The Succession of Heat and Mass Driven Natural Convection Regimes Along a Vertical Impermeable Wall

This paper presents the analysis of the natural convection process that takes place near a vertical plane wall embedded in a constant temperature and linearly mass stratified fluid (the Prandtl number and the Smith number are smaller than 1.0, while the Lewis number is greater than 1.0). The wall has a constant temperature, while the flux of a certain constituent is constant at this boundary. The scale analysis and the finite differences method are used as techniques of work. The scale analysis proves the existence, at equilibrium, of heat and/or mass driven convection regimes along the wall. The finite differences method is used solve the governing equations and to verify the scale analysis results using two particular parameters sets.

Optimización del tratamiento térmico para la inducción al desove de Argopecten purpuratus (Mollusca: Bivalvia)

Based on methodologies currently used in commercial hatcheries, four thermic treatments were compared to induce the gametes expulsion of Argopecten purpuratus. The treatments evaluated included: 1) gradual increase in temperature, 2) gradual decrease, 3) 5 °C thermal-shock, 4) 10 °C thermal-shock and 5) control at constant temperature 16 °C. After induction, the number of fertilized oocytes in each treatment was estimated. The results show that a gradual increase in temperature between 16 and 26 °C causes a significantly higher proportion of fertilized oocytes compared to other treatments.

Curing monitoring of bonded composite patch at constant temperature with electromechanical impedance and system parameters evaluation approach

As one of cost-effective maintenance methods, bonded composite patch repair has been receiving more and more attention in the engineering community since past decades. However, realizing real-time monitoring for curing process of bonded repair patch is difficult for most current techniques. In our work, a method based on electromechanical impedance and system parameters evaluation for structural health monitoring issues was developed, which could implement the online monitoring throughout whole curing process. Compared with the dynamic thermomechanical analysis results, the experiment data matches well. It demonstrates that the proposed approach can effectively monitor the curing process of composite repair patch at a constant temperature of 120 °C. Hence, the presented approach in this paper is expected to be a novel, robust, and real-time monitoring method for structural maintenance with the composite patch.

CHEMICAL AND STRUCTURAL CHANGES IN POPLAR WOOD UPON STEAM TREATMENT AT CONSTANT TEMPERATURE AND PRESSURE CONDITIONS FOR DIFFERENT TIME INTERVALS

Technology advancement has helped in the development of high-throughput equipment for the analysis of raw material in paper industries. In this research, we have used some advanced techniques to analyze the pore size, structural and chemical changes, and cellulose crystallinity of poplar wood pretreated with steam at constant temperature and pressure conditions for different treatment time. Samples were analyzed by the nitrogen adsorption test, Fourier-transform infrared spectroscopy – attenuated total reflectance (FTIR–ATR), X-ray diffraction (XRD), and field scanning electron microscopy (FE-SEM). Slit-shaped pores were formed, with a diameter of 2.12 nm, after 30 minutes of treatment. FTIR results revealed the degradation of the lignin skeleton through the formation of guaiacyl and syringyl units and deformation in the cellulose and hemicelluloses structure. The crystallinity index (CI) increased upon steam treatment for up to 15 min, but after that, a drop in the CI was observed. The crystallite thickness (d200) increased after 15 min of treatment, due to the rearrangement of cellulose chains. However, a further increase in steam treatment duration to 30 min resulted in a decline of d200, followed by an increase in the cellulose II crystalline region and d020. The steam treatment duration of 15-30 min was found to be a critical time interval, which led to increases in the number of mesopores, CI, d200, and the cellulose II region in the poplar wood.

Modified superstructure fiber Bragg grating for a filter application

Performance of a modified superstructure fiber Bragg grating is carried out by; simulation using a Matlab and then by optisystem7. Results for these two simulations are compared with an experimental investigation for three special FBGs in addition to a standard one. These four FBGs have one, two, three, and four regions. For each region, Bragg wavelength is increased around 6nm, with constant spacing between every two regions. Laser reflectance (R) and transmittance (T) spectra and their corresponding number of peaks and their bandwidths are observed and analyzed in a constant temperature and strain. Results for this investigation indicate enhancement for the modified FBG to be an effective filter that can be employed for communication as well as sense. Filtering the transmitted signals could be satisfied in a simple and more efficiency than the traditional device.

