bluuebunny/crossref_metadata_2025 huggingface dataset:
Validating the textural characteristics of soft fish‐based paste through International Dysphagia Diet Standardisation Initiative recommended tests
Authors: Xie Yisha , Zhao Wenyu , Yu Wanying , Lin Xiaoyu , Tao Shuaifei , Prakash Sangeeta , Dong Xiuping
Published: December 2020

One in every twelve people worldwide suffers from dysphagia that affects the swallowing mechanism and some patients require a special texture‐modified food for their sustenance. Fish is a great source of nutrients and proteins, however the commercially dysphagia diet made from fish is limited. This study investigated the textural characteristics of a soft fish paste produced from steamed grass carp fillet with different the water addition, grinding cycles and ratio of starch with the mixture of steamed fillet and water, following International Dysphagia Diet Standardisation Initiative (IDDSI) guidelines and other instruments. The water addition and particle size affected the physical properties, and the starch had a certain masking effect on fishy odor. The mixture of steamed fish fillets and water (91:9 wt/wt) was ground in a colloid mill for 3 cycles. The fish paste was then sterilized by adding sugar, salt, and starch in the mixture (ratios of 0.5:100, 0.5:100, and 0.6:100, wt/wt, respectively) and mixing well. The paste conformed to Level 4‐pureed and extremely thick of IDDSI framework. The fish paste product had a light fishy odor that was acceptable to sensory specialists.
Assessment of pyloric sphincter distensibility and pressure in patients with diabetic gastroparesis
Authors: Desprez Charlotte , Chambaz Marion , Melchior Chloé , Basile Paul , Prevost Gaetan , Jacques Jérémie , Leroi Anne‐Marie , Gourcerol Guillaume
Published: December 2020

Background

Recent studies have shown that pyloric distensibility is altered in 30–50% of gastroparetic patients but the number of diabetic patients included in prior reports has been small. The aim of the present study was to assess pyloric sphincter measurements in diabetic patients with gastroparesis and to determine whether diabetes characteristics were correlated to pyloric disfunction.

Methods

Pyloric distensibility and pressure were measured using EndoFLIP® system in 46 patients with diabetic gastroparesis (DGP) and compared with 21 healthy volunteers (HV), and 33 patients with idiopathic gastroparesis (IGP). Altered pyloric distensibility was defined as the measurement below 10 mm2/mmHg at 40 ml of inflation. In diabetic patients, blood glucose, glycated hemoglobin, duration, complications, and treatments were collected.

Key Results

Mean pyloric distensibility at 40 ml of inflation was lower in DGP and IGP groups with, respectively, 10.8 ± 0.9 mm2/mmHg and 14.8 ± 2.2 mm2/mmHg in comparison with the HV group (25.2 ± 2.3 mm2/mmHg; p < 0.005). 56.5% of patients had a decreased pyloric distensibility in the DGP group, 51.5% of patients in the IGP group, and 10% of patients in the HV group. No correlation was found between pyloric sphincter measurements and diabetes characteristics, including blood glucose, glycated hemoglobin, diabetes mellitus type, neuropathy, or GLP1 agonists intake.

Conclusion and Interferences

Pyloric sphincter distensibility and pressure were altered both in diabetic and idiopathic gastroparesis. Pyloric sphincter distensibility was not correlated to diabetes parameters.
Using Satellite Rod Technique in Patients with Severe Kyphoscoliosis Undergoing Three‐Column Osteotomy: A Minimum of 2 Years' Follow‐up
Authors: Hu Zongshan , Liu Dun , Zhu Zezhang , Qiu Yong , Liu Zhen
Published: December 2020

Objective

To introduce the satellite rod technique utilized in severe spinal deformity after three‐column osteotomy (3CO) and to evaluate the radiographic and clinical outcomes at 2‐year follow‐up, further discussing its utilization in this particular cohort.

Methods

A total of 32 (19 females and 13 males) with an average age of 32.9 ± 18.3 years from December 2012 to March 2016 were retrospectively reviewed. Radiographic measurements were performed on standing full‐spine anteroposterior and lateral radiographs preoperatively, postoperatively, and at last follow‐up. The coronal parameters including Cobb angle and distance between C7 plumb line and center sacral vertical line (C7PL‐CSVL), as well as the sagittal parameters including global kyphosis (GK) and sagittal vertical axis (SVA) were measured at three time points. The Scoliosis Research Society‐22 questionnaire (SRS‐22) was fulfilled preoperatively and at each follow‐up. Paired t test would be used to determine whether there was a significant difference between time points.

Results

A total of 32 patients were enrolled in this study with mean age of 32.9 ± 18.3 (range, 12 to 66) years old. Twenty patients underwent pedicle subluxation osteotomy (PSO) and 12 patients underwent vertebral column resection (VCR). The pathogenesis of this cohort included neuromuscular scoliosis (11 cases), congenital kyphoscoliosis (seven with hemivertebrae and five with segmentation failure), degenerative spinal deformity (five cases), and thoracolumbar tuberculosis with angular kyphosis (four cases). The post‐operative Cobb angle decreased significantly from 49.1° ± 28.0° to 19.0° ± 16.7° with a correction rate of 65.2% ± 21.8%. At final follow‐up, the average Cobb angle was 19.4° ± 16.9° and no obvious loss of correction was found. The preoperative, postoperative, and last follow‐up C7PL‐CSVL were 23.9 ± 14.5 mm, 15.7 ± 11.1 mm, and 12.1 ± 7.4 mm, respectively. Significant postoperative improvement was attained while there was no change observed at last follow‐up. Postoperative GK significantly improved from 73.8° ± 28.1° to 23.2° ± 11.7° with the correction rate of 66.0% ± 17.9%. SVA decreased significantly from 42.9 ± 33.9 mm to 24.1 ± 21.1 mm. The average GK and SVA at final follow‐up were 22.7° ± 10.1° and 23.5 ± 21.1 mm, respectively and no obvious loss of correction was observed of them during follow‐up. In addition, no change or loss of motor or somatosensory evoked potential occurred during surgery. During the follow‐up, two malposition screws and one rod breakage were found.

