Consecutive Operations Research Articles

Robotic TAPP vs. endoscopic TEP for inguinal hernia repair: a register-based analysis of 129 consecutive robotic operations

Robotic TAPP vs. endoscopic TEP for inguinal hernia repair: a register-based analysis of 129 consecutive robotic operations

Sustainable biodiesel production from waste cooking oil using highly effective CaO/hectorite catalyst: Process optimization, kinetic and thermodynamic studies.

Biodiesel production through trans-esterification reaction requires design of efficient solid catalyst for sustainable use. This study reports a newly prepared CaO/hectorite catalyst for trans-esterification reaction of waste cooking oil (WCO). The catalyst material was prepared by wet impregnation method. Material characterization was done using various advanced instrumentation techniques such as FTIR, 1H/13C NMR, XRD NMR, BET, TGA and FE-SEM. The result of FE-SEM characterization shows the surface heterogeneity in catalytic material. Further, an enhanced BET surface area (142.3 m2 g−1) of CaO/hectorite indicated suitability of material for catalytic applications. Kissinger-Akahira-Sonuse (KAS) computational model was used to evaluate thermodynamic parameters. Response surface methodology (RSM) – Box Behnken model/ANOVA was used to draw the 3D-surface plots and 2D-contour plots for estimation of maximum biodiesel yield. The catalytic trans-esterification shows high biodiesel production (95 %) in an optimized reaction condition (10.5:1 methanol:oil molar ratio, 3.5 % catalyst loading, 57.5 °C reaction temperature and 105 min). It was found that the biodiesel produced from WCO has fuel characteristics complied with that of B100. The catalyst could be reused up to seven consecutive cycles operation resulting biodiesel production (>80 % yield) thus indicating future commercial applications in a sustainable manner.

Prognostic Significance of the Controlling Nutritional Status (CONUT) Score in Patients with Muscle-Invasive Bladder Cancer after Radical Cystectomy.

To assess the impact of the The Controlling Nutritional Status (CONUT) score, an indicator of nutritional status, on the survival and prognosis after radical cystectomy. The medical records of patients who underwent consecutive radical cystectomy operations with the diagnosis of muscle-invasive bladder cancer at our clinic were retrospectively examined. The patients were separated into two groups based on the cut-off CONUT score which was derived using the receiver operating characteristic (ROC) curve. The group with a CONUT score ≥ 3 was categorized as high CONUT, whereas the group with a CONUT score <3 was categorized as low CONUT. The groups were compaired according to oncological outcomes and survival risk factors. Cancer-specific survival (CSS) and overall survival (OS) were statistically significantly lower in the High CONUT group compared to the Low CONUT group (p<0.001, p=0.024, respectively). Age (HR: 1.02, 95% CI: 1.006-1.04, p=0.011) and CONUT score (HR: 3.92, 95% CI: 2.66-5.77, p<0.001) were revealed to be independent prognostic variables in the multivariate analysis for OS. The CONUT score was found to be an independent predictor of survival in patients with muscle-invasive bladder cancer in this study.

EDI&amp;S SO03 Replacing Single-use Chloraprep with Low Carbon Cost-effective Surgical Skin Preparation: A QI Project for Sustainability in Surgery

