Piston ring assembly for a new natural gas vehicle symmetrical multistage wobble-plate compressor

Natural gas is an alternative fuel of choice in the market today due to the increase in the price of petroleum, as well as out of environmental concerns. Pressure requirement for a natural gas vehicle (NGV) storage tank is 3000 psig (206 bars). Thus, at NGV refueling facilities, the natural gas need to be stored at a higher pressure in order to refuel the NGV at the pressure required. Compressors are needed in the compression process at the refueling facilities. A new compressor design for natural gas refueling appliance has been developed which is the symmetrical multistage wobble-plate compressor. This compressor design is the newest variation of the axial reciprocating piston compressor. The success of the compressor design in compressing gas depends on the piston ring assembly design. Through this paper, the process of designing the piston ring assembly and considerations taken for this new compressor design were explained. The results presented are those from preliminary tests using air on the working fluid. Real tests on natural gas are to be organised utilising all the experience and lesson learnt from that on air

Contact pressure analysis of acetabular cup surface with dimple addition on total hip arthroplasty using finite element method

This research aims to analyze the contact pressure on acetabular cup surface with dimple addition and without dimple addition. The main contribution in this research is to explore the influence of dimple addition to contact pressure that affects implant lifetime. The simulation is carried out by giving fully 3D physiological loading of the hip joint under normal walking conditions. Contact pressure analysis conducted on dry contact condition and meshing with the two-pole method performed to provide a comprehensive contact pressure result. The results show that the total hip arthroplasty model with dimple addition can reduce contact pressure for all phases in one full cycle with average decreased by 15.53% which indicates that adding dimple to the contact surface in the total hip arthroplasty bearing can extend the life of implant use

Uniaxial and multiaxial fatigue life prediction of the trabecular bone based on physiological loading: a comparative study

Fatigue assessment of the trabecular bone has been developed to give a better understanding of bone properties. While most fatigue studies are relying on uniaxial compressive load as the method of assessment, in various cases details are missing, or the uniaxial results are not very realistic. In this paper, the effect of three different load histories from physiological loading applied on the trabecular bone were studied in order to predict the first failure surface and the fatigue lifetime. The fatigue behaviour of the trabecular bone under uniaxial load was compared to that of multiaxial load using a finite element simulation. The plastic strain was found localized at the trabecular structure under multiaxial load. On average, applying multiaxial loads reduced more than five times the fatigue life of the trabecular bone. The results provide evidence that multiaxial loading is dominated in the low cycle fatigue in contrast to the uniaxial one. Both bone volume fraction and structural model index were best predictors of failure (p < 0.05) in fatigue for both types of loading, whilst uniaxial loading has indicated better values in most cases

The effect of bottom profile dimples on the femoral head on wear in metal-on-metal total hip arthroplasty

Wear and wear-induced debris is a significant factor in causing failure in implants. Reducing contact pressure by using a textured surface between the femoral head and acetabular cup is crucial to improving the implant’s life. This study presented the effect of surface texturing as dimples on the wear evolution of total hip arthroplasty. It was implemented by developing finite element analysis from the prediction model without dimples and with bottom profile dimples of flat, drill, and ball types. Simulations were carried out by performing 3D physiological loading of the hip joint under normal walking conditions. A geometry update was initiated based on the patient’s daily routine activities. Our results showed that the addition of dimples reduced contact pressure and wear. The bottom profile dimples of the ball type had the best ability to reduce wear relative to the other types, reducing cumulative linear wear by 24.3% and cumulative volumetric wear by 31% compared to no dimples. The findings demonstrated that surface texturing with appropriate dimple bottom geometry on a bearing surface is able to extend the lifetime of hip implants

Odor clustering using a gas sensor array system of chicken meat based on temperature variations and storage time

Shelf life and temperature are two things that affect the freshness of meat. Generally, people identify the freshness of meat by looking at the texture, color, and even aroma of meat. These methods have less effective approaches to identify the freshness of meat. The limitations of the human sense of smell have led to the development of gas sensor array system technology. Research has been done on odor cluster analysis using gas sensor array with variations in shelf life and temperature in classifying the smell of chicken meat. The study used a sample of 20 g of chicken meat in a 150 ml bottle which was sensed using a gas sensor array system at a certain storage period and temperature. The shelf life used is a shelf life of 0 h, 6 h, 12 h, 18 h, and 24 h as well as variations in temperature 4 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C. The analysis is carried out using machine learning in the form of principal component analysis and deep neural network. In this study using the principal component analysis and deep neural network method, it can be seen that the gas sensor array is able to classify well. Meanwhile, the results of deep neural network model can be classified as fresh and unfresh chicken meat with a testing accuracy of 98.70%. The result showed that gas sensor array could classify chicken meat with high accuracy and the proposed method provides a significant improvement

An in-vivo study of photobiomodulation using 403 nm and 649 nm diode lasers for molar tooth extraction wound healing in wistar rats

Purpose This study aims to examine the effects of red 649 nm 4 J/cm2 and blue 403 nm 8 J/cm2 diode laser treatment for post-extraction wounded healing in rats through histopathological and immunohistochemical analysis. Methods Samples of 54 Wistar rats were divided into six groups: C- control group without treatment; C + wounded group without treatment; TB wound group with Povidone-iodine treatment; TD wounded group with doxycycline treatment; TLB wounded group with 403 nm diode laser treatment; and TLR wounded group with 649 nm diode laser treatment. Mandibular samples were observed for the number of lymphocytes and fibroblasts cells, new blood vessels formation, Interleukin 1β, and Collagen 1α expression level. Results Based on the histopathological test results, red laser diode treatment significantly increased the number of lymphocyte, fibroblast cells and the formation of new blood vessels. Meanwhile, immunohistochemical tests showed an increase in the expression of the Colagen-1α protein which plays a role in the formation of collagen for new tissues formation after damage, as well as a decrease in Interleukin-1β expression level. Blue laser is also able to show a positive effect on wound healing even though its penetration level into the tissue is lower compared to red laser. Conclusion The red diode laser 649 nm has been shown to accelerate the process of proliferation in wound healing post molar extraction based on histopathological and immunohistochemical test results

