Ambient Temperature Conditions Research Articles

Impact of metakaolin on hydration properties of magnesium phosphate cement

The degradation of mechanical properties in magnesium phosphate cement (MPC) is commonly observed under conditions of rapid heat release and high ambient temperature. To mitigate this phenomenon, the incorporation of metakaolin has been investigated as a means to reduce the hydration heat of MPC and enhance its mechanical properties at elevated temperatures. Experimental findings reveal a pronounced influence of metakaolin on the heat flow behavior of MPC. Specifically, the addition of a small fraction of metakaolin (not exceeding 20wt%) leads to an accelerated heat release rate during the initial 0.13hours, followed by a substantial reduction in the heat release rate with further increments of metakaolin. Furthermore, the inclusion of metakaolin significantly improves the mechanical properties of MPC. For instance, a composition comprising 30% metakaolin yields a notable 79.2% increase in strength after 7 days. It is worth noting that temperatures below 400℃ are found to have an adverse impact on the mechanical properties of MPC, whereas a temperature range encompassing 600℃>T>400℃ enhances these properties due to vitrification at high temperatures. Importantly, MPC incorporating metakaolin exhibits superior mechanical performance compared to its metakaolin-free counterpart across all tested temperatures, which can be attributed to the attainment of a denser microstructure facilitated by metakaolin incorporation.

The Influence of Different Working Fluid Temperatures on the Hydraulic Performance of Magnetic Vortex Pumps

Magnetic vortex pumps are characterized by their high performance and zero leakage, and in recent years, they have been applied for the transportation of antifreeze coolant in varying-temperature environments. This paper combines Computational Fluid Dynamics (CFD) with experimental verification to study the external and internal flow characteristics of magnetic vortex pumps when transporting working fluid at different temperatures, considering radial clearance flow. The results indicate that as the temperature of the medium increases, both the pump head and efficiency improve. Specifically, under the design flow rate condition, the pump head increases by 16.7% when transporting a medium at 90 °C compared to ambient-temperature conditions. Conversely, the pump head is only 16.8% of that observed under ambient-temperature conditions when transporting a medium at −30 °C. Analysis of the internal flow field reveals that the changes in pump hydraulic performance at different working fluid temperatures are primarily due to variations in the vorticity of the internal flow field.

Combined effects of ambient temperature and food availability on induced innate immune response of a fruit-eating bat (Carollia perspicillata).

Resilience of mammals to anthropogenic climate and land-use changes is associated with the maintenance of adequate responses of several fitness-related traits such as those related to immune functions. Isolated and combined effects of decreased food availability and increased ambient temperature can lead to immunosuppression and greater susceptibility to disease. Our study tested the general hypothesis that decreased food availability, increased ambient temperature and the combined effect of both factors would affect selected physiological and behavioral components associated with the innate immune system of fruit-eating bats (Carollia perspicillata). Physiological (fever, leukocytosis and neutrophil/lymphocyte ratio) and behavioral (food intake) components of the acute phase response, as well as bacterial killing ability of the plasma were assessed after immune challenge with lipopolysaccharide (LPS: 10 mg/kg) in experimental groups kept at different short-term conditions of food availability (ad libitum diet or 50% food-deprived) and ambient temperature (27 and 33°C). Our results indicate that magnitude of increase in body temperature was not affected by food availability, ambient temperature or the interaction of both factors, but the time to reach the highest increase took longer in LPS-injected bats that were kept under food restriction. The magnitude of increased neutrophil/lymphocyte ratio was affected by the interaction between food availability and ambient temperature, but food intake, total white blood cell count and bacterial killing ability were not affected by any factor or interaction. Overall, our results suggest that bacterial killing ability and most components of acute phase response examined are not affected by short-term changes in food availability and ambient temperature within the range evaluated in this study, and that the increase of the neutrophil/lymphocyte ratio when bats are exposed to low food availability and high ambient temperature might represent an enhancement of cellular response to deal with infection.

