Transfer Operator Research Articles

Efficient GPU implementation of the multivariate empirical mode decomposition algorithm

An efficient GPU implementation of the Multivariate Empirical Mode Decomposition (MEMD) method is presented for speeding up the process of decomposing non-stationary multi-channel bioelectric signals into different oscillation modes. Each step of the MEMD algorithm is designed with performance in mind and implemented to remove all unnecessary overheads caused by CPU-GPU communication, data transfer operations and synchronisation. The implementation is validated with synthetic and real EEG signals of different lengths and channels (up to 128 channels) on different GPU cards, and compared to existing serial MEMD implementations. The final implementation achieved between 180x-430x speedup compared to MATLAB and a 10x improvement over the only known existing GPU implementation. The average decomposition error of our implementation is below 1.2 %. Our GPU program is the fastest known GPU implementation of the MEMD algorithm that reduces execution time from hours to seconds and as such makes it possible to perform MEMD time-frequency analysis of high-density EEG (MEG) or similar multi-channel signals in a fraction of time and opens the road towards its practical applicability.

Thermodynamical and spectral phase transition for local diffeomorphisms in the circle

It is known that all uniformly expanding dynamics have no phase transition with respect to Hölder continuous potentials. In this paper we show that given a local diffeomorphism f on the circle, that is neither a uniformly expanding dynamics nor invertible, the topological pressure function is not analytical. In other words, f has a thermodynamic phase transition with respect to geometric potential. Assuming that f is transitive and that Df is Hölder continuous, we show that there exists such that the transfer operator , acting on the space of Hölder continuous functions, has the spectral gap property for all and has not the spectral gap property for all . Similar results are also obtained when the transfer operator acts on the space of bounded variations functions and smooth functions. In particular, we show that in the transitive case f has a unique thermodynamic phase transition and it occurs in t 0. In addition, if the loss of expansion of the dynamics occurs because of an indifferent fixed point or the dynamics admits an absolutely continuous invariant probability with positive Lyapunov exponent then

Facile synthesis of ZIF-8 modified PES beads with improved sorption characteristics for elimination of Congo red from aquatic stream

The adsorption is a well know mass transfer operation that was employed for more than decades in water industry. Predominately carbon based, inorganic materials and MOF etc. have been widely employed as an adsorbent. In contrast in the present study polymeric nano beads incorporated with MOF were synthesized for efficient adsorption performances. The polymeric beads were obtained from Polyethersulfone (PES) and was incorporated with ZIF-8. In the inception phase, ZIF-8 incorporated PES polymeric beads were prepared through non-solvent induced phase separation (NIPS) process to discern the factors governing the adsorption mechanism. The zeta potential analysis showed that adding ZIF-8 into the PES matrix changed the charge from negative to positive. The ZIF-8@PES showed a maximum adsorption efficiency of 99.7% for CR dye removal compared to 14% of unmodified PES. The enhanced CR removal due to ZIF-8 addition was specifically due to π-π interactions between the linker and CR molecules, open Zn metal sites and electrostatic attraction. The sorption followed the Langmuir isotherm and Elovich kinetic model. The performance and regeneration studies showed that the modified beads were 91.1% efficient up to 4 cycles.

Issues of Improvement and Reorganization of Russian-Chinese Trade in the Notes and Projects of its Participants

The article is devoted to the projects of the Siberian merchants to improve the Russian-Chinese trade through changes in its organization to attract more participants, transfer operations to Chinese and Mongolian territories, and develop transport infrastructure. Particular attention is paid to proposals for the unification of merchant capital for the development of commercial development of Southeast Asia and the Pacific region. Even in the initial period of the Russian-Chinese bargaining, projects of the Irkutsk vice-governor L. Lang and Governor A. Bril appeared, proposing to create a single merchant company under the auspices of the state, like the East India Companies of England and Holland. Further projects were devoted to the transfer of trade to the territory of the Qing Empire, the expansion of the social composition of participants through the formation of merchant companies. The analysis of merchant notes and projects allows us to speak of their authors as creative and experienced entrepreneurs seeking to expand Russian-Chinese trade ties and strengthen the empire's position on the southeastern borders of Russia.

