System Mass Balance Research Articles

Automatic mass balancing of spacecraft attitude simulators by optimal feedback control

There is an increasing interest in development of spacecraft attitude simulators. A necessary and challenging task in preparation for any attitude control experiment is to remove the gravitational disturbances on the simulator by a mass balancing system which relocates the center of mass to coincide with the center of rotation. This research is aimed at filling a substantial gap in the literature by presenting a methodical framework for analysis and design of closed-loop automatic mass balancing systems. In this regard, a state-space representation for imbalanced dynamics of attitude simulators is derived to enable the application of modern control techniques to the problem which will be shown to be very effective in achieving an accurate balancing. The model is further enhanced by state augmentation and incremental control input to address the practical requirements for an efficient balancing strategy. Next, an optimal feedback control is designed on the enhanced dynamics model to minimize the rotational kinetic energy and leveling accuracy as key performance measures of the problem. The simulation results and comparative evaluations with a previously validated method verified that the proposed modeling and control approach is effective in achieving an accurate mass balancing while providing a convenient and methodical analysis and design procedure.

Geochemical and mineralogical processes leading to variation of soil characteristics on calcareous toposequence in semiarid ecosystem condition

Soils are under the influence of their formation processes at varying rates. Determining the variability and characteristics of soils due to the formation processes’ effects is vital for sustainable soil management. This study aimed to investigate soils formed on limestone and on different physiographic units (summit, shoulder, backslope and footslope) under semiarid climatic condition. That is why, the present study assessed clay mineralogy, weathering indices, mass loss/gain states, and physic-chemical properties of different profiles. It is concluded that smectite clay mineral is dominant in the profile IV located on footslope position with differences in clay mineralogy due to physiographical change. The summit physiographic unit includes the highest aggregate stability (63.74%). The soil’s field capacity and wilting point contents showed statistically significant variation with the increase in smectite clay minerals in the PIV profile on the footslope unit (p < 0.01). In addition, a positive (0.506; p < 0.05) directional relationship was found between the variability in physiographic units (from summit to footslope) and the available water content (AWC). In addition, bulk density and porosity characteristics varied depending on the particle size distribution and land use type. The soils formed on shoulder and backslope units classified as Entisol soil order are described as “not decomposed” according to the Chemical Alteration Index (CIA), Chemical Weathering Index (CIW), and Plagioclase Alteration Index (PIA) values. On the other hand, in the Inceptisol and Vertisol soils, it was determined leaching process for basic cations in the PI and PIV profiles located on the summit and footslope. As for mass balance system, the highest losses from the soil formed on the backslope whereas, the PI and PIV formed on the footslope position gains. As a result of this study, it has been revealed that soil formation process in the summit and footslope is more effective than in other physiographic units. Therefore, physico-chemical properties are mainly affected by these processes.

Quantifying microplastic stocks and flows in the urban agglomeration based on the mass balance model and source-pathway-receptor framework: Revealing the role of pollution sources, weather patterns, and environmental management practices

Microplastics are widely present in global ecosystems, threatening both marine and freshwater species. Given this problem, it is vital to research where land-based microplastics originate and how they are transmitted to receiving waters in urban agglomerations. Research results should inform systemic mitigation efforts to prevent future contamination. This study established the multi-directional transmission network of a microplastic mass balance system using a source-pathway-receptor framework, and involving annual source stocks and pathway flows with considerable variations under dry and wet weather patterns. Details of a baseline scenario quantifying the occurrence and spread of microplastics in an urban agglomeration were also determined in the context of current environmental management practices. We demonstrated that the total stock of the six major pollution sources amounted to 5317.7 ± 2175.3 and 3320.1 ± 953.6 tons/a in dry and wet weather, respectively; and 2347.8 ± 766.9 and 1991.8 ± 701.8 tons/a flows directly entered the sewer system and receiving water in Shanghai, China, respectively. Prominent microplastic stocks were found in atmospheric fallout, industrial wastewater, and domestic sewage. These stocks were much higher compared to crop farming wastewater, aquacultural wastewater, and livestock and poultry breeding wastewater. Total microplastic flows entering receiving water reached 3207.4 ± 1071.6 tons/a; the largest contributions were from wet weather overflow (23.7%), direct atmospheric fallout (21.7%), wastewater treatment plant effluent (14.2%), industrial wastewater (14.1%), and surface runoff (10.4%). Weather patterns led to divergent microplastic transmission pathways and mass flows, revealing a lagging timeline mode and illustrating the basic spatiotemporal features of microplastic contamination in urban agglomerations. Terminal disposal practices retained about two-fifths of the microplastic flows that would have otherwise been transmitted into receiving water. Of these, land surface sweep contributed half of the retained flow. Improvements in WWTP removal efficiency, storm sewage interception rate, industrial wastewater collection rate, and sewer sediment dredge rate could further enhance the systemic benefits.