Integrating Superconductivity in Cu Replace Lead Apatite by Nuclear Magnetic Moment Theory of RBL

Recently, scientists proclaimed superconductivity under ambient conditions of room temperature and 1 atmosphere pressure in Cu partial substituted lead apatite: Pb(10-x)Cux(PO4)6. This paper highlights the application of RBL’s stable isotope of positive and negative nuclear magnetic moments (NMMs) theory for explaining the heavy isotopic enrichment of this materials as {207Pb{10-x}63Cux(‘31PιO4)6}, where ι = 17 or 18 and the resulting superconductivity and novel room temperature atmospheric pressure superconductivity of this heavy isotopic enriched substance. On the basis of such analysis by RBL theory, the synthesis of high temperature, regular pressure superconductivity can be explained and this recent experimental observation of ambient pressure and temperature superconductivity in 207Pb{10-x}63Cux(‘31PιO4)6, where ι = 17 or 18, proves RBL’s NMMs theory of high temperature superconductivity. After 1 month on July 22, 2023 of the archiving of such data for superconductivity Pb(10-x)Cux(PO4)6 by Lee and coworkers, a huge experimental effort by hundreds of researchers around the world has attempted to replicate this room temperature, ambient pressure superconductivity in Pb(10-x)Cux(PO4)6 without success. The resulting inability to replicate the ambient superconductivity and note of some fractional component in the mixture causing the ambient superconductivity is explained by RBL’s theory as the fractional component may be clumped isotopes as in {207Pb{10-x}63Cux(‘31PιO4)6}, where ι = 17 or 18, and RBL here notes the vapor deposition process alleged by Lee and coworkers for producing the superconductivity was previously predicted by RBL to cause isotopic fractionation during solid to liquid and liquid to gas and gas to solid physical changes.

Life cycle testing and reliability analysis of prismatic lithium-iron-phosphate cells

ABSTRACT A cell’s ability to store energy, and produce power is limited by its capacity fading with age. This paper presents the findings on the performance characteristics of prismatic Lithium-iron phosphate (LiFePO4) cells under different ambient temperature conditions, discharge rates, and depth of discharge. The accelerated life cycle testing results depicted a linear degradation pattern of up to 300 cycles. Linear extrapolation reveals that at 25°C temperature, an increase in the discharge rate from 0.5 C to 0.8 C reduces the cycle life significantly by 52.9%. On the other hand, at a constant discharge rate, an increase in temperature reduced predicted cycle life in the range of 23.2–41.36%. Lithium-ion cells’ reliability modeling and analysis was carried out using an exponential distribution showing the increasing failure rate with age, with the temperature significantly reducing the expected life of the cells.

Effect of Block Copolymer Self-Assembly on Phase Separation in Photopolymerizable Epoxy Blends.

Directing self-assembly of photopolymerizable systems is advantageous for controlling polymer nanostructure and material properties, but developing techniques for inducing ordered structure remains challenging. In this work, well-defined diblock or random copolymers were incorporated into cationic photopolymerizable epoxy systems to investigate the impact of copolymer architecture on self-assembly and phase separated nanostructures. Copolymers consisting of poly(hydroxyethyl acrylate)-x-(butyl acrylate) were prepared using photoiniferter polymerization to control functional group placement and molecular weight/polydispersity. Prepolymer configuration and concentration induced distinctly different effects on the resin flow and photopolymerization kinetics. The diblock copolymer self-assembled into nanostructured phases within the resin matrix, whereas the random copolymer formed an isotropic mixture. Rapid photopolymerization and ambient temperature conditions during cure facilitated retention of the self-assembled phases, leading to considerably different composite morphology and thermomechanical behavior. Increased loading of the diblock copolymer induced long-range ordered cocontinuous structures. Even with nearly identical prepolymer composition, controlled nanophase separation resulted in significantly enhanced tensile properties relative to those of the isotropic system. This work demonstrates that controlling phase separation with a block copolymer architecture allows access to nanostructured photopolymers with unique and enhanced properties.

