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Dynamical vehicle performances depend on its center of gravity's position. It is necessary to determine this position as closely as possible. The current methods of determining the center of gravity's position are either not sufficiently accurate or are very demanding in relation to finances, time and special equipment. At the same time, there is a lack of accurate data on the center of gravity's position of current vehicles for further research. Therefore, the purpose of this study is to propose such a methodology of measuring the center of gravity's position, including its height, which is accurate enough and has as low-demand measuring equipment as possible. Another purpose of this study is to obtain data on the change in the centers of gravity's positions in different vehicles due to various load distributions. Extensive experimental measurements, according to the innovative methodology, were performed with five vehicles. The positions of the center of gravity were determined for various load distributions, and the results were analyzed in detail. [ABSTRACT FROM AUTHOR]

The present note addresses the novel problem of executing complex aircraft maneuvers under considerable center of gravity (c.g.) uncertainties arising from asymmetrical loading or release of payloads, uneven fuel consumption etc. First, the aircraft flight dynamics under predominantly lateral c.g. movement, is approximated and expressed in a block strict feedback form and thereafter an adaptive backstepping controller is proposed to adapt to the c.g. variations. To alleviate the model uncertainty caused by this model approximation and also to provide robustness to aerodynamic uncertainties in high-alpha regions, a sliding mode control is further integrated with the adaptive backstepping control law. Asymptotic stability conditions of the proposed controller are derived from the first principle using Lyapunov's method and Barbalat's lemma. To validate the proposed control scheme, the high-alpha Herbst maneuver is implemented in simulation for the F18-HARV aircraft and the results show that the maneuver performance remains nearly the same under both the nominal and the off-nominal c.g. positions. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Naturalium Universitatis Pekinensis is the property of Editorial Office of Acta Scientiarum Naturalium Universitatis Pekinensis and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Studying long-term precipitation trends is crucial for sustainable development, as the proper utilization of water resources is essential for maintaining a sustainable water supply. The objective and novelty of this paper was to reveal the gradual mutation process of precipitation in China over a century. This study utilized monthly precipitation data from 1901 to 2022 (at a century scale) to analyze and explore the spatiotemporal variability in precipitation across different time scales and regions with a trend analysis, an abrupt change analysis, and gravity center models. The findings indicate that (1) from 1901 to 2022, the precipitation in China generally decreased from the southeast coastal areas toward the northwest inland regions. (2) There were significant differences in the migration of precipitation gravity centers among the different study regions, with the least dispersion being observed in the Liao River basin, while the Hai River basin, various river basins in the northwest, and the Pearl River basin exhibited certain regularities in gravity center movement, and other regions showed periodic variations. (3) Over the period from 1901 to 2022, there was a trend of transitioning from lower to higher precipitation levels. (4) According to continuous long-term abrupt change tests, the timing of precipitation shifts varied across different basins. Precipitation, as a crucial component of natural resources, directly impacts various aspects of socio-economic life. Research findings provide decision support for regional flood control and disaster reduction and offer scientific decisions for ecological security. [ABSTRACT FROM AUTHOR]

An experiment is performed on introducing methane with a syringe at different helium flow rates on a chromatographic column free of adsorbent. It is found that the input signals generated in this case are satisfactorily described by an elution curve equation that is a correct solution to the direct problem of linear adsorption dynamics. A separate example shows that the input signals at the same flow rate coincide with one another quite well. The centers of gravity to the left and right of the input signal's maximum are calculated, considerably expanding its content of information. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive backstepping-based control scheme is proposed to perform autonomous lateral maneuvers under significant lateral offset in the center of gravity (c.g.) position in a UAV. It is first shown that the coupled equations of motion arising from lateral c.g. shift can be simplified and cast in block strict feedback form making it amenable to a two-step backstepping control design. Useful nonlinear terms in the equations of motion are identified and retained in the backstepping design to ensure a less conservative control. Adaptation law is incorporated to dynamically adjust to changes in the c.g. position by adding an adaptive term to each step of the backstepping control. Lyapunov’s direct method and LaSalle’s invariance principle are applied to establish asymptotic stability of both tracking errors and errors in the c.g. estimate. To validate the effectiveness of the proposed control strategy, simulation results for horizontal turn maneuver are presented for the fixed wing Aerosonde UAV and maneuver performance is observed to remain highly insensitive to a wide range of lateral c.g. positions on either side of the fuselage centerline. Furthermore, a comparative control performance analysis is carried out against an ad-hoc model-based adaptive backstepping control scheme available in the literature and the results show significant performance enhancement in the proposed scheme. Along with the c.g. variations, the effects of steady crosswind are also investigated and the control formulation is modified to mitigate these effects too. Real-time control hardware in loop simulations are also provided in support of the real time viability of the proposed control. [ABSTRACT FROM AUTHOR]

