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This article estimates the ties between green fiscal policies and energy efficiency in COVID-19 era. For this purpose, data envelopment analysis (DEA) approach is considered and applied. The study findings show that green fiscal policies, such as public supports and tax rebates, have significant role in reducing energy poverty of different international countries by advancing energy efficiency. Therefore, a panel data ranging from 2010 to 2020 is used. Our findings indicate that the aggregate degree of green fiscal policies help to decline energy poverty. Renewable energy companies had larger series of net fiscal competence and size efficiency, and their levels of energy efficiency were greater than 0.457%, with the 16% effect of current public supports and 11% effect of taxation rebates supported to diminish energy poverty with 29.7% in different international economies. This is a positive effect by green fiscal policies. The study also presented policy implications suggesting effectively implementing green fiscal policies for more efficient carbon reduction and making climate change supportive for peoples in post COVID-19 period.

This study measures the energy rebound effects of Chinese energy and coal power use in Chinese energy-intensive industries by using latent class stochastic frontier models like LMDI, and other various econometric estimation approach for coal-supplying regions in China ranging between 1992 and 2018. The findings reveals that China’s coal sector’s average capacity consumption is 0.81%, with a pattern of first increasing and then decreasing, falling to 0.68% in 2016 specifically. The coal capacity operation rate concerning low as well as depleted regions is generally strong, with limited space for expansion. In 2015 and 2016, the utilization rate of coal production potential in moderate-producing areas fell about 42%. Economic development variables affect the capacity utilization levels of moderate, weak, and depleted generating regions. At the same time, the price volatility cannot induce a practical improvement in the ability utilization rate, which means that China’s coal industry is mainly un-marketized. China’s energy efficiency increased about 19.98% among 2000 and 2016, while the rapidest expansion pattern has been noted in the eastern province at 39.86%, next to central (11.71%) and western regions (9.59%). The take back impact via the renewable energy and renewable productivity channels is estimated as 12.34% and 25.40%, respectively. Therefore, the take back impact is of significant importance regarding energy preservation, as China’s cumulative renewable energy use is equal to China’s aggregate energy use. On such findings, recent research also contributed by presenting novel policy implications for key stakeholders.

Ghana suffers from inadequate power supply due to increasing demand though it is amongst the African nations with the highest access to electricity. This research aims to assess the techno-economic potential of wind and solar energy potential for Ghana's northern part. We employ the Weibull distribution function, levelized cost of energy, and net present cost metrics for the economic study. The wind and solar energy resource's structure generated 72,284 kWh yearly. Both systems were identified to be too expensive if implemented under the current financing conditions in the country. The PV systems generated 38,859 kWh/year, representing 53.76% of the total electricity generated in a year, generating renewable hydrogen in the country. The findings show that sizing and management of renewable plants will fulfill the basic annual cooking demands of the populations, which are 785 kg H2 in Ghana. The countries' capacity for developing solar hydrogen plants is further suggested by generating new solar hydrogen opportunity charts. Considering the significance of hydrogen energy under the renewable energy output, we recommend using hybrid systems for hydrogen production. The findings reveal which flexibility options are critical in key stages of the energy transition to a 70, 80, 90, and 100% renewable energy system.

This research aims to look into the effect of COVID-19 on emerging stock markets in seven of the Association of Southeast Asian Nations' (ASEAN-7) member countries from March 21, 2020 to April 31, 2020. This paper uses a ST-HAR-type Bayesian posterior model and it highlights the stock market of this ongoing crisis, such as, COVID-19 outbreak in all countries and related industries. The empirical results shown a clear evidence of a transition during COVID-19 crisis regime, also crisis intensity and timing differences. The most negatively impacted industries were health care and consumer services due to the Covid-19 drug-race and international travel restrictions. More so, study results estimated that only a small number of sectors are affected by COVID-19 fear including health care, consumer services, utilities, and technology, significance at the 1%, 5%, and 10%, that measure current volatility's reliance on weekly and monthly variables. Secondly, it is found that there is almost no chance that the COVID-19 pandemic would positively affect the stock market performance in all the countries, mainly Indonesia and Singapore were the countries most affected. Thirdly, results shown that Thailand's stock market output has dropped by 15%. Results shows that COVID-19 fear causes an eventual reason of public attention towards stock market volatility. The study presented comprehensive way forwards to stabilize movement of ASEAN equity market's volatility index and guided the policy implications to key stakeholders that can better help to mitigate drastic impacts of COVID-19 fear on the performance of equity markets.

Due to their different abilities to improve financial growth and improve social development, small and medium enterprises (SMEs) have been referred to as the economy's backbone. Small- and medium-sized enterprises are crucial for both high- and low-income nations' financial development. Customers grow more conscious of their purchase choices, preferences, and environmental consequences. The financial opportunities for SMEs in the United Arab Emirates to use green innovation methods to address potential obstacles for increasing green goods, processes, and management are examined in this paper; as a result, it is critical to reduce clean technology adoption constraints in small- and medium-sized businesses. To identify significant hurdles, sub-barriers, and ways to overcome impediments to green innovation in the United Arab Emirates, we apply an integrated decision process. Following a detailed literature analysis and the assistance of twelve experts, six primary obstacles, twenty-five sub-obstacles, and strategies to reduce the barriers were identified. Primary and sub-barriers were assessed using the FAHP. The (FTOPSIS) approach was used to rank the strategies. Five SMEs in the United Arab Emirates are putting the suggested integrated decision model to the test. "Financial investment levels 0.646 to 11 percent growth level," according to the FAHP, are the most significant hurdles to SMEs adopting green practices. This research demonstrated a considerable beneficial association between SMEs and financial development and funding in the United Arab Emirates. According to this study, using research methodologies to provide green innovation in SMEs is the best strategy to overcome green innovation and adoption hurdles in small and medium firms and increasing their economics.

