Change In Center Of Gravity Research Articles

Analysis of Spatial and Temporal Trends of Vegetation Cover Evolution and Its Driving Forces from 2000 to 2020—A Case Study of the WuShen Counties in the Maowusu Sandland

The WuShen counties in the hinterland of the Maowusu Sandland are located in the “ecological stress zone” of the forest–steppe desert, with low vegetation cover, a strong ecosystem sensitivity, and poor stability under the influence of human activities. Therefore, it is important to study and analyze the changes in vegetation growth in this region for the purpose of objectively evaluating the effectiveness of desertification control in China’s agricultural and pastoral intertwined zones, and formulating corresponding measures in a timely manner. In this paper, the spatial and temporal variations in the vegetation NDVI in the WuShen counties of the Maowusu Sandland and their response relationships with driving factors were investigated by using a trend test, center of gravity transfer model, partial correlation calculation, and residual analysis, and by using the MOD13A3 vegetation NDVI time series data from 2000 to 2020, as well as the precipitation, temperature, and potential evapotranspiration data from the same period. The results showed the following: ① The regional vegetation NDVI did not fluctuate significantly with latitude and longitude, and the NDVI varied between 0.227 and 0.375 over the 21-year period, with a mean increase of 0.13 for the region as a whole and an increase of 0.61 for the region of greatest change. Of the area, 86.83% experienced a highly significant increase, and the trend in increase around rivers and towns was higher than that in the northwestern inland flow area, with the overall performance of “low in the west and high in the east”. ② Only 2.07% of the vegetation NDVI center of gravity did not shift, and the response with climate factors was mainly characterized by having consistent or opposite center of gravity changes with precipitation and potential evapotranspiration. ③ Human activities have been the dominant factor in the vegetation NDVI change, with 75.89 percent of the area positively impacted by human activities, and human activities in the southwest inhibiting the improvement of vegetation in the area. The impact of human activities on the unchanged land type area is increasing, most obviously in the farmland area, and the impact of human activities on the changed land type area is gradually decreasing in the area where the farmland becomes impervious. The vegetation in the area above 1300 m above sea level is degraded by the environment and human activities. The research results can provide scientific support for the implementation of ecological fine management and the formulation of corresponding ecological restoration and desertification control measures in the Maowusu Sandland. At the same time, it is expected to serve as a baseline for other studies on the evolution of vegetation in agro-pastoral zones.

Analysis of Land Use Gravity Center Change and Carbon Emission Impact in Chengdu Plain of China from 2006 to 2022

As the economic center and major grain-producing area in Southwest China, the calculation of the carbon budget and the protection of cultivated land in the Chengdu Plain are of vital significance for China to achieve a carbon peak strategy and ensure food security. For the purpose of clarifying the trend of land use focus and carbon emissions in the Chengdu Plain, the carbon peak level of land use in 33 counties in the Chengdu Plain was explored. Based on the gravity center model and IPCC carbon emission coefficient method, the changing trend of land use gravity center and carbon emission in Chengdu Plain from 2006 to 2022 was clarified. PLS regression model and LMDI model were used to explore the main influencing factors of the carbon emission of cropland and the carbon emission of building land. PLUS model was used to simulate future land use patterns and carbon emissions. (1) The center of gravity of cropland, building land, water, and other and unused land shifted to the northeast by 4.23 km, 5.46 km, 8.44 km, and 31.58 km, respectively, and that of forest and grass shifted to the southeast by 11.12 km and 3.41 km, respectively. For major food crops, the centers of gravity of rice and maize moved northeastward by 15.47 km and 7.52 km, respectively, while wheat moved southwestward by 17.77 km. (2) From 2006 to 2022, carbon emissions from land use in the 33 counties of the Chengdu Plain are all on the rise, with a total increase of 13.552 million tons, and carbon sinks in the 31 counties continue to decline, with a total decrease of 0.691 million tons. (3) Under the natural scenario, carbon sink scenario, and carbon reduction scenario, the carbon emissions from land use decrease by 0.5391 million tons, 3.4728 million tons, and 4.5265 million tons from 2022, respectively. Among the 33 counties in the Chengdu Plain, 11 counties did not achieve carbon peak under the natural scenario, 5 counties did not achieve carbon peak under the carbon sink scenario, and all the counties achieved carbon peak under the carbon sink scenario. During the study period, there was a serious loss of cropland in the Chengdu Plain, mainly to building land in the central part of the Chengdu Plain and to forests within the Longmen Mountain, Longquan Mountain, and Leshan City, and there is a need to strengthen cropland protection in this region in the future. Under the natural scenario, carbon sink scenario, and carbon reduction scenario, land use in the Chengdu Plain region can achieve carbon peak, and the carbon reduction model will be more helpful for the counties to achieve carbon peak.