Conclusion

The satellite rod used in patients with severe kyphoscoliosis undergoing 3CO could yield favorable radiological and clinical outcomes. With the utilization of this technique, the coronal and sagittal balance could be well‐maintained during follow‐up.
Evaluation of Percutaneous Transforaminal Endoscopic Discectomy in the Treatment of Lumbar Disc Herniation: A Retrospective Study
Authors: Chen Qiyong , Zhang Zhongmin , Liu Boling , Liu Shaoqiang
Published: December 2020

Objective

The objective of the present study was to evaluate the safety and efficacy of percutaneous transforaminal endoscopic discectomy (PTED) and open fenestration discectomy (OFD) in the treatment of lumbar disc herniation (LDH).

Methods

Patients in our hospital with LDH who received PTED (n = 71) and OFD (n = 39) from 2013 to 2014 were retrospectively studied. Patient information, including age, gender, visual analogue scale (VAS) score for low back pain and leg pain, body weight, height, Oswestry disability index (ODI), Japanese Orthopedic Association (JOA), and recurrence, was collected. The patients in the two groups were followed up for an average of 63 months after surgery.

Results

A total of 136 patients completed the operation and 110 patients were followed up completely. There was no significant difference in baseline data between the two groups (P > 0.05). The postoperative low back pain, leg pain, ODI, and JOA of the two groups were better than those preoperatively (P < 0.05). One week after surgery, the recovery of PTED patients was better than that of OFD. The ODI score of the PTED group was lower than that of the OFD group (10 [8, 12] vs 14 [11, 16]; P < 0.05), the waist VAS score of the PTED group was lower than that of the OFD group (2 [2, 3] vs 3 [2, 4]; P < 0.05), the leg VAS score of the PTED group was lower than that of the OFD group (1 [0,1] vs 1 [1, 2]; P < 0.05), while the JOA score of the PTED group was higher than that of OFD group [19(16, 20) vs 12(10, 17); P < 0.05]. There were no significant differences in ODI, JOA, waist and leg VAS scores between the two groups at 1 month after surgery and at subsequent follow‐up (P > 0.05). At the end of the follow up, 89.7% (35/39) of patients in the OFD group had excellent improvement in the JOA score, and 88.7% (63/71) of patients in the PTED group had an excellent improvement. There was no significant difference between the two (P > 0.05). There was also no significant difference in the recurrence rate between the two groups [(5/71) vs (3/39); P > 0.05]. [Correction added on 05 March 2021, after first online publication: “3/29” was amended to “3/39” in the preceding sentence.]

Conclusion

Both PTED and OFD can achieve good mid‐term efficacy in the treatment of LDH but PTED has certain advantages, including the small incision, a shorter hospital stay, and quicker, earlier recovery. However, prospective randomized controlled studies with a larger sample size are needed.
Isolated Meniscal Ramp Lesion Without Obvious Anterior Cruicate Ligament Rupture
Authors: Jiang Jun , Ni Lei , Chen Jian
Published: December 2020

Objectives

The purpose of the present paper was to study isolated meniscal ramp lesions without obvious ACL rupture. Their biomechanical mechanisms were analyzed and their clinical characteristics were reviewed. The clinical effects of an all‐inside horizontal mattress suture for isolated ramp lesions were evaluated.

Materials and Methods

Twenty isolated meniscal ramp lesion patients without obvious ACL rupture from 2015 to 2017 were retrospectively reviewed. Preoperative MRI showed intact ACL and signs of ramp lesions. These isolated ramp lesions were arthroscopically confirmed and repaired through an all‐inside horizontal mattress suturing method. MRI was performed 3 months postoperatively to assess isolated ramp lesion healing. The Tegner–Lysholm score and the visual analog scale score were recorded preoperatively and at 2 years postoperatively. The Wilcoxon rank sum test was performed to determine statistical significance.

Results

Arthroscopic exploration confirmed isolated ramp lesions and longitudinal ACL splits or degeneration without obvious ACL rupture. MRI 3 months postoperatively showed healing of the isolated ramp lesions. At 2 years postoperatively, the VAS scores were significantly decreased and the Tegner–Lysholm scores were significantly increased. Knee function, without pain, was restored in all patients, including walking, climing and descending stairs, and squatting.

