Entropy Flow Research Articles

Dissipation-Time Uncertainty Relation.

We show that the entropy production rate bounds the rate at which physical processes can be performed in stochastic systems far from equilibrium. In particular, we prove the fundamental tradeoff ⟨S[over ˙]_{e}⟩T≥k_{B} between the entropy flow ⟨S[over ˙]_{e}⟩ into the reservoirs and the mean time T to complete any process whose time-reversed is exponentially rarer. This dissipation-time uncertainty relation is a novel form of speed limit: the smaller the dissipation, the larger the time to perform a process.

Understanding the 3D construction method of thermodynamic cycle: Insights from limiting performance of pure working fluid

The 2D temperature-entropy diagram, which is commonly applied to construct and analyze conventional thermodynamic cycles, cannot clearly express novel thermodynamic cycles with multi-working fluids. The 3D construction method provides a methodological guidance to the construction and analysis of novel thermodynamic cycles. In order to understand the mechanism of the 3D construction method, in this study, the limiting performance of 3D thermodynamic cycle with pure working fluid is analyzed and compared with the limiting performance of organic Rankine cycle. Based on the diagram of the 3D coordinates in terms of temperature, entropy, and mass flow rate, the 3D limiting thermodynamic cycle is defined and decoupled into two limiting organic Rankine cycle first. Then, equations of limiting thermal efficiency and thermodynamic perfection are derived based on pure working fluid. Three parameters affecting limiting performance are revealed, namely the latent heat, the slope of the saturated liquid line in the temperature-entropy diagram, and the separation quality. Lastly, effects of key operating parameters on the limiting efficiency of the 3D cycle are analyzed. With the increase of high temperature or middle temperature, the limiting thermal efficiency increases, and thermodynamic perfection increases first and then declines. With the increase of separation quality, the limiting thermal efficiency shows a downward trend. However, the trend of thermodynamic perfection with separation quality depends on values of high temperature and middle temperature. Besides, the limiting performance between the 3D cycle and conventional organic Rankine cycle is compared. The limiting thermodynamic perfection of 3D cycle using R245fa is 7.3%-16.42% higher than that of conventional organic Rankine cycle.

Key Frames Extraction Based on Optical-flow and Mutual Information Entropy

Key frames provide a suitable video summary and framework for video indexing, browsing and retrieval, and how to extract key frames is the core in the field of video retrieval. In order to solve the problem of redundancy and missing selection in key frame extraction, this paper proposed a key frame extraction algorithm based on optical flow and mutual information entropy. This algorithm integrates mutual information entropy and optical flow characteristics to extract key frames. First, the optical flow method calculated the total optical flow of each frame of the image, and selected the video frame with extreme optical flow difference in the neighbourhood as the key frame, and the other video frames were put into the candidate key frame set; by calculating the mutual information entropy of the key frame set, the minimum mutual information entropy is taken as the threshold; Then, The mutual information entropy of the candidate key frame set was calculated, and the image frames larger than the threshold value were put into the key frame set; Finally, redundant key frames are deleted through the measurement of inter-frame similarity, and the remaining key frames are the key frames to be extracted. The experimental results show that compared with other methods, the accuracy of extracted key frames by this approach is significantly improved on precision, recall and F-score, and the extracted key frames can reflect video content more effectively.

Formularization of entropy and anticipation of metastable states using mutual information in one-dimensional traffic flow

