Amount Of Injection Research Articles

Experimental observation of turbulent jet ignition of pre-chamber with scavenging system for carbon dioxide diluted mixtures

The exhaust gas recirculation (EGR) method can suppress knock and improve the thermal efficiency of engines. But it will also deteriorate the combustion stability and engine power. Turbulent jet ignition (TJI) is a reliable ignition resource for improving ignition stability and burning rate. However, the residual productions in the pre-chamber will worsen the performance of the TJI. To this end, a self-designed pre-chamber with a scavenging system has been proposed. In this study, the ignition process and flame propagation phenomena under different EGR dilution ratios for H2/N2/O2 and CH4/N2/O2 mixtures were conducted in a constant-volume combustion chamber. The results suggested that the increase in EGR dilution weakens the influence of cellular instability and causes buoyancy instability, the latter of which could be mitigated by the passive TJI method. For the passive TJI mode, the exit time of the hot jet was delayed, and the turbulent flame speed decreased with the increase of EGR dilution ratio. Four ignition phenomena, namely jet re-ignition, flame buoyancy, re-ignition failure, and misfire, were distinctly identified. However, EGR tolerance cannot be extended by passive pre-chambers. Therefore, the pre-chamber with a scavenging system that can effectively extend the lean combustion tolerance with EGR dilution compared to SI and passive TJI was proposed. The effects of air and fuel injection quantities on ignition and flame propagation were investigated. The flame propagation velocity was positively related to the air injection mass, whereas an optimum fuel mass was required to achieve fast flame propagation. The EGR limit based on dual injections in the pre-chamber was obviously extended. Moreover, under near EGR tolerance conditions, a leaner fuel injection in the pre-chamber was required to realize successful ignition in the main chamber, as strong turbulence could cause high heat transfer loss with the cool unburnt mixture and suppress the occurrence of re-ignition.

Abstract 13969: Iterative Changes in Alcohol Septal Ablation at the Medical University of South Carolina: A Single-Center Experience

Introduction: Alcohol septal ablation (ASA) is an effective procedure to treat medically refractory hypertrophic obstructive cardiomyopathy (HOCM). Several modifications have been made to the procedure since its inception. We seek to assess the changes in the procedure and outcomes over the past 20 years Methods: We retrospectively analyzed 845 ASA procedures performed from January 2000 to February 2022 using an internally maintained database. These procedures were then split into three groups, with procedures occurring from 2000-2004 (Cohort 1), 2005-2011 (Cohort 2), and 2006-2022 (Cohort 3). Patient demographics, echocardiographic measurements, and procedural data were recorded. Results: Average patient age was 53.06 (143:161 M:F, 52.96% female), 59.71 (125:140, 52.83% female), and 63.86 years (99:177, 64.13% female) in Cohorts 1, 2, 3 respectively. The peak resting left ventricular outflow tract (LVOT) gradient was significantly higher in Cohort 2 and 3 (69.893 mmHg, 72.218 mmHg) versus Cohort 1 (57.32 mmHg, p<0.0001). The number of septal arteries injected increased slightly, but the total amount of alcohol injected decreased, thereby implying a reduced amount of alcohol injection per septal artery. The overall infarct size did not show a significant difference between the three Cohorts (peak total creatine kinase, p=0.0871). The average length of hospital stay decreased and pacemaker incidence continued to be <10%. There were no procedural deaths since 2008. See Figure 1. Conclusions: ASA has become increasingly safer over the past twenty years at MUSC with maintained efficacy and zero procedural mortality since 2008. Improved patient selection, transition to a bi-radial approach, contrast echocardiographic imaging, slower alcohol injection rate, reduced alcohol volume per septal artery and increased operator experience are responsible for the improvement.