Heating performance of a vapor compression heat pump cascaded with a thermoelectric heat pump

Air source heat pumps (ASHPs) are widely utilized for heating and cooling in residential buildings; however, their effectiveness in heating mode is compromised during extreme weather conditions. Extensive research endeavors have been undertaken to develop, test, and assess a cost-effective vapor compression ASHP suitable for cold climate regions. This study takes an innovative approach by developing component and system prototypes for a cold climate heat pump. This design combines a thermoelectric heat pump (TEHP) with a traditional residential split ASHP to augment heating capacity in low ambient temperature conditions. The component and system prototypes underwent experimental testing in the psychrometric chambers. The experimental findings revealed a 13.6 % to 13.7 % increase in total heat pump heating capacity, accompanied by a 3.1 % to 5.0 % decrease in the coefficient of performance (COP) at ambient temperatures of −15 °C and −19 °C, when compared to the original ASHP. The COP of the TEHP is relatively constant, ranging from 1.63 to 1.76. This prototype offers a solution to address the challenges associated with reduced heat pump capacity at low ambient temperatures. The experimental results indicated that the lower the ambient temperature, thermoelectric heat pump auxiliary heating can increase the heating efficiency 60 % in comparison to electric resistance.

Zebra finch song parameters are affected by the breeding status of the male, but not temperature variability

Bird song is a crucial feature for mate choice and reproduction. Song can potentially communicate information related to the quality of the mate, through song complexity, structure or finer changes in syllable characteristics. It has been shown in zebra finches that those characteristics can be affected by various factors including motivation, hormone levels or extreme temperature. However, although the literature on zebra finch song is substantial, some factors have been neglected. In this paper, we recorded male zebra finches in two breeding contexts (before and after pairing) and in two ambient temperature conditions (stable and variable) to see how those factors could influence song production. We found strong differences between the two breeding contexts: compared to their song before pairing, males that were paired had lower song rate, syllable consistency, frequency and entropy, while surprisingly the amplitude of their syllables increased. Temperature variability had an impact on the extent of these differences, but did not directly affect the song parameters that we measured. Our results describe for the first time how breeding status and temperature variability can affect zebra finch song, and give some new insights into the subtleties of the acoustic communication of this model species.

Influences of a Supplemental Blend of Essential Oils Plus 25-Hydroxy-Vit-D3 and Zilpaterol Hydrochloride (β2 Agonist) on Growth Performance and Carcass Measures of Feedlot Lambs Finished under Conditions of High Ambient Temperature.

Forty-eight Pelibuey × Katahdin male intact lambs (25.12 ± 3.79 kg LW) were used in a 70-d growing-finishing trial. Dietary treatments consisted of total mixed corn-based diet supplemented with: (1) no feed additives (Control); (2) 150 mg of essential oils blend plus 0.10 mg of 25-hydroxy-Vit-D3/kg diet offered throughout the 70-d experimental period (EOD3); (3) Control diet fed during the first 35 days and zilpaterol hydrochloride (ZH) supplementation at 6 mg/kg diet offered during the final 35 days of the experiment (32 days with ZH with a withdrawal 3-d before harvest), and (4) basal diet supplemented with EOD3 during first 35 days finishing, and EOD3 in combination with ZH (EOD3 + ZH) during the subsequent 32-days with ZH withdrawal 3 days before harvest. The temperature-humidity index during the experiment averaged 80.4 ± 3.2. There were no treatment interactions (p > 0.20) on growth performance and carcass measures. Supplemental EOD3 did not affect (p = 0.43) dry matter intake (DMI), but increased (p < 0.01) carcass adjusted average daily gain (ADG, 9.2%), gain efficiency (GF, 6.7%), and observed vs. expected dietary net energy for maintenance (NEm, 4.8%) and for gain (NEg, 6.4%). Supplemental ZH did not affect dry matter intake (DMI, p = 0.50) but increased (p < 0.01) carcass adjusted ADG (14.5%), GF (13%) and observed vs. expected dietary NEm (9%) and NEg (11.7%). Compared to control lambs, the combination of both additives increased ADG (24.9%), GF (21.2%), and observed vs. expected dietary NEm and NEg (14.2% and 18.9%, respectively). There were no treatment interactions on carcass characteristics, visceral organ mass, or on gene expression of IGF1, IGF2 and mTOR in longissimus muscle (LM). Supplemental EOD3 increased hot carcass weight (HCW; 4.0%, p < 0.01) but did not affect other carcass measures. Supplemental EOD3 decreased (3%, p = 0.03) intestine mass weight (g intestine/kg empty body weight). Supplemental ZH increased HCW (6%, p < 0.01), dressing percentage (1.7%, p = 0.04), and LM area (9.7%, p < 0.01), and decreased kidney-pelvic-fat percentage (16.2%, p < 0.01), fat thickness (14.7%, p = 0.03), and visceral fat. Compared to controls, the combination of EOD3 with ZH increased HCW (10.2%). It is concluded that growth performance responses to supplemental EOD3 and ZH are additive. Both supplements can be fed in combination without detrimental effects on expected benefits when fed separately. In addition, ZH supplementation improves carcass traits.

