An experimental study on global contact stiffness of sandy particle layers under high loads in three body contact

An experimental study on the effects of oxygenated fuel blends and multiple injection strategies on DI diesel engine emissions

To determine the effectiveness of three different methods of ultrasound probe cleaning for the prevention of nosocomial infections. Experimental study. Radiology Department, the Aga Khan University Hospital, Karachi and Microbiology Department, JPMC, Karachi, from December 2006 to April 2007. A total of 75 culture swabs from ultrasound probes used for sonographic examinations of different body parts of patients were included in the study. Probes were prospectively randomized into three equal groups with 25 probes in each group. Culture was sent before and after using three different techniques of cleaning ultrasound probe, which included sterilized paper towel, 0.9% saline and swipe over with standard bath soap applied on group A (n=25), group B (n=25) and group C (n=25) respectively. Number of Colony Forming Unit (CFU) of bacteria were calculated on standard agar plate to find out the effectiveness of cleaning methods in reducing bacterial count from the ultrasound probe after the procedures. All samples were tested in single microbiology lab by using same bacterial growth media provided by same manufacturer. Kruskall Wallis, Jonchkheere-Terpstra and Wilcoxon sign rank tests were applied to find out statistical significance. There was a significant reduction in bacterial count after applying either of all three cleaning methods for ultrasound probe compared to count on the probes before cleaning (p<0.001), however, soap cleaning method was the most effective in decreasing bacterial count to the minimum level in comparison to other two methods (p<0.001). The overall reduction in pathogenic bacterial count after performing each cleaning method was 45%, 76% and 98% for paper cleaning, normal saline and soap cleaning method respectively. Cleaning ultrasound probe after performing each procedure is a cost-effective practice with potential of reducing nosocomial infections. Soap cleaning technique is the most effective method for reducing bacterial count acquired due to patients' body contact with the ultrasound probes.

Structural stiffness has been increasingly considered as a performance index or parameter indicating condition of structures in the fields of aerospace, civil, and mechanical engineering. In this paper, theoretical and experimental structural stiffness models are proposed, and random vibration responses of the structure are evaluated. As a demonstration, the proposed method is applied to a one-story frame structure generally used in many engineering applications, and the experimental results show that the structural stiffness increases as the thickness of girder augments. Due to the idealization and perfect column-girder joint conditions, the theoretically predicted structural stiffness value is always larger than that measured from the experiment. Since the experimental method includes all practical factors, the experimental values of structural stiffness represent real global stiffness of the structure. An empirical equation of structural stiffness for the one-story frame structure is thus obtained by fitting the experimental data. The experimental random vibration experiment is conducted and it demonstrates that the random vibration responses under the same excitation all decrease when the girder becomes thicker. The influence of crack damage in columns of the one-story frame on structural global stiffness and random vibration response is also experimentally investigated, and it shows that the structural stiffness reduces slightly when damage is present. For the example given where the damage locates at the midheight of columns and coincides with location of the inflection point, the local damage in the structure only imparts a little change on the structural global stiffness, and the random vibration responses of the intact and damage structures also exhibit little difference. The experimental structural stiffness model presented can be used to data-reduce the global structural stiffness from the random vibration experiment, and it can be in turn considered as a performance index to assess condition of or detect damage in the structures.

Summary This paper addresses experimental results on the strength of single-lap compositebondedjoints withdifferent manufacturingmethods and configurations. The joints were fabricated with 4 different methods; Co-curing with additional adhesive (CCA) and without additional adhesive (CCN) between composite adherends, Co-bonding (COB) and secondary bonding (SEB). Joints have 5 different overlap lengths(l), 3 different lay-up patterns and 4 different thicknesses(t), respectively. Width of the joints(w) is constant at 25.4 mm. A total of 389 single-lap specimens were tested in tension. In the test to examine the effect of manufacturing methods and overlap lengths, the joint CCN showed the highest failure loads at all the overlap lengths except for one case and was followed by the methods SEB, CCA and COB. When the ratio of l/w is 2.0, failure load of the CCA is slightly higher than CCN. Failure load of COB is always the lowest. In the test for the joint with different thicknesses as well, failure load of the joint CCN is the highest and the joint COB shows thelowestload. To investigatethe effect of lay-up patterns,the proportionsof the layers in 0˚, 45˚, 90˚ were changed in (1) (25/50/25),(2) (10/80/10)and (3) (50/40/10) keeping the similar thicknesses. In the patterns (1) and (3), the joint CCN fails at the highest loads. But in the pattern (2), CCA shows slightly higher load than CCN. With limited exceptions, CCN shows the highest failure loads for the most of the joints with various configurations. Test results also show the failure loads of the joints are closely related to failure modes. In most case, the joint showing cohesive failure is high and the delamination failure load is the next. The joints dominated by debonding fail at the lowest loads generally.

