Thickness Improvement and Calibration Pressure Reduction of Stepped Tubular Components Using Axial Hydro-pressing Method

A new tube axial hydro-pressing method was proposed to solve the problems of high forming pressure and severely uneven wall thickness distribution of traditional tube hydroforming methods to form stepped tubular components. The forming pressure of the traditional hydroforming and the tube axial hydro-pressing method is studied theoretically, the mechanical model of the fillet area is established, and the forming pressure calculation formula is given. Based on this, an investigation of the tube axial hydro-pressing method is carried out by numerical simulation and experimental methods, and compared with the traditional tube hydroforming method. The key to the tube axial hydro-pressing method is to precisely control the relationship between the protrusion height and the axial feed, which is achieved by precisely controlling the feeding pressure and the axial displacement. Therefore, the constant pressure device in the experiment was used to eliminate the influence of the pressure rise caused by the volume compression on its cooperation relationship, to achieve accurate control of the loading path, eliminate wrinkles and flash defects. A qualified workpiece is successfully manufactured when the internal pressure is 18.0 MPa and the feed on each side is 15.0 mm. The forming pressure is reduced by 88.0%, and the feed is increased by 6.5%, which reduces the wall thickness reduction by 9.0%. The wall thickness difference of the workpiece can be controlled within 7.0%. The tube axial hydro-pressing method is suitable for forming stepped tubular components, which can achieve more replenishment at lower pressures, thereby effectively improving the uniformity of wall thickness and significantly reducing the forming pressure.

Effects of bearing lubrication conditions on rotor dynamic behavior

Usually, rotor dynamic analyses do not consider the effects of the lubricant supply condition, although this is an important aspect of journal bearing performance. Therefore, this work has implemented a mass-conserving model to realistically describe the oil feeding condition and evaluate its influence on rotor dynamics. This analysis was carried out by varying feeding pressure and groove position and the results indicate that the oil supply conditions significantly influence the bearing performance and affect the dynamic behavior of the entire rotor. In general, lower flow rates lead to a bearing with a greater stability region, as observed mainly in the bearing with a groove at 270° and, on the other hand, the increase in feeding pressure reduces the instability threshold.

Reductions in foliar Hemiptera in portions of a fescue grassland invaded by Smooth Brome (Bromus inermis)

Fescue grassland in Canadian prairie is characterized by Plains Rough Fescue (Festuca hallii), but the introduced exotic grass, Smooth Brome (Bromus inermis), is expanding therein. Hemiptera play an important role as herbivores in vegetation. In an invaded fescue grassland in Manitoba, 52 plant species had a combined average cover of 216%. Kentucky Bluegrass (Poa pratensis), another exotic grass, was most abundant at 64%, followed by B. inermis at 21% and the native grass F. hallii at 18%. Across 47 random sample points, B. inermis cover ranged from 0% to 180%. At these points, 2445 specimens of Hemiptera were collected by sweep net and divided into 99 morphologically distinct species. Bromus inermis cover had negative correlations with Hemiptera species richness and diversity, but not with abundance and biomass of Hemiptera. However, B. inermis cover was negatively correlated with abundance of two individual species of Hemipteran leafhoppers in the family Cicadellidae: Doratura stylata and Diplocolenus configuratus. Total graminoid cover had no significant correlation with any of the above Hemiptera variables. We conclude that feeding requirements deter some phytophagous Hemiptera from entering sections of fescue grassland invaded by B. inermis. In this way, invasion by B. inermis can be expected to modify ecosystem function by increasing feeding pressure on neighbouring natural vegetation and other introduced species.