Cloud type identification algorithm to simulate MSG infrared radiance using the Radiative Transfer Model RTTOV and ALADIN forecasting output

In numerical weather prediction (NWP), the big challenger in satellite data assimilation is the presence of cloud essentially the convective cloud. In this work, we focus only on the simulation of SEVIRI radiances of MSG2 satellite, using the radiative transfer operator RTTOV in its 9.3 version, by introducing the fields provided by the model ALADIN/Algeria. This simulation can have two objectives. The first one is the validation of the simulated radiances for data assimilation; the second one is to generate synthetic images that will serve as a help tool to the localization of the storms using the short time forecast. Many improvements have been made in the source code for these operators in order to try to resolve this problem. This latest model RTTOV assimilates cumuliform clouds, stratiform clouds and the ones of the upper levels as cirrus. For the simulation of these clouds, we will developed an algorithm for the identification of cloud types and cloud structure, based on the vertical profile of the cloud liquid water (CLW) and the cloud solid water (CSW) forecasted by ALADIN model at all the forty three (43) levels of the RTTOV model. A comparative study using the MSG2 data has shown on a number of weather situations, a good correlation between simulated and observed radiances, but this correlation is locally random for isolated clouds.

Complete population transfer between next-adjacent energy levels of a transmon qudit

The utilization of qudits in quantum systems has led to significant advantages in quantum computation and information processing. Therefore, qudits have gained increased attention in recent research for their precise and efficient operations. In this work, we demonstrate the complete population transfer between the next-adjacent energy levels of a transmon qudit using the Pythagorean coupling method and energy level mapping. We achieve a |0〉 to |2〉 transfer with a process fidelity of 97.76% in the subspace spanned by |0〉 to |2〉. Moreover, the transfer operation is achieved within a remarkably fast timescale, as short as 20 ns. This study may present a promising avenue for enhancing the operation flexibility and efficiency of qudits in future implementations.

A multi-objective decision method for the network security situation grade assessment under multi-source information

Grade assessment of network security situation is summarized as a typical multi-index grade assessment problem. However, the existed methods for grade assessment of network security situation do not consider multi-source information such as the trust information among experts, the preference information among companies and heterogeneous information of companies. The above problems are unable to be solved through traditional assessment methods. The aim of this paper is to establish a novel multi-objective decision model for the grade assessment of network security situation under multi-source information. On the basis of describing the grade assessment problem of network security situation, the membership functions of four-type thresholds for the grades on attribute eigenvalue are put forward. Two trust information uncertainty degrees in social network are defined, and the trust transfer operator based on trust information uncertainty degree and multi-path trust integration method based on the variable weight function is proposed. Afterwards, a new method to generate the incomplete social network is used to identify the weights of experts. Then, a multi-objective decision grade assessment optimization model is further established to obtain the network security situation grades and grade discrimination based on the two-tuple linguistic operator. The proposed method provides a theoretical basis for constructing and testing the grade assessment of network security situation. Meanwhile, it develops the grade assessment system of advanced network security situation and improves the ability to protect network security.

An experimental setup for investigating the blowdown of liquid CO2 down to -50°C

In many Carbon Capture and Storage (CCS) technologies, CO2 is transported in a dense phase between 1 and 10 MPa, depending on the temperature. Previous investigations demonstrated that major accidents may occur during transportation or transfer operations in case of vessel or pipe depressurization to the atmosphere. Amongst the scenarios potentially leading to this, tank blowdown is a major concern due to two factors: the risk of brittle rupturing caused by low temperatures and the possibility of dry ice formation in the piping. Current flow models cannot properly model this, and further experimental evidence and detailed data are required.To provide the required information, a specific experimental setup was developed and tested. The tank is a 2 m3 sphere, carefully insulated and connected to a 40 mm diameter, 3 m long release pipe terminated by a discharge orifice to control the depressurization rate. The pipe can be connected either on the side of the vessel to release the gaseous phase or at the bottom to release the liquid phase.Optic ports are provided on the vessel and on the pipe to observe phase transition and monitor the liquid level. The instrumentation is a set of pressure transducers and arrays of thermocouples inside the CO2 and in the shell of the vessel. The tank is continuously weighed during the blowdown and the data are treated so that the mass flowrate can be obtained.The performance of the system is discussed based on a gaseous phase blowdown starting from a half-filled vessel with liquid CO2 at -38 °C and 1 MPa. Detailed data are presented and discussed. All phases - liquid, gas, and solid - appeared during the release, and temperatures dropped to nearly -80 °C in the shell and lasted for hours.

Multifunctional Motion Sensing Enabled by Laser-Induced Graphene.