Tunneling injection to trap-limited space-charge conduction for metal-insulator junction

For a biased trap-filled insulator, the current transport is governed by the physics of charge injection from the metallic electrode and also the trap-limited space-charge conduction in the insulator. With a Schottky barrier at the interface of the metal-insulator junction, charge tunneling injection from a metal into the trap-filled insulator is different from an Ohmic contact. At sufficiently large amount of charge injection at high voltages, the charge transport becomes the trap-limited space-charge conduction. In this paper, we develop a consistent model to calculate the correct IV characteristics up to a breakdown field strength of 1 V/nm. Using this model, we analyze the transport characteristic of three different metal-insulator junctions (ITO/PPV, Al/h-BN, and Al/ZrO2) and identify the conduction mechanisms over a wide range of the applied voltage, insulator's thickness, and properties of the traps. Our findings report the interplay between various transport mechanisms, which is useful to characterize the correct current transport for novel insulators such as organic semiconductors, 2D insulators, and metal-oxide electronics.

Impact of Dilation and Irreversible Compaction on Underground Hydrogen Storage in Depleted Hydrocarbon Reservoirs

Underground hydrogen gas storage (UHS) at depleted hydrocarbon reservoirs may balance energy production/consumption during seasons by utilizing the capability of hydrogen gas. The geomechanical behavior of the reservoir rock during UHS operation cycles is an effective parameter of the overall quality and quantity of this operation. This study investigated the impact of rock geomechanical behavior on the quality and quantity of UHS operation performance in a depleted oil reservoir. Three geomechanical behaviors, namely, elastic deformation, irreversible compaction of rock, and dilation–recompaction, form the basis of this study. We numerically investigated how these cases affect wellbore injectability, hydrogen recovery, production of in situ reservoir fluids, and the number of hydrogen injection/production wells. Based on the results of this study, the performance of wells during the injection of hydrogen in the dilation case was better than in other cases. After 10 cycles, 87% of the designed cumulative volume of hydrogen was injected into the reservoir. Though the irreversible compaction case injected the least cumulative hydrogen, it generated the highest hydrogen recovery during annual cycles and at the end of UHS operation (93%). The production of nonhydrogen fluids is known as a problem in UHS operations in depleted hydrocarbon reservoirs. After 10 cycles of hydrogen injection and production and 3 years of prolonged production, the dilation case produced less water and oil overall than other cases. Also, fewer wells are required to achieve the designed injection amount in the dilation case compared to base and irreversible compaction cases. Therefore, the costs associated with hydrogen injection and production wells in reservoirs with geomechanical dilation behavior are lower.

Next-Cycle Optimal Dilute Combustion Control via Online Learning of Cycle-to-Cycle Variability Using Kernel Density Estimators

Dilute combustion using exhaust gas recirculation (EGR) presents a cost-effective method for increasing the efficiency of spark-ignition (SI) engines. However, the maximum amount of EGR that can be used at a given condition is limited by a rapid increment of cycle-to-cycle variability (CCV). This study describes a methodology to design a model-based stochastic optimal controller to adjust the cycle-to-cycle fuel injection quantity in order to reduce CCV and further extend the dilute limit. Given the complexity and chaotic nature of combustion events, the controller was enhanced with online learning in order to identify the statistical properties of combustion efficiency, which are needed to generate predictions for next-cycle events. This study showed that a kernel density estimator (KDE) can be used to learn the combustion properties in real time and can be incorporated into the feedback policy in order to calculate the optimal control command. Experimental results suggested that the dilute limit can be extended from 18.5% to 21% EGR fraction at an operating condition relevant for highway cruising. Additionally, the proposed controller can achieve a large CCV reduction with less fuel enrichment compared to previous methods, overall contributing to an increase in 0.2% indicated fuel conversion efficiency.

Simulation of In-cylinder Mixture Formation in SIDI Diesel Engine

In this paper, the in-cylinder mixture formation process of a two-stroke spark-ignition direct-injection(SIDI) diesel engine is simulated and analyzed. The effects of the shape of the combustion chamber, the injection time and the initial temperature of the engine on the mixing process and the performance of the SIDI diesel engine are analyzed. The simulation results show that the offset combustor can obviously improve the fuel economy of the SIDI diesel engine. Under the premise of constant fuel injection quantity, there is an optimal fuel injection time to make the power performance and economy of the SIDI diesel engine optimal. Increasing the initial temperature is beneficial to the atomization of diesel oil and the formation of diesel mixture in cylinder. The results will guide the engineering design of SIDI diesel engine.