Abstract Background Operating theatre waste accounts for approximately 50% of all hospital waste produced in the NHS [1] and two-thirds of carbon contributions come from single-use items [2]. With a major goal of the NHS being net-zero, surgeons have a collective responsibility for reducing the carbon footprint through eliminating single-use equipment and plastic waste such as Chloraprep wands. The aim of this quality improvement project was to introduce the use of chlorhexidine solution poured into reusable gallipots and applied using reusable sponge-holders into local practice, which is more environmentally friendly, significantly cheaper and is the first-line skin preparation recommended by NICE [3]. Method Chloraprep use in consecutive operations performed by the trust in a month before and after the intervention was retrospectively collected and categorised based on specialties. The intervention was a series of local oral presentations, leaflets and posters to highlight the benefits of chlorhexidine solution over Chloraprep. The change in percentage of Chloraprep use in all cases completed in 1 month pre- and post-intervention was retrospectively collected and analysed. Further qualitative data was obtained through pre- and post-intervention surveys. Results There was a reduction in use of Chloraprep across all specialties targeted by the intervention, with 27% of cases pre-intervention and 24% of cases post-intervention using Chloraprep. The highest percentage reduction was seen by the local upper gastrointestinal surgery team (37%). The percentage reductions in the cases using Chloraprep 10 days post intervention were general surgery 9%, upper GI 3%, colorectal 1% and vascular 6%. The pre- and post-intervention surveys also showed a decrease in Chloraprep use from 94.1% to 80% and corresponding increased use of swabs and antiseptic solution. 100% of the responders agreed with using the sustainable option. Conclusion The educational intervention has proven to be effective in achieving the aims of this project. Critical analysis of the literature has shown no difference in surgical site infection rates between the two options [2]. However, there is a need for high quality trials that directly compare the clinical effectiveness of both methods of application. We hope to encourage surgeons and theatre staff to opt out of using Chloraprep and consider the use of swabs dipped in chlorhexidine alcohol solution. Thus, we recommend the re-usable low carbon low-cost alternative method and encourage efforts to promote sustainability in surgery.

Repair of the Bulbospongiosus Muscle to Suspend the Penis to the Pubic Bones in Proximal Hypospadias

BackgroundIn proximal hypospadias, ventral curvature is invariable and most have penoscrotal transposition, and we observed that the base of the penis (BOP) was located on the inferior aspect of the pubic bones in those, in contrast to the location of the BOP at the anterior end in normal penises. We also observed an unfused bulbospongiosus muscle (BSM) at surgery in those. The aim was to assess the impact of repairing the unfused BSM or transection and straightening of the urethral plate at the first operation on the low BOP. MethodAll consecutive proximal hypospadias operations from January 2021 to August 2023 that had a low BOP were retrospectively studied. At the first operation, some had urethral plate transection only, with no BSM repair. Some had BSM repair with or without plate transection. The BOP position was reassessed post-intervention. ResultsThirty-three cases of proximal hypospadias with low BOP were studied. At the first operation, as the key distinguishing step, 18 had BSM repair and 15 urethral plate transections. BOP shifted to the anterior end of the pubic bones in all 18 patients following BSM repair but showed no change in the 15 without BSM repair (p<0.01). Subsequent BSM repair, during the second stage, normalized BOP in those 15. Normalising the BOP corrected penoscrotal transposition because the anterior end of the scrotum was at the anterior end of the pubic bones. ConclusionRepairing BSM is essential for normalising the BOP, which results in a normal penoscrotal relationship and normal anterior penile projection. Level of evidenceIV

Technique and Expected Benefit of Intraoperative Perfusion Imaging of Peripheral Nerves.

Peripheral nerve surgery, particularly in cases of nerve compression syndrome (NCS), necessitates a comprehensive evaluation of intraneural blood flow, as localized reductions in nerve perfusion are integral to the etiopathogenesis of such conditions. Although nerve perfusion is currently guided by morphologic characteristics, this assessment is subjective and prone to bias. Intraoperative fluorescence-assisted perfusion imaging with indocyanine green (ICG) is an established tool in flap and lymphatic surgery to objectively assess perfusion intraoperatively. However, only a few unspecific applications of ICG in peripheral nerve surgery have been published so far. In this study, we performed intraoperative perfusion imaging using ICG in 16 consecutive operations within the peripheral nervous system, including microsurgical reconstructions after obstetric brachial plexus injury, decompression for NCS, and vascularized ulnar nerve interposition transfers. Our findings show the utility of ICG in delineating healthy perfusion borders at proximal and distal stump levels after neuroma resection, and we demonstrate a correlation between histological findings and these clinically observed perfusion patterns. In NCS cases, we demonstrate that ICG imaging is effective in highlighting reduced perfusion predecompression and improved perfusion postdecompression. Additionally, ICG proved valuable for assessing perfusion of free vascularized nerve grafts. Intraoperative ICG perfusion imaging is a valuable tool during surgery of the peripheral nervous system, providing insights into the etiopathogenesis of NCS and aiding in the visualization of perfusion. This study underscores the potential of ICG in nerve surgery and its applicability for improving surgical outcomes and advancing our understanding of peripheral nerve pathologies.