An Inversion Framework for Optimizing Non‐Methane VOC Emissions Using Remote Sensing and Airborne Observations in Northeast Asia During the KORUS‐AQ Field Campaign

We aim to reduce uncertainties in CH2O and other volatile organic carbon (VOC) emissions through assimilation of remote sensing data. We first update a three‐dimensional (3D) chemical transport model, GEOS‐Chem with the KORUSv5 anthropogenic emission inventory and inclusion of chemistry for aromatics and C2H4, leading to modest improvements in simulation of CH2O (normalized mean bias (NMB): −0.57 to −0.51) and O3 (NMB: −0.25 to −0.19) compared against DC‐8 aircraft measurements during KORUS‐AQ; the mixing ratio of most VOC species are still underestimated. We next constrain VOC emissions using CH2O observations from two satellites (OMI and OMPS) and the DC‐8 aircraft during KORUS‐AQ. To utilize data from multiple platforms in a consistent manner, we develop a two‐step Hybrid Iterative Finite Difference Mass Balance and four‐dimensional variational inversion system (Hybrid IFDMB‐4DVar). The total VOC emissions throughout the domain increase by 47%. The a posteriori simulation reduces the low biases of simulated CH2O (NMB: −0.51 to −0.15), O3 (NMB: −0.19 to −0.06), and VOCs. Alterations to the VOC speciation from the 4D‐Var inversion include increases of biogenic isoprene emissions in Korea and anthropogenic emissions in Eastern China. We find that the IFDMB method alone is adequate for reducing the low biases of VOCs in general; however, 4D‐Var provides additional refinement of high‐resolution emissions and their speciation. Defining reasonable emission errors and choosing optimal regularization parameters are crucial parts of the inversion system. Our new hybrid inversion framework can be applied for future air quality campaigns, maximizing the value of integrating measurements from current and upcoming geostationary satellite instruments.

Computational Framework for Machine-Learning-Enabled 13C Fluxomics.

13C metabolic flux analysis (MFA) has emerged as a powerful tool for synthetic biology. This optimization-based approach suffers long computation time and unstable solutions depending on the initial guess. Here, we develop a machine-learning-based framework for 13C fluxomics. Specifically, training and test data sets are generated by metabolic network decomposition and flux sampling, in which flux ratios at metabolic nodes and simulated labeling patterns of metabolites are used as training targets and features, respectively. To improve prediction accuracy and simplify the model, automated processes are developed for flux ratio selection based on solvability and feature screening based on importance. We found that predictive performance can be significantly improved using both amino acids and central carbon metabolites in comparison with amino acids alone. Together with measured external fluxes, the predicted flux ratios determine the mass balance system, yielding global flux distributions. This approach is validated by flux estimation using both simulated and experimental data in comparison with canonical 13C MFA. The approach represents a reliable fluxomics method readily applicable to high-throughput metabolic phenotyping, which highlights the advances of intelligent learning algorithms in synthetic biology, specifically in the Test and Learn stage of the Design-Build-Test-Learn cycle.

