Loss Distribution Research Articles

Physiological Roles of Eumelanin- and Melanogenesis-Associated Diseases: A Look at the Potentialities of Engineered and Microbial Eumelanin in Clinical Practice.

This paper aims to highlight the physiological actions exerted by eumelanin present in several organs/tissues of the human body and to rationalise the often conflicting functional roles played by this biopolymer on the basis of its peculiar properties. Besides pigmentary disorders, a growing number of organ injuries and degenerative pathologies are presently ascribed to the modification of physiological eumelanin levels in terms of alterations in its chemical/structural features, and of a partial loss or uneven distribution of the pigment. The present review analyses the more recent research dedicated to the physiological and pathological actions of eumelanin and provides an insight into some melanogenesis-associated diseases of the skin, eye, ear, and brain, including the most significant neurodegenerative disorders. Also described are the potentialities of therapies based on the localised supply of exogeneous EU and the opportunities that EU produced via synthetic biology offers in order to redesign therapeutical and diagnostic applications.

Properties and applications of the Tan Weibull loss distribution

Probability models play crucial role in modeling loss in the finance and actuarial sciences. In this article, a new family of loss distributions known as the Tan F-Loss family of distributions is proposed with the Tan Weibull Loss distribution as a special case. The density exhibits decreasing, right skewed, symmetric, and approximately symmetric shapes. The hazard rate function shows decreasing and modified bathtub shapes. The statistical properties of the Tan Weibull Loss distribution including the quantile function, moments, expansion of the general rate, moment generating function, incomplete moment, and order statistics are studied. The maximum likelihood estimators of the distribution are also studied. Simulations are carried out to examine the behavior of the estimators. The results show that the estimators are consistent. The usefulness of the proposed distribution is demonstrated with two insurance loss datasets. The results show that the proposed distribution gives a better parametric to the two datasets compared with the competing distributions.

An analytical approach for designing sCO2 centrifugal compressors using the loss-integrated throughflow method

Several studies have focused on the analytical modeling of centrifugal compressors. These models are commonly used in design, optimization and evaluation of rotor geometry. Existing models, which rely on either the meanline method (1D model) or the streamline curvature-based throughflow method (2D model) combined with semi-empirical pressure loss relations, are closed-loop models that do not account for pressure loss distribution along the blade channel. Additionally, these models simplify the rotor’s three-dimensional geometry, focusing primarily on the β angle and meanline length. To address these limitations, we introduce an open-loop analytical approach called the ’loss-integrated throughflow method’ (LITM). This method computes pressure losses step-by-step along the blade’s channel geometry using the three-dimensional cross-section of the rotor as input data. The motivation behind this new approach is to develop an alternative tool for the preliminary design of supercritical CO2 (sCO2) compressors, providing insight into the relation between losses and rotor geometry beyond just the β angle and meanline length. In the present work we compare simulation results with a one-dimensional (1D) mathematical model that has been validated against experimental data for sCO2. We compare three sets of rotors, where each set shares identical β angles and meanline lengths. When compared against the 1D model, our model yields deviations ranging from 2.8% to 21.9% for rotors with matching meanline lengths and β angles. This suggests that factors other than the variables previously considered influence pressure losses. As a result of this study, we conclude that the proposed analytical model offers potential to refine the preliminary design for sCO2 rotors.

Study on Thermal Characteristics of Winding under Inter-Turn Fault of Oil-Immersed Transformer

The inter-turn fault is a common fault of oil-immersed transformers. Due to the deterioration of inter-turn insulation, its resistance decreases, which leads to an increase in the winding coil current and loss, causing the winding temperature to rise. Therefore, analyzing the electrothermal characteristics of inter-turn short circuit faults in oil-immersed transformers can provide a theoretical basis for the diagnosis of inter-turn faults in transformers. This paper studies the equivalent circuit under inter-turn faults and establishes a field–circuit coupling model to calculate the current characteristics under different inter-turn short circuit faults of transformers. The distribution of coil losses under faults is calculated as thermal source excitations, and a thermal–fluid-coupled calculation model for oil-immersed transformers is established. After the experimental verification, it is found that both the errors between the winding and tank surface temperatures do not exceed the acceptable limits, validating the effectiveness of this model. Using this model to calculate the temperature distribution for various inter-turn short circuit faults in transformers reveals their hot-spot characteristics. The results indicate that under inter-turn fault conditions, the temperature at faulty turns will gradually increase towards a limit, eventually leading to coil damage. This research provides theoretical support for enhancing transformer detection and diagnostic capabilities.