The development of flexible sensors based on laser-induced graphene (LIG) has recently attracted much attention. It was commonly generated by laser-ablating commercial polyimide (PI). However, the weak mechanical extensibility of PI limits the development and diversified applications of LIG-based sensors. In this work, we adopted medical polyurethane (PU) tapes to peel off the LIG generated on PI and developed flexible and wearable sensors based on the proposed LIG/PU composite structure. Compared with other methods for LIG transfer, PU tape has many advantages, including a simplified process and being less time-consuming. We characterized the LIG samples generated under different laser powers and analyzed the property differences introduced by the transfer operation. We then studied the impact of fabrication mode on the strain sensitivity of the LIG/PU and optimized the design of a LIG/PU-based strain sensor, which possessed a gauge factor (GF) of up to 263.6 in the strain range of 75-90%. In addition, we designed a capacitive pressure sensor for tactile sensing, which is composed of two LIG/PU composite structures and a PI space layer. These LIG flexible devices can be used for human motion monitoring and tactile perception in sports events. This work provides a simple, fast, and low-cost way for the preparation of multifunctional sensor systems with good performance, which has a broad application prospect in human motion monitoring.

The generalized IFS Bayesian method and an associated variational principle covering the classical and dynamical cases

We introduce a general IFS Bayesian method for getting posterior probabilities from prior probabilities, and also a generalized Bayes' rule, which will contemplate a dynamical, as well as a non-dynamical setting. Given a loss function , we detail the prior and posterior items, their consequences and exhibit several examples. Taking Θ as the set of parameters and Y as the set of data (which usually provides random samples), a general IFS is a measurable map , which can be interpreted as a family of maps . The main inspiration for the results we will get here comes from a paper by Zellner (with no dynamics), where Bayes' rule is related to a principle of minimization of information. We will show that our IFS Bayesian method which produces posterior probabilities (which are associated to holonomic probabilities) is related to the optimal solution of a variational principle, somehow corresponding to the pressure in Thermodynamic Formalism, and also to the principle of minimization of information in Information Theory. Among other results, we present the prior dynamical elements and we derive the corresponding posterior elements via the Ruelle operator of Thermodynamic Formalism; getting in this way a form of dynamical Bayes' rule.

Understanding recent deep‐learning techniques for identifying collective variables of molecular dynamics

AbstractHigh‐dimensional metastable molecular dynamics (MD) can often be characterised by a few features of the system, that is, collective variables (CVs). Thanks to the rapid advance in the area of machine learning and deep learning, various deep learning‐based CV identification techniques have been developed in recent years, allowing accurate modelling and efficient simulation of complex molecular systems. In this paper, we look at two different categories of deep learning‐based approaches for finding CVs, either by computing leading eigenfunctions of transfer operator associated to the underlying dynamics, or by learning an autoencoder via minimisation of reconstruction error. We present a concise overview of the mathematics behind these two approaches and conduct a comparative numerical study of these two approaches on illustrative examples.

A multigrid method for kernel functions acting on interacting structures with applications to biofluids

Simulating the dynamics of discretized interacting structures whose relationship is dictated by a kernel function gives rise to a large dense matrix. We propose a multigrid solver for such a matrix that exploits not only its data-sparsity resulting from the decay of the kernel function but also the regularity of the geometry of the structures and the quantities of interest distributed on them. Like the well-known multigrid method for large sparse matrices arising from boundary-value problems, our method requires a smoother for removing high-frequency terms in solution errors, a strategy for coarsening a grid, and a pair of transfer operators for exchanging information between two grids. We develop new techniques for these processes that are tailored to a kernel function acting on discretized interacting structures. They are matrix-free in the sense that there is no need to construct the large dense matrix. Numerical experiments on a variety of bio-inspired microswimmers immersed in a Stokes flow demonstrate the effectiveness and efficiency of the proposed multigrid solver. In the case of free swimmers that must maintain force and torque balance, additional sparse rows and columns need to be appended to the dense matrix above. We develop a matrix-free fast solver for this bordered matrix as well, in which the multigrid method is a key component.

Dynamic analysis of pilot transfer accidents

Marine pilot is the person who expert on a specific region and guide the ship masters for safe navigation. Pilot transfer (PT) operation is a process of embarkation or disembarkation of pilots from pilot boat to ship or viceverca which is very risky operation and accidents even cause death of the pilots sometimes happen. The nature of the operation require pilots transfer between two movement vessel relatively in open sea conditions expose to different weather environment along day and night. Given the dearth of international research on pilot transfer operations, this study seeks to combine fault tree analysis with bayesian network analysis using a fuzzy technique in order to analyze accidents that occur during pilot transfer operations. When first investigating the root causes and causal chain of the PT accidents, fault tree analysis (FTA) was used. The probability of crucial occurrences are often cloudy, but experts' judgment and imprecise ideas can help. A Bayesian network (BN) mapping is made to get around the problems caused by FTA's conditional dependencies and lack of flexibility. Sensitivity analysis is used to help BN simulate the analysis using the entire operating procedure. The study's findings highlighted the root nodes “poor condition of pilot ladder”, “lack of safety culture”, “adverse sea/swell” and “securing failure of pilot ladder on deck” as major contributors to PT accidents. The results show that the study's methodology is sound and practical, and that adding FTA-BN to an analysis of PT accidents will make a substantial contribution to the literature.