Goldstino spectrum in an ultracold Bose-Fermi mixture with explicitly broken supersymmetry

We theoretically investigate a supersymmetric collective mode called Goldstino in a Bose-Fermi mixture. The explicit supersymmetry breaking, which is unavoidable in cold atom experiments, is considered. We derive the Gell-Mann--Oakes-Renner (GOR) relation for the Goldstino, which gives the relation between the energy gap at the zero momentum and the explicit breaking term. We also numerically evaluate the gap of Goldstino above the Bose-Einstein condensation temperature within the random phase approximation (RPA). While the gap obtained from the GOR relation coincides with that in the RPA for the mass-balanced system, there is a deviation from the GOR relation in the mass-imbalanced system. We point out the deviation becomes large when the Goldstino pole is close to the branch point, although it is parametrically a higher order with respect to the mass-imbalanced parameter. To examine the existence of the goldstino pole in realistic cold atomic systems, we show how the mass-imbalance effect appears in $^6$Li-$^7$Li, $^{40}$K-$^{41}$K, and $^{173}$Yb-$^{174}$Yb mixtures. Furthermore, we analyze the Goldstino spectral weight in a $^{173}$Yb-$^{174}$Yb mixture with realistic interactions and show a clear peak due to the Goldstino pole. As a possibility to observe the Goldstino spectrum in cold atom experiments, we discuss the effects of the Goldstino pole on the fermionic single-particle excitation as well as the relationship between the GOR relation and Tan's contact.

Rancang Bangun Sistem Pengendalian Level Pada Tangki Penyimpanan Menggunakan Degree Of Freedom Analysis Dengan Tunning PID Berdasarkan Metode Cohen-Coon

The storage tank is one of the most important operating units used in the generation process. This operating unit functions as water storage which will later be used as raw material for making steam. To maintain the mass balance system and the energy balance system in the storage tank, a proper control system is needed. One of the variables controlled in this operating unit is implementing a level control system. In a process control system, key knowledge is needed, namely determining the process variable (PV), manipulated variable (MV), and disturbance variable (DV). If it is wrong in determining the three types of variables, then the output from the control system that we provide is not by the value we want (setpoint). Analysis of degrees of freedom (DOF) is used to determine the number of manipulated variables in the storage tank operation unit. To determine the number of variable numbers and the number of equation numbers can be used by looking at the mathematical equation model of the storage unit operation. Meanwhile, to determine the number of variables used in the above equation is to choose the type of variable that affects the process if the variable is changed. PID tunning needs to be done to determine the best proportional, derivative, and integral constant values, which later the output we want is the same as the setpoint value. Cohen Coon is a PID tunning method that can tolerate a constant amplitude oscillation state. Cohen-Coon is trying to improve the oscillation method by using the quarter amplitude decay method. The closed-loop response system, in this method, is made so that the response is in the form of a quarter amplitude decay. Quarter amplitude decay is defined as a transient response whose amplitude in the first period has a ratio of one quarter (1/4).

Automatic mass balancing system for a dynamic CubeSat attitude simulator: development and experimental validation

This paper describes the automatic balancing and inertia identification system for three degrees of freedom CubeSat attitude simulator testbed. For a reliable verification of the attitude determination and control subsystem, the on-orbit environment shall be simulated within the testbed, minimizing the external disturbances acting on the satellite mock-up. The gravity torque is expected to be the largest among the disturbances, and an automatic balancing procedure can largely reduce the time necessary for tuning the platform and minimize the residual torque. The automatic balancing system adopted in this work employs three sliding masses independently actuated by three electric motors using a two-step procedure. In the first step, a feedback control is employed for a plane balancing. The inertia parameters and the remaining offset component are then estimated by collecting free oscillating platform data. This two-step procedure is iterated towards increasingly finer balancing until no further improvement is obtained. For the planar balancing, a control law based on linearized equations and a newly developed nonlinear feedback law is implemented and compared, showing the superior performance of the latter. The unbalance offset vector component along the local vertical and inertia tensor are estimated by a constrained batch least squares filter. Experimental results show the effectiveness of the implemented approach, which leads to a residual disturbance torque acting on the balanced platform smaller than 5 × 10–5 Nm.

