Measured Loss Rate Research Articles

A Coloring-Based Packet Loss Rate Measurement Scheme on Network Nodes

Network measurement is an efficient way to understand network behavior. Traditional measurement techniques focus on internet protocol (IP) networks, where the processing capacity of network nodes is limited and primarily dedicated to packet forwarding. As a result, these techniques typically rely on end hosts or external systems to analyze traffic and evaluate network performance. This reliance introduces several challenges, such as increased measurement latency and scalability limitations, particularly in large-scale networks. With the emergence of next-generation internet architectures, especially information-centric networking (ICN), network nodes have gained enhanced capabilities, enabling measurement tasks to be performed directly at these nodes. This paper proposes a distributed measurement scheme where network nodes collaborate to monitor the packet loss rate on the intermediate link. By setting an unused bit in the packet header, the upstream node “colors” the packets into different color blocks. The minimum duration of each block is determined by the degree of reordering on the link, and the number of packets in each block must be a power of two. The downstream node recognizes blocks, assigns packets to the right block, and deduces the original number of packets for each block to calculate packet loss. Moreover, the upstream node adjusts the number of packets in each block based on the packet transmission rate on the link, aiming to balance measurement accuracy and frequency. A P4-based implementation on a BMv2 software switch is presented to demonstrate the feasibility of the proposed scheme. Simulations show that this scheme improves measurement accuracy and is more robust against packet reordering. Additionally, the proposed scheme maintains relatively low network overhead and, at higher measurement frequencies, exhibits the lowest overhead compared to existing methods.

Investigating the Chemical Stability of Electrospray Plumes During Particle Collisions

Electrospray thrusters fulfill the main propulsion requirements for long-term small-satellite missions. However, the molecules present in the plume are susceptible to collisions, chemical reactions, and fragmentation, which may introduce different new species with various mass-to-charge ratios inside the plume. Prediction of the byproducts that appear upon collisions is of prime importance to predicting the evolution of the plume and estimating the performance and the lifetime expectancy of the thruster. In this work, we use molecular dynamics simulations to investigate monomer–neutral collisions at different impact configurations, impact energies, and impact parameters, and we provide the mass spectra of the resulting species. We predict that 1) collisions within a center-of-mass distance of 6 Å can result in momentum exchange and molecular fragmentation, 2) higher-energy impacts produce more byproducts, and 3) heavy molecules (e.g., 1-ethyl-3-methylimidazolium [EMI] and BF4) are more likely to result from weak collisions (<30 eV), whereas light molecules (e.g., H, F, and CH3) are more likely to result from strong collisions. Collisional fragmentation is shown to negatively affect key performance indicators, including reductions in thrust, specific impulse, and propulsive efficiency. This phenomenon potentially accounts for the observed discrepancies in experimental measurements of current and mass loss rates.

Comparison of two multiplexed portable cold-atom vacuum standards

We compare the vacuum measured by two portable cold-atom vacuum standards (pCAVSs) based on ultracold 7Li atoms. pCAVSs are quantum-based standards that use a priori scattering calculations to convert a measured loss rate of cold atoms from a conservative trap into a background gas pressure. Our pCAVS devices share the same laser system and measure the vacuum concurrently. The two pCAVSs together detected a leak with a rate on the order of 10−6 Pa l/s. After fixing the leak, the pCAVS measured pressure of about 40 nPa with 2.6% uncertainty. The two pCAVSs agree within their uncertainties, even when swapping some of their component parts. Operation of the pCAVS was found to cause some additional outgassing, on the order of 10−8 Pa l/s, which can be mitigated in the future by better thermal management.

Facial skin ageing: Key concepts and overview of processes.

