasing the anisotropy angle and permeability ratio leads to a reduction in both fluid velocity and micro rotational velocity, while the Darcy number promotes an increase in flow velocity. Additionally, the study discusses the impact of these parameters on shear stress and couple stress at the channel walls. The findings contribute to a deeper understanding of micropolar fluid behavior in porous media, with potential applications in filtration, lubrication, and subsurface fluid dynamics.

Numerical and experimental investigation of film cooling effectiveness distribution predictions that considers the effects of the turbulent Schmidt number

Film cooling is a critical protective cooling technique that is used in gas turbine engines. However, predicting the film cooling effectiveness can be quite challenging due to the complex mixing processes involved. As a result, simulations commonly require experimental validation or modification of their numerical methods. In this study, predictions of film cooling effectiveness distributions were enhanced by an examination of the impact of the turbulent Schmidt number, Sct, on the coolant-covered areas. An existing turbulent viscosity modification method, the MIX model, was utilized to obtain more accurate flow field representations. The definition, physical implications, and role of the turbulent Schmidt number in numerical simulations, along with the principles of the pressure-sensitive paint measurement method, which was used to characterize the film cooling effectiveness, were explored. Both numerical simulations and experimental validation were employed. The study results revealed that small-scale turbulent eddies, which were averaged in the RANS method according to the Sct, critically influenced the mixing between the coolant and the mainstream, thereby impacting the cooling effectiveness. It was also revealed that as Sct decreased, the cooling effectiveness diminished in the streamwise direction but increased in the spanwise and vertical directions, regardless of the momentum ratio value. An Sct value of 0.3 was found to be more suitable than the commonly used value of 0.7, particularly for a low momentum ratio of 0.43. When Sct=0.3, the error in the area-averaged cooling effectiveness was 10 %, while it was 51 % when Sct=0.7. Additionally, an Sct value of 0.3 produced better overall cooling effectiveness distributions. Consequently, an Sct value of 0.3 is recommended for most low-speed and incompressible-flow simulation conditions.

Optimization method of vibration isolation performance of the 6DOF vibration isolation platform based on different configurations

The configuration optimization methods are developed to design the six degree of freedom (6DOF) passive vibration isolation platform with superior isolation performance. According to different position arrangements, various configuration vibration isolation platforms, including the 33 type, 63 type, 66–1 type, and 66–2 type, are designed and systematically analyzed. Through analysis of the geometric characteristics of the configuration platforms, the nonlinear dynamical equations for each configuration vibration isolation platform are established using Hamilton's principle. Utilizing the transmission rate as an evaluation index, the isolation performance of each platform in six directions (three translational and three rotational) is systematically studied. The results indicate that: (a) Through the comparative analysis of different configuration vibration isolation platforms, it can be found that the 66–1 configuration not only has the largest loading capacity but also owns the best isolation performance in the x, y, and γ directions. The 33 configuration has better isolation performance in the z, α, and β directions, while having greater loading capacity; (b) Through configuration optimization, a 6DOF vibration isolation platform can be obtained with high static stiffness in the vertical direction and low dynamic stiffness in other external excitation directions. This kind of HSLDS characteristics will significantly enhance the isolation performance of the vibration isolation platform; (c) Workspace analysis under different configurations reveals that the 66–1 configuration offers the largest workspace in all six directions, followed by the 63 configuration, while the workspaces of the 33 and 66–2 configurations are similar.

Effects of Pressure on Nitrogen Content and Solidification Structure during Pressurized Electroslag Remelting Process with Composite Electrode

The nitrogen content and solidification structure of the 1Mn18Cr18N ingots produced by the customized laboratory‐scale vacuum induction melting furnace and the pressure electroslag remelting furnace (PESR) with novel composite electrode under different pressure and the same power consumption are compared and studied. The results show that there are perfectly uniform radial chromium and nitrogen profiles during the PESR process. The nitrogen uptake reaction in the PESR process with composite electrode takes place on the liquid metal film on the electrode. Nitrogen uptake could be improved by increasing the nitrogen partial pressure. In addition, the basin depth at a pressure of 0.1 and 1.22 MPa is about 41 and 38 mm, the angle of the grains with respect to the vertical axis is 35° and 31°, respectively. The flat metal basin profile resulted from the thermal resistance at the slag–mold interface decreasing with increasing pressure. Primary and secondary dendritic arm spacing (PDAS and SDAS) variations exhibit an increasing and subsequently decreasing the trend as they move further away from the center in a horizontal direction. Both PDAS and SDAS decrease with increasing pressure from 0.1 to 1.22 MPa.

Analysis of corneal surface shape following overnight orthokeratology with different optical zone diameters.

This study analyzed the corneal surface shape following overnight orthokeratology with different optical zone diameters. A total of 82 eyes belonging to 41 myopic children who completed 1 month of the orthokeratology (ortho-k) lens wear at the Eye Hospital of Wenzhou Medical University from January 2022 to January 2023 were retrospectively analyzed. According to the size of the base curve (BC) of ortho-k lens, patients were divided into BC 5.0 and BC 6.0 groups. The changes in decentration distance and corneal refraction of the two groups after the ortho-k lens wear were analyzed. Independent sample t-tests were used to compare these two outcome measures between the two groups. The decentration distance of BC 5.0 group (0.37 ± 0.19 mm) was significantly lower than that of BC 6.0 group (0.49 ± 0.25 mm, t = -2.330, p = 0.022). In the BC 5.0 group, the direction of decentration was superonasal in 3 cases, inferonasal in 2 cases, inferotemporal in 21 cases, and superotemporal in 6 cases. In the BC 6.0 group, the direction of decentration was superonasal in 2 cases, inferonasal in 2 cases, inferotemporal in 27 cases, and superotemporal in 19 cases. The optical zone area (8.19 ± 2.96 mm2) and reverse curve zone area (30.05 ± 6.74 mm2) in the BC 5.0 group were significantly lower than in the BC 6.0 group (10.42 ± 2.03 mm2, t = -4.043, p < 0.001; 38.21 ± 4.77 mm2, t = -6.422, p < 0.001). The change in the rate of refraction in the horizontal direction in BC 5.0 group were significant higher than in BC 6.0 group. Base curve 5.0 mm ortho-k lens is better positioned than BC 6.0 mm lens. A small BC ortho-k forms a smaller optical zone and reverse curve area, which might get a greater aiameter of alignment curve to facilitate positioning better than the traditional BC lens. In addition, a small BC lens increases positive refraction in the peripheral area, resulting in a greater negative pressure than the traditional BC lens.