bluuebunny/crossref_metadata_2025 huggingface dataset:
Paramedian incisional complications after prophylactic laparoscopy‐assisted gastropexy in 411 dogs
Authors: Baron Jessica K. , Casale Sue A. , Monnet Eric , Mayhew Philipp D. , Runge Jeffrey J. , Follette Christelle M. , Phipps Kevin , Powell Margaret E. , Reczynska Alicja I. , Squire Nathan T. , Barton Bruce A. , Berg John
Published: December 2019

Objective

To determine the frequency and types of paramedian incisional complications after prophylactic laparoscopy‐assisted gastropexy (LAG) in dogs and to evaluate potential risk factors for complications.

Study design

Multi‐institutional retrospective study.

Animals

Client‐owned dogs (N = 411).

Methods

Records for dogs that underwent single‐incision–port laparoscopy‐assisted gastropexy (SIPLAG) or multiple‐port laparoscopy‐assisted gastropexy (MPLAG) at five veterinary referral hospitals were reviewed. Information regarding signalment, surgical procedures, perioperative care, and incisional complications was collected. Follow‐up information was obtained by review of medical records and/or communication with owners. Potential risk factors for complications were examined statistically.

Results

Paramedian incisional complications were observed in 78 of 411 (19%) dogs. The most common complication was seroma formation, which occurred in 51 (12.4%) dogs. Surgical site infections were observed in 16 (3.9%) dogs, and dehiscence or development of excessive scar tissue at the incision site were each observed in nine (2.2%) dogs. Complications resolved with conservative treatment in 75 of 78 (96.2%) dogs and with surgical treatment in three of 78 (3.8%) dogs. The odds of complications were approximately twice as high in dogs undergoing SIPLAG than in dogs undergoing MPLAG (odds ratio, 2.03;P =.006).

Conclusion

Minor paramedian incisional complications, particularly seroma formation, were frequently observed after LAG. Most complications were successfully managed conservatively. Single‐incision–port laparoscopy‐assisted gastropexy was associated with a higher complication rate compared with MPLAG.

Clinical significance

Owners should be informed that there is a relatively high rate of minor paramedian incisional complications after LAG. The risk of complications appears to be higher for SIPLAG than for MPLAG.
Dynamic Control of Sensor and Actuator failures in Multivariable Distillation Column
Authors: Al-Shatri Ali H. , Ahmad Arshad , Oladokun Olagoke , Nyakuma Bemgba Bevan , Al-shanini Ali
Published: December 2019

This paper examines the impact of sensor and actuator failures in the operation of a multivariable distillation column. Several failure scenarios are evaluated including failures of sensors and actuators in various scales of magnitudes and durations. The results obtained illustrate the ability of process controllers in suppressing the impact of these unwanted events. Closed-loop dynamic responses of the process revealed capabilities of these controllers in dealing with upsets that are small in magnitude and duration. In the case of larger and longer process upsets, process controllers are not adequate in providing the necessary corrective measures. This leaves the necessary interventions to be taken by the plant operators, following alarms that would have been triggered in typical plant operation scenario.
Pemaknaan Naratif Pengalaman dalam Cerpen Melayu/Narrative Experiential Meaning-making in Malay Short Stories
Authors: Azmi Siti Norashikin , Hassan Hanita , Wan Fakhruddin Wan Farah Wani , Mohamad Nasir Zaliza
Published: December 2019

The experiential meaning-making in narrative can be studied by applying the Ideational Metafunction theoretical framework as introduced by Halliday. According to Halliday, the meaning-making can be realized by means of three Transitivity main elements found in clauses which are process, participants and circumstances. A study was conducted on three Malay short stories entitled ‘Catatan di Meja Makan’, ‘Anita’ and ‘Meneruskan Perjalanan’ by Zurinah Hassan to analyse the experiential meaning-making of narrative using Transitivity analysis from Systemic Functional Linguistics as the analytical framework. The findings of the Transitivity analysis on Malay short stories show that material process types are mostly found and followed by mental processes. This results in the most found participants are actors for material process types, whilst participants for mental processes are sensors. The findings also show that the participants for material processes can be living or non-living entities. The writer usually conveys the meaning of short stories in active forms, by which means active processes are used to illustrate the actions of participants in Malay short stories. The findings of this study are a contribution to the field of Malay language studies using the theoretical framework of Systemic Functional Linguistics, of which studies on Malay language using this theory are still lacking.
CORROSION BEHAVIOR OF REINFORCING STEEL IN RC SLAB CONTAINING CHLORIDES WITH PARTIAL REPLACEMENT OF CEMENT AS FLY ASH
Authors: Gupta Sristi Das , Sugiyama Takafumi , Islam Md Shafiqul
Published: December 2019