Experimental investigation on pneumatic pre-fracturing grouting in low-permeability soil

Effective injection of grout into low-permeability soil is difficult in the process of soil reinforcement. To address practical problems, this study proposes a pneumatic pre-fracturing grouting method comprising model experiments to analyze the initiation and propagation of fractures, earth pressure, soil displacement, and the characteristics of grouting consolidation. In the pneumatic fracturing experiment, the fractures exhibited larger effective radii under gradual pneumatic loading compared with those created due to instant loading, providing more initial channels for grout diffusion. Meanwhile, the higher the pneumatic pressure, the greater the residual height of the fractures after pneumatic fracturing, yielding a predominant condition for grout injection. Compared with conventional grouting, the effective injection amount, effective diffusion radius, and height of grout consolidation of pneumatic pre-fracturing grouting were much larger. The results prove the feasibility and superiority of pneumatic pre-fracturing grouting in low-permeability soils.

Mathematical and experimental validation of an approach for simultaneously determining the binding parameters of two drugs to a receptor

Quantifying drug-protein interactions has a pivotal role in both early phase drug development and clinical processes. Diverse affinity chromatographic methods like nonlinear chromatography can realize such quantification, however, their throughputs are challenged due to the loading of a single ligand during each run. This work derivatized a new equation for simultaneously determining the bindings of two ligands to a protein relying on assumption that the retention factors of the ligands are dependent on their injection amounts. Experimental validation of the derivatization was performed on an immobilized endothelin A receptor (ETAR) column taking ambrisentan, bosentan, and macitentan as injecting solutes. All three ligands presented a decrease in retention times along with increasing moles of injection when they were singly injected into the column. Likewise, negative relationships between the retentions and the injection amounts were observed when co-injection of ambrisentan/bosentan or bosentan/macitentan was performed, thus confirming the assumption of the derivatization. The association constants of ambrisentan, bosentan, and macitentan binding to ETAR were (1.42 ± 0.78)×104, (1.81 ± 0.22)×104, and (1.71 ± 0.41)×104 L/mol when each of them was singly loaded on the column. Such data displayed insignificant changes in four weeks thereby providing a proof of good stability of the column during the period. Co-injections of the two ligand pairs resulted in the association constants of (2.97 ± 0.13)×104 for ambrisentan, (2.51 ± 0.87)×104 for bosentan, and (2.88 ± 0.34)×104 L/mol for macitentan. These results were in good agreement with the calculation when each of the ligands was injected alone into the column and demonstrated little differences from the data by nonlinear chromatography. Owning to the simultaneous analysis of two ligands, the throughput of the proposed method was twofold higher than the typical assays including frontal analysis, zonal elution, and nonlinear chromatography. It is possible to become an alternative for rapid analysis of drug-protein interaction.

Structure Design and Working Characteristics Analysis of Direct-Drive Giant Magnetostrictive Injector.

At present, the research of electronically controlled injectors is mostly limited to the non-direct drive structure. Although the research on the direct drive structure is involved, it mostly stays in the conceptual machine or simulation stage. In this paper, based on the direct-drive structure, the giant magnetostrictive material is used as the energy conversion material, the prototype of the direct-drive giant magnetostrictive fuel injector is designed and manufactured, and the experimental test system and AMESim simulation model are built. By means of experiment and simulation, the injection characteristics of Giant magnetostrictive injector (GMI) are tested. It is found that the minimum single injection quantity of GMI is 5.9 mm3 under the condition of 30 MPa rail pressure, which shows high injection accuracy. The experimental results are in good agreement with the simulation results under different driving pulse widths and voltages. When the driving pulse width is not less than 650 µs, the relative errors are all less than 5%, which verifies the effectiveness of the simulation model. The injection performance of GMI is analyzed. The results show that this injector has a stable injection performance, fast response speed (the shortest injection pulse width is about 200 µs), and the injection process can be completed five times in 5 ms.

