Body Sections Research Articles

Improved Adaptive Butterfly Subdivision Algorithm and Its Application in 3D Geological Modeling

It is of great significance in the fields of 3D modeling, geological engineering and oil and gas storage. This paper mainly studies the improved adaptive butterfly subdivision algorithm and its application in 3D geological modeling. After the geological body section is created, the surface model can be constructed by connecting the sampling points on the contour line of adjacent sections with triangular patches according to the improved adaptive butterfly subdivision algorithm, and then the construction of the geological body model is realized by connecting the strata blocks with the same attributes on the adjacent sections. In this paper, the contour algorithm is used to generate the volume element surface. In this paper, the regular grid interpolation data is generated by butterfly subdivision algorithm using borehole data with multi-layer geological information. After all the simplexes in a 3D geological modeling area are generated, the complex body or complex to which the simple body belongs and the complex body to which the complex body belongs can be assigned. So far, the geological body simulation of 3D modeling area has been completed. Experimental data show that the total execution time of the algorithm is less than 20s. The results show that the improved butterfly subdivision algorithm can improve the accuracy and accuracy of the model.

Analysis and identification of body features in Alzheimer’s patients for gait recognition and gait attractiveness

Alzheimer’s infection is a degenerative mind malady and the most well-known reason for dementia [1, 2]. There has been a lot of past research on which substantial highlights are generally significant in gait investigation. The essential objective of the examination revealed here was to adopt a diagnostic strategy to addressing these inquiries, with regards to recognizing the highlights that are generally significant for gait acknowledgment and gait allure assessment. We dissected the relative movements from various body sections to a root marker of 30 guys by the fixed root strategy. The lower left arm, hips and lower legs were distinguished as significant highlights for gait acknowledgment. The lower legs were perceived as significant highlights for gait allure assessment. Three diverse extraction strategies were applied to accomplish gait marks. In extra, stride appeal was broke down by means of Principle component analysis and linear regression strategy.

ТРЕХМЕРНОЕ МОДЕЛИРОВАНИЕ КАК СИСТЕМА ОТОБРАЖЕНИЯ СУММАРНОГО ХИМИЧЕСКОГО ЗАГРЯЗНЕНИЯ ПОЧВ

The method of three-dimensional model in the system of computer modeling MathCad and Autodesk 3ds Max by categories of total soil pollution is developed. A visualization block and an analytical block have been developed which are based on calculated mathematical models for analyzing and evaluating the environmental situation, risks, and environmental safety of the territory. Three-dimensional models of relief mapping of the Pekhorka river fl oodplain are constructed by integrating them with the help of a programming environment and optimized 3D modeling programs. Three-dimensional models with total soil contamination for water body sections are constructed. On the example of some sections of the catchment area of the Pekhorka river in the Balashikha region, models with soil contamination by the total ZC indicator were created. The development of 3D modeling techniques allows you to create predictive scenarios more accurately with a high degree of detail, as well as quickly approach the solution of environmental problems. Optimization of three-dimensional modeling in the fi eld of problems related to the catchment area contributes to the further operational solution of problems of rational land use and improvement of the environmental situation.

Evaluation of ultrasonic cleaning process

Purpose. To establish relationship between intensity of ultrasonic cleaning and an ultrasonic response fixed at a set point. To determine the influence of liquid contamination on this signal. To specify parameters of an ultrasonic signal to evaluate the course of cleaning a preset section of a body. To define limiting values indicating efficiency of ceasing the cleaning process. Methodology. The research is based on simulation of ultrasonic wave propagation in the heterogeneous environment and subsequent analysis of the signals by using software. Findings. Dependences are established to form evaluation of the course of the cleaning process by parameters of the ultrasonic response. It is found that both the bodys state and that of the liquid affect the ultrasonic response obtained by the sensor at the set point during ultrasonic cleaning. With high contamination (>30%) the state of the liquid becomes a critical factor for forming the signal of the ultrasonic response. With that, there is an abrupt reduction of threshold signal arrival time and increase in the main amplitude, which is to be one of indicators of ceasing the cleaning process in case of its inefficiency. With lower contamination, suspended contaminant particles only correct the signal to some extent without distorting it. There is a relationship between reduction of contamination, the arrival time of threshold signal, on the one hand, and the value of the main amplitude and the 2nd and 3rd-order nonlinearity coefficients, on the other hand. The arrival of the threshold value of the signal is the major parameter determining intensity of cleaning, i.e. reduction of contaminant thickness, which is determined by the value of the main amplitude of the signal and the 2nd and 3rd-order nonlinearity coefficients. Originality. For the first time, methods for evaluating the course of the ultrasonic cleaning process by analyzing ultrasonic responses at a specified point have been developed. Practical value. To consider spatial distribution of the ultrasonic cleaning process, its control is to be based on evaluating the bodys contamination in several preset points. To implement this, the character of dependences between changes in contamination of the body section and parameters of the fixed ultrasonic response is determined. Impacts are considered of suspended contaminant particles in the liquid on the signal analyzed. The observed relationship will provide the basis for building the spatially distributed control over ultrasonic cleaning considering the cleaned bodys state.