Steel reinforcement in concrete containing fly ash has been practically employed to RC structures in snowy cold region and coastal areas so that the durability of the structures against corrosion can be enhanced. In this research to make the compatibility with RC slab bridge sodium chloride solution of 10[WU1] % in concentration was applied on RC slab and corrosion development was monitored by electrochemical method. Applying fly ash in RC slab at two replacement levels of 15[WU2] % (F15) and 30% (F30) of cement the specimens were observed. The observation result verified that fly ash concrete showed longer period of corrosion initiation (ASTM C876) than normal reinforced concrete. The initiation period of corrosion was 4.5 and 6 times longer for F15 and F30 concrete than normal concrete, as well as 91 days strength of F30 concrete was about 14% higher that of norma concrete. Test result showed that fly ash has better influence on steel corrosion reduction than concrete cover increment. It was observed that fly ash concrete (F15 and F30) with 3 cm concrete cover has better corrosion resistivity than using 4 cm cover of non-fly ash concrete. Furthermore, using the same concrete cover (3 cm) it was found that the actual corrosion rate was decreased about 68 to 82% by adding fly ash 15 to 30% respectively compared to normal reinforced concrete. In addition, a significant attenuation in corrosion area in rebar between fly ash concrete and normal concrete was found. Based on actual corrosion area on rebar surface, actual corrosion current density was larger than corrosion current density found from non-destructive way. Moreover, further analysis was conducted for characterization of different corrosion products using Raman spectroscopy with 532 nm wave length. It revealed that the corrosion product (Oxides and Oxyhydroxides compound) were less in F15 and F30 concrete compared to normal concrete. Considering these results, the possibility of reduction of chloride induced corrosion in reinforced concrete structure using fly ash has confirmed.
First Language Acquisition, Developmental Errors in Vocabulary: A Case Study of a Four -Year- Old Iranian Child
Authors: Sadeghi Nastaran , Hashamdar Mohammad
Published: December 2019

This case study aims to discover the process of first language acquisition of a 4–year-old Iranian child. The focus of the research is on developmental errors the child has created in his language development, i.e. the words which are not correct. To do so, the researcher, during four months, observed and recorded the subject's produced strange words. The recording was done by two ways, Interval recording strategy and event sampling.Developmental errors or strange words are part of the learning process. These words are created due to different reasons. The research shows that during four months and in thirty three records, eleven strange words and expressions were produced. These eleven errors were investigated in this study in details. A table was presented by the researcher in which these errors were thoroughly described.
Comparison of Certain Physical Fitness Parameters in Young Football and Basketball Players
Authors: Akyüz Murat
Published: December 2019

This study was carried out in order to compare certain physical fitness parameters of young basketball and football players. Basketball players, who are playing in U16 league (n=12), and football players playing in U17 league (n=10) participated in the study voluntarily. Groups were separated into two as the basketball group (BG) and the football group (FG). BG has a body weight mean of 74.13±7.26 kg, a height mean of 187.50±7.03 cm, and an age mean of 16. FG has a body weight mean of 68.0±7.95 kg, a height mean of 178.4±5.31 cm, and an age mean of 17. Participants were applied performance tests, which are composed of sit and reach test, leg strength, hand grip strength, flexibility, 20 m sprint, and flamingo balance test among physical fitness parameters. Data obtained were analysed using SPSS 19.0 package program, and Mann Whitney U test was used to compare two groups. While there was no meaningful difference between strength and flexibility values (p>0.05), a meaningful difference occurred in favour of FG in 20 m speed test (p<0.05). As a result, the difference that occurred in speed only makes us think that height and body weight in basketball players can impact speed and agility negatively compared to football players.
An Eddy-Viscosity Model Sensitized to Curvature and Wall-Roughness Effects for Reynolds-Averaged Closure
Authors: Zhang Yang , Chen Gang , Xu Jiakuan
Published: December 2019

This paper presents a new extension of the realizable K−ε model that accounts for streamline curvature, system rotation, and surface roughness. The model is a type of realizable K−ε model, but the transport equations and the eddy-viscosity damping functions are modified, based on the Richardson number and roughness height; the roughness correction covers both the transitional and fully rough regimes. Flows in a rotating channel and a U-bend duct are used to validate the response of the new model to the system rotation and streamline curvature. The flow in a plane channel and the flow over a dune are used to validate the roughness extension. Finally, a rotating channel with rough walls is studied, to test the new model when both rotation and roughness are present.
Spatiotemporal Evolution of Rotational Natural Cavitation in Rotational Supercavitating Evaporator for Desalination
Authors: Zheng Zhi-Ying , Wang Lu , Cai Wei-Hua , Zheng Xin , Li Qian , Kunugi Tomoaki , Li Hui , Li Feng-Chen
Published: December 2019