Legislations concerning emissions from heavy-duty diesel engines are becoming increasingly stringent. This requires conventional diesel combustion to be compliant using costly and sophisticated aftertreatment systems. Preferably, diesel–methanol dual-fuel is one of the suitable alternative combustion modes as it can potentially reduce the formation of nitrogen oxide and soot emissions which characterised the diesel mixing-controlled combustion. This is primarily due to the high latent heat of vaporisation and oxygen content of the methanol fuel. At high engine loads, however, the potential of diesel–methanol dual-fuel operation is constrained by the excessive combustion pressure rise rate and peak in-cylinder pressure, which limits both the engine efficiency and the percentage of methanol that can be used. For the first time, experimental studies were conducted to explore advanced combustion control strategies such as Miller cycle, exhaust gas recirculation, and intake air cooling for improving upon high load diesel–methanol dual-fuel combustion. Experiments were carried out at 1200 r/min and 18 bar indicated mean effective pressure on a single-cylinder heavy-duty diesel engine, which equipped with a high pressure common rail diesel injection, a methanol port fuel injection, and a variable valve actuation system on the intake camshaft. Results showed that the methanol energy fraction of a conventional diesel–methanol dual-fuel operation with a baseline intake valve closing timing was limited to 28%. This was due to the high combustion temperature at a high load which advanced the ignition timing of the premixed charge, resulting in high levels of pressure rise rate. The application of lower effective compression ratio and intake air temperature ( Tint) effectively decreased the compression temperature, which successfully delayed the ignition timing of the premixed charge. This allowed for a more advanced diesel injection timing to achieve improvement in the thermal efficiency and potentially enabled a higher methanol substitution ratio. Although the introduction of exhaust gas recirculation demonstrated very slight impact on the ignition timing of the premixed charge, a higher net indicated efficiency was observed due to a relatively lower local combustion temperature which reduced heat transfer loss. Moreover, the optimised diesel–methanol dual-fuel operation allowed a higher methanol energy fraction of 40% to be used at an effective compression ratio of 14.3 and Tint of 305 K and achieved the highest net indicated efficiency of 47.4%, improving by 3.7% and 2.6%, respectively, when compared to the optimised conventional diesel combustion (45.7%) and conventional diesel–methanol dual-fuel (46.2%). This improvement was accompanied with a reduction of 37% in nitrogen oxide emissions and little impact on soot emissions in comparison with the conventional diesel combustion.