Three-point support analysis and optimization design under the change of gravity center of diamond lathe

The position of three-point support has an important impact on the stiffness and accuracy of the diamond lathe. To determine the position of the support, this paper commences by conducting static and dynamic analysis on the large-size platform machine tool whose base is 2340×1540 mm under the two support schemes. It determines the basic layout scheme of the support points of the machine tool under the change of gravity center. Subsequently, by combining the least squares fitting and particle swarm optimization algorithm with the optimization goal of minimum deformation of the machine tool base working surface, the position of the support points is optimized under the influence of the Change of Gravity center. The results indicate that the optimal solution of the design variable within the design interval can be obtained through limited sampling points and optimization iterations. The average and maximum deformation of the base working surface are 0.867 μm and 1.45 μm. They decreased by 11.17% and 26.02% compared with before optimization.

Fluid-structure interaction dynamic analysis of large civil aircraft tank sloshing

To meet the requirements of passengers, the tank volume of large civil aircraft is gradually increasing, which brings certain risks. Under different 0 pertaining conditions during the flight, the liquid in the tank will cause structural failure and affect the aircraft’s safety. Therefore, based on the assumption of an ideal fluid, the smooth particle method (SPH) combined with the finite element method (FEM) is used to establish the coupling dynamic equation between the tank and the liquid. The effects of sloshing impact on the water tank under different filling rates were studied, and the influences of the water wave shape, the center of gravity shift, stress distribution, and deformation of the tank were obtained. The results show that the mass accumulation of water particles occurs in the acceleration stage, the relative center of gravity changes greatly in less water, and the accumulated liquid greatly influences the tank under the action of inertia. The more liquid in the tank is, the more the impact effect on the tank increases. The analysis results provide some reference for the analysis and design of tank anti-sway plates and flight attitude adjustment.

Spatial–Temporal Evolution Analysis of the Development of Jingdang and Famen Townships in the Vicinity of the Capital City Site of the Western Zhou Dynasty in China

This study aimed to explore the evolution of Jingdang and Famen towns near the Zhouyuan site, the capital city site of the Western Zhou Dynasty in China, to elucidate the relationship between township development and the essential ancient relics conservation areas. Based on the remote sensing satellite images from 1982 to 2022, combining with historical demographic data, this study used four methods, including land use classification, land use transfer matrix, landscape pattern center of gravity changes, and population count statistics, to study the spatial–temporal evolution of land, population, and ecology in the region over the past 40 years. The results showed that under the strict relic conservation regimen, these two towns are in a declining stage. To improve their decaying status, some potential strategies valuable for township development are proposed to balance the relationship between relic conservation and township development for their mutual benefit and coexistence.

Investigation of the Relationship of Functional Improvement and Body Mass Index in Breast Reduction Patients.