Anomalous strain-dependent charge density in honeycomb borophene

The electronic properties of honeycomb borophene under strain were investigated using first principles. The biaxial tensile strain was found to alter the interlayer interaction between the substrate layer and the sample layer, manifested as controlled by strain in a commensurate contact state intralayer and interlayer coupling strength. In addition, honeycomb borophene was found to have an anomalous strain-dependent charge density. We explain that this charge density fluctuation is determined by the electron-deficient nature of borophene itself and the change in the amount of electron injection into the borophene layer under strain. This study provides new insights into the changes in the interaction between two-dimensional materials and substrate layers under strain.

Performance characteristics of a two-stroke low speed engine applying ammonia/diesel dual direct injection strategy

Ammonia has been attracting widely interests among the world because of the property of carbon-free energy resource. As the alternative and renewable fuel of internal combustion engine, its application is expected to comply with the GHG (greenhouse gas) reducing goal of traditional power equipment. However, the defects of low combustion efficiency, high pollutant emissions and poor power performance are restricting the promotion of ammonia fuel. Experimental validation and evaluation of Ammonia/Diesel dual direct injection mode of two-stroke low speed engine were conducted in the current study based on the concept of diesel Jet Controlled Compression Ignition (JCCI). The engine performance and emission characteristics were discussed under the cases of various ammonia injection quantity, timing and different diesel injection timing conditions. It reveals that the injection timing of diesel, which is responsible for the ignition of liquid phase ammonia spray, can regulate the engine combustion phase precisely. The combustion duration of ammonia is accelerated by the ignition of high energy diesel flame, which results in the improvement of indicated thermal efficiency (ITE). Moreover, the worrying fuel type NOx emission, which is mainly produced by the ammonia combustion, is reduced by the reasonable arrangement of injection timings of diesel and ammonia.

Investigating a deterministic yet computationally cheap combustion parameter for model predictive control of a CNG-diesel RCCI engine

This study investigates the changing deterministic features of the cycle-resolved location of maximum pressure and its correlation with combustion phasing for dynamical transitions in the combustion of a CNG-Diesel RCCI engine. The investigation is performed using nonlinear dynamical and chaotic methods such as return maps, recurrence, and cross recurrence plots. The experiments are performed on a single-cylinder automotive engine operated in RCCI mode with the aid of the development ECU. The experiments are conducted by running the engine at a fixed engine speed of 1500 rpm and a load of 3 bar BMEP. Diesel fuel is injected directly into the cylinder by following a double injection strategy using an equal amount of fuel in both the pilot and main injections. The effect of the start of main injection timing of diesel on combustion dynamics is investigated at two different masses of CNG. The predominance of deterministic periodic features is discovered in the cycle-resolved dynamics of the engine combustion during the RCCI regime. Results show that with advancement in diesel injection timing, the mode of combustion shifts from conventional dual fuel to RCCI, and this shift is coupled to the onset of noisy periodic-2 bifurcations., The periodic-2 behavior even transforms to periodic-3 and 4 with an increasing advancement in diesel injection timing for engines operating with a higher CNG mass. For most of the operating conditions, the deterministic features in the location of maximum pressure are comparable with that of combustion phasing. Recurrence and cross recurrence plots-based methodology advocates for the existence of strong correlations or at least a phase synchronization between the location of maximum pressure and combustion phasing when the engine operates in the RCCI regime, irrespective of diesel injection timing and amount of port-injected CNG fuel. The presence of similar deterministic features in the location of maximum pressure and combustion phasing and a strong relationship between these two at intermediate diesel injection timings in the RCCI regime for both the CNG masses makes this regime most suitable for using the location of maximum pressure as a feedback/controlled parameter for model predictive control of the engine.

