Search Results (47)

Objectives: The aim of this study was to determine differences in injury types and frequencies between piston-based and band-based automated chest compression devices in patients with non-traumatic out-of-hospital cardiac arrest (OHCA) at a German cardiac arrest center. Methods: This retrospective single-center study assessed resuscitation-related injuries in OHCA patients using protocol-based early whole-body CT scans at hospital admission. CT scans were reviewed independently by two reviewers blinded to the compression device used. Between May 2015 and September 2021, all patients resuscitated from non-traumatic OHCA, treated with a mechanical chest compression device, and showing stable return of spontaneous circulation (ROSC) until CT examination according to the institutional standard operating procedure for all OHCA patients were included. Patients were categorized by compression device type, and group differences were analyzed using the Chi-square test and Mann–Whitney U test. In addition, patient-level incidences of rib fracture types were calculated, and risk ratios with corresponding 95% confidence intervals were used to compare rib fracture patterns between groups. A p-value of <0.05 was considered statistically significant. Results: Among 71 patients, 32 received band-based and 39 piston-based treatment. Both groups were comparable in resuscitation duration, body constitution, and gender ratio, although the band-based group was older. Thoracic injuries predominated, with rib fractures representing the most frequent injury pattern (64/71, 90.1%). The median number of rib fractures per patient was 10 (IQR 8–12) in the band-based group and 9 (IQR 7–12) in the piston-based group. The band-based group had significantly more liver lacerations (5/32, 15.6% vs. 0/39, 0%; p = 0.01) and displaced rib fractures (117 vs. 87; p = 0.046; patient-level RR = 1.43, 95% CI 1.06–1.93). Conclusions: In this observational study of a CT-based cohort of OHCA patients with stable ROSC, the band-based device was associated with significantly higher frequencies of liver lacerations and displaced rib fractures than the piston-based device. These findings should be interpreted as hypothesis-generating and may support further evaluation of device-specific injury profiles in future studies. Full article

Background: Noninvasive transdermal insulin delivery using ultrasound technology has gained attention for improving the glycemic control of insulin-dependent patients. Methods: Indirect functional comparison and evaluation of insulin dosage, between noninvasive ultrasound-mediated transdermal delivery and needle injection methods, was achieved utilizing in vivo blood glucose measurements of temporary hyperglycemic rabbits. Nine rabbits were divided into three groups: (i) untreated control, (ii) subcutaneous injection and (iii) ultrasound-mediated transdermal delivery. Animals were anesthetized using a combination of ketamine hydrochloride and sodium xylazine to produce temporary hyperglycemic rabbits during the experiments. The rabbits in the control group did not receive insulin, while the animals in the ultrasound group received insulin transdermally for 10 min utilizing a customized single-element piston-shaped ultrasound transducer operated by multi-frequency electrical signals from 100 to 200 kHz. Rabbits in the direct subcutaneous injection group were anesthetized and injected with 0.25 units/kg of insulin. Results: With an initial blood glucose baseline level of 228.7 ± 13.1 (mg/dL) for all rabbits, the in vivo results of control group showed an increase above the baseline by 129.7 ± 27.3 (mg/dL) at the end of the in vivo experimental period (80 min). However, the ultrasound-mediated delivery and subcutaneous injection groups showed noticeable statistically significant percentage reductions in blood glucose levels by 43.9 ± 5.4 and 42.7 ± 6.6, respectively, compared to the control group by the end of the in vivo experiments. Conclusions: In vivo glucose response results confirmed that piston-shaped ultrasound transducers achieved indirectly similar insulin dosage delivery by ultrasound energy for tested animals with no statistically significant differences once compared to the results of the subcutaneous needle injection group. Full article