Due to macromastia, center of gravity changes and neck, shoulder, back pain become prominent. Macromastia and obesity separately cause pain and an increase in curves of vertebra. The aim of this study is to compare the functional benefits of reduction mammoplasty between obese and non-obese patients. Data of this retrospective study were collected from archives and include preoperative/postoperative thoracic Cobb angles, preoperative/postoperative VAS scores, BMI and resected breast tissue weight of patients who underwent reduction mammaplasty operations between August 2017 and April 2019 in Plastic, Reconstructive and Aesthetic Surgery Department. This study shows that reduction mammoplasty enables significant decrease both in thoracic kyphosis angles and in neck, shoulder and back VAS scores. However, no significant difference was found in preoperative/postoperative values and mean amount of changes of thoracic kyphosis angles between obese and non-obese patients. Decreases in neck, shoulder and back VAS scores were not found statistically significant between two groups. The breast resection amount was not related to correction of kyphosis, but it enabled only a significant decrease in neck VAS scores. Functional improvement was not related to body mass index in reduction mammoplasty patients. Functional benefits were observed similarly in both obese and non-obese patients. A precise threshold value for body weight, body mass index and amount of breast tissue could not be defined as an indication for functional reduction mammoplasty. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Kinematic characteristics of gait with different myopia: a cross-sectional study.

Myopia, 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. (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. A 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. During 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. Myopia 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.

Study on the Spatial and Temporal Evolution of Regional Green Space Morphology Outside Built-Up Areas based on the Google Earth Engine and Biophysical Component Modeling

The spatial pattern of regional green space is an important dimension to describe and quantitatively express the characteristics of regional green spaces outside the built-up area of a city. With the expansion of urban and rural construction land, regional green space has been continuously encroached upon. This leads to a decline in regional ecological well-being and the loss of biodiversity. Based on the remote sensing data of Shanghai city from 2000 to 2020, we quantitatively studied the spatial morphological change characteristics of regional green space outside the built-up area of Shanghai city. Firstly, with the help of the GEE platform, the optimal decoding accuracy classification method was selected through machine learning (random forest, support vector machine, classification regression tree); then, based on the biophysical component (BCI) and CA binarization, the built-up area ranges for up to five time nodes were obtained; finally, through GIS spatial data analysis and processing technology, the regional green space dynamic data of Shanghai for five time nodes were extracted. Based on the above data, an analysis index system was constructed to quantitatively analyze the spatial morphology characteristics of the regional green space outside the built-up area of Shanghai. The results show that (1) the area of regional green space outside the built-up area of Shanghai had a fluctuating growth pattern of “decreasing and then increasing”. The arable land and water areas in Shanghai decreased, and the woodland area increased steadily, while the wetland and grassland areas showed a trend of first decreasing and then increasing. (2) The regional green patch fragmentation shows a fluctuating development trend of increasing, decreasing, and increasing. (3) The change in the spatial center of gravity of the regional green space in Shanghai had a high degree of consistency with the overall green space change. The center of gravity of the grasslands in the regional green space moved substantially to the northwest, while the center of gravity of the other types remained basically unchanged. This study reveals the spatial morphology characteristics of regional green spaces and provides a research method to study the dynamic changes in regional ecological resources. The results of this study can provide a scientific basis for the identification, protection, and development of regional ecological resources.

MRI-based inter- and intrafraction motion analysis of the pancreatic tail and spleen as preparation for adaptive MRI-guided radiotherapy in neuroblastoma

BackgroundIn pediatric radiotherapy treatment planning of abdominal tumors, dose constraints to the pancreatic tail/spleen are applied to reduce late toxicity. In this study, an analysis of inter- and intrafraction motion of the pancreatic tail/spleen is performed to estimate the potential benefits of online MRI-guided radiotherapy (MRgRT).Materials and methodsTen randomly selected neuroblastoma patients (median age: 3.4 years), irradiated with intensity-modulated arc therapy at our department (prescription dose: 21.6/1.8 Gy), were retrospectively evaluated for inter- and intrafraction motion of the pancreatic tail/spleen. Three follow-up MRIs (T2- and T1-weighted ± gadolinium) were rigidly registered to a planning CT (pCT), on the vertebrae around the target volume. The pancreatic tail/spleen were delineated on all MRIs and pCT. Interfraction motion was defined as a center of gravity change between pCT and T2-weighted images in left-right (LR), anterior-posterior (AP) and cranial-caudal (CC) direction. For intrafraction motion analysis, organ position on T1-weighted ± gadolinium was compared to T2-weighted. The clinical radiation plan was used to estimate the dose received by the pancreatic tail/spleen for each position.ResultsThe median (IQR) interfraction motion was minimal in LR/AP, and largest in CC direction; pancreatic tail 2.5 mm (8.9), and spleen 0.9 mm (3.9). Intrafraction motion was smaller, but showed a similar motion pattern (pancreatic tail, CC: 0.4 mm (1.6); spleen, CC: 0.9 mm (2.8)). The differences of Dmean associated with inter- and intrafraction motions ranged from − 3.5 to 5.8 Gy for the pancreatic tail and − 1.2 to 3.0 Gy for the spleen. In 6 out of 10 patients, movements of the pancreatic tail and spleen were highlighted as potentially clinically significant because of ≥ 1 Gy dose constraint violation.ConclusionInter- and intrafraction organ motion results into unexpected constrain violations in 60% of a randomly selected neuroblastoma cohort, supporting further prospective exploration of MRgRT.