Whole-Body MRI and Whole Body [123I]-I-mIBG Scintigraphy: a Comparison in Intermediate and High Risk Neuroblastoma and validation of SIOPEN Scoring System in WB-MRI

Purpose: To assess the agreement between 123I-metaiodobenzylguanidine or [123I]-I-mIBG and Whole Body Magnetic Resonance Imaging with diffusion-weighted whole-body imaging with background body signal suppression (WB MRI-DWIBS) in High and Intermediate risk Neuroblastoma, a retrospective review was performed on [123I]-I-mIBG and DWIBS paired scans acquired at diagnosis, response-to-therapy, after-surgery, off therapy and after relapse with systemic involvement, and osteo-bone marrow metastatic load was evaluated for each of them. Methods: 80 paired [123I]-I-mIBG and DWIBS scans were acquired for 31 patients between June 2009 and June 2019 within 30 days and without intercurrent therapy. SIOPEN Semi-quantitative Scoring Systems for NB with 12 body sections was applied at whole body MIBG and WB MRI-DWIBS acquired to evaluate the skeletal disease extent. In each case thoracic-abdominal SPECT was used to confirm or exclude doubtful scintigraphic alterations. We evaluated specificity, sensitivity, overall accuracy, positive predictive value (PPV) and negative predictive value (NPV) of WB MRI-DWIBS respect [123I]-I-mIBG scintigraphy considered as gold standard. The inverse theoretical statistic exercise was performed for [123I]-I-mIBG respect DWIBS results. Results: DWIBS and [123I]-I-mIBG images were concordant in 890 out of the 960 analyzed segments, with high agreement between the two techniques (Kendal=0.85 P < 0.0001 and Chi 536.5975 P < 0.0001). Considering [123I]-I-mIBG as gold standard, WB MRI-DWIBS overall accuracy was 93%, sensitivity 78%, specificity 95%, PPV 77% and NPV 96%. Otherwise, on the theoretical statistic exercise, [123I]-I-mIBG overall accuracy was 93%; sensitivity 77%; specificity 97%; VPP 78%; VPN 95%, respect DWIBS. [123I]-I-mIBG and WB MRI-DWIBS SIOPEN scoring resulted superimposable (Rho Spearman=0.88, P < 0.0001). Conclusion: DWIBS and [123I]-I-mIBG images showed a very high concordance: a first validation of SIOPEN Scoring System seems possible on the basis of these data. WB MRI may represent an alternative in weak-avid MIBG tumors and for follow up assessment. A multimodal imaging protocol is proposed for High and Intermediate Risk protocols.

A new type of improved four-node DKT thin-shell element and the improvement research on the fast algorithm for bus rollover collision

To solve the problem of seriously element wrap during the finite element analysis process of bus rollover collision, the wrap modification improvement of a new type of four-node DKT (Discreted Kirchhoff Theory) thin-shell element is carried out. The new type of improved four-node DKT thin-shell element is applied to the one-step algorithm for bus rollover collision, and the rollover collision simulation is carried out for the typical bus body section of a 12-m bus body structure. The simulation result is compared with the original one-step algorithm for bus rollover collision. The result shows that the simulation efficiency of the improved one-step algorithm for bus rollover collision is about 50% higher than that of the original algorithm, and the computational precision is increased by about 3.2%. The effectiveness of actual engineering application of the new type of improved element is verified in the end.