IntroductionThe face is a cosmetically sensitive region where the process of ageing is most clearly manifested. With increased focus on anti‐ageing and longevity, more anti‐senescent treatments are being proposed despite limited evidence. This study outlines the pathways and mechanisms underpinning the biological process of ageing in the face.MethodsComprehensive searches of MEDLINE, EMBASE, Cochrane Library and CINAHL from inception to 2020. Inclusion criteria included all empirical human research studies specific to facial ageing features, written in the English language.ResultsA total of 65 papers met inclusion criteria for analysis. Pathways were subdivided into intrinsic and extrinsic senescence mechanisms. Intrinsic pathways included genetics, generation of reactive oxygen species and hormonal changes. Extrinsic pathways included photoageing and damage to skin layers. The combined intrinsic and extrinsic pathway alterations result in wrinkles, higher laxity, slackness and thinning of the skin. Skin functions such as barrier immune function, wound healing, thermoregulation and sensory function are also impaired.ConclusionThe ageing process is unique to the individual and depends on the interplay between an individual's genetics and external environmental factors. Through understanding the molecular and cellular mechanisms, an appreciation of the consequent structural and functional changes can be achieved. Based on this knowledge, further research can focus on how to slow or impede the ageing process and identify specific targets to develop and evolve new treatment strategies.

Design and implementation of a software tester for benchmarking stateful NATxy gateways: Theory and practice of extending siitperf for stateful tests

Our siitperf is the world’s first RFC 8219 compliant free software SIIT (Stateless IP/ICMP Translation, also called stateless NAT64) benchmarking tool. It was written in C++ using DPDK (Intel Data Plane Development Kit). Our current effort aims to design and implement a test program for stateful NATxy gateways, including both stateful NAT64 and stateful NAT44 (also called NAPT: Network Address and Port Translation). Due to the object-oriented design of siitperf, it is feasible to extend it for stateful tests, while keeping its original design and features. In this paper, we introduce the problem of benchmarking stateful NATxy gateways and propose various solutions. We disclose the design and the most important implementation decisions of the stateful extension of siitperf. We prove the viability of our design and implementation by a functional NAT64 test and performing the maximum connection establishment rate, throughput, and frame loss rate measurements of the Jool stateful NAT64 implementation. We also carry out an initial performance estimation of the stateful extension of siitperf. Our tester is distributed as free software under the GPLv3 license for the benefit of the research, benchmarking and networking communities.

Vacuum pressure measurement based on &lt;sup&gt;6&lt;/sup&gt;Li cold atoms in a magneto-optical trap

Ultra-high vacuum measurement and extremely high vacuum (UHV/XHV) measurement play an important role in high-tech fields such as deep space exploration, particle accelerators, and nanoscience; with the continuous extension of the lower limit of measurement, especially when it reaches the order of 10&lt;sup&gt;–10&lt;/sup&gt; Pa, higher requirements are placed on the accuracy of the measurement. At present, in the field of UHV/XHV measurement, ionization gauges based on the principle of neutral gas ionization are commonly applied to the vacuum measurement. However, traditional ionization vacuum gauges during use can create electronic excitation desorption effects, soft X-rays, and the effect of hot cathode outgassing, thereby affecting the accuracy of measurement and limiting the lower limit of measurement. Compared with the traditional measurement technology, this method uses the relationship between the loss rate and pressure caused by the collision of cold atoms trapped in the trap depth with the background gas to calculate the gas density and inversely calculate the vacuum pressure. Based on the intrinsic quantum mechanical properties of cold atom collisions, this method is expected to be developed into a new vacuum traceability standard. In this paper, based on the small-angle approximation and impulse approximation under the quantum scattering theory, the loss rate coefficient of the collision of &lt;sup&gt;6&lt;/sup&gt;Li cold atoms with background gas molecules is calculated. According to the ideal gas equation, the pressure inversion formula is obtained. The collision loss rate is extracted by accurately fitting the loss curve of the cold atom. In order to improve the accuracy of vacuum inversion and reduce the influence of quantum diffractive collision on loss rate measurement, the trap depth under the conditions of a certain cooling laser intensity, detuning, and magnetic field gradient is determined by the photoassociation method. Finally, in a range of 1 × 10&lt;sup&gt;–8&lt;/sup&gt;–5 × 10&lt;sup&gt;–6&lt;/sup&gt; Pa, the inverted pressure value is compared with the measured value of the ionization meter, proving that this method has good accuracy and reliability in the inversion of vacuum pressure. At present, the main factor restricting the improvement of accuracy is the influence of the collision between the excited atoms in the magneto-optical trap and the background gas on the loss rate measurement. In the future, with the proportion of excited atoms and the excited state &lt;i&gt;C&lt;/i&gt;&lt;sub&gt;6&lt;/sub&gt; coefficient to be precisely determined, the uncertainty of vacuum pressure measurement can be further reduced.

