Bed Of Springs Research Articles

Recent developments in computational modelling of the knee

ObjectiveModel calculations of knee joint loading range from an assumption of perfectly rigid articular surfaces to more realistic simulations of cartilage and meniscal deformation. Rigid-body musculoskeletal models simulate knee contact mechanics using the ‘bed of springs’ method from elastic foundation theory whereas finite-element models discretise each structure into a series of interconnected elements and ascribe material properties to each element. This mini-review describes some of the most recent developments in computational modelling of knee contact mechanics and suggests possible avenues for future improvements. DesignNarrative mini-review. ResultsMuscle and joint contact forces can be calculated synchronously at a reasonable computational cost (typically a few hours of CPU time) using rigid-body models and elastic foundation theory whereas similar calculations using fully deformable finite-element models can take several days and even weeks. The main computational expense incurred in finite-element musculoskeletal modelling is the solution of a muscle-force optimization problem. ConclusionCalculation of muscle and joint contact forces within the framework of a finite-element musculoskeletal model remains challenging. Integrating biomechanical data from human motion experiments with fully deformable finite-element models to simulate knee contact mechanics during dynamic activity is an evolving science. Future work should explore the use of efficient methods such as direct collocation to perform muscle-driven dynamic optimization simulations of movement using finite-element musculoskeletal models. Dynamic optimization may be combined with finite-element modelling to enable predictive simulations of movement so that the effects of changes in musculoskeletal anatomy on knee contact mechanics can be studied more systematically.

Dynamic behaviour of carbon-nanotube reinforced functionally graded double-arch systems

The goal of the current investigation is to determine the dynamic behaviour of double-arch systems: the system is made of two arches reinforced by three different functionally graded patterns of carbon nanotubes and connected with an elastic layer of spring bed. The carbon-nanotube functionally graded patterns considered are uniformly distributed, FG-X and FG-O. Two different boundary conditions of movable and immovable simply supported (named SS1 and SS2) are studied for the reinforced double-arches, where the displacements along the curve-line are constrained for the ends of SS2 arches. Both the Hamilton principle and force-moment technique are utilised to formulate the coupled equations of motion. A series expansion technique is then used to solve the equations. A validation is performed and consistent agreement between the proposed methodology and simplified version of the double-arch system is achieved. One prominent observation arising from this study is that an increase in the opening angle of the double-arch system results in a decline in both the series for the transverse natural frequencies for SS1. Conversely, the systems with SS2 boundary conditions exhibit an initial rise in both the series of natural frequencies as the opening angle increases, followed by a gradual decrease. A thicker carbon-nanotube reinforced functionally graded double-arch system demonstrates an increased natural-frequency sensitivity to variation in opening angles. Lastly, increasing the elastic layer coefficient of stiffness causes an increment in the second series natural frequency of the system.

Spring Bed Business as a Livelihood for the People of Sei Semayang Village, Sunggal District, Deli Serdang Regency

The research aims to describe the reasons why the people of Sei Semayang Village chose the spring bed business as a livelihood, as well as outlining strategies for running a spring bed business as a livelihood. Qualitative research method with a descriptive approach, data collection techniques used in the research are interviews, observation, documentation carried out to add relevant data. The research method used from the research results is as follows: 1. Gaining knowledge from experience while working as an employee in a spring bed business owned by another entrepreneur is the reason people choose business as a livelihood. Fulfilling economic needs by choosing the spring bed business as a livelihood for people affected by the Covid-19 pandemic. Obtaining large profits is the reason why people run the spring bed business as a livelihood. The ease of making and obtaining raw materials by the community is the reason for choosing the spring bed business as a livelihood. 2. Business development strategy by improving the quality of raw materials for spring bed products, developing product designs according to consumer desires, entrepreneurs employing experienced employees in the furniture sector. Providing a guarantee for spring bed products to gain loyalty from consumers. Spring bed buying and selling transactions using a door-to-door system carried out by sales. Spring bed buying and selling transactions via social media Facebook and Tiktok.