Mid-spatial frequency reduction via zero-depth of cut rapid-feed passes in face-turning

The single point diamond turning process (SPDT) is used widely in creating optical grade mirror surfaces on several engineering materials ranging from polymers, and metals, to brittle materials such as silicon and germanium. In visual optic mirror applications, mid-spatial frequency (MSF) errors generated during the SPDT process interfere with the visible spectrum of light thereby affecting the image quality. To overcome these errors, a post-processing operation of polishing the optical mirrors is required. The post-processing step not only increases the complexity of the manufacturing process but also leads to minor geometrical form changes in the mirror which affects performance. To avoid post-processing and minimize MSFs formed during turning- a novel method to modify the toolpath during the machining process has been proposed in this paper. The suggested toolpath strategy comprises two consecutive operations: i) employing variable low feed rates with the specified depth of cut (DoC) and ii) executing rapid traverse rates with zero depth of cut for a predetermined number of passes. The effectiveness of the proposed strategy is tested by carrying out facing experiments in a micro-precision CNC lathe. The power spectral density (PSD) content of the machined surface is then analyzed to check for any improvement in the frequency characteristics. The results show that the frequency errors generated by the toolpath in normal turning operations can be minimized, distributing the resulting PSD peak over a wide range of spatial frequencies. From the PSD plots, it is observed that there is a decrease of 77% and 85.82% in the peak intensity values when compared with surfaces machined at constant feedrates of 150 μm/rev and 200 μm/rev respectively. This method can be applied to nanoprecision SPDT machines to improve the surface quality and to eliminate the MSF errors of the visual optical grade mirrors without the need for post-processing.

Primary and revision myringoplasty in children: Long-term outcome and analysis of the factors influencing the results

ObjectiveAssess the long-term outcome of pediatric myringoplasty. MethodsTympanoplasty type I, myringoplasty, was performed on 85 children (91 consecutive operations, 74 primary and 17 revisions) under 16 years of age. The perforations were sequela either to acute or chronic inflammatory middle ear disease. Medial grafting technique was employed with temporalis fascia. Adenoidectomy was performed earlier on all but five children. The preoperative observation period exceeded one year for all patients. The mean follow-up was 5.4 (SD 3.6) years. ResultsThe long-term graft take rate was 84% for primary myringoplasty, and 53% for revision operations. The re-perforations were associated with postoperative discharge, subtotal or total perforation and revision surgery. In the cohort, sixty ears (66%) were completely healthy (intact tympanic membrane in normal position without adhesions and with good mobility) after follow-up. Spontaneous healing took place in 37% after re-perforation. The preoperative ventilation tube treatment did not affect the outcome and there were no differences between age groups. Preoperative sonotubometry or Valsalva test results did not correlate with outcome. Four ears needed a ventilation tube during the follow-up due to poor ventilation. The mean pure tone thresholds improved significantly after operation. ConclusionsMyringoplasty in children is a reliable procedure without age restrictions. One year of preoperative observation excludes most unstable ears, and high tendency of spontaneous healing after re-perforation suggests the need for a lengthy follow-up before revision surgery.

Cost Analysis of Pelvic Exenteration Surgery for Advanced Pelvic Malignancy

BackgroundPelvic exenteration (PE) is a radical procedure involving multi-visceral resection for locally advanced pelvic malignancies. Such radical surgery is associated with prolonged operating theater time and hospital stay, as well as a substantial risk of postoperative complications, and therefore significant financial cost. This study aimed to comprehensively detail the inpatient cost of PE at a specialist center in the Australian public sector.MethodsA retrospective costing review of consecutive PE operations at Royal Prince Alfred Hospital in Sydney between March 2014 and June 2022 was performed. Clinical data were extracted from a prospectively maintained database, and in-hospital costing data were provided by the hospital Performance Unit. All statistical analyses were performed using SPSS.ResultsPelvic exenteration was performed for 461 patients, of whom 283 (61 %) had primary or recurrent rectal cancer, 160 (35 %) had primary or recurrent non-rectal cancer, and 18 (4 %) had a benign indication. The median admission cost was $108,259.4 ($86,620.8–$144,429.3) (Australian dollars [AUD]), with the highest costs for staffing followed by the operating room. Overall, admission costs were higher for complete PE (p < 0.001), PE combined with cytoreductive surgery (CRS) (p < 0.001), and older patients (p = 0.006).DiscussionThe total admission cost for patients undergoing PE reflects the complexity of the procedure and the multidisciplinary requirement. Patients of advanced age undergoing complete PE and PE combined with CRS incurred greater costs, but the requirement of a sacrectomy, vertical rectus abdominal flap reconstruction, major nerve or vascular excision, or repair were not associated with higher overall cost in the multivariate analysis.

