This work reports on a chemical precipitation experiment to produce nanocrystalline calcium hydroxyapatite (Ca-HA) using a calcium carbonate precursor derived from green mussel shells. Ammonium biphosphate and phosphoric acid were mixed with the precursor, achieving a pH of 13–14 by stirring magnetically at 30 °C for 48 hours. The nanocrystalline Ca-HA product (8–13 nm) was validated through X-ray diffraction and Fourier-transform infrared spectroscopy with an average calcium-to-phosphorus ratio molar of 1.8, influencing the thermal stability according to thermogravimetric and differential thermal analysis. Green mussel shell wastes are a recyclable calcium resource potentially used to synthesize nanocrystalline hydroxyapatite.

The main chemical components of waste cow bones are apatite minerals, especially those containing calcium and phosphorus. This study investigated whether this bone could produce extracted hydroxyapatite through calcining at 900 degrees C for different holding times (1-6 h). An average mass loss of 45% occurred in this experiment during the preparation of bone powders, which involved crushing and further calcining at this temperature. The quantitative XRD analysis showed that 99.97 wt.% hydroxyapatite and over 0.3 wt.% calcite were present in the raw and as-calcined bone powders, with trace amounts of CaFe3O5 (calcium ferrite) phases appearing in the calcined product. Depending on the holding calcining times, SEM images of the calcined bovine powders revealed aggregate sizes ranging from 0.5-3 mu m and crystallite (grain) sizes ranging from 70 to 340 nm in all calcium-phosphate powder products. Following EDX analysis of all sample surfaces, possible calcium-deficient hydroxyapatite instead of hydroxyapatite formed, as evidenced by the calcined product's Ca/P ratio exceeding 1.67. Additionally, calcining cow bones for 5-6 h at 900 degrees C yielded a high-purity nano-crystalline hydroxyapatite powder precursor in biomedical applications.

A substantial amount of dry solid waste residues in Indonesia produced during the extraction of asphalt-rock bitumen offers the potential for calcium recovery for reducing CO₂ emissions toward value-added carbonate minerals via indirect mineral carbonation. This study used the residue by crushing and calcining at 900 °C for 5 hours, leached with 2 M HCl and 1 M H2SO4 at 60 °C to form a calcium-rich solution, and mixed with NH4HCO3 at a pH of 11.2–12 to precipitate calcium carbonate (PCC) at varying 30–70 °C. The PCC product has substantial calcite and small vaterite with spherical morphology, potentially various applications in paper and plastic-making industries.

The tribological performance of tire such as braking capacity (related to contact force) and abrasion resistance (related to surface stress) can be identified through the investigation of the friction contact between tire and road. However, it is difficult to investigate the distribution of contact forces and stress of the tire surface experimentally. As a friction contact model between a tire tread and road surface, a tread block model in contact with a rigid surface is studied here numerically to investigate the distribution of contact forces and stress on its surface. The tread material is a Reinforced Styrene Butadiene Rubber and depicted as a plane strain shape of 15 mm x 10 mm dimension. Analysis was carried out in a constant sliding speed of 300 mm/s with various depths of indentation. Mechanical properties of tread block material was modelled as a hyper -elastic type. The contact forces and stress distribution on the tread block surface were obtained. Results show that dynamic or stick -slip phenomena are observed along friction contact. With respect to the tread block surface coordinate, the surface stress at leading edge is much larger than trailing edge.

The term “contact area” refers to the total surface area of two entities in direct physical touch. When discussing an artificial hip joint, “contact area” refers to the surface area of contact between the components of the artificial hip joint (ball and cup) positioned inside the patient. Several methods can be used to figure out the contact area of an artificial hip joint, such as finite element analysis and traditional experiments on contact mechanics with hip joint simulators. The contact area in an artificial hip joint ensures load distribution. For optimal and long-term performance, the prosthetic hip joint’s contact area must be well understood for design, fitting, and monitoring. This study presented a novel method to estimate the liner surface contact area due to interaction contact in the artificial hip joint using a computer-aided design (CAD) program. This study also contrasted numerical approaches utilizing computer-aided engineering software and theoretical predictions based on Hertz theory with three-dimensional processes using CAD software to determine the contact area in the inner liner. There were no significant discrepancies in the outcomes of the three approaches.