Reliability of methods to determine cutaneous evaporative water loss rate in furred and fleeced mammals.

We used a high-precision weighing system and flow-through respirometry to quantify cutaneous evaporative water loss rates in woolly sheep (wool thickness, ca. 6.5 cm) and haired goats (coat thickness, ca. 2.5 cm), while simultaneously recording parallel data obtained from (1) a flow-through ventilated capsule, (2) a closed hand-held electronic evaporimeter chamber, and (3) a closed colorimetric paper disc chamber. In comparison to the weighing system and respirometry, used here as a "gold standard" measure of cutaneous evaporative water loss rate, we found relatively good agreement with data obtained from the flow-through ventilated capsules. However, we found poor agreement with data obtained from the closed electronic evaporimeter chambers (underestimated by 60%, on average) and the closed colorimetric paper disc chambers (overestimated by 52%, on average). This deviation was likely associated with a requirement for shaved skin in the closed chamber methods. Our results therefore cast doubt on the validity of the closed chamber methods for measurement of cutaneous evaporative water loss rates in furred and fleeced mammals, and instead show that more accurate values can be obtained using flow-through ventilated capsules.

Molecule–molecule and atom–molecule collisions with ultracold RbCs molecules

Understanding ultracold collisions involving molecules is of fundamental importance for current experiments, where inelastic collisions typically limit the lifetime of molecular ensembles in optical traps. Here we present a broad study of optically trapped ultracold RbCs molecules in collisions with one another, in reactive collisions with Rb atoms, and in nonreactive collisions with Cs atoms. For experiments with RbCs alone, we show that by modulating the intensity of the optical trap, such that the molecules spend 75% of each modulation cycle in the dark, we partially suppress collisional loss of the molecules. This is evidence for optical excitation of molecule pairs mediated via sticky collisions. We find that the suppression is less effective for molecules not prepared in the spin-stretched hyperfine ground state. This may be due either to longer lifetimes for complexes in the dark or to laser-free decay pathways. For atom–molecule mixtures, RbCs + Rb and RbCs + Cs, we demonstrate that the rate of collisional loss of molecules scales linearly with the density of atoms. This indicates that, in both cases, the loss of molecules is rate-limited by two-body atom–molecule processes. For both mixtures, we measure loss rates that are below the thermally averaged universal limit.

Understanding one-body losses in magnetically trapped metastable europium atoms

We report the measurement of one-body loss rates for magnetically trapped metastable europium atoms and the study of their loss mechanism. The loss of atoms observed in a magneto-optical trap is not fully understood because of the indivisibility of the loss regarding optical pumpings due to the presence of cooling laser beams. We magnetically trapped the atoms by directly loading from the magneto-optical trap and observed almost identical one-body loss rates of approximately 2.6s−1 for two isotopes: 151Eu and 153Eu. Our rate-equation-based model, combined with loss rate measurements carried out with repumpers, shows that blackbody radiation at room temperature drives E1 transitions and induces the observed losses.