Effective techniques to break seed dormancy in Rhodomyrtus tomentosa (Aiton) Hassk. for seed germination enhancement

Rhodomyrtus tomentosa is a valuable plant for medical and pharmaceutical uses. The plant reproduces through seeds; however, the seeds become dormant, resulting in low germination rates. The industrial demand for this plant is expanding, making sustainable propagation a major challenge. The present study aims to evaluate different techniques for breaking the dormancy of R. tomentosa seeds. A randomized design was used to evaluate different techniques for breaking the dormancy of R. tomentosa seeds, including de-operculum, chemical scarifications, and exogenous gibberellic acid (GA3), in both laboratory conditions at ambient temperature (25 ± 2 °C) and field conditions. The characteristics of R. tomentosa fruit and seeds were assessed. The average mass, width, and length of fruits were 1.90 g, 13.78 g, and 15.27 g, respectively. The average seed/ripe fruit contained 57 seeds, and the mass of 1000 seeds was 2.64 g. Seed viability (100 %) was achieved in the treatment with 0.075 % tetrazolium at 45 °C for 3 h, but a germinated seed was only 13.00 %. The study of breaking seed dormancy in laboratory conditions revealed that de-operculum significantly enhanced seed germination up to 83.00 % within 15 days, compared with control treatment of 13.00 % within 34 days (p ≤ 0.01). In contrast, 10 % KNO3 for 24 h under field conditions resulted in the highest seed germination rate of 91.00 % within 34 days, while de-operculum treatment showed 63.00 % of seed germination within 15 days. In addition, the seed water imbibition rate between control and de-operculum seeds was evaluated. The results demonstrated that the control seeds absorbed water more slowly than the de-operculum seeds, indicating that de-operculum promoted faster germination. The findings concluded that breaking seed dormancy is important for R. tomentosa seed germination. De-operculum and KNO3 were discovered to be effective ways of breaking seed dormancy in R. tomentosa.

Thermodynamic analysis of rotary pressure exchanger and ejectors for CO2 refrigeration system

Natural refrigerant CO2 has become a viable choice for refrigeration units for land-based and offshore applications due to its environment-friendly nature and compactness. The CO2 transcritical cycle allows operating in colder climates and in elevated ambient temperature conditions and with significant heat recovery. However, the energy efficiency of the system suffers at higher heat rejection conditions mainly due to expansion losses. This work theoretically investigates and proposes the implementation of a new expansion work recovery device, a pressure exchanger (CO2-PX), for the transcritical CO2 cycle. The numerical models are developed in the Engineering Equation solver (EES) to compare the performance of CO2-PX configuration with standard booster-, parallel-, and ejector- configurations for various conditions. The analysis is carried out for the evaporation temperature of 0 ℃ and the gas cooler outlet temperature of 33 ℃ to 37 ℃. The results indicate that the coefficient of performance (COP) is improved by 17.7–23.5%, 16.3–20.3%, and 2.4–5.5% to the standard booster, parallel and ejector configurations, respectively, at the investigated conditions.