GAMBARAN UMUM FEEDING PRACTICES YANG DITERAPKAN ORANGTUA PADA ANAK PICKY EATING

ABSTRACTPicky eating behavior in children cause distress for parents because the impacts on children's health and family eating activities. Picky eating can be influenced by feeding practices. Feeding practices consist of restriction / control feeding, pressure to eat, and child monitoring. The purpose of this scientific literacy study is to collect a general overview on the feeding practices that applied by parents of picky eating children. The research method is a literature review using studies obtained from several databases. There are 7 quantitative studies selected with participants aged 1-12 years, and using instruments to measure picky eating and feeding practices. The result shows that parents apply pressure to eat and restriction / control feeding in feeding practices in children who exhibit picky eating behavior. This research is expected to increase parental awareness about appropriate feeding practices implemented in order to reduce the risk of children experiencing picky eating.ABSTRAKPerilaku picky eating pada anak meresahkan orangtua karena dapat berdampak pada kesehatan anak dan proses kegiatan makan keluarga. Picky eating dapat dipengaruhi dari faktor lingkungan, salah satunya feeding practices. Feeding practices terdiri atas restriction/control feeding, pressure to eat, dan monitoring child. Tujuan kajian literasi ilmiah ini adalah mengumpulkan gambaran umum studi ilmiah tentang feeding practices yang diterapkan orangtua pada anak picky eating. Metode penelitian ini adalah kajian literatur dengan menggunakan studi yang diperoleh dari beberapa database. Terdapat 7 studi kuantitatif yang terpilih dengan partisipan dalam penelitian berusia 1-12 tahun, serta menggunakan instrument untuk mengukur perilaku picky eating pada anak dan feeding practice yang diterapkan orangtua. Hasil menunjukkan orangtua menerapkan pressure to eat dan restriction/control feeding dalam feeding practices pada anak yang menunjukkan perilaku picky eating. Penelitian ini diharapkan dapat meningkatkan kesadaran orangtua mengenai feeding practice yang tepat diterapkan agar mengurangi resiko anak mengalami picky eating.

A New Industrial Technology for Mass Production of Graphene/PEBA Membranes for CO2/CH4 Selectivity with High Dispersion, Thermal and Mechanical Performance

Polyether block amide (PEBA) nanocomposite membranes, including Graphene (GA)/PEBA membranes are considered to be a promising emerging technology for removing CO2 from natural gas and biogas. However, poor dispersion of GA in the produced membranes at industrial scale still forms the main barrier to commercialize. Within this frame, this research aims to develop a new industrial approach to produce GA/PEBA granules that could be used as a feedstock material for mass production of GA/PEBA membranes. The developed approach consists of three sequential phases. The first stage was concentrated on production of GA/PEBA granules using extrusion process (at 170–210 °C, depending on GA concentration) in the presence of Paraffin Liquid (PL) as an adhesive layer (between GA and PEBA) and assisted melting of PEBA. The second phase was devoted to production of GA/PEBA membranes using a solution casting method. The last phase was focused on evaluation of CO2/CH4 selectivity of the fabricated membranes at low and high temperatures (25 and 55 °C) at a constant feeding pressure (2 bar) using a test rig built especially for that purpose. The granules and membranes were prepared with different concentrations of GA in the range 0.05 to 0.5 wt.% and constant amount of PL (2 wt.%). Also, the morphology, physical, chemical, thermal, and mechanical behaviors of the synthesized membranes were analyzed with the help of SEM, TEM, XRD, FTIR, TGA-DTG, and universal testing machine. The results showed that incorporation of GA with PEBA using the developed approach resulted in significant improvements in dispersion, thermal, and mechanical properties (higher elasticity increased by ~10%). Also, ideal CO2/CH4 selectivity was improved by 29% at 25 °C and 32% at 55 °C.

Coal Desliming Using Annular Rinse Water Hydrocyclone

The separation of fine coal can be improved by pre-desliming, which was significantly enhanced when fine coal was processed using a Falcon concentrator, and <45-μm coal slime was removed. Ultrafine classification tests using Krebs classification cyclone with annular rinse water showed that the increase in feeding concentration negatively affected the efficiency of classification while increasing the classification size because the settling was hindered by the high underflow concentrations. The optimization experiments with response indicators of classification efficiency based on orthogonal design using Design-Expert software indicated that the optimal classification efficiency reached 91.32% with a feeding pressure of 0.03 MPa, a rinse water pressure of 0.02 MPa, and a feeding concentration of 12.5%. Meanwhile, the classification size was 49.99 μm, which agreed well with the predicted value.

Bubble Size Distribution Characteristics of a Jet-Stirring Coupling Flotation Device

In this study, a new jet-stirring coupling flotation device that incorporates the advantages of three conventional flotation machines (specifically, Jameson cell, mechanical flotation cell, flotation column) was designed based on jet suction. The suction capacity of a double cosine self-aspirated nozzle utilized by the device was analyzed under different feeding pressures, and the effects of frother concentration, feeding pressure, suction capacity, and height of sampling location on the bubble size distribution (BSD) were investigated using a high-speed video system. It was found that a large amount of air was sucked into the flotation cell by the self-aspirated nozzle arranged in a non-submerged manner, which met the requirements of flotation in terms of the suction amount of air. The suction capacity showed a positive linear correlation with negative pressure inside the nozzle. When the Methyl isobutyl carbinol (MIBC) concentration reached the critical coalescence concentration (CCC), the bubble size stabilized at approximately 0.31 mm, which was smaller than the bubble size produced by the conventional flotation machine. This indicated that bubbles suitable for flotation were generated. D32 linearly decreased with increasing of feeding pressures and conversely increased with increasing suction capacities and sampling location heights, independent of the frother concentration.