Exploring the collision, acoustic and thermal energy dissipation distribution of discrete mass

This research delves into the transfer and loss of energy in a discrete mass when subjected to forced vibration. Using discrete element method (DEM), we analyzed the dynamic behavior of regular spherical granular assemblies and the energy distribution characteristics under different excitation frequencies and reduced accelerations. Moreover, the energy transfer and dissipation process of granular assemblies under different vibration states are studied using an experimental method. The results show that the granular assemblies will produce collision energy dissipation, thermal energy dissipation, acoustic energy dissipation and other forms of energy dissipation in the forced vibration state and the proportion of different energy dissipation under different excitation is given. The collision and friction of granular assemblies are the key to affecting other forms of energy dissipation. When the excitation increases, the energy dissipation forms are generated inside the granular assemblies, and the proportion of collision energy dissipation of the granular assemblies increases. The acoustic energy above 20 kHz occupies the main part of the acoustic energy dissipation. Thermal energy consumption always exists, which takes a long time to play a role. The granular also have other forms of energy loss, which is hard to be measured, including Rayleigh waves generated by granular collision. In this study, the relationship between the forced vibration state of the granular assemblies and the energy loss distribution is established. Various types of energy transfer and conversion distribution which further enriches the energy dissipation of discrete element calculation of the granular assemblies is discussed and provides a reference for the energy loss analysis of the granular assemblies.

The forest loss within small reservoirs surpasses that of large reservoirs across the tropics

The vast potential of hydropower remains crucial in addressing the escalating need for clean energy, particularly in Tropical Moist Forests (TMFs) regions. Yet, the widespread construction of reservoirs within TMFs has resulted in the inundation of forested areas, exacerbating the fragmentation of forest landscapes and contributing additional loss of carbon stored in these ecosystems. Despite this, the scale and degree of forest loss within reservoirs due to inundation from reservoir construction remain poorly quantified and mapped across tropical regions. Here, we leverage long-term TMFs data spanning from 1990 to 2021 to investigate forest loss within reservoirs across tropical regions. We reveal that forest losses within reservoirs total 3521 km2, constituting a relatively small fraction of total forest loss. Nonetheless, the spatial distribution of forest loss within reservoirs varies significantly across the tropics, with patchy distributions observed in the American and African TMFs, and striped patterns evident in the Asian TMFs. Contrary to common assumptions, we show that small reservoirs exhibit higher levels of forest loss compared to large reservoirs, particularly pronounced in the African TMFs region. Furthermore, our projections indicate that the exclusive construction of small reservoirs contributes to approximately 27% of Africa’s total forest area lost. We underscore the importance of policymakers carefully evaluating the trade-offs associated with the construction of large versus small reservoirs in TMF regions, to minimize the adverse impacts of hydropower development on forest ecosystems.

Deductibles and health care utilization: An experiment on the role of forward-looking behavior

We investigate the effects of nonlinear deductible contracts on health utilization behavior by using a laboratory experiment in which we can control the likelihood of hitting the deductible. We also evaluate the effect of subjects receiving regular information updates on their remaining deductible. Our results show that varying the future price has a significant effect on health care consumption. At an individual level, we identify and richly characterize heterogeneity. We find fully forward-looking, fully myopic, as well as mixed types after controlling for risk preferences. We show that there is a substantial welfare loss due to a lack in forward-looking behavior. The distribution of the welfare loss are characterized and differ sharply according to the model of risk preferences adopted for normative evaluation. Potential drivers of welfare effects are investigated and have a tendency to differ across risk preference models.

Brillouin-based fiber loss measurement for PON using ERA-BOTDA with differential width pairs of frequency-swept pump pulses.

We demonstrate Brillouin-based loss distribution measurement for passive optical networks with differential width pairs of frequency-swept pump pulses that can suppress the spatial resolution degradation, especially those created by large loss events typical of an 8-branch splitter. Based on the acoustic wave simulation of a frequency-swept pump pulse, we investigate the arrangement of the modulation frequency within the optical pulse. A preliminary experiment is conducted on a 5-dB loss event near an 8-branch splitter. The results show that the proposed technique can accurately measure loss events with a spatial resolution of better than 3 m.