BACKGROUND The four components that make up the current dual-mobility artificial hip joint design are the femoral head, the inner liner, the outer liner as a metal cover to prevent wear, and the acetabular cup. The acetabular cup and the outer liner were constructed of 316L stainless steel. At the same time, the inner liner was made of ultra-high-molecular-weight polyethylene (UHMWPE). As this new dual-mobility artificial hip joint has not been researched extensively, more tribological research is needed to predict wear. The thickness of the inner liner is a significant component to consider when calculating the contact pressure. AIM To make use of finite element analysis to gain a better understanding of the contact behavior in various inner liner thicknesses on a new model of a dual-mobility artificial hip joint, with the ultimate objective of determining the inner liner thickness that was most suitable for this particular type of dual-mobility artificial hip joint. METHODS In this study, the size of the femoral head was compared between two diameters (28 mm and 36 mm) and eight inner liner thicknesses ranging from 5 mm to 12 mm. Using the finite element method, the contact parameters, including the maximum contact pressure and contact area, have been evaluated in light of the Hertzian contact theory. The simulation was performed statically with dissipated energy and asymmetric behavior. The types of interaction were surface-to-surface contact and normal contact behavior. RESULTS The maximum contact pressures in the inner liner (UHMWPE) at a head diameter of 28 mm and 36 mm are between 3.7-13.5 MPa and 2.7-10.4 MPa, respectively. The maximum von Mises of the inner liner, outer liner, and acetabular cup are 2.4-11.4 MPa, 15.7-44.3 MPa, and 3.7-12.6 MPa, respectively, for 28 mm head. Then the maximum von Mises stresses of the 36 mm head are 1.9-8.9 MPa for the inner liner, 9.9-32.8 MPa for the outer liner, and 2.6-9.9 MPa for the acetabular cup. A head with a diameter of 28 mm should have an inner liner with a thickness of 12 mm. Whereas the head diameter was 36 mm, an inner liner thickness of 8 mm was suitable. CONCLUSION The contact pressures and von Mises stresses generated during this research can potentially be exploited in estimating the wear of dual-mobility artificial hip joints in general. Contact pressure and von Mises stress reduce with an increasing head diameter and inner liner's thickness. Present findings would become one of the references for orthopedic surgery for choosing suitable bearing geometric parameter of hip implant.

In contact mechanics analysis, load, deformation, friction, and residual stress are important variables that need to be considered to understand the behavior of materials under contact for application in biomedical industry. This study investigated the effect of load, diameter ratio, and friction coefficient on the contact behavior between two hemispheres of equal hardness. The finite element method (FEM) used in this study incorporated variations in load (2500 N, 5000 N, and 8000 N) and friction coefficient (0, 0.05, 0.1, 0.4, 0.8) to detect the impact of these factors on residual stress and deformation springback in the diameter ratio ranging from 1 to 5. The upper hemisphere had a constant diameter, while the diameter of the bottom hemisphere was varied according to the chosen diameter ratio. The results showed that an increase in the diameter ratio caused a decrease in the deformation ratio, indicating that smaller hemispheres experienced an increase in deformation. The study also found that the model showing springback will decrease with increasing load and diameter ratio. The load and diameter ratio affected the springback and residual stress of the hemispheres. Large loads led to reduced springback and high residual stress. Higher diameter ratios resulted in lower springback and wider residual stress distribution in the bottom hemisphere and reduced residual stress distribution in the upper hemisphere. The friction coefficient also affected the residual stress distribution. Therefore, appropriate load, diameter ratio, and friction coefficient selection are crucial factors for producing high-quality products in biomedical industry.

In the industrial sector, bearings are a common machine component used to maintain the relative motion between two components. The performance of journal bearings is expected to enhance due to technological advancements resulting from the development of high-speed and high- load machines. Considering the complexity of flow in journal bearings, numerical simulations can be used to analyze and improve tribological performance of journal bearings. However, utilizing numerical simulation to predict the actual operating conditions of a journal bearing is not always error-free. The parameters taken into account during simulation affect how closely the results match actual conditions. The simulation results of journal bearing performance are affected by a number of factors, including flow turbulence, cavitation, thermal effect, and slip. In this study, such factors are modeled and explored in greater depth using a computational fluid dynamics (CFD) approach to determine how important each modeling is to the results. The simulation results are validated with the experimental work in the available reference. The findings of this study demonstrate the importance of incorporating the combined influence of cavitation, slip, and thermal effects in order to ensure that computational fluid dynamics (CFD) predictions accurately represent the real-world operating conditions of journal bearings.

The study presented a powder processing method involving calcination and subsequent carbonation in the synthesis of precipitated calcium carbonate (PCC) for recycling green mussel shells, which contain a high calcium carbonate content. The purity of portlandite [Ca(OH)2] as a result of calcination and subsequent moisture absorption during storage was verified using the XRD-Rietveld method. Further quantitative XRD Rietveld analysis of the PCC product confirmed the presence of vaterite (55.20 wt.%) and calcite (44.80 wt.%) minerals after carbonation process of the calcined powder product. The SEM examination of this product revealed particle aggregates of non-uniform polyhedral and cubical grains of varying small and large sizes. The FTIR analysis also confirmed that calcination and subsequent hydration of mussel shell powder yielded pure portlandite, whereas the carbonation yielded PCC polymorphism. As a result, this powder processing method is simple to scale and reduces the cost of PCC synthesis, which is critical for practical applications. The current study demonstrated that the powder processing method for recycling green mussel shells as starting materials in biomedical applications is technically feasible.