A novel desalination device named rotational supercavitating evaporator (RSCE) has been proposed and designed by utilizing supercavitation effect. With special focus on the spatiotemporal evolution of rotational natural cavitation, the hydrodynamic characteristics of cavitating flows in RSCE under different rotational speeds are studied by the visualization experiments and three-dimensional steady numerical simulations. The results of the visualization experiments show that with increasing rotational speed, the cavity morphology develops from several transient isolated bubbles moving with the blades, to blurred partial cavity, and finally to transparent supercavity with nearly constant size. Numerical simulation can predict the development of the cavity morphology in the experiment qualitatively and quantitatively. Vapor phase structures are shed at the tail of the cavity due to the reentrant jet, which are in the forms of single smaller bubbles and U-shaped vapor phase structures under lower rotational speeds and of cavitation clouds and cavitating filaments containing strings of bubbles under higher rotational speeds. Vortex structure is captured based on Q-criterion and encloses the cavity in the radial direction, wherein the periphery of the cavity is enclosed by a single tip vortex tube which can explain the generation of drifting stripe-shaped cavity under higher rotational speeds due to tip vortex, and the cavity tail is enclosed by two vortex tubes split from the single tip vortex tube. A power-law empirical formula for the dimensionless supercavity length versus the cavitation number considering the effect of rotation is obtained by fitting the experimental data on fully developed supercavitation.
Turbulent Properties of Triple Elliptic Free Jets With Various Nozzle Orientation
Authors: Morris Ella Marie , Aleyasin Seyed Sobhan , Biswas Neelakash , Tachie Mark Francis
Published: December 2019

An experimental investigation of nozzle orientation effects on turbulent characteristics of elliptic triple free jets was carried out for three nozzle configurations. The first configuration had each nozzle oriented along the minor plane (3_Minor), the next had two nozzles oriented along the minor plane and one along the major plane (Min_Maj_Min) and the last configuration had one nozzle oriented along the minor plane and two along the major plane (Maj_Min_Maj). The experiments were conducted using modified contoured nozzles with a sharp linear contraction for a nozzle spacing ratio of 4.1d, a nozzle equivalent diameter of 9 mm, and Reynolds number of 10,000. Nozzle orientation effects on the mean velocity, turbulent intensity, and Reynolds shear stress were discussed. The velocity decay, jet spread, merging point (MP), combined point (CP), and potential core length were used to characterize the effects of nozzle orientation on the mixing performance. The 3_Minor configuration had shorter potential core length and closer MP location which are indicative of a faster mixing in the converging region. The early merging of 3_Minor led to higher levels of streamwise turbulent intensity. One-dimensional plots revealed that jets approached self-similarity at a faster rate in the major axis. The orientation of the middle jet was found to be a key factor in determining transverse diffusion of the Reynolds shear stress in the plane of observation. Two-point correlations were used to provide insight into the effects of nozzle orientation on the spatial coherence of the large-scale turbulence structure and integral length scale.
Thermal Step Response of N-Layer Composite Walls—Accurate Approximative Formulas
Authors: Hagentoft Carl-Eric , Pallin Simon
Published: December 2019

For many industrial applications, heat flow through composites relates directly to energy usage and thus is of highest interest. For multilayer composites, the heat flow is a result of multiple variables, such as the temperature gradient over the surface boundaries and each material's thermal conductivity, specific heat, and thickness. In addition, the transient heat flux also depends on how the materials are aligned together. The heat flow through composites can be estimated using advanced computer simulations for applied heat transfer. Although these tools are powerful, they are also time consuming. Therefore, approximations that allow the estimation of heat flow through composites can be very useful. This paper presents approximations to solve transient heat transfer in multilayer composites, with and without an interior surface resistance. Since the energy use for various applications relates to the heat transferred at the surface boundary, the main focus of this paper is to define approximate solutions for interior heat flow. In other words, these approximations are found by applying a unit step change in temperature on one side of a composite and then in real-time emulating the surface heat flux on the opposite side from which the step change occurs. The approximations are presented based on lumped analyses and Laplace network solutions and are validated against analytical and numerical solutions.
Capillary Instability of Viscoelastic Liquid Film With Heat and Mass Transfer
Authors: Awasthi Mukesh Kumar
Published: December 2019

This paper examines the effect of transfer of heat and mass on the capillary instability between a viscoelastic liquid and a viscous gas. The viscoelastic liquid obeys the Oldroyd B-model. These two fluid layers considered in coaxial cylinders and viscoelastic–viscous potential flow theory are used for investigation. To study the stability of the interface, the normal-mode procedure is employed and a cubic dispersion equation in terms of growth rate has been obtained. We observe that the viscoelastic liquid–viscous gas interface is more unstable than the viscous liquid–viscous gas interface. Additionally, we show that the unstable axisymmetric wave modes are stabilized by allowing heat transfer at the interface.
Experimental Investigation of Forced Convection Enhancement by Acoustic Resonance Excitations in Turbulated Heat Exchangers
Authors: Gendebien Samuel , Kleiman Alex , Leizeronok Boris , Cukurel Beni
Published: December 2019