Both macro and micro states of Newtonian particles are used to define entropy. However, in previous research studies, which focused on traffic flow from the perspective of thermodynamics and information theory, researchers did not fully determine how entropy can be defined for self-driven particles that do not satisfy Newton’s laws. One attempt to formularize entropy in a one-dimensional traffic flow has been based on information theory. Entropy has been defined by focusing only on the location variation of the vehicles but not on the velocity variation of the vehicles. Moreover, no study has succeeded in considering the time evolution of entropy in a self-driven particle system. In this study, we redefine the entropy and mutual information in one-dimensional traffic flow from the information theoretical perspective, focusing on the velocity variation of vehicles. Moreover, we advance the thermodynamic analysis of one-dimensional traffic flow by examining the time evolution of the new formularized entropy. To observe the time evolution of the formularized entropy, we conducted numerical simulations using both stochastic optimal velocity (SOV) and zero-range process with a slow-start-rule (ZRP+SLS) models that can reproduce a metastable state, which occurs before the congestion begins at a high average velocity and short headway. Moreover, we used the mutual information to anticipate a metastable state – a sign of congestion – by calculating experimental data from three following vehicles on a real expressway to demonstrate the practical application of the formularized mutual information. Thus, we analyzed traffic flow both macroscopically and microscopically using the new formularized entropy to contribute to the studies of self-driven particle systems in both ways of thermodynamics and statistical mechanics or information theory.

Thermodynamic Parameters of the Viscous Flow in the Aqueous Solutions of Polyols

Data experimentally obtained for the kinematic viscosity are used to calculate the thermodynamic characteristics of viscous flows in some polyols and their aqueous solutions. The solutions of glycerol, erythritol, xylitol, adonite, sorbitol, mannitol, and dulcite are studied, as well as the melts of erythritol, xylitol, and sorbitol. The entropy, enthalpy, and free energy of the viscous flow are calculated in the framework of the theory of reaction rate constants. A linear dependence between the true entropy and the enthalpy of the viscous flow in the researched systems is found, which allowed us to determine the isokinetic temperature, calculate the transmission coefficient, draw a conclusion about the mechanisms of bond formation in the reaction centers of active complexes, and estimate the vibration energy of those bonds.

Development and validation of a sample entropy-based method to identify complex patient-ventilator interactions during mechanical ventilation

Patient-ventilator asynchronies can be detected by close monitoring of ventilator screens by clinicians or through automated algorithms. However, detecting complex patient-ventilator interactions (CP-VI), consisting of changes in the respiratory rate and/or clusters of asynchronies, is a challenge. Sample Entropy (SE) of airway flow (SE-Flow) and airway pressure (SE-Paw) waveforms obtained from 27 critically ill patients was used to develop and validate an automated algorithm for detecting CP-VI. The algorithm’s performance was compared versus the gold standard (the ventilator’s waveform recordings for CP-VI were scored visually by three experts; Fleiss’ kappa = 0.90 (0.87–0.93)). A repeated holdout cross-validation procedure using the Matthews correlation coefficient (MCC) as a measure of effectiveness was used for optimization of different combinations of SE settings (embedding dimension, m, and tolerance value, r), derived SE features (mean and maximum values), and the thresholds of change (Th) from patient’s own baseline SE value. The most accurate results were obtained using the maximum values of SE-Flow (m = 2, r = 0.2, Th = 25%) and SE-Paw (m = 4, r = 0.2, Th = 30%) which report MCCs of 0.85 (0.78–0.86) and 0.78 (0.78–0.85), and accuracies of 0.93 (0.89–0.93) and 0.89 (0.89–0.93), respectively. This approach promises an improvement in the accurate detection of CP-VI, and future study of their clinical implications.

The optimal defrosting condition of an air source heat pump based on entropy analysis

