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The disc-seal single screw pump (DSSP) used in the field of high viscosity oily sludge transport has a huge advantage. However, there is no research on the pressurization characteristics of the DSSP at present, which makes its application limited. In view of this, the pressurization process mathematical model of the DSSP was established based on the geometric model of the pump. By using this model, the pressurization characteristics of DSSP and the influence of working parameters on the pressurization process were studied combined with the principle of back-flow pressurization. Analysis results show that the instantaneous pressurization process could be realized mainly depending on the reflux pressurization from the outlet chamber to the pressurization chamber when the screw rotor rotating angle is located at -5° to +5°. The pressure in the pressurization chamber will increase with the increase of working parameters which include inlet pressure, outlet pressure, screw rotation velocity and dynamic viscosity of fluid medium in the area of flow-back pressurization. The screw rotation velocity and the viscosity of the conveying medium have significant effects on the peak pressure in the pressurization chamber, and the peak pressure in the pressurization chamber is proportional to the screw rotation velocity and the dynamic viscosity coefficient of the conveying medium. The proportional coefficient between the peak pressure and the screw rotation velocity is 6.29×104. The proportional coefficient between the peak pressure and the dynamic viscosity of the conveying medium is 6.28×106.

A 90° elbow equipped with guide vanes was developed with the intent of reducing elbow erosion. Numerical models were formed to predict the maximum erosion rate of elbow and Face-1, and the response surface methodology was used to study the relationship between the erosion rate and structural parameters of guide vane. A second-order response surface model was established to determine the relationship between R1 and variables, and a reduced cubic (RC) polynomial model was obtained to reveal the relationship between R2 and the three factors. The numerical results show that the low-speed region is expended and the maximum discrete particle matter (DPM) concentration is reduced after installing the guide vane. This internal component provides a shelter for the elbow from the direct impact of high-speed solids.

The twin-screw expander is widely used in many low-grade energy recovery systems. Its built-in volume ratio has a crucial impact on the system performance. Large built-in volume ratio can expand both the application and scope of the twin-screw expander, and can improve the efficiency of the power generation cycle as well. In this study, a novel pair of intermeshing cross-axis conical twin-screw rotors (CCSRs) with large built-in volume ratio and large expansion ratio for the twin-screw expander was proposed. The conjugate meshing of CCSRs can be achieved by using spherical-sectional profiles. Geometric performance of the proposed CCSRs was studied. Moreover, a thermodynamic model and numerical simulations of the working process of the proposed cross-axis conical twin-screw expander (CCSE) were established, and the working performance and thermodynamic characteristics during the expansion process were analyzed. Study results indicate that the proposed CCSRs exhibit a larger built-in volume ratio, and the corresponding twin-screw expander has a larger expansion ratio than that of the traditional one. The contents will be beneficial to the improvement and development of the twin-screw expander and energy recovery systems.

In some cases Metformin (MF) produces intestinal discomfort and increased risk of dysbiosis. We developed a novel astragalus compound oral solution (termed "OS") and investigated effects of treatments with OS alone or in combination with metformin (MF) in a type 2 diabetes (T2D) mouse model. OS can treat T2D in mice. OS, in comparison with MF (OS + MF), was more effective in improving HDL, ALT, hepatic glycogen, and GSH-px levels, and in protecting several organs simultaneously. Gut microbiota composition and diversity were significantly better for OS and OS + MF than for MF. Helicobacter, Oscillospira, Mucispirillum, Dehalobacterium, Anaerotruncus, Subdoligranulum, Akkermansia, Allobaculum, and Ochrobactrum were significantly correlated with FBG, liver function indicators, and islet cell areas. Our findings suggest that OS applied in combination with MF promoted health in the T2D mouse model through effects on 192 related targets to regulate glucose and lipid metabolism, protect organs, and improve gut microbiota composition

The scroll geometry in the central region of the scroll wrap plays a crucial role in determining the working performance of scroll compressors. In order to improve the comprehensive performance of scroll wraps, in this study, a novel circular involute modified wrap was put forward, in which the central and peripheral wrap profiles were connected by a circular involute in the central regions, so that a pair of fully smooth and correct meshing scroll wraps were generated. A geometric model of the involute modified wrap were proposed, and then equations of the wrap profiles and relations between geometric parameters were derived. Effects of geometric parameters on the shape and performance of the involute modified wrap were discussed in detail. Furthermore, the compression ratio of the involute modified wrap was studied by numerical simulation, and the deformation of the involute modified wrap produced by temperature load and pressure load was calculated, compared with the conventional circular arc modified wrap under the same geometric shape of scroll compressors. Study results demonstrate that the proposed involute modified wrap may simultaneously improve the compression ratio and the strength of wrap head for scroll compressors; in addition, the involute modified wrap is good for design flexibility, and therefore is superior to the circular arc modified wrap.

