Analysis of preheating temperature field characteristics in selective laser sintering

Selective laser sintering technology has broad application prospects in the manufacture of small batch parts with complex structure. In the sintering process, the preheating efficiency and temperature of powder layer determine the processing quality. A method of preheating powder by lamp radiation and tropical heat conduction is proposed in this paper. The thermal radiation model is established, and the angle coefficient is introduced to describe the proportion of radiation energy on the surface of powder layer. Based on the geometric characteristics of the powder cylinder, the heat conduction process is simplified to one-dimensional heat conduction along the radial direction, and the heat conduction model is established. The coupled temperature field under two actions is obtained by combining the heat radiation model with the heat conduction model. The uniformity coefficient [Formula: see text]/[Formula: see text] of the temperature field is defined to represent the uniformity of the preheating temperature field of the powder layer. By comparing the uniformity coefficient [Formula: see text], a more uniform temperature field can be obtained when the height coefficient is 1.8 under combined action. The validity of the model is verified by a comparative experiment with processed water atomized iron powder. Constructing uniform temperature field can effectively reduce the deformation of parts and improve the forming quality.

Wind Drift Evaporation Loss and Soil Moisture Distribution under Sprinkler Irrigated Blackgram (Vigna mungo L.)

An experiment was conducted during March–June 2018 with the sprinkler irrigation system covered in an area of 39×42 m2. Proper design and management of sprinkler irrigation systems improves the uniformity of moisture distribution and reduces wind drift and evaporation losses (WDEL) for effective crop growth. Uniformity coefficient, wind drift and evaporation loss of the sprinkler system at a different pressure head of 2 kg cm-2, 2.5 kg cm-2 and 3 kg cm-2 were studied. Wind speed was observed by using handheld anemometer. The wind speed ranged between 0.9 to 4.5 m s-1. The highest uniformity coefficient of 88.19% and wind drift and evaporation loss of 3.5% were obtained at the pressure head of 3 kg cm-2 and the wind speed of 0.9 m s-1. Soil samples were collected at different depths of 0–10 cm, 10–20 cm, 20–30 cm and at a radial distance from 0 m, 3 m, 6 m, 9 m, 12 m respectively to determine the soil moisture distribution pattern. The soil moisture content values were plotted by using the computer software, surfer 10 of the windows version and contour maps were drawn. The moisture content was found to be more at 0–10 cm depth, as compared to 10–20 cm and 20–30 cm depth. The percentage of moisture was found to be highest at a 6 m distance, which was due to overlapping of the sprinkler system.

Durability Evaluation of Concrete Bridges Based on the Theory of Matter Element Extension—Entropy Weight Method—Unascertained Measure

To accurately evaluate the durability of reinforced concrete girder bridges, a durability evaluation model was developed based on the matter element extension theory, entropy weight method, and unascertained measure theory. A total of seven indicators were selected for durability evaluation: the concrete presumed strength uniformity coefficient, reinforcement corrosion potential level, chloride ion content, average value of concrete relative carbonation depth, crack width, resistivity, and characteristic value of the reinforcement protective layer thickness. The weights of the durability evaluation indices were assigned using matter element extension combined with the entropy weight method, and the multi-indicator comprehensive evaluation vector was obtained by combining the single-indicator measurement matrix. The evaluation results were analyzed by applying the confidence criterion. The results showed that the evaluation results of this model matched with the actual conditions of the girder bridges, which indicates that this durability evaluation model has good applicability and is reasonable. Finally, a comparative study proved that the model could accurately evaluate the bridge durability.

Influence of the Lubrication Oil Temperature on the Disengaging Dynamic Characteristics of a Cu-Based Wet Multi-Disc Clutch

Clutch disengaging dynamic characteristics, including the disengaging duration and the variations of friction pair gaps and friction torque, are crucial to the shifting control of an automatic transmission. In the present paper, the influence of lubrication oil (ATF) temperature on disengaging dynamic characteristics is investigated through a comprehensive numerical model for the clutch disengaging process, which considers the hydrodynamic lubrication, the asperity contact, the heat transfer, the spline resistance, and the impact between the piston and clutch hub. Moreover, the non-uniformity coefficient (NUC) is proposed to characterize the disengaging uniformity of friction pairs. As the ATF temperature increases from 60 °C to 140 °C, the clutch disengaging duration shortens remarkably (shortened by 55.1%); besides, the NUC sees a decreasing trend before a slight increase. When the ATF temperature is 80 °C, the distribution of friction pair gaps is most uniform. During the disengaging process, the increase of ATF temperature not only accelerates the change of the lubrication status between friction pairs but also contributes to the decrease of contact torque and hydrodynamic torque. This research demonstrates for the first time, evidence for clutch disengaging dynamic characteristics with the consideration of ATF temperature.