The objective of this paper is to evaluate the training efficiency of AR-based versus paper-based instruction methods with different levels of task complexity in terms of knowledge retention (i.e., short-term memory and long-term memory). Two maintenance operations were selected (i.e., low-demand (check all seals of the pump housing) and high-demand maintenance tasks (repair a gearbox of the piston pump and check all seals of the gearbox)). Twenty-eight healthy males were recruited and randomly divided into two groups. Each participant performed the maintenance task with assistance (i.e., AR-based or paper-based instruction) and repeated it without instructions twice (30 min apart and then two weeks later). Knowledge retention was measured using the total task completion time without guidance, error number, the number of self-corrected errors (SCEs), and the number of times help was sought from the researcher. The results show that using AR-based instruction enhanced the participants’ performance, especially in the highly demanding task, by reducing task completion time and errors in both short- and long-term retention tasks. Participants who were guided through a paper-based instruction method showed more errors, more instances of seeking help from the researcher, and a longer time to complete the long-term retention task, compared with those guided through the AR-based instruction method. Overall, using AR instruction to guide maintenance workers increased training transfer by 33.61%. Full article

The diesel substitution ratio is a key parameter influencing the combustion characteristics and energy conversion efficiency of hydrogen diesel dual-fuel free-piston engines. This study develops a thermodynamic hydrodynamic coupled model for a dual-fuel free engine to investigate the effects of five substitution ratios (15%, 20%, 25%, 30%, and 35%) on in-cylinder mixture formation, combustion characteristics, and emission performance. The key novelty of this work lies in employing this fully coupled combustion-dynamics model to systematically optimize the hydrogen–diesel substitution ratio, which explicitly captures the critical feedback between combustion and the piston’s unique motion. The cumulative heat release served as the key quantitative metric. The analyzed parameters included the gas mixture fraction, turbulent kinetic energy, flow trajectories, in-cylinder pressure and temperature, combustion reaction rate, unburned equivalent ratio, cumulative heat release and its rate, heat release rate, and emission mass. The results demonstrate that the engine’s overall performance is optimal at a substitution ratio of 25%. At this ratio, a peak volumetric mixture fraction of 0.0088 was achieved with a broad distribution range, indicating significantly improved spatial fuel uniformity. The flow field exhibited organized swirl patterns that enhanced fuel dispersion. The peak in-cylinder pressure reached 7.2 MPa, which was 0.044 MPa higher than that of the 20% group. The combustion temperature remained stable, with a peak value of 1606 K, exceeding the 20% and 30% groups by 7 K and 16 K, respectively. The heat release phase was well-synchronized with the piston motion, ensuring a high proportion of premixed combustion for thorough fuel oxidation. Although nitrogen oxide (NOx) emissions were slightly higher, the reduction in soot was substantially greater than in the 20% group, leading to overall superior performance compared to the other substitution ratios. This study develops a thermodynamic hydrodynamic coupled model for a dual-fuel free-piston engine by leveraging the interaction between piston motion and combustion. This paper presents a novel strategy for optimizing the substitution ratio in a free piston engine via a fully coupled combustion-dynamics model. Full article

Groundwater recharge sources and residence times in the Sulaimani–Warmawa Sub-basin, located in the Kurdistan Region of Iraq, were assessed through an integrated hydrogeological, hydrochemical, and isotopic investigation. The study area, located around Sulaimani City, is characterized by a semi-arid climate with precipitation predominantly occurring during winter and early spring. Hydrochemical results indicate groundwater types ranging from Ca–HCO₃ to Mg–Ca–HCO₃, accompanied by a progressive increase in electrical conductivity along the regional flow path. Stable isotope signatures (δ²H and δ¹⁸O) show that groundwater is primarily recharged by winter precipitation derived from both Eastern Mediterranean and Persian Gulf air masses. Two groundwater groups were identified based on isotopic composition and tritium content: recently recharged groundwater and older groundwater, represented by two samples. Tritium values ranging from 0.8 to 4.9 TU correspond to minimum residence times from less than 10 years to approximately 40 years. Higher tritium concentrations near recharge zones reflect recent infiltration, whereas lower values indicate older groundwater with limited modern recharge. The piston flow model provided the best fit for tritium data, suggesting limited mixing and relatively rapid subsurface flow. Samples with higher salinity likely reflect reduced flushing in low-permeability zones, resulting in elevated dissolved solids. Hydraulic-data-based estimated groundwater flow velocities yielded lower values compared to tritium-based estimates, implying preferential flow in karstified formations. The relatively short groundwater residence times mean there is high vulnerability to contamination, emphasizing the need for careful land-use planning and groundwater protection strategies. Full article