The load in resistance training is considered to be a critical variable for neuromuscular adaptations. Therefore, it is important to assess the effects of applying different loads on the development of maximal strength and muscular hypertrophy. The aim of this study was to systematically review the literature and compare the effects of resistance training that was performed with low loads versus moderate and high loads in untrained and trained healthy adult males on the development of maximal strength and muscle hypertrophy during randomized experimental designs. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (2021) were followed with the eligibility criteria defined according to participants, interventions, comparators, outcomes, and study design (PICOS): (P) healthy males between 18 and 40 years old, (I) interventions performed with low loads, (C) interventions performed with moderate or high loads, (O) development of maximal strength and muscle hypertrophy, and (S) randomized experimental studies with between- or within-subject parallel designs. The literature search strategy was performed in three electronic databases (Embase, PubMed, and Web of Science) on 22 August 2021. Results: Twenty-three studies with a total of 563 participants (80.6% untrained and 19.4% trained) were selected. The studies included both relative and absolute loads. All studies were classified as being moderate-to-high methodological quality, although only two studies had a score higher than six points. The main findings indicated that the load magnitude that was used during resistance training influenced the dynamic strength and isometric strength gains. In general, comparisons between the groups (i.e., low, moderate, and high loads) showed higher gains in 1RM and maximal voluntary isometric contraction when moderate and high loads were used. In contrast, regarding muscle hypertrophy, most studies showed that when resistance training was performed to muscle failure, the load used had less influence on muscle hypertrophy. The current literature shows that gains in maximal strength are more pronounced with high and moderate loads compared to low loads in healthy adult male populations. However, for muscle hypertrophy, studies indicate that a wide spectrum of loads (i.e., 30 to 90% 1RM) may be used for healthy adult male populations.

Previous research indicates that the low temperature combustion (LTC) is capable of producing ultra-low nitrogen oxides (NOx) and soot emissions. The LTC in diesel engines can be enabled by the use of heavy exhaust gas recirculation (EGR) at moderate engine loads. However, when operating at higher engine loads, elevated demands of both intake boost and EGR levels to ensure ultra-low emissions make engine controllability a challenging task. In this work, a multifuel combustion strategy is implemented to improve the emission performance and engine controllability at higher engine loads. The port fueling of ethanol is ignited by the direct injection of diesel fuel. The ethanol impacts on the engine emissions, ignition delay, heat-release shaping, and cylinder-charge cooling have been empirically analyzed with the sweeps of different ethanol-to-diesel ratios. Zero-dimensional phenomenological engine cycle simulations have been conducted to supplement the empirical work. The multifuel combustion of ethanol and diesel produces lower emissions of NOx and soot while maintaining the engine efficiency. The experimental setup and study cases are described, and the potential for the application of an ethanol-to-diesel multifuel system at higher loads has been proposed and discussed.

Previous research indicates that the low temperature combustion (LTC) is capable of producing ultra-low nitrogen oxides (NOx) and soot emissions. The LTC in diesel engines can be enabled by the heavy use of exhaust gas recirculation (EGR) at moderate engine loads. However, when operating at higher engine loads, elevated demands of both intake boost and EGR levels to ensure ultra-low emissions make engine controllability a challenging task. In this work, a multi-fuel combustion strategy is implemented to improve the emission performance and engine controllability at higher engine loads. The port fueling of ethanol is ignited by the direct injection of diesel fuel. The ethanol impacts on the engine emissions, ignition delay, heat-release shaping and cylinder-charge cooling have been empirically analyzed with the sweeps of different ethanol-to-diesel ratios. Zero-dimensional phenomenological engine cycle simulations have been conducted to supplement the empirical work. The multi-fuel combustion of ethanol and diesel produces lower emissions of NOx and soot while maintaining the engine efficiency. The experimental set-up and study cases are described and the potential for the application of ethanol-to-diesel multi-fuel system at higher loads has been proposed and discussed.

It is well-known that laboratory subjects often do not play mixed strategy equilibrium games according to the equilibrium predictions. In particular, subjects often mix with the incorrect proportions and their actions often exhibit serial correlation. However, little is known about the role of cognition in these observations. We conduct an experiment where subjects play a repeated hide and seek game against a computer opponent programmed to play either a strategy that can be exploited by the subject (a naive strategy) or designed to exploit suboptimal play of the subject (an exploitative strategy). The subjects play with either fewer available cognitive resources (under a high cognitive load) or with more available cognitive resources (under a low cognitive load). While we observe that subjects do not mix in the predicted proportions and their actions exhibit serial correlation, we do not find strong evidence these are related to their available cognitive resources. This suggests that the standard laboratory results on mixed strategies are not associated with the availability of cognitive resources. Surprisingly, we find evidence that subjects under a high load earn more than subjects under a low load. However, we also find that subjects under a low cognitive load exhibit a greater rate of increase in earnings across rounds than subjects under a high load.

