Spacing Ratio Research Articles

Analysis of the cross-flow features around two side-by-side rectangular cylinders

This study employs the lattice Boltzmann method (LBM) to numerically analyze the fluid flow around two side-by-side rectangular cylinders with an aspect ratio (AR) of 3:2. The gap spacing (G) between the cylinders is taken in the range 0–10 and the Reynolds number (Re) is fixed at 200. The numerical outcomes depict a strong correlation between flow patterns, force variations, gap spacing, and aspect ratio. Among these parameters, the latter ones strongly influence the flow-induced drag, lift, and pressure. The mean drag coefficient (CDmean), Strouhal number (St), and root-mean-square values of force coefficients exhibit rapid variations under the impact of these parameters for both cylinders. The observed outcomes further indicate that flow structures in the wake vary with changes in gap spacing. Five separate patterns of wake flow are detected, depending on varying gap spacing. These patterns include isolated bluff-body flow, flip-flopping flow, non-synchronized flow, modulated synchronized flow, and synchronized flow.

FeNiCo@lyocell-based carbon cloth cathode for enhanced seawater electrolysis with bipolar membrane

The formation of inorganic precipitates at the cathode is the most persistent problem in direct seawater electrolysis (DSWE) for hydrogen production. To address this issue, we demonstrate the combination of lyocell-based carbon cloth (CC, as a conductive substrate) and bipolar membrane (BPM)-based DSWE. The entire process, from fabricating lyocell-based CC to coating FeNiCo catalysts, is conducted to ensure stable adhesion between the CC surface and electrocatalysts, thereby enhancing charge transfer. The hydrogen evolution reaction activity of FeNiCo@lyocell-based CC in 1.0 M NaOH shows the overpotential of 152 mV at 10 mA/cm2, which is much lower than that (342 mV) of bare lyocell-based CC. When the FeNiCo@lyocell-based CC is used as a cathode in the BPM-DSWE, the growth rate of inorganic precipitates formed at the cathode is significantly reduced. As a result, the rate of increase in cathodic potential over 100 h at 100 mA/cm2 is approximately 6 %, which is more than four times smaller than that of Pt-coated Ti foam. The woven structure of the lyocell-based CC provides small holes densely distributed at regular intervals and empty spaces between carbon fibers arranged in the same direction. The unique structure is expected to help the protons generated from the BPM escape directly into bulk seawater. In this process, free protons can play a role in reducing the high pH formed at the interfaces of each fiber, slowing down the growth rate of inorganic deposits. If the empty space ratio of the porous structure and the three-dimensional connectivity are optimized for BPM-DSWE, lyocell-based CC is expected to be a promising conductive substrate that can suppress the formation of inorganic deposits even at higher current densities.

Combined effect of diameter ratio and spacing ratio on flow around two tandem circular cylinders at a moderate Reynolds number (Re)

Combined effect of diameter ratio and spacing ratio on flow around two tandem circular cylinders at a moderate Reynolds number (<i>Re</i>)

Direct numerical simulation study on convective heat transfer of two tandem permeable square cylinders

This study focuses on two-dimensional heat transfer and unsteady flow past two tandem heated porous square cylinders using lattice Boltzmann method combined with block-structured topology-confined mesh refinement. The effects of the Reynolds number (30≤Re≤150), the Darcy number (10−5≤Da≤10−2), and spacing ratio (1.5≤L/D≤5, where L and D are distance of two adjacent cylinder centers and square cylinder length, respectively) are investigated. The intended analysis links hydrodynamic and heat transfer coefficients and wake structures in parameter space of Re−Da−L/D to fluid mechanics. For upstream cylinder, drag coefficients decrease with a reduction of Da and range of Re≥100, while wake length increases with an increment of L/D ratio at the same range of Re. Time-averaged normalized velocity increases at higher permeability levels. A significant augmentation in a time-averaged Nusselt number is reported for an increase in Da and full L/D range. For downstream cylinder, the interaction of fluid vortices in the gap between the cylinders affects the flow pattern, causing irregularities in the drag coefficient variation. The impacts of L/D on the wake length is more obvious than that of Da. Both the wake length and time-averaged Nusselt number values are proportional to an increase in L/D. Consequently, all the investigated results of the upstream cylinder are significantly altered from those of the downstream cylinder due to the shadowing effect of the upstream cylinder.