Laboratory Tests of Electrical Parameters of the Start-Up Process of Single-Cylinder Diesel Engines

Despite continuous work on new power systems for vehicles, machines, and devices, the combustion engine is still the dominant system. The operation of the combustion engine is initiated during the starting process using starting devices. The most common starting system used is the electric starter. The starting process of an internal combustion engine depends on the following factors: the technical condition of the starting system, technical condition of the engine, battery charge level, lubricating properties, engine standstill time, engine and ambient temperature, type of fuel, etc. This article presents the results of laboratory tests of the electrical parameters of the starting process of a single-cylinder compression–ignition engine with variable fuel injection parameters and ambient temperature conditions. It was confirmed that for the increased fuel dose FD2, higher values of the measured electrical parameters (Imax, Pmax, and Pmed) were obtained compared to the series of tests with the nominal fuel dose. Knowledge of the values of the electrical parameters of the starting process is important not only for the user (vehicle driver, agricultural machinery operator, etc.), but above all for designers of modern starting systems for combustion engines and service personnel. The obtained results of testing the electrical parameters of the combustion engine during start-up may be helpful in designing new drive systems supported by a compression–ignition combustion engine.

Unraveling Ammonia and Trimethylamine Uptake on Conductive Doped Polyaniline.

Polyaniline (PAni)-based sensors are a promising solution for ammonia (NH3) detection at the ppb level. However, the nature of the NH3-PAni interaction and underlying drivers remain unclear. This paper proposes to characterize the interaction between doped PAni (dPAni) sensing material and NH3 by using a Knudsen cell. First, to characterize the dPAni interface, the probe-gas method, i.e., titration of surface sites with a gas of specific properties, is deployed. The dPAni interface is found to be homogeneous with more than 96% of surface sites of acid nature or with hydroxyl functional groups. This result highlights that basic gases such as amines might act as interfering gases for NH3 detection by polyaniline-based sensors. Second, the adsorption isotherms of NH3 and trimethylamine (TMA) on dPAni are reported at ambient temperature conditions, 293 K. The uptake of NH3 and TMA on dPAni follows a Langmuir-type behavior. This approach allows for the first time to quantify the uptake of NH3 and TMA on gas-sensor materials and determine typical Langmuir adsorption parameters, i.e., the partitioning coefficient, KLang, and the maximum surface coverage, Nmax. The corresponding values obtained for NH3 and TMA are Klang (NH3) = 19.7 × 10-15 cm3 molecules-1 Nmax (NH3) = 11.6 × 1014 molecules cm-2, KLang (TMA) = 7.0 × 10-15 cm3 molecules-1 Nmax (TMA) = 5.0 × 1014 molecules cm-2. KLang and Nmax values of NH3 are higher than those of TMA, suggesting that NH3 is more efficiently taken up than TMA on dPAni. The results of this work suggest that strong hydrogen bonding drives the performance of a polyaniline-based gas sensor for NH3 and amines. In conclusion, the Knudsen cell approach allows reconsidering the fundamentals of NH3 interactions with dPAni and provides new insights on drivers to enhance sensing properties.

Mechanochemical Birch Reduction with Low Reactive Alkaline Earth Metals.

Birch reduction and similar dissolved metal-type transformations hold significant importance in the organic synthesis toolbox. Historically, the field has been dominated by alkali metal reductants. In this study, we report that largely neglected, low-reactive alkaline earth metals can become powerful and affordable reductants when used in a ball mill under essentially solvent-free conditions, in the presence of ethylenediamine and THF as liquid additives. Calcium can reduce both electron-deficient and electron-rich arenes, with yields of products similar to those obtained with lithium metal. Magnesium reveals enhanced reducing power, enabling the reduction of benzoic acids while keeping electron-rich aromatic moieties intact and allows for chemoselective transformations. The developed mechanochemical approach uses readily available and safer-to-handle metals, operates under air and ambient temperature conditions, and can be used for gram-scale preparations. Finally, we demonstrate that the developed conditions can be used for other dissolved metal-type reductive transformations, including reductive amination, deoxygenation, dehalogenation, alkene and alkyne reductions.