Flexible PON systems enabling optical virtual private network and upstream channel upgrade

With the rapid growth of peer-to-peer (P2P) traffic in the access network, the capability to implement inter-optical network unit (ONU) communication (IOC) has become a fundamental requirement for the underlying passive optical network (PON). The conventional IOC is realized electronically on layer 2 or layer 3 and relies on the transfer operations in the optical line terminal (OLT), thus resulting in high transmission latency and excessive bandwidth consumption. To achieve an efficient IOC, the optical virtual private network (OVPN) is proposed to establish direct optical layer links among ONUs by adding some auxiliary optical components to the existing PON system. However, in previously reported OVPN schemes, the added devices are only used for IOC and cannot fulfill other network functions, which leads to poor flexibility. To improve the reconfigurability of the whole PON system, we present two simple modifications that can not only achieve a high-bandwidth OVPN but also increase the upstream channel capacity. The proposed schemes introduce a new wavelength as the OVPN channel to refrain from changing the physical configuration of the normal upstream and downstream. One scheme retrofits the optical line terminal (OLT) with a fiber Bragg grating (FBG) based reflection module, while the other employs an additional short-length distribution fiber for each ONU to redirect IOC traffic. In both schemes, optical switches (OSWs) are used to control the added OVPN wavelength and the original upstream wavelength so that the two wavelengths can transmit IOC traffic and upstream traffic flexibly. According to the states of OSWs, PON systems will form multiple working modes adapted to different network conditions. To evaluate the improvement in flexibility of wavelength usage, the throughput performances of proposed schemes were analyzed theoretically under varying offered loads and IOC traffic proportions. In addition, the feasibility of both schemes was verified through physical layer simulations, where the optical spectra and bit error rates (BERs) of signals on different wavelengths were investigated.

Role of Hundi in Border Trade Payment of Northern Thailand- Myanmar Before and After 2021 Military Coup

Myanmar considers border trade more important than international trade. Due to the economic sanctions imposed by the West since the military government took power in 1996 up until the latest one in 2021, Thailand -Myanmar border trade has been characterized by more informal trade than previously. Border trade has developed despite being subjected to long-standing international trade barriers. This study aims to convey an understanding of how the informal border payment, “Hundi”, works as the border-trade -payment between Myanmar and Northern Thailand. Even though hundi is an informal transfer system it is widely used as an alternative banking system. Especially, hundi is used in the financing of legitimate businesses, to prevent exacerbating the problems of access to credit of different states. This study draws on available literature and open-source reporting, as well as extensive field research by interviewing trusted sources for more than 30 informants (i.e., border-trader, money changer, money transfer operators, business leaders, hundi operators, immigrant labors, government officials, commercial banking staffs) in the northern part of Thailand with the border city in Shan state, Myanmar during 2017-2022. This study found that hundi plays a significant role as both a substitute and complement to cross-border trade and payment across the border of Myanmar-Thailand. After the recent political instability, and expansion from a formal banking sector to a mobile money services, in the short term, we are unlikely to see an elimination of the hundi system completely.

Dynamics of Ostrowski skew-product: 1. Limit laws and Hausdorff dimensions

We present a dynamical study of Ostrowski’s map based on the use of transfer operators. The Ostrowski dynamical system is obtained as a skew-product of the Gauss map (it has the Gauss map as a base and intervals as fibers) and produces expansions of real numbers with respect to an irrational base given by continued fractions. By studying spectral properties of the associated transfer operators, we show that the absolutely continuous invariant measure of the Ostrowski dynamical system has exponential mixing properties. We deduce a central limit theorem for random variables of an arithmetic nature, and motivated by applications in inhomogeneous Diophantine approximation, we also get Bowen–Ruelle type implicit estimates in terms of spectral elements for the Hausdorff dimension of a bounded digit set.