Calculation Method of Bonding Section of Joint Surface of Dangerous Rock Mass Based on Amplitude Ratio

In this study, through an analysis of vibration response characteristics of joint surface stiffness on dangerous rock mass, the relationship formula between amplitude ratio of the dangerous rock mass to the bedrock and the length of the bonding section of the joint surface is determined. The stability of the rock mass can be evaluated by combining the formula with the existing rock-mass limit equilibrium theory. This study proposes the existence of a resonance bonding length for the dangerous rock mass. When the length of the bonding section reaches the resonance bonding length, the dangerous rock mass has the largest response to the bedrock vibration. The study found that when the length of the bonding section of the dangerous rock mass is longer than the resonance bonding length, the amplitude ratio increases with the decrease of the bonding section and increases with the increase of the vibration frequency of the bedrock. When the length of the bonding section of the dangerous rock body is shorter than the resonance bonding length, the amplitude ratio decreases with the decrease of the bonding section and decreases with the increase of the vibration frequency of the bedrock. Indoor experiments were conducted by collecting the vibration time-history curves of rock blocks and stone piers and performing analysis and calculation, which proved the accuracy of the analytical results. Through the amplitude ratio of the dangerous rock mass and the bedrock, the bonding length can be calculated. This method can improve the calculation accuracy of the stability coefficient K of the dangerous rock mass.

Collecting Deer Keds (Diptera: Hippoboscidae: Lipoptena Nitzsch, 1818 and Neolipoptena Bequaert, 1942) and Ticks (Acari: Ixodidae) From Hunter-Harvested Deer and Other Cervids.

Deer keds (Diptera: Hippoboscidae: Lipoptena Nitzsch, 1818 and Neolipoptena Bequaert, 1942) are blood-feeding ectoparasites that primarily attack cervids and occasionally bite humans, while ticks may be found on cervids, but are more generalized in host choice. Recent detection of pathogens such as Anaplasma and Borrelia in deer keds and historical infections of tick-borne diseases provides reason to investigate these ectoparasites as vectors. However, previous methods employed to sample deer keds and ticks vary, making it difficult to standardize and compare ectoparasite burdens on cervids. Therefore, we propose a standardized protocol to collect deer keds and ticks from hunter-harvested deer, which combines previous methods of sampling, including timing of collections, dividing sections of the deer, and materials used in the collection process. We tested a three-section and a five-section sampling scheme in 2018 and 2019, respectively, and found that dividing the deer body into five sections provided more specificity in identifying where deer keds and ticks may be found on deer. Data from 2018 suggested that deer keds and ticks were found on all three sections (head, anterior, posterior), while data from 2019 suggested that more Ixodes scapularis were found on the head and deer keds were found on all body sections (head, dorsal anterior, dorsal posterior, ventral anterior, and ventral posterior). The protocol provides an efficient way to sample deer for deer keds and ticks and allows researchers to compare ectoparasite burdens across geographical regions. Furthermore, this protocol can be used to collect other ectoparasites from deer or other cervids.

Shape Optimization of the Cross-Section for Noncircular Hypersonic Missile Forebody

In the hypersonic regime, noncircular missiles have attracted significant attention from researchers. The paper first summarizes the development and present situation of the noncircular missiles at home and abroad. Previous research found that the cross-section shape of missiles has a direct influence on the aerodynamics performance. To find the best cross-section shape in terms of lift-drag-ratio, an efficient and robust shape optimization framework is developed. Class/shape function transformation (CST) method and power-law curve are introduced to complete the parametric modeling of the noncircular missile. The evolutionary algorithm has been utilized to improve the optimization efficiency. A combination of script and journal files is written to automate the CAD loft, mesh generation, and CFD simulations process. Finally, the forebody section of a missile body is chosen as an example to deliver the whole optimization steps. The optimization results show that the lift-to-drag ratio increases from 1.8 to 2.4 when the hypersonic missile forebody cruises at the design condition. The results also demonstrate that the optimized configuration has a better aerodynamic performance than the original one over a wide speed range from Mach 2 to 8 and a wide attack of angle range from 0 to 30.