Effect of Flow Interference between Cylinders Subjected to a Cross Flow over a Cluster of Three Equally Spaced Cylinders

In this paper, flow over a cluster of three equally spaced circular cylinders was studied by numerical simulation based on the turbulence model k-kl-ω for two incidence angles β = 0° and 60°, at different Reynolds numbers, and flow interference pattern characteristics between cylinders, characteristics of force parameters, and Strouhal number of each cylinder with different spacing ratios ranging from 1.5 to 4 at Re 8 × 104, 2 × 105 and 2 × 106 were obtained. Analyzing the flow field around three cylinders, the following results have been obtained: (1) at incidence angle β = 0° and 60°, the wake was nearly symmetrical if S/D ≥ 2.0; (2) at β = 60°, S/D = 1.5, and Re = 2 × 105, an asymmetric periodic flow pattern occurred in the wake region which produced a significant effect on the surface mechanical parameters and Strouhal number, and this was observed for the first time. The periodic flow regime of the wake region also occurred at S/D = 1.35 and 1.5, without the same phenomenon at S/D = 1.7 and 2.0; this phenomenon is described for the first time in this paper; (3) the phenomenon of periodic flow regime in the wake region was intrinsic and related to Reynolds number and space ratio. In addition, the characteristics of force parameters of three cylinders were mainly affected by the interference between cylinders, at 1.5 &lt; S/D &lt; 4, which indicated that the drag coefficient of three cylinders reduces with different Reynolds numbers and increases with enlargement of the spacing ratio for upstream cylinders at incidence angle 0°. At incidence angle 60° and S/D = 1.5~4, the Strouhal number decreases with the enlargement of spacing ratio for the upstream cylinders, but the Strouhal number increases for the downstream cylinder, which is another prominent flow interference influence. The results indicated the effect of flow interference between cylinders subjected to a cross flow over a cluster of three equally spaced cylinders, considering the flow pattern, surface mechanical parameters and Strouhal number, which should be considered in the establishment of standard design codes in fields such as offshore wind turbine engineering for flow interference around groups of cylinders.

Double Mini TightRope Suture Suspensionplasty with FCR to APL Imbrication for Thumb Basilar Joint Arthritis: Intermediate Outcomes

Abstract Background We sought to evaluate the intermediate term outcomes of trapeziectomy with double Mini TightRope suture suspensionplasty and flexor carpi radialis to abductor pollicis longus imbrication for the treatment of basilar thumb joint arthritis. Case Description We performed a retrospective review of patients from 2012 to 2021 at a single institution within a standardized protocol. Thirty-nine patients (46 thumbs) with a mean age of 61 years and clinical follow-up of 2.8 years met our inclusion criteria. Grip strength increased from 13.8 kg preoperatively to 20.3 kg postoperatively. Appositional pinch strength increased from 3.7 to 5.7 kg, while oppositional pinch strength also increased from 2.8 to 4.4 kg. Trapezial space ratio was well maintained at 0.36 postoperatively compared with 0.46 preoperatively at a mean radiographic follow-up of 2.2 years. Literature Review and Clinical Relevance Results from our series demonstrate predictable outcomes with reduced pain levels, increased grip and pinch strengths, improved function, and preserved range of motion with few complications. Level of Evidence III therapeutic. Trial Registration Not applicable.

Investigation on the failure mechanism for surrounding rock in small interval tunnels using finite element limit analysis method

This paper presents a case study to evaluate the failure mechanism of surrounding rock in mountain tunnels caused by small interval parallelism and the reinforcement effect of intermediate rock columns. The characteristics and reasons of surrounding rock collapse were analyzed through field investigation, taking Yaoxi Tunnel as a case study. The critical collapse and blowout pressure results obtained by the finite element difference method (FEDM) software FLAC and the finite element limit analysis method (FELAM) software OPTUM were compared based on Mollon’s theoretical solution. The critical support pressure errors for collapse are 18.803% and 8.129%, indicating that OPTUM has a slight advantage in accuracy for solving tunnel collapse. Therefore, the models of small interval tunnels were established by OPTUM to investigate the collapse failure mechanism and progressive failure process of surrounding rock. The effects of tunnel depth ratio (H/D), spacing ratio (S/D), and surrounding rock parameters (γ, φ, c) on critical support pressure, failure mode, and surrounding rock settlement laws were studied through simulation models. It shows that the gradual decrease in mechanical parameters of rock is the main cause of the increase in critical support pressure. The design parameters (H/D, S/D) have a mutagenic effect on the pressure arch of the double tunnel surrounding rock. As the distance between the two holes increases, the joint pressure point in the intermediate rock column gradually rises. Finally, the effectiveness of the reinforcement measures for the intermediate rock column was verified through on-site monitoring. The research results of this study have reference price for similar projects.

