bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antiarrhythmic drug effects on premature beats are partly determined by prior cardiac activation frequency in perfused guinea‐pig heart
Authors: Osadchii Oleg E. 
Published: March 2020

New Findings
What is the central question of this study?
Can antiarrhythmic drug effects on repolarization, conduction time and excitation wavelength in premature beats be determined by prior cardiac activation frequency?

What is the main finding and its importance?
In premature beats induced after a series of cardiac activations at a slow rate, antiarrhythmics prolong repolarization but evoke little or no conduction delay, thus increasing the excitation wavelength, which indicates an antiarrhythmic effect. Fast prior activation rate attenuates prolongation of repolarization, while amplifying the conduction delay induced by drugs, which translates into the reduced excitation wavelength, indicating proarrhythmia. These findings suggest that a sudden increase in heart rate can shape adverse pharmacological profiles in patients with ventricular ectopy.
AbstractAntiarrhythmic drugs used to treat atrial fibrillation can occasionally induce ventricular tachyarrhythmia, which is typically precipitated by a premature ectopic beat through a mechanism related, in part, to the shortening of the excitation wavelength (EW). The arrhythmia is likely to occur when a drug induces a reduction, rather than an increase, in the EW of ectopic beats. In this study, I examined whether the arrhythmic drug profile is shaped by the increased cardiac activation rate before ectopic excitation. Ventricular monophasic action potential durations, conduction times and EW values were assessed during programmed stimulations applied at long (S1–S1 [basic drive cycle length] = 550 ms) and short (S1–S1 = 200 ms) cycle lengths in perfused guinea‐pig hearts. The premature activations were induced with extrastimulus application immediately upon termination of the refractory period. With dofetilide, a class III antiarrhythmic agent, a prolongation in action potential duration and the resulting increase in the EW obtained at S1–S1 = 550 ms were significantly attenuated at S1–S1 = 200 ms, in both the regular (S1) and the premature (S2) beats. With class I antiarrhythmic agents (quinidine, procainamide and flecainide), fast S1–S1 pacing was found to attenuate the drug‐induced increase in action potential duration, while amplifying drug‐induced conduction slowing, in both S1 and S2 beats. As a result, although the EW was increased (quinidine and procainamide) or not changed (flecainide) at the long S1–S1 intervals, it was invariably reduced by these agents at the short S1–S1 intervals. These findings indicate that the increased heart rate before ectopic activation shapes the arrhythmic profiles by facilitating drug‐induced EW reduction.
System Parameter Optimization for a Frequency-Up-Conversion Piezoelectric Energy Harvester With Backward Mechanical-Electric Coupling Effect
Authors: Wang Fengxia 
Published: March 2020

Abstract
In this work, a parametric model for a frequency-up-conversion piezoelectric energy harvester (PEH) was developed based on the Galerkin method. The PEH is composed of a piezoelectric bimorph and a stopper, which was subjected to a harmonic excitation. Although backward coupling results in a structure dynamic damping, models with neglected backward coupling were often adopted to estimate the output power of a piezoelectric energy harvester. The purpose of this work is to examine the effect of backward coupling on the dynamic response and the output power generation for a frequency-up-conversion PEH. With the same base excitations, we compared the dynamics and output energies of two cases: (1) neglecting the backward coupling effect (BCE) in the model and (2) including the BCE in the model. To obtain the optimum gap with maximum output power, we studied the relationship between the output power and the gap of the steady-state solutions. From the analytical results, it was found that the BCE can be neglected as long as there is no impact or the output power is small. However, once impacts get involved, the piezoelectric backward effect dominates the total damping due to small mechanical damping which is true for most PEH. The backward coupling will significantly diminish both the vibration and output power. Therefore, if the BCE is neglected in an impact-driven frequency-up-conversion PEH, the simplified model will exaggerate the output power.
How Chemistry Controls Engine Design
Authors: Flynn Patrick F. 
Published: March 2020