The center of gravity (COG) is a crucial concept in both strategic studies and military planning, yet its ambiguous and incoherent nature has repeatedly led to abundant confusion. In particular, its relation to both Clausewitz and the German Schwerpunkt tradition remains poorly understood. This article addresses these shortcomings by tracing both Schwerpunkt and COG in German and US military doctrine, respectively. Comparing the two concepts across several dimensions, the article not only finds that both have evolved considerably over time, but also that while having a common origin, they are ultimately based on different approaches, assumptions, and traditions. [ABSTRACT FROM AUTHOR]

This paper proposes a novel optimization algorithm called center of gravity (CoG). The main idea of CoG is attributing the potential function to a set of particles in problem space and finding the contour lines. With each particle moving with a predefined location in search space, the potential function is defined based on particle's fitness values. The particles are then ranked according to their finesses. Through clustering of particles, the contour line will be constructed which then leads to determining their center of gravity. This process will iteratively continue by updating the particles in each iteration and ultimately achieving the global CoG. The proposed CoG algorithm is shown to be useful for different types of uni-modal to multi-modal benchmark functions. Also, optimizing some important engineering problems has been considered. The performance of this new optimization algorithm has been compared with some of the optimization algorithms. Simulation results confirm that the CoG algorithm provides performance improvement compared to other existing methods in various scenarios. [ABSTRACT FROM AUTHOR]

In an ever-changing environment, detecting shifts in the spatial distribution of marine fish and understanding the relative importance of climate change and biotic factors impacting fish distributions can improve fisheries management. Coincident with the significant increase in Haddock (Melanogrammus aeglefinus) abundance to a historically high levels on Georges Bank (GB) in the last decade, extreme ocean temperature increase was also observed in this region. In this study, the possible seasonal and inter-annual spatial distribution changes of haddock were investigated with >50 years of bottom trawl survey data collected in spring and fall on GB. These data were analyzed using models with spatial, different temporal, and spatio-temporal autocorrelation structures. To characterize the directional changes in haddock spatial distribution, the Center of Gravity (CG) and Area of Occupancy (AO) in each season were estimated from the best model selected by Akaike Information Criteria (AIC). The results showed substantial range expansion/contraction and distribution changes in both spring and fall over time. The relative role of density dependence, age structure, and climate change in affecting haddock distribution was evaluated using a generalized additive model (GAM). It was found that density-dependent habitat selection made the greatest contribution to the variations of AO in both seasons, which is consistent with the MacCall's Basin model theory. Rising ocean temperatures played a major role in shaping a northward distribution shift in fall. GB is the southern edge of haddock distribution in the Northwest Atlantic, continued warming from climate model projections in the next 50 years in this region could make it difficult to define stock boundaries between GB and adjacent Canadian and US domestic management areas. This would subsequently impact fishery management of haddock. [ABSTRACT FROM AUTHOR]

Wheelchairs are the primary means of movement for people with mobility disabilities, regardless of their type of drive. One of the main features of wheelchairs, besides their ability to generate drive, maneuverability, and body support, is their stability of movement. This stability largely depends on the height of the center of gravity in the human-wheelchair system. This parameter is very important from the perspective of wheelchair user safety, especially when overcoming architectural obstacles such as curbs, stairs, or slopes. Currently, many models available on the market have additional protection in the form of support wheels, which prevent the wheelchair from tipping over backwards with the user. However, the use of these support wheels is associated with an increase in the weight and dimensions of the wheelchair, as well as a decrease in ergonomics. Faced with this problem, the authors have set out to present an innovative method for calculating the height of the center of gravity and conducted a series of experimental tests on various wheelchair designs. The research analyzed the displacement of the center of gravity depending on the angle of the inclination of the ground from 0° to 15°. The conclusions obtained regarding stability and the calculation of the center of gravity in relation to maintaining balance can form the basis for designing new wheelchair structures. [ABSTRACT FROM AUTHOR]

This work presents issues related to selected errors accompanying spatial measurements of surface roughness using contact profilometry. The influence of internal heat sources, such as engines or control electronics, on the thermal expansion of the drive responsible for the measurement probe's movement in the X-axis direction was investigated. In terms of starting measurements on a thermally unstable device, the synchronization error of individual profile paths was 16.1 µm. Based on thermographic studies, the time required for full thermal stabilization of this drive was determined to be 6–12 h from when the device was turned on. It was demonstrated that thermal stabilization of the profilometer significantly reduced positioning errors of the measurement probe on the X-axis. Thermal stabilization time should be determined individually for a specific device variant. This research also determined how changes in the center of gravity caused by the measurement probe's movement affected the overall rigidity of the profilometer structure and the leveling of the tested surface. Laser interferometry was used for this purpose. The determined vulnerability of the profilometer structure was 0.8 µm for a measurement section of 25 mm. Understanding the described relationships will reduce errors associated with conducting measurements and preparing equipment for tests. Additionally, it will enable the correct evaluation of surface geometry. [ABSTRACT FROM AUTHOR]