Conclusion

Isolated meniscal ramp lesions without obvious ACL rupture may exist because of ACL longitudinal splits or degeneration and can be repaired through anterolateral and anteromedial portals with an all‐inside horizontal‐mattress suturing method.
Successful liver transplantation in hyperornithinemia‐hyperammonemia‐homocitrullinuria syndrome: Case report
Authors: De Bruyne Pauline , Verloo Patrick , Van Hove Johan L. K. , de Hemptinne Bernard , Vande Velde Saskia , Van Winckel Myriam , Van Biervliet Stephanie , De Bruyne Ruth
Published: December 2020

Background

HHH syndrome is a rare autosomal recessive disorder of the urea cycle, caused by a deficient mitochondrial ornithine transporter. We report the first successful liver transplantation in HHH syndrome performed in a seven‐year‐old boy. The patient presented at 4 weeks of age with hyperammonemic coma. The plasma amino acid profile was suggestive of HHH syndrome, and the diagnosis was confirmed when sequencing of the SLC25A15 gene identified two mutations p.R275Q and p.A76D. Although immediate intervention resulted in normalization of plasma ammonia levels within 24 hours, he developed cerebral edema, coma, convulsions, and subsequent neurological sequelae. Metabolic control was difficult requiring severe protein restriction and continued treatment with sodium benzoate and L‐arginine. Despite substantial developmental delay, he was referred to our center for liver transplantation because of poor metabolic control. Following cadaveric split liver transplantation, there was complete normalization of his plasma ammonia and plasma amino acid levels under a normal protein‐containing diet. This excellent metabolic control was associated with a markedly improved general condition, mood and behavior, and small developmental achievements. Twelve years after liver transplantation, the patient has a stable cognitive impairment without progression of spastic diplegia.

Conclusion

This first case of liver transplantation in HHH syndrome demonstrates that this procedure is a therapeutic option for HHH patients with difficult metabolic control.
Signal informativeness for sequence structure modulates human auditory cortical responses
Authors: Simal Amour , Bermudez Patrick , Lefebvre Christine , Vachon François , Jolicœur Pierre
Published: December 2020

We observed how information about the structure of tone sequences modulates cortical responses in the context of a standard short‐term memory (STM) task. Participants heard two sequences of one, three, or five tones (203 ms on, 203 ms off) interspersed by a silent interval (2 s) and decided whether the sequences were the same or different. In experiment 1, sequence length was randomized between trials. During the first sequence, the amplitude of the auditory P2 was larger for the second tone in trials with three tones, and for the second and fourth tone in trials with five tones. We hypothesize the increase in P2 reflected a dynamic disambiguation process because these tones were predictive of a sequence longer than one or three tones. This hypothesis was supported by the absence of P2 amplitude modulation during the second sequence (when sequence length was known). In experiment 2, we blocked trials by sequence length to ensure the effects were not caused by some process related to encoding in STM. There was no P2 amplitude modulation in either the first or second sequences. Thus, tones 2 and 4 had a larger amplitude only when they provided new information about the length of the current tone sequence. To some extent, the auditory N1 also showed those modulations. Independent Component Analysis of the ERPs provided evidence the modulations in P2 amplitude could originate in auditory cortex. These results suggest a rapid dynamic adaptation of auditory cortical responses based on the local informativeness of auditory signals.
A CHAT about health literacy – a qualitative feasibility study of the Conversational Health Literacy Assessment Tool (CHAT) in a Danish municipal healthcare centre
Authors: Jensen Nanna Husted , Aaby Anna , Ryom Knud , Maindal Helle Terkildsen
Published: December 2020

Background

Understanding individual health literacy needs is crucial when designing supportive and effective health care. However, tools assessing health literacy in practice are lacking. The Conversational Health Literacy Assessment Tool (CHAT) was recently developed, but its ability to assess health literacy remains unexplored. We aimed to investigate the implementation and adoption of CHAT, its ability to increase awareness of health literacy among healthcare providers, and if CHAT could assess health literacy needs in patients.

Methods

We performed a qualitative feasibility study of CHAT among healthcare providers (nurses, physiotherapists and occupational therapists) who provide rehabilitation services for patients with noncommunicable diseases in a municipal healthcare centre in Denmark. The study used the RE‐AIM framework (Reach, Effectiveness, Adoption, Implementation and Maintenance) to structure interview guide and analysis. We collected qualitative data from four small focus groups with healthcare providers (n = 11). The data were analysed using a deductive thematic three‐step method for organising and interpreting data. All informants provided written informed consent prior to data collection.

Results

CHAT seems to be a feasible and efficient tool for assessing health literacy needs among individuals with different socio‐demographic characteristics and with different diagnoses. CHAT was easiest implemented and adopted by healthcare providers, who were already familiarly with the concept of health literacy. The informants emphasised that an introduction to CHAT and health literacy as concept was valuable for the adoption. Some of them felt frustrated that they did not have opportunity and options to meet the health literacy needs identified by CHAT.