The present research deals with enhancing the thermal performance of turbulated heat exchangers through the application of sound pressure waves at acoustic resonance frequencies. Extending the findings of prior wind tunnel studies, where a standing wave greatly improved the forced convection in reattaching flows, this paper exploits such a phenomenon in a practical heat exchanger setting. The current experiments are conducted in representative turbulated plate and double-pipe heat exchanger geometries, mounted in a dedicated facility. After identifying the inherent acoustic resonance frequencies of the passageways, the impact of excitation is studied in various sound pressure levels, blockage ratios, as well as Strouhal and Reynolds numbers. The acoustic resonance excitation resulted in heat transfer enhancement of 20% and 10% in the plate and double-pipe designs, respectively, absence of additional pressure penalties. To the best knowledge of the authors, this is the first demonstration of acoustic forced convection enhancement in turbulated heat exchanger geometries. Such a technology can pave the way toward future designs that require low-pressure losses, minimal form factor, and/or process controllability.
Application of the Common-Feeding Injection System Layout to Light Duty Commercial Vehicle Diesel Engines
Authors: Ferrari A. , Jin Z. , Mittica A. , Vento O. , Zhang T. , Ouyang L. , Tan S.
Published: December 2019

The innovative Common Feeding (CF) fuel injection system has been designed for a light duty commercial vehicle diesel engine in order to reduce production costs and allow easy installation on the engine, compared to a traditional Common Rail system. In the CF apparatus, a delivery chamber with a volume around 10 cm3 is integrated in the high-pressure pump. The chamber at one side is connected to the pump, and at the other side is linked to the solenoid injectors by means of pipes (the rail is removed from the hydraulic circuit).

Experimental tests have been carried out on a hydraulic test rig at the Politecnico di Torino in order to compare the general performance of the prototypal CF system with that of a Common Rail (CR) system equipped with different rail volume sizes (realized by manufacturing rails of the same length but with different internal diameter). The injected mass flow-rates of single injections as well as of pilot-main injections have been captured by instantaneous flow-rate meters. In the case of the double injection schedules, the dependence of the injected mass pertaining to the second injection shot has been investigated during dwell time sweeps and design solutions have been provided to minimize the oscillations of such injected mass with respect to dwell time for the CF system.

Furthermore, the injector inlet pressure time histories, the static and dynamic injector leakages, the nozzle opening and closure delays and the injected volume cycle-to-cycle dispersion have been evaluated for both CR and CF systems.

In general, the injection performance of the injection systems with different hydraulic capacitances or shapes of the accumulator is similar. One significant difference is that the injection rate feature slightly different slopes during the rising phases. Furthermore, cycle-to-cycle dispersion in the injected mass increase to some extent when the accumulation volume of the high-pressure circuit is dramatically decreased. Finally, the frequencies of the free pressure waves that are originated by the water hammer, which occurs at the end of a hydraulic injection, are different when the shape of the accumulation volume change, whereas these frequencies are basically independent of the accumulation volume size.
A Comparison of Low-Load Efficiency Optimization on a Heavy-Duty Engine Operated With Gasoline-Diesel RCCI and CDC
Authors: Willems R. C. , Willems F. P. T. , Deen N. G. , Somers L. M. T.
Published: December 2019

Upcoming CO2 legislation in Europe is driving heavy-duty vehicle manufacturers to develop highly efficient engines more than ever before. Further improvements to conventional diesel combustion, or adopting the reactivity controlled compression ignition concept are both plausible strategies to comply with mandated targets. This work compares these two combustion regimes by performing an optimization on both using Design of Experiments. The tests are conducted on a heavy-duty, single-cylinder engine fueled with either only diesel, or a combination of diesel and gasoline. Analysis of variance is used to reveal the most influential operating parameters with respect to indicated efficiency. Attention is also directed towards the distribution of fuel energy to quantify individual loss channels. A load-speed combination typical for highway cruising is selected given its substantial contribution to the total fuel consumption of long haul trucks. Experiments show that when the intake manifold pressure is limited to levels that are similar to contemporary turbocharger capabilities, the conventional diesel combustion regime outperforms the dual fuel mode. Yet, the latter displays superior low levels of nitrogen oxides. Suboptimal combustion phasing was identified as main cause for this lower efficiency. By leaving the intake manifold pressure unrestricted, reactivity controlled compression ignition surpasses conventional diesel combustion regarding both the emissions of nitrogen oxides and indicated efficiency.
On the Effects of Injection Strategy, EGR, and Intake Boost on TSCI With Wet Ethanol
Authors: Gainey Brian , Yan Ziming , Rahimi-Boldaji Mozhgan , Lawler Benjamin
Published: December 2019

Using a split injection of wet ethanol, where a portion of the fuel is injected during the compression stroke, has been shown to be an effective way to enable thermally stratified compression ignition (TSCI), an advanced, low temperature combustion (LTC) mode that aims to control the heat release process by enhancing thermal stratification, thereby extending the load range of LTC. Wet ethanol is the ideal fuel candidate to enable TSCI because it has a high latent heat of vaporization and low equivalence ratio sensitivity. Previous work has shown “early” compression stroke injections (−150 to −100 deg aTDC) have the potential to control the start of combustion while “mid” compression stroke injections (−90 to −30 deg aTDC) have the potential to control in-cylinder thermal stratification, thereby controlling the heat release rate.