Background: Osteoarthritis is one of the most frequent joint disorders in the world. The specialists in the field strongly support the role of physical exercise as a key component in the holistic management of arthrosis. The aim of the current study was to identify and assess the functional deficit of these patients and to identify means to alleviate it through pre-surgery physiotherapy programs. Methods: The study was conducted on two samples of patients: a witness sample, encompassing 126 subjects without pathologies at the level of their lower limbs, and a study sample, formed of 116 subjects diagnosed with severe gonarthrosis with total knee arthroplasty indication. The assessment protocol was accomplished with the GPS 400 stabilometric platform. Results: The barycenter differences within the support polygon, recorded for the two samples within sagittal deviation, emphasize that the barycenter shifting mainly towards the healthy lower limb will demand, from the individual, more intense rebalancing postural reactions that will place the center-of-gravity projection in the sagittal plane, closer to the central area of the support polygon. Conclusions: In the case of gonarthrosis and other joint disorders, the use of functional testing to assess body weight distribution and center-of-gravity imbalances represents a promising direction in the research on and management of these disorders, providing essential information for functional diagnosing and thus enabling the elaboration and monitoring of individualized functional rehabilitation plans. [ABSTRACT FROM AUTHOR]

As the elderly population increases, independent living for the aged has become essential for extending a healthy life expectancy, and this requires the maintenance of mobility for daily activities, such as standing up and walking. Among these, standing up, a series of movements involved in getting out of a chair or bed, is the starting point of daily activities. Therefore, it is important to clarify the factors that contribute to accomplishing the transition from sitting to standing up. This study attempted to clarify the relationship between motor characteristics and the mechanism of muscle activity involved in the change from sitting to standing up. Specifically, we focused on the activity of the bi-articular muscles involved in the two joints simultaneously rather than joint torque that is the conventional standard for evaluating motion. We probed the mechanistic characteristics of bi-articular muscle activity as well as the main muscles that function during normal standing up motion, namely a natural standing up movement where the trunk is not vertically restricted, using electromyographic analysis, theoretical analysis using a link model based on the muscle arrangement of the lower limb, and experimental analysis using an actual model that reproduces the functions of these muscles to define the muscular activities of the thigh muscles. [ABSTRACT FROM AUTHOR]

While variation in the southern Peninsular Spanish affricate /tʃ/ has been considered in the context of deaffrication to [ʃ], this study examines an emergent variant [ts] in the context of sociolinguistic identity and style in political speech. Based on a corpus of public speech from Madrid and Andalusia, Spain, this study examines the phonetic and sociolinguistic characteristics of the affricate, finding variation in the quality of the frication portion of the segment through an analysis of segment duration (ms), the center of gravity (Hz), and a categorical identification of realization type. The results suggest that both linguistic variables, like phonetic environment, stress, lexical frequency, and following vowel formant height, as well as extralinguistic variables, like speaker city, gender, political affiliation, and speech context, condition use. Based on these findings, it appears that production of the alveolar affricate [ts] is an incipient sociolinguistic marker in the process of acquiring social meaning. It is particularly associated with female speech and prestige norms that transcend regional identification. This alveolar variant serves as an additional sociolinguistic resource accessible for identity development among politicians and offers insight into ongoing change in the affricate inventory of southern and northern-central Peninsular Spanish. [ABSTRACT FROM AUTHOR]

The traditional method of allocating passenger seats based on compartments does not effectively manage an aircraft's center of gravity (CG), resulting in a notable divergence from the desired target CG (TCG). In this work, the Boeing B737-800 aircraft was employed as a case study, and row-based and compartment-based integer programming models for passenger allocation were examined and constructed with the aim of addressing the current situation. The accuracy of CG control was evaluated by comparing the row-based and compartment-based allocation techniques, taking into account different bodyweights and numbers of passengers. The key contribution of this research is to broaden the range of the mobilizable set for the aviation weight and balance (AWB) model, resulting in a significant reduction in the range of deviations in the center of gravity outcomes by a factor of around 6 to 16. The effectiveness of the row-based allocation approach and the impact of passenger weight randomness on the deviation of an airplane's CG were also investigated in this study. The Monte Carlo method was utilized to quantify the uncertainty associated with passenger weight, resulting in the generation of the posterior distribution of the aircraft's center of gravity (CG) deviation. The outcome of the row-based model test is the determination of the range of passenger numbers that can be effectively allocated under different TCG conditions. [ABSTRACT FROM AUTHOR]

When the amphibious vehicle navigates in water, the angle of the anti-wave plate and the position of the center of gravity greatly influence the navigation characteristics. In the relevant research on reducing the navigation resistance of amphibious vehicles by adjusting the angle of the anti-wave plate, there is a lack of scientific selection of parameters and reasonable research of simulation results by using mathematical methods, and the influence of the center of gravity position on navigation characteristics is not considered at the same time. To study the influence of the combinations of the angle of the anti-wave plate and the position of the center of gravity on the resistance reduction characteristics, a numerical calculation model of the amphibious unmanned vehicle was established by using the theory of computational fluid dynamics, and the experimental data verified the correctness of the numerical model. Based on this numerical model, the navigation characteristics of the amphibious unmanned vehicle were studied when the center of gravity was located at different positions, and the orthogonal experimental design method was used to optimize the parameters of the angle of the anti-wave plate and the position of the center of gravity. The results show that through the parameter optimization analysis based on the orthogonal experimental method, the combination of the optimal angle of the anti-wave plate and the position of the center of gravity is obtained. And the numerical simulation result of resistance is consistent with the predicted optimal solution. Compared with the maximum navigational resistance, the parameter optimization reduces the navigational resistance of the amphibious unmanned vehicle by 24%. [ABSTRACT FROM AUTHOR]