Defining Design Parameters for Controlled Rocking Braced Frames to Control Seismic Losses

ABSTRACT Controlled rocking braced frames (CRBFs) are a self-centering lateral force-resisting system aimed at reducing structural damage potential. Previous research has shown that relatively low design forces for rocking and for structural elements in CRBFs would be acceptable based on collapse fragility analysis. However, past studies have also highlighted the potential for significant story drifts and for increased demands on acceleration-sensitive nonstructural components installed in buildings with CRBFs. Therefore, while CRBFs have demonstrated acceptable performance in terms of collapse across a wide range of design options, these design options must be evaluated considering the performance of nonstructural components if the intended low-damage potential of CRBFs is to be fully realized. To address this need, this paper investigates the influence of two key design parameters on seismic losses of buildings with CRBFs, namely the response modification factor (R) for the rocking joint design and the amplification factor (γ) used to incorporate higher-mode forces into the capacity design of frame members. Three different heights of CRBF buildings are designed using different design options, with values of R ranging from 5 to 12 and with higher-mode forces considered based on two seismic intensity levels: the design earthquake (DE) and the maximum considered earthquake (MCE). Then, following an assessment of structural responses, the paper’s primary emphasis is on earthquake-induced economic losses. While the computed total expected annual losses (EALs) using various design options are remarkably similar, the distribution of losses attributed to collapse or to nonstructural components varies. The CRBFs with lower resistance to rocking exhibit greater losses attributed to collapse and to drift-sensitive nonstructural components, but this is counterbalanced by a simultaneous reduction in losses related to acceleration-sensitive nonstructural components. Furthermore, in taller CRBF buildings, using amplified higher-mode forces based on the MCE level slightly decreases total EALs compared to those using the DE level, primarily due to a reduction in collapse losses.

Downflow and upflow sand filtration for removing turbid particles with diverse morphological and surface-charge characteristics: Comparisons of filtered water quality and head loss distribution

Besides the physicochemical characteristics (e.g., size, structure, charge nature, etc.) of turbid particles, the filtration flow direction may affect their migration and adhesion behaviors inside the filtration unit. Unfortunately, there has been a lack of research regarding the combined effects of these above factors on filtered water quality and head loss development during filtration. In this study, different turbid particles were prepared by flocculating water samples containing kaolin and humic acid. Filtration experimental results of these flocculated waters revealed that downflow and upflow filtration modes had different durations of effective filtration under identical PAC-dosage cases, and upflow filtration led to faster increases in filtered water turbidity at the breakthrough stage compared to downflow filtration. During 180-min downflow filtration, the average size of residual turbid particles increased, but this did not occur in upflow filtration. Furthermore, differently from downflow filtration, upflow filtration had a more uniform distribution of head loss across all filter layers. The ease of backwashing differed between the two filtration modes, reflected by the different times required for reaching a relatively stable turbidity during 10-min backwashing. Lastly, based on SEM, FTIR and XPS analyses for characterizing the coagulated particle surface morphology, element composition, and functional groups, a series of conceptual models for particle removal by downflow and upflow filtrations were developed to clarify the influencing mechanisms of different turbid particles on filtration. It highlighted the advantages of upflow filtration, including improved distribution of flow resistance, better removal of larger-sized turbid particles, and enhanced pollutant-holding capacity of the filter media.

Statistical characterization of the effect of random core loss on the intercore crosstalk in long-haul uncoupled multicore fiber links.

We characterize the statistical properties of direct average intercore crosstalk (ICXT) in long-haul uncoupled multicore fiber (MCF) links consisting of concatenated MCF segments, where core dependent loss (CDL) in each segment varies randomly. Numerical simulation results show that the direct average ICXT power at the output of long-haul MCF links with random CDL is well described by a Gaussian distribution. A statistical distribution, which accounts for only two values of core loss (the highest and lowest core loss) with equal probability, is proposed as the worst-case distribution of core loss resulting in the maximum excess of direct average ICXT power. With this distribution, practical values of random CDL, 20 MCF segments per span and 2000 km-long links, analytical and simulation results show the maximum excess of direct average ICXT power does not exceed 0.25 dB, being further lower for a higher number of segments. An analytical approximation for the maximum excess of direct average ICXT power in long-haul uncoupled MCF links with similar spans is presented. Demonstrating high accuracy (with less than 0.02 dB discrepancy relative to simulation results in all cases evaluated), this approximation provides a simple and efficient means for estimating the worst-case impact of random CDL on ICXT power in long-haul MCF links.