Mechanochemical Birch Reduction with Low Reactive Alkaline Earth Metals

AbstractBirch reduction and similar dissolved metal‐type transformations hold significant importance in the organic synthesis toolbox. Historically, the field has been dominated by alkali metal reductants. In this study, we report that largely neglected, low‐reactive alkaline earth metals can become powerful and affordable reductants when used in a ball mill under essentially solvent‐free conditions, in the presence of ethylenediamine and THF as liquid additives. Calcium can reduce both electron‐deficient and electron‐rich arenes, with yields of products similar to those obtained with lithium metal. Magnesium reveals enhanced reducing power, enabling the reduction of benzoic acids while keeping electron‐rich aromatic moieties intact and allows for chemoselective transformations. The developed mechanochemical approach uses readily available and safer‐to‐handle metals, operates under air and ambient temperature conditions, and can be used for gram‐scale preparations. Finally, we demonstrate that the developed conditions can be used for other dissolved metal‐type reductive transformations, including reductive amination, deoxygenation, dehalogenation, alkene and alkyne reductions.

Polysulfide-ene polymerization of bisacrylamides and bismaleimides toward sulphur-rich polymers

Given the ever-increasing importance of developing more sustainable solutions for the fabrication and engineering of polymeric materials, alternative building blocks to the petroleum-derived chemicals are gaining growing interest. In addition to its natural abundance, elemental sulfur is produced industrially in vast quantities which is primarily obtained as a side product from oil refineries and gas purification plants. Thus, elemental sulfur has been prospected as a sustainable resource for the fabrication of structurally diverse polymers. In this study an efficient methodology to obtain sulfur-rich polymers from elemental sulfur-derived polysulfide salts is reported. Polysulfide-ene step growth polymerization of bisacrylamide and bismaleimide-based monomers with bifunctional disodium pentasulfide (Na2S5) generated structurally diverse polyamide and polyimide copolymers incorporating polysulfide chains on the polymer backbones. Copolymers up to 31.8 kDa molecular weight (Mn) and 94% monomerconversions were efficiently obtained under ambient temperature conditions and without the need of any metal or organo-catalyst. By choosing various bifunctional ene monomers, structurally diverse and tailorable linear copolymers were obtained. The methodology was also extended to the fabrication of sulfur-rich crosslinked polymers by employing a multifunctional thiolate-based crosslinker. As a potential application, fabricated crosslinked polymers were employed as adsorbents to remove toxic mercury ions from water. The reported synthetic strategy demonstrated the efficiency of polysulfide-ene reaction to synthesize sulfur-rich polyamide and polyimide polymers and could broaden the available polymerization reaction tools that employelemental sulfur-derived polysulfide salts in functional polymer synthesis.

Development of sustainable engineered cementitious composite with enhanced compressive performance at elevated temperatures using high volume GGBFS

This study presents the development of an environmentally sustainable hybrid polyethylene (PE)-steel fibre reinforced engineered cementitious composites (ECC) to achieve enhanced compressive performance at elevated temperature. Utilizing a unique blend of industry by-products—ground granulated blast furnace slag (GGBFS), dolomite powder, and fly ash, with supplementary cementitious materials exceeding 50% replacement level, the developed ECC achieves remarkable improvement in compressive strength, both at ambient and elevated temperature conditions. A total of 340-cylinder specimens were tested to analyse the compressive properties after exposure to 20–800 °C, and the effect of different binders, fibre ratio on the residual compressive behaviour was investigated. Additionally, effects of the critical fire test parameters such as pre-drying and cooling treatment were also studied. The research findings indicate that incorporating high-volume GGBFS blends significantly improved the compressive performance of the ECC irrespective of the type of test parameters. Notably, a specific blend comprising of GGBFS, fly ash (GGBFS:fly ash = 1:0.2) and dolomite (15% by binder weight) demonstrated 138 MPa strength at room temperature and at least 75% and 45% strength retention at 600 °C and 800 °C, respectively. This was significantly higher than the values reported in literatures (∼48% at 600 °C and ∼12% at 800 °C) for similar type of ECC. The study also highlights the impact of sudden cooling in water and confirms the occurrence of both thermal shock and rehydration through microstructural analysis. Environmental impact analysis was also conducted to demonstrate the low carbon emission of the developed ECC.