A mechanically-derived contact model for adhesive elastic-perfectly plastic particles, Part I: Utilizing the method of dimensionality reduction

In this two part series (Zunker and Kamrin, 2024), we present a contact model able to capture the response of interacting adhesive elastic-perfectly plastic particles under a variety of loadings. In Part I, we focus on elastic through fully-plastic contact with and without adhesion. For these contact regimes the model is built upon the method of dimensionality reduction which allows the problem of a 3D axisymmetric contact to be mapped to a corresponding problem of a 1D rigid indenter penetrating a bed of independent Hookean springs. Plasticity is accounted for by continuously varying the 1D indenter profile subject to a constraint on the contact pressure. Unloading falls out naturally, and simply requires lifting the 1D indenter out of the springs and tracking the force. By accounting for the incompressible nature of this plastic deformation, the contact model is able to capture multi-neighbor dependent effects such as increased force and formation of new contacts. JKR type adhesion is recovered seamlessly within the method of dimensionality reduction by simply allowing the springs to ‘stick’ to the 1D indenter’s surface. Because of the mechanics-focused formulation of the contact model, only a few physical inputs describing the interacting particles are needed: particle radius, Young’s modulus, Poisson ratio, yield stress, and effective surface energy. The contact model is validated against finite element simulations and analytic theory—including Hertz’s contact law and the JKR theory of adhesion. These comparisons show that the proposed contact model is able to accurately capture plastic displacement, average contact pressure, contact area, and force as a function of displacement for contacts as well as particle volume within the elastic to fully-plastic regimes.

Penerapan Algoritma Adaptive Response Rate Exponential Smoothing Terhadap Business Intelligence System

PT. XYZ is one of the companies in the field of furniture sales by offering its flagship product, namely spring bed. The company's business continues to grow every year, of course, the company must be able to complete its work quickly and precisely. One of the main problems of the company is that the increase in company sales is still not able to cover the company's expenses and sometimes the company still suffers losses. This happens because companies often make mistakes in purchasing product inventory stock. Not all types of spring beds sell well, so sometimes purchases are made of the type of spring bed that is not selling well, which results in stock accumulation and instability of the company's cash inflow and outflow. In this study, a Business Intelligence System was built, which is a form of information technology implementation to store, collect and analyze data into knowledge so that it can be used as prediction results. The prediction algorithm used in this research is the Adaptive Response Rate Exponential algorithm. The expected goal of this research is to build a Business Intelligence System that can calculate product sales predictions in the following month using the Adaptive Response Rate Exponential Smoothing (ARRES) algorithm. Based on the results of the MAPE test, it can be concluded that the percentage of prediction accuracy from the ARRES algorithm on the sales transaction data of PT. XYZ is 53.33% which is categorized as quite accurate and the percentage of prediction error from the ARRES method is 46.67% which is categorized as reasonable

Optimalisasi Keuntungan Menggunakan Metode Branch And Bound Pada Produksi Spring Bed

PT Satelit Maluku is a company that produces spring beds with three types, namely 2in1, ordinary spring beds and single beds. Every company established aims to get big profits as well as PT Satelit Maluku. To obtain large profits, companies need to make strategies so that each available material can be allocated optimally and appropriately. The purpose of this research is PT Satelit Maluku can optimize the profit of spring bed production by using the Branch and Bound and QM for Windows V5 methods. From the results of calculations using the Branch and Bound method and QM for windows V5, the optimal profit is Rp. 19,775,000 with a lot of production of spring bed type 2in1 is 0 (not producing), ordinary spring bed is 26 pieces and single bed is 3 pieces.

Tetrodotoxins (TTXs) and Vibrio alginolyticus in Mussels from Central Adriatic Sea (Italy): Are They Closely Related?