A processable high thermal conductivity epoxy composites with multi-scale particles for high-frequency electrical insulation

The solid-state transformer (SST) in the renewable energy grid is developing in the way of high voltage and high frequency, which often results in a sharp increase in heat production of the equipment and accelerates the failure of the insulating materials. Epoxy resin (EPR) is commonly used as an insulation material for SST due to its excellent electrical insulating properties, processing performance (viscosity), and low price. However, the thermal conductivity of EPR is only about 0.2 W/(m·K), which leads to poor insulating performance under high frequency and temperature. To enhance thermal conductivity, a substantial quantity of highly thermally conductive particles is incorporated into the EPR, accompanied by a severe increase in electrical insulation defects and viscosity. This study utilized a multi-scale particle-filled approach to investigate the thermal conductivity, processing characteristics, and high-frequency electrical insulation performance of composites. The composite, filled with 25 µm BN and 5 µm SiO2 particles, enhances thermal conductivity to 0.732 W/(m·K) and demonstrates superior electrical insulating properties at both 10 kHz and 20 kHz bipolar square waves (with an increase of 131.76% and 163.97% in relative EPR, respectively), as well as good processability. Meanwhile, it is found that the dielectric loss, thermal conductivity, and electric field distribution of the composite are the main factors affecting the electrical insulating properties from 10 to 20 kHz under high voltage.Graphical

Rate of polyethylene wear correlates with earlier glenoid implant failure in anatomic total shoulder arthroplasty with cemented all-polyethylene glenoid components

BackgroundGlenoid component loosening is the most common cause of anatomic total shoulder arthroplasty failure, and osteolysis is a common intraoperative and radiographic finding associated with these failed arthroplasties. While preclinical testing can estimate failure mode and wear rates in the laboratory, there is limited in vivo data measuring polyethylene wear rate and location. MethodsUsing an institutional review board–approved total joint arthroplasty retrieval collection, 56 cemented all-polyethylene glenoid components from eleven different manufacturers were analyzed for in vivo dimensional change. We used the differential thickness measurement between the anteroposterior and superoinferior axes of each radially symmetrical implant to determine the dimensional change along that axis. A physiologic wear vector was determined for each retrieved device. ResultsThe implants had a median dimensional change of 0.13 mm/year (range 0.01-1.01mm/year) and the 25th and 75th percentiles were 0.060 and 0.22 mm/year, respectively. The average time to revision of devices with <0.1mm/year of wear was 140.9 months, while the averages for devices between 0.1-0.2mm/year and ≥0.2mm/year were 80.7 and 54.0 months, respectively. Devices with ≥0.2mm/year of wear had significantly shorter time to revision than those with <0.1mm/year (P = .0006). The devices had a similar material loss distribution in both superior-inferior and anterior-posterior directions, with 29 (52%) devices having a greater material loss in the superior-inferior distribution and the remaining 27 (48%) devices in the anterior-posterior axis. The physiologic wear vector had a mean of 47.3 degrees, with a relatively even distribution across all angles, suggesting that glenoid component loosening can occur along multiple axes. ConclusionWe conclude that polyethylene wear is a contributing factor for early failure of cemented all-polyethylene glenoid implants and that anatomic total shoulder arthroplasty may benefit from advances in polyethylene processing. We also suggest that in vitro testing of new polymers and designs should incorporate motion vectors beyond the traditional IS rocking horse test.

A parametric approach to flow loss with incidence and tip clearance variables for a compressor linear cascade

A study was conducted using theoretical and numerical calculations to analyze the flow losses of a compressor linear cascade called SMU37-RL02. Its main goal is to determine the parametric expressions for vortex structure weight loss at the 103% axial chord position on the quasi-S3 section of the cascade. A flow loss distribution band delineation extraction method is proposed to improve data acquisition efficiency. The method expands the database by single-parameter variable expressions, and the simulated annealing algorithm solves the full-condition optimized tip clearance range for the cascade. The results show that the dominant flow loss weight of the vortex structures is transferred from the passage vortex to the tip leakage vortex following the increased tip clearance. Making the tip clearance Ct = 0.19%H as the optimization objective has the most stable and best performance at the full incoming flow conditions compared to the cascade with an equidistant tip clearance. The maximum loss reduction is 13.16% relative to the original cascade loss at the i = +1.9° incoming flow condition. The optimal cascade achieves relatively stable optimization over the full range of incoming flow conditions.

Simulation of a scintillator-based fast ion loss detector for steady-state operation in Wendelstein 7-X (invited).