Full-Dimensional Global Potential Energy Surface for the KRb + KRb → K2Rb2* → K2 + Rb2 Reaction with Accurate Long-Range Interactions and Quantum Statistical Calculation of the Product State Distribution under Ultracold Conditions

A full-dimensional global potential energy surface (PES) for the KRb + KRb → K2Rb2* → K2 + Rb2 reaction is reported based on high-level ab initio calculations. The short-range part of the PES is fit with the permutationally invariant polynomial-neural network method, while the long-range parts of the PES in both the reactant and product asymptotes are represented by an asymptotically correct form. The long- and short-range parts are connected with intermediate-range parts to make them smooth. Within a statistical quantum model, this PES reproduces both the measured loss rates of ultracold KRb molecules and the K2 and Rb2 product state distributions, underscoring the important role of tunneling in ultracold chemistry. The PES also correctly predicts the lifetime of the K2Rb2* intermediate complex within the Rice-Ramsperger-Kassel-Marcus limit. It thus provides a reliable platform for future dynamical studies of the prototypical reaction.

Soiling Loss Rate Measurements of Photovoltaic Modules in a Hot and Humid Desert Environment

Abstract Power generation from renewable energy sources, in particular solar photovoltaics (PV), has become extremely attractive thanks to its very low levelized cost of electricity (LCoE). In desert-like environments, the energy yield is drastically reduced due to dust accumulation. While effective and affordable cleaning strategies can be implemented in large, MW-size PV power plants, soiling remains an economic and logistic challenge. In this article, we analyze the soiling loss rates of PV modules for different tilt angles measured during a period of 15 months in the Western Region of Saudi Arabia. We observe a strong correlation between weather parameters like humidity and wind speed and the mechanism of dust accumulation. Our measurements show that, for specific weather conditions, soiled modules undergo a partial cleaning process. As a consequence, and for the first time, the soiling loss rates are shown to have a clear dependence on the current soiling state of the modules, with clean modules soiling twice as fast as soiled ones. This dependency is a key for predicting the correct cleaning frequency of a PV power plant. Finally, the results obtained for vertically mounted modules (90 deg), where dust accumulation is negligible, point to a favorable case for the use of bifacial PV modules.

The corrosion behavior of Mg–Nd binary alloys in the harsh marine environment

Abstract The corrosion behavior of Mg-Nd binary alloys in the harsh South China Sea environment was researched by scanning electron microscopy, energy-dispersive spectrometry and X-ray diffraction analysis. In order to explain the corrosion mechanism, corrosion resistance was analyzed by weight loss rate and electrochemical measurement in the laboratory. With a continuous enlargement of Nd-content, Mg12Nd phases increased and multiplied. The weight loss rate of Mg-0.5Nd alloy was 0.0436 mg•cm−2•y−1 (0.0837 mm•y−1), whereas that of Mg-1.5Nd alloy was 0.0294 mg•cm−2•y−1 (0.0517 mm•y−1) during the exposure corrosion in the South China Sea site. The mechanical strength of Mg-1.5Nd alloy was 148 MPa before the exposure in the harsh marine environment, while the residual mechanical strength was merely about 94 MPa after the exposure test. Both Mg-1.5Nd alloy and Mg-1.0Nd alloy occurred the brittle fracture, which resulted that the elongation was nearly equal to zero. The self-corrosion current density demonstrated that degradation rate of Mg-Nd binary alloys was as follows : Mg-0.5Nd>Mg-1.0Nd>Mg-1.5Nd. For the South China Sea corrosion site, a large amount of sea salts exited in the atmospheric environment. Due to the heavy rainfall and high humidity, sodium chloride in the atmospheric environment dissolved, more serious electrochemical corrosion occurred on the surface of Mg-Nd binary alloys.