Spatiotemporal heterogeneity of the relationship between urban morphology and land surface temperature at a block scale

Understanding the relationship between urban morphology and land surface temperature (LST) is essential for mitigating urban heat island (UHI). This study investigates the spatiotemporal heterogeneity of the relationship between urban morphology and LST across 5 experiment sites located in different temperature zones of China at a block scale. Normalized difference vegetation index (NDVI), building density (BD), floor area ratio (FAR), average building height (ABH) and open space ratio (OSR) are adopted to indicate the physical urban morphology. The results show positive relationship between BD and LST, and negative relations between LST and NDVI, ABH and OSR from a global perspective. The relations of FAR to LST are mixed. However, variable relationship between urban morphological indicators (UMIs) and LST are significantly observed at a block scale. 12 scenes that generate local relations of UMIs and LST differing from that of the surroundings are identified. Typical strategies for land development, vegetation phenology, large natural elements and human activities may be the most important causative factors to the heterogenous relationship between urban morphology and LST. Findings derived in the study would promote studies on mechanisms of the effects of urban morphology on LST and contribute to practices of UHI mitigation.

Categorisation of urban open spaces for heat adaptation: A cluster based approach

In the context of climate change, adapting a city's open spaces to heat waves and extreme heat is crucial for mitigating the Urban Heat Island effect and ensuring the wellbeing of its inhabitants. However, the heat adaptation potential of open spaces varies within a city. This study develops an objective and replicable method to categorise urban areas based on their open spaces' adaptive capacity and improvement potential to heat waves at the micro-scale. This is achieved using a clustering approach, eliminating manual operations, using openly available data, employing indicators suitable for every urban fabric type, and using the urban block as the analysis unit. The validation of the method in the case study of Bilbao (Spain) demonstrates its capacity to obtain meaningful insights regarding open space heat adaptation potential. An analysis of the resulting categories reveals significant open space improvement potential throughout the city and a varying adaptive capacity that depends on urban density. Categories with the lowest adaptive capacity have median open space ratios between 0.35 and 0.65 and median tree cover ratios between 0.07 and 0.15. Those with the highest adaptive capacity present median open space ratios between 0.8 and 1 and median tree cover ratios between 0.05 and 0.25. The method can aid local policymakers in identifying opportunity spots for hosting adaptation solutions and understanding the challenges the city may face in planning adaptation action. The method's replicability enables it to be applied in other cities, contributing to a broader exploration of climate change adaptation potential.

A quasi in-situ investigation of the cell to dendrite transition using Ni-W single crystal alloy

A quasi in-situ investigation of the cell to dendrite transition (CDT) was carried out by preparing Ni-W single crystal alloy with an increasing withdrawal rate. It was shown that the solidification process occurred under the convex growth interface, which produced a gradient of the drift velocity along the interface and led to a coarsening effect on the microstructures. This coarsening effect, combined with the refining effect induced by the increasing withdrawal rate, resulted in the CDT and an inconstant primary spacing. The results showed that the cell to dendrite transition for hexagonal cell was nonuniformed, and the tip splitting and lateral branching for cellular and dendritic structures were controlled by the ratio of the neighbor spacing to the average primary spacing. Two models and a rule, which separately revealed the influence factor of the drift velocity, the transition process from cell to dendrite, and the law of tip splitting and lateral branching for cellular and dendritic structures, were proposed. It was hoped that the present work could provide ideas for in-situ studies of microstructural evolution.