Oil spill in Ilha Grande Bay: analysis of the impact mitigation process

In Brazilian waters, the main oil spills occurred near maritime terminals and oil refineries. In 2015, a leak spilled more than 25,000 liters of oil into the sea, during oil transfer operations between ships at the terminal's mooring pier. This event reached an area of 459 kilometers, between the bays of Ilha Grande and Sepetiba, with oil adhering to several coastal and island points. Impact assessments and mitigating measures were carried out during 3 months of daily technical monitoring in the field. Impact mitigation measures were agreed with the environmental inspection body, and low pressure washes, at room temperature with sea water, of shores with adhered oil, were carried out. Along the impacted area, several coastal points with populations of barnacles covered by oil were recorded, which subsequently showed high mortality rates. The washing of the points that had a large amount of adhered oil proved to be effective in cleaning the shores, and mainly in the release of substrate, for a new repopulation of organisms of the biological communities that occur in these ecosystems.

Civilian Medical Responder Perspectives to a Federal Military Medical Deployment in New York City during the COVID-19 Pandemic

Objectives This study aims to describe the civilian experience and perceptions of the patient coordination and management at the interface of the New York City (NYC) civilian and the military health systems during a large-scale public health emergency. Methods A qualitative study design was implemented with interviews conducted using a basic descriptive approach. Purposive sampling was used to recruit participants with experience working during the first wave of COVID-19 in NYC. Inclusion criteria were civilians who worked at the Javits Center, the USNS Comfort, or NYC hospitals, who interfaced with patient transfer and military personnel during the city-wide medical response to COVID-19. Semi-structured video interviews were conducted between July 20, 2021 and March 11, 2022. Results Civilian responders working in the clinical and transfer operations of patients to military facilities in NYC during March and April of 2020 described initial confusion, as well as logistical (patient selection, transfer logistics, patient tracking), communication, and leadership challenges. While the military deployment was felt to be necessary to address the surge capacity in hospitals, the lack of clarity about military medical resources and frameworks for response resulted in confusion about what was being offered by the military deployment. This was balanced by the positive impression of working with military members and the resources that they brought to the response more generally. The need for future trainings and exercises were highlighted. Conclusions Initial challenges with civilian-military roles and responsibilities, regional needs assessment, patient selection, and logistics were ultimately resolved through adaptation of civilian and military leadership. Improvements in patient tracking, medical records, and standard hospital admission and discharge functions for patients in military alternative care facilities were identified as areas for improvement. Civilian government, health care, and military leaders should consider these ideas when planning for future military deployments in support of a domestic medical response.

Conditional mixing in deterministic chaos

AbstractWhile on the one hand, chaotic dynamical systems can be predicted for all time given exact knowledge of an initial state, they are also in many cases rapidly mixing, meaning that smooth probabilistic information (quantified by measures) on the system’s state has negligible value for predicting the long-term future. However, an understanding of the long-term predictive value of intermediate kinds of probabilistic information is necessary in various physical problems, and largely remains lacking. Of particular interest in data assimilation and linear response theory are the conditional measures of the Sinai–Ruelle–Bowen (SRB) measure on zero sets of general smooth functions of the phase space. In this paper we give rigorous and numerical evidence that such measures generically converge back under the dynamics to the full SRB measures, exponentially quickly. We call this property conditional mixing. While conditional mixing typically cannot be proven from standard transfer operator theory, we will prove that conditional mixing holds in a class of generalized baker’s maps, and demonstrate it numerically in some non-Markovian piecewise hyperbolic maps. Conditional mixing provides a natural limit on the effectiveness of long-term forecasting of chaotic systems via partial observations, and appears key to proving the existence of linear response outside the setting of smooth uniform hyperbolicity.

Тенденции развития сверхширокополосных прямохаотических средств связи

The report discusses the development trends in the development of ultra-wideband wire-less communications based on chaotic signals. For the first time, direct chaotic communications were proposed in 2000 as a way to use noise-like (chaotic) signals for communication systems. The idea was to generate information-carrying signals directly in the region of radio or microwave frequencies where transmission takes place, and to modulate and demodulate these signals there without resorting to frequency transfer operations. In the basic version of the scheme, chaotic radio pulses were used as an information carrier, which made it possible to use “on-off” modulation and modulation of the positions of chaotic radio pulses. An envelope detector matched with the transmitted signal was used as a receiver. Another variant of the direct chaotic system is the recently proposed relative transmission scheme based on chaotic radio pulses. The report examines the characteristics and specifics of both schemes when used in ultra-wideband wire-less communication in the centimeter and decimeter wavelength ranges.