Semi-analytical study on regular sea wave interaction with circular elastic floaters of aquaculture fish cages

In this paper, a semi-analytical model was developed to find the vertical motions and wavefield around elastic circular floaters of aquaculture fish cages in regular waves. The fluid is assumed inviscid, incompressible, and irrotational flow. A regular train of deep water waves was incident to a floater, which consist of two tori of high-density polyethylene (HDPE) pipes. The problem was analyzed with the assumption of the relatively large incident wavelength in comparison to the cross-section of tori. Slender body theory and matched asymptotic expansions were used with the inner solution close to the body section composed of suitable radiation solution at large distance of floater by distributing source and doublet along centerlines of floater constituent tori. In this approach, the fundamental solutions were developed for symmetric and anti-symmetric motions. Then, the governing equations on diffraction and incident waves were decomposed to Fourier modes of these solutions. The main influence parameters on vertical accelerations such as floater dimensions, wave number, the distances between tori, and bending stiffness of floater were studied. The model results demonstrate good agreement with those of the BEM. Furthermore, the Energy Transmission Index (ETI) was introduced for describing the effect of the floater on the downstream environment.

Performance enhancement of a two-phase closed thermosyphon with a vortex generator

This study focuses on improving the heat transfer performance of a two-phase closed thermosyphon by altering the geometry of a typical straight pipe thermosyphon body. Here, a vortex generating obstacle positioned in the pipe body augments the flow path of the liquid-vapour fluid mixture. This flow augmentation induces a thermal boundary layer mixing effect, which enhances the convection heat transfer within the system under thermal loading. A multiphase numerical simulation model is developed to simulate the fluid phase change and wall temperature distribution of a two-phase closed thermosyphon. The Lee model is adapted to calculate mass and energy transfer source terms during the condensation and evaporation phase-change processes, while the Volume of Fluid method is employed to track liquid-vapour interface movement. The analysis of the new design reveals that the vortex generator has the most significant impact on average wall temperature distribution and overall thermal resistance when it is positioned in the adiabatic section and condenser section of the thermosyphon body. The reduction in thermal resistance is 3.5% and 3.3% when positioned in these two sections, respectively. This reduction corresponds to a higher velocity of the liquid-vapour mixture flow in these regions, indicating that thermal boundary layer mixing can be most enhanced in regions where the liquid-vapour mixture flow velocity has a higher magnitude.

Location and course of the mandibular canal in dentate patients: morphometric study using cone-beam computed tomography.

The morphometric characteristics of the mandibular canal (MC) may vary according to the characteristics of the population studied. Correct location of the MC is fundamental for the indication and planning of different dental treatments, and it is therefore essential to have clinical parameters indicating its approximate location. The aim of this study was to describe the location and course of the MC by morphometric relations in the mandibular body, from the mental foramen to distal of the first molar, in dentate adult patients. We analysed 55 cone-beam computed tomography (CBCT) of male and female patients, aged over 18 years and with fully dentate to the first molar. In each CBCT we selected five coronal sections (A-E) of the mandibular body at different levels using the teeth as references. We determined different morphometric measurements in each section to relate the MC with the corticals of the mandibular body (m1, m2, m3, m4), their orientation to lingual (F) and the thickness of the mandibular corticals (B1, B2 and B3). The distance between the MC and the alveolar crests was greater in males than in females in all the sections. In general, in all the hemiarches, the MC courses away from the vestibular cortical of the mandible (and in some cases significantly towards the lingual cortical) from anterior to posterior in the mandibular body. In the left hemiarch of dentate females the MC describes a descent in the molar zone within the mandibular body. Any intervention in the mandible must be carried out with extreme caution to avoid damaging the vasculo-nervous bundle which passes through the MC. Cone-beam computed tomography is the best tool currently available for the planning and execution of surgical procedures, and is the only tool in clinical use which allows the precise course of the MC to be identified.

Semi-analytical and experimental study on array of elastic circular floaters vertical motions in regular sea waves

In this paper, a semi-analytical method was developed to find the vertical accelerations of array of semi-submerged elastic circular floaters in regular waves. In this process, it was assumed that the fluid is inviscid, incompressible, and irrational flow. Furthermore, incident wavelength was relatively large in comparison to the floaters cross-section. Using slender body theory and matched asymptotic expansions, the inner solution close to the body section composed of suitable radiation solution at large distance from floaters. By this method, the governing equation on the diffracted wave of each floater was expressed as a simple function of Fourier modes of incident waves. Finally, using linear wave theory, the relationship between the incident, radiated, and diffracted waves on an array of floaters was established in Fourier modes. The model results demonstrate good agreement with those of the boundary element method. A series of experimental tests were also performed for model validation. The results show that as the wavenumber increases, the floater hydro-elastic interaction is becoming important. Furthermore, the floaters on upstream have larger significant vertical motions in comparison to a single floater in waves.