Novel Trephine for Descemet Membrane Endothelial Keratoplasty Surgery Improves Surgical Preparation Time and Graft Quality: Pilot Data From the "Number 7" Endothelial Keratoplasty Trephine.

To report the safety and efficacy of a novel asymmetric marking trephine for Descemet membrane endothelial keratoplasty (DMEK) tissue preparation. The trephine design incorporates optimized curves to distribute mechanical forces and minimize the risk of tears without loss of total endothelial cell volume transplanted compared with a standard 8.00 mm circular transplant. A retrospective case series of 40 consecutive DMEK operations comparing 20 cases using the "Number 7" trephine against 20 using a modified shark fin technique as standard. Patient and donor characteristics, tissue preparation time and complications, total surgical time, intraoperative and postoperative complications, and endothelial cell counts at 3 months postsurgery are reported. DMEK tissue preparation was significantly faster using the "Number 7" trephine (5.4 vs. 7.6 minutes, P = 0.008). Further, fewer complications arose during tissue preparation (0 vs. 2 complications) despite the faster preparation time. Total surgical time was similar between techniques; however, time spent manipulating the graft was reduced (5.1 vs. 6.8 minutes, P = 0.007) primarily because of the lower tissue preparation complications. Fewer postoperative complications were observed (1 vs. 3, of which 1 in the standard technique group requiring a redo-DMEK), again due to the reduced tissue preparation complications. The 3-month endothelial cell count was comparable between techniques (P > 0.05). Use of the "Number 7" trephine led to faster and safer DMEK tissue preparation, which in turn reduced graft manipulation times and postoperative complications without compromising total endothelial cell volume transplanted. This novel device is ideal for use by surgeons who prepare their own DMEK tissue and within tissue banks who provide prestripped and preloaded DMEK tissue.

ThP7.17 - Improving completeness of operative notes for laparoscopic appendicectomy

Abstract Aim This study aimed to compare the quality of laparoscopic appendicectomy operation notes in the emergency setting to 'Get It Right First Time' (GIRFT) guidelines. To evaluate the effect of the teaching session and operative note checklist in improving the completion rate of operation notes for laparoscopic appendicectomy. Method Retrospective analysis of 19 consecutive operation notes of patients undergoing emergency laparoscopic appendicectomy. Prospective data was then collected on 15 consecutive appendicectomy operation notes post-intervention. 34 recommendations based on GIRFT recommendations 'Best practice for laparoscopic appendicectomy documentation' were used to audit laparoscopic appendicectomy operation notes. Documentation was reviewed by two independent reviewers and scores were given based on GIRFT recommendations. Student's T-test was used to calculate the significance of overall scores and Chi-Squared to calculate the difference between individual categories. Results Mean completeness of operation notes improved from the first cycle (58.5%) to the second cycle (85.5%, P&amp;lt;0.001). There was a significant improvement in documentation of patient positioning (P=0.001), skin preparation (0.035), diagnostic findings (P&amp;lt;0.001), health of caecum (P&amp;lt;0.036), extraction port (P=0.01) and follow-up plan (P=0.03). Conclusion There were many domains of the GIRFT recommendations not addressed prior to this audit. Teaching sessions and checklist distribution lead to a significant improvement in overall completeness of the operation note. Movement towards digitised templates should be made to further comply with guidelines.

Investigation of the efficacy of graphite-sulfur iron tailing composite catalysts for activation of peroxydisulfate for rhodamine B degradation.