A quantitative theoretical framework has been created to model neutral beam injection and fast ion losses in the Wendelstein 7-X (W7-X) stellarator, including a novel method to develop synthetic diagnostics for fast ion loss detectors (FILDs) of many types, such as scintillating and Faraday Cup FILDs. This is the first time that this has been done in stellarator geometry with this level of fidelity, providing a way for fast ion losses to be predicted more precisely in future stellarator experiments and in W7-X. Simulations of the signal seen by a Faraday Cup FILD have been completed for multiple W7-X plasmas and show close agreement with the measured signals. This method is now applied to an actively water-cooled, scintillator-based FILD, which is currently in development to measure the fast ion loss distribution in W7-X in greater detail. The design makes use of a double slit to measure energy-and-pitch-angle-resolved losses of both co-going and counter-going fast ions. The diagnostic, which can be inserted to different radial positions, has been designed to withstand steady-state heat fluxes of up to 120 kW/m2 along with additional transient heat loads of 100 kW/m2 lasting for up to 20s at a time. Simulations of W7-X standard magnetic configuration show up to 8 × 1013 (s-1 cm-2) ion fluxes onto the sensor from each neutral beam source and no signal from the counter-going slit. These simulations will help inform experimental proposals for future W7-X campaigns after installation of this diagnostic.

Decomposition of green manure and nutrients release in Subarctic, Kola Peninsula, Russia

In the field experiment, the intensity of decomposition and release of nutrients was studied for six types of plant residues – leaves, panicles and straw of oats (Avena sativa), as well as whole plants of lupine (Lupinus angustifolius), phacelia (Phacelia tanacetifolia) and vetch (Vicia sativa) in the arable horizon of Anthrosols on the Kola Peninsula. Samples in mesh nylon bags were sampled after 8, 12 and 24 months of exposure in soil. The loss of weight, the content of Corg and Norg, as well as ash elements – Si, Al, Fe, K, Ca, Mg, P, S and Mn were determined in all plant residue samples. As the results showed, despite the low temperatures, the decomposition of green manure in soil occurred with a high intensity, comparable to the southern chernozem zone: after a year of exposure in the soil, plant residues lost from 47% (oat straw) to 75% (lupine) of their initial ash-free weight. After 2 years, weight loss reached 68% in oat straw and 90% in lupine. The distribution of losses of Corg, Norg, and P between the types of plant residues and decomposition periods correlated significantly (at p≤0.01) with the distribution of weight losses. Changes in the content of other ash elements did not depend on weight loss: depending on the type of material and the stage of decomposition, the samples could not only lose them (K – by all plant residues; Mn – by lupine; S, Ca and Mg – by all plant residues, except straw and oat panicles), but also accumulate them in quantities exceeding the initial ones (Fe – by all species, Mn – by all species except lupine; Ca and Mg – by straw and oat panicles) at certain periods. The accumulation of elements above initial level means that the transformed plant residues can accumulate additional amounts of elements from the soil solution, while the irregular alternation of increases and decreases in Ca, Mg, S, Fe and Mn indicates the reversible nature of the process. Due to the significant differences between the types of green manure in terms of chemical composition, rate and dynamics of decomposition and release of nutrients, their use provides great opportunities for managing soil fertility and the intensity of elements cycling in agrocenoses through the species selection.

Assessment of ozone pollution on rice yield reduction and economic losses in Sichuan province during 2015–2020

In recent years, there has been a significant increase in surface ozone (O3) concentrations in the troposphere. Ozone pollution has significant adverse effects on ecosystems, human health, and climate change, particularly on crop growth and yield. This study utilized the observational hourly O3 data, cumulative O3 concentration over 40 ppb per h (AOT40), and the mean daytime 7-h O3 concentration (M7) to analyze the spatiotemporal distributions of relative yield losses (RYLs) and evaluate the yield reduction and economic losses of rice in Sichuan province from 2015 to 2020. The results indicated that the average O3 concentration during the growing rice season ranged from 55.4 to 69.3 μg/m3, with the highest O3 concentration observed in 2017, and the AOT40 ranged from 4.5 to 8.7 ppm h from 2015 to 2020. At the county level, the O3 concentration, AOT40, and the relative yield loss (RYL) of rice based on AOT40 exhibited clear spatiotemporal differences in Sichuan. The RYLs of AOT40 were 4.9–9.2% from 2015 to 2020. According to AOT40 and M7 metrics, the yield loss and economic losses attributed to O3 pollution amounted to 78.75–150.36 (9.74–21.54) ten thousand tons, and 2079.08–4149.89 (257.25–594.45) million Yuan, respectively. Rice yield and economic losses were relatively large in the Chengdu Plain, southern Sichuan, and northeast Sichuan. These findings will contribute to a deeper understanding of the detrimental effects of elevated surface O3 concentrations on rice crops. It is imperative to implement more stringent O3 reduction measures aimed at lowering O3 concentrations, enhancing rice quality, and safeguarding food security in Sichuan.