In this work, a mixture of 80% ethanol and 20% water by mass is used to further study the injection strategy of TSCI combustion. Additionally, the impact of external, cooled exhaust gas recirculation (EGR) and intake boost level on the effectiveness of a split injection of wet ethanol to control the heat release process are investigated. It was found that neither external, cooled EGR, nor intake boost level has any impact on the effectiveness of the compression stroke injection(s) at controlling the burn rate of TSCI. It was also seen that external, cooled EGR has the potential to increase the overall tailpipe combustion efficiency, while intake boost has the potential to decrease NOx emissions at the expense of combustion efficiency by lowering the global equivalence ratio.
Effect of Hydrogen and Carbon Monoxide Addition to Methane on Laminar Burning Velocity
Authors: Morovatiyan Mohammadrasool , Shahsavan Martia , Baghirzade Mammadbaghir , Mack J. Hunter
Published: December 2019

Exhaust gas recirculation (EGR) in spark-ignited engines is a key technique to reduce in-cylinder NOx production by decreasing the combustion temperature. The major species of the exhaust gas in rich combustion of natural gas are hydrogen and carbon monoxide, which can subsequently be recirculated to the cylinders using EGR. In this study, the effect of hydrogen and carbon monoxide addition to methane on laminar burning velocity and flame morphological structure is investigated. Due to the broad flammability limit and high burning velocity of hydrogen compared to methane, this addition to the gaseous mixture leads to an increase in burning velocity, less emissions production, and a boost to the thermal efficiency of internal combustion engines. Premixed CH4-H2-CO-Air flames are experimentally investigated using an optically accessible constant volume combustion chamber (CVCC) accompanied with a high-speed Z-type Schlieren imaging system. Furthermore, a numerical code is applied to quantify the laminar burning velocity based on the pressure rise during flame propagation within the CVCC. According to the empirical and numerical results, the addition of hydrogen and carbon monoxide enhances laminar burning velocity while influencing the flame structure and development.
Screening Compounds for Fast Pyrolysis and Catalytic Biofuel Upgrading Using Artificial Neural Networks
Authors: Kessler Travis , Schwartz Thomas , Wong Hsi-Wu , Mack J. Hunter
Published: December 2019

There is significant interest among researchers in finding economically sustainable alternatives to fossil-derived drop-in fuels and fuel additives. Fast pyrolysis, a method for converting biomass into liquid hydrocarbons with the potential for use as fuels or fuel additives, is a promising technology that can be two to three times less expensive at scale when compared to alternative approaches such as gasification and fermentation. However, many bio-oils directly derived from fast pyrolysis have a high oxygen content and high acidity, indicating poor performance in diesel engines when used as fuels or fuel additives. Thus, a combination of selective fast pyrolysis and chemical catalysis could produce tuned bioblendstocks that perform optimally in diesel engines. The variance in performance for derived compounds introduces a feedback loop in researching acceptable fuels and fuel additives, as various combustion properties for these compounds must be determined after pyrolysis and catalytic upgrading occurs. The present work aims to reduce this feedback loop by utilizing artificial neural networks trained with quantitative structure-property relationship values to preemptively screen pure component compounds that will be produced from fast pyrolysis and catalytic upgrading. The quantitative structure-property relationship values selected as inputs for models are discussed, the cetane number and sooting propensity of compounds derived from the catalytic upgrading of phenol are predicted, and the viability of these compounds as fuels and fuel additives is analyzed. The model constructed to predict cetane number has a test set prediction root-mean-squared error of 9.874 cetane units, and the model constructed to predict yield sooting index has a test set prediction root-mean-squared error of 13.478 yield sooting index units (on the unified scale).
Novel Engine Cycle Enabling Partial Load Fuel Efficiency Beyond Full Load Conditions
Authors: de Jong Arjen
Published: December 2019

Fuel consumption reduction and emission reductions in internal combustion engines (ICE) is a hot topic nowadays. An adaption of cylinder de-activation technique called ECONAMIQ over-expansion can be applied to engines to improve fuel efficiency. Using the pressure from the exhaust gas from the active cylinders, the ‘idle’ cylinders could be expanded to extract more work out of the engine during partial load operation. Using the virtual simulation environment GT-Power, this cycle is applied to a 4-cylinder SI engine. This engine model is simulated for a part load operation point and compared with a standard 4-cylinder engine model and 4-cylinder engine model equipped with cylinder de-activation. From these simulations various variables for engine operation (valve timing etc.) are optimized to further reduce fuel consumption of the engine. A final brake specific fuel consumption reduction of over 10% is achieved using the overexpansion cycle, while improving engine performance on two burning cylinders over 10% as well. With this improvement it is shown that the over-expansion cycle has a significant benefit compared to a standard ICE and cylinder de-activation techniques. These simulations are being validated on an engine test dyno using a natural aspirated ICE.
Air Fuel Dilution in a Pilot Ignited Direct Injection Natural Gas Engine: Pollutants, Performance, and System Level Considerations
Authors: Singh Aditya Prakash , McTaggart-Cowan Gordon Patrick , Kirchen Patrick
Published: December 2019