Conclusions

CHAT is a promising tool for assessing individual health literacy needs and increasing awareness of health literacy among healthcare providers. For successfully implementation of CHAT, we recommend developing a structured implementation programme, including an introduction to health literacy and an outline of the options for acting upon CHAT results.
Occipital condyle defects assessed by radiography or CT can be a normal finding in foals
Authors: Sage Sophie Elena , Olive Julien , Lavoie Jean‐Pierre
Published: December 2020

Age of complete ossification of equine occipital condyles has not been published. Consequently, clinical significance of occipital condyle defects on radiographs or CT scans of young horses remains unknown. The goals of this single‐center, retrospective, cross‐sectional study were to characterize incidental occipital condyle defects and to define the age of complete ossification. The margin of occipital condyles was classified as regular or with defect(s). Analyses were made on 121 horses, including 106 radiographic and 19 CT studies showing the occipital condyles of horses less than 5 years of age obtained over 6 years in a referral hospital. Neurological signs and outcome were not associated with occipital defects. Horses with regular occipital condyles on radiographs had a median age of 974 days (median interquartile range = 707) compared with 47 days (interquartile range = 106) in the defect group. The odds of finding radiographically regular occipital condyles were 2.6% higher for each additional day of age (P = .011, 95% CI, 0.6‐4.7%). In the CT group, univariate analyses demonstrated a significant effect of age on the aspect of occipital condyles (P = .016). Horses with regular occipital condyles were older (median age = 881 days; interquartile range = 1054) than horses with a defect (median age = 109 days, interquartile range = 318). All horses above 156 days (5.1 months) of age and 550 days (18.1 months) of age had regular occipital condyles on radiographic and CT images, respectively. This study describes occipital condyle defects as a potential normal finding in young horses and provides guidelines for interpretation of the occipital condyle ossification process.
The Stakeholder Agreement Metric: Quantifying Preference Agreement Between Product Stakeholders
Authors: Chou Suzanne , Arezoomand Mojtaba , Coulentianos Marianna J. , Nambunmee Kowit , Neitzel Richard , Adhvaryu Achyuta , Austin-Breneman Jesse
Published: December 2020

Go/no-go decisions require engineering design teams to evaluate whether a concept is worth further investment of resources. These decisions can be difficult when product success depends on multiple stakeholders in addition to the end-user. This study proposes the Stakeholder Agreement Metric (SAM) framework to estimate the level of agreement between stakeholder preferences via the distance between optimal designs calculated from a preference model derived from conjoint analysis. The framework was tested in an empirical case study describing the design and piloting of a hand tool for informal electronic waste workers in Thailand. Data from a follow-up assessment indicate the SAM estimate aligned with future metrics of stakeholder satisfaction. The case study also qualitatively compared SAM to the analytical hierarchy process (AHP). Data collection issues with AHP illustrated some of the practical limitations of the framework. This study suggests that the SAM framework is a promising tool to further explore as a way to support designers making go/no-go decisions that involve multiple stakeholders. Further exploration should include additional case studies to investigate potential outcomes of different SAM values and comparing multiple stakeholder groups.
High-Performance Perovskite Solar Cells Fabricated by a Hybrid Physical–Chemical Vapor Deposition
Authors: Wei Xiangyang , Peng Yanke , Jing Gaoshan , Simon Terrence , Cui Tianhong
Published: December 2020

For the first time, we used a hybrid physical–chemical vapor deposition (HPCVD) method to fabricate perovskite solar cells (PSCs) based on perovskite films with both organic cations and halogen anions. A high power conversion efficiency (PCE) of 18.1% was achieved based on a mixed perovskite film of MAxFA1−xPb (IyBr1−y)3 and the efficiency of the PSCs with MAPbI3 and MAxFA1−xPbI3 films were 14.5% and 16.4%, respectively. Perovskite material components and bandgaps were precisely tuned to achieve high photoelectric conversion performance. Three different types of perovskite films employed include MAPbI3, MAxFA1−xPbI3, and MAxFA1−xPb (IyBr1−y)3 (which are also designated as MAPbI3, MA0.89FA0.11PbI3, and MA0.54FA0.46Pb (I0.94Br0.06)3 with the respective bandgaps of 1.60 eV, 1.58 eV, and 1.61 eV. The experimental results demonstrate the ability to fabricate both organic cation and halogen anion mixed perovskite films by the HPCVD method and achieve easily adjustable bandgaps. In addition, the perovskite films fabricated by HPCVD have superior surface morphology, large crystal size, and low surface roughness. Eventually, this vapor-based method will have great potential in the fabrication of large-area and flexible PSCs to promote commercial application and industrialization of future PSCs.
Modelling of Soot Formation and Experimental Study for Different Octane Number Fuels in Dual Fuel Combustion Engine With Diesel
Authors: Krishnamoorthi M. , Sreedhara S. , Duvvuri Pavan Prakash
Published: December 2020

This work investigates the effects of low reactivity fuel (LRF) on reactivity controlled compression ignition (RCCI) engine with fossil diesel. RCCI mode of combustion is a low temperature combustion (LTC) strategy which reduces both oxides of nitrogen (NOx) and soot emissions simultaneously. Syngas and methanol can be obtained from renewable biological resources and conventional coal. LRF (methanol, syngas and gasoline) has been supplied to the engine along with intake air and diesel is injected to initiate the combustion process. Test engine has been operated for different dual fuel modes at constant engine speed (1500 rpm) and load (80%). Closed cycle combustion simulations have been performed to complement the experimental results and in-cylinder dynamics. Particle size mimic (PSM) model has been used to investigate the soot particle number and mass-size distributions and mean particle size. Results confirmed that maximum gross indicated thermal efficiency (38%) has been observed in gasoline/diesel dual fuel mode. Compared to gasoline/diesel dual fuel mode, about 74% and 86%, lower soot and NOx emissions have been observed for methanol/diesel dual fuel mode, while about 46% and 52% lower soot and NOx emissions have been found in syngas/diesel mode. About 53% higher carbon monoxide emission has been observed for syngas/diesel case as compared to gasoline/diesel case. Predictions from soot modelling reveal that condensation mode, surface growth mode and nucleation mode particles are dominant in methanol, syngas and gasoline/diesel dual fuel modes respectively. Bigger primary soot particles (diameter > 35 nm, nanometre) have been observed for methanol/diesel mode and the gasoline/diesel mode shows a smaller size of primary particles.
Towards Integrated Spark and Combustion Modeling for Engines
Authors: Karpatne Anand , Subramaniam Vivek , Joshi Sachin , Qin Xiao , Breden Douglas , Sofianopoulos Aimilios , Raja Laxminarayan
Published: December 2020