A Single Image High-Perception Super-Resolution Reconstruction Method Based on Multi-layer Feature Fusion Model with Adaptive Compression and Parameter Tuning

We propose a simple image high-perception super-resolution reconstruction method based on multi-layer feature fusion model with adaptive compression and parameter tuning. The aim is to further balance the high and low-frequency information of an image, enrich the detailed texture to improve perceptual quality, and improve the adaptive optimization and generalization of the model in the process of super-resolution reconstruction. First, an effective multi-layer fusion super-resolution (MFSR) basic model is constructed by the design of edge enhancement, refine layering, enhanced super-resolution generative adversarial network and other sub-models, and effective multi-layer fusion. This further enriches the image representation of features of different scales and depths and improves the feature representation of high and low-frequency information in a balanced way. Next, a total loss function of the generator is constructed with adaptive parameter tuning performance. The overall adaptability of the model is improved through adaptive weight distribution and fusion of content loss, perceptual loss, and adversarial loss, and improving the error while reducing the edge enhancement model. Finally, a fitness function with the evaluation perceptual function as the optimization strategy is constructed, and the model compression and adaptive tuning of MFSR are carried out based on the multi-mechanism fusion strategy. Consequently, the construction of the adaptive MFSR model is realized. Adaptive MFSR can maintain high peak signal to noise ratio and structural similarity on the test sets Set5, Set14, and BSD100, and achieve high-quality reconstructed images with low learned perceptual image patch similarity and perceptual index, while having good generalization capabilities.

Amount, distribution and controls of the soil organic carbon storage loss in the degraded China's grasslands

More than 80 % of China's grasslands are classified as degraded, and the loss of soil carbon storage due to degradation has a significant impact on China's terrestrial carbon sinks as well as carbon neutrality targets. The loss of soil carbon storage in degraded grasslands can serve as a benchmark for quantifying the carbon sequestration capacity of restored grasslands in the future. Here, above- and below-ground biomass, soil organic carbon (SOC) content at various depths (0–100 cm) and soil bulk density were collected from 226 degradation sequences around China. The above information was integrated and statistically analyzed to quantify the difference of SOC storage between the degraded and natural grassland at national scale. The result showed that grassland degradation led to a significant reduction in SOC storage across different depths. SOC (0–100 cm) of degraded grassland decreased by 39 % compared to that of natural grassland, ranging from 21 % in the lightly degraded sites to 59 % of the extremely degraded sites. 15 potential predictors were used to estimate the national amount of these differences of 0–20 cm depth SOC storage as 5.29 ± 1.59 Pg C. This considerable carbon storage gap implies the necessity of China's grassland restoration project in achieving carbon neutrality goals in the future.

Performance research and improvement of ultra-high-speed R290 rotary compressor

With the trend towards miniaturization of rotary compressors, increasing the speed of compressors and improving performance at high speed have become important research directions. Simultaneously, due to the need for refrigerants with low global warming potential (GWP), R290 has become an important alternative to hydrofluorocarbons (HFCs). Under the same compressor structure size, meeting the cooling/heating demands with R290 necessitates higher operating speed owing to its lower cooling capacity per unit volume. In this paper, the performance loss distribution of an ultra-high-speed R290 rotary compressor has been studied theoretically and experimentally, and the accuracy of theoretical calculation was verified through experiments. According to the calculation, the primary factor influencing the performance of the ultra-high-speed rotary compressor is over-compression loss. Consequently, corresponding solutions to improve the performance of the ultra-high-speed compressor were proposed. The internal parameters of the compressor were measured, thereby validating the conclusions and assessing the efficacy of the proposed solutions. Finally, the structure parameters were further optimized, which was also verified by experiments. It is found that the double-valve structure can effectively reduce the over-compression loss. When operating at 10,800 rpm under the ASHRAE T1, compared with the prototype, the compressor with double-valve structure can reduce the over-compression loss by 45.0 %, and increase the cyclic thermodynamic perfection by 7.85 %.