Pickling behavior of 2205 duplex stainless steel hot-rolled strips in mixed solutions of HNO3-HF

The pickling behaviour of 2205 DSS hot-rolled strips after annealing and sand blasting was studied in the mixed solutions of HNO3-HF using weight loss rate, surface analysis, corrosion potential, and electrochemical impedance spectroscopy measurements. The pickling rate decreased as the concentration of HNO3 increased in the mixed solutions of x HNO3 + 25 g l−1 HF (x = 40 ∼ 200 g l−1) at 50 °C due to passivation. The passivating effect of HNO3 became weak as its concentration was less than 80 g l−1. The pickling rate increased noticeably when the concentration of HF in the mixed solutions of 120 g l−1 HNO3 + y HF (y = 5 ∼ 80 g l−1) at 50 °C was increased. The dissolution of the metal under the oxide scale may have changed from the passive state to the active state as the HF concentration was higher than 25 g l−1. The pickling dissolution accelerated noticeably as the temperature rose from 40 to 60 °C. With the optimised pickling process, 2205 DSS hot-rolled strips can be pickled industrially with good efficiency and surface topography.

The water vapor foreign-continuum in the 1.6 µm window by CRDS at room temperature

Water vapour foreign-continuum absorption cross-sections, CF, are measured for the first time at room temperature in the 1.6 µm transparency window, of importance for atmospheric applications. The measurements are performed by cavity ring down spectroscopy (CRDS) at 15 selected spectral data points. These data, covering the 5700–6640 cm−1 spectral range, are derived from the variation of the absorption signal during pressure ramps of humidified air up to 1 atm with a typical 1% water vapour relative concentration. The foreign-continuum absorption was obtained as the excess of the measured loss rate compared to the sum of the loss rate measured with dry air, the local water monomer contribution and the self-continuum absorption. CF values were derived from the linear dependence of the foreign-continuum absorption with the product of the partial pressures of water vapour and air. The semi-empirical MT_CKD CF values are found significantly underestimated in the centre of the window.

Assessment of Soil Erosion with RUSLE 3D and USPED in the Nekor Watershed (Northern Morocco)

Over the last decades, estimation of soil erosion using empirical models has long been an active research topic, especially because they are useful to establish watershed management plans. Nevertheless, their application over large areas in a data-scarce Mediterranean region is still a challenge given the furrowed and steep nature of landscapes as well as the aggressiveness of the semi-arid climate. The main purpose of this research was to identify the spatial patterns of erosion and deposition in Nekor river basin (Northern Morocco) using two models: the Revised Universal Soil Loss Equation for Complex Terrain (RUSLE3D) and the Unit Stream Power-based Erosion Deposition (USPED). The two models were evaluated using existing annual soil loss rate measurements. As a result of the RUSLE3D application, about the 73% of the Nekor basin ranges between moderate and extreme risks of erosion, while according to USPED estimation, only 50% of the basin ranges between moderate and extreme risks of erosion. The analysis shows that the mean annual soil erosion rate for both models ranges between 60 and 65 t⋅ha−1⋅year−1 while the mean annual deposition rate is 38 t⋅ha−1⋅year−1. The current results confirmed those coming from previous soil erosion studies, which estimated annual soil loss rates in Nekor river basin between 50 and 70 t⋅ha−1⋅year−1. This study also provided valuable guidance on where to implement soil protection measures.

Application-Level Packet Loss Rate Measurement Based on Improved L-Rex Model

The current network information asymmetry is infringing the interests of end users in non-neutral network environment. To empower users, application-level performance measurements are usually used to rebalance the information asymmetry currently disfavoring users. Application-level packet loss rate, as an important key performance indicator (KPI), receives extensive attention in academia. However, every coin has its two sides. Although the application-level packet loss estimation is simple and nonintrusive, since the information available from the application layer is relatively scarce compared to the lower layers, the estimation accuracy has no guarantee. In view of this, taking the L-Rex model as the cut-in spot, this paper focuses on leveraging the self-clocking mechanism of Transmission Control Protocol (TCP) to improve the accuracy of application-level loss estimation. Meanwhile, owing to the dynamically estimated parameters and the weakened packet reordering impact, the robustness of estimation is also expected to be improved accordingly. Finally, a series of comparative experiments at the practically relevant parameter space show that the enhanced approach and strategy detailed in this paper are effective.