Tetrodotoxins (TTXs), potent neurotoxins, have become an increasing concern in Europe in recent decades, especially because of their presence in mollusks. The European Food Safety Authority published a Scientific Opinion setting a recommended threshold for TTX in mollusks of 44 µg equivalent kg−1 and calling all member states to contribute to an effort to gather data in order to produce a more exhaustive risk assessment. The objective of this work was to assess TTX levels in wild and farmed mussels (Mytilus galloprovincialis) harvested in 2018–2019 along the coastal area of the Marche region in the Central Adriatic Sea (Italy). The presence of Vibrio spp. carrying the non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) genes, which are suspected to be involved in TTX biosynthesis, was also investigated. Out of 158 mussel samples analyzed by hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry (HILIC-MS/MS), 11 (7%) contained the toxins at detectable levels (8–26 µg kg−1) and 3 (2%) contained levels above the EFSA safety threshold (61–76 µg kg−1). Contaminated mussels were all harvested from natural beds in spring or summer. Of the 2019 samples, 70% of them contained V. alginolyticus strains with the NRPS and/or PKS genes. None of the strains containing NRPS and/or PKS genes showed detectable levels of TTXs. TTXs in mussels are not yet a threat in the Marche region nor in Europe, but further investigations are surely needed.

The impact of mussel seed fishery on the dynamics of wild subtidal mussel beds in the western Wadden Sea, The Netherlands

For the cultivation of mussels, wild stocks of juveniles are harvested to collect mussel seed as starting material for the culture. These wild stocks are found in the sublittoral western Wadden Sea (NL). After summer spat fall, fisheries in Autumn on newly formed beds is carried out in areas that have the risk of washing away due to storms, or are vulnerable for starfish predation. These wild beds are considered as relatively unstable. On remaining more stable wild beds, seed fishery is carried out in next Spring. As the Wadden Sea is a nature conservation area, mussel seed fisheries is only allowed if no negative impacts on the nature management objectives can be expected. Seed fishery impacts were addressed in an extensive study including effects on sediment composition, macrobenthos and epifauna. In this paper we describe the effects of mussel seed fisheries on the development of the mussel stocks with and without fisheries in 39 pairwise studied impact and control plots.Stocks on seed beds in areas of the sublittoral Western Wadden Sea that are known as unstable, show a large decline within one year after settlement, also when there is no seed fishery. Harvesting seed on more stable beds in Spring results in a statistical significant reduction in stock size, which lasts for a period of two years after the first fishery. For the longer term, there is a gradual decline of the mussel stocks on all studied plots. On three out of the 39 plots, mussel biomass showed a large increase, both on control and impact parts. Also these mussel beds declined and eventually disappeared. A difference in life expectancy of fished and unfished beds was not demonstrated.It is concluded that sublittoral beds gradually disappear, also without fisheries. As a consequence, new recruitment is of critical importance for the long-term survival of sublittoral mussel beds. As we found no significant difference between recruitment on fished and control parts, there are no indications for negative impacts of seed fishery on new recruitment.

Analytical formulation and finite-element implementation technique of a rigorous two-parameter foundation model to beams on elastic foundations

ABSTRACT A simple way of computer implementation of an effective two-parameter subgrade model for the routine analysis of flexible foundations on an elastic subgrade is presented. It is based on a rigorous analytical subgrade model recently proposed by one of the authors that takes full account of the soil–structure interaction. The details of both finite element (FE) and analytical implementation of the model to beams are presented. Fully established closed-form relationships are provided for the subgrade parameters. The essence in the method is that the soil shear resistance within the loaded region is transferred to the foundation element as an additional rigidity in form of a geometric stiffness, thereby leaving the Winkler spring bed to take care of the vertical compression as accustomed. Additional edge springs are introduced to account for the edge forces due to the shear continuity extending beyond the edges. By so doing, the attractiveness of the long-enduring Winkler’s model is maintained, whereas the missing shear interaction is taken care of through the introduction of the geometric stiffness and the edge springs. The FE discretisation is thus limited to the foundation unit alone as initially intended. Subject classification codes: soil–foundation interaction

Application of ranked positional weights method in springbed production line balancing