The oil layers in the Dongying Formation offshore oilfield are severely contaminated. The near-wellbore reservoir pore throats are blocked, which seriously affects the development effect. It has become urgent to implement acidizing stimulation measures. However, the target reservoir is deeply buried, has high reservoir pressure, and is highly sensitive. These factors result in high pressure during acidizing operations, a long single-trip time for raising and lowering the tubing string, and high costs. Moreover, acid that is not promptly returned to the surface after acidizing can cause secondary pollution to the reservoir. This work proposes an integrated tubing string to perform reverse displacement and reverse squeeze. With this, acid can be injected into the formation through the annulus between the casing and tubing. The residual acid and its post-acidizing derivative residues are rapidly lifted to the surface by the reciprocating suction action of the return pump. Based on this, the structure and specifications of the acidizing-flowback tubing string are designed through the flow rate analysis method. The tubing string is mainly affected by mechanical effects, including buoyancy, piston effect, flow viscosity effect, helical bending effect, temperature difference effect, and expansion effect. The maximum deformations are 1.4 m, 1.9 m, 0.18 m, 2.7 m, 1.8 m, and 2.5 m, respectively. The total deformation is less than 3 m. Simulation results from three groups of oil wells at different depths indicate that the axial force of the tubing string ranges from 400 to 600 kN. The stress ranges from 260 to 350 MPa, deformation is 1.1–2.4 mm, and the safety factor exceeds 3.0. This can effectively ensure the safety of on-site operations. Based on the actual field conditions, the acidizing-flowback tubing string is evaluated. This verifies the effectiveness of the acidizing-flowback tubing string. This research provides an economical and efficient operation process for acidizing operations in the Dongying Formation offshore oilfield. It achieves the goal of removing reservoir contamination and provides guidance for the unblocking and stimulation of low-permeability and sensitive reservoirs in the middle and deep layers of offshore oilfields. Full article

Background: Diabetes mellitus is associated with worse outcomes after cardiac arrest. Hyperglycemia, diabetes treatments and other long-term sequalae may contribute to this association. We sought to determine the acute effect of diabetes on the return of spontaneous circulation (ROSC) and post-arrest cardiac function in a rat cardiac arrest model. Methods: Eighteen male Wistar rats were utilized, and 12 underwent the induction of type II diabetes for 10 weeks through a high-fat diet and the injection of streptozotocin. The carotid artery flow and femoral arterial pressure were measured. Seven minutes of asphyxial cardiac arrest was induced. An external cardiac compression was performed via an automated piston. Post-ROSC, epinephrine was titrated to a mean arterial pressure (MAP) of 70 mmHg. Data was analyzed using the Mann–Whitney test. The significance was set at p ≤ 0.05. Results: The rate of the ROSC was significantly lower in animals with diabetes, 50% compared to 100% in non-diabetics. Additionally, it took significantly longer to achieve the ROSC in diabetics, p = 0.034. In animals who survived, the cardiac function was reduced, as indicated by an increased epinephrine requirement, p = 0.041, and a decreased cardiac output at the end of the experiment, p = 0.017. The lactate, venous and arterial pressures, heart rate and carotid flow did not differ between groups at 2 h. Conclusions: Diabetes negatively affects the survival from cardiac arrest. Here, the critical difference was the rate of the conversion to a life-sustaining rhythm and the achievement of the ROSC. The post-ROSC cardiac function was depressed in diabetic animals. Interventions targeted at improving defibrillation success may be important in diabetics. Full article

