Determining residuary resistance per unit weight of displacement with Symbolic Regression and Gradient Boosted Tree algorithms

Determining the residuary resistance per unit weight of displacement is one of the key factors in the design of vessels. In this paper, the authors utilize two novel methods – Symbolic Regression (SR) and Gradient Boosted Trees (GBT) to achieve a model which can be used to calculate the value of residuary resistance per unit weight, of displacement from the longitudinal position of the center of buoyancy, prismatic coefficient, length-displacement ratio, beam-draught ratio, length-beam ratio, and Froude number. This data is given as results of 308 experiments provided as a part of a publicly available dataset. The results are evaluated using the coefficient of determination (R2) and Mean Absolute Percentage Error (MAPE). Pre-processing, in the shape of correlation analysis combined with variable elimination and variable scaling, is applied to the dataset. The results show that while both methods achieve regression results, the result of regression of SR is relatively poor in comparison to GBT. Both methods provide slightly poorer, but comparable results to previous research focussing on the use of “black-box” methods, such as neural networks. The elimination of variables does not show a high influence on the modeling performance in the presented case, while variable scaling does achieve better results compared to the models trained with the non-scaled dataset.

The impact of parity and maternal obesity on the fetal outcomes of a non-selected Lower Saxony population

Objectives Maternal obesity during pregnancy is associated with adverse intrauterine events and fetal outcomes and may increase the risk of obesity and metabolic disease development in offspring. Higher parity, regardless of socioeconomic status, is associated with increased maternal body mass index (BMI). In this study, we examined the relationship between parity, maternal obesity, and fetal outcomes in a large sample of mother-neonate pairs from Lower Saxony, Germany. Methods This retrospective cohort study examined pseudonymized data of a non-selected singleton cohort from Lower Saxony’s statewide quality assurance initiative. 448,963 cases were included. Newborn outcomes were assessed in relation to maternal BMI and parity. Results Maternal obesity was associated with an increased risk of placental insufficiency, chorioamnionitis, and fetal distress while giving birth. This effect was present across all parity groups. Fetal presentation did not differ between BMI groups, except for the increased risk of high longitudinal position and shoulder dystocia in obese women. Maternal obesity was also associated with an increased risk of premature birth, low arterial cord blood pH and low 5-min APGAR scores. Conclusions Maternal obesity increases the risk of adverse neonatal outcomes. There is a positive correlation between parity and increased maternal BMI. Weight-dependent fetal risk factors increase with parity, while parity-dependent outcomes occur less frequently in multipara. Prevention and intervention programs for women planning to become pregnant can be promising measures to reduce pregnancy and birth complications.

VARIATION OF THE TECHNOLOGICAL PROPERTIES OF WOOD FROM Ochroma pyramidale IN THE LONGITUDINAL AND RADIAL SENSE OF THE SLEW

The work aimed to characterize the wood of the species Ochroma pyramidale in the longitudinal and radial direction of the tree. For the study, five six-year old trees were used. Discs were removed at different heights of the stem. The samples were obtained from each disk in different regions between the pith and bark. The preparation and the anatomical analysis of the permanent and temporary slides, chemical analyzes, and basic density measure of the stem wood were carried out according to technical standards. As a result, it was observed that the highest averages for pore diameter and fiber length were found in the region close to the bark at all heights. Regarding to the rays, it was noted that there was an interaction between the longitudinal x radial factors for most of the parameters evaluated, except for the width of the rays. For fiber lumen diameter and vessel length, the same trend line was found, the highest average observed in the region close to the pith. In the chemical analyzes, it was possible to observe that there was no significant difference in the longitudinal direction of the wood except for solubility in cold water. For basic density, there was an increase in the region closer to the pith compared to the region closer to the bark. However, in relation to the longitudinal position of the bole, the highest values were found at the base of the bole. It could be seen that the Ochroma pyramidale species has potential use for products linked to thermal and acoustic insulation, production of particleboards and pulp and paper production.

Numerical Simulation of Depth Tracking Control of an Underwater Towed System Coupled with Wave–Ship Interference

This paper presents a numerical study of the depth tracking control for an underwater towed system under wave–ship interference condition. To overcome the laminations of ignoring the hydrodynamic factors and wave–ship interference in the existing simulation model for the depth tracking operation of the underwater towed system, a numerical model combining the control system with the computational fluid dynamics (CFD) method based on the overset mesh technique is explored and constructed; the influence of towing ship and head waves is introduced into the numerical analysis of the underwater towed system; a depth control system based on the center of gravity adjustment is proposed and its control characteristics are discussed. The fluid motion around the towed vehicle and the towing ship is governed by the Navier–Stokes equations, and the overset mesh technique is applied for the numerical solution of the equations. The towing cable connecting the towed vehicle and towing ship is governed by the quasi-steady-state catenary equations. The depth tracking controller adjusting the longitudinal position of a shifting weight is constructed based on the proportional–integral–derivative (PID) algorithm. The simulation results show that the numerical simulation system is practicable, and the depth tracking control system is feasible, effective, and robust.