Implications of Recent Stellar Wind Measurements

Very recent measurements of stellar winds are used to update relations between winds and coronal activity. New wind constraints include an upper limit of Ṁ < 0.1 Ṁ⊙ for τ Ceti (G8 V), derived from a nondetection of astrospheric H I Lyman-α absorption. This upper limit is reported here for the first time, and represents the weakest wind constrained using the astrospheric absorption technique. A high mass loss rate measurement of Ṁ = 10 Ṁ⊙ for δ Pav (G8 IV) from astrospheric Lyman-α absorption suggests stronger winds for subgiants than for main sequence stars of equivalent activity. A very low mass-loss rate of Ṁ ≈ 0.06 Ṁ⊙ recently estimated for GJ 436 (M3 V) from Lyman-α absorption from an evaporating exoplanetary atmosphere implies inactive M dwarfs may have weak winds compared with GK dwarfs of similar activity.

Determination of Cyclability of Li/FeS2 Batteries Based on Measurement of Coulombic Efficiency

The electrochemical performance of negative electrodes based on different FeS2 samples was investigated. The study demonstrated a correlation between the coulombic efficiency obtained over 60 cycles and the capacity loss rate evaluated over 15 cycles. The accuracy of the coulombic efficiency and capacity loss rate measurements was advantageous for predicting the aging behavior of half-cells over a short-term test. A suggested classification of the coulombic efficiency and verification via a numerical analysis were proposed to determine the fading rate of batteries during the galvanostatic test.

Solid Particle Erosion Behavior of Carbon Fiber - Metal Wire Hybrid Reinforced Polymer Composites

Carbon fiber reinforced composite materials (CFRP) are being widely used in aircraft parts and unmanned air vehicle (UAV) airframe production due to their high specific stiffness and strength. Besides their superior characteristics, they have a disadvantage of poor electrical conductivity when used in UAV airframes which subjected to lightning strike during their service life. In order to protect UAV airframe from lightning strike damage, adding a metal wire to CFRP composite is an alternative method. Moreover, UAV and aircraft airframe materials subjected to solid particle erosion damage during their service life also.Surface damage induced by solid particle erosion cause aerodynamic losses and result with increase in specific fuel consumption or shortening of maximum air vehicle range. Also worn body could be lost its lightning strike residence. It is evident that there is no much literature study about CFRP - metal wire hybrid reinforced composites solid particle erosion behavior. The aim of this study is to characterize the solid particle erosion behavior of CFRP - metal wire hybrid reinforced composite and analyze the post wear damage induced in the surface of the samples. Solid particle tests were performed according to ASTM G 76 standard in a specially designed test rig.Mass loss and erosion rate measurements after tests were done and damage mechanisms were discussed. Surface roughness analysis of specimens before and after solid particle erosion tests were performed by using 3D non-contact laser profilometer.

Development of a new UHV/XHV pressure standard (cold atom vacuum standard)

The National Institute of Standards and Technology has recently begun a program to develop a primary pressure standard that is based on ultra-cold atoms, covering a pressure range of 1 × 10−6 Pa–1 × 10−10 Pa and possibly lower. These pressures correspond to the entire ultra-high vacuum range and extend into the extreme-high vacuum. This cold-atom vacuum standard (CAVS) is both a primary standard and absolute sensor of vacuum. The CAVS is based on the loss of cold, sensor atoms (such as the alkali-metal lithium) from a magnetic trap due to collisions with the background gas (primarily H2) in the vacuum. The pressure is determined from a thermally-averaged collision cross section, which is a fundamental atomic property, and the measured loss rate. The CAVS is primary because it will use collision cross sections determined from ab initio calculations for the Li + H2 system. Primary traceability is transferred to other systems of interest using sensitivity coefficients.