Combustion and emission performance of internal combustion (IC) engines depend on the ability of the ignition system to provide an ignition kernel that can successfully transition into an early flame kernel. Several key physical phenomena such as flow physics, plasma dynamics, circuit transients, and electromagnetics influence the behavior of the spark. The combustion kinetics decide the eventual transition of the spark into a self-sustaining flame kernel. The goal of this paper is to present a feasibility study involving the integration of a high-fidelity magnetohydrodynamic description of the spark physics with a finite rate chemical kinetics-based combustion model. A future goal of this proposed framework will be to model and validate a coupled ignition and combustion simulation for spark ignited engines. Two separate solvers are used to model spark physics and combustion kinetics respectively, and a coupling strategy is developed to model different aspects of physics occurring at disparate time-scales. This approach provides a physically consistent estimate of the electrical energy distribution within the spark-gap under high cross-flow velocities. When provided with certain favorable in-cylinder conditions, the spark kernel triggers self-sustained combustion.
Combustion of Hydrotreated Vegetable Oil in a Diesel Engine: Sensitivity to Split Injection Strategy and Exhaust Gas Recirculation
Authors: Mikulski Maciej , Hunicz Jacek , Vasudev Aneesh , Rybak Arkadiusz , Gęca Michał
Published: December 2020

This work explores the potential to optimize advanced common-rail engines for operation with hydrotreated vegetable oil (HVO). The single-cylinder engine research focuses on adjusting the injection strategy and external exhaust gas recirculation (EGR) to achieve the optimum performance-emissions trade-off using HVO. The engine is operated at a fixed rotational speed of 2000 rpm and under constant load (net indicated mean effective pressure of 0.45 MPa). Split fuel-injection strategy is used: main injection timing is fixed but pilot injection is varied both in terms of timing and quantity. The engine tests, without turbocharging, are conducted under non-EGR conditions and using approximately 27% EGR rate. Results with HVO are compared with results when using diesel fuel.

Within the constraints of a single, representative operating point, the results highlight that when using the factory map-based injection strategy, HVO offers soot emissions below 0.015 g/kWh, a 50% reduction when compared to diesel fuel. Nitrogen oxides (NOx) emissions at the same conditions are, however, 10% higher than for diesel fuel. That correlates with higher peak in-cylinder pressures and temperatures. Advancing the pilot HVO injection reduced NOx emissions to the level of the diesel baseline, and although soot emissions increased, they remained 25% lower than with diesel. Interestingly, the two tested fuels exhibited very different responses to EGR. Generally, at 27% EGR, HVO produced twice as much soot as diesel. The heat release analysis indicates this sensitivity to EGR stems from HVO’s higher cetane number causing faster auto-ignition, resulting in less premixed combustion and hence producing more soot. Generally, HVO offered more complete combustion than diesel fuel. Regardless of pilot fuel injection strategy, CO emission was reduced by approximately 50% with HVO for both EGR and non-EGR conditions. HVO also benefits emissions of unburned hydrocarbons, in terms of both total values and also unlegislated aldehydes and aromatics.
Engine Performance and Emissions for a Heavy-Duty Diesel Engine Converted to Stoichiometric Natural Gas Operation
Authors: Liu Jinlong , Ulishney Christopher , Dumitrescu Cosmin E.
Published: December 2020

Converting existing compression ignition (CI) engines to spark ignition (SI) operation can increase the use of natural gas (NG) in heavy-duty engine applications and reduce the reliance on petroleum fuels. Gas fumigation upstream of the intake manifold and the addition of a spark plug in place of the diesel injector to initiate and control the combustion process is a convenient approach for converting existing diesel engines to dedicated NG operation. Stoichiometric operation and a three-way catalytic converter can help the engine to comply with increasingly strict emission regulations. However, as the CI-to-SI conversion usually maintains the conventional geometry of a CI engine (i.e., maintains the flat cylinder head and the bowl-in piston), the goal of this study was to observe some of the effects that the diesel conversion to stoichiometric NG SI operation will have on the engine’s performance and emissions. Dynamometer tests were performed at a constant engine speed at 1300 rpm but various spark timings. The experimental results for a net indicated mean effective pressure ∼ 6.7 bar showed that ignition timing did not affect the end of combustion due to the slow-burn inside the squish. Moreover, the less-optimal conditions inside the squish led to increased carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions. While the combustion event was stable with no signs of knocking at the medium load conditions investigated here, the results suggest that the engine control needs to optimize the mass fraction trapped inside the squish region for a higher efficiency and lower emissions.
Improving Machine Learning Model Performance in Predicting the Indicated Mean Effective Pressure of a Natural Gas Engine
Authors: Liu Jinlong , Ulishney Christopher , Dumitrescu Cosmin E.
Published: December 2020