Understanding the Lateral Dimension of Traffic: Measuring and Modeling Lane Discipline

There is growing interest in understanding the lateral dimension of traffic. This trend has been motivated by the detection of phenomena unexplained by traditional models and the emergence of new technologies. Previous attempts to address this dimension have focused on lane-changing and non-lane-based traffic. The literature on vehicles keeping their lanes has generally been limited to simple statistics on vehicle position while models assume vehicles stay perfectly centered. Previously the author developed a two-dimensional traffic model aiming to capture such behavior qualitatively. Still pending is a deeper, more accurate comprehension and modeling of the relationships between variables in both axes. The present paper is based on the Next Generation SIMulation (NGSIM) datasets. It was found that lateral position is highly dependent on the longitudinal position, a phenomenon consistent with data capture from multiple cameras. A methodology is proposed to alleviate this problem. It was also discovered that the standard deviation of lateral velocity grows with longitudinal velocity and that the average lateral position varies with longitudinal velocity by up to 8 cm, possibly reflecting greater caution in overtaking. Random walk models were proposed and calibrated to reproduce some of the characteristics measured. It was determined that drivers’ response is much more sensitive to the lateral velocity than to position. These results provide a basis for further advances in understanding the lateral dimension. It is hoped that such comprehension will facilitate the design of autonomous vehicle algorithms that are friendlier to both passengers and the occupants of surrounding vehicles.

Carotid total plaque area as a marker of asymptomatic lower extremity arterial disease

Objective: to examine the prognostic value of ultrasound markers of carotid atherosclerosis in relation to the presence of asymptomatic lower extremity peripheral artery disease (PAD). Materials and Methods: the study included 193 patients with carotid atherosclerosis. All patients underwent duplex ultrasound scanning (DUS) of carotid and lower limb arteries. The carotid plaque score (cPS) was determined as the total height of all plaques in the carotid arteries. The carotid total plaque area (cTPA) was estimated in the longitudinal position, the area of plaque was measured in the manual trace mode.Results: asymptomatic lower extremity PAD was diagnosed in 31.6% of patients. The increase in cTPA, in contrast to cPS and the degree of carotid stenosis, was independent predictor of lower extremity PAD and was associated with an increase in the relative risk of its presence by 6.78 times (95% CI 2.48-18.5; p <0.0001). cTPA ≥42.5 mm2 made it possible to diagnose asymptomatic lower extremity PAD with a sensitivity of 70.2% and specificity of 73.0%. Conclusion: In patients with carotid atherosclerosis among carotid atherosclerosis markers only cTPA, in contrast to cPS and the degree of carotid stenosis, had an independent predictive value regarding the presence of asymptomatic lower extremity PAD.

Optimization of Resistance Performance for Inland Twin-Skeg Ship Based on CFD and Surrogate Modeling

With the increasingly serious energy problems in the world and the introduction of Energy Efficiency Design Index (EEDI) by International Maritime Organization (IMO), the application of energy conservation and emission reduction methods in ships has been paid more and more attention. With the rapid development of computational fluid dynamics (CFD), ship hull form optimization based on CFD has become a hot topic, Inland twin-skeg ship has a relatively complicated hull form, and it has strong theoretical significance and engineering practical value to carry out hull form optimization research on this type of ship. Based on the multidisciplinary comprehensive optimization platform for ship hydrodynamic performance (SHIPMDO-WUT) self-developed by Wuhan University of Technology research institute of multidisciplinary design optimization of ship performance, this paper using the hull surface deformation method based on the radial basis function interpolation to change the hull form and skeg shape of a 3000t inland twin-skeg oil tanker with invisible bulbous bow. And the high-precision CFD calculation software SHIPFLOW was used to predict the resistance of this ship. Finally, combined with CFD surrogate model and optimization algorithm, the ship with excellent resistance performance is obtained and ensuring the ship displacement and the longitudinal position of the buoyancy center are within the range of certain constraints. At last, the optimization results were verified numerically.

Exploring the motivations to participate in an online brand community: a study of 7–11-year-old children

Purpose The purpose of this research is to understand what motivates 7–11-year-old children to participate in online brand communities (OBCs). Prior research has concentrated on prescriptive product categories (games and gaming), predominantly adolescent groups and the social aspects of community engagement and actual behaviour within communities, rather than the motivations to participate with the OBC. This has ultimately limited what has been gleaned, both theoretically and managerially, from this important segment. Design/methodology/approach An interpretive, longitudinal position is adopted, using a sample of 261 children (113 male and 148 female) from across the UK, using event-based diaries over a 12-month period, generating 2,224 entries. Findings Data indicate that children are motivated to participate in a brand community for four reasons: to support and ameliorate pre-purchase anxieties, resolve interpersonal conflicts, exact social dominance in terms of product ownership and perceptions of product knowledge and to actively engage in digitalised pester power. The study also reveals that certain motivational aspects such as conflict resolution and exacting dominance, are gender-specific. Research limitations/implications Knowledge of children’s motivation to engage with OBCs is important for marketers and brand managers alike as the data reveal markedly different stimuli when compared to known adult behaviours in the field. Given the nature of the study, scope exists for significant future research. Practical implications The study reveals behaviours that will assist brand managers in further understanding the complex and untraditional relationships that children have with brands and OBCs. Originality/value This study makes a novel examination of a hitherto little-explored segment of consumers. In doing so, it uncovers the theoretical and practical characteristics of child consumers that contemporary, adult-focussed literature does not recognise. The paper makes an additional contribution to theory by positing four new behavioural categories relating to community engagement – dependers, defusers, demanders and dominators – and four new motivational factors which are fundamentally different from adult taxonomies – social hegemony, parental persuasion, dilemma solving and conflict resolution.