This research measures the relationship between green innovation and the performance of financial development by using an econometric estimation during the year of 2000 to 2018 in 28 Chinese provinces. It is intended to explore the relative role of green technological innovation in driving green financial development in the west and central China, as well as how it influences economic growth in these regions. Ordinary least square (OLS) framework was utilized in mainland China to perform empirical studies by using an econometric estimation. This study claims that China has adopted research-based education system, while those for economic growth and expenditure in the regions while the innovation parts results shows that the tertiary education were 12.42% and 13.53% versus the 10.50% and 10.6% in the eastern area. The research-based education increases the patents in green innovation and boosts the environmental policy. The financial development led to green technological development and innovation. Green innovation and financial development decrease the emissions, and it is apparent that as environmental regulations stimulate technical development, the superiority of human resources increases. The findings indicate that green financing reduces short-term lending, thus limiting clean energy overinvestment, while the long-term loans have little impact on renewable energy overinvestment, and the intermediary effect is unmaintainable. Meanwhile, the green financial growth will reduce renewable energy overinvestment and increase renewable energy investment productivity to certain amount.

Since 1970, numerous governments have established strategic petroleum reserves (SPRs) in relation to oil supply interruptions. In this study, important oil reserves, physical oil supply disruption and social welfare losses due to physical distribution of oil supply have been measured. The physical oil supply disruption has been measured in the form of oil supply vulnerability index and oil volatility index of the South Asian economies. Analysis reveals that the accumulation and drawdown of important national crude oil strategic petroleum reserves where the state wants to optimize individual social welfare while individuals hold over stock optimize their earnings levels. The monetary deciding factors utilize the government’s optimum important stockpile policy and simultaneously the amount and economic factors vital for the nongovernment market to actuate the optimum accumulation and nonaccumulation of important fossil fuels stockpile. Additionally, findings show that India is the lowest crude oil insecure country while Afghanistan and Bangladesh are the highest insecure countries in terms of oil supply. India’s topmost mark shows a bigger possibility to alter the fossil fuels producers while Afghanistan, Bangladesh, Bhutan and Nepal have the minimum mark corroborating the group as the utmost producer risk exposed nations.

In the contemporary environment, developing countries are more focused on how economic factors can reasonably utilize technological advancement and carbon neutrality target as effective mechanisms in achieving sustainable production and consumption patterns. The effort to attain carbon neutrality target on natural environment in terms of lower carbon emission (CO2), haze pollution, and greenhouse gas (GHG) requires measures like the usage of non-renewable energy, ecological innovation, and environmental taxes. In doing so, this study considers the sustainability of China's natural environment in terms of CO2 emission, haze pollution through PM2.5, and greenhouse gas emission as well as factors like ecological innovation (ECO), environmental taxes (ERT), renewable energy, and globalization as the key determinants. The Quantile ARDL approach was used to examine both long- and short-run relationships between the explanatory and outcome variables. The results confirmed that there is a significant and negative impact of ECO, renewable energy, and ERT on CO2 emission in the region of China under different quantiles. Whereas, the globalization factor was observed as positively and significantly linked with CO2 emission but only for the higher quantiles. The long-run estimation further showed that ECO, renewable energy, and ERT can significantly help to decrease haze pollution in terms of PM2.5 in China. Furthermore, QARDL also confirms the negative and long-run estimation between the ECO, REN, and ERT, whereas globalization is causing more GHG in China, subsequently creating more environmental sustainability issues. Thus, it is concluded that effective innovation, renewable energy consumption, and environmental taxes reduce carbon emission while globalization increases the carbon emission in the country.

In the past decade, researchers have shifted their interests to explore different ways to mitigate environmental degradation. In that context, the present study explores the role of solar energy and eco-innovation in reducing environmental degradation in China. The study utilized data for the period 1990-2018 and applied the latest available econometric technique, a quantile autoregressive distributed lag model, to determine the impacts of solar energy and eco-innovation on improving China's environmental quality. According to the empirical results, in the long term, solar energy is negatively and significantly associated with CO2 emissions at higher quantiles. Eco-innovation has proven to be the most important channel to mitigate CO2 emissions in China. Eco-innovation is exerting a negative and significant influence on CO2 emissions at all quantiles in the long term. In addition, the population size is causing CO2 emissions to surge significantly at lower quantiles. The empirical analysis reveals that per capita income (PI) is positively associated with CO2 emissions at all quantiles, but it is significant only at higher quantiles in China. We found evidence of unidirectional causality for eco-innovation to CO2 emissions and solar energy to CO2 emissions. However, for population and CO2 emissions, per capita income, and CO2 emissions, we found bidirectional causality. As indicated by our empirical results, solar energy and eco-innovation are the two most effective channels to control CO2 emissions in China. Therefore, policies based on the promotion of eco-innovation and the initiation of new solar energy projects can control emissions and improve environmental quality in China. Integr Environ Assess Manag 2021;00:1-17. © 2021 SETAC.

Plate or nail fixations have been applied to the repair of clavicle fractures. However, it is quite difficult to fairly evaluate the different clavicle fixation techniques owing to variations in the bone anatomy, bone quality, and fracture pattern. The purpose of this study was to investigate the biomechanical performances of different fixation techniques applied to a clavicle fracture using the finite element method. A simplified single-clavicle model and a complete human upper-body skeleton model were developed in this study. Three types of plate fixations, namely, superior clavicle plate, anterior clavicle plate, and clavicle anatomic spiral fixations, and one nail fixation, a titanium elastic nail fixation, were investigated and compared. The plate fixation techniques have a better fixation stability compared to the nail fixation technique. However, the nail fixation technique shows lower bone stress and can reduce the risk of a peri-implant fracture compared to the plate fixation techniques. Increasing the number of locking screws for the clavicle plate system can reduce the implant stress. Insertion of the bone plate into the anterior site of the clavicle or a multi-plane fixation is recommended to achieve the required biomechanical performance. A plate fixation revealed a relatively better fixation stability, and a nail fixation showed a lower risk of a peri-implant fracture.