Compared to traditional air freezing, immersion chilling and freezing shows an improvement in the freezing effect on meat quality, but it is not known whether this advantage persists over longer storage periods. Therefore, the objective of the current study was to compare the effects of immersion chilling and freezing (ICF) and traditional air freezing (TAF) on the physical and chemical indexes in beef longissimus muscle during a storage period of 150 days. In the current study, the longissimus muscle from Luxi cattle (aged 20–24 months) was analyzed, with samples independently frozen by ICF and TAF. After the core temperature was frozen to below −18 degrees by the two chilling methods, samples were transferred to a −18 degrees cold room for further storage. During the storage period, physical and chemical indexes, mainly including color and texture qualities, total volatile base nitrogen (TVB‐N) and peroxide value (POV) were measured and comparatively analyzed at several fixed time points. A higher freezing rate was observed in ICF (5.124 cm/h) than in TAF (0.194 cm/h), and better microstructure was observed in ICF treatment. Besides, peak force values and total energy values were significantly lower in the TAF group than in the ICF group during the first 45 days of freezing storage time (p, Freezing is one of the most effective ways to preserve the quality of beef and is used to minimize the product loss. Many studies have demonstrated that the immersion chilling and freezing shows good improvement on the freezing effect of meat quality; however, it is not known whether this advantage will still exist in a longer storage period. The aim of current study was to explore the effects of different freezing methods, including the immersion chilling and freezing (ICF) and traditional air freezing (TAF), on the physical and chemical indexes in beef longissimus muscle during a period of 150‐day storage.

Background Crime researchers often use publicly available geocoding services to obtain crime locations and conduct subsequent analysis. The quality of these geocoding platforms has not been extensively investigated, especially in the crime research field. The match rate is often employed for this purpose, but this measures only absolute performance at a specified scale and cannot reflect the performance of a platform at different accuracy levels. By expanding match rate to multiple scales, we compared the quality of publicly available geocoding services in China. Methods In this study, we develop a set of evaluation metrics by clarifying the definition of the match rate and considering the multiscale characteristics of geocoding errors. To interpret the geocoding errors of addresses, the positional errors are classified into more detailed types in accordance with their topological relationships with mapping units. Using burglary addresses recorded in N city, the quality of the geocoding services provided by four mainstream online geocoding services in China are compared based on these metrics. Results The match rates of the four geocoding platforms are high enough to maintain the burglary distribution patterns at the subdistrict and district levels but cannot satisfy this need at the building level. Three of the four platforms can geocode enough addresses for spatial analysis at the community level, while Tencent cannot. For commercial addresses, the match rates of the four platforms for residential addresses cannot satisfy the needs of burglary mapping at the building level but can satisfy these needs at any other level. For residential addresses, Tencent is the only platform that cannot provide satisfactory results for community-level mapping. For gated community-level mapping, Baidu and Tianditu can provide marginally satisfactory results. Based on the accuracy levels provided by each platform, the applicability of the results at each level are further analyzed. Conclusions Although this study is limited by address type and data volume, the results suggest users to select appropriate geocoding service based on mapping unit sizes and address types. The results can also help users determine whether the geocoding result at certain accuracy level meet their needs. This research also provides guidance for address-based users beyond crime analysis.

This article examines whether different levels of entry controls impact burglary rates in gated communities. It differs from the previous studies that only distinguish gated communities from non-gated communities but ignore important variation in different levels of entry controls. A sample of 698 gated communities in a large Chinese city are selected for this study. A negative binomial regression model estimates the relationships between entry control levels and burglary rates in gated communities. The test of these relationships accounts for the control of other important explanatory variables, including management fee, building height, building age, housing price, house for sale, rental house and floating population. Results indicate that higher entry control levels are associated with significantly lower burglary rates in gated communities. This is the first study that reveals a quantitative relationship between burglary and entry control level in gated communities at the city-wide scale.

