Varied Ambient Conditions Research Articles

Influence of ambient conditions on the marine two-stroke engine integrated with a bottoming Rankine cycle system: Energy and exergy analyses

The varied ambient condition brings challenges to highly efficient operation of the marine engine especially when a bottoming Rankine cycle system is integrated. However, few theoretical studies on it were reported. This paper aims at providing a comprehensive energy and exergy study on the marine two-stroke engine and its integrated bottoming Rankine cycle operating at different ambient temperatures. First, the thermodynamic processes of the combined cycle power plant and its tuning methods are described in detail, followed by model building and validation. Parametric studies on the combined cycle power plant operating under varied ambient conditions are then performed from energy and exergy perspectives. It is concluded that the high-pressure tuning can effectively control the scavenging process under varied ambient conditions but has a limited effect on the exergy distributions of the marine engine. With the bypass tuning, every 10 °C rise in the ambient temperature requires a decrease of the bypass ratio by 2% in absolute, which increases the exhaust gas temperature by only 5 °C compared to that of 16 °C in the base engine case. In the bottoming Rankine cycle system, the optimum evaporation pressure is mainly determined by the exhaust temperature rather than the ambient temperature. The fuel-saving potential of the combined cycle with the power turbine tuning reaches up to 7% and is deteriorated with the increasing ambient temperature.

Survivability of a particle laden sessile coughed and sneezed droplet subjected to different ambient conditions

The present work analyzes the survival of particle laden coughed and sneezed droplets under the influence of different weather conditions. Firstly, the impact of ambient conditions on the evaporation kinetics of a droplet containing fluorescent particles placed on a hydrophobic surface (akin to human skin which has low surface energy) is explored. The experimental situations are chosen accordingly so as to imitate the scenario of the evaporation of virus contaminated saliva droplets being ejected on human skin. Following the micro-Particle Image Velocimetry analysis, the internal dynamics of the droplet subjected to varied ambient conditions are quantified. Secondly, through both the theoretical and experimental investigations, the temporal loss of droplet volume being subjected to diverse atmospheric conditions is explored. Lastly, it has been demonstrated that the stress being generated inside the droplet due to the development of the internal flow velocities, becomes significantly higher at a higher wind velocities. The higher stress may endorse a situation leading to the possibility of disruption of the virion lipid membrane (for a case pertaining to the virus laden droplet).

Robust children’s speech recognition in zero resource condition

User applications such as voice-based web search, online learning, and video gaming require an effective speech recognition module to take user commands. Nowadays, even children are frequently using such tools, especially for online learning and gaming. This has increased the demand for developing a noise-robust automatic speech recognition (ASR) system that can effectively transcribe children’s data under varied ambient conditions. However, automatic recognition of children’s speech is extremely challenging due to the insufficiency of data from child speakers in the majority of the languages across the world. Consequently, in this zero-resource condition, we are forced to decode children’s speech on systems trained using adults’ data. However, the acoustic mismatch between adults’ and children’s speech, such as differences in pitch, formant frequencies, and speaking-rates, leads to highly degraded recognition performance. To enhance the recognition rate under zero-resource conditions, we have explored the role of formant and duration-modification-based out-of-domain data augmentation in this paper. For that purpose, the formant frequencies of the adults’ speech data are upscaled using warping of linear predictive coding coefficients. On pooling original and formant modified adults’ speech data into training, the mismatch in formant locations is reduced leading to better recognition performance. Further improvement in recognition rate can be achieved by simultaneously modifying the duration as well as the formant frequencies of the training data. This case of out-of-domain data augmentation has also been studied in this work and found to yield added gains. In addition to data augmentation, a noise- and pitch-robust front-end acoustic feature extraction approach exploiting higher-order spectral analysis (simple and cross-bispectrum) is also proposed in this paper. The proposed features are noise-robust due to the inherent immunity of the bispectrum towards additive noises. An added advantage of bispectrum is reduced pitch sensitivity as demonstrated in this work. This, in turn, helps alleviate the aforementioned pitch-induced acoustic mismatch. The experimental evaluations presented in this paper demonstrate that the use of proposed acoustic features, as well as the out-of-domain data augmentation techniques, are highly suited for zero-resource children’s speech recognition tasks under clean and noisy conditions.