Abstract
A review of empirical engine data that exhibit the limits of the chemistry of fuel oxidation in engines is presented. These data have been compared to analyses using up to date fuel oxidation chemical analyses programs and shown to be in close agreement. The constraints caused by the fuel oxidation chemistry limitations are key determinants of the engine’s overall design, determining allowed intake conditions, fuel-air ratios, compression ratio requirements, and the need for such ancillary devices as those for exhaust emissions aftertreatment.
Diesel Spray Development From VCO Nozzles With Common-Rail
Authors: Bae Choongsik , Kang Jinsuk , Lee Hang-Kyung 
Published: March 2020

Abstract
Spray characteristics of diesel fuel injection system is one of the most important factors in diesel combustion and pollutant emissions especially in HSDI (High Speed Direct Injection) diesel engines where the interval between the onset of combustion and the evaporation of atomized fuel is relatively short.
An investigation into various spray characteristics from different holes of VCO (Valve Covered Orifice) nozzles was performed. The global characteristics of spray, including spray angle, spray tip penetration, and spray pattern were measured from the spray images, which were frozen by an instantaneous photography with a spark light source and ICCD. These spray images were acquired sequentially from the first injection to fifth injection to investigate injection-to-injection variation. For better understanding of spray development and their internal structures, a long-distance microscope was used to get magnified spray images at the vicinity of the nozzle hole with a laser sheet illumination. Also backward illuminated images with a spark light source were taken at various points of the spray field including vicinity of the nozzle hole to understand surface structures and breakup process of dense spray from VCO nozzle incorporated with common-rail injection system.
As injection pressure increases interaction between spray and ambient air becomes important to liquid penetration and spray angle. Macroscopic spray angle increases due to air entrainment as injection pressure increases though spray angle near the hole seems independent from injection pressure. Liquid penetration is initially affected by injection rate increase as needle is moving upward and liquid penetration increase rate is in accordance with injection pressure. After this stage, air entrainment and high potential of evaporation makes the increase rate slower and this tendency is more obvious for higher injection pressure. Microscopic images taken at the vicinity of the nozzle hole exit reveal that central dense region consists of thick ligaments or membranes and most of the liquid droplets are formed at the tip of ligaments from spray surface due to the waves developed on it. Some smaller liquid droplets seem to be generated from the bubble or membrane breakup process. Droplet sizing was performed from the microscopic images, which were frozen by spark light source that has light duration of 10ns and high-resolution CCD camera equipped with long distance microscope whose magnification factor is more than six. Fuel particle sizes, described as SMD (Sauter Mean Diameter) in many points, decreased during injection durations and higher injection pressure induced smaller value.
Effect of Injection Rate on the Performance and Emissions of a Direct-Injection Gasoline Engine in Comparison With the Port-Injection Operation
Authors: Shiga Seiichi , Kobayashi Kazumitsu , Hayakawa Eiji , Matsuura Takashi , Nakamura Hisao , Ishima Tsuneaki , Obokata Tomio 
Published: March 2020

Abstract
This paper presents a study on the effect of injection rate on the performance and emissions of a direct-injection gasoline engine operated with seven kinds of DI injection and a port-injection. The injection pressures were set at 0.3 and 7 MPa for port injection and DI operation modes respectively. The spray characteristics of DI injectors were obtained by measuring the SMD, droplet concentration and spray angle. The engine was run at a constant speed and load of 1000 rpm and 0.22 MPa of BMEP. The BSFC reduction of DI from port injection was 13% at most in which 4% was derived from the decrease in pumping loss and the remaining 9% was due to the improvement of the cycle efficiency. As for the injection rate effect in DI operation, the BSFC takes the minimum at a value of the injection rate where the maximum difference reached to 7%. It was revealed that this is due to the variation of the combustion efficiency and then corresponds to the behavior of droplet concentration. Soot emission correlated well with the SMD. Thus the performance and emissions were mostly explained by the spray characteristics.
An Experimental and Numerical Investigation of Turbulent Mixing of Subsonic Gas Jets in a Coaxial Configuration
Authors: Mahalakshmi N. V. , Ilangovan V. 
Published: March 2020