Evaluations are vital to quantify the functionalities of athletic footwear, such as the performance of slip resistance, shock absorption, and rebound. Computational technology has progressed to become a promising solution for accelerating product development time and providing customized products in order to keep up with the competitive contemporary footwear market. In this research, the effects of various tread pattern designs on traction performance in a normal gait were analyzed by employing an approach that integrated computational simulation and gait analysis. A state-of-the-art finite element (FE) model of a shoe was developed by digital sculpting technology. A dynamic plantar pressure distribution was automatically applied to interpret individualized subject conditions. The traction performance and real contact area between the shoe and the ground during the gait could be characterized and predicted. The results suggest that the real contact area and the structure of the outsole tread design influence the traction performance of the shoe in dry conditions. This computational process is more efficient than mechanical tests in terms of both cost and time, and it could bring a noticeable benefit to the footwear industry in the early design phases of product development.

Experimental approaches have been widely used to investigate the bone–implant interfacial strength of anterior lumbar interbody fusion (ALIF) devices. However, improper design of experimental jigs and inconsistencies in cadaveric specimens might significantly impede the evaluation of different ALIF device designs. Therefore, this study aimed to investigate and compare various test setups in terms of their feasibility for conducting pullout tests on ALIF devices. Three types of pullout test setups for evaluating the interfacial strength of the ALIF devices were investigated. Then, finite element models of the L4–L5 segment with different ALIF device designs were developed and numerical analysis was performed. Finally, the results from all the pullout test setups were compared with those obtained from numerical analysis. The results indicated that the quasi-material and boundary pullout test setup (QMBPTS), which considered the effects of the composite material of the test specimens and mimicked the lumbar posterior element’s anatomy and loading mechanism, revealed a more realistic bone failure pattern and interfacial pullout strength compared with the general pullout test setup and the quasi-boundary pullout test setup. The finite element models could accurately predict the experimental results obtained using the QMBPTS. It was confirmed that QMBPTS is a feasible and inexpensive pullout test setup for evaluating the bone–implant interfacial pullout strength of ALIF devices. Both the experimental and numerical approaches could provide useful information for designing a biomechanical experiment to solve bone–implant loosening problems.

Objective Numerous studies have demonstrated that fluvoxamine has considerable pharmacokinetic and pharmacodynamic interactions with clozapine. We conducted a 12-week, randomized, double-blind, placebo-controlled study to evaluate the effects of fluvoxamine on metabolic parameters and psychopathology in clozapine-treated patients with schizophrenia. Methods We recruited 85 patients who received a DSM-IV diagnosis of schizophrenia. Eligible patients were randomized to receive fluvoxamine 50 mg/day plus clozapine 100 mg/day or clozapine 300 mg/day. We studied metabolic parameters, psychopathology, and drug levels at baseline and 4, 8, and 12 weeks after the intervention. Plasma levels of clozapine, norclozapine, clozapine N-oxide, and fluvoxamine were determined using high-performance liquid chromatography with ultraviolet detection. Results No significant difference was observed in baseline characteristics between the two groups. Clozapine–fluvoxamine combined treatment significantly attenuated the increments in body weight, insulin resistance, and levels of insulin, glucose, and triglycerides compared with clozapine monotherapy. Both groups exhibited significant improvements in their Positive and Negative Syndrome Scale (PANSS) total and negative scores. The combined treatment group showed significant reduction in the PANSS general psychopathology scores compared with the monotherapy group. No difference was observed in the plasma clozapine level between the two groups. The monotherapy group showed higher levels of norclozapine and clozapine N-oxide than the combined group. Conclusions Compared with clozapine monotherapy, treatment with adjunctive fluvoxamine with clozapine for 12 weeks can alleviate body weight gain and metabolic abnormalities in patients with schizophrenia, without sacrificing the clinical effect. Clinicians should interpret these findings cautiously considering the short duration of this study. The study was registered at www.clinicaltrials.gov ( NCT01401491 ).

Cage loosening continues to be a problem after spinal fusion surgery. Past studies have investigated the interfacial strength of cages in situations of a single loosening direction. However, the human spine can move in different directions; therefore, cage loosening may occur in any direction. The purposes of this study were to develop a novel finite element analysis-based neurogenetic algorithm and to discover the spike design of vertebral body cages (VBCs) with excellent interfacial pullout strength by considering multiple cage loosening directions. Five design variables of VBCs were defined, and three-dimensional finite element models were created to predict the interfacial pullout strength of different VBCs. Then, both the artificial neural network and the genetic algorithm were applied to discover the optimum VBC. Finally, one optimum VBC and five VBCs selected from the Taguchi orthogonal array were tested and compared. The optimum spike design of the VBCs was successfully determined, and the interfacial pullout strength of the optimum VBC design was superior to that of other VBCs (17–77% increase in maximum pullout force). Non-oblique spikes were suggested to enhance their loosening resistances when multiple loosening directions were considered. In conclusion, the optimum spike design revealed excellent interfacial pullout performance of vertebral body cages in multiple loosening directions. The outcome of this study could help surgeons understand the interfacial pullout strength of VBCs in terms of their spike designs, and it could provide design direction to biomechanical engineers.

A high number of slip-and-fall incidents result in common injuries of daily life. The design of outsole tread pattern is one of the key factors which had a direct impact on slip resistance performance. The application of numerical simulation is an opportunity for footwear industry to evaluate the multiple outsole tread pattern design and ground condition in a more controlled and efficient manner than mechanical testing in the developing process.

We investigate whether the funding liquidity risk to institutional investors influences the negative relation between expected returns and variance (the ‘‘Low-volatility anomaly’’). With the Taiwan stock market as a setting, we implement a multivariate Markov switching model and use the funding liquidity risk to model the time-varying transition probabilities of the regime-switching process to capture changes in the funding liquidity risk regime. Our evidence documents that the low-volatility anomaly is most pronounced when there is high funding liquidity risk. When there is low funding liquidity risk, however, the low-volatility anomaly has a significant reversal. These results imply that the increased funding liquidity risk due to financial shock transmitted from parent banks is associated with higher selling pressure on institutional investors’ high-volatility stocks, leading to the low-volatility anomaly.