Hydrogenation of coconut oil into Biofuel (bio-jet fuel and high-value low molecule hydrocarbons)

The performance of Ni/HZSM-5, HZSM-5, and without a catalyst have been investigated for the hydrogen pressure range of 10-40bar hydrocracking of coconut oil in a packed-bed tubular reactor between 300-450°C. This study concentrates on the effect of the operating parameters (reaction pressure, type of catalyst and reaction temperature) on the yield of transportation fuel carbon range (C5-C22) using the One-Variable-At-A-Time approach. The objectives of this study are to evaluate the effect of process conditions which includes: temperature, pressure, and presence of a catalyst, and to compare the activity of Ni/HZSM-5, HZSM-5 and without catalysts. All tested catalysts were effective in attaining biofuel range in the liquid product. The highest yield and performance of gasoline liquid composition 83.03% was obtained from the reaction pressure at constant temperature of 450 ͦC in 40bar where HZSM-5 catalysts was used, the yield of gasoline liquid composition 82.25% was also produced at constant pressure of 40 bar in 300 ͦC where promoted catalyst(Ni/HZSM-5) was used. Hydrocracking coconut oil under Ni/HZSM-5 catalysts produced the highest yield of jet fuel liquid compositions 78.73% at constant temperature 300°C, and pressure of 10 bar, this was due to less coke that was formed within a reactor and less temperature of 300°C. The highest yield of jet fuel liquid composition 75.67% was also produced at constant pressure of 10 bar at muximum temperature of 450 ͦ C, this was also due to less coke that was formed within a reactor where HZSM-5 was used because of less pressure applied. For the highest yield of diesel liquid composition 24.04%, constant temperature at 400 ͦC of 20 bar where Ni/HZSM-5 was used in figure:5-9 and the highest yield of diesel liquid composition 25.15% was also produced at constant pressure of 20 bar in 450 ͦC where HZSM-5 was used. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) coupled with Energy- dispersive X-ray spectroscopy (EDS) analyses were employed for catalyst characterization. XRD patterns confirm the success of metal doping on ZSM-5. Major peaks at 9.1° and 22.9° corresponding to ZSM-5 crystals were observed in ZSM-5. Impregnation with metals reduced the crystallinity of ZSM-5 supported catalysts.

Solving hybrid-vehicle routing problem using modified simulated annealing

<span lang="EN-US">In this paper, we consider the hybrid vehicle routing problem (HVRP) at which the vehicle consumes two types of power: fuel and electricity. The aim of this problem is to minimize the total cost of travelling between customers, provided that each customer is visited only once. The vehicle departs from the depot and returns after completing the whole route. This optimization problem is solved using a modified simulated annealing (SA) heuristic procedure with constant temperature. This approach is implemented on a numerical example and the results are compared with the SA algorithm with decreasing temperature. The obtained results show that using the SA with constant temperature overrides the SA with decreasing temperature. The results indicate that SA with decreasing temperature needs twice the number of iterations needed by the SA with constant temperature to reach a near optimum solution.</span>

Feedback PID Controller-Based Closed-Loop Fast Charging of Lithium-Ion Batteries Using Constant-Temperature–Constant-Voltage Method

Lithium-ion batteries are the most used technology in portable electronic devices. High energy density and high power per mass battery unit make it preferable over other batteries. The existing constant-temperature and constant-voltage charging technique (CT–CV), with a closed loop, lacks a detailed design of control circuits, which can increase charging speed. This article addresses this research gap in a novel way by implementing a simpler feedback proportional integral and differential (PID) control to a closed-loop CT–CV charging circuit. Voltage-mode control (VMC) and average current-mode control (ACM) methods were implemented to maintain the battery voltage, current, and temperature at safe limits. As per simulation results, 23% faster charging is achieved by implementing VMC and almost 50% faster charging is attained by employing the ACM technique in the PID controller. Our proposed control strategy is validated experimentally, which yields up to 25% faster charging of a battery than the reference battery.

Analysing temperature protocol deviations in pome fruit export cold chains: A Western Cape case

Background: A major concern plaguing South African pome fruit exporters is the volume of fruit going to waste during the export process. The senescence of fruits and the deterioration in its quality are accelerated by an increase in temperature. Thus, the first step in ultimately extending the shelf life of exported pome fruit and decreasing the risk of rejections is to ensure constant temperature control.Objectives: The study investigated the severity of temperature protocol deviations within the apple and pear export cold chains from the Western Cape, South Africa to the Netherlands. The study was undertaken in 2018 for Company X, an international fruit exporting firm, to improve the efficiency of its cold chains.Method: The research conducted temperature trials starting as close to the farm as possible and concluding as close to the end consumer as possible. Pulp and ambient temperature probes were inserted into and around the fruit to monitor export temperature profiles.Results: Firstly, the trial results show that non-compliance with temperature protocols occurred more often along the pome fruit export cold chain than initially anticipated. Secondly, the position within the pallet where the temperature breaks occurred highlighted an issue of heat retention resulting from unintentional oversights early in the cold chain. The study also identified areas of possible improvements where management could mitigate senescence factors.Conclusion: The study concluded that the efficient and effective functioning of a cold chain depends on cumulative efforts by all the supply chain partners rather than on the efforts of a single partner.