Preparation and Optimization of Modified Asphalt by Profile Control Parameters at Lamadian Oilfield

The Lamadian oilfield has entered the stage of strong water cut after natural energy development and conventional water flooding development. The use of asphalt binder for profile control can not only adjust the contradiction between layers, expand the swept volume, but also improve the oil displacement efficiency. The field test has achieved certain results. The main oil layer in the Lamadian oilfield has a strong oil layer thickness and serious vertical and plane heterogeneity. After years of water injection development and polymer injection development, most oilfields have entered a period of strong water cut. In the test, it is found that the effect of different well layers is very different, the effect is unstable, and the reason is unclear. Therefore, it is necessary to carry out research on the adaptability and parameter optimization of profile control of asphalt binder through laboratory experiments. In this paper, the asphalt binder provided on site are modified and the dispersion effect of modified asphalt binder is studied, and the concentration of suspending agent is optimized. The artificial cemented core structure and injection method are improved to solve the problem of aggregated asphalt binder on the end face during injection. The displacement profile control experiment was carried out with artificial cores, and the matching relationship between the injected particle size of the asphalt binder and the permeability was determined, and the optimal injection amount was optimized for cores with different permeabilities. The research results show that adding a KCl (potassium chloride solution) solution with a concentration of 2% as a dispersant can exert a better dispersing effect on the asphalt binder. Through the plugging rate experiments of three types of asphalt binder, the profile control effect is determined as the best when the particle size of the asphalt binder is 0.06–0.1 mm. According to the experimental results, the experimental research on the injection concentration and profile control radius of the profile control agent system was carried out. Finally, it was determined that the injection concentration of 3500 mg/L and the profile control radius of 1/3–1/2 of the well spacing were the optimal injection parameters. The field application of a profile control agent provides experimental basis.

Development of a new RH desulphurisation process with powder injection through the nozzles of up snorkel

ABSTRACT A novel desulphurisation process in a RH (Ruhstahl-Hausen Process) degasser (RH aside spray technique) has been proposed, plant trials have been carried out and the ruling factors have been analysed. The results indicate that the new desulphurisation process can not only obtain high desulphurisation degree of above 80% but also avoid unfavorable fluorite powder flux. The sulfur in the molten steel can be removed from 40∼80 ppm to less than 10∼20 ppm . The injection amount of the powder flux is about 5 kg per ton steel. The desulphurisation effect is perfect and stable, which is suitable for ultra-low-carbon electrical steel deep desulphurisation in RH degasser. Enlargement of the interfacial reaction area is considered to accelerate the desulphurisation process. Further study is recommended.

Effect of parameters on retention behavior of ovalbumin and immunoglobulin E in asymmetrical flow field‐flow fractionation

Asymmetrical flow field-flow fractionation is a rising useful technique to separate and characterize macromolecules. Elution behaviors of allergen protein ovalbumin and immunoglobulin E were studied here. Effects of flow rates, kinds of carrier solutions, and injection amounts were investigated in the desire to experiment and verify the effect of every factor and to validate asymmetrical flow field-flow fractionation theory. Results suggested that cross-flow is the most important factor among all the factors that have been studied. Too-low focus flow (0.5 ml/min) and outflow (0.4 ml/min) are harmful for protein separation and characterization. Smaller size ovalbumin (with a monomer is 11.4 nm) is more prone to be influenced compared with the bigger analyte immunoglobulin E (with a monomer diameter is 32.1 nm) by flow rates. The adopted types of carrier fluids did not change the retention behavior of the two proteins. Still, protein aggregation and membrane adsorption should be paid more attention to under different carrier fluids.

Use of Hydrogen-Rich Gas in Blast Furnace Ironmaking of V-bearing Titanomagnetite: Mass and Energy Balance Calculations.

The iron and steel industry is a major CO2 emitter and an important subject for the implementation of carbon emission reduction goals and tasks. Due to the complex ore composition and low iron grade, vanadium–bearing titanomagnetite smelting in a blast furnace consumes more coke and emits more carbon than in an ordinary blast furnace. Injecting hydrogen–rich gas into blast furnace can not only partially replace coke, but also reduce the carbon emission. Based on the whole furnace and zonal energy and mass balance of blast furnace, the operation window of the blast furnace smelting vanadium–bearing titanomagnetite is established in this study on the premise that the thermal state of the blast furnace is basically unchanged (raceway adiabatic flame temperature and top gas temperature). The effects of different injection amounts of hydrogen–rich gases (shale gas, coke oven gas, and hydrogen) on raceway adiabatic flame temperature and top gas temperature, and the influence of blast temperature and preheating temperature of hydrogen–rich gases on operation window are calculated and analyzed. This study provides a certain theoretical reference for the follow–up practice of hydrogen–rich smelting of vanadium–bearing titanomagnetite in blast furnace.