Dilution of natural gas fuel with air for use in a pilot ignited direct injection natural gas engine was investigated to evaluate the impact of this strategy on emissions and engine performance. A representative heavy-duty mode (mid to high-load at medium speed) was considered and the equivalence ratio (Φ) and exhaust gas recirculation (EGR) rates were varied from this representative mode. Air dilution resulted in a significant reduction in several pollutants: 90 to 97% reductions in black carbon particulate matter, 45 to 95% reductions in carbon monoxide, 68 to 85% reductions in total unburnt hydrocarbons. NOx emissions were found to increase by between 1.5 and 2.5x, depending on Φ and EGR, for a fixed combustion phasing. Beyond the emissions improvements, the gross indicated thermal efficiency increased by 2.5 percentage points at both high and low EGR rates. At higher EGR rates, this improvement was due to improved combustion efficiency, while the mechanism for efficiency improvement at lower EGR rates was unclear. The application of air-fuel dilution requires compressed air (> 300 bar) to mix with natural gas at high pressures. A system level analysis considered the compression power required by an industrial 3-stage reciprocating compressor and indicated that the gross indicated thermal efficiency improvements could compensate for the compression requirements for engine operation at high Φ.
Direct Measurement of Ammonia Storage on Passive SCR Systems for Lean Gasoline NOx Reduction Using Radio Frequency Sensing
Authors: Ragaller Paul , Mandelbaum Josh , Lapenta Luc , Sappok Alexander , Pihl Josh , Prikhodko Vitaly , Parks James
Published: December 2019

Lean gasoline engine operation provides clear efficiency benefits relative to conventional stoichiometric combustion approaches. One of the key hurdles to the widespread, practical implementation of lean gasoline combustion remains the challenge of lean NOx control. One of the potential approaches for controlling NOx emission from lean gasoline engines is the so-called passive selective catalytic reduction (SCR) system. In such systems, periods of rich operation generate ammonia over a three-way catalyst (TWC), which is then adsorbed on the downstream SCR and consumed during lean operation. Brief periods of rich operation must occur in response to the depletion of stored ammonia on the SCR, which requires reliable measurements of the SCR ammonia inventory. Presently, lean exhaust system controls rely on a variety of gas sensors mounted up- and downstream of the catalysts, and which only provide an indirect inference of the operation state.

In this study, a radio frequency (RF) sensor was used to provide a direction measurement of the amount of ammonia adsorbed on the SCR in real-time. The RF sensor was calibrated and deployed on a BMW N43B20 4-cylinder lean gasoline engine equipped with a passive SCR system. Brief periods of rich operation performed at lambda values between 0.98 and 0.99 generated the ammonia, subsequently stored on the SCR for consumption during periods of lean operation. The experiments compared real-time measurements of SCR ammonia inventory from the RF sensor with estimates of ammonia coverage derived from exhaust gas composition measurements upstream and downstream of the catalyst. The results showed a high degree of correlation between the RF measurements and SCR ammonia storage inventory, and demonstrated NOx conversion efficiencies above 98%, confirming the feasibility of the concept. Relative to stoichiometric operation, lean-gasoline operation resulted in fuel efficiency gains of up to 10%, which may be further improved through direct feedback control from the RF sensor to optimize lean–rich cycling based on actual, measured SCR ammonia levels.
Optimization of High Pressure Direct Injection Micro-Pilot As a Retrofit Technology for Conventional Dual Fuel Engines
Authors: Beshouri Greg , Fischer Gerry
Published: December 2019

In the late 1980’s Enterprise Engine Company performed a single cylinder test of micro-pilot high pressure direct injection as a retrofit technology for conventional dual fuel engines. While that testing demonstrated a number of benefits for this technology, non-technical considerations led to the use of low pressure Pre-Combustion Chamber (PCC) micro-pilot technology as the retrofit technology instead. Thirty years later, when the automotive components of the PCC micro-pilot system were no longer available, the opportunity again arose to test the capabilities of an off the shelf high pressure direct injection micro-pilot system as a retrofit technology for a conventional dual fuel engine.

Single cylinder and full engine testing of the high pressure direct injection micro-pilot injection confirmed the results of the 1980’s testing. The test results also corroborated modern analytical and experimental testing of high pressure pilot technology. In particular, the interaction between the diesel pilot and primary fuel gas charge is very complex and sometimes counterintuitive. Likewise performance optimization requires careful balance of injection timing, injection quantity and fuel gas air/fuel ratio. Even then, exhaust gas methane emissions remain counterintuitive.