Converting existing compression ignition engines to spark ignition approach is a promising approach to increase the application of natural gas in the heavy-duty transportation sector. However, the diesel-like environment dramatically affects the engine performance and emissions. As a result, experimental tests are needed to investigate the characteristics of such converted engines. A machine learning model based on bagged decision trees algorithm was established in this study to reduce the experimental cost and identify the operating conditions of special interest for analysis. Preliminary engine tests that changed spark timing, mixture equivalence ratio, and engine speed (three key engine operation variables) but maintained intake and boundary conditions were applied as model input to train such a correlative model. The model output was the indicated mean effective pressure, which is an engine parameter generally used to assist in locating high engine efficiency regions at constant engine speed and fuel/air ratio. After training, the correlative model can provide acceptable prediction performance except few outliers. Subsequently, boosting ensemble learning approach was applied in this study to help improve the model performance. Furthermore, the results showed that the boosted decision trees algorithm better described the combustion process inside the cylinder, as least for the operating conditions investigated in this study.
Optimization of Direct Water Injection Parameters to Improve the Trade-off Between Efficiency and NOx Emissions for a Lean-Burn CHP NG Engine
Authors: Beltaifa Youssef , Holzberger Sascha , Aslan Ferhat , Kettner Maurice , Eilts Peter
Published: December 2020

In the medium and long term, cogeneration plants in Germany will play an important role in the transition towards a cleaner and more efficient electricity and heat generation, compared to the conventional uncoupled power plants. For most of the currently used CHP (Combined Heat and Power) units, which operate with a lean-burn process, the NOx emissions limit represents an obstacle to increasing the electrical efficiency. Therefore, the lean burn process has become less attractive because of stricter future NOx emissions limit. In this context, the stoichiometric combustion process with a three-way catalytic converter provides a solution. However, the present study shows that lean burn operation still has potential due to direct water injection into the combustion chamber.

This work includes an experimental investigation of the impact of different injection parameters (beginning of injection timing, injection pressure difference and water-to-fuel ratio) on the effectiveness of direct water injection regarding the improvement of the trade-off between engine efficiency and NOx emissions. For the execution of the experimental investigations, a series-production CHP-engine was equipped with a direct injection system consisting of a high-pressure unit, a high-pressure pipe and a GDI-injector. For the injector integration, the cylinder head was machined sidewise (close to the exhaust gas valve). Furthermore, 3D CFD simulations of the injection process allowed gaining a deeper insight into the complex spray-flow interaction, wall film formation and evaporation at different injection timings. For the 3D CFD simulations, the spray model used was tuned with help of spray pictures, taken on the spray test bed.

Water injection at the beginning of the intake stroke (330 °CA BFTDC) reduces NOx emissions most effectively. Moreover, it causes the least engine efficiency loss. The increase of the injection pressure difference (between 20 and 80 bar) leads to a significant increase of the engine efficiency. However, it has a secondary effect on the NOx emissions reduction. The lowest NOx emissions are reached with an injection pressure difference of 60 bar. The combination of direct water injection (at the beginning of the intake stroke, injection pressure difference of 60 bar) with earlier combustion phasings enables an increase in the engine efficiency and a simultaneous decrease in NOx emissions without loss in engine performance. Main drawbacks of water injection are longer combustion duration and higher CO and HC emissions. In addition, the lower exhaust gas temperature causes a deterioration of the conversion of the HC molecules in the oxidation catalyst and reduces the heat recovery efficiency of the CHP-system.
X-Ray Characterization of Real Fuel Sprays for Gasoline Direct Injection
Authors: Sforzo Brandon A. , Tekawade Aniket , Kastengren Alan L. , Fezzaa Kamel , Ilavsky Jan , Powell Christopher F. , Pei Yuanjiang , Zhang Anqi , Levy Robert
Published: December 2020

The effects of fuel blend properties on spray and injector performance has been investigated for several operating conditions in a side-mount injector for Gasoline Direct Injection (GDI) using two certification fuel blends, Euro 5 and Euro 6. Several X-ray diagnostic techniques were conducted to characterize the injector and spray morphology. Detailed internal geometry of the GDI injector was measured with a feature-resolution of 1.8 micrometers, through the use of hard X-ray tomography. The geometry characterization of this six-hole GDI, side mount injector, quantifies relevant hole and counterbore dimensions and reveals the intricate details within the flow passages, including surface roughness and micron-sized features. Internal valve motion was measured with a temporal resolution of 20 microseconds and a spatial resolution of 2.0 micrometers, for three injection pressures and several injector energizing strategies. The needle motion for both fuels exhibit similar lift profiles for common energizing commands. A combination of X-ray radiography and Ultra-Small-Angle X-ray Scattering (USAXS) was used to characterize the fuel mass distribution and the droplet sizing, respectively. Tomographic spray radiography revealed the near-nozzle distribution of fuel mass for each of the fuels, and the asymmetry produced by the angled nozzles. Under evaporative conditions, the two fuels show minor differences in peak fuel mass distribution during steady injection, though both exhibit fluctuations in injection during the early, transient phase. US-AXS measurements of the path-specific surface area of the spray indicated lower peak values for the more evaporative conditions in the near nozzle region. These spray measurements portray the specific behavior of real fuel blends under a variety of conditions, illustrating the need to examine multi-component fuels to better understand relevant cases. Furthermore, this work furnishes the realistic boundary values for simulations to appropriately predict the sprays which were experimentally measured, and influenced by those realistic conditions.
An Automated Machine Learning-Genetic Algorithm (AutoML-GA) Framework With Active Learning for Design Optimization
Authors: Owoyele Opeoluwa , Pal Pinaki , Vidal Torreira Alvaro
Published: December 2020