A New Perspective is Required to Understand the Role of Forest Ecosystems in Global Mercury Cycle: A Review

Mercury (Hg) is one of the most toxic heavy metal pollutants, which can be easily transmitted and enriched through the food chain, posing severe threat to human beings. Forest ecosystems are one of the most active environments for biogeochemical cycles of Hg. It is essential to research on Hg cycling in the forest ecosystem, which contributes to a comprehensive understanding of global biogeochemical cycle of Hg. However, there is still a lack of consensus on whether the forest ecosystem is a "source" or "sink" of Hg in the global Hg cycle so far. Therefore, it is necessary to elucidate the current state of knowledge on Hg deposition, transformation and fate in the forest ecosystem, especially the existing puzzles or issues encountered by scientists worldwide. This review highlights the complexity and uncertainties of Hg cycling in forest ecosystems. It is proposed that a new perspective is required to further understand the role of forest ecosystems in global Hg cycle based on a sufficient understanding of Hg exchange fluxes at the interface of air-soil and air-plant, Hg deposition flux through litterfall, and accurate construction of Hg mass balance system.

Implementation of the Product Environmental Footprint Category Rules for dairy products: An approach to assess nitrogen emissions in a mass balanced dairy farm system

Following the Single Market for Green Products, the European Commission released the Product Environmental Footprint Category Rules for Dairy Products (PEFCR-D). According to the PEFCR-D, nitrogen (N) emissions must be calculated as stated by The Intergovernmental Panel on Climate Change (IPCC) and the European Environmental Agency (EMEP/EEA) methods. However, since the IPCC method and the EMEP/EEA method follow different N flows, the estimated N emissions differ at common farm stages resulting in incompatibilities in the reported PEFCR-D emissions from a mass balance perspective. This work proposes a comprehensive approach to calculate N emissions to satisfy the PEFCR-D guideline in a N balanced farm system. The proposed approach coordinates and balances the N flows at each stage in order to estimate the N emissions from the dairy system. In this regard, emissions such as N2O, NH3, NOx, N2 and NO3− are estimated following the IPCC and EMEP/EEA methods from a single N flow in the system. The N losses in the whole dairy farm are estimated to increase 4.41% as a result of the implementing the PEFCR-D in a N balanced system instead of a non-balanced one. Consequently, an increase in environmental impacts of the farm such as Global Warming Potential (6.68%), Marine Eutrophication (4.91%) and Terrestrial Eutrophication (4.26%) were also measured. Moreover, the proposed approach to implement the PEFCR-D enabled the redistribution of emissions between farm stages; particularly relocating N emissions and environmental impacts between manure management and application. This resulted in a decrement on the manure management stage environmental impacts such as Global Warming (−41.88%) and Photochemical Ozone formation (−25.49%). On the other hand, at application stage, increments in Global Warming (26.94%), Marine Eutrophication (8.48%) and Terrestrial Eutrophication (7.52%) were evidenced when contrasting the outcomes between the non-balanced and balanced PEFCR-D calculation approach.

Steady-state distributed modeling of dissolved oxygen in data-poor, sewage dominated river systems using drainage networks

The determination of water quality along a river drainage network is of paramount importance for many environmental applications. Whereas several codes have been proposed to deal with this problem along a single reach of a river, no simple solution has been proposed for a complex river network. In this contribution, a methodology is presented for preliminary screening of river water quality at the watershed-scale and at steady state. The solution process exploits the information contained within the watershed's space-filling drainage network (SFDN), that is automatically computed by processing the raster map of the watershed's elevations. To this end, a visiting algorithm for non-binary trees is coupled to a Newton-Raphson method that locally solves the system of nonlinear water-quality mass balances. We believe that the resulting framework will be especially valuable for initial screening analyses in data-poor watersheds. A free code called Q2T that implements the described methods is provided.

PID 컨트롤러를 이용한 우주선 시뮬레이터의 자동 밸런싱 시스템

PID 컨트롤러를 이용한 우주선 시뮬레이터의 자동 밸런싱 시스템

Methodology to determine the extent of anaerobic digestion, composting and CH4 oxidation in a landfill environment