The compressive strength and static biodegradation rate of chitosan-gelatin limestone-based carbonate hydroxyapatite composite scaffold

Background: One of the main components in tissue engineering is the scaffold, which may serve as a medium to support cell and tissue growth. Scaffolds must have good compressive strength and controlled biodegradability to show biological activities while treating bone defects. This study uses Chitosan-gelatin (C–G) with good flexibility and elasticity and high-strength carbonate hydroxyapatite (CHA), which may be the ideal scaffold for tissue engineering. Purpose: To analyze the compressive strength and static biodegradation rate within various ratios of C–G and CHA (C–G:CHA) scaffold as a requirement for bone tissue engineering. Methods: The scaffold is synthesized from C–G:CHA with three ratio variations, which are 40:60, 30:70, and 20:80 (weight for weight [w/w]), made with a freeze-drying method. The compressive strengths are then tested. The biodegradation rate is tested by soaking the scaffold in simulated body fluid for 1, 3, 7, 14, and 21 days. Data are analyzed with a one-way ANOVA parametric test. Results: The compressive strength of each ratio of C–G:CHA scaffold 40:60 (w/w), 30:70 (w/w), and 20:80 (w/w), consecutively, are 4.2 Megapascals (MPa), 3.3 MPa, 2.2 MPa, and there are no significant differences with the p= 0.069 (p>0.05). The static biodegradation percentage after 21 days on each ratio variation of C–G:CHA scaffold 40:60 (w/w), 30:70 (w/w), and 20:80 (w/w) is 25.98%, 24.67%, and 20.64%. One-way ANOVA Welch test shows the result of the p-value as p<0.05. Conclusion: The compressive strength and static biodegradation of the C–G:CHA scaffold with ratio variations of 40:60 (w/w), 30:70 (w/w), and 20:80(w/w) fulfilled the requirements as a scaffold for bone tissue engineering

Mechanical degradation model of porous fe scaffold: simulation approach

This paper proposes a simple degradation model that estimates morphological changes in pure iron scaffolding due to surface erosion. The main contribution of this work is to estimate the degradation of porous pure iron scaffolding and analyze the impact of morphological changes on mechanical properties. In this study, the pure iron scaffolding model was designed in CAD software with 3 different porosity such as 30%, 41%, and 55% respectively. The geometry images of CAD models with a resolution of 3316 x 5530 pixels are captured layer by layer with a thickness of 0.02 mm. The purpose of this method is to replace the function of the u-CT scanning technique. Two-dimensional morphological erosion is applied to reduce the number of pixels of the image model. This erosion process is adjusted iteratively with increasing number of pixels to erode the image model until the volume of the scaffold after reconstruction matches the volume of the model undergoing mathematical calculations. Their changes in the volume of scaffold geometry and degradation of mechanical properties were evaluated using finite element analysis. This study found that mechanical properties such as elastic modulus and yield strength decreased systematically during the 19 week degradation period. In addition, deformation analysis is performed on models based on finite element analysis

Design and development of multistage symmetrical wobble compressor

There are many types of compressor design based on variation applications from the low pressure to the high pressure compression. For the high pressure application, the horizontal opposed reciprocating compressor is the most popular. However, for the smaller flow-rate natural gas refueling appliance compressors, scotch-yoke type has just been introduced into the market. Judging from the advantages and disadvantages from these compressor types, the wobble-plate and swash-plate compressor were chosen to be the combined concept for development of the new compressor. Both compressor concepts are currently used only for low pressure application with single stage compression. For this new compressor design development, both compressor types were combined to develop into a new symmetrical multi-stage wobble-plate compressor. The new compressor design operates with the suction pressure of 3 bar and discharge pressure of 206 bar. This new compressor design inherits the advantages of the wobble-plate and the swashplate compressor which are compact and able to operate at high operating speed. Main improvement in this new compressor design is the introduction of the symmetrical wobble-plate configuration which allows for higher compressor capacity and balanced horizontal forces. The rotor concept from the swash-plate compressor has also been adopted in this new design. The normal connecting rod with the two ended ball joints has been replaced by the connecting rod with standard end-joints at both ends. This has eased the manufacturing process as the end-joints are available on the shelves. However, this standard universal end joint has limit the tilting angle of the wobble plate to a maximum of 16º. Against this limitation and for the compressor to operate with minimum possible operating torque and optimum pressure ratio, analysis conducted concludes that the optimum number of stages is five. Flow analysis was conducted to simulate pressure and gas velocity distributions. This has helped in the conceptual development and this design of the suction and discharge port, the value and the cylinder of each stage. Heat transfer analysis was also conducted to simulate the temperature distribution on the cylinder block. The predicted temperature is about 302ºC at the first stage. Temperature rise due to compression of the air for both prototypes was found to be insignificant. As such the inter-cooler and after-cooler provided were found unnecessary and were not used. Both prototypes operated with good stability at all speeds and noise generated was acceptably low. The 1.00 m3/hr prototype compressor was run at 1100 rpm producing a discharge pressure of 260 bar and for flow rates of 10 m3/hr was run at 400 rpm producing a discharge pressure of 180 bar