Spatio-temporal evolution and gravity center change of carbon emissions in the Guangdong-Hong Kong-Macao greater bay area and the influencing factors

The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is one of the most densely built and economically vibrant regions in China, it is of vital importance to study the spatio-temporal heterogeneity and influence mechanisms of its carbon emissions against the backdrop of peaking carbon dioxide emissions and achieving carbon neutrality. However, systematic research on this area is still lacking. Therefore, this study uses spatial autocorrelation, kernel density estimation, and standard deviation ellipses to construct an exploratory spatial data analysis (ESDA) framework to analyze the spatio-temporal evolutionary characteristics of carbon emissions from GBA and combine it with the geographically and temporally weighted regression (GTWR) model to identify the various influencing factors of carbon emissions in GBA and reveal its implications. The results showed that: (1) Between 2009 and 2019, the total carbon emissions in GBA remained stable and gradually decreased. The gap between the carbon emission intensity of the cities narrowed. (2) The GBA urban agglomeration exhibited spatial autocorrelation, but characteristics of the global spatial pattern had not yet formed a steady state. The kernel density of carbon emissions in GBA showed an obvious “monopolar” phenomenon. (3) The gravity centre of carbon emissions in GBA was located to the southeast of the geometric centre of the whole region, shifting toward the northwest. (4) Population size, level of economic development and energy intensity have a strong positive contribution to carbon emissions, compared to the level of opening up and industrialization level, which has a weaker impact. There is significant spatial heterogeneity in the distribution of regression coefficients for each factor, and GBA should take full account of the characteristics of different types of cities in terms of carbon emissions and implement targeted emission reduction strategies. Our research provides a comprehensive analytical framework for regional carbon emissions, offering theoretical support for low-carbon development in the GBA.

Effect of slope change on kinematics of amateur golfers' full swing.

Golf courses are designed with uneven terrain. These factors are especially important when facing (slope), players need to straighten the posture of each part of the body in order to complete the swing on an inclined surface such as flat ground. Amateur players may be more likely to change the movement patterns of their shots due to uneven terrain. Therefore, it may be necessary to clarify the shot characteristics of amateur players and provide reference materials for technical improvement. The purpose of this study was to examine the effect of slope on amateur golfers' swing kinematics by analyzing the variation of time variables, body center of gravity (COG), and shot parameters of amateur golfers' swing at different ground slopes. Six male amateur golfers participated in the experiment. The 7-iron was used for 5 swings each at three slopes: flat ground (FG, 0∘), ball below foot (BBF, +10∘), and foot below ball (FBB, -10∘). The OptiTrack-Motion capture system was used to collect kinematic data, and the three-dimensional motion data will be transmitted to Visual3D software for subsequent data analysis such as golf swing division and body COG changes. Shot parameters (carry, swing speed, ball speed, and smash factor) were recorded for each swing using the Caddie SC300 radar monitoring device. The results showed that there was no difference in the overall swing time and the time required for each interval at different slopes (p> 0.05) there is no significant difference in the change of the COG of the body in the forward and backward directions (p> 0.05). The three slopes of swing speed, ball speed, carry and smash factor were not significantly different (p> 0.05). The rhythm of the amateur golfer's swing was not affected by the slope, but the slope restricts the movement of the body's COG, which may affect the weight movement, and ultimately cause the performance parameters to not reach the level of the FG.