An examination of the processes contributing to the production of landfill greenhouse gas (GHG) emissions is required, as the actual level to which waste degrades anaerobically and aerobically beneath covers has not been differentiated. This paper presents a methodology to distinguish between the rate of anaerobic digestion (rAD), composting (rCOM) and CH4 oxidation (rOX) in a landfill environment, by means of a system of mass balances developed for molecular species (CH4, CO2) and stable carbon isotopes (δ13C-CO2 and δ13C-CH4). The technique was applied at two sampling locations on a sloped area of landfill. Four sampling rounds were performed over an 18 month period after a 1.0 m layer of fresh waste and 30–50 cm of silty clay loam had been placed over the area. Static chambers were used to measure the flux of the molecular and isotope species at the surface and soil gas probes were used to collect gas samples at depths of approximately 0.5, 1.0 and 1.5 m. Mass balances were based on the surface flux and the concentration of the molecular and isotopic species at the deepest sampling depth. The sensitivity of calculated rates was considered by randomly varying stoichiometric and isotopic parameters by ±5% to generate at least 500 calculations of rOX, rAD and rCOM for each location in each sampling round. The resulting average value of rAD and rCOM indicated anaerobic digestion and composting were equally dominant at both locations. Average values of rCOM: ranged from 9.8 to 44.5 g CO2 m−2 d−1 over the four sampling rounds, declining monotonically at one site and rising then falling at the other. Average values of rAD: ranged from 10.6 to 45.3 g CO2 m−2 d−1. Although the highest average rAD value occurred in the initial sampling round, all subsequent rAD values fell between 10 and 20 g CO2 m−2 d−1. rOX had the smallest activity contribution at both sites, with averages ranging from 1.6 to 8.6 g CO2 m−2 d−1. This study has demonstrated that for an interim cover, composting and anaerobic digestion of shallow landfill waste can occur simultaneously.

Mass properties identification and automatic mass balancing system for satellite attitude dynamics simulator

A Satellite Attitude Dynamics Simulator is a low-cost, ground-based system made to simulate the conditions of a weightless satellite in space. The identification of the mass characteristics is crucial for Satellite Attitude Dynamics Simulator application and so the center of mass place is necessary for balancing the platform and moment of inertia which is a significant factor in designing controllers and selecting actuators. The purposes of this paper are the mass properties identification and design, experimentation, and validation of an automatic mass balancing system, which is assembled on the Satellite Attitude Dynamics Simulator at the Space Research Laboratory. This paper presents a process of mass properties estimation for the Satellite Attitude Dynamics Simulator using classical Levenberg–Marquardt as an optimization method. By employing this technique lack of repeatability and difficulties in implementation will be eliminated. In order to verify this technique, a MATLAB® SIMULINK® model of the Satellite Attitude Dynamics Simulator is established. The gap between the center of mass and center of rotation is decreased by means of the automatic mass balancing system in order to remove gravity disturbance. The results of this identification process are compared to the recursive least square algorithm, which is commonly employed in identification of mass properties. The analytical and experimental results prove that the proposed characteristic estimation process using classical Levenberg–Marquardt algorithm is more effective and appropriate. Proper excitation of the platform will guarantee the accuracy of estimation and compensation of the center of gravity offset utilizing the balancing system.

A New Approach to Compensate Oscillations of Path-Linked Presses Caused by Inertial Forces

Presses with mechanical linkages based on levers between motor and ram (path-linked presses) tend to oscillate due to inertial forces as a consequence of the drive parts motion.In this publication a new approach for a mass-balancing system is presented. This system allows to generate the optimal compensation forces needed to counteract the inertial forces by means of four linear motors. The control signals for the linear motors are specified by an evolutionary optimization algorithm, which operates on the base of measured accelerations of the press frame. The control signals of the linear motors are created in a way that the machines oscillations are reduced to a minimum. This way the presented mass-balancing system adapts itself automatically to varying conditions during the operation of the machine, such as a tool change or a varying stroke rate.In particular, the present publication provides the results of the conceptual design and the virtual testing of this approach, which has been mainly carried out with the help of multiple-body simulations.

Difference schemes based on the support operator method for fluids dynamics problems in a collector containing gas hydrates

Difference schemes based on the support operator method are considered as applied to fluid dynamics in underground collectors containing gas hydrate deposits. A system of mass and energy balances describing fluid dynamics in a porous medium containing gas hydrate deposits is given. A dissipative hydrate equation is derived that determines the thermodynamic evolution of the parameters of the system. It is shown that the jumps in specific volumes and internal energy occurring in phase transitions play a crucial role in the stability of the evolution of the system in the dissipation thermodynamic module of the system. A family of rotation-invariant difference schemes of the support operator method on unstructured meshes is constructed for numerical computations. The schemes are tested on a series of model problems. Their numerical solutions are presented.