An experimental study is presented of flow control of the rotor wake in a rotor/stator axial compressor. The objective is to quantify the reduction in the stator forced response due to flow blowing from the rotor trailingedge. The experiment was conducted in a low-speed, large-scale axial compressor at both near-design and high time-mean blade loading. The blowing cases considered are 35, 72, and 105% of the nonblowing wake momentum defect, which ranges from 1.3 to 3.7% of the compressor mass flow at near-design loading. Instrumentation include slanted hot wire to acquire three-dimensional ensemble-averaged rotor wake profile and fast-response pressure gauges embedded within the stator blades at midspan. Results show that the development of the near wake (15% chord downstream of trailing edge) is very much loading dependent; the same amount of blowing momentum has an effect on the velocity defect at near-design loading but not at high loading. Farther downstream, trailing-edge blowing is effective in energizing the wake. The decrease in magnitude of transverse gust is essentially linear with the wake momentum increase due to the blowing flow. Data show reduction in the stator unsteady force amplitude for all blowing cases tested. With the wake momentum at 72% of that for the wakeless flow, force amplitude reduction of 25 and 35% are realized for the near-design and high loading cases, respectively.

Recently, the engineering structural ceramics as friction and wear components in manufacturing technology and devices have attracted much attention due to their high strength and corrosion resistance. In this study, the tribological properties of Si3N4/Si3N4 sliding pairs were investigated by adding few-layer graphene to base lubricating oil on the lubrication and cooling under different experimental conditions. Test results showed that lubrication and cooling performance was obviously improved with the addition of graphene at high rotational speeds and low loads. For oil containing 0.1 wt% graphene at a rotational speed of 3000 r·min−1 and 40 N loads, the average friction coefficient was reduced by 76.33%. The cooling effect on Si3N4/Si3N4 sliding pairs, however, was optimal at low rotational speeds and high loads. For oil containing 0.05 wt% graphene at a lower rotational speed of 500 r·min−1 and a higher load of 140 N, the temperature rise was reduced by 19.76%. In addition, the wear mark depth would decrease when adding appropriate graphene. The mechanism behind the reduction in friction and anti-wear properties was related to the formation of a lubricating protective film.

&lt;div&gt;The main objective of this study is to investigate the effect of pilot injection mass and timing on main combustion and engine emissions. The experiments have been conducted on a single-cylinder diesel engine at fixed engine speed with various loads. In the computational fluid dynamics (CFD) simulations of the combustion, only a segment of the cylinder was considered. A numerical multiphase simulation of the internal nozzle flow delivered the required initial conditions for the spray primary breakup model. For the combustion the ECFM-3Z model was employed with a two-stage autoignition model.&lt;/div&gt; &lt;div&gt;The measurements show that a pilot injection can reduce the nitrogen oxides (NO&lt;sub&gt;x&lt;/sub&gt;) emissions at low engine load. With higher engine loads an increase in the NO&lt;sub&gt;x&lt;/sub&gt; emission values was observed. The numerical investigation exhibited that the thermal nitrogen monoxide (NO) formation is a mixing-controlled process. The NO is formed generally in two different zones. The first one is located near the cylinder head. The interaction between the cylinder head and the bowl-guided spray leads to the formation of eddies, which enhance the jet-air mixing. The second region is in the piston bowl. The numerical simulation showed that a tumble is generated due to the spray-piston interaction. This tumble mixes the fuel in the piston bowl with fresh cylinder charge. The combustion at stoichiometric conditions and high temperature in these two zones induces the thermal formation of the NO.&lt;/div&gt; &lt;div&gt;Pilot injection affects the thermal NO by changing the ignition position of the main injection. At low loads, the pilot injection influences the ignition position of the main injection strongly, leading to different fuel-air-distribution in the combustion chamber. At these conditions, a small amount of the fuel burns under stoichiometric conditions, and thus a smaller amount of NO is generated. At higher loads, the influence of the pilot injection on the ignition position is small because the spray development is slower at higher gas densities. The equivalence ratio at the geometrical NO formation regions does not change with the pilot injection. The increase in the NO&lt;sub&gt;x&lt;/sub&gt; could be explained by the high gas temperature caused by the combustion of the pilot injection.&lt;/div&gt;