TRIZ, also known as the theory of innovative problem-solving, has garnered attention from several proponents who advocate its merits as a systematic technique or toolkit that offers a rational framework for fostering creativity in pursuing innovation and creative problem-solving. The broad range of tools and procedures used in the TRIZ-based innovating enable the effective development of next-generation items while successfully enhancing existing ones. Using these tools and approaches may also facilitate the development of the necessary functionality and mitigate the costs associated with manufacturing processes, hence allowing the introduction of novel and enhanced products to be introduced into the market. This study aims to employ the TRIZ approach to develop an optimal laparoscopic chair design. The design of the laparoscopic chair was with a particular emphasis on ease and usability. The laparoscopic chair's design demonstrated adherence to ergonomic principles despite the absence of actual ergonomic testing. This design has the chair's adjustable components, which allow for height and level modifications, as well as customizable positioning to accommodate the preferences of the seated individual. The outcome of this design is comparable to laparoscopic chairs offered by medical corporations and preparing for the prototyping phase.

This study investigated the recycling of solid waste residues from rock asphalt extraction via 5-hour calcination at 900 °C and indirect carbon mineralization. The calcined powder was first dissolved at 60 °C in 2 M CH3COOH, carbonized in NH4HCO3, and agitated at 1200 rpm in 2 M NaOH for 30 minutes at 30–60 °C and pH 12. The precipitated calcium carbonate (PCC) results are calcite (24.4–56.3 wt.%) and vaterite (75.6–3.7 wt.%), as confirmed by XRD analysis, carbonate FTIR spectra, and SEM images of prismatic calcite and spherical vaterite. This high-value PCC product has potential industrial applications, such as paper and plastics.

The single mobility bearing as a previous bearing design of total hip prosthesis has severe mobility constraints that can result in dislocation during Muslim (people who follow the Islam as religion) prayer movements, specifically shalat that requires intense movement. There are five intense movements (i.e., bowing, prostration, sitting, transition from standing to prostration, and final sitting) during Muslim prayer that may generate an impingement problem for patients with total hip prosthesis. In this work, textured dual mobility total hip prosthesis with two textured cases (i.e., textured femoral head and textured inner liner) are presented and their performances are numerically evaluated against untextured surface model during Muslim prayer movement. The concave dimple design is chosen for surface texturing, while for simulating femoral head materials, SS 316L and CoCrMo is choosen. To represent the real condition, three-dimensional computational fluid dynamics (CFD) coupled with two-way fluid–structure interaction (FSI) methods are employed to analyze elastohydrodynamic lubrication problem with non-Newtonian synovial fluid model. The main aim of the present study is to investigate the tribological performance on dual mobility total hip prosthesis with applied textured surface with concave dimple in femoral head and inner liner surface under Muslim prayer movements. It is found that applying surface texturing has a beneficial effect on the lubrication performance for some intense movements. The textured femoral head model performs better than textured inner liner model and untextured model (both femoral head and inner liner). The numerical results also indicate superior performance of CoCrMo femoral head compared to SS 316L femoral head. These findings can be used as a reference for biomedical engineers and orthopedic surgeons in designing and choosing suitable total hip prosthesis for Muslims makes they can carry out Muslim prayer movements like humans in general who have normal hip joints.

Resources recovery of calcium and phosphates from respective green mussel shells and bovine bones by calcination and chemically extracting are viable precursors for carbonate-rich apatite biomedical material applications. Because of their high osteoconductivity, carbonate-rich apatite bioceramics are being studied intensively for synthetic bone transplants. In the study, powder processing routes of calcination and following chemical dissolution in MgCl2 and H2SO4 were each for recovering calcium of mussel shells and phosphate of bovine bones yielding a crystal-forming solution feedstock for use in microwave-irradiated synthesis. FTIR spectra and XRD patterns validated the crystallinity and phase identification for as-synthesized powders. As a result, the presence of CO3, PO43-, and OH- bands in carbonate-calcium phosphate complexes were present in FTIR spectra. According to the XRD Rietveld method, the as-synthesized powder product contained brushite, carbonated hydroxyapatite (CHA), calcite, and gypsum. The recoverable CHA crystallites' size was 40 nm. This present study demonstrated that microwave irradiation synthesis of CHA powder with calcium and phosphates derived from mussel shells and bovine bones is the potential to yield a large amount of CHA for bioceramics and would aid in the design of a powder processing step for preparing the CHA powder precursor in biomedical applications.