ABSTRACT In winter, the heat transfer characteristics and energy efficiency of air source heat pumps (ASHP) will deteriorate due to the frost forming on the surface of the evaporator. In order to recover the thermal performance of the heat exchanger, defrosting is necessary. The optimal defrosting condition is one of the crucial factors to achieve efficient operation of ASHP. However, most previous control strategies are only devoted to the change of experimental parameters after frosting and influence on the heat transfer performance of the heat exchanger, and pay no attention to the influence of the frosting process on the energy transfer between air and refrigerant. These methods cannot achieve the high efficiency of system energy utilization. Thus, this study investigated the feasibility of using the entropy analysis control method to seek the optimal defrost conditions. Firstly, the trend of the temperature difference and the frictional pressure drop (PTP) as the key parameters of entropy generation analysis is developed. Secondly, based on the minimum principle of entropy generation and entropy resistance, the optimal defrost conditions of the evaporator under frosting conditions are studied. Finally, experiments are carried out to verify the optimal defrost parameters for the entropy analysis control method using the proportion of the temperature difference and the drop (PTP. Results indicate that due to the formation of frost, the entropy flow and entropy production caused by the temperature difference and pressure drop show a negative correlation trend, which makes the entropy generation and entropy resistance show decreasing trend initially and then increasing. Simultaneously, the irreversibility distribution ratio is approximately 1 and the minimum of the entropy generation and entropy resistance was achieved. Hence, the minimum irreversible degree and the peak of the energy efficiency can be obtained. It can be determined that the proportion of the temperature difference and the PTP can be used as irrational for defrosting control parameters. When the proportion of the temperature difference and the PTP is approximately 0.8, the system entropy generation and entropy resistance are the smallest. It is verified that the defrosting strategy of evaporator based on entropy analysis can realize the optimal heat transfer performance, the highest heat transfer efficiency, and the high-efficiency operation in the low-temperature environment of the ASHP system.

Detection of probe flow anomalies using information entropy and random forest method

Aiming at the problems of excessive dependence on manual work, low detection accuracy and poor real-time performance of current probe flow anomaly detection in power system network security detection, a detection method for calculating information entropy of probe flow and random forest classificat ion is proposed. Firstly, the network probe stream data are captured and aggregated in real-time to extract network stream metadata. Secondly, by calculating Pearson correlation coefficient and maximum mutual information coefficient, feature selection of network metadata is carried out. Finally, the information entropy and stochastic forest algorithm are combined to detect the anomaly of probe traffic based on the selected key feature groups, and the probe traffic is accurately classified by multiple incremental learning. The results show that the proposed method can quickly locate the abnormal position of probe traffic and analyze the abnormal points, which greatly reduces the workload of application platform for power system security monitoring, and has high detection accuracy. It effectively improves the reliability and early warning ability of power system network security.

Nonlinear Onsager relations for Gaussian quantum maps

Onsager's relations allow one to express the second law of thermodynamics in terms of the underlying associated currents. These relations, however, are usually valid only close to equilibrium. Using a quantum phase space formulation of the second law, we show that open bosonic Gaussian systems also obey a set of Onsager relations, valid arbitrarily far from equilibrium. These relations, however, are found to be given by a more complex non-linear function, which reduces to the usual quadratic form close to equilibrium. This non-linearity implies that far from equilibrium, there exists a fundamental asymmetry between entropy flow from system to bath and vice-versa. The ramifications of this for applications in driven-dissipative quantum optical setups are also discussed.

Bowen entropy of sets of generic points for fixed-point free flows

Let (X,ϕ) be a compact metric flow without fixed points. We will be concerned with the entropy of flows which takes into consideration all possible reparametrizations of flows. In this paper, by establishing the Brin–Katok's entropy formula for flows without fixed points in the non-ergodic case, we prove the following result: for an ergodic ϕ-invariant measure μ,htopB(ϕ,Gμ(ϕ))=hμ(ϕ1), where Gμ(ϕ) is the set of generic points for μ and htopB(ϕ,Gμ(ϕ)) is the Bowen entropy on Gμ(ϕ). This extends the classical result of Bowen in 1973 to fixed-point free flows. Moreover, it is shown that the Bowen entropy can be determined via the local entropies of measures.

Research on Evaluating the Sustainable Operation of Rail Transit System Based on QFD and Fuzzy Clustering.