Abstract
Measurements of mean temperature, velocity, the normal stresses and Reynolds shear stress are reported in the mixing region of coaxial jet flows. The measurements were obtained with three different outer jet exit temperature of 15, 30 and 45°C above ambient with the constant exit Reynolds number. The satisfactory representation of the jet is dependent on adequate representation of turbulence in the jet, which determines its spread and mixing. The standard k-ε model is used to predict the mean and turbulent flow fields. The deviation of predicted results from experimental kinetic energy at high exit temperature difference can be due to the anistotropic charter of the mixing region. Measurements performed at different axial stations provide a broad database against which result of calculation procedures embodying k-ε turbulence model can be compared. The normal stress results show substantial deviations from isotropy. This clearly indicates the need to consider the normal stresses in any turbulence model of such flows.
Passenger-Car Fuel Consumption Versus Performance in Retrospect
Authors: Amann Charles A. 
Published: March 2020

Abstract
Over the last quarter of the 1900s, the U.S. Environmental Protection Agency (EPA) has annually tabulated the fuel economy and performance characteristics of the new passenger-car fleet. Fuel economy was measured over the EPA combined urban and highway driving schedules. The performance metric was the estimated acceleration time from a standing start to 60 miles per hour (mph). In the present study, the interplay among factors influencing these characteristics is reviewed. Then, for the average new car in a given year, the manner in which fuel consumption and acceleration time are influenced by vehicle weight and engine power are examined. The departure of individual vehicles from this average trend is considered. Finally, a few of the prominent powertrain characteristics responsible for improvements in the tradeoff between fuel consumption and performance are listed.
A Multiple-Zone Cycle Simulation for Spark-Ignition Engines: Thermodynamic Details
Authors: Caton Jerald A. 
Published: March 2020

Abstract
A thermodynamic cycle simulation was developed for a spark-ignition engine which included the use of multiple zones for the combustion process. This simulation was used to complete analyses for a commercial, spark-ignition V-8 engine operating at a part load condition. Specifically, the engine possessed a compression ratio of 8.1:1, and had a bore and stroke of 101.6 and 88.4 mm, respectively. A part load operating condition at 1400 rpm with an equivalence ratio of 1.0 was examined.
Results were obtained for overall engine performance, for detailed in-cylinder events, and for the thermodynamics of the individual processes. In particular, the characteristics of the engine operation with respect to the combustion process were examined. Implications of the multiple zones formulation for the combustion process are described.
Engine Variables Affecting the SI Engine Knock
Authors: Karimifar Mansoor 
Published: March 2020

Abstract
To program the automatic performance control loops of the modern cars at the design stage, numerical result of engine variables effecting knock intensity is the most important tool. Although general aspects of the effect of engine operating conditions on knock have been studied in previous investigations, precise numerical results of that, are not available. The procedures proposed in the past to provide the requirements of the models either predicting or measuring knock are complicated and the details are not presented.
In the current work, on the basis of the ‘sampling frequency theorem’ and in regard to the measured frequency of the knocking-pressure fluctuations, a fast on-line data acquisition system was designed and developed. The system was used on a variable compression ratio research engine using two different fuels. Large number of the engine pressure crank angle data were recorded at different operating conditions. Knock, intensity measurement was carried out using a developed criteria obtained by a careful analysis of pressure oscillations at 0.25 degree crank angle intervals. This lead to identification of cycles having specified knock intensity over a wide range of operating conditions. Effect of engine variables on knock intensity was therefore measured numerically for both fuels. Using the simple criteria to study the effect of engine operating conditions on the intensity of knock produced the results which agreed with the earlier experimental findings.
Modeling Direct-Injection Gasoline HCCI Combustion Using Detailed Chemistry and CFD
Authors: Kong Song-Charng , Reitz Rolf D. 
Published: March 2020