Zero-temperature equation of state of mass-imbalanced resonant Fermi gases.

We calculate the zero-temperature equation of state of mass-imbalanced resonant Fermi gases in an abinitio fashion, by implementing the recent proposal of imaginary-valued mass difference to bypass the sign problem in lattice MonteCarlo calculations. The fully nonperturbative results thus obtained are analytically continued to real mass-imbalance to yield the physical equation of state, providing predictions for upcoming experiments with mass-imbalanced atomic Fermi gases. In addition, we present an exact relation for the rate of change of the equation of state at small mass imbalances, showing that it is fully determined by the energy of the mass-balanced system.

Can satellite land surface temperature data be used similarly to river discharge measurements for distributed hydrological model calibration?

A new methodology is proposed for the calibration of distributed hydrological models at the basin scale by constraining an internal model variable using satellite data of land surface temperature (LST). The model algorithm solves the system of energy and mass balances in terms of a representative equilibrium temperature that governs the fluxes of energy and mass over the basin domain. This equilibrium surface temperature, which is a critical model state variable, is compared to operational satellite LST, while calibrating soil hydraulic parameters and vegetation variables differently in each pixel, minimizing the errors. This procedure is compared to the traditional calibration using only discharge measurements. The distributed energy water balance model, Flash-flood Event-based Spatially-distributed rainfall–runoff Transformation – Energy Water Balance model (FEST-EWB), is used to test this approach. This methodology is applied to the Upper Yangtze River basin (China) using MODIS LST retrieved from satellite data in the framework of the NRSCC-ESA DRAGON-2 Programme. The calibration procedure based on LST seems to outperform the calibration based on discharge, with lower relative error and higher Nash-Sutcliffe efficiency index on cumulated volume.Editor D. Koutsoyiannis; Associate editor C. Perrin

냉매 R1234yf의 모세관내 유동 특성에 관한 해석적 연구

R1234yf has been developed as an alternative refrigerant to R134a, which has been associated with global warming. The capillary tubes as expansion valves control the mass flow rate and balance system pressure in the refrigeration cycle. The present numerical model used the governing equations including the law of conservation of mass, momentum, and energy in a capillary tube. The mass flow rate of R1234yf decreased by 47.0% as the capillary tube length was increased from 1 to 4 m. As the inner diameter of the capillary tubes was changed from 1.3 to 1.7 mm, the mass flow rate of R134a and R1234yf increased by 117.9% and 121.0%, respectively. The mass flow rate of the R134a and R1234yf increased by 28.3% and 29.1% with subcooling increasing from 0 to 7°C. In addition, when the inlet temperature of the capillary tubes was changed from 35 to 60°C, the mass flow rate of R134a and R1234yf increased by 31.0% and 45.4%, respectively.

The politics of European agencements: constructing a market of sustainable biofuels

The sustainability of biofuels has been the subject of heated debates in Europe. The 2009 Renewable Energy Directive (RED) introduced criteria meant to define whether biofuels are sustainable. These criteria, relating to the level of greenhouse gas emissions and the types of land used to produce biofuels, are expected to be implemented through certification schemes associating private companies and public bodies (whether national or European). Using recent works in the sociology of markets, I consider these sustainability schemes as agencements, a lens for the study of the construction of a market in sustainable biofuels and for the analysis of European integration. I focus on the mass balance system, which, meant to track the circulation of biofuels qualified as sustainable, is a compromise, implemented at the price of pervasive uncertainties and difficulties. The European political and economic organisation is at stake in discussions related to the extent of the control exercised through the sustainability schemes by virtue of the mass balance system, and a politics of subsidiarity and a politics of harmonisation are at the heart of the making of a European market for sustainable biofuels. The description of the agencements organising European markets in sustainable biofuels points to the importance of coexistence as an economic and political operation.