The Biomechanical Analysis of Jumping Difficulty Movement in National Traditional Sports

In order to explore the relevant factors and the completion of difficult movements, this paper is an important theoretical basis for improving and constructing the evaluation of athletes’ movement quality. It presents a kinematic analysis of the difficult movements of competitive Tai Chi, taking the difficult movements of the swirl group of competitive aerobics as the research object. The data is collected by different methods. When completing difficult movements, due to different personal exercise habits, this paper takes the right leg as the swinging leg and the left leg as the take-off leg when completing the difficult movements. The test object in this paper adopts the traditional three-step up-step method. The starting time of the take-off stage is consistent with the illustration. By consulting experts for the stage division of the difficult movement, the two movement stages are equally divided into three stages according to the needs of the research: take-off, soaring, and landing. The results show that, from the moment the left foot hits the ground to the moment of maximum cushioning, the angles of the right knee are 176.48° and 165.06°, respectively, and the flexion of the right knee is not large; especially when the left foot touches the ground, the right leg is close to a straight line, indicating that the athlete’s body is in a straight line. The posture is relatively good, the left foot is used as the grounding leg, the angle of the knee joint is reduced from 160.82° to 124.41°, and the left knee buffer angle is 36.40°. As the right leg swings to the ground, the left knee and left hip are slightly stretched, and the right knee and right hip are slightly flexed. This change is also reflected in the fact that the center of gravity changes from the direction of the horizontal speed at this stage. Move the left side of the body slightly to the right. Difficulty movements are different in the landing stage, and their joint parameters are also different. When the landing leg touches the ground, there is no significant difference in the maximum cushioning time, the degree of torsion of the shoulder and the hip is different, the relative rotation position of the shoulder and the hip is opposite, and the posture of the shoulders at the time of landing is different. In teaching, the landing leg and the end direction of the rotation are not the same; it is necessary to strengthen the strength training of the legs, to experience the force feeling of the different degrees of rotation of the shoulder joint and the hip joint, as well as the spatial perception ability, and take the initiative to actively land. The magnitude of the rear cushion and the coordination of the trunk and the limbs are used to avoid unnecessary damage during the landing phase.

Gravity center change of carbon emissions in Chinese residential building sector: Differences between urban and rural area

In China, dynamic spatial–temporal evolution and urban–rural gap in carbon emissions of residential building sector are crucial for understanding the current state, which is faced with great challenges related to emission mitigation. To overcome the challenge, this study employed the gravity center model to explore spatial–temporal evolution of carbon emissions and analyzed the driving factories leading the differences between urban residential buildings and rural residential buildings via decomposition analysis. Meanwhile, Tapio decoupling index is used to predict the future movement of the gravity center. Our results indicated that: (i) the carbon emissions gravity center of both residential building types tends to move south; (ii) the northeast and northwest regions play the largest role in driving the gravity center movement of urban residential buildings and rural residential buildings, respectively; (iii) per capita disposable income is the primary factors affecting the gravity center movement. (iv) the gravity center of both residential building types might tend to move westward in the future. Overall, this study attempts to remedy the current lack of research pertaining to spatial–temporal evolution laws governing carbon emissions in the Chinese residential building sector and provides a reference point for the implementation of targeted urban and rural emission reduction policies.