Herein, a novel graphite/sulfur iron tailing composite was applied as a peroxydisulfate (PDS) activator for rhodamine B (RhB) degradation in the water. The superior catalytic efficiency of graphite/sulfur iron tailing was achieved through radical (SO4•- and •OH) and non-radical (1O2) processes according to the radical quenching experiments and electron paramagnetic resonance analysis. The carbonyl group and Fe species were the main active sites on the surface of graphite/sulfur iron tailing, which was demonstrated by combining Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and reaction kinetic experiments, and a possible degradation mechanism was also proposed. Overall, activated with 0.30g/L of C-1, PDS achieved a 94.8% removal rate for RhB and maintained a removal rate of over 85% even after five consecutive operation cycles, and this study will benefit the application of iron/carbon composite materials in practical water treatment.

Intraoperative monitoring of visual evoked potentials: experience of 240 operations

Background. Intraoperative monitoring (IOM) of visual evoked potentials (VEPs) is used to inform surgeons about impacts on the visual system in order to prevent iatrogenic visual impairment. The VEP monitoring use become widespread only in the last decade; nowadays, there is no generally accepted methodology for its implementation, and the effectiveness of VEP monitoring and the factors determining it have not been sufficiently studied.Aim. The aim of the study was to investigate the factors influencing the VEP monitoring feasibility and effectiveness.Materials and methods. Data from 240 consecutive neurosurgical operations performed using VEP monitoring were retrospectively reviewed. IOM data (registration parameters, presence and type of VEP changes), patient characteristics (gender and age, tumor type and location, presence of preoperative visual dysfunctions), anesthesia parameters and postoperative changes in vision were studied. Statistical analysis was performed using χ2 and Mann–Whitney tests.Results. VEPs were obtained in 91.3 % of eyes with completely or partially preserved vision. The main factors reducing the chances to record VEPs successfully are preoperative visual disorders and the use of inhalation anesthesia. A personalized approach to the selection of reference electrodes and frequency filtering parameters makes it possible to reduce the number of averagings required for VEP recording and accelerate informing surgeons. With successful monitoring 59.1 % of eyes had no noticeable VEP changes; 5.8 % of eyes had signs of intraoperative improvement; 35.1 % had signs of deterioration. Among the last category, 60.7 % of eyes had full VEPs recovery afterwards. After surgery, new visual disorders were detected in 2.6 % of eyes without signs of intraoperative deterioration, in 6.7 % – with temporary deterioration, and in 19.3 % – with signs of deterioration persisted until IOM is finished. Assessing the sensitivity and specificity of VEP monitoring is hampered by the possibility of complications in the early postoperative period and IOM influence on the course and results of the operation. The proportion of total resections was maximal when VEP monitoring was successful. In the subgroup without preoperative visual impairments, the alarms during monitoring were associated with decrease in proportion of total resections proportion due to increase in proportion of subtotal resections.Conclusion. VEP monitoring with a personalized approach allows effective monitoring of visual functions preservation during neurosurgical operations.

Linear Time Train Contraction Minor Labeling for Railway Line Capacity Analysis

AbstractWhen no more than one train is feasibly contained in the separation headway times of two other trains, a triangular gap problem-based method is used to compute the consumed capacity in linear time. This is a strong condition limiting its applicability, while real-world operations often feature mixed traffic of various speeds, creating more complex structures beyond the characterization of a triangular gap. In this paper, we attempt to investigate the multi-train gap scenario and provide a general solution to the railway timetable structure and capacity analysis problem. Given a timetable, we use an incidence graph, the so-called train contraction minor, for representing the consecutive train operations and show that a longest path for spanning the compressed timetable is any path in a graph induced by some topological subsequence of trains that connects the predefined vertices in the train contraction minor. By vector-valued vertex labeling of this minor, we acquire an efficient algorithm that computes the consumed capacity of the timetable. Our algorithm runs in O(mn) time, where m and n are the number of trains and stations, respectively, and is free from the limitation and outperforms the near-linear time policy iteration implementation in the max-plus system of train operations. A toy example and a real-world case study demonstrate the effectiveness and computational performance of the proposed method. The proposed method based on train contraction minor contributes to the railway operations community by promoting the efficient computation of railway line capacity into linear time.