Background: Postural sway changes often reflect functional impairments in adults with chronic low back pain (LBP). However, there is a gap in understanding how these individuals adapt their postural strategies to maintain stability. Purpose: This study investigated postural sway distance and velocity, utilizing the center of pressure (COP) and center of gravity (COG), between adults with and without LBP during repeated unilateral standing trials. Methods: Twenty-six subjects with LBP and 39 control subjects participated in the study. Postural sway ranges, COP/COG sways, and sway velocities (computed by dividing path length by time in anteroposterior (AP) and mediolateral (ML) directions over 10 s) were analyzed across three unilateral standing trials. Results: A significant group interaction in sway range difference was observed following repeated trials (F = 5.90, p = 0.02). For COG sway range, significant group interactions were demonstrated in both directions (F = 4.28, p = 0.04) and repeated trials (F = 5.79, p = 0.02). The LBP group demonstrated reduced ML sway velocities in the first (5.21 ± 2.43 for the control group, 4.16 ± 2.33 for the LBP group; t = 1.72, p = 0.04) and second (4.87 ± 2.62 for the control group, 3.79 ± 2.22 for the LBP group; t = 1.73, p = 0.04) trials. Conclusion: The LBP group demonstrated decreased ML sway velocities to enhance trunk stability in the initial two trials. The COG results emphasized the potential use of trunk strategies in augmenting postural stability and optimizing neuromuscular control during unilateral standing. [ABSTRACT FROM AUTHOR]

This study examined the influence of running shoe center of gravity relative position shifting forward and backward in sagittal axis on male amateur runners. Twenty-three adult male runners were recruited through social media with paid to participate in this study. The experimental shoe used was the Li Ning Feidian Challenger 3. Forward center of gravity (FCG), defined as the shoe center of gravity located at 10.8 cm (15% before midpoint) from shoe toe to heel. Intermediate center of gravity (ICG), defined as the shoe center of gravity, is located at 14.8 cm (midpoint) from shoe toe to heel. Backward center of gravity (BCG), defined as the shoe center of gravity, is located at 23.1 cm (15% after midpoint) from shoe toe to heel. Questionnaire collection was used to assess the perception of the center of gravity shifting. Ground contact temporal, peak force/pressure of plantar and kinetics indicators data were simultaneously captured by motion capture system and force platform. Three participants (13.04%) correctly perceived the shoe center of gravity shifting forward and backward simultaneously. Shoes ICG peak force underneath Meta 1 increased significantly than BCG by 7.59% (p < 0. 0 5). Shoes FCG peak force underneath Meta 2 decreased significantly compared to ICG and BCG by 13.62% and 8.96% (p < 0. 0 5). Shoes BCG peak force underneath Meta 5 decreased significantly compared to ICG and FCG by 18.18% and 23.78% (p < 0. 0 5). Shoes FCG peak pressure underneath Meta 2 decreased significantly compared to ICG and BCG by 13.02% and 9.19% (p < 0. 0 5). Shoes FCG peak pressure underneath Meta 2 decreased significantly compared to ICG and BCG by 11.18% and 9.16% (p < 0. 0 5). However, there are no significant differences in kinetic indicators. The findings suggest that a fraction of participants can correct perceived shoe center of gravity shifting. Shoes' FCG reduces force and pressure in the middle metatarsal regions. Shoes' BCG reduces force in the lateral and medial metatarsal region. Healthcare professionals can optimize the design of footwear accordingly to improve rehabilitation outcomes and reduce injury risks in runners. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South-Central Minzu University (Natural Science Edition) is the property of Journal of South-Central Minzu University (Natural Science Edition) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Miniaturized fiber-Bragg-grating (FBG) interrogators are of interest for applications in the areas where weight and size controlling is important, e.g., airplanes and aerospace or in-situ monitoring. An ultra-compact high-precision on-chip interrogator is proposed based on a tailored arrayed waveguide grating (AWG) on a silicon-on-insulator (SOI) platform. The on-chip interrogator enables continuous wavelength interrogation from 1 544 nm to 1 568 nm with the wavelength accuracy of less than 1 pm [the root-mean-square error (RMSE) is 0.73 pm] over the whole wavelength range. The chip loss is less than 5 dB. The 1 × 16 AWG is optimized to achieve a large bandwidth and a low noise level at each channel, and the FBG reflection peaks can be detected by multiple output channels of the AWG. The fabricated AWG is utilized to interrogate FBG sensors through the center of gravity (CoG) algorithm. The validation of an on-chip FBG interrogator that works with sub-picometer wavelength accuracy in a broad wavelength range shows large potential for applications in miniaturized fiber optic sensing systems.