Porous additive manufactured (AM) cages were a new selection for posterior lumbar interbody fusion (PLIF) surgery due to their low rigidity. Past studies had investigated porous AM cages; however, their structural designs and performances were evaluated using oversimplified numerical models. Thus, the purpose of this research was to investigate the porous structure of the AM cages using a realistic spine model. Three-dimensional finite element models of T10-S1 multilevel spine were developed using ANSYS Workbench. Eleven types of the AM cages were analyzed and compared to understand their strengths and limitations. The results showed that the sparse density in microstructure geometry would increase the intersegmental rotation but the von Mises stress of cage becomes enlarge simultaneously. Adding a PEEK layer to the microstructure is not a good choice to prevent the cage stress getting higher value. The outcomes of this study can help surgeons to understand the biomechanics of PLIF surgery combined with the use of porous AM cages.

Rib fracture is a common injury and can result in pain during respiration. Conservative treatment of rib fracture is applied via mechanical ventilation. However, ventilator-associated complications frequently occur. Surgical fixation is another approach to treat rib fractures. Unfortunately, this surgical treatment is still not completely defined. Past studies have evaluated the biomechanics of the rib cage during respiration using a finite element method, but only intact conditions were modelled. Thus, the purpose of this study was to develop a realistic numerical model of the human rib cage and to analyse the biomechanical performance of intact, injured and treated rib cages. Three-dimensional finite element models of the human rib cage were developed. Respiratory movement of the human rib cage was simulated to evaluate the strengths and limitations of different scenarios. The results show that a realistic human respiratory movement can be simulated and the predicted results were closely related to previous study (correlation coefficient>0.92). Fixation of two fractured ribs significantly decreased the fixation index (191%) compared to the injured model. This fixation may provide adequate fixation stability as well as reveal lower bone stress and implant stress compared with the fixation of three or more fractured ribs.

The pelvis is one of the most stressed areas of the human musculoskeletal system due to the transfer of truncal loads to the lower extremities. Sacroiliac joint injury may lead to abnormal joint mechanics and an unstable pelvis. Various fixation techniques have been evaluated and discussed. However, it may be difficult to investigate each technique due to variations in bone quality, bone anatomy, fracture pattern, and fixation location. Additionally, the finite element method is one useful technology that avoids these variations. Unfortunately, most previous studies neglected the effects of the lumbar spine and femurs when they investigated the biomechanics of pelvises. Thus, the aim of this study was to investigate the biomechanical performance of intact, injured, and treated pelvises using numerical and experimental approaches. Three-dimensional finite element models of the spine-pelvis-femur complex with and without muscles and ligaments were developed. The intact pelvis, the pelvis with sacroiliac joint injury, and three types of pelvic fixation techniques were analyzed. Concurrently, biomechanical tests were conducted to validate the numerical outcomes using artificial pelvises. Posterior iliosacral screw fixation showed relatively better fixation stability and lower risks of implant failure and pelvic breakage than sacral bar fixation and a locking compression plate fixation. The present study can help surgeons and engineers understand the biomechanics of intact, injured, and treated pelvises. Both the simulation technique and the experimental setup can be applied to investigate different pelvic injuries.

Total ankle replacement (TAR) surgery is one of the useful methods to treat ankle arthritis. Selective laser melting that is an additive manufacturing (AM) technique has made it possible to fabricate orthopedic implants. However, there are rare studies to analyze AM implants using finite element method. Thus, the purpose of this study was to investigate the effect of the various porous designs with three types of tibial shapes for five ankle postures using three-dimensional (3D) human lower extremity models. The variable-axis-mobile-bearing (VAMB) TAR models were developed in one solid TAR design and three porous TAR designs on the tibial and talar components. Additionally, three shape designs (curved, flat, and tilted) of the tibial component were also evaluated. Each TAR design was assembled on the human lower extremity model with standing, inversion, eversion, plantar flexion, and dorsiflexion ankle postures. The results showed that there was a minor effect among the solid and porous TAR designs on the implant stability, the bone stress, and the implant stress. However, those performances in the plantar flexion were significantly reduced compared to that in the other ankle postures. Although the porous TAR designs have a higher risk of implant failure and bone breakage, it may have better bone-implant bonding ability. This study could help engineers and surgeons to understand the design rationale and biomechanics of AM-based TAR devices.

Locking compression plates (LCPs) have been used to fix femoral shaft fractures. Previous studies have attempted to identify the best LCP screw positions and numbers to achieve the fixation stability. However, the determined screw positions and numbers were mainly based on the surgeons' experiences. The aim of this study was to discover the best number and positions of LCP screws to achieve acceptable fixation stability. Three-dimensional numerical models of a fractured femur with the LCP were first developed. Then, the best screw position and number of LCPs were determined by using a simulation-based particle swarm optimization algorithm. Finally, the results of the numerical study were validated by conducting biomechanical tests. The results showed that the LCP with six locking screws resulted in the necessary fixation stability, and the best combination of positions of locking screws inserted into the LCP was 1-5-6-7-8-12 (three locking screws on either side of the bone fragment with two locking screws as close as practicable to the fracture site). In addition, the numerical models and algorithms developed in this study were validated by the biomechanical tests. Both the numerical and experimental results can provide clinical suggestions to surgeons and help them to understand the biomechanics of LCP systems.