Chaos based image encryption scheme to secure sensitive multimedia content in cloud storage

Cloud computing offers a variety of on-demand services to users and has gained significant prominence in the contemporary era. The security of information stored in cloud data centers has become a central concern, especially for sensitive data like medical images, videos, and multimedia content that require heightened protection when stored in data centers. Cloud users have a responsibility to ensure the security of their data through strategic measures. Focusing on maintaining the privacy of images stored in the cloud, this research introduces an innovative image encryption technique that is based on a modified Skew Tent chaotic map. The suggested modification to the chaotic map includes combining the Skew Tent map with both the sine trigonometric function and perturbation technology. This results in enhanced randomness, more intricate dynamical behavior, a broader chaotic range, and increased sensitivity to initial values in contrast to alternative chaotic maps. The incorporation of this adapted map into a stepwise procedure, involving two rounds of permutation followed by diffusion, effectively accomplishes image data encryption for cloud storage systems. These consecutive operations collectively enhance the encryption method’s randomness and robustness. Through simulations conducted using Cloudsim, the cipher-image exhibits a uniform distribution and achieves a commendable information entropy score of 7.996749. The encryption algorithm significantly reduces correlation coefficients from 1 in the original image to 0 in the encrypted image, while maintaining NPCR (Number of Pixel Change Rate) and UACI (Unified Average Changing Intensity) values within the critical range. Additionally, both theoretical analysis and practical evaluations confirm the algorithm’s resilience against exhaustive, occlusion, and classical attacks. Moreover, extending this encryption framework to video data, a novel video encryption approach is proposed.

Rare earth oxide Y2O3 modified g-C3N4 for efficient photocatalytic hydrogen production: photocatalytic performance and electron transfer channels

This work used a one-step calcination process to prepare g-C3N4 composites with varying Y2O3 loading. XRD, TEM, and XPS verified the structure and morphology of the composite photocatalyst, and its photoelectrochemical and hydrogen production performance were studied. According to the experimental results, it is found that the composite structure between Y2O3 and g-C3N4 effectively suppresses the photoelectron–hole complex and enhances the photocatalytic hydrogen production properties of g-C3N4. Under the irradiation of a 300 W xenon lamp, YCN-3 had superior photocatalytic hydrogen generation performance, achieving a rate of 1079.61 μmol g−1 h−1, which was 2.3 times greater than that of g-C3N4 in its unmodified state. After three consecutive photocatalytic operations, satisfactory stability and reusability were obtained. Finally, the possibility of a mechanism for the photocatalytic charge transfer pathway is discussed, which provides an effective way for g-C3N4 photocatalytic hydrogen production.

Prevention of Adhesions after Bone Fracture Using a Carboxymethylcellulose and Polyethylene Oxide Composite Gel in Dogs.

The formation of adhesions is a common complication following traumatic injuries and surgical procedures, often resulting in pain, stiffness, and loss of function. This study aimed to evaluate the feasibility and safety of using a composite material comprising of carboxymethylcellulose (CMC), polyethylene oxide (PEO), and calcium chloride, for preventing adhesions between muscle and bone during the healing stage, as well as its effect on the bone healing process. Ten healthy purpose-bred laboratory Beagle dogs were randomly subjected to two consecutive operations with a 6-month interval, alternating between left and right forelimbs. On the left forelimb an osteotomy at the ulna was performed, while on the right forelimb the same procedure was supplemented by the application of the anti-adhesion agent in the osteotomy site prior to closure. Clinical, diagnostic imaging, macroscopic, and histological evaluations were performed at various time points. The results showed no significant differences in surgical site perimeter (p = 0.558), lameness (p = 0.227), and radiographic bone healing (p = 0.379) between the two groups. However, the macroscopic (p = 0.006) and histological assessments revealed significantly lower adhesion scores (p = 0.0049) and better healing (p = 0.0102) in the group that received the anti-adhesion agent. These findings suggest that the CMC/PEO composite material is a safe and potentially effective intervention for preventing post-traumatic and post-surgical adhesions in canine patients without compromising bone healing. Further research is warranted to fully characterize the clinical benefits of this approach.