TO SPECIFICATION OF THE FORCE OF A VIBRATORY ROLLER ON THE SOIL

As a result of the analysis of tillage rollers, it was revealed that the main design feature is to ensure the required specific pressure on the soil, consequently, it is necessary to increase the roller mass per 1 m of the working width, whereas it leads to metal consumption increase of the tool. Based on the obtained data, we developed a fundamentally new design of the vibratory roller, its application will ensure the fulfillment of agrotechnical requirements for soil density with a minimum metal consumption of 70 kg/m. High-quality tillage with a vibratory roller is ensured by a passive drive of unbalancers installed on the axis of a hollow cylinder. To determine the center of mass of the unbalancers, the KOMPAS 3D v 20 program was used, which allows to obtain the desired result with an accuracy of 0.000001 mm. It was revealed in the course of the theoretical study that the unbalancers create vibrations with an amplitude of 0.00008 ... 0.0011 m at a rotation frequency of 800 min-1 due to their displacement in relation to the axis of the vibratory roller. Also, it was revealed that when the unbalancers are displaced in relation to the roller axis, the position of their center of gravity changes by approximately the same value. Concurrently, the specific pressure of the vibratory roller on the soil changes from 732.81 N/m to 1275.28 N/m, increasing by 74% in case of displacement of the unbalancers in relation to the axis of the vibratory roller up to the maximum value of a = 20 mm. Field studies of the proposed roller showed that the quality of soil compaction by the proposed vibratory roller with improved parameters and modes of operation is better than that of the most common rollers, namely, ZKVG-1.4 and ZKKSH-6.

Multi-body modelling and adaptive control of a re-configurable uninhabited airship

This paper presents pitch control of an uninhabited airship using changes in center of gravity. Changes in center of gravity are achieved by controlling the position of a movable gondola along a rigid keel fixed to the bow of the helium envelope. The longitudinal multi-body dynamic equations of motion were developed using the measured and estimated physical properties and an adaptive PID controller was designed to control the pitch angle. Flight tests on a 4 m long uninhabited airship prototype were conducted to demonstrate the effectiveness of the method.

Design, development and experimental validation of a lightweight dual-arm aerial manipulator with a COG balancing mechanism

In this work, we present the design, fabrication, and experimental validation of a lightweight, low inertia dual-arm manipulator with a center of gravity (COG) balancing mechanism, specifically designed for aerial manipulation missions. The developed system, consisting of the dual-arm base and two arms with 6 degrees of freedom (DOFs) each, weighs 2.5 kg in total with a maximum payload of 1.0 kg per arm. The dual-arm system is designed such that it can be attached to different multirotors without making major design modifications. In addition, the design of the arms is conceived to decrease the inertia of the arms by utilizing a timing belt-based transmission mechanism. Moreover, the proposed dual-arm design employs prismatic joints to introduce the following distinctive features: 1) ability of each arm to dynamically adjust its COG for better flight performance; 2) fully independent control of each arm for performing different tasks simultaneously; 3) extended workspace and reach of the arms for enhancing operational capability and improving safety during aerial manipulation missions. Since the proposed design has low inertia and a compensation mechanism to deal with the disturbances caused by the COG change, the developed dual-arm system can be mounted on multirotors equipped with standard autopilots, opening the door for the widespread use of dual-arm manipulators with the commercially available UAV platforms. To ensure the robustness of the mechanical structure, an analysis using finite element methods (FEM) is conducted. Extensive experimental flight tests are performed to evaluate the proposed dual-arm design with a hexarotor equipped with a common off-the-shelf autopilot. The experimental results show that the influence of the arms motion over the hexarotor stability is minor in contactless flight due to the low weight and inertia of the proposed dual-arm design. Furthermore, better hovering performance is achieved by exploiting the ability of the proposed design to compensate the dual-arm COG displacement.

Brownian Noise and Temperature Sensitivity of Long-Period Lunar Seismometers

ABSTRACT As long-period ground motion holds the key to understanding the interior of the Earth’s Moon, reducing long-period noise sources will be an essential area of focus in the design of future lunar seismometers. For the proposed Lunar Geophysical Network (LGN), the International Lunar Network (ILN) Science Definition Team specifies that an LGN enabling seismometer will need to be more sensitive than any previous seismometer at frequencies below 1 Hz. In an effort toward lowering the seismometer noise floor for lunar geophysical missions, we evaluate the 1/f Brownian noise and the temperature sensitivity of a seismometer. Temperature sensitivity of a seismometer is related to an important component of the seismometer output noise that is proportional to the temperature noise in the environment. The implications of the ILN requirement are presented in the context of the state-of-the-art InSight Seismic Experiment for Interior Structure (SEIS) Very Broad Band (VBB) planetary seismometer. Brownian noise due to internal friction was estimated for future lunar operation after accounting for the rebalance of the product of mass and distance to the center of gravity of the pendulum for the SEIS-VBB sensor. We find that Brownian noise could be a limiting factor in meeting the ILN requirement for lunar seismometers. Further, we have developed a formalism to understand the temperature sensitivity of a seismometer, relating it quantitatively to the local gravity, the thermoelastic coefficient of the spring, change in center of gravity, and the coefficient of thermal expansion of the mechanical structures. We found that in general the temperature sensitivity of a seismometer is proportional to the local gravity, and so the temperature sensitivity can be reduced when operating on a planetary body with lower gravity. Our Brownian noise and temperature sensitivity models will be useful in the design of the next generation of planetary seismometers.