Subsidence of interbody devices into the vertebral body might result in serious clinical problems, especially when the devices are not well designed and analyzed. Recently, some novel designs were proposed to reduce the risk of subsidence, but those designs are based on the researcher's experience. The purpose of this study was to discover the interbody device design with excellent subsidence resistance by changing the device's shape. The three-dimensional nonlinear finite element models, which consisted of the interbody device and vertebral body, were created first. Then, the simulation-based genetic algorithm, which combined the finite element model and the searching algorithm, was developed by using ANSYS® Parametric Design Language. Finally, the numerical results were carefully validated with the use of biomechanical tests. The optimum shape design obtained in this study looks like a flower with many petals and it has excellent subsidence resistance when compared with the other designs provided by the past studies. The results of the present study could help surgeons to understand the subsidence resistance of interbody devices in terms of their shapes and has directly provided the design rationales to engineers. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1158–1163, 2013

Locked compression plates have been widely used for the treatment of diaphyseal femoral fractures. The purpose of this study was to discover the best screw configurations in the twelve-hole bone plate by using a biomechanical optimization method namely finite element analysis-based discrete particle swarm optimization. The results showed that increasing the number of screws decreased the deflection of the constructs, and the performance of three screws per main segment showed no significant difference as compared to all screws occupying the plate holes. We concluded that stability can be achieved by increasing the number of screws and three screws on either of the segment can provide sufficient stability while minimizing the complications of plate fixation.

Geographic forwarding is part of geographic routing in that each node only needs to know the location of its neighbors and the destination. This method can reduce the cost of table-driven routing which needs to maintain the whole path, even if the path is not in use. It also saves time when searching the path, as compared with reactive routing. When using geographic forwarding, it usually happens that the local maximum cannot forward the packet directly to the destination; this fundamental problem is called Dead End. We use the A star (A*) algorithm, which is usually used in role-playing or strategic games, to detour around terrain that cannot be passed through directly. Nodes must vote on an agent in a specific area to be a decision-maker and find a reference route for the source node. When the route is decided, geographic forwarding is used according to this reference path to the destination to avoid the dead end.

Anterior Lumbar Interbody Fusion (ALIF) has been widely used to treat internal disc degeneration. However, different cage positions and their orientations may affect the initial stability leading to different fusion results. The purpose of the present study is to investigate the optimum cage position and orientation for aiding an ALIF having a transfacet pedicle screw fixation (TFPS). A three-dimensional finite element model (ALIF with TFPS) has been developed to simulate the stability of the L4/L5 fusion segment under five different loading conditions. The Taguchi method was used to evaluate the optimized placement of the cages. Three control factors and two noise factors were included in the parameter design. The control factors included the anterior-posterior position, the medio-lateral position, and the convergent-divergent angle between the two cages. The compressive preload and the strengths of the cancellous bone were set as noise factors. From the results of the FEA and the Taguchi method, we suggest that the optimal cage positioning has a wide anterior placement, and a diverging angle between the two cages. The results show that the optimum cage position simultaneously contributes to a stronger support of the anterior column and lowers the risk of TFPS loosening.

A titanium mesh cage (TMC) might develop subsidence and cause local kyphotic deformity of the spine. For prevention of this complication, this study was designed to find the most appropriate spike design for a vertebral body cage (VBC). In order to investigate the subsidence of a VBC, three‐dimensional finite element models of the L5 spinal model with a nonlinear contact analysis have been developed. Then, the Taguchi robust design method was used to evaluate spike designs. Finally, the mechanical experiment was developed to obtain the compressive strength of the VBC. For the results of the FEM‐based Taguchi method, the spike row, the spike obliquity, and the spike height were especially important factors for preventing the subsidence. The optimum combinations were pyramidal spike type, a spike height of 2 mm, a spike diameter of 1.4 mm, an oblique geometry, 11 rows per 28 mm, and an inner diameter of 10 mm. For the results of the experiment, the good relationship between finite element simulatio...

Study Design: Comparative in vitro biomechanical study and finite element analysis. Objectives: To investigate the bending strength and pullout strength of conical pedicle screws, as compared with conventional cylindrical screws. Summary of Background Data: Transpedicle screw fixation, the gold standard of spinal fixation, is threatened by screw failure. Conical screws can resist screw breakage and loosening. However, biomechanical studies of bending strength have been lacking, and the results of pullout studies have varied widely. Methods: Ten types of pedicle screws with different patterns of core tapering and core diameter were specially manufactured with good control of all other design factors. The stiffness, yielding strength, and fatigue life of the pedicle screws were assessed by cantilever bending tests using high-molecular-weight polyethylene. The pullout strength was assessed by pullout tests using polyurethane foam. Concurrently, 3-dimensional finite element models simulating these mechanical tests were created, and the results were correlated to those of the mechanical tests. Results: In bending tests, conical screws had substantially higher stiffness, yielding strength, and fatigue life than cylindrical screws (P

Background Healing of tibial fractures treated by locked nailing is threatened by locking screw failure. However, the effects of the design factors of the screws on their mechanical strength have rarely been studied. Method Three-point bending tests and finite element analyses were used to investigate the bending strength of five types of commercially available tibial locking screws and two types of specially designed screws. Yielding strength and fatigue life measured in bending tests were correlated to total strain energy and maximal tensile stress computed in finite element analyses. Parametric analysis and design optimization were done according to the Taguchi method. Validation studies to assess the stress rising effect of the threads on the fatigue strength were conducted in two types of new screws made of either stainless steel or titanium alloy. Findings The yielding strength of the screws was closely related to their total strain energy, and the logarithm of the fatigue life was closely related to the maximal tensile stress with correlation coefficients of −0.95 and −0.90, respectively. Parametric studies indicated that fatigue strength of the screws was affected mainly by inner diameter (contribution, 63.8%) and root radius (27.8%). The yielding strength was determined primarily by inner diameter (88.5%). Titanium screws had a longer fatigue life than stainless steel screws, especially in screws with larger root radii. Interpretation A screw’s strength is closely related to its design factors. Finite element models, which can reliably reflect the mechanical strength of screws can save time and effort during screw design. Larger root radius can effectively improve the fatigue strength, especially for titanium screws as compared with stainless steel screws.