As a new type of fluid machinery, the disc-seal single screw pump (DSSP) is vital for energy conversion in oil sludge energy recovery systems and natural gas liquefaction system due to the advantages of wide flow range, strong self-absorption and well adaptability to organic solid impurities. However, no research work has focused on the working mechanism and performance of this pump at present, which makes its application limited. In view of this, the in-depth theoretical study on the meshing characteristics and operating performance of the DSSP must be carried out. In this paper, the profile equations of the meshing pair and the working process mathematical model were established for the first time based on three-dimensional space meshing theory, coordinate transformation principle. By using this model, the working performance of this pump was investigated, and the influence mechanism of the profile parameters on the theoretic volume was analyzed. The results of the analysis show that DSSP has the best leakage characteristics when the seal disc rotation center fell on the screw rotor touchline. All these analyses can provide the theory basis for improving the performance of the pump and optimized design of the meshing pair.

The disc-seal single screw pump (DSSP) is the key devices for liquid refrigerant conveying. However, there is little research on the suction capacity of this pump at present, which makes its application limited. In view of this, a mathematical model of the suction volume was established firstly based on the three-dimensional meshing theory. By using this model, the suction capacity calculation model was put forward, and the suction capacity and the impact mechanism of working parameters on it were investigated. The theoretical calculation results are in good agreement with the actual engineering data with the deviation not more than 6.5%. The results obtained by this validated model show that DSSP has abundant suction capacity with a suction capacity far more than 1 and the suction capacity varies in inverse proportion to density and rotation speed. All of these studies can provide theoretical basis for improving the performance of the DSSP.

A pair of screw rotors, the core components of twin-screw multiphase pumps, primarily determine the pump performance. The conventional screw rotor contains unsmooth edges caused by unsmooth points in the cross-sectional profiles, which will lead to the abrasion, wear and fatigue near the unsmooth edges of the screw rotors during operation. For solving this problem, a novel pair of fully smooth screw rotors without unsmooth edges were proposed, and their cross-sectional profiles composed of the elliptical arcs and their conjugate curves were put forward. Parametric equations of the proposed screw rotor profiles were also derived, and then the effects of geometric parameters on the pump performance of the proposed screw rotors were discussed. Furthermore, the transient flow of the twin-screw multiphase pump with the proposed screw rotors were carried out by numerical simulations. The distributions of pressure and velocity in the proposed pump were obtained. The gap leakage and backflow velocity at each gap varying with time and location in the working process were also analyzed. The results indicate that the carryover of the proposed screw rotors is reduced by 90.49%, while its area utilization ratio is increased by 0.8%, and the length of the spatial contact curve is reduced by 25.71% in comparison with the conventional screw rotors. Thus, the superiority and feasibility of the proposed screw rotors are validated.

The head-on collision of two water droplets with a diameter of 10 nm in an atmospheric environment was investigated via molecular dynamics simulations. The gas molecules between droplets were visualized, and the phenomena of gas extrusion and gas molecules being captured were found. By observing and analyzing the holes regime, a "periphery-sucking" mechanism was proposed to explain the thinning in the middle of the expanding disk and the holes appearing. It was found that the splattering regime can be divided into the limited splattering regime and the divergent splattering regime. The splattering modes and droplet characteristics of the two regimes are markedly different. The non-bonded interactions and intermolecular hydrogen bond were analyzed, and it was found that increasing the Weber number (

We constructed a novel β-mannanase/GLP-1 fusion peptide, termed MGLP_1, and evaluated its ability to ameliorate obesity in a high-fat/high-sugar diet (HFSD)-induced mouse model. Eight-wk MGLP_1 treatment notably reduced obesity, as reflected by significant changes of body weight, serum triglyceride level, fatty liver and adipose tissue distribution. Amelioration of HFSD-induced gut dysbiosis by MGLP_1 was evidenced by reduced abundance ratio of bacterial phyla Firmicutes to Bacteroidetes, enhanced abundance of beneficial probiotic genera (Bifidobacterium, Lachnospiraceae, Ileibacterium), and reduced abundance of harmful genera (Clostridium, Romboutsia). Mechanisms of weight loss were investigated by comparing effects of treatment with MGLP_1 vs. prebiotics manno-oligosaccharides (MOS). MGLP_1 ameliorated gut microbiota imbalance by enhancing carbohydrate catabolism, whereas MOS promoted glycan synthesis and metabolism. Our findings, taken together, indicate that MGLP_1 fusion peptide has strong potential for amelioration of obesity by modifying relationships between gut microbiota and lipid and glucose metabolism.