Comprehensive Analysis of Minibuses Gravity Center: A Post-Production Review for Car Body Industry

The center of gravity (CoG) on the minibus is one of the fundamental parameters that affect the operation of the vehicle to maintain traffic safety. CoG greatly affects vehicle maneuverability due to load transfer between the front and rear wheels, such as when turning, braking, and accelerating. Therefore, this research was conducted to evaluate the operational safety of minibusses produced by the domestic car body industry. The case study was conducted on a minibus with a capacity of 30 passengers to be used in a mining area. Investigations on CoG were carried out based on the minibus specification data, especially the dimensions and forces acting on the wheels. Minibusses as test objects were categorized in two conditions, namely without passengers and with 30 passengers. The test results are expressed in a coordinate system (x, y, z) which represents the longitudinal, lateral, and vertical distances to the center of the front wheel axle. CoG coordinate values ​​without passengers are (2194.92; 7.11; 1327.97) mm and CoG coordinates with full passengers (30 people) are (2388.52; 13.04; 1251.72) mm. The test results show that the change in CoG at full load is not significant which indicates the minibus is safe when maneuvering under normal conditions.

Analysis and experimental research on stability characteristics of squatting posture of wearable lower limb exoskeleton robot

Aiming at the problems of complex movement posture, many degrees of freedom and flexible movement of the human body’s lower limbs, a dynamic mathematical model of the squat posture was established, and analyzed the dynamic parameters of the hip joint, knee joint and ankle joint during the squatting posture of the wearable lower extremity exoskeleton robot. Based on the MATLAB simulation software, the motion characteristics of the squat posture are simulated and analyzed, and the results show that: in the process of squatting, the theoretical calculation results are quite different from the simulation results, indicating that the process of squatting is unstable. Therefore, based on the Zero Moment Point (ZMP) theory, a stable polygon of the squat posture is established, the instability rate is defined. From a qualitative and quantitative point of view, the effects of the squat posture and the change of the center of gravity (COG) on the motion stability are analyzed. An experimental platform was built and the experiment was performed to verify the COG and ZMP changes in the squatting posture, which verified the correctness of the theoretical calculation conclusions and the influence of COG changes on ZMP.

Monitoring desertification in Mongolia based on Landsat images and Google Earth Engine from 1990 to 2020

Desertification is one of the most serious ecological and environmental problems in arid regions. Low-cost, wide-ranging, and high-precision methods are essential for the formulation of appropriate strategies for quantitatively monitoring desertification. In this study, based on Google Earth Engine and Landsat images, six machine learning methods were used to monitor desertification dynamics in 1990–2020 in Mongolia. The spatiotemporal distributions and changes in desertification at different stages were analyzed using gravity center change and intensity analysis models. Subsequently, we quantitatively investigated the factors driving desertification in Mongolia. The results indicate that the maximum entropy method can obtain the most accurate assessment of the degree of desertification in comparison with the other five methods, with an accuracy of 96%. In 1990–2005, the area of desertified land increased significantly, afterward, a decreasing trend was observed. Lightly and moderately desertified lands had the highest change intensities and were most sensitive to environmental factors. Although the desertification dynamics are under the influence of both natural and anthropogenic factors, precipitation plays a dominant role in Mongolia. This study provides a comprehensive analysis of the desertification status and trends in Mongolia, and presents desertification maps that can be used to formulate preventive measures and guide desertification prevention and control.