Dermal exposure assessment to trinexapac-ethyl: a case study of workers in golf course in Hawaii, USA.

Trinexapac-ethyl (TE) was more widely used in golf course worldwide. As a plant growth regulator, it inhibited grass development and delayed grass cutting date. Direct contact with TE by workers that handle and apply these agents can lead to harmful effects depending on the exposure dosage and duration. Many studies have focused on the growth regulation of TE in plants, while its health risks to human beings were rarely reported. Here, we investigated the risk assessment of workers directly dermal exposed to TE by using some absorbent paper patches. The exposure intensity (EI) and potential dermal exposure (PDE) of worker body sections were obtained, and different exposure patterns were compared. The EI of each body section among mixing/loading, hand-held power sprayer, and manual sprayer workers was ranging from 7.22 to 73.0 pg cm-2. The maximum EI of TE was found on hands of manual sprayers, while the minimum EI of TE was recorded on upper arms of mixing and loading workers. The maximum contribution sections was 29% for the chest and back from mixing/loading workers, 40% for the chest and back from hand-held power sprayers, and 32% for the thigh from manual sprayers. The unit weight potential dermal exposure (UWPDE) of hand-held power sprayers was 60% lower than that of manual sprayers, indicating that hand-held power sprayers were safer than those of manual sprayers. These findings revealed that trinexapac-ethyl posed relatively higher exposure risks to manual sprayer workers than other operator workers in golf course, mainly responsible for body sections of the chest and back and thigh.

A Review of RPPVSM based Skin Identification Techniques

In recent times, most work on suspect detection, medical science and meteorology has been committed towards image processing. This paper deals with several biometric characteristics, including face recognition, finger knuckle, RPPVSM, vein pattern, and fingerprint. RPPVSM differs from the birthmark, because it is genetic but RPPVSM can be genetic or obtained. The two main parts of RPPVSM are detection and Matching. A duplicate evidence therefore creates a vein pattern unlikely. In contexts in which images of evidence may display non-facial body sections of offenders or criminals such as child sexual assault or conflict, relatively permanent Pigmented or Vascular Skin Marks (RPPVSM) have recently been adopted as biometric recognition attribute. In certain cases, Face Detection is hard to recognize individuals because adequate facial details are not sufficient. The recognition of manual RPPVSM is exhausting and time - intensive.

MDixon-based synthetic CT generation via transfer and patch learning

We propose a practicable method for generating synthetic CT images from modified Dixon (mDixon) MR data for the challenging body section of the abdomen and extending into the pelvis. Attenuation correction is necessary to make quantitatively accurate PET but is problematic withPET/MR scanning as MR data lack the information of photon attenuation. Multiple methods were proposed to generate synthetic CT from MR images. However, due to the challenge to distinguish bone and air in MR signals, most existing methods require advanced MR sequences that entail long acquisition time and have limited availablity. To address this problem, we propose a voxel-oriented method for synthetic CT generation using both the transfer and patch learning (SCG-TPL). The overall framework of SCG-TPL includes three stages. Stage I extracts seven-dimensional texture features from mDixon MR images using the weighted convolutional sum; Stage II enlists the knowledge-leveraged transfer fuzzy c-means (KL-TFCM) clustering as well as the patch learning-oriented semi-supervised LapSVM classification to train multiple candidate four-tissue-type-identifiers (FTTIs); Stage III synthesizes CT for new patients’ mDixon images using the candidate FTTIs and voting principle. The significance of our method is threefold: (1) As the global model for patch learning, guiding by the referenced knowledge, KL-TFCM can credibly initialize MR data with overcoming the individual diversity. As the local complement, LapSVM can adaptively model each patch with low time and labor costs. (2) Jointly using the transfer KL-TFCM clustering and patch learning-oriented LapSVM classification, SCG-TPL is able to output accurate synthetic CT in the abdomen. (3) SCG-TPL synthesizes CT only using easily-obtainable mDixon MR images, which greatly facilitates its clinical practicability. Experimental studies on ten subjects’ mDixon MR data verified the superiority of our proposed method.