In this paper, we propose a new novel polling-based medium access control protocol, named UPCF (Unified Point Coordination Function), to provide power conservation and quality-of-service (QoS) guarantees for multimedia applications over wireless local area networks. Specifically, UPCF has the following attractive features. First, it supports multiple priority levels and guarantees that high-priority stations always join the polling list earlier than low-priority stations. Second, it provides fast reservation scheme such that associated stations with real-time traffic can get on the polling list in bounded time. Third, it employs dynamic channel time allocation scheme to support CBR/VBR transportation and provide per-flow probabilistic bandwidth assurance. Fourth, it employs the power management techniques to let mobile stations save as much energy as possible. Fifth, it adopts the mobile-assisted admission control technique such that the point coordinator can admit as many newly flows as possible while not violating QoS guarantees made to already-admitted flows. The performance of UPCF is evaluated through both analysis and simulations. Simulation results do confirm that, as compared with the PCF in IEEE 802.11, UPCF not only provides higher goodput and energy throughput, but also achieves lower power consumption and frame loss due to delay expiry. Last but not least, we expect that UPCF can pass the current Wi-Fi certification and may coexist with the upcoming IEEE 802.11e standard.

An ad hoc network is formed by a group of mobile hosts communicating over wireless channels. There is no any fixed network interaction and centralized administration. Because a routing protocol needs an efficient medium access control (MAC) protocol to support, to design an efficient MAC protocol is important and fundamental in ad hoc networks. So far, no other MAC protocol has stable broadcast performance in the dense mobile ad hoc network. In this paper, we address the issue of reliable broadcast and stable performance at the MAC layer. We present a reliable and adaptive broadcast MAC protocol RAMAC which is a TDMA-based distributed MAC protocol for the broadcast reservation in mobile ad hoc networks. We divide the area into many grid cells with the support of GPS. We use the properties of grid cells to design an efficient protocol. RAMAC is characterized by five important features: (i) A dynamic frame size is generated in every contention. This dynamic frame size can let RAMAC adapt to the network load. (ii) Our well-designed reservation protocol can avoid the deadlock problem. (iii) When the network is dense, RAMAC can still work stably; however, no other MAC protocols can work well in the dense network. (iv) We propose a reservation protocol that can efficiently and fast reserve data slots. (v) The well-designed grid architecture makes the senders of unicast in a grid cell transmit concurrently as many as possible, so RAMAC is highly parallel in unicast.

The Universal Mobile Telecommunications System (UMTS) adopts the WCDMA technology as the radio access interface to provide variable transmission rate services. There are four classes of connections identified in UMTS, which are the conversational, streaming, interactive, and background connections. To efficiently utilize radio bandwidth, the shared channel approach is proposed to deliver the packets for the interactive and background connections. This paper proposes a "Shared-Channel Assignment and Scheduling" (SCAS) algorithm to periodically allocate shared channels to serve interactive and background connections. We conduct formal mathematical proofs and simulation experiments to investigate the performance of the SCAS algorithm. We formally prove that with SCAS, a shared channel can be fully utilized (i.e., the utilization of a shared channel can be up to 100%) to serve the interactive connections. Our analysis indicates that compared with the previously proposed shared channel allocation and scheduling algorithms, there are less computation and communication overheads introduced in the SCAS algorithm. The results of the simulation experiments indicate that it is preferred to set up the Transmission Time Interval (TTI; that is, the unit of time interval for shared channel allocation) smaller to optimize the performance of the SCAS algorithm, including the shared channel utilization and the average waiting time of a connection before getting transmission service.

The Universal Mobile Telecommunications System (UMTS) provides users variable data rate services, which adopts wide-band code-division multiple-access (WCDMA) as the radio access technology. In WCDMA, orthogonal variable spreading factor (OVSF) codes are assigned to different users to preserve the orthogonality between users' physical channels. The data rate supported by an OVSF code depends on its spreading factor (SF). An OVSF code with smaller SF can support higher data rate services than that with larger SFs. Randomly assigning the OVSF code with a large SF to a user may preclude a larger number of OVSF codes with small SFs, which may cause lots of high data rate call requests to be blocked. Therefore the OVSF code assignment affects the performance of the UMTS network significantly. In this paper, we propose two OVSF code assignment schemes CADPB1 and CADPB2 for UMTS. Both schemes are simple and with low system overhead. The simulation experiments are conducted to evaluate the performances for our schemes. Our study indicates that our proposed schemes outperform previously proposed schemes in terms of the weighted blocking probability and fairness index. Our schemes improve the call acceptance rate by slightly introducing call waiting time.

Objective. To investigate the bone holding power of tibial locking screws. Design. The bone holding power was assessed by mechanical testing and finite element analysis. Background. Screw loosening might threaten fracture fixation and bone healing. Methods. In mechanical tests, six types of different tibial locking screws were inserted into low-density polyurethane foam tubes, which simulated osteoporotic bone. The screws were pushed out of the foam bone by an axial load, and the maximal pushout load was recorded. In finite element analysis, three-dimensional finite element models with a nonlinear contact interface between the screws and the bones were created to simulate the mechanical testing. The total strain energy of the bone and total reaction force of the screws were recorded. The contribution of the design factors was analyzed by the Taguchi method. Results. In the mechanical tests, foam bone was stripped by the screw threads without screw deformation. The testing results were closely related to those of finite element analysis. The Taguchi analysis showed that the descending order of contribution of the design factors was outer diameter, pitch, half angle, and inner diameter. Root radius and thread width had minimal effects. Conclusions. The bone holding power of the screws could be reliably assessed by finite element models, which could analyze the effects of all the design factors independently and were potentially applicable to screws with irregular thread patterns. RelevanceThe finite element models built in this study may help manufacturers in evaluating new designs of locking screws and assist surgeons in selecting suitable devices for patients with severe osteoporosis.