The purpose of this study is to evaluate the sustainable operation of rail transit system. In rail transit system, as the most important aspect of negative entropy flow, the effective strategy can offset the increasing entropy of the system and make it have the characteristics of dissipative structure, so as to realize the sustainable operation. At first, this study constructs the Pressure-State-Response (PSR) model to evaluate the sustainable operation of rail transit system. In this PSR model, “pressure” is viewed as customer requirements, which answers the reasons for such changes in rail transit system; “state” refers to the state and environment of system activities, which can be described as the challenges of coping with system pressure; “response” describes the system’s actions to address the challenges posed by customer needs, namely operational strategies. Moreover, then, 13 pressure indices, five state indices and 11 response indices are summarized. In addition, based on quality function deployment (QFD), with 13 pressure indices as input variables, five state indices as customer requirements (CRs) of QFD and 11 response indices as technical attributes (TAs) of QFD, this study proposed the three-phase evaluation method of the sustainable operation of rail transit system to obtain the operational strategy (that is, negative entropy flow): The first phase is to verify that 13 pressure indices can be clustered into five state indices by fuzzy clustering analysis; The second phase is to get the weights of five state indices by evidential reasoning; The third phase is to rate the importance of 11 response indices by integrating fuzzy weighted average and expected value operator. Finally, the proposed model and method of evaluation are applied to the empirical analysis of Shanghai rail transit system. Finally, we come to the conclusion that Shanghai rail transit system should take priority from the following five aspects: “advancement of design standards”, “reliability of subway facilities”, “completeness of operational rules”, “standardization of management operation” and “rationality of passenger flow control”.

Measures of maximal entropy for suspension flows

We study suspension flows defined over sub-shifts of finite type with continuous roof functions. We prove the existence of suspension flows with uncountably many ergodic measures of maximal entropy. More generally, we prove that any suspension flow defined over a sub-shift of finite type can be perturbed (by an arbitrarily small perturbation) so that the resulting flow has uncountably many ergodic measures of maximal entropy, and that the same can be arranged so that the new flow has a unique measure of maximal entropy.

Risk identification method of power grid division based on power flow entropy

This research introduced a new way to identify the weak area of power grid by the maximum entropy increase. The stable quantification of grid is judged by weighted power flow entropy index. The index of weighted power flow entropy can quantitatively evaluate the ordered stability degree of system key facts. A large number of simulation calculations of IEEE39 node system show that when the entropy of weighted power flow increases to 40-50% or more, the power grid is easy to enter the self-organized critical state, that is, the risk of blackout increases significantly. This paper studies the influence of the load growth in different regions on the entropy index of the whole system, and selects the region with the largest entropy increase as the weak region. The feasibility and effectiveness of the proposed method are verified by taking an actual power grid as an example.

Automatic Detection of Movement Inception During Hand Gesture

Hand movement recognition based on ElectroMyographic signals is a crucial subject frequently addressed using feature extraction and classifiers such as neuronal networks. However, there is no model to allow automatic movement inception using superficial ElectroMyographic signals; in the present paper is presented a solution to the above problem. To understand the beginning of movement permits the start of other systems for different applications such as activation of human-machine interface, wearable devices among others, this allows saving energy in terms of computation cost, because only at the right moment the system will activate. The mathematical model presented uses the principle of a) superficial EMG signal model, b) the entropy, and c) the flow entropy. The synergy between all the above elements enables the determination of the produced information rate to track significant variation and causing sharp peaks in the entropy flow. The occurrence of each positive peak in the entropy flow corresponds to a movement begging and the occurrence time of each negative peak corresponds to a movement termination. The model was validated through an experimental procedure using a wearable device, in this case, it is used the MyoArmBand as device for subjects to perform release and grasp gestures. As a result, it is found that the proposed model can automatically detect the beginning of the movements at approximately 245.9ms. This value of time change depends on the device used due to connection systems and the computing capacity. Moreover, the proposed procedure can be implemented using other wearable devices as smart watches, smart bands, smart t-shirts, or others instruments that measure the electrical activity.

On the Entropy of Flows with Reparametrized Gluing Orbit Property

We show that a flow or a semiflow with a weak form of reparametrized gluing orbit property has positive topological entropy if it is not minimal.

Spatiotemporal dynamics of a buoyancy-driven turbulent fire.