P-207 Analysis of oocyte morphology: differences between rescued and non-rescued metaphase II oocytes after conventional ovarian hyperstimulation

Abstract Study question Are there morphological differences between rescued and non-rescued metaphase II oocytes after conventional ovarian hyperstimulation (COH)? Summary answer Rescued metaphase II oocytes have a smaller diameter and a higher zona pellucida/perivitelline space ratio than non-rescued metaphase II oocytes. What is known already The rescue of germinal vesicles and metaphase I in assisted reproduction clinics has increased in recent years, but it is still not widely used because these oocytes have a lower developmental potential compared to oocytes matured in the follicular environment. Recent studies focus on the different strategies for the oocyte maturation process in the laboratory, one of them showed that rescued metaphase II oocytes have a smaller diameter than oocytes matured within the follicular environment. To our knowledge, this is the first study to analyze in detail the morphological differences between in vivo and in vitro matured oocytes. Study design, size, duration This retrospective study includes the analysis of 144 non-rescued metaphase II oocytes images and 181 rescued metaphase II oocytes images obtained after decumulation, or decumulation and in vitro maturation. Images were acquired over four months using Embryoscope TimeLapse systems. Morphological parameters were manually annotated by one single operator, to reduce the discrepancy of measurements, using the drawing tools of the EmbryoViewer software: oocyte area (μm2), polar body area (PBA)(μm2), zona pellucida (μm), perivitelline space (PVS)(μm). Participants/materials, setting, methods First, the different variables measured were analyzed to see if they were related to each other. Then, measurements obtained from images of non-rescued metaphase II oocytes were compared with those of the rescued. In addition, relationships between the different morphological parameters (oocyte area/PBA ratio, oocyte area/zona pellucida ratio, oocyte area/PVS ratio, zona pellucida/PVS ratio, PBA/PVS ratio and PBA/zona pellucida ratio) were calculated and their values were compared between oocytes from different maturation origins. Main results and the role of chance In both rescued and non-rescued metaphase II oocytes, a significantly positive correlation was detected between oocyte area and PBA*, and zona pellucida thickness*. It was also found a significant negative correlation between PVS size and PBA*. For rescued oocytes, a significantly negative correlation was also found between oocyte area and PVS*. Comparison of the means of age, BMI, AMH and all the morphological parameters analyzed between the two groups showed significant differences in age*, oocyte área*, PVS*, oocyte area-zona pellucida ratio*, oocyte area -PVS ratio*, zona pellucida -PVS ratio*, PBA -PVS ratio *. The average of these variables in the rescued oocytes group were: 28.77 ± 6.25, 9734.70 ± 681.28, 8.79 ± 4.43, 628.10 ± 116.29, 1391.86 ± 689.13, 2.24 ± 1.11, 50.84 ± 40.81; while their mean in the non-rescued oocytes group were: 24.41 ± 4.15, 10152.63 ± 711.3, 11.73 ± 5.62, 675,08 ± 111.48, 1063.32 ± 554.35, 1.60 ± 0.82, 37.65 ± 24.55. In addition, multivariable logistic regression showed that the differences in oocyte area size and zona pellucida/PVS ratio remained statistically different between the two groups despite the difference in patient age*. (p&amp;lt;.05*) Limitations, reasons for caution This study is limited by its descriptive and single-center nature. A multicenter study that also evaluates the developmental potential of oocytes would be needed. Wider implications of the findings Our study shows morphological differences between rescued and non-rescued metaphase II oocytes. It could be studied whether these differences are associated with the lower developmental competence of rescued metaphase II oocytes that has been observed in previous studies. Trial registration number Not applicable

Integrated Impacts of Building Space Ratio and Wind Direction on Pedestrian-level Wind Environment around High-rise Buildings with Equilateral Triangle Arrangement

Integrated Impacts of Building Space Ratio and Wind Direction on Pedestrian-level Wind Environment around High-rise Buildings with Equilateral Triangle Arrangement

Aerodynamic force characteristics and flow field mechanism of multiple square cylinders in a tandem arrangement