Abstract
Detailed chemical kinetics was implemented into an engine CFD code to study the combustion process in Homogeneous Charge Compression Ignition (HCCI) engines. The CHEMKIN code was implemented into KIVA-3V such that the chemistry and flow solutions were coupled. Effects of turbulent mixing on the reaction rates were also considered. The model was validated using experimental data from a direct-injection Caterpillar engine operated in the HCCI mode using gasoline. The results show that good levels of agreement were obtained using the present KIVA/CHEMKIN model for a wide range of engine conditions including various injection timings, engine speeds, and loads. It was found that the effects of turbulent mixing on the reaction rates needed to be considered to correctly simulate the combustion phasing. It was also found that the presence of residual radicals could enhance the mixture reactivity and hence shorten the ignition delay time. The NOx emissions were found to increase as the injection timing was retarded, in agreement with experimental results.
Combustion Characteristics of Spark Ignition Engine Fuelled by LPG
Authors: Shehata M. S. 
Published: March 2020

Abstract
Experimental studies have been carried out for investigating engine performance parameters, cylinder pressure, emissions and engine thermal balance of spark ignition engine (S.I.E.) using either gasoline or Liquefied Petroleum Gases (LPG) as a fuel at maximum brake torque (MBT) ignition timing. MBT ignition timing for LPG is found to be 2 to 10 degrees crank angle more advance than for gasoline. Maximum cylinder pressure locations for gasoline and LPG are shifted towards top dead center (TDC) with increase engine speed. At low engine speed, maximum cylinder pressure for gasoline fuel is higher than for LPG fuel. At high engine speeds maximum cylinder pressure for LPG is nearly the same as for gasoline. Maximum pressure for ignition timing 35 crank angle (CA) before top dead center (BTDC) is greater than for 45 and 25 CA respectively. Engine produces more brake power with gasoline than with LPG. Engine brake thermal efficiency (ηbth) and volumetric efficiency (ηv) with LPG is less than for gasoline. When S.I.E converted from gasoline to LPG the loss in maximum power is nearly 14% and the loss in maximum efficiency is nearly 8%. UHC and CO concentrations for LPG are nearly one-tenth of that produced by gasoline at the same ignition timing and the same engine speed. For low engine speed exhaust and oil temperatures for gasoline and LPG increase with increase engine speed but for high engine speed exhaust and oil temperature decreases with increase engine speed. For gasoline and LPG cooling water temperature decreases with increase engine speed. Lubricating oil and cooling water temperatures for gasoline and LPG increase with increase ignition timing BTDC but exhaust gas temperature decreases with increase ignition timing. LPG has higher exhausted gas temperature than gasoline but gasoline has higher oil temperature than LPG. At different ignition timing exhaust loss for LPG is greater than for gasoline but cooling water loss for gasoline is greater than for LPG.
Preliminary Investigation of Dilution Strategies to Control Engine Torque During Transient Events
Authors: Maugham R. D. , Vaughan N. D. , Brace C. J. , Murray S. W. 
Published: March 2020

Abstract
A continuously variable transmission (CVT) allows a powertrain controller the freedom to develop a required output power at a range of engine torque and speed conditions. This flexibility can be used to maximise fuel efficiency. Due to low frictional and pumping losses a gasoline engine’s fuel efficiency is maximised at low speed, high torque conditions. However due to the reduced torque margin available, controlling a gasoline engine in this region compromises transient vehicle response. Dilution torque control, using EGR or lean burn, has the potential to maintain the economy gains available using a CVT powertrain whilst improving a vehicle’s driveability.
This paper introduces preliminary work that has been undertaken to investigate the potential of charge dilution to control steady state engine torque. A test rig has been developed based around an engine fitted with variable cam phasing and an external EGR system. The paper contains a discussion of initial results of a lean dilution test program used to demonstrate the principle.
Optimum Design of the Continuously Variable Transmission for a Motorcycle
Authors: Huang Yuan Mao , Hu Bi Shyang 
Published: March 2020