Dynamical vehicle performances depend on its center of gravity’s position. It is necessary to determine this position as closely as possible. The current methods of determining the center of gravity’s position are either not sufficiently accurate or are very demanding in relation to finances, time and special equipment. At the same time, there is a lack of accurate data on the center of gravity’s position of current vehicles for further research. Therefore, the purpose of this study is to propose such a methodology of measuring the center of gravity’s position, including its height, which is accurate enough and has as low-demand measuring equipment as possible. Another purpose of this study is to obtain data on the change in the centers of gravity’s positions in different vehicles due to various load distributions. Extensive experimental measurements, according to the innovative methodology, were performed with five vehicles. The positions of the center of gravity were determined for various load distributions, and the results were analyzed in detail.

Miniaturized fiber-Bragg-grating (FBG) interrogators are of interest for applications in the areas where weight and size controlling is important, e.g., airplanes and aerospace or in-situ monitoring. An ultra-compact high-precision on-chip interrogator is proposed based on a tailored arrayed waveguide grating (AWG) on a silicon-on-insulator (SOI) platform. The on-chip interrogator enables continuous wavelength interrogation from 1 544 nm to 1 568 nm with the wavelength accuracy of less than 1 pm [the root-mean-square error (RMSE) is 0.73 pm] over the whole wavelength range. The chip loss is less than 5 dB. The 1 × 16 AWG is optimized to achieve a large bandwidth and a low noise level at each channel, and the FBG reflection peaks can be detected by multiple output channels of the AWG. The fabricated AWG is utilized to interrogate FBG sensors through the center of gravity (CoG) algorithm. The validation of an on-chip FBG interrogator that works with sub-picometer wavelength accuracy in a broad wavelength range shows large potential for applications in miniaturized fiber optic sensing systems. [ABSTRACT FROM AUTHOR]

There is a high risk of musculoskeletal discomfort and injury due to the lack of professional guidance and training in caregiving postures. This study aimed to develop a risk assessment and visualization method by analyzing caregiving postures. Participants with (n = 8) and without (n = 10) caregiving experience were recruited to simulate patient transfer from bed to wheelchair. The Rapid Entire Body Assessment (REBA) method lacked sensitivity in distinguishing the experienced and inexperienced groups. We found that the visualization of the center of gravity (COG) trajectory could represent distinct posture differences between the two groups. Based on this finding, we considered a modified REBA method combining the COG trajectory, load-bearing time, and asymmetric load parameters, named the Caregiving-REBA (C-REBA) method. Our results demonstrated that C-REBA could effectively distinguish experienced and inexperienced caregivers, especially in caregiving task Stages 2–4. In conclusion, the present work explored adjusting to the parameters of the REBA method. The proposed C-REBA method could be easily imbedded into the Internet of Things (IoT) device to assess the caregiving posture for providing visual guidance and warning of the risk of discomfort or injury. [ABSTRACT FROM AUTHOR]

A composite indicator (CI) is the mathematical aggregation of sub-dimension (local) indicators used to provide an overall score for the multidimensional concept being measured. CIs are widely used to assess the benefits or risks in human endeavors, such as by creating life satisfaction indices or disaster risk indicators. One important aspect of the development of CIs is setting up value thresholds for taking action, such as in determining the minimum acceptable level of life satisfaction in a community or the maximum acceptable flood risk value beyond which people should be ordered to evacuate from the area in danger. The analytic hierarchy/network process (AHNP) is widely used for the development of CIs. In a review of 111 AHP/ANP CI studies, fewer than 10% discussed any threshold. This means that about 90% of the developed CIs were theoretically sound but lacked the actionable thresholds necessary to be of practical use. Furthermore, for the few studies that set thresholds, the values were typically set arbitrarily or using inadequate statistical approaches. To address this important concern, this study first discusses the most commonly used approaches to setting up thresholds, as well as their inadequacies, and proposes the development of AHP/ANP CI thresholds using a mathematical approach based on the rate of change and center of gravity (RCCG) concepts. Using this approach, a virtual reference alternative, i.e., a threshold profile (TP) made up of the local thresholds of each indicator, is calculated. The key advantage of the proposed method is that it not only provides a non-arbitrary way to set up a CI threshold; more importantly, it is independent of the data and/or alternatives to be evaluated; that is, a threshold calculated with the proposed approach constitutes an absolute reference value, outside the dataset.