This study investigated the bone holding power of tibial locking screws by mechanical testing and finite element analysis. In mechanical tests, five types of commercially available tibial locking screws: Howmedica, Osteo AG, Richards type I, Richards type II, and Synthes were inserted in a cylinder of polyurethane foam bone. Axial load was applied to the screw tip to push the screws out of the foam bone by a material testing machine. The pushout strength of each screw was recorded. In finite element analysis, three-dimensional finite element models with nonlinear contact interface between the screws and the bones were created to simulate the mechanical testing. The results showed that the order of the pushout strength of the locking screws from high to low was Osteo AG, Richards type II, Richards type I, Howmedica, and Synthes. The results of mechanical tests were highly correlated to the results of finite element analysis. Finite element models with low elastic modulus of bone and no frictional force between the screws and bones can better simulate the situations of mechanical testing. The finite element models built in this study may help the manufacturers evaluate new designs of locking screws before manufacture and assist surgeons to select suitable devices for their patients.

Anterior lumbar plate (ALP) systems have been widely used as an effective interbody fusion device for treating spinal cord compression. However, clinical complications, such as implant loosening and breakage, still occur. Past studies have investigated the effects of the screw orientation on the interfacial strength, but these studies were inconsistent. The purpose of this study was to identify an ALP system with excellent interfacial strength by varying the screw orientation. Three-dimensional finite element models of L4–L5 segments with an ALP system were first constructed. A neurogenetic algorithm, which combines artificial neural networks and genetic algorithms, was subsequently developed to discover the optimum plate design. Finally, biomechanical tests were conducted to validate the results of the finite element models and the engineering algorithm. The results indicated that the interfacial strength of the optimum plate design obtained using the neurogenetic algorithm was excellent compared with the other designs and that all of the locking screws should be inserted divergently. Both the numerical and experimental outcomes can provide clinical suggestions to surgeons and help them to understand the interfacial strength of ALP systems in terms of the screw orientation.

Anterior cervical discectomy and fusion is a common surgical procedure to treat spinal cord or nerve root compression. However, the clinical complications of anterior cervical plate system still occur. Past researchers have tried to improve the clinical complications by changing the screw thread or the screw orientation. The conclusion on the screw thread is quite consistent. Unfortunately, the studies on the screw orientation reached inconsistent conclusions. In addition, the effects of the screw orientation which are determined before the surgery are mainly based on the surgeon's experiences without biomechanical evidences. Therefore, the purpose of this study was to investigate the clinical performances of anterior cervical plate for the anterior cervical discectomy and fusion. Three-dimensional nonlinear finite element model, which consisted of C3-T2 multi-level spine and anterior cervical plate system, was developed to investigate the fixation stability by using ANSYS Workbench 14.5. Six desi...

Spinal pedicle screw fixations have been used extensively to treat fracture, tumor, infection, or degeneration of the spine. Cannulated spinal pedicle screws with bone cement augmentation might be a useful method to ameliorate screw loosening. However, cannulated spinal pedicle screws might also increase the risk of screw breakage. Thus, the purpose of this study was to investigate the bending performance of different spinal pedicle screws with either solid design or cannulated design. Three-dimensional finite element models, which consisted of the spinal pedicle screw and the screw's hosting material, were first constructed. Next, monotonic and cyclic cantilever bending tests were both applied to validate the results of the finite element analyses. Finally, both the numerical and experimental approaches were evaluated and compared. The results indicated that the cylindrical spinal pedicle screws with a cannulated design had significantly poorer bending performance. In addition, conical spinal pedicle screws maintained the original bending performance, whether they were solid or of cannulated design. This study may provide useful recommendations to orthopedic surgeons before surgery, and it may also provide design rationales to biomechanical engineers during the development of spinal pedicle screws.

An ad-hoc network is temporarily formed by a group of mobile hosts communicating over wireless channels without any fixed network interaction and centralized administration. When a mobile host communicates with other mobile hosts in an ad-hoc network, the routes are established via the intermediate mobile hosts as forwarding nodes. Under such a network environment an adaptive approach for routing management will be proposed in this paper. In this approach, at first the network infrastructure is constructed by several communication groups, which are called routing groups. A routing group communicates with other routing groups via the boundary mobile hosts as forwarding nodes. In a routing group the mobile hosts are divided, by means of the dominating values, into two groups — one positive cluster and several non-positive clusters. The nodes in the positive cluster maintain the topology information of the routing group. Under such a construction environment, intra-group routing performs unicasting and gets multiple paths, while inter-group routing performs on group level by propagating the route requests to the boundary clusters, which are called bridge clusters. This routing scheme massively reduces the message complexity that is especially important for system performance under such a resource constraint environment. As far as the dynamic topology characteristics of ad-hoc networks are concerned, this approach also provides a more efficient infrastructure update. Finally, simulation results show that the routing via dynamic group construction outperforms the previous works in message complexity and infrastructure update efficiency.

An optimization approach was applied to improve the design of the lag screws used in double screw nails. However, finite element analyses with an optimal algorithm may take a long time to find the best design. Thus, surrogate methods, either artificial neural networks or multiple linear regressions, were used to substitute for the finite element models. The results showed that an artificial neural network method can accurately develop the objective functions of the lag screws for both the bending strength and the pullout strength. A multiple linear regression method can successfully develop the objective function of the lag screws for the pullout strength, but it failed to construct the objective function for the bending strength. The optimal design of the lag screws could be obtained using the artificial neural network method and genetic algorithms.

MAXM is a multi-channel MAC protocol for ad hoc networks. The idea of MAXM is to maximize utilization of bandwidth by adopting a distributed self-stabilizing maximal matching-transmission algorithm. In this paper, we prove that given a fixed number, p, of packets, MAXM is able to guarantee that all packets are delivered within O(pN+pT) time in the network of N mobile hosts, where T is the time to transmit a packet on a non-conflicting channel.