ELECTROSPINNING OF ST. JOHN'S WORT OIL LOADED MICROCAPSULES BASED PVA NANOFIBERS

In this study, it was achieved that the production of St. John's Wort oil loadad Eudragit RS 100/PVA microcapsules by emulsion/solvent evaporation method and the microcapsules were embedded in PVA nanofibers. Morphological analysis was carried out with SEM images of both microcapsules and nanofibers. The presence of St. John's Wort oil, PVA and Eudragit RS 100 polymers were confirmed in the chemical structure of microcapsules and nanofibers by FT-IR. According to experimental studies, microcapsules were produced to have a smooth surface, a spherical shape and a uniform particle size. The PVA concentration was kept constant at 10% wt and microcapsule concentrations were applied as 1, 3, 5, 7, and 9 wt %. Then, polymer solution properties were measured, such as conductivity, viscosity, and surface tension. It was determined that viscosity and surface tension values increased with microcapsule concentration increase, while conductivity did not change significantly. Nanofiber production was realized via the electrospinning method under the optimum process parameters. According to the SEM images and histogram, nanowebs have a fine fiber diameter, smooth surface, high quality and no bead structure. In addition, the average microcapsule size is 30 μm, average fiber diameter is 430 nm and the fiber diameter uniformity coefficient is 1,014. It is thought that this nanofiber surface containing microcapsules embedded in St. John's Wort has the potential to be used as a wound dressing.

PARACETAMOL DRUG LOADED MICROCAPSULE BASED NANOFIBER PRODUCTION

In this study, it was aimed to production and characterization of paracetamol (PCT) loaded microcapsules and microcapsule added electro spun PVA nanofibers. Eudragit RS 100 and PVA were used as the shell in the microcapsule structure, and PCT was used as the core material. First of all, the PCT loaded Eudragit RS 100/PVA microcapsules were produced by solvent evaporation method under the optimum process parameters. Then, properties such as conductivity, viscosity and surface tension of the microcapsule loaded PVA solution were measured and the effects of microcapsule concentration on the solution properties were determined. According to the solution results, while the viscosity increased with the microcapsule concentration, conductivity and surface tension did not change significantly except for the PVA-10 sample. After the electrospinning process, fibre morphology was determined by SEM and incorporation of microcapsules into the nanofibers was clearly demonstrated. It was calculated from the SEM images that average microcapsule size is 9.81μm, average fibre diameter is 550 nm and fibre diameter uniformity coefficient is 1.025. Finally, the incorporation of PCT loaded microcapsules into the nanofibers was chemically confirmed by FT-IR analysis. It is thought that the results of this study will be useful for controlled drug release, especially in medical textiles.

Design and Performance Evaluation of a Stone Crusher

Crushers are essential machines in several industries for particle size reduction. They are invaluable in laboratories (higher institutions and research centres), the mining and construction industries. Available crushers are imported and very expensive. This has pushed some workers around Nigeria to crush stones with crude materials and manual labour, to meet the demand of the various sectors while neglecting the hazards involved. A hammer mill has been designed with due considerations to standard design requirements, local content and cost. The power required to crush granite with the desired through put of 400 kg/h was found to be 5.5 kW. Major factors considered for the material selection are the mechanical properties, wear of materials, fabrication requirement and cost. The machine was fabricated using locally available materials. The fabricated stone crusher was tested and the actual capacity was found to be 301 kg/h with a through-put efficiency of 75.4 %. The crushed products were well graded with 1.89 coefficient of gradation and uniformity coefficient of 10.22. The machine was produced at a cost of two hundred and forty-five thousand, two hundred naira (₦245,200.00 {US$595.15}).

Otomatisasi Sistem Fertigasi Tetes untuk Tanaman Berbasis Mikrokontroler

The process of manual fertilization and irrigation of plants has disadvantages such as it requires human labor and is inefficient in the use of fertilizers and water sources. Therefore, the purpose of this research is to design and develop an automatic fertigation system. The method used in this research is a drip fertigation technique where the fertigation liquid that has been stirred is placed in a tank with 100 cm height from ground. With the gravitational force, the fertigation liquid is distributed through pipes, hoses and emitters around the plant. While the control system and automation of fertigation distribution to plants is carried out based on a microcontroller that need the condition of soil moisture values around the plant. If the watering time and humidity values are met, the electronic valve will open so that the fertigation liquid flows from the tank to the plants. Furthermore, in this study the tests were carried out to determine the uniformity coefficient and debit of drip fertigation. From the results, it shows that the emitter’s debit influenced by the liquid level in the tank. The uniformity coefficient obtained in the two tests is greater than 90%. From the two tests carried out from the moisture sensor 1 and 2, it shows the mean percentage error for both sensor is less than 1.7%, while the percentage error of soil moisture sensor 1 is 1.6% and the percentage error of soil moisture sensor 2 is 1%, respectively. Meanwhile, from the ultrasonic sensor testing it was obtained 0% of error. It also shows from the testing conducted that the fertigation system works very well and successfully.

Evaluation of broiler dark house illumination systems, with and without thermal insulation

In the breeding of broiler house, the proper use of lighting systems has great influence on the welfare and the productivity of the birds. The objective was to evaluate two artificial lighting systems used in broiler house in terms of the allocative efficiency of luminance. One of the broiler house was closed with black raffia bag (dark house), without thermal insulation (NTI) and its lighting was composed of incandescent, compact fluorescent light (LFCs) and light emitting diode (LED) bulbs. The other broiler house was closed with extruded polystyrene panels (XPS) and thermally insulated (TI), and its lighting was composed of compact fluorescent lamps. The influence of external light of sun inside the broiler house was analyzed by means of exhaust holes and the degree of distribution of illumination through statistical analyzes and the study of the distribution uniformity coefficient (DUC). Contour maps were prepared showing the degree of internal luminance distribution for each broiler house, specifically in the area that did not suffer interference from external natural sunlight. The results showed that natural lighting influenced the internal lighting across the last 18 meters at the end of the broiler house and there was a more homogeneous lighting in the broiler house TI.