The use of machine learning (ML) based surrogate models is a promising technique to significantly accelerate simulation-based design optimization of IC engines, due to the high computational cost of running computational fluid dynamics (CFD) simulations. However, surrogate-based optimization for IC engine applications suffers from two main issues. First, training ML models requires hyperparameter selection, often involving trial-and-error combined with domain expertise. The second issue is that the data required to train these models is often unknown a priori. In this work, we present an automated hyperparameter selection technique coupled with an active learning approach to address these challenges. The technique presented in this study involves the use of a Bayesian approach to optimize the hyperparameters of the base learners that make up a Super Learner model to obtain better test performance. In addition to performing hyperparameter optimization (HPO), an active learning approach is employed, where the process of data generation using simulations, ML training, and surrogate optimization, is performed repeatedly to refine the solution in the vicinity of the predicted optimum. The proposed approach is applied to the optimization of a compression ignition engine with control parameters relating to fuel injection, in-cylinder flow, and thermodynamic conditions. It is demonstrated that by automatically selecting the best values of the hyperparameters, a 1.6% improvement in merit value is obtained, compared to an improvement of 1.0% with default hyperparameters. Overall, the framework introduced in this study reduces the need for technical expertise in training ML models for optimization, while also reducing the number of simulations needed for performing surrogate-based design optimization.
RCCI With High Reactivity S8-ULSD Blend and Low Reactivity N-Butanol
Authors: Soloiu Valentin , Carapia Cesar E. , Smith Richard , Weaver Amanda , Mckinney Levi , Mothershed David , Grall Drake , Ilie Marcel , Rahman Mosfequr
Published: December 2020

A fuel blend consisting of 10% S8 by mass (a Fischer-Tropsch synthetic kerosene), and 90% ULSD (Ultra Low Sulfur Diesel) was investigated for their combustion characteristics and impact on emissions during RCCI (Reactivity Controlled Compression Ignition) combustion in a single cylinder experimental engine utilizing a 65% by mass n-butanol port fuel injection (PFI). RCCI is a dual fuel combustion strategy achieved with the introduction of a PFI fuel of the low-reactive n-butanol, and a direct injection (DI) of a high-reactivity blend (FT-BLEND) into an experimental diesel engine. The combustion analysis and emissions testing were conducted at 1500 RPM at an engine load of 5 bar IMEP (Indicated Mean Effective Pressure), and CA50 of 9° ATDC (After Top Dead Center); CDC (Conventional Diesel Combustion) and RCCI with 65Bu-35ULSD were utilized as the baseline for AHRR (Apparent Heat Release Rate), ringing and emissions comparisons. It was found during a preliminary investigation with a Constant Volume Combustion Chamber (CVCC) that the introduction of 10% by mass S8 into a mixture with 90% ULSD by mass only increased Derived Cetane Number (DCN) by 0.8, yet it was found to have a significant effect on the combustion characteristics of the fuel blend.

This led to the change in injection timing necessary for maintaining 65Bu-35F-T BLEND RCCI at a CA50 of 5° ATDC (After Top Dead Center) to be shifted 3° closer to TDC, thus affecting the Ringing Intensity (RI), Pressure Rise Rate, and heat release of the blend all to decrease. CDC was conducted with a primary injection of 14° BTDC at a rail pressure of 800 bar, all RCCI testing was conducted with 65% PFI of n-butanol by mass and 35% DI, to prevent knock, with a rail pressure of 600 bar and a pilot injection of 60° BTDC for 0.35 ms. 65Bu-35ULSD RCCI was conducted with a primary injection at 6° BTDC with neat ULSD#2, the fuel 65Bu-35F-T BLEND in RCCI had a primary injection at 3° BTDC to maintain CA50 at 9° ATDC. 65Bu-35ULSD RCCI experienced a NOx and soot emissions decrease of 40.8% and 91.44% respectively in comparison to CDC. The fuel 65Bu-35F-T BLEND in RCCI exhibited an additional decrease of NOx and soot of 32.9 and 5.3%, in comparison to 65Bu-35ULSD RCCI for an overall decrease in emissions of 73.7% and 96.71% respectively. Ringing Intensity followed a similar trend with reductions in RI for 65Bu-35ULSD RCCI decreasing only by 6.2% whereas 65Bu-35F-T BLEND had a decrease in RI of 76.6%. Although emissions for both RCCI fuels experienced a decrease in NOx and soot in comparison to CDC, UHC and CO did increase as a result of RCCI. CO emissions for 65Bu-35ULSD RCCI and 65Bu-35F-T BLEND where increased from CDC by a factor of 5 and 4 respectively with UHC emissions rising from CDC by a factor of 3.4. The fuel 65Bu-35F-T BLEND had a higher combustion efficiency than 65Bu-35ULSD in RCCI at 91.2% due to lower CO emissions of the blend.
Comparing Cetane Number Measurement Methods
Authors: Abel Riley C. , Luecke Jon , Ratcliff Matthew A. , Zigler Bradley T.
Published: December 2020