This work presents issues related to selected errors accompanying spatial measurements of surface roughness using contact profilometry. The influence of internal heat sources, such as engines or control electronics, on the thermal expansion of the drive responsible for the measurement probe’s movement in the X-axis direction was investigated. In terms of starting measurements on a thermally unstable device, the synchronization error of individual profile paths was 16.1 µm. Based on thermographic studies, the time required for full thermal stabilization of this drive was determined to be 6–12 h from when the device was turned on. It was demonstrated that thermal stabilization of the profilometer significantly reduced positioning errors of the measurement probe on the X-axis. Thermal stabilization time should be determined individually for a specific device variant. This research also determined how changes in the center of gravity caused by the measurement probe’s movement affected the overall rigidity of the profilometer structure and the leveling of the tested surface. Laser interferometry was used for this purpose. The determined vulnerability of the profilometer structure was 0.8 µm for a measurement section of 25 mm. Understanding the described relationships will reduce errors associated with conducting measurements and preparing equipment for tests. Additionally, it will enable the correct evaluation of surface geometry.

Purpose. To determine a reasonable place for installing the equipment unit for the fire-rescue motorcycle, which allows maintaining the stability of the motorcycle when driving at a speed of v ≤ 70 km/h. Methods. To calculate the motorcycle motion model Matlab was used. Findings. The methods have been developed for determining the coordinates of the center of gravity of a multifunctional fire and rescue motorcycle equipped with an equipment unit. The effect of motorcycle speed on its stability when turning around was researched. Application field of research. The results of the work can be used in recommendations for motorcycles exploitation in case of moving to the fire place.

BackgroundMyopia, a condition affecting approximately one-quarter of the world' s population, has been projected to double in prevalence by the year 2050. It can have an impact on postural control during walking and can increase the risk of falls and injuries.Objective(1) To examine the abnormal performance of postural control during walking in male college students who used convex lenses for myopia intervention from a kinematic perspective; (2) to establish theoretical foundation for preventing falls and injuries in the myopic population.MethodsA total of 22 male college students participated in this study. The center of gravity (COG), the percentage of gait cycle (PGC) and the joint angle(JT) were collected as indications of postural control during walking. A quantitative analysis was conducted using a One-Way Repeated Measures ANOVA to examine the variations among the three groups.ResultsDuring myopic interventions, (1) the range of vertical COG changes is significant to be greater compared with normal vision (P < 0.05). (2) there was an significant increase in the PGC in single-legged support, accompanied by a decrease in the PGC in double-legged support, compared with normal vision (P < 0.05). (3) The myopic intervention leads to increased variability in JT of the hip and the knee during the single-leg support and swing, as compared to individuals with normal vision (P < 0.05). Severe myopic interventions result in more changes in JT of ankle.ConclusionMyopia has been found to have a negative impact on postural control during walking, leading to changes in balance, increased instability, and an elevated risk of injury.

Fuel is the largest contributor to the operating cost of airlines. It has always been a concern for researchers to come up with ways to reduce fuel consumption and make the aviation industry more environmentally friendly. The challenge here is to reduce the drag in order to reduce fuel consumption. This research work focuses on the impact of the center of gravity on the total drag of a B747-400 aircraft, with the aim of reducing the amount of fuel consumed and increasing its range. MATLAB code was used to assess the trim conditions at the different center of gravity locations, and the stability and control derivatives were evaluated from the results using Microsoft Excel. The study concludes that as the center of gravity moves aft within the permissible range, the total drag of the aircraft decreases. The optimal center of gravity location was found at 39.5 % of the Mean Aerodynamic Chord (MAC), corresponding to a maximum range of 13,930 km. This research work is important as it provides insight into the relationship between the center of gravity and total drag, and how it affects the fuel consumption and range of an aircraft. By understanding this relationship, engineers can design aircraft with more efficient fuel consumption, thus reducing the environmental impact of the aviation industry.

The center of gravity of a forklift truck, a crucial parameter for vehicle stability, changes with different loads during operation. We propose an estimation algorithm for the center of gravity position suitable for a counterbalanced forklift truck. By installing sensors on the fork, we use an inclinable platform and propose a static joint center of gravity measurement method. For straight-line driving, we establish a longitudinal dynamics model and propose a nonlinear H∞ estimation algorithm. For steering conditions, we establish a roll dynamics model and propose a forgetting factor recursive least square estimation algorithm. A data fusion algorithm for the forklift truck's center of gravity position under various working conditions is proposed. The fusion of these estimation results yields the best estimated center of gravity height. We validate the algorithm's effectiveness using a hardware-in-the-loop simulation platform under different working conditions. The experiments demonstrate the algorithm's fast parameter fitting, wide applicability, and accurate position control within a 5 % error range. [ABSTRACT FROM AUTHOR]

Covert contrast is the statistically reliable distinction between target language phonemes produced in the process of language acquisition that is nevertheless not perceived by a native speaker of that language. This paper examines the acquisition of contrasts in four Najdi Arabic fricatives, /s/, /ʃ/, /θ/, and /ð/, and seeks to identify the most common substitutions in producing these sounds. Words were elicited from 25 preschool children (aged 3–5 years). The target words contained the studied fricative followed by either long /a:/ or short /a/ in the initial position. Praat software was used for acoustic analysis to extract the four acoustic cues: center of gravity, fricative noise duration, F1, and F2. Participants performed a word repetition task and a picture elicitation task. The results showed six cases of covert contrast, seven cases of no contrast, and 87 cases of accurate production (overt contrast). The results also revealed stopping, gliding, and affrication as substitutions in the manner of articulation, while replacement in place of articulation occurred in backing but most commonly in fronting (24 cases). The present study sought to determine implications for children's linguistic performance, and, consequently, for language education and for planning treatment for children with speech disorders. [ABSTRACT FROM AUTHOR]