In the current era of globalization, business competition demands industries in manufacturing to improve their business strategies are increasingly. The company that produces spring beds of various sizes has experienced rapid development. Spring bed 180 cm x 200 cm size has the longest process and research on the springbed production line is 180 cm x 200 cm. The company has 9 work stations with 19 work elements with time variation of work elements which are 50 seconds to 2737 seconds. The problem experienced by the company is the bottleneck at the assembly station because it has the longest cycle time of 2737 seconds. One method used in assembly line balancing is the RPW method (Ranked Positional Weights). The RPW method is an approach to solving problems in line balance and finding solutions quickly by the number of workstations determination at a minimum by giving weight to each work elements that has been placed on all work elements. Using the RPW method, obtained line efficiency, balance delay and smoothing index were 86.09%, 13.91% and 1418.45 with the number of work stations is 8.

An extended discrete element method for the estimation of contact pressure at the ankle joint during stance phase.

Abnormalities in the ankle contact pressure are related to the onset of osteoarthritis. In vivo measurements are not possible with currently available techniques, so computational methods such as the finite element analysis (FEA) are often used instead. The discrete element method (DEM), a computationally efficient alternative to time-consuming FEA, has also been used to predict the joint contact pressure. It describes the articular cartilage as a bed of independent springs, assuming a linearly elastic behaviour and absence of relative motion between the bones. In this study, we present the extended DEM (EDEM) which is able to track the motion of talus over time. The method was used, with input data from a subject-specific musculoskeletal model, to predict the contact pressure in the ankle joint during gait. Results from EDEM were also compared with outputs from conventional DEM. Predicted values of contact area were larger in EDEM than they were in DEM (4.67 and 4.18 cm2, respectively). Peak values of contact pressure, attained at the toe-off, were 7.3 MPa for EDEM and 6.92 MPa for DEM. Values predicted from EDEM fell well within the ranges reported in the literature. Overall, the motion of the talus had more effect on the extension and shape of the pressure distribution than it had on the magnitude of the pressure. The results indicated that EDEM is a valid methodology for the prediction of ankle contact pressure during daily activities.

MATERIAL REQUIREMENT PLANNING UNTUK MEMENUHI PRODUKSI PADA CV. BANGUN CIPTA ARTHA DI BADUNG

Inventory management without Material Requirement systems in CV. Bangun Cipta Artha resulted in the lot size for each order of raw materials not optimal. One concept that can be used to plan and control raw materials is the Material Requirement Planning. This study is to determine the number of sizes of raw material orders, the exact order time, the method that produces the lowest cost for each raw material, and the effect of using MRP on inventory costs. This research conducted on 160x200cm spring bed products. Data was analyzed by making production master schedules, determining net requirements, determining lot size, and making MRP tables. Based on the results, the determination the best lot sizing is the order quantiy period which results in a total inventory cost of Rp. 26,475,220 where the total cost is lower, compared to lot for lot method which Rp. 43,464,000. part period balancing Rp. 33,106,576, and conventional method Rp.49,472,912.
 Keywords: Material Requirement Planning (MRP), Sizing Lot, Lot For Lot, Balancing Part Period, Period Order Quantiy

Fostering biotechnology on the productivity and development of agricultural SMEs (Zimbabwe)

Purpose: This study scrutinizes the application of biotechnology in fostering the productivity of agricultural SMEs in Zimbabwe over the period 2019-2020. Fostering biotechnology around the world is significantly attracting much attention from agricultural entrepreneurs who have been lacking business productivity initiatives. As much this study attempts to unravel whether biotechnology is the spring bed for stimulating the productivity of agricultural SMEs to attain food security and nutriment. Research Methodology: A survey was used to get biotechnology data from archives of the National Biotechnology Association of Zimbabwe, concerning the use of biotechnology research in seeking to improve productivity by agricultural SMEs. Results: The study showed that fostering biotechnology has demonstrable benefits that help SMEs to grow and increase food nutriment. The study recommended that investing in biotechnology has returns which are most apparent for SMEs to increase productivity and competitiveness in Zimbabwe Limitation: The lack of a single study is a complex nature in the study and seemingly different instruments could produce a detailed analysis. Contribution: The study encourages fostering biotechnology to improve the productivity and development of agricultural SMEs in Zimbabwe to attain food security and nutriment and poverty reduction. Keywords: Biotechnology, Agriculture, SMEs, Development, Productivity, Food security