Analysis of the causes of residual back pain in the early and late stages after percutaneous vertebral augmentation

To explore the influencing factors of the residual back pain in patient with osteoporotic vertebral compression fractures(OVCFs) in the early and late stages after percutaneous vertebral augmentation(PVA), and analyze the correlation between these factors and the residual back pain after PVA. From March 2018 to December 2019, 312 patients with OVCFs who treated with PVA were collected. According to the inclusion and exclusion criteria, a total of 240 patients were included in this retrospective study. There were 59 males and 181 females, aged from 50 to 95 years old with an average of (76.11±10.72) years old, and 50 cases of fractures located in the thoracic region (T5-T10), 159 cases in the thoracolumbar region (T11-L2), and 31 cases in the lumbar region (L3 and below). The first day after PVA was regarded as the early postoperative period, and the seventh day was regarded as the late postoperative period. According to the visual analogue scale (VAS), the patients were divided into 4 groups:early postoperative pain relief group(group A, VAS≤4 scores), there were 121 patients, including 29 males and 92 females, aged from 50 to 90 years with an average of (75.71±11.00) years;early postoperative pain relief was not an obvious group (group B, VAS >4 scores), there were 119 patients, including 30 males and 89 females, aged from 53 to 95 years with an average of (76.51±10.46) years; late postoperative pain relief group (group C, VAS≤ 4 scores), there were 172 patients, including 42 males and 130 females, aged from 50 to 95 years with an average of (76.20±10.68) years; late postoperative pain relief was not obvious group (group D, VAS>4 scores), there were 68 patients, including 17 males and 51 females, aged from 53 to 94 years old with an average of (75.88±10.91) years old. The age, gender, bone mineral density(BMD), injured vertebral segment, preoperative thoracolumbar fascial condition, surgical methods, single or bilateral puncture, the amount of bone cement injection, anterior vertebral height recovery rate and central vertebral height recovery rate in the 4 groups were analyzed by univariate analysis. The statistically significant factors were put into a Logistic regression to analyze the correlation between these factors and residual back pain after PVA. Univariate analysis showed that the residual back pain in the early stage after PVA was correlated with BMD, preoperative thoracolumbar fascial injury, single or bilateral puncture, the amount of bone cement injection, anterior vertebral height recovery rate and central vertebral height recovery rate(P<0.05). The residual back pain in the late postoperative period was related to BMD, injured vertebral segment, surgical methods, the amount of bone cement injection, anterior vertebral height recovery rate and central vertebral height recovery rate(P<0.05). Multivariate Logistic regression analysis showed that thoracolumbar fascial injury(OR=4.938, P=0.001), single or bilateral puncture(OR=5.073, P=0.002) were positively correlated with the residual back pain in the early stage after PVA(B>0), which were risk factors;the BMD (OR=0.211, P=0.000) and anterior vertebral height recovery rate (OR=0.866, P=0.001) were negatively correlated with the residual back pain in the early stage after PVA(B<0), which were protective factors. In the late stage after PVA, the BMD(OR=0.448, P=0.003), the amount of bone cement injection (OR=0.648, P=0.004) and anterior vertebral height recovery rate (OR=0.820, P=0.000) were negatively correlated with residual back pain(B<0), which were protective factors. The decrease of BMD, injury of the thoracolumbar fascia, single or bilateral puncture, poor recovery of anterior vertebral height and insufficient injection of bone cement are closely related to the occurrence of residual back pain after PVA, which affect the relief of residual back pain in the early and late postoperative periods.