Twinning, slip and size effect of phase-transforming ferroelectric nanopillars

Ferroelectric materials are widely used in energy applications due to their field-driven multiferroic properties. The stress-induced phase transformation plays an important role in the functionality over repeated and consecutive operation cycles, especially at the micro/nanoscales. Here we report a systematic in-situ uniaxial compression tests on cuboidal Barium titanate (BaTiO3) nanopillars with size varying from 100 nm to 3000 nm, by which we explore the stress-induced transformation and its interplay with plastic deformation. We confirm the superelasticity achieved in pillars by martensitic phase transformation from tetragonal to orthorhombic. There exists a critical size, 330 nm, for the yield stress. Above 330 nm, martensitic phase transformation aids slip along the plane with a low Schmid factor, in turn, the pseudo-compatible twins form within the shear band. The scaling exponent of size-dependent yield strength is found to be exactly 1. For nanopillars smaller than 330 nm, no twins form, only slips with large Schmid factors are activated, and size effect vanishes. All pillars with sizes from 100 nm to 300 nm achieve the theoretical yield limit around 9 GPa. Our experimental results uncover the interplay between twins and slips in BaTiO3 nanopillars, which pave the way for the optimization of microstructure design of ferroelectric materials for microelectronic applications at small scales.

Capacity Degradation Assessment of Lithium-Ion Battery Considering Coupling Effects of Calendar and Cycling Aging

Capacity degradation of lithium-ion batteries largely determines the cost, performance and environmental impact of various products such as renewable energy production systems, portable electronics, and electric vehicles. Degradation assessment is thus of great importance for prognostic and health management of batteries, which ensures a stable production and operation. There are typically two leading sources contributing to the degradation of a lithium-ion battery, namely, cycling aging during charge/discharge cycles and calendar aging during idle states. However, most existing studies on degradation assessment either only consider a single source or ignore the coupling of these two sources, which makes the evaluation inefficient. A common observation in practice is that a battery tends to degrade faster when it experiences charge/discharge cycles continuously for a longer time. To capture this feature, this paper introduces the concept of the cumulative uninterrupted cycling duration (CUCD), which is defined as the consecutive operation duration since a battery ends the idle state. The CUCD can also help to model the coupling between the calendar and cycling aging. This paper then proposes to model the drift rate of cycling aging as a function of the CUCD and the functional form is determined with the monotonic spline. We estimate the model parameters by maximizing the likelihood function. Hypothesis testings toward the significance of the coupling between two aging sources and the monotonicity of the drift rate function under cycling aging are also provided. The effectiveness and the superiority of the model are validated using numerical and real case studies. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This study aims to characterize the degradation of lithium-ion battery simultaneously considering calendar and cycling agings and the coupling effect. Unlike previous research that only supplied experimental results to qualitatively illustrate the existence of the coupling effect between these two aging sources, this study provides procedures to quantitatively test the significance of such an effect. In addition, previous research ignored the coupling effect in the degradation modeling as it is difficult to capture, this study propose the concept of CUCD to characterize it. The CUCD is also introduced as a stress factor for cycling aging, which is based on the fact that a battery will degrade faster when it experiences charge/discharge cycle continuously for a longer time. Hypothesis testing is also provided to illustrate this monotonicity. To deal with another challenge that the expert knowledge of the functional form between cycling aging and CUCD is unavailable except for the monotonicity, a nonparametric method with the shape-restricted spline is adapted. The estimation procedures for the model parameters are also presented.

Influence of consecutive tamping operations on failures of ballast bed and tamping machine

Repeated tamping operations can improve the maintenance effort for ballasted tracks, but can also cause damage to tamper and ballast. Therefore, this study investigated the failure mechanism of a ballast bed and tamping machine for consecutive tamping operations. A highly accurate and stable method for testing the dynamic characteristics of a tamper was designed, and the macroscopic influence of the number of tamping operations was analyzed experimentally. The results indicated that when the tamping operation was repeated, the impact force was smaller and the squeezing distance was shortened. In addition, the mechanical state of the ballast bed improved when the tamping operation was repeated within three times. A ballasted track-tamping machine model was established using the DEM-MFBD coupling approach, and the microscopic influence of the number of tamping operations was analyzed numerically. The results showed that excessive tamping significantly increased the stress on the tamper and the dynamic response of ballast. The optimal number of tamping operations is recommended to be less than four.