Logistics is increasingly shown to be essential for agribusiness, given that rural producers are concerned with minimizing costs related to the various processes on the properties. Logistic processes involve economic and environmental costs due to high fuel consumption. This article aims to investigate the best location for the implementation of a shared biodigestion center, in order to minimize the distances to be covered by vehicles that will collect organic waste in different locations, aiming at supplying biodigesters for biogas production. The methodology proposed for this approach consists of applying two methods, the center of gravity method and the facility location method (p-medians). Data from geographic coordinates (Latitude and Longitude) and distances between the considered rural producers were used. This methodology made it possible to identify local options for the installation of a shared biodigestion center among rural swine producers in the region of Toledo-PR, in order to optimize the distances and volumes of waste collected and sent to this center. The results showed that this methodology facilitates the process of collecting and disposing of waste generated on the properties, causing producers to minimize transport costs and the total distance covered, while meeting all demand. [ABSTRACT FROM AUTHOR]

[Objectives] To explore the characteristics of land use change and its main influencing factors in Mojiang County from 2000 to 2020, and try to provide a scientific reference for alleviating the contradiction between man and land in Mojiang County and realizing the sustainable development of regional land resources. [Methods] Based on the land cover data and socio - economic data of Mojiang County from 2000 to 2020, the dynamic degree of land use, land use transfer matrix and center - of - gravity transfer model were calculated, and the temporal and spatial change characteristics and driving factors of various types of land use were calculated by PLUS model. [Results] From 2000 to 2020, the area and proportion of grassland, waters and construction land in Mojiang County showed an upward trend, while the area and proportion of cultivated land and forestland showed a downward trend. Among them, cultivated land was mainly converted into forest land and grassland, and some were converted into waters and construction land; forest land was mainly converted into cultivated land and grassland, and part of it was converted into waters and construction land. From 2000 to 2020, the center - of - gravity of cultivated land, forest land and construction land in Mojiang County moved to the southeast of the county, and the moving rates were 0. 66, 1.97 and 10.58 km/yr, respectively; the center - of - gravity of grassland and waters moved to the southwest of the county, and the moving rates were 1.30 and 20.20 km/yr, respectively. Distance from road, distance from government and distance from waters are the main driving forces affecting land use change in Mojiang County; the forecast shows that in 2040, the area of grassland and forest land in Mojiang County will continue to decrease, the area of cultivated land will turn to rise, and the area of waters and construction land will continue to rise. [Conclusions] Reasonable planning and optimizing the allocation of cultivated land and forest land structure and strict control of the expansion scale of construction land are necessary measures to ensure the coordinated development of regional land rational use and economic construction. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to improve the accuracy and credibility of the evaluation of military equipment support training effect, it abstracts the first-level index weight vector obtained by subjective and objective weighting method as multiple particles in multi-dimensional space. The relative weight of each weight vector in index aggregation is determined by the distance between particle and center of gravity. It takes the center of gravity of multiple particles obtained iteratively as the ideal weight vector of the first-order index. This method integrates the advantages of subjective and objective weighting methods, and optimizes the index aggregation method of combined weighting method, so that the evaluation of military equipment support training effect can take into account the importance of indicators and the difference of index values.

The traditional method of allocating passenger seats based on compartments does not effectively manage an aircraft’s center of gravity (CG), resulting in a notable divergence from the desired target CG (TCG). In this work, the Boeing B737-800 aircraft was employed as a case study, and row-based and compartment-based integer programming models for passenger allocation were examined and constructed with the aim of addressing the current situation. The accuracy of CG control was evaluated by comparing the row-based and compartment-based allocation techniques, taking into account different bodyweights and numbers of passengers. The key contribution of this research is to broaden the range of the mobilizable set for the aviation weight and balance (AWB) model, resulting in a significant reduction in the range of deviations in the center of gravity outcomes by a factor of around 6 to 16. The effectiveness of the row-based allocation approach and the impact of passenger weight randomness on the deviation of an airplane’s CG were also investigated in this study. The Monte Carlo method was utilized to quantify the uncertainty associated with passenger weight, resulting in the generation of the posterior distribution of the aircraft’s center of gravity (CG) deviation. The outcome of the row-based model test is the determination of the range of passenger numbers that can be effectively allocated under different TCG conditions.