This paper reviews modern single cylinder and full engine test results focusing on optimization parameters for high pressure direct injection micro-pilot for retrofit and new engine applications.
A Statistical Study to Evaluate the Performance of Liquid Cooling Garments Considering Thermal Comfort
Authors: Shu Weicheng , Wang Jiawen , Zhang Xinfeng , Luo Xiaobing
Published: December 2019

Liquid cooling garments (LCGs) are considered a feasible cooling equipment to protect individuals from hyperthermia and heat-related illness when working in extremely hot and stressful environments. So far, the goals for optimization design of LCGs are mostly from the perspective of enhancing its efficiency and duration working time. However, thermal comfort is the key factor which is often not considered. In fact, there are many situations that may cause discomfort. For example, as the ice melts, the inlet temperature of the liquid cooling vest changes constantly resulting in the change of thermal states of the human body, which lead to discomfort of human. So, it is very significative to develop a method to evaluate the performance of LCGs considering thermal comfort. In this paper, an uncomfortable time ratio was proposed to evaluate the performance of LCGs considering thermal comfort. It defined the proportion of uncomfortable time including overcooling and overheating in the entire working time. Series of tests were conducted by a modified thermal manikin method to evaluate the thermal properties. According to the analyses, the duration working time was 82.77 min, while the uncomfortable time ratio was too large, up to 57.6 %. It showed that the requirement of comfort should be considered when optimizing the performance of LCGs. The influences of different parameters such as the volume of ice, flowrate, inlet temperature on the performance of LCGs were investigated through orthogonal experimental design. The statistical analysis illustrated that the influence of the volume of ice on the uncomfortable time ratio is greater than that of flowrate and ambient temperature. It is concluded that this method is useful for the control and design of LCGs considering thermal comfort.
Optimal Arrangement of Multiple Heat Sources in Vertically Stacked Two-Layer 3-D IC Using Genetic Algorithm
Authors: Rangarajan Srikanth , Hadad Yaser , Choobineh Leila , Sammakia Bahgat
Published: December 2019

The semiconductor packaging technologies have seen its growth from MCM (Multi-chip module), SiP (System in Package), SoC (System on Chip) to the heterogeneous integration of the MCM. Thermal management of multi-chip vertically integrated systems poses additional constraints and limitations beyond those for single chip modules. 3-D integrated circuits (3-D ICs) technology is a potential approach for next-generation semiconductor packaging technologies. A 3-D IC is formed by vertical interconnection of multiple substrates containing active devices which offer reduced die footprint and interconnect length. This manuscript discusses the optimal arrangement of two hotspots on each layer of a two-die stacked 3-D IC. An analytical heat transfer model for prediction of three-dimensional temperature field of a 3-D IC based on the solution of governing energy equations has been developed and used for this study. The model is subject to adiabatic boundary conditions at the walls except for the bottom wall which is subject to convective boundary condition. Genetic Algorithm is employed for solving two non-conflicting objectives constrained optimization problem. The first objective aims to minimize the maximum temperature on both layers, the second objective aims to achieve temperature uniformity in the layers. A feed-forward back propagation Artificial Neural Network (ANN) is employed for obtaining the functional relationship between the location of the hotspots and the objectives. The results of the optimization study are expected to provide recommendations on the design guidelines for arranging hotspots on vertically stacked substrates.
Evaluation of Low Order Stress Models for Use in Co-Design Analysis of Electronics Packaging
Authors: Boteler L. M. , Miner S. M.
Published: December 2019

Co-design and co-engineering have the potential to improve the design of electronics packaging significantly. A co-designed approach moves away from the sequential approach of an electrical layout followed by a mechanical module design, and then the addition of a heat sink. Replacing it with an approach that addresses the electrical, thermal, and mechanical design simultaneously during the initial design. The goal is to evaluate the design space quickly, considering both the thermal and mechanical stress aspects together. ParaPower is a low order fast running parametric analysis tool, developed by the Army Research Laboratory (ARL), that allows rapid evaluation of package temperatures and coefficient of thermal expansion (CTE) induced stresses throughout the design space. The model uses a 3D nodal network to calculate device temperatures and thermal stresses. In order to rapidly evaluate the design space both the thermal and stress models must be reduced order and provide reasonable results on coarse grids. In the case of the stress model, the goal is a low order relationship between the temperatures and the CTE induced stresses. This paper compares three different low order models for stress. The first uses a more traditional planar module design. This assumes a substantial substrate or heat spreader as the base for the module assembly. The second model is less restrictive, eliminating the requirement for a substrate. The third model also eliminates the substrate requirement, but also allows for in-plane distribution of the stresses. The first two models do not account for the in-plane distribution. Two geometries are considered, a standard power module with a substantial substrate and a stacked novel module with no clear substrate layer. Results for both geometries and the three stress models are compared to finite element analysis (FEA) using SolidWorks, beginning with a thermal analysis followed by a stress analysis based on the temperature solution. All three models run roughly two orders of magnitude faster than the FEA and they correctly predict the trends in the CTE induced stresses.
Evaluation of a Lead Glass for Encapsulating High-Temperature Power Modules for Aerospace Application
Authors: Liu Lanbing , Nam David , Guo Ben , Burgos Rolando , Lu Guo-quan
Published: December 2019