Wind tunnel tests and large eddy simulations were employed to obtain the aerodynamic coefficients and flow fields of two and three tandem square cylinders across various spacing ratios. The spacing ratio L/D, defined as the ratio of the center-to-center spacing between adjacent square cylinders to their width, ranges from 1.2 to 8. By analyzing these results, the aerodynamic force characteristics and their generation mechanism of the three tandem square cylinders at a high Reynolds number (Re = 3.2 × 104) were revealed. By comparing the results of the two and three tandem square cylinders, the effect of adding a third square cylinder behind the two tandem square cylinders on its aerodynamic characteristics was clarified. The results show that unlike the two tandem square cylinders, the three tandem square cylinders exhibit two critical spacing ratios, (L/D)cr1 = 2.5–3 and (L/D)cr2 = 3.5–4, respectively. Based on these two critical spacing ratios, the flow around the three tandem square cylinders is identified as single blunt body, reattachment, and co-shedding regimes. In the single blunt body and reattachment regimes, the addition of a third square cylinder behind significantly alters the flow around the two tandem square cylinders, leading to reduced mean drag coefficients, fluctuating lift coefficients, and Strouhal numbers, along with an increased critical spacing ratio. In the co-shedding regime, this addition has little effect on the flow.

Wake transitions of flow past two tandem semi-circular cylinders near a moving wall

Wake transitions of flow past two tandem semi-circular cylinders near a moving wall were numerically investigated using the lattice Boltzmann method at the Reynolds number of 150 with various gap ratios (G/D, where G and D are the spacing between the cylinder and wall and the cylinder diameter, respectively) and spacing ratios (L/D, where L is the distance between the cylinder centers). The analysis aims to clarify the effects of L/D and G/D on wake structures, hydrodynamic forces, Strouhal number, and spectral energy of the flow exerted on both cylinders. This study reveals five distinct flow regimes in the L/D-G/D space, such as overshoot, continuous reattachment, pair-wise, quasi-coshedding, and coshedding. These regimes are identified using plots of vorticity contour, time history of drag and lift coefficients (CD and CL), power spectral density, and proper orthogonal decomposition of the vorticity fluctuation into deterministic spatial structures. Furthermore, the flow regime maps and diagrams of time-averaged pressure coefficients on the surface of the cylinders are given to analyze the influence of the moving wall. A significant change in CD and CL is observed for both cylinders, depending on the L/D and G/D ratios. The time-averaged drag coefficient of the downstream cylinder is remarkably lower than that of the upstream cylinder. A significant increase in the time-averaged lift coefficient of the upstream cylinder is observed when the G/D is small due to near-moving wall effects. The root-mean-squared value of the lift and drag coefficients of the downstream cylinder is lower than that of the upstream cylinder as a result of the proximity effect. Meanwhile, the Strouhal number for both cylinders remains mostly the same.

Flow past two diamond-section cylinders in tandem arrangement at a low Reynolds number

The unsteady flow surrounding two fixed diamond cylinders is analyzed at Reynolds number 100 over normalized center-to-center spacing ratios 2−15. By analyzing the contours of instantaneous vorticity, variations of recirculation length, surface pressure, and fluid forcing of cylinders, the value of normalized critical spacing is found to be 3.4. In the reattachment zone below critical spacing, vortex-shedding from the upstream (UC) and downstream (DC) cylinders is anti-phase. At the critical spacing, regular vortex-shedding commences also from the UC, and vortex-shedding from the cylinders becomes phase synchronized for the first time. The analysis of a vortex-shedding cycle at the critical spacing reveals that the cylinders shed vortices at the same frequency, but with a time delay. Impingement of vortices shed from the UC on the DC strengthens vorticity around the DC and shifts the instantaneous position of its forward stagnation point from the leading edge. The understanding that locations of stagnation points govern the direction and magnitude of lift force comes from the analysis of flow at the critical gap. When the surface bounded by stagnation points is occupied mostly with negative vorticity, the instantaneous lift is negative and vice versa. At critical spacing, mean streamlines show the emergence of an anti-wake at forward stagnation point of the DC for the first time. Over the entire range of cylinder separation, nine distinct patterns of separation topologies are identified. Below critical spacing, both pressure and viscous drag components, and hence, total drag of the DC are negative or upstream-acting.