The aim of translucency-enhancing liquids (TEL) is to locally influence the phase composition of zirconia in order to increase its translucency. This study aimed to determine the influence of TEL on 3Y- and 4Y-TZP zirconia concerning roughness, hardness, wear, flexural strength, dynamic stability and fracture force of fixed dental prostheses after thermal cycling and mechanical loading. Two zirconia materials (4Y-TZP; 3Y-TZP-LA, n = 8 per material and test) were investigated with and without prior application of TEL. Two-body wear tests were performed in a pneumatic pin-on-block design (50 N, 120,000 cycles, 1.6 Hz) with steatite balls (r = 1.5 mm) as antagonists. Mean and maximum vertical loss as well as roughness (Ra, Rz) were measured with a 3D laser-scanning microscope (KJ 3D, Keyence, J). Antagonist wear was determined as percent area of the projected antagonist area. Martens hardness (HM; ISO 14577-1) and biaxial flexural strength (BFS; ISO 6872) were investigated. The flexural fatigue limit BFSdyn was determined under cyclic loading in a staircase approach with a piston-on-three-ball-test. Thermal cycling and mechanical loading (TCML: 2 × 3000 × 5 °C/55 °C, 2 min/cycle, H₂O dist., 1.2 × 10⁶ force á 50 N) was performed on four-unit fixed dental prostheses (FDPs) (n = 8 per group) and the fracture force after TCML was determined. Statistics: ANOVA, Bonferroni test, Kaplan–Meier survival, Pearson correlation; α = 0.05. TEL application significantly influences roughness, hardness, biaxial flexural strength, dynamic performance, as well as fracture force after TCML in 3Y-TZP. For 4Y-TZP, a distinct influence of TEL was only identified for BFS. The application of TEL on 3Y- or 4Y-TZP did not affect wear. TEL application has a strong effect on the mechanical properties of 3Y-TZP and minor effects on 4Y-TZP. All effects of the TEL application are of a magnitude that is unlikely to restrict clinical application. Full article

The mechanisms of in-service damage caused to the cylinder units of internal combustion engines (ICE) during their operation are analyzed. Long-term operation under harsh conditions, failure to comply with operating conditions, and breach of design and technology standards were found to be the major reasons for the initiation and propagation of in-service defects. The life of ICE cylinder liners is proposed to be extended by forming regular microreliefs. This represents a promising surface engineering strategy. Axial lines of the regular microrelief’s grooves were considered using analytical dependencies, which helped determine their coordinates and those of their equidistant. The authors simulated the pattern according to which the groove axes of type II regular microrelief could be aligned on the inner surface of the cylinder liner. To this end, a tool with three deforming elements was used. Technical means have been developed to implement this technology on the working surfaces of the liner–piston group’s mating parts. Full article

Molecular modeling calculations for the design and improvement of next-generation additives for motor oils have reached a level that can support and improve experimental results. The regulation of insoluble sludge nanoparticle aggregations within oil and on engine pistons is a critical performance metric for lubricant oil additives. There is a general agreement regarding the mechanism of deposit formation which is attributed to the self-aggregation of nano-sized carbon rich insoluble structures. Dispersants are a primary category of additives employed to inhibit aggregation in lubricant formulations. Along with the base oil, they are crucial in dispersing and stabilizing insoluble particles to manage the formation of deposits. In this study, multiscale modeling methods were used to elucidate molecular mechanism of deposit control via polyisobutylene-bis-succinimide (PIBSI) dispersants by using density functional theory (DFT), molecular dynamics (MD) simulations of cells constructed by statistical sampling of molecular configurations, and coarse-grained (CG) simulations. The aim of this study was to understand the role of different groups such as succinimide, amine center, and two polyisobutylene (PIB) tails in PIBSI dispersants. It was demonstrated that the mechanism of deposit control by the polymer-based PIBSI dispersant can be elucidated through the interactions among various constituents, including hydrogen bonding and hydrophilic–hydrophobic interactions. We showed that sludge type nanoparticle aggregation is mitigated by intercalation of polar amine central groups of dispersant between the nanoparticles followed by the extension of two hydrophobic PIB chains into the oil phase that decreases coalesce further by forming a hydrophobic repulsive layer. Full article