Research is divided as to what degree visually unattended objects are processed (Lachter et al., 2008; Carrasco, 2011). The hybrid model of object recognition (Hummel, 2001) predicts that familiar objects are automatically recognised without attention. However under perceptual load theory (Lavie, 1995), when objects are rendered unattended due to exhausted attentional resources, they are not processed. The present work examined the visual processing of images of everyday objects in a short-lag repetition-priming paradigm. In Experiments 1-3 attention was cued to the location of one of two objects in the first (prime) display, with the unattended sometimes repeated in the second (probe) display. ERP repetition effects were observed which were insensitive to changes in scale (Experiment 1) but sensitive to slight scrambling of the image (Experiment 2). Increasing perceptual load did not modulate these view-specific repetition effects (Experiment 3), consistent with the predictions of automatic holistic processing. In Experiments 4-7 a letter search task was used to render the flanking object image unattended under high load. In Experiment 5 distractor processing was observed in ERP even under high load. In Experiments 4, 6 and 7 a pattern of view sensitive/insensitive and load sensitive/insensitive repetition effects on RT (Experiment 4) and ERP amplitude (Experiments 6, 7) were observed that were difficult to interpret under either the hybrid model or perceptual load theory, but may reflect fast view-based and slow view-independent processing of objects. Overall, the properties of the view-sensitive repetition effects were generally consistent with those associated with the automatic/pre-attentive processing of the holistic route of the hybrid model. However, differences between the processing of objects rendered unattended via a spatial cue or perceptual load indicate that the bottom-up driven hybrid model and perceptual load theory may benefit from the consideration of the interaction of top-down biasing of processing (Tsotsos et al., 2008).

The present paper discusses the improvement brought about in the strength and thermal stability of the unidirectional glass fiber reinforced epoxy composites through the incorporation of nano TiO2. The hybrid nanocomposites are fabricated through wet lay-up technique and are cured under pressure and static loading at room temperature. The TiO2 is added in 1, 2, 3, 4 and 5 wt% in order to arrive at the optimum wt% of nano TiO2 for improvement in the desired properties such as bend strength, tensile strength and composite toughness. The uniform dispersion of nano TiO2 into the epoxy matrix is achieved by sonication method. It is observed that the mechanical properties improved for TiO2 addition up to 2 wt%. At 3, 4 and 5 wt% addition of nano TiO2 the mechanical properties deteriorated due to severe agglomeration of the nano TiO2 at higher loading. The agglomeration at higher loading is observed through the SEM and AFM images. The thermal stability of the hybrid nanocomposite is studied through thermogravimetric analysis and the results depicted an improved thermal stability at higher wt% addition of nano TiO2 . This is because of the retardant effect exhibited by TiO2 at higher wt loading to heat and oxygen. Hence, slowing down the thermal degradation of the composite.

Contact analyses have been conducted over more than one century starting with Hertz who analyzed normal frictionless elastic contact between half-spaces with small deformation. The phenomenon of two surfaces in contact is important in the field of tribology and has been studied my many researchers. Hollow roller bearings find wide applications owing to their lower inertia, better radial stiffness and cooler running. The preloading of the rollers ensures many superior operating characteristics such as higher radial stiffness, rotational accuracy and higher speed capability. For hollow roller method is available for the calculation of contact width and contact stresses and all other important terminologies which are available for the solid roller. This paper presents a numerical and experimental analysis of the contact interaction between two elastic bodies “Cylinder and Flat”. In the numerical analysis Hertz theory is used to determine contact width for elastic contact. Experimental investigation has been performed by footprint method which is used to analyze a real contact area between two bodies for applied loading conditions. A comparison with the numerical data is given to validate the experimental procedure. The test results are almost similar and very close with the numerical data. Using this experimental method elastic contact between hollow cylinder and flat has been studied. Finally in the present work modified Hertz equation was developed for the calculation of half contact width for hollow cylinder and cylinder/flat body contact.