Unsteady wake and heat transfer characteristics of three tandem circular cylinders in forced and mixed convection flows

In natural convection (high Richardson number Ri), a high Prandtl number (Pr) leads to thinner thermal boundary layers, enlarging the thermal gradient and hence the enhancement of buoyancy effect. In forced convection (low Ri), a high Pr introduces thicker velocity boundary layers. In mixed convection scenarios, where both forced and natural convection are significant, the interaction between Pr and Ri determines the resultant flow pattern and heat transfer characteristic. Three tandem circular cylinders with an identical spacing ratio of 4.0 in both forced and mixed convection flows were numerically investigated by using finite element method. The computations were carried out in the range of Pr = 5–50 and Ri = 0–2 at a low Reynolds number of Re = 150. The results of the squared strain rate and the vorticity shed light on the enstrophy transfer process. Thermal plume structures in the far wake originate from the upper dispersed vortices due to the high superimposed buoyancy at low Pr, while they are suppressed at high Pr. The increase in Pr plays a role as the flow stabilization, while the growth of Ri plays the reverse role. The time-averaged velocity, pressure coefficient, and temperature become more asymmetrical at high Ri. The Nusselt number of the upstream cylinder is approximately equal to the empirical result without the consideration of thermal buoyancy. Due to the thermal buoyancy, the migration of shear layers along the cylinder surface leads to the frequency alteration and harmonic frequency in the drag, lift, and Nusselt coefficients.

Außerhäusliche Mobilität von Personen ab 75 Jahren im ländlichen Raum. Ergebnisse aus einer GPS-Studie

ZusammenfassungHintergrundAußerhäusliche Mobilität, definiert als aktives und passives Bewegen durch außerhäusliche Umwelten, ist eine Ressource für Autonomie, Lebensqualität und Selbstverwirklichung im Alter. Beeinflusst wird diese multifaktoriell, was bisher vor allem im urbanen Raum untersucht wurde. Ziel der Studie ist es, assoziierte Faktoren in einer ländlichen Studienpopulation ab 75 Jahren zu untersuchen.MethodenBaseline-Daten der MOBILE-Studie von 212 Personen ab 75 Jahren erhoben zwischen Juni 2021 und Oktober 2022 gingen in die Analysen ein. Außerhäusliche Mobilität (GPS-basiert an 7 aufeinanderfolgenden Tagen) wurde zeitlich als Time out of Home (TOH) sowie räumlich als Convex Hull (CHull) gemessen. Gemischte Modelle berücksichtigten neben ambulanten Versorgungsparametern persönliche, soziale und umweltbezogene Faktoren sowie Kovariaten wie Alter und Geschlecht.ErgebnisseDie Teilnehmenden der MOBILE-Studie (MAlter 81,5, SD: 4,1, davon 56,1 % weiblich) zeigten eine tägliche außerhäusliche Mobilität von MTOH: 319,3 min; SD: 196,3 und MCHull: 41,3; SD: 132,8. Signifikante Assoziationen wurden für Alter (TOH: ß = −0,039; p < 0,001), soziales Netzwerk (TOH: ß = 0,123; p < 0,001), Zusammenleben (CHull: ß = 0,689; p = 0,035), Gesundheitskompetenz (CHull: ß = 0,077; p = 0,008), Gehwegqualität (ß = 0,366; p = 0,003), Grünflächenanteil (TOH: ß = 0,005; p = 0,047), ambulante Versorgungsinanspruchnahme (TOH: ß = −0,637; p < 0,001, CHull: ß = 1,532; p = 0,025) und aktives Autofahren (TOH: ß = −0,361; p = 0,004) gefunden.DiskussionBereits bekannte multifaktorielle Assoziationen mit objektiv gemessener außerhäuslicher Mobilität konnten im ländlichen Raum bestätigt werden. Neuartig und für Forschung und Praxis relevant ist der signifikante Zusammenhang außerhäuslicher Mobilität mit der Versorgungsinanspruchnahme.