For future internal combustion engines, driven by regenerative fuels, efficiency is more important than ever. One approach to reduce the losses inside the piston cylinder unit (PCU) is to improve the alignment of the liner and the piston. Therefore, a cylinder liner with a free form was developed at the Institute of Technical Combustion (ITV) of the Leibniz University Hannover which compensates radial and linear deformations along the stroke. The layout is based on a FEM simulation. The liner was manufactured by the Institute of Production Engineering and Machine Tools (IFW) of Leibniz University of Hannover with a novel turn-milling process. The liner was investigated on the heavy-duty Floating-Liner engine of ITV with a displacement of 1991 ccm and a bore diameter of 130 mm. The experimental results show improvement in the friction losses over the whole engine map in the range of 9% and up to 17.3% compared to a serial liner. Sealing efficiency could be improved up to 28.8%, depending on the operational point. Overall, the investigation aims for lower fuel consumption which would in result fewer emissions. Full article

One therapeutical alternative in the treatment of functional disorders is the use of printed oral splints. The mechanical properties of these materials are highly essential to their clinical effectiveness, and their performance may vary depending on factors such as cleaning, post-polymerization, or their orientation during construction. The objective of this in vitro investigation is to evaluate the effectiveness of the selected materials in terms of their biaxial flexural strength in relation to the criteria listed above. Splint materials were used in the printing of 720 discs. The printing process was carried out in different orientations in relation to the building platform. Either an automatic or manual cleaning process was performed on the samples. For post-polymerization, either an LED or Xenon light was utilized. A piston-on-three-ball test was used to measure the biaxial flexural strength (BFS) of the materials after they were stored in water for either 24 h or 60 days. The homogeneity of the data was controlled by employing the Levene method, and the differences between the groups were analyzed using the ANOVA and Bonferroni methods. After being stored for twenty-four hours, the mean BFS ranged anywhere from 79 MPa to 157 MPa. Following a period of sixty hours, the BFS exhibited a substantial drop and revealed values that ranged from 72 to 127 MPa. There was no significant difference that could be identified between the materials or between the various cleaning processes. The results of post-polymerization showed that the LED light produced higher means than the Xenon light did. In terms of position, the mean values varied greatly, with 0°’s mean value being 101 MPa, 45°’s mean value being 102 MPa, and 90°’s mean value being 115 MPa. The use of a build orientation of 90° and post-polymerization with LED light resulted in significantly increased biaxial flexural strength. According to this study, this design should be implemented in order to ensure that splint materials have the highest possible strength. Full article