Purpose/Background: Various methods are available for assessment of static and dynamic postural stability. The primary purpose of this study was to investigate the relationship between dynamic postural stability as measured by the Star Excursion Balance Test (SEBT) and static postural sway assessment as measured by the TechnoBody™ Pro-Kin in female soccer players. A secondary purpose was to determine side-to-side symmetry in this cohort. Methods: A total of 18 female soccer players completed testing on the SEBT and Technobody™ Pro-Kin balance device. Outcome measures were anterior, posterior medial, and posterior lateral reaches from the SEBT and center of pressure in the x- and y-axes as well as SD of movement in the forward/backward and medial/lateral directions from the force plate on left and right legs. Bivariate correlations were determined between the 8 measures. In addition, paired Wilcoxon signed-rank tests were performed to determine similarity between limb scores. Results: All measures on both the SEBT and postural sway assessment were significantly correlated when comparing dominant with nondominant lower-extremities with the exception of SD of movement in both x- and y-axes. When correlating results of the SEBT with postural sway assessment, a significant correlation was found between the SEBT right lower-extremity posterior lateral reach (r =.567, P <.05) and summed SEBT (r =.486, P <.05) and the center of pressure in the y-axis. A significant correlation was also found on the left lower-extremity, with SD of forward/backward movement and SEBT posterior medial reach (r = −.511, P <.05). Conclusions: Dynamic postural tests and static postural tests provide different information to the overall assessment of balance in female soccer players. Relationship between variables differed based on the subject's lower-extremity dominance. [ABSTRACT FROM AUTHOR]

In this paper, we represent the integral of vectors of a hyperbolic simplex by volumes of facets and unit vectors pseudo-perpendicular to them. By using it, we can define a new hyperbolic centroid of a hyperbolic simplex. [ABSTRACT FROM AUTHOR]

Copyright of Ingenius, Revista Ciencia y Tecnología is the property of Universidad Politecnica Salesiana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Hyperopia is a common blurred vision phenomenon that affects postural control in gait; however, current research has focused on the alteration and correction of hyperopia's physiological characteristics, ignoring the effect of hyperopia on gait kinematic characteristics. The effect of hyperopia on the basic form of movement walking is a worthy concern. Objective: To investigate the gait kinematic characteristics of male college students with varying degrees of visual acuity (normal vision, hyperopia 150°, and hyperopia 450°), as well as to provide a theoretical foundation for the effect of visual acuity on gait and fall risk reduction. Methods: Twenty-two male college students with normal visual acuity were chosen. Their vision was tested using a standard visual acuity logarithm table at normal and with 150° and 450° concave lenses. Gait kinematic data were collected under normal vision and hyperopic conditions using the PN3 Pro advanced inertial motion capture system and Axis Studio application program. Results and conclusion: 1. The change of center of gravity in Pre-double support was smaller than normal vision; Late-single support and Late-swing was larger than normal vision; 2. The percentage of the double-leg support decreased; the percentage of the single-leg support and the Late-swing increased; 3. For the joints' range of motion, Trunk flexion and extension range of motion in Pre-single support, Late-double support and Pre-swing smaller than normal visual acuity, and Late-swing larger than normal; hip internal abduction and adduction and internal and external rotation are larger than normal vision in Late-single support; knee and ankle in abduction and adduction direction are larger than normal vision in the swing stage; hip flexion and extension, internal external rotation are larger than normal vision in the swing stage. Hyperopic interventions have an impact on the kinematic characteristics of gait in male college students, mainly in terms of altered balance, increased instability, increased difficulty in maintaining trunk stability, and increased risk of injury. [ABSTRACT FROM AUTHOR]

Sustainable development is a hot issue in global research today. As a large developing country, China has increasingly prominent conflicts between water use, the population, and the economy, so it is necessary to solve the sustainable development issues represented by water use, the population, and the economy. To explore the evolutionary process for water use, the population, and the economy in China, we calculated the evolutionary path of the center of gravity for water use, the population, and the economy in China from 1965 to 2019 by using the center of gravity model, and we calculated the decomposed contributions of the evolutionary path of the center of gravity for water use, the population, and the economy in China from 1965 to 2019, which the six major areas in China contributed to, by using the center of gravity decomposed contributions model. The results show the following: (1) As a whole, the center of gravity cumulative yearly moving distance for water use was 835.77 km, and the center of gravity moving direction as well as angle were north by east, 18.95°. The center of gravity cumulative yearly moving distance for the population was 113.40 km, and the center of gravity moving direction as well as angle were south by west, 31.50°. The center of gravity cumulative yearly moving distance for the economy was 449.83 km, and the center of gravity moving direction as well as angle were south by east, 8.63°. (2) From the decomposed value contribution rate of the evolutionary path of the center of gravity in the latitude direction for water use, the population, and the economy in China from 1965 to 2019, which the six major areas in China contributed to, Northeast China contributed the most (42.26%, 34.09%, and 39.37%, respectively). The increasing proportion of total water use consumption in Northeast China most positively affected the evolutionary path of the center of gravity for water use in China, moving northwards from 1965 to 2019, and the decreasing proportion of the total population as well as gross regional product in Northeast China most negatively affected the evolutionary path of the center of gravity for the population and economy in China, moving southwards from 1965 to 2019. [ABSTRACT FROM AUTHOR]