This study examines the biomechanical implications of lubricants trapped in deformable sinusoidal valleys under loading and unloading against rigid flats using the finite element method (FEM). This phenomenon is similar to the intervertebral discs in the spine under loading-unloading conditions. Materials are assumed to be elastic-perfectly plastic, and lubricants are modelled as either compressible or incompressible. The contact area, deformation, and von Mises stress have been discussed in this study. The result showed good agreement with the past research in the dry conditions and the trapped fluid in the incomplete filling during loading conditions. The incomplete filling is the condition of the sinusoidal valley volume being bigger than the lubricant volume. Additional lubricant reduces the contact area and deformations in the loading conditions while shrinking the von Mises stress distribution. For dry and lubricated contact, the most significant decline in contact area, deformation, and von Mises stress distribution is observed in incompressible conditions. Additional lubricant reduces contact area and deformations and shrinkage of the von Mises stress distribution in the complete filling. The findings are necessary for understanding joint mechanics and the durability of biomedical implants.

Everyone agrees that there must be some contact for wear, and extreme contact pressuresPressure beyond the yield limit will cause overload damage, making material failure worse. But different pieces of evidence have led to different conclusions for the middle range of contact pressuresPressure. Even though there are advanced modeling techniques, many researchers still do not know about contact pressurePressure, especially when it comes to metal-on-polyethylene articulations on dual-mobilityMobility cups. This study used finite element analysis to aim at contact pressurePressure on some small femoral head diameters paired with different thicknesses of the polyethylene liner on dual mobilityMobility cups for Asians. During the normal gait cycle, contact pressurePressure analysis was done at each head-to-liner ratio. The research results can be used to determine the best head size and the inner liner’s thickness.

Introduction: This study presents a novel weighted vest integrated with vibrotactile stimulation for deep pressure therapy. Following the principles of Morrison's research, we assessed its effectiveness in calming users with four distinct vibration patterns. Method: Ten male participants without ASD history, aged 19-25 and weighing 48-73 kg, provided subjective evaluations using the Comfort Rating Scale (CRS). Result: Results showed that participants reported increased calmness after using the device, as evidenced by the overall ratings of the "calming" term, with the "down" pattern receiving the highest ratings. The study advocates for future work involving physiological sensors to measure the device's effectiveness objectively. While promising, this innovation has limitations, such as fixed vibration frequency and reliance on an adapter for power. Future iterations could address these issues to enhance the device's portability and customizable vibration frequencies. Conclusion: This research contributes to deep pressure therapy and vibration therapy by focusing on responsive patterns and subjective evaluations, opening doors for future developments.

Ca-source of green mussel shells (Perna-Viridis) recovered into precipitated calcium car-bonate (PCC) powders via a calcination-dissolution-precipitation pathway is a prospective feedstock for the rapid synthesis of monocalcium phosphate monohydrate (MCPM). In the study, a potential aqueous crystallization process was implemented for MCPM synthesis by blending PCC powders with vaterite (55.20 wt %) and calcite (44.80 wt%) in strongly phos-phoric acid with a molarity of 85% (w/w) and varying amounts of water (2-6 mL), followed by rapid evaporation and drying. The resulting product contained at least 90 wt % MCPM and minor monetite according to XRD and FTIR analyses. The morphology of the MCPM product is a prismatic-like shape with grain sizes ranging from 3 to 9 mm, as observed using SEM techniques. DTA/DTG/TG analysis confirms the stability of MCPM products at tem-peratures up to 100 degrees C providing benefits for food industries and communities as a stable food additive commodity.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Waste crab shells (CS) have the potential to mineralize CO2, yielding precipitated calcium carbonate (PCC) powder feedstock for use in the synthesis of monocalcium phosphate monohydrate (MCPM) in an acidic condition by partial neutralization of phosphoric acid at 90 degrees C and varying times (30-120 min), followed by evaporation of the water at 100 degrees C. The PCC and MCPM products were analyzed using X-ray powder diffraction, Fourier transform infrared spectroscopy, and the scanning electron microscopy/energy dispersive X-ray method. After 120 min of stirring, the pure MCPM revealed uniform particle sizes from 1 to 3 mu m. The presented MCPM synthesis using the PCC powder precursor may assist in developing a large-scale MCPM industry while recycling a considerable quantity of CS waste.

Musculoskeletal disorders frequently occur in various types of work, including laparoscopic surgeons. The surgeon profession is classified as a high-risk occupation and may have musculoskeletal disorders. Surgeons who suffer from these disorders experience illnesses ranging from mild to severe because the muscles often receive long-term static loads. These causes can be prevented when working in a seated position. In this work, the investigation being conducted is to design a chair as a surgeon's aid that consists of a base platform, seat height adjustment mechanism, seat cushion, backrest, and handrest. In this paper, a rectangular platform is analyzed using a finite element model. The analysis results by considering the structure as a truss produce the largest stress of 34 MPa compared the structure as a frame of 30 MPa. These two approaches lead to the conclusion that the structure computed as a truss is more secure than the analysis of the structure as a frame.