The vacated space of volume/price of the drugs centralized procurement with quantity in secondary and above public hospitals of China

BackgroundIn 2018, the National Centralized Drug Procurement (NCDP) policy has been implemented in 11 provinces, and promoted across the country in 2019. The main feature of the policy is “volume for price”, therefore, it is necessary to measure the price relationship, not only to reduce the price of drugs, reduce the burden of patients' medical costs, but also facilitate pharmaceutical companies to access enough innovation incentives. The aim of this study was to assess the vacated space effect of the drug centralized procurement by national organizations in exchange of price for quantity.MethodsA difference-in-differences (DID) model was employed to analyze the effect of the 4 + 7 pilot drugs centralized purchasing policy on drug sales volume and selected versus clinically substitutable unselected varieties, using observational data from 2018 to 2019. We compared drug procurement data between secondary and above public hospitals in pilot and non-pilot cities throughout China.ResultsThe study showed that the average treatment effect (ATE) of sales in the in-hospital market for the selected supply varieties in centralized purchasing is -0.42, and with a sales volume of 0.49. This indicates a volume-price vacated space of 1.16 ~ 1.17 DDD (defined daily dose)/Yuan, implying that for every 1 defined daily dose (DDD) increase in reported volume, the standardized price decreased by 1.16–1.17 Yuan. The ATE of in-hospital market sales for drugs not selected in centralized procurement shows a decrease of 0.13. This finding highlights the presence of the price linkage effect. The ATE of sales volume is 0.57, indicating a volume-price space of 4.38 ~ 4.39 DDD/Yuan for unselected drugs, approximately 3.75 higher relative to that of the selected ones.ConclusionsThe ratio of the volume-price space of clinically substitutable unselected and selected drugs may serve as direct evidence for evaluating the shift from centralized purchasing of drug varieties to clinically substitutable other ones. To strengthen the volume-based negotiation approach and maximize the effectiveness of centralized purchasing policies, we recommend the strategic implementation of a three-tiered centralized purchasing system, the expansion of drug coverage, and the introduction of relevant constraints and incentives.

Numerical research on the flow and heat transfer characteristics in the immersion jet cooling for servers

Immersion cooling and jet impingement liquid cooling, as two of the significant emerging direct contact liquid cooling methods, have promising prospects for development and application. The two cooling methods are combined and numerical simulation is applied to study the heat transfer performance of the immersion jet-cooled server. The orthogonal method is employed to determine the optimal structural parameters of the immersion jet, and the flow and heat transfer characteristics under different inlet and outlet layouts are investigated. The study shows that the optimal heat dissipation effect and moderate pressure are achieved when the ratio of jet distance (L) to jet pipe diameter (D) is 1.2, and the ratio of jet hole spacing to jet orifice diameter is 11.1. When the inlet and outlet of the cabinet are arranged in a Z-shaped layout, the pressure on the server surface is reduced by 17.1 %–31.6 % compared to a U-shaped layout. When the inlet and outlet of the cabinet are arranged in a Z-shaped manner with the inlet at the bottom and the outlet at the top, the highest heat transfer coefficient is over 24000 W/(m2· K), which is approximately 1.5 times higher than that of other layouts. Through dimensional analysis, a quadratic function was selected to fit the relationship between heat transfer coefficient h, server pressure P and jet ratio (D/L), opening area A; In addition, the criterion relationship of Nu = f (Re, Eu) is fitted according to the simulation data, which provides a theoretical basis for energy saving and consumption reduction in data centers.

Coupling effects of building-vegetation-land on seasonal land surface temperature on street-level: A study from a campus in Beijing

The land surface temperature (LST) of urban streets is significantly influenced by the surrounding urban environment. In the cold areas of northern China, this influence exhibits a seasonal pattern. Currently, in areas with noticeable seasonal variations, the coupling effects of urban elements on the annual stability of street LST remain unclear. This study developed a new metric, Normalized Winter-Summer Land Surface Temperature Difference, to measure the year-round LST stability of campus streets. Three key urban elements affecting street-level LST in winter and summer were identified: building, vegetation, and land. The influencing characteristics for winter and summer LST were quantified and ranked respectively. The study reveals that the green space ratio dominates summer LST, while fraction vegetation coverage, leaf area index and average building height dominate winter LST. We found that morphological characteristics of buildings and vegetation cannot fully explain the impact of the urban physical environment on street-level LST. For winter street LST studies, greater emphasis should be placed on non-morphological characteristics and land. Based on the impact mechanisms and critical thresholds of key features in winter and summer, this study establishes an interpretable spatial classification method. By assigning seasonal weights to influencing features, it provides comprehensive design strategies that consider both winter and summer features to enhance annual LST stability and climate resilience in urban spaces facing extreme meteorological conditions.