Cetane number is one of the most important fuel performance metrics for mixing controlled compression-ignition “diesel” engines, quantifying a fuel’s propensity for autoignition when injected into end-of-compression-type temperature and pressure conditions. The historical default and referee method on a Cooperative Fuel Research (CFR) engine configured with indirect fuel injection and variable compression ratio is cetane number (CN) rating. A subject fuel is evaluated against primary reference fuel blends, with heptamethylnonane defining a low-reactivity endpoint of CN = 15 and hexadecane defining a high-reactivity endpoint of CN = 100. While the CN scale covers the range from zero (0) to 100, typical testing is in the range of 30 to 65 CN. Alternatively, several constant-volume combustion chamber (CVCC)-based cetane rating devices have been developed to rate fuels with an equivalent derived cetane number (DCN) or indicated cetane number (ICN). These devices measure ignition delay for fuel injected into a fixed volume of high-temperature and high-pressure air to simulate end-of-compression-type conditions. In this study, a range of novel fuel compounds are evaluated across three CVCC methods: the Ignition Quality Tester (IQT), Fuel Ignition Tester (FIT), and Advanced Fuel Ignition Delay Analyzer (AFIDA). Resulting DCNs and ICNs are compared for fuels within the normal diesel fuel range of reactivity, as well as very high (∼100) and very low DCNs/ICNs (∼5). Distinct differences between results from various devices are discussed. This is important to consider because some new, high-efficiency advanced compression-ignition (CI) engine combustion strategies operate with more kinetically controlled distributed combustion as opposed to mixing controlled diffusion flames. These advanced combustion strategies may benefit from new fuel chemistries, but current rating methods of CN, DCN, and ICN may not fully describe their performance. In addition, recent evidence suggests ignition delay in modern on-road diesel engines with high-pressure common rail fuel injection systems may no longer directly correlate to traditional CN fuel ratings. Simulated end-of-compression conditions are compared for CN, DCN, and ICN and discussed in the context of modern diesel engines to provide additional insight. Results highlight the potential need for revised and/or multiple fuel test conditions to measure fuel performance for advanced CI strategies.
Study on Design Method of Combustion Reference Values for Model-Based Control of Advanced Diesel Engine
Authors: Kim Jihoon , Yamasaki Yudai
Published: December 2020

Model-based control systems are drawing attention in relation to implementing next-generation combustion technologies with high thermal efficiency and low emissions, such as homogeneous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI) combustion, which have low robustness. A model-based control system derives control inputs according to reference values and operating conditions during every cycle and has potential to replace the conventional control map, which requires a large number of experiments. However, model-based control for engines requires reference values for combustion, such as heat release peak timing and heat release peak value; such values represent the combustion state. Therefore, the reference for the transient condition is important for utilizing the benefit of model-based control systems, given that such systems derive control outputs cycle by cycle.

In this study, a design method for the combustion reference values for the transient operating condition is described for advanced diesel combustion, which uses premixed compression ignition combustion by multiple fuel injections. Specifically, a statistical method and a method based on model prediction considering the driving characteristics are proposed and compared in engine control experiments. These proposed methods were evaluated under defined simple transient operation conditions and worldwide harmonized light vehicles test cycles (WLTC) mode considering real road conditions. Results showed that designing the combustion reference values for transient operation by model prediction is effective, and such method has the potential to reflect the driving characteristics.
Influence of Fuel Properties on GDI PM Emissions Over First 200 Seconds of WLTP Using an Engine Dynamometer and Novel “Virtual Drivetrain” Software
Authors: Bock Noah R. , Northrop William F.
Published: December 2020

The influence of fuel properties on particulate matter (PM) emissions from a catalytic gasoline particulate filter (GPF) equipped gasoline direct injection (GDI) engine were investigated using novel “virtual drivetrain” software and an engine mated to an engine dynamometer. The virtual drivetrain software was developed in LabVIEW to operate the engine on an engine dynamometer as if it were in a vehicle undergoing a driving cycle. The software uses a physics-based approach to determine vehicle acceleration and speed based on engine load and a programed “shift” schedule to control engine speed. The software uses a control algorithm to modulate engine load and braking to match a calculated vehicle speed with the prescribed speed trace of the driving cycle of choice. The first 200 seconds of the WLTP driving cycle was tested using 6 different fuel formulations of varying volatility, aromaticity, and ethanol concentration. The first 200 seconds of the WLTP was chosen as the test condition because it is the most problematic section of the driving cycle for controlling PM emissions due to the cold start and cold drive-off. It was found that there was a strong correlation between aromaticity of the fuel and the engine-out PM emissions, with the highest emitting fuel producing more than double the mass emissions of the low PM production fuel. However, the post-GPF PM emissions depended greatly on the soot loading state of the GPF. The fuel with the highest engine-out PM emissions produced comparable post-GPF emissions to the lowest PM producing fuel over the driving cycle when the GPF was loaded over three cycles with the respective fuels. These results demonstrate the importance of GPF loading state when aftertreatment systems are used for PM reduction. It also shows that GPF control may be more important than fuel properties, and that regulatory compliance for PM can be achieved with proper GPF control calibration irrespective of fuel type.