Analytical Method Development and Validation of Ondansetron and Telmisartan in Tablet Dosage Form by RP-UPLC Method

The objective of the present analysis was the improvement of easy, exact as well as reproducible and precise verifies reversed phase Liquid Chromatography with High Performance [UPLC] assays for Telmisartan and Ondansetron. The chromatographic splitting up was done on Acuity UPLC BEH C 18 (50×2.1mm and1.7µm) column with gradient elution. The injection amount was 1µl and also the detection was performed at 214 nm by utilizing photo diode array detector. The evolved as well as a validated UPLC way of Telmisartan and Ondansetron in tablet dosage styles based on ICH tips was precise and accurate, therefore it may be utilized for equally evaluation scientific studies of medications. This process demonstrated the repeatability of outcomes with regard to accuracy, scientific studies, robustness, and then program - suitability problems.&#x0D; Keywords: UPLC, Ondansetron, chromatography, Telmisartan, accuracy, robustness

Risk factors of adjacent vertebral refracture after percutaneous vertebroplasty for osteoporotic vertebral compression fractures in super-old patients

To analyze the risk factors for refracture of adjacent vertebrae after percutaneous vertebroplasty (PVP) in super-old patients with osteoporotic vertebral compression fractures(OVCFs). A retrospective analysis was performed on 40 patients(age≥90 years) with OVCFs who underwent PVP between June 2012 and June 2019. There were 7 males and 33 females, age from 90 to 101 years old with an average of (94.6±1.6) years. Patients were divided into two groups according to whether adjacent vertebral refracture occurred after PVP. Among them, 20 patients occurred refracture after PVP (refracture group) and 20 patients did not occur it(control group). The general information, radiological data and pelvic parameters of the two groups were collected. The items included age, gender, body mass index (BMI), fracture site and bone mineral density(BMD) T-value, fracture to operation time, compression degree of injured vertebra, recovery degree of anterior edge of injured vertebra, bone cement injection amount, bone cement leakage, pelvic index(PI), pelvic tilt angle (PT), sacral angle(SS), et al. Factors that may be related to refracture were included in the single-factor study, and multivariate Logistic regression analysis was performed on the risk factors with statistical significance in the single-factor analysis to further clarify the independent risk factors for refracture of adjacent vertebral bodies after PVP. There were no significant differences in age, gender, fracture site, fracture to operation time, compression degree of injured vertebra and recovery degree of anterior edge of injured vertebra between two groups (P>0.05). There were significant differences in BMI, BMD T-value, bone cement injection amount and bone cement leakage rate between two groups(P<0.05). The PI and PT values of the refracture group were higher than those of the control group(P<0.05). There was no significant difference in SS between two groups (P>0.05). Multivariate Logistic regression analysis showed that decreased BMD T-value, bone cement leakage, increased PT and PI values increased the risk of recurrence of adjacent vertebral fractures in OVCFs (P<0.05). There are many risk factors for the recurrence of adjacent vertebral fractures in super-old patients with OVCFs. Patients with high PI and PT values may be one of the risk factors.

Fast space charge packet characteristics within low-density polyethylene affected by epitaxial crystallization

The formation of space charge packet increases the maximum electric field within HVDC polymeric cable insulation. However, the influence of epitaxial crystallization on transient characteristics of space charge packet behavior in polyethylene (LDPE) under high temperature is still unrevealed. Therefore, polytetrafluoroethylene (PTFE), isotactic polypropylene (iPP), and glass (G) were adopted as the substrates to prepare LDPE samples with different epitaxial crystallization, denoted as PE-PTFE, PE-iPP, and PE-G respectively, for the measurement of space charge packet at 60 °C under −125 kV/mm. The experimental results show that space charge packets with both positive and negative polarity occurred immediately in LDPE samples after polarization, whose mobility and rising rate of electric field are at least 10 times higher than that at normal temperature. The injection amount of positive space charge packet arranged as PE-PTFE > PE-G > PE-iPP. According to the epitaxial crystallization characteristics of parallel (PE-PTFE), crossed (PE-iPP), and random (PE-G) arrangement of molecular chain, as well as the feature that hole migration is tend to be affected by molecular chain arrangement, the epitaxial crystallization of PE-iPP is contributed to the transport within inter-molecules, resulting in the difficulty of the appearance of positive space charge packet. The obtained results in this paper are important to have deep understanding for space charge behavior within cable insulation.