Design the Supply chain risk mitigation with supply chain risk management approach in spring bed factory

A risk is often described an event, a change in situation, or a consequence. It can be handled or eliminated by using risk management. The objective of the research was to identify some factors which caused the lateness in delivering raw materials until it comes on time at spring bed factory, a company which produces spring beds. Within these 2 years the company has had the problem of providing raw materials which are often delivered late so that the company cannot meet consumers’ demand punctually. In consequence it suffers financial loss. The research used HOR (HOR I and HOR II) by identifying risk event and risk agent. The result of the identification with HOR I risk agent, it was found that the lateness was caused by the lateness of ship arrival, the lateness in supplying raw materials, dependency on parent company. To mitigate risk agent, mitigating strategy (HOR II) was organized such as making work contract with suppliers that came from parent company in order to communicate directly with suppliers, procuring raw materials from 2 weeks to 2 months before they were needed, and doing multiple routes.

Influences of out-of-plane elastic energy and thermal effects on friction between graphene layers

Through molecular dynamic simulations, a system for investigating the contributions of elastic deformation energy and thermal activation effects to friction has been constructed. In this system, a graphene flake slides on a suspended graphene layer anchored on a bed of springs. The “graphene–spring” system provides a useful ideal approach to model different layers of graphene through changing the stiffness of the springs. The results first indicate that both the friction force and the elastic deformation energy have an exponential dependence on the support stiffness. Second, the observed non-monotonic variation in friction manifested by peaks and plateaus with increasing temperature results from the changing rate of energy dissipation due to the transition of slip regimes. Therefore, we suggest that the friction force emanates from the competition between the interfacial energy barrier and out-of-plane elastic deformation energy, as well as the competition between the thermal activation effects and transition of slip regimes. Therefore, the observation can extend the validity of the Prandtl–Tomlinson model on friction phenomena. Our simulations are intended to provide theoretical guidance when considering the influence of stiffness on the friction between graphene layers in the design of nanodevices.

Influence of stiffness gradient on friction between graphene layers

According to the molecular dynamics simulations and the mechanism of energy dissipation of nanofriction, we construct a model system with a flake sliding in commensurate configuration on a monolayer suspended graphene anchored on a bed of springs. The system is to analyze the contributions of different regions (T1-T7) of the graphene flake to friction force, with the substrate characterized by different stiffness gradients and midpoint stiffness.</br>The results indicate that the soft region of contact (T1) always contributes to the driving force, whereas the hard region (T7) leads to the biggest friction force on all column atoms of the flake. Moreover, as the support stiffness increases, when the stiffness gradient and the midpoint stiffness are equal to 1.34 nN/nm<sup>2</sup> and 12 nN/nm, respectively, the contribution ratio of T7 to the total friction increases from 33% to 47%, which is approximately 4-15 times greater than those of each column atoms in T3-T6. The results also indicate that the energy barrier decreases with the increase of support stiffness along the stiffness gradient direction of the substrate, which induces the resistance forces on the relative motion to decrease. Meanwhile, the amplitude of the thermal atomic fluctuation is higher in the softer region while lower in the harder one. This difference in amplitude leads to the considerable potential gradient that ultimately causes the driving force. Finally, for a given point at the end of the flake (T1 or T7), the intensity of the van der Waals potential field is mainly determined by the nearest substrate atoms at that point. Part of these nearest atoms lie inside the contact region while the others do not. Consequently, the thermal vibration of the atoms inside the contact region is different from that of the atoms outside the confinement. The different thermal vibrations induce the greater edge barriers. In addition, T1 lies in the soft edge region and T7 in the hard one. As a result, the normal deformations of these two regions are always different, and therefore they also generate the driving force.</br>At these points, the results reported here suggest that the friction force in each contact region is caused by the coupling of the energy barrier and the elastic deformation between the graphene surfaces. The former contribution, i.e.the energy barrier, includes the interfacial potential barrier in commensurate state which is against the sliding of the surfaces with respect to each other, and the potential gradient caused by the different vibration magnitudes of the substrate atoms against the different spring stiffness in the direction of stiffness gradient. The latter contribution, i.e. the elastic deformation, is the unbalanced edge energy barrier resulting from the asymmetrical deformation and the different degrees of freedom between the edge atoms of the slider and atoms inside and outside the contact area of the substrate. Results of this paper are expected to be able to provide theoretical guidance in considering the influence of stiffness gradient on friction between commensurate surfaces and in designing the nanodevices.