A pedicle screw fixation has been widely used to treat spinal diseases. Clinical reports have shown that the weakest part of the spinal fixator is the pedicle screw. However, previous studies have only focused on either screw breakage or screw loosening. There have been no studies that have addressed the multiobjective design optimization of the pedicle screws. The multiobjective optimization methodology was applied and it consisted of finite element method, Taguchi method, artificial neural networks, and genetic algorithms. Three-dimensional finite element models for both the bending strength and the pullout strength of the pedicle screw were first developed and arranged on an L25 orthogonal array. Then, artificial neural networks were used to create two objective functions. Finally, the optimum solutions of the pedicle screws were obtained by genetic algorithms. The results showed that the optimum designs had higher bending and pullout strengths compared with commercially available screws. The optimum designs of pedicle screw revealed excellent biomechanical performances. The neurogenetic approach has effectively decreased the time and effort required for searching for the optimal designs of pedicle screws and has directly provided the selection information to surgeons.

The purpose of this biomechanical study was to compare the mechanical properties of specially designed locked nails and screws with the same structures and made from either stainless steel or titanium alloy. The structural factors investigated included inner diameter and root radius for locking screws and outer diameter and nail hole size for locked nails. The mechanical properties investigated included yield load, cyclic bending stiffness, and fatigue life. Finite element models were used to simulate the mechanical tests and compute the stress concentration factors. Increasing the root radius and the inner diameter could effectively increase the fatigue life of the locking screws. The fatigue life of titanium screws was higher (by 1.4- to >6-fold) than that of stainless steel screws, especially when the inner diameter was increased. In contrast, the fatigue life of titanium locked nails was lower (by about 1/4 to 1/3) than that of their stainless steel counterparts. Finite element models could closely predict the results of the biomechanical tests with a Pearson correlation coefficient that ranged from -0.58 to -0.84 for screws and was -0.98 for nails. The stress concentration factors ranged from 1 to 1.97 for screws and from 3.89 to 4.99 for nails. The present study suggested that with larger root radius and inner diameter, titanium locking screws could provide much higher fatigue life than stainless steel counterparts. However, titanium locked nails might lose their advantages of superior mechanical strength because of high notch sensitivity, and this limitation should be taken seriously during the design process.

MAXM is a multi-channel MAC protocol for Ad Hoc Networks. The idea of MAXM is to maximize utilization of bandwidth by adopting a distributed self-stabilizing maximal matching-transmission algorithm. In this paper, we prove that given a fixed number, p, of packets, MAXM is able to guarantee that all packets are delivered within O(pN+pT) time in the network of N mobile hosts, where T is the time to transmit a packet on a non-conflicting channel.

Selecting transparently a proper network connection for voice communication will be a fundamental requirement in future multi-mode heterogeneous wireless network. This paper extends always best connected (ABC) to a fine-grain paradigm called always best network connection (ABNC) to address this issue. Instead of selecting a best access network as in conventional ABC, ABNC enable users to select a best network connection, which consists of source and destination access network pair, to satisfy quality constraint and users' preference. To support ABNC, we develop a user profile to specify network connection priority. Meanwhile we extend SIP and propose a network selection information service (NSIS) based on MIH (media independent handover) to collect information of both source and destination access networks for decision making. Finally, analytic hierarchy process (AHP) is used to recommend a network connection with assistance of user profile and NSIS. An example is illustrated to show that AHP can successfully select a good network connection that fulfill the requirement of users.

Improper design of vertebral body cages may seriously affect the interface strength and cause the lose of fixation for a vertebral body replacement. This research used a FEM-based Taguchi method to investigate the effects of various factors to find the robust design of the body cage. Three-dimensional finite element models with a nonlinear contact analysis have been developed to simulate the pullout strength of the body cage. Then, the Taguchi robust design method was used to evaluate the spike design. In a situation without bone fusion, the spike row, the spike oblique, and the spike height were especially important factors. The optimum combination has been found to be the pyramidal spike type, a spike height of 2 mm, a spike diameter of 2.2 mm, an oblique geometry, 11 rows per 28 mm, and an inner diameter of 10 mm. In a situation with bone fusion, the spike row, the spike height, and the inner diameter were the most significant factors. Here, the optimum combination has been found to be the conical spike type, a spike height of 2 mm, a spike diameter of 2.2 mm, an oblique geometry, 11 rows per 28 mm, and an inner diameter of 20 mm. The finite element analyses could be used to predict the interface stiffness of the body cages. The FEM-based Taguchi methods have effectively decreased the time and effort required for evaluating the design variables of implants and have fairly assessed the contribution of each design variable.

This study proposes the application of the MCSCL groupware for the hearing-impaired students to engage in learning the mathematics word problems. This groupware, which integrates the collaborative argumentation theory, the scaffolding tools, and the comic, is to be applied in the activities of the collaborative learning. We present the system architecture which describes the implementation based on integration of the PDA, the network technology, and the learning strategy. Furthermore, this study employed the groupware as a channel for the hearing-impaired students to improve the experience of learning the mathematics word problems.

Fusion has been the gold standard treatment for treating lumbar degenerative disc disease. Many clinical studies have demonstrated that adjacent segment degeneration was observed in patients over time. Various instrumentations of pedicle screw-based stabilization systems have been investigated using numerical approaches. However, numerical models developed in the past were simplified to reduce computational time. The aim of this study was to evaluate and to compare the biomechanical performance of rigid, semi-rigid, and dynamic posterior instrumentations using a more realistic numerical model. Three-dimensional nonlinear finite element models of the T11-S1 multilevel spine with various posterior instrumentations were developed. The intersegmental rotation, the maximum disc stress, and the maximum implant stress were calculated. The results indicated that the rigid instrumentation resulted in greater fixation stability but also a greater risk of adjacent segment degeneration and implant failure. The biomechanical performance of the dynamic instrumentation was closer to that of the intact spine model compared with the rigid and semi-rigid instrumentations. The results of this study could help surgeons understand the biomechanical characteristics of different posterior instrumentations for the treatment of lumbar degenerative disc diseases.