Experimental investigation on VCRS by using R-134a and R-410a of air and evaporative cooled condenser

In this study, experimental research is carried out on two different class of refrigerants at three varied ambient conditions viz. (30°C, 35ºC and 40ºC) and three different air velocities viz. (1.25, 1.00, 0.75 m/s) in air cooled and evaporative cooled condenser. The first class is of low temperature refrigerant (R-134a) and the second is of high temperature refrigerant (R-410a). The results described that COP of high temperature refrigerant is greater than that of low temperature refrigerant. The COP increased with increasing air speed in air cooled and evaporative cooled condenser and decreased with increasing the ambient temperatures. For a fixed ambient temperature and air velocity, the COP of R-410a turned out to be greater than the COP of R-134a.Thus proving that high temperature refrigerant is better in performance than low temperature refrigerant.

Assessment of Compost Stability Using Single and Mixed Culture in a Static Semi-closed Fed-batch Reactor

Different microbial inoculums are expected to affect the degradation and stability of different compost materials. The results tend to vary more significantly in an open system due to the varied ambient conditions (temperature, moisture and air-borne microbial). To minimise such variation and avoid low reproducibility of the data, the present work was performed in a static semi-closed fed-batch reactor (SSCFBR) for better control of the composting process. The thermophilic Bacillus coagulans (BC) and the commercial effective microorganisms (EM) were used as the microbial inoculum (MI) in the SSCFBR. Distilled water was used in place of the MI for the control experiments. The mixture of chicken dung (CD), wooden husk (WH), and rice husk (RH) were used as the compost materials. The MI was inoculated into the compost bed in the SSCFBR (15 L working volume) at the same initial optical density (OD) of 0.8 and the initial volume of 800 mL with a forced aeration of 0.4 L/min. The parameters for the assessment of compost stability included the temperature, moisture content, oxygen uptake rate (OUR) and carbon dioxide emission rate (CER). BC showed comparable or better results to that achieved by the commercial EM. The temperature profile for both composts showed similar patterns where the highest peak of temperature was recorded within 1 d of composting (slightly higher for BC, 55 ± 0.8 °C and 47 ± 0.8 °C for EM). Such thermophilic temperature profile has not been observed in the control. The initial moisture content was set similar for all composts (44.5 ± 0.7 %). The moisture content declined slightly different for both MI compost (to 39.0 ± 0.6 % for BC and 36.6 ± 1.2 % for EM). Both composts showed very similar trend in the OUR. A higher evolution rate of carbon dioxide (CO2) was observed for the compost with BC for the first three days (0.06 ± 0.014 g/mol) as compared to that by EM (0.02 ± 0.007 g/mol). On the 4th d of composting, the production of CO2 in EM compost showed a near constant value (0.008 ± 0.002 g/mol) but the BC compost showed the rate of 0.06 ± 0.01 g/mol the 5th d and declined to 0.02 ± 0.004 g/mol on the 7th d. For both composting cases, the highest rate of CO2 was observed at the highest peak of temperature. The SSCFBR has been designed and could be used to facilitate the assessment of compost stability in a closed system with improved reproducibility of the data for composting.

Laser-Based Joining of Thermoplastics to Metals: Influence of Varied Ambient Conditions on Joint Performance and Microstructure

Laser-based joining of thermoplastics to metals shows a great potential for functional design especially in terms of lightweight constructions. In the joining process, the joining speed and the energy per unit length, respectively, show an influence on time-temperature profiles measured in the joining zone. The time-temperature profile affects the joining zone and consequently the joint behavior in mechanical testing. In the current investigation, the joining zone was characterized by the melting layer. Moreover, the mechanical properties of the joint by tensile shear testing and the fracture mode were investigated. Based on the results obtained, three sets of joining speeds/energies per unit length with different mechanical behaviors were selected for further investigations under varied ambient conditions. Thereby, the influence of outdoor weathering as well as aging above the glass transition temperature of the plastic part on the joint’s performance was compared with the nonaged joints.

An Experimental Study to Evaluate the Effect of Ambient Temperature during Manual Lifting and Design of Optimal Task Parameters

AbstractIn the present study, the effect of lifting task parameters on the heart rate and oxygen uptake of workers during manual lifting tasks in different ambient conditions was evaluated. The experiments conducted in two different temperature conditions showed a significantly higher oxygen uptake and heart rate in colder conditions as compared to warmer conditions. Three other factors, namely, load, lifting frequency, and vertical distance were found to significant affect the responses. Various combinations of significant factors were used to calculate oxygen uptake and heart rate. These were then compared with the safe limits as per the maximum aerobic capacity of workers. Based on these comparisons, the safe combinations were identified that can be used to design lifting tasks in varied ambient conditions. The study further concluded that lifting tasks performed in winter should have different relaxation or fatigue allowances built into the cycle time of the task to compensate for higher exertion. © 2011 Wiley Periodicals, Inc.