In single screw compressor (SSC), the inner surface of the working chamber has always been a key issue that affects oil application and heat transfer. However, the geometric characteristics for the inner surface of the working chamber in SSC with Multicolumn Envelope Meshing Pair (MEMP) have not been carried out yet. Therefore, in this paper, a geometric model of working chamber inner surface for the SSC with MEMP is established to predict the geometric characteristics of the working process. The presented model is verified as a powerful tool for geometric characteristics analysis by the simulation results. With the validated model, the geometric characteristics of the working process and the effect of MEMP structural parameters on the geometric characteristics and the working performance for the SSC with MEMP have been analyzed. Through the comparison of the inner surface area with different structural parameters, optimization analysis of the structural parameters can be obtained. All of this work can provide the basis for the later heat transfer analysis and optimization structural design of the SSC.

Purpose Shear stresses have a considerable influence on the characteristics of lubricants and become significant at high rotating speeds. This study aims to investigate the influences of shear cavitation (SC) on loading capacity of journal bearings. Design/methodology/approach A principal normal stress cavitation criterion based on the stress applied to flowing lubricant in journal bearings is developed and used to investigate SC in journal bearings. A computational fluid dynamic (CFD) model for calculating the loading capacity is established using this criterion. After validation with experimental results, the loading capacity is calculated under different conditions. Findings The calculation results indicate that SC intensifies when viscosity, speed and eccentricity increase. Angle of loading capacity with SC is larger than that without SC. The magnitude of loading capacity with SC is smaller than that without SC due to the decrease in the ultimate pressure. In addition, the magnitude difference between the loading capacity with and without SC increases when viscosity, speed and eccentricity increases. Originality/value Present research can provide some guidance for calculating the loading capacity when a journal bearing is operating at high speed or with a high viscosity lubricant.

Purpose Frequent itemset mining (FIM) is a basic topic in data mining. Most FIM methods build itemset database containing all possible itemsets, and use predefined thresholds to determine whether an itemset is frequent. However, the algorithm has some deficiencies. It is more fit for discrete data rather than ordinal/continuous data, which may result in computational redundancy, and some of the results are difficult to be interpreted. The purpose of this paper is to shed light on this gap by proposing a new data mining method. Design/methodology/approach Regression pattern (RP) model will be introduced, in which the regression model and FIM method will be combined to solve the existing problems. Using a survey data of computer technology and software professional qualification examination, the multiple linear regression model is selected to mine associations between items. Findings Some interesting associations mined by the proposed algorithm and the results show that the proposed method can be applied in ordinal/continuous data mining area. The experiment of RP model shows that, compared to FIM, the computational redundancy decreased and the results contain more information. Research limitations/implications The proposed algorithm is designed for ordinal/continuous data and is expected to provide inspiration for data stream mining and unstructured data mining. Practical implications Compared to FIM, which mines associations between discrete items, RP model could mine associations between ordinal/continuous data sets. Importantly, RP model performs well in saving computational resource and mining meaningful associations. Originality/value The proposed algorithms provide a novelty view to define and mine association.

In single screw refrigeration compressor (SSRC), the wear of meshing pair has always been a key issue that restricts its development. In order to solve this problem, a Multicolumn Envelope Meshing Pair (MEMP) was proposed. However, the theoretical research on wear resistance of MEMP has not been carried out yet. Therefore, in this paper, a theoretical calculation model describing the influence of the MEMP profile parameters on wear characteristics of the SSRC with MEMP is established to predict the wear resistance. The presented model is verified as a powerful tool for wear characteristics analysis by the experimental results. With the validated model, the effect of MEMP profile parameters on the wear characteristics of SSRC has been analyzed. Optimization analysis shows that in the design stage more envelope columns with a larger center distance and larger envelope column diameter should be chosen for the MEMP to get a better wear resistance.