Introduction to Privacy and Compliance for Consumers (v2)

This article is the first of several sections of the IDPro Body of Knowledge that address Privacy and Compliance for Consumers. This introductory section sets the foundation for subsequent sections on privacy within the IDPro Body of Knowledge, providing an overview of a variety of topics, including definitions of privacy, different approaches to privacy in the consumer sector versus the workforce environment, and more.

Wind tunnel tests on the aerodynamic characteristics of vehicles on highway bridges

Accurately quantifying the aerodynamic forces acting on vehicles and long-span bridges is critical for assessing the safety of moving vehicles on bridges which are subjected to strong wind. It is necessary to consider the aerodynamic interference between vehicles and the bridge, especially for this with the bluff body section and wind barriers. However, very few investigations have been carried out to find aerodynamic coefficients of vehicles on a bridge with the bluff body section and considering the effect of wind barrier. This article therefore carried out wind tunnel tests to determine aerodynamic coefficients of container truck on a bridge with a π-cross section and wind barriers. The influence of vehicle position in different road lanes of the bridge deck and the aerodynamic interference between vehicles on the aerodynamic characteristics of the vehicle and the bridge are investigated. Different heights and ventilation ratios of wind barrier are taken into consideration to examine variations of aerodynamic coefficients with different wind barriers. Furthermore, the change mechanism in the aerodynamic coefficients of the vehicles is observed by analyzing the wind pressure distribution on the surface of the vehicles. The test results show that the different lane locations of the vehicle affect the aerodynamic coefficients significantly, as well as the aerodynamic interference between vehicles with transverse arrangement or longitudinal arrangement, especially for the side force coefficient. The existence of wind barrier reduces the side force coefficients of the vehicle remarkably. Such effects also vary with the ventilation ratio and height of wind barrier.

Development of Autonomous Advanced Disinfection Tunnel to Tackle External Surface Disinfection of COVID-19 Virus in Public Places.

This paper describes a robust autonomous disinfection tunnel to disinfect external surfaces of COVID-19 virus such as clothes and open body sections in public places such as airports, office complexes, schools, and malls. To make the tunnel effective and highly efficient, it has been provided with two chambers with three disinfection processes. Due to the multiple processes, the possibility of neutralizing the virus is quite high and higher than other solutions available at this point for this purpose. Chamber 1 sprays the solution of a disinfectant on the person. This solution can be either a dilute solution of approved chemical or any Ayurvedic/herbal disinfectant. Once the person enters chamber 2, he/she is exposed to hot air at 70 °C along with far-ultraviolet C rays (207–222 nm). Both chambers function autonomously by detecting a person in a chamber using ultrasonic sensors. The proposed tunnel is developed under industry–academia collaboration jointly by Technopark@iitk and ALIMCO under the ambit of the Ministry of Human Resources Development and the Ministry of Social Justice and Empowerment, respectively. The tunnel is referred to as the ‘Techno Advanced Disinfection Tunnel’ (TADT).

A high-order fractional step finite volume solver towards prediction of longitudinal distribution of cross-sectional ship roll hydrodynamics

A high-order fractional step finite volume solver is developed with a fractional step method along with an explicit fourth-order Runge–Kutta scheme in solving Navier–Stokes equations. And then the solver is applied to the prediction of the longitudinal distribution of cross-sectional ship roll hydrodynamics. The present development ameliorates the previous high-order finite volume solver [Ocean Eng 180:119–129] in solving the pressure–velocity coupled equation to further enhance its robustness on roll simulation. Firstly, accuracy of the solver is validated by shear-driven cavity flows and a series of roll motions with the available published numerical or experimental results. And its convergency is verified with a grid- and time step-dependence study. Then, a roll simulation on the mid-section of a KVLCC2 is performed; it embodies that the present solver can suppress the force oscillation than the previous one [Ocean Eng 180:119–129]. Finally, harmonic excited roll motions for several cross sections of a KVLCC2 are systematically investigated for cases of different roll amplitudes and frequencies. And longitudinal distributions of roll hydrodynamics and flow structures near the ship hull are analyzed. In results, the present solver enhances the robustness on roll simulation compared with the previous one [Ocean Eng 180:119–129]. Roll hydrodynamic coefficients culminate at sections of the parallel middle body, and decrease gradually towards fore and aft, and then they increase at the bow and stern.