We numerically study the spatiotemporal dynamics and predictability of a buoyancy-driven turbulent fire. A significant transition from order to disorder structures can be observed from the mean degree in the spatial horizontal visibility graph. The gravitational term (baroclinic torque term) in the vorticity equation has a significant impact on the formation of the order (disorder) structure in the near field (far field). The entropy flow transport from temperature to flow velocity fluctuations is predominant near the interface between hot combustion products and ambient air. The transfer entropy is an important measure for determining the predictability of flow velocity fluctuations in the near field obtained by reservoir computing.

Studies of boundary entropy in AdS/BCFT

In this paper we review the AdS/BCFT proposal of Takayanagi for holographic description of systems with boundaries, in particular, boundary conformal field theories (BCFTs). Motivated by better understanding of the proposed duality we employ entanglement entropy as a probe of familiar properties of impurities and defects. Using the dual gravity description, we check that in two spacetime dimensions the impurity entropy does not depend on a particular state of the theory, which is a well-known CFT result. In three dimensions different, and not necessarily equivalent, definitions of the defect entropy can be given. We compute the entanglement entropy of a line defect at finite temperature and compare it with earlier calculations of the thermodynamical entropy. The results indicate that the entanglement entropy flows to the definition of the entropy as the Bekenstein–Hawking entropy associated to a portion of the black horizon, which we call impurity ‘shadow’. Geometric configurations, which we discuss, provide examples of RG flows of the defect entropies. We outline the connection between the geometric picture of the RG flows and examples of lattice calculations. We also discuss some new generalizations of the AdS/BCFT geometries.

Origin of life: a theory of fundamental universal structure of life

In this article, the universal structure of life is aimed to be clarified. We assert that the life is a double-structured system. As fundamental layer of the life, thermodynamically non-equilibrium circulative process is working. In the flow of entropy from sun, intermediating earth, to the cold universe, living system disposes the entropy produced in the living process. The upper layer of the living system is structured by the process of information-based ordering. As the physical system becomes too complicate, the physical ambiguity emerges, where the minimum energy principle of physics cannot determine the physical state uniquely. When this “open state space” emerges, the possibility of encoding the symbol to the state freely from the energy constraint comes out. The selection action between the open states is evaluated by the fitness of result of the action. The open state become stochastically biased because of the difference of fitness of each state, and the information of each state by the definition of Shannon comes out. Systemization based on the information amount of each component and information transmission between the components becomes possible. Selection action becomes to evaluate the present action to select from the fitness of future. Thus, biological temporality which flow from future to present emerges. In conclusion, life is double-structured system which is constructed based on “future intentionality” which produces the “biological” temporality.

Adsorption thermodynamics and performance indicators of selective adsorbent/refrigerant pairs

Adsorbed phase thermodynamics and isosteric heat of adsorption of adsorbent/refrigerant pairs have immense importance in predicting the system performance of an adsorption heat pump. In this study, six potential adsorbent/adsorbate pairs - Maxsorb III/ethanol, PR_KOH4/ethanol, SAC2/R32, Maxsorb III/R152a, H2-treated Maxsorb III/ethanol, and Maxsorb III/propane are compared using a well-established model for determining heat of adsorption. Temperature-entropy (T-s) maps as a function of pressure, temperature, and adsorption uptake were plotted. It was observed that at a fixed temperature (303 K) the adsorbed phase entropy had an increasing trend with the increment of adsorbate uptake for all the studied pairs. Adsorption cooling cycles were plotted in the temperature-entropy maps for a specific cooling condition. Moreover, the entropy flow for different pairs suggested the minimum required driving force. The theoretical coefficient of performance and specific cooling effect were computed for all the pairs. This comparative analysis is important for choosing the suitable adsorbent/adsorbate pair for a particular heat pump application.

Optimization of Wind Power Configuration in Distribution Network Based on Scenario Clustering and Power Flow Entropy

Optimization of Wind Power Configuration in Distribution Network Based on Scenario Clustering and Power Flow Entropy