Clean-up of divalent cobalt ions by massive sequestration in a low-cost calcium silicate hydrate material

Cobalt is a critical resource in industrial economies for the manufacture of electric-vehicle batteries, alloys, magnets, and catalysts, but has acute supply-chain risks and poses a threat to the environment. Large-scale sequestration of cobalt in low-cost materials under mild conditions opens a path to cobalt recycling, recovery and environmental clean-up. We describe such sequestration of cobalt by a widely available commercial calcium silicate material containing the mineral xonotlite. Xonotlite rapidly and spontaneously takes up 40 percent of its weight of cobalt under ambient conditions of temperature and pressure and reduces dissolved cobalt concentrations to low parts per million. A new Sharp Front experimental design is used to obtain kinetic and chemical information. Sequestration occurs by a coupled dissolution-precipitation replacement mechanism. The cobalt silicate reaction product is largely amorphous but has phyllosilicate features.

Experimental Transient Process Analysis of Micro-Turbojet Aviation Engines: Comparing the Effects of Diesel and Kerosene Fuels at Different Ambient Temperatures

In this paper, we investigate the impact of diesel and kerosene on the transient processes occurring in a micro-turbojet aviation engine. The experiments were conducted under two distinct ambient temperature conditions, 0 and 20 °C. Specifically, we analyzed the starting phase of the micro-engine while operating with kerosene and diesel at both ambient temperature settings. Comparative graphs were generated, and the starting time was meticulously examined. Subsequently, we constructed performance maps for the engine using both fuels and across the two ambient temperature scenarios. We then executed a transient process, comprising sudden acceleration and deceleration, under the aforementioned ambient temperature conditions and with both fuels. The fluctuations in temperature within the combustion chamber, thrust force, and fuel consumption are presented for both rapid acceleration and deceleration events. Furthermore, we conducted comparisons between the thrust force, fuel flow rate, combustion chamber temperature, and specific fuel consumption for the two fuels tested and under the two ambient temperature conditions, both during idle and at higher engine regimes. In the idle regime at 0 °C, the kerosene flow is about 0.78% higher than diesel, with the kerosene thrust approximately 1.92% greater. At 20 °C, the kerosene consumption rises by roughly 5.56% compared to diesel, while the thrust increases by about 1.38%. It was observed that at the maximum operating regime, at 0 °C, the kerosene flow exceeds diesel by around 6%, with the kerosene thrust slightly higher, by about 0.63%. At 20 °C, the kerosene consumption rises by roughly 13.19% compared to diesel, while the thrust increases by about 5.91%. In higher regimes, the kerosene consumption surpasses diesel, but the thrust increase is not significant. Thus, diesel’s use as a fuel for the microturbo engine is justified due to its lower consumption at both 0 °C and 20 °C.

African Star Apple Juice Stored at Tropical Ambient and Refrigeration Temperatures: Effect on Physicochemical Characteristics, Antioxidant Properties and Microbiological

The present study was aimed at evaluating the physicochemical and antioxidant properties as well as microbiological quality of extracted juice from African star apple (Chrysophyllum albidum) stored under tropical ambient and refrigeration conditions. Juice was extracted from mashed star apple fruit cotyledons (after deseeding) and pasteurized in a water bath at 71.2 oC for 30 minutes before storage for four (4) weeks under tropical ambient (28±2 oC) and refrigeration (6±2 oC) conditions. The results showed that there was no fibre in the juice, the moisture was 78.51% and 79.13% for fresh African star apple (ASA) juice and sample stored under ambient conditions, respectively. It also showed pH of ASA juice at week 0 to be 3.52 and week 4 for both samples stored at refrigeration and ambient temperatures to be 2.85 and 2.28, respectively. There was no fecal coliform count in all the studied juice samples throughout the storage period, but total viable bacteria counts were 2.7x104 cfu/ml, 1.84x105 cfu/ml and 6.6x104 cfu/ml for fresh juice and juice stored for 4 weeks at ambient temperature and refrigeration conditions, respectively. Overall, storage conditions had insignificant impact on the antioxidant properties and free radical scavenging capacity of the fruit juice; the slight changes observed were linked to usual molecular reactions. In conclusion, storage under refrigeration conditions elongated the shelf life of the juice.