Abstract
Many design parameters affect the performance of continuous variable transmissions. This paper presents the optimization of a continuous variable transmission by using the simulated annealing algorithm. The Bessel method of curve fitting and the tensor product method of surface fitting were used to facilitate the discrete fuel consumption, emissions of carbon monoxide (CO) and HC compound of experimental engine data. A compromise method was used to analyze the multi-objective functions. The values for design variables are recommended for further development.
Effects of Drop Jumps on 1000-m Performance Time and Pacing in Elite Male and Female Endurance Runners
Authors: Boullosa Daniel , Abad César C.C. , Reis Valter P. , Fernandes Victor , Castilho Claudio , Candido Luis , Zagatto Alessandro M. , Pereira Lucas A. , Loturco Irineu 
Published: March 2020

Purpose: To evaluate the effect of drop jumps (DJs) on performance time and pacing in a field test (ie, 1000 m) commonly used to evaluate endurance runners and to evaluate running and jumping performance in male and female athletes separately. Methods: Twenty elite endurance runners (male, n = 10, 27.8 [7.0] y, 62.3 [5.2] kg; female, n = 10, 25.9 [5.3] y, 51.7 [4.1] kg) competing in middle- and long-distance events participated in this study. After determination of the box height associated with the best reactive strength index, athletes randomly performed a warm-up with or without the inclusion of 5 DJs with the highest reactive strength index prior to a 1000-m track test. Performance time and pacing (250-m splits) were determined. Countermovement-jump heights at different time points and blood lactate concentration after running tests were also recorded. Results: A “possible” faster 1000-m time (162.4 vs 165.3 s) with a “very likely” faster first split (38.8 vs 40.3 s) was observed in male athletes in the DJ condition. In contrast, female athletes showed a “possible” slower running time (186.8 vs 184.8 s) and a “likely” greater blood lactate concentration after the 1000-m test in the DJ condition. Male and female athletes presented greater countermovement-jump performances after warm-up and running tests in both conditions. Conclusions: The inclusion of 5 DJs with the height associated with the best reactive strength index induced a “possible” improvement in 1000-m performance time in elite male endurance runners. The current protocol should be avoided in female athletes.
Trunk–Pelvis Kinematics Variability During Gait and Its Association With Trunk Muscle Endurance in Patients With Chronic Low Back Pain
Authors: Bagheri Rasool , Ebrahimi Takamjani Ismail , Pourahmadi Mohammad R. , Jannati Elham , Fazeli Sayyed H. , Hedayati Rozita , Akbari Mahmood 
Published: March 2020

The first purpose was to investigate the trunk muscle endurance, the second aim was to evaluate the trunk–pelvis kinematics during gait, and the third was to evaluate the relationship between trunk–pelvis kinematics and the trunk muscle endurance. Thirty participants (15 nonspecific chronic low back pain [NCLBP] and 15 healthy) were included. The authors first assessed trunk muscle endurance on endurance testing protocols. The authors next measured the trunk–pelvis kinematics during gait using a 3-dimensional motion capture system. Angular displacement, waveform pattern (CVp), and offset variability (CVo) were also examined. Statistical analysis revealed a significant difference in (1) the trunk muscle endurance and (2) sagittal, frontal, and transverse planes CVp between groups (P < .05). A significant moderate correlation was found between supine double straight-leg raise and frontal CVp (r = .521, P = .03) and transverse planes CVp (r = .442, P = .05). However, a significant moderate correlation was observed between prone double straight-leg raise and sagittal plane CVp (r = .528, P = .03) and transverse plane CVp (r = .678, P = .001). The relationship between (1) lower trunk extensor endurance with transverse and sagittal planes CVp and (2) lower abdominal muscle endurance with transverse and frontal planes CVp suggests that gait variability in these planes may result because of trunk muscle deconditioning accompanying NCLBP.