The decarbonization of maritime transport has become a crucial strategy for the adoption of renewable low-carbon fuels (LCFs) (MARPOL 73/78 (Annex VI) and COM (2021) 562-final 2021/0210 (COD)). In 2018, 98% of operated marine diesel engines ran on fossil fuels. The application of LCFs, according to expert assessments (DNV GL), is considered the most effective solution to the decarbonization challenge in the maritime sector. This publication presents methodological proposals related to assessing the reliability of operational diesel engines when transitioning to low- carbon fuels. The proposed methodology implements an interconnected assessment of the combustion cycle parameters and the limiting reliability factors of the thermal load on the most critical components of the cylinder–piston group. The optimization of the combustion cycle parameters for the indicators of energy and the environmental efficiency of low-carbon fuel applications was combined with the evaluation and assurance of permissible values of the thermal load factors on the components to determine the overall reliability of the engine. Thus, the possibility of overload and engine failures was already eliminated at the retrofitting design stage. The algorithm for the parametric analysis was grounded in the practical application of established α-formulae for the heat exchange intensity, such as those of the Central Diesel Engine Research Institute and G. Woschni. This approach was combined with modeling the combustion cycle parameters by employing statistical or single-zone mathematical models such as IMPULS and AVL BOOST. The α-formulae for low carbon fuels were verified based on the thermal balance data. The structure of the solutions for the effectiveness of the practical implementation of this methodology was comprehensively oriented towards diesel “families”, as exemplified by the models 15/15 (p_mi = 1.2, 1.4, and 1.6 MPa). The long-term goal of the obtained results in the structure of comprehensive decarbonization research was to assess the factors of the reliable operation of characteristic groups of medium-speed (350–1000 rpm) and high-speed (1000–2100 rpm) marine engines for reliable operation in the medium term on ammonia. Full article

Preferential flow is widely developed in varieties of voids (such as macropores and fissures) in loess areas, affecting slope hydrology and stability and even leading to geological disasters. However, the model of seepage evolution with dynamic preferential flow is not clear, which obstructs the disclosure of the mechanism of landslides induced by the preferential flow. This study aimed to capture the seepage and occurrence status of water in loess voids, explain the variability characteristics of the loess pore structure, and reveal the seepage evolution model of dynamic preferential flow. Preferential infiltration experiments were conducted by combining X-ray computed tomography (X-ray CT) nondestructive detection with contrast techniques under dynamic seepage conditions. Three-dimensional (3D) visualized reconstruction, digital image correlation (DIC), image processing, and quantitative analyses were performed in AVIZO 2019.1, including two-dimensional (2D) and 3D characteristics of preferential flow distribution and macropore changing, dynamic variation of the porosity, pore number, volume, dip angle, and connectivity. Results showed that (1) preferential flow exists under saturated and unsaturated conditions in loess with strong uniformity and anisotropy; (2) preferential flow not only migrates into existing connected macropores, but also connects the original isolated pores into channels and forms larger percolation groups of contrast medium under the gradually increased high pressure; (3) the seepage develops with the evolution model of ‘preferential flow–piston flow–preferential piston mixture flow–piston flow’ in the dynamic process. The new insights into the characteristics of the seepage evolution in undisturbed loess under dynamic preferential flow will enrich the understanding of loess seepage and provided an important reference for future research on the slope instability of the loess induced by preferential flow. Full article

The current problems associated with the maintenance of hard coal longwall mining depend on the application or use of extraction technologies. In order to make the best use of these technologies, a new approach based on simulation studies is necessary. This paper aims to develop a mathematical model for the powered roof support’s operation. The three groups of professionals involved in the testing of the roof support were involved in the work on changing the hydraulic system of the powered roof support stand. These professionals were powered roof support’s designers, researchers and users. The research subject was the development of a mathematical model as a starting point for conducting simulations. The model is based on d’Alembert’s principle and the equation of the balance of flow rates. Based on the developed model, it is possible to determine the pressure in the space under the piston of the hydraulic prop. The results obtained in the simulations are the basic assumptions for the development of a prototype that would solve the current problems in the hydraulic systems of powered roof supports. The adopted research methodology assumed the development of a mathematical model, simulation in the MATLAB environment and verification of the model on a test stand. The obtained results of simulation tests based on the developed mathematical model were confirmed in bench tests. Simulation and bench tests determined the correctness of the assumptions made for the development of the prototype model. Based on the analysis of the results, the nature of the work of the future prototype has been predetermined. The next stage will be the testing of the prototype, which is to be included in the hydraulic system of the prop of powered roof support in the future. The model mentioned before is the baseline model, and it will be modified depending on the application of the future design in real conditions. Simulation studies of powered roof support will allow the structure that is used currently to be optimised, so as to adapt it to increasingly difficult working conditions. Full article