The claw rotor profile is one of the key factors for improving the performance of claw vacuum pumps. In order to develop novel types of claw rotor profiles, the conjugate curves of claw rotor profiles were calculated, and therefore two types of straight claw rotors, a cusp claw rotor and a smooth claw rotor, were proposed in this study. Geometric models of the proposed claw rotors were established, and profile equations were also derived. Moreover, effects of the independent geometric parameters on shapes of the claw rotors and the performance of pumps were analyzed. The stress and deformation of two proposed claw rotors loaded by gas pressures at the end moment of the discharge process were analyzed and compared. The study results indicate that the cusp claw rotor is a special case of the smooth claw rotors, when the value of tip circular arcs equals to zero. The smooth claw rotor is superior to the cusp claw rotor in terms of the working performance and mechanical property.

Purpose Surface texturing has been proven as an effective means of contact performance enhancement. However, limited work has been done to investigate the regular relationship to solve the multi-parameters problem of textures, and inertia effect and elastic deformation were seldom considered together in previous optimization work. This paper aims to quantitatively obtain the relationship between the textured depth and liquid film thickness and find the effect of deformation on the optimal textured height ratio in elastic parallel sliders. Design/methodology/approach Numerical models of hydrodynamic lubrication are established based on the computational fluid dynamic method. Elastic deformation is considered through fluid–structure interaction (FSI) method. Using response surface optimization method, textured parallel sliders are optimized with maximum loading capacity as the objective. Findings The results show that the optimal height ratios are all within the range of 0.60-0.65 when textured parallel sliders are considered as rigid. After considering the effect of elastic deformation, loading capacity drops and is reduced more obviously with a decrease in the elastic moduli. The optimal height ratios are within the range of 0.60-0.63, which shows that FSI has a considerable influence on loading capacity but has no significant influence on the optimal height ratio. Originality/value The present research provides a theoretical reference for engineering application of elastic textured parallel sliders.

A geometric model of a 1-pair of circular arcs modified wrap (1-CMW), the existing circular arc modified wrap (CMW), was developed. In order to improve the performance and overcome its shortcoming of the CMW, a novel n-pair of circular arcs modified wrap (n-CMW) for scroll compressors was proposed based on the midline design method. A 2-CMW was analyzed, and then a general geometric model of n-CMW with arbitrary pair number n was established. In addition, the generation procedure, general mutual dependence of geometric parameters as well as equations of wrap profiles were obtained, and the influence of geometric parameters on shapes of the n-CMW was analyzed. Flow simulations of the 1-CMW, 2-CMW, 3-CMW and 4-CMW during the working process with the same conditions were conducted. Study results indicate that the proposed n-CMW increases the built-in volume ratio and design flexibility, and is superior to the existing CMW.

The Qinghai-Tibetan Plateau, with low precipitation, low oxygen partial pressure, and temperatures routinely dropping below −30 °C in winter, presents several physiological challenges to its fauna. Yet it is home to many endemic mammalian species, including the plateau pika (Ochotona curzoniae). How these small animals that are incapable of hibernation survive the winter is an enigma. Measurements of daily energy expenditure (DEE) using the doubly labeled water method show that pikas suppress their DEE during winter. At the same body weight, pikas in winter expend 29.7% less than in summer, despite ambient temperatures being approximately 25 °C lower. Combined with resting metabolic rates (RMRs), this gives them an exceptionally low metabolic scope in winter (DEE/RMRt = 1.60 ± 0.30; RMRt is resting metabolic rate at thermoneutrality). Using implanted body temperature loggers and filming in the wild, we show that this is achieved by reducing body temperature and physical activity. Thyroid hormone (T(3) and T(4)) measurements indicate this metabolic suppression is probably mediated via the thyroid axis. Winter activity was lower at sites where domestic yak (Bos grunniens) densities were higher. Pikas supplement their food intake at these sites by eating yak feces, demonstrated by direct observation, identification of yak DNA in pika stomach contents, and greater convergence in the yak/pika microbiotas in winter. This interspecific coprophagy allows pikas to thrive where yak are abundant and partially explains why pika densities are higher where domestic yak, their supposed direct competitors for food, are more abundant.