On the optimization of sphalerite bioleaching; the inspection of intermittent irrigation, type of agglomeration, feed formulation and their interactions on the bioleaching of low-grade zinc sulfide ores

In this study, we have investigated the bioleaching potential of a native strain of Acidithiobacillus ferrooxidans isolated from zinc and lead sulfide mines under varied ambient conditions of growth and substrate consumption. The effects of intermittent irrigation, type of agglomeration, feed formulation in terms of acid, enriched salt solution, initial number of microorganism, and their interactions on the bioleaching of low-grade zinc sulfide ores (containing 5.78% zinc) on growth and biooxidation efficiency of the bacteria have been evaluated. Bioleaching capacities of the isolate were optimized by the utilization the Taguchi method (e-qualitic-4) for design of experiments. As a result, eight column bioreactors with 5.7kg ore (100% <12mm) capacity were fabricated. Through the analysis, continuous inoculation of the ores with the solution of A. ferrooxidans type and spraying a bacterial-rich solution into the agglomerator were found to be the most significant factors, whereas intermittent irrigation and interactions of parameters have less effect within the ranges investigated. The extraction of zinc was obtained under the optimal conditions more than 70% in 80 days, which is noticeable to compare with conventional bioleaching.

“Anchor effect” in poly(styrene maleic anhydride)/TiO2 nanocomposites

Multi-component composites or hybrid materials of inorganic matter and organic polymers have been reported recently [1–3]. It is well known that styrene and maleic anhydride usually copolymerize in an alternating way, resulting in a poly(styrene maleic anhydride) (PSMA) alternating copolymer with highly regular anhydride groups on backbone chains which may provide regular sites for combination with other substances. Nanocomposites of inorganic materials in organic matrices are of a particular interest, which combine typical properties of organic polymers (e.g., elasticity, transparency or specific absorption of light, dielectric properties) with the advantages of nanoparticles, particularly, the high specific surface and the high ratio of surface atoms to innersphere atoms. Among the nanostructured materials investigated, nanometer-sized TiO2 particles are technologically important in many applications, which greatly increases their activity as a catalyst and sensitivity as a sensor [4, 5]. However, a serious problem is its aggregation with varied ambient conditions. In this paper, we report the synthesis of PSMA/TiO2 nanocomposites via a multi-component solution. The PSMA can provide functional groups, which anchor TiO2 particles and prevent them from aggregating. The PSMA gives a 1 : 1 alternating structure consisting of styrene and maleic anhydride, as shown in Fig. 1 [6]. PSMA was dissolved in THF (tetrahydrofuran) with stirring at 40 ◦C for 12 h, then acacH (acetylacetone) and deionized water (mol ratio 1 : 25) were dropped into the polymer solution. The acacH was used to reduce the hydrolyzing rate of Ti(OBu-n)4 (tetrabutyl titanate). The pH value of the mixture was adjusted to about 1.7 with concentrated hydrochloric acid (37%). After stirring for 20 min, the precursor Ti(OBu-n)4 dissolved in THF was dropped into the mixture. After that, the reactant mixture was heated to 60 ◦C, and stirred at this temperature for 4 h. Finally, the homogeneous mixture was sealed in a baking oven and kept at room temperature for 4 days. Several punctures were made in the sealing adhesive tape with a pin to volatilize THF at 40 ◦C in flowing air, and thus orange-red and optically transparent samples of PSMA/TiO2 composites were obtained. The samples were dried under vacuum at 80 ◦C for 2 days. FT-IR spectra of the samples indicate the existence of absorbed water from air, which gave rise to an absorption band [7] at 1620 cm−1, and especially, the broad band around 3500 cm−1. The IR spectrum of PSMA (Fig. 2a) shows that the adsorption bands at 1858 and 1778 cm−1 which are characteristic bands of the copolymer of styrene maleic anhydride [8], which are attributed to asymmetrical and symmetrical νC=O (C=O stretching vibration) of the maleic anhydride moiety [9], respectively. The peaks at 1600, 1500 and 1450 cm−1 are the νC=C of the phenyl group on the backbone chain [9, 10]. The band at 1214 cm−1 is attributed to the νC–O–C of maleic anhydride units, for a five-numbered cyclo-anhydride shows a νC–O–C band at 1310∼1210 cm−1 wavenumber [7]. The band at 700 cm−1 is the δC=C (C=C bending vibration) of the phenyl group [10], which was used as an internal reference to offset differences in the thickness of IR samples. The spectrum of pure TiO2 (Fig. 2b) shows a strong and broad adsorption peak between 650 and 400 cm−1, which is accounted for by vibrations of Ti–O–Ti groups [11], and regarded as the characteristic peak for TiO2 [12]. The IR information of both