Establishing the Interlayer Structural Response for Unbonded Concrete Overlays of Existing Concrete Pavements

An improved mechanistic empirical design procedure for unbonded concrete overlays of existing concrete pavements (UBOLs) should account for the effect of the interlayer on the structural response of the pavement. One approach is to use the Totsky model to characterize the interlayer. The Totsky model treats the interlayer as a bed of springs between two plates and is currently incorporated into the rigid pavement finite element software ISLAB. A difficulty encountered in implementing this model is that there are currently no guidelines as to what the interlayer k-value should be for different types of interlayers. The interlayer can be constructed of new or aged asphalt (open or dense graded) or a nonwoven geotextile fabric. To establish the k-values that accurately characterize each of these materials, an ISLAB model of a laboratory test was created so the k-values could be established by matching the measured and calculated difference between the deflections in the overlay and existing pavement. To supplement the use of the laboratory data in establishing the Totsky interlayer k-value, an analysis was carried out using falling weight deflectometer (FWD) data from UBOLs at the Minnesota Road Research Facility (MnROAD). Analyses were then performed to determine if the difference between k-values for different interlayer materials are statistically significant, and if the results from the laboratory analysis match those obtained from the MnROAD field data. The Totsky k-value recommended for use when modeling the response of an UBOL with an asphalt interlayer is 3500 psi/in and 425 psi/in for a fabric interlayer.

Chaotic oscillations of viscoelastic microtubes conveying pulsatile fluid

As the first endeavour, the influence of a pulsatile flow on the large-amplitude bifurcation behaviour of viscoelastic microtubes subject to longitudinal pretention is studied with special consideration to chaos. The viscoelastic microtube is surrounded by a nonlinear spring bed. A modified size-dependent nonlinear tube model is developed based on a combination of the couple stress theory and the Euler–Bernoulli theory. Hamilton’s principle, as an equation derivation technique, and Galerkin’s procedure, as a discretisation technique, are used. Finally, the discretised differential equations of the pulsatile fluid-conveying viscoelastic microscale tube are solved using a time-integration approach. It is investigated that how the bifurcation response for both motions along the axial and transverse axes is highly dependent of the mean value and the amplitude of the speed of the pulsatile flow.

Study on the Fire Behavior of Spring Bed Mattress with and Without a Cooling Frame

Study on the Fire Behavior of Spring Bed Mattress with and Without a Cooling Frame

Punching-shear behaviors of RC-column footings with various reinforcement and strengthening details

In this study, various reinforcement and strengthening details for the improvement of the punching-shear behavior of concrete footings were developed. Eight test specimens of reinforced-concrete (RC) footings were constructed and tested to investigate the punching-shear behavior of the concrete footings with the developed details. The test parameters include the additional placement of a longitudinal reinforcement around the column-footing connections, the inclination of the shear reinforcement, an additional cast of high-strength concrete, and an additional concrete cast with amorphous metallic fibers (AMFs). The test specimens were supported on a bed of steel car springs that simulate the elastic behavior of soil. The test results show that the punching strength was significantly enhanced by the additional placement of the longitudinal reinforcement around the column-footing connections and by the addition of the retrofit materials (high-strength concrete and AMF-reinforced concrete). Contrarily, the shear reinforcement that was placed around the connections did not significantly affect the punching-shear strength of the footings. The test results were also compared with strength predictions for which the current design codes and the existing theoretical models were used.