Encapsulation is a big challenge for packaging high-temperature power modules due to limited choices of insulation materials that can be easily processed and have high reliable working temperature of over 250°C. In this work, we evaluated a lead glass as a potential high-temperature encapsulant for protecting SiC power chips interconnected on a common Al2O3 direct-bond-copper (DBC) substrate. To avoid glass cracking due to its high elastic modulus and mismatched coefficient of thermal expansion (CTE) with that of the DBC substrate, we added a polyimide buffer layer between the glass and the substrate to reduce thermomechanical stresses. We found that the buffer layer was effective in reducing cracks in the glass, but it also lowered the breakdown and partial discharge inception field strengths. Single-chip SiC MOSFET packages were fabricated using the glass encapsulant to demonstrate its feasibility for high-temperature encapsulation.
Correlated Effects of Self-Heating, Light Output, and Efficiency of GaN Light-Emitting Diodes on Junction Temperature
Authors: Chatterjee Bikramjit , Lundh James Spencer , Shoemaker Daniel , Kim Tae Kyoung , Kwak Joon Seop , Cho Jaehee , Choi Sukwon
Published: December 2019

With the advent of GaN as the major material system in the solid-state lighting industry — high power, high brightness LEDs with wavelength ranging from near UV to white are getting fabricated and part of a tremendously large and ever-increasing market. However, device self-heating and environment temperature significantly deteriorates the LED’s optical performance. Hence, it is extremely important to quantify the device self-heating and its impact on optical performance. In this work, three different characterization techniques were used to calculate temperature rise due to self-heating for an InGaN/GaN LED with 5 pairs of multiple quantum wells. The impact of self-heating and increased environment temperature on the device optical performance were also studied. Nanoparticle assisted Raman thermometry was used for the first time to measure the LED mesa surface temperature. The temperature measured using this technique was compared with temperature data obtained by using the forward voltage method and infrared (IR) thermography. The IR and Raman measurement results were in close agreement while the temperature data obtained from forward voltage method underestimated the temperature by 510%. It was also observed that due to environment temperature increase from 25°C to 100°C, LED optical power output drops by 12%.
Comparative Study on Power Module Architectures for Modularity and Scalability
Authors: Lu Mei-Chien
Published: December 2019

Silicon carbide wide bandgap power electronics have gained application spaces in hybrid electric vehicle and electrical vehicles. The Department of Energy has set target performance goals for 2025 to promote electric vehicles and hybrid electric vehicles as a means of carbon emission reduction and long term sustainability. Silicon carbide technology is well suited to reach these goals. Challenges include higher expectations on power density, performance, efficiency, thermal management, compactness, cost, and reliability. This study will benchmark state of the art silicon and silicon carbide technologies. Power modules of commercial traction inverters are analyzed for their within-package interconnect scheme, module architecture, and cooling methods. A few power module package architectures from both industry adopted standards and proposed patented technologies are compared for modularity and scalability for integration into inverters. The within package interconnect schemes are crucial elements to support power module design. Current trends of power module architectures and their integration into inverter are discussed. The development of an eco-system to support the transition from silicon-based to silicon carbide-based power electronics is additionally discussed as an ongoing challenge.
Comparative Evaluation of Algorithms for Achieving Ultrapacked Thermal Greases: Microstructural Models and Effective Behavior
Authors: Achar P. L. Sukshitha , Liao Huanyu , Subbarayan Ganesh
Published: December 2019

As device power density increases, there is a need to dissipate generated heat by increasing particle volume loading in thermal interface materials. In this work, we develop and evaluate algorithms for generating ultrapacked microstructures of particles. Simulated microstructures reported in the literature rarely contain particle volume fractions greater than 60%. However, commercially available thermal greases claim to achieve volume fractions in the range of 60–80%. Therefore, to analyze effectiveness of commercially available particle-filled thermal interface materials, there is a need to develop algorithms capable of generating ultrapacked microstructures. The particle packing problem is initially posed as a nonlinear programming problem (NLP), and formal optimization algorithms are applied to generate microstructures that are maximally packed. Since accuracy of the simulated behavior is dependent on the number of particles in the simulation cell, efficiently simulating large number of particles is imperative. However, the packing simulation is computationally expensive. Therefore, various optimization algorithms are systematically evaluated to assess the computational efficiency as measured by the time to generate the microstructures for a system containing a large number of particles. The evaluated algorithms include the penalty function methods, best-in-class sequential programming method, matrix-less conjugate gradient method as well as the augmented Lagrangian method. In addition, heuristic algorithms are also evaluated to achieve computationally efficient packing. The evaluated heuristic algorithms are mainly based on the Drop-Fall-Shake method, but modified to more effectively simulate the mixing process in commercial planetary mixers. With the developed procedures, Representative Volume Elements (RVE) with volume fraction as high as 74% are demonstrated. The simulated microstructures are analyzed using our previously developed random network model to estimate the effective thermal and mechanical behavior given a particle arrangement.