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Background Percutaneous vertebroplasty was the most common strategy for osteoporotic vertebral compression fracture. However, refracture after vertebroplasty also occurred and bone mineral density (BMD) was one of the main factors associated with refracture after percutaneous vertebroplasty. Aims To investigate the efficacy of a short-sequential treatment of teriparatide followed by alendronate on prevention of refracture after percutaneous vertebroplasty in osteoporotic patients, and compare it with the therapy of alendronate alone. Methods From January 2018 to January 2020, we recruited 165 female osteoporosis patients after percutaneous vertebroplasty who were assigned into sequential treatment of teriparatide followed by alendronate group (TPTD + ALN group) and alendronate alone group (ALN group). The vertebral fracture occurred during this process was also recorded in both the groups. A total of 105 participants completed the 1-year follow-up. Furthermore, BMD and serum procollagen type I N-terminal propeptide (PINP) and C-terminal cross-linking telopeptide of type I collagen (CTX) were compared between the two groups during 1-year follow-up. Results The 105 patients were finally included, with 59 in ALN group and 46 in TPTD + ALN group. During 1-year follow-up, the vertebral refracture rate in TPTD + ALN group was much lower than that in ALN group (2.2% vs. 13.6%, p p Discussion and conclusion A short-sequential administration of teriparatide followed by alendronate was more effective in elevating the BMD and decreasing the refracture rate at 12-month follow-up, compared to the counterpart with alendronate alone.

This paper deals with the robust fault detection problem in the finite frequency domain for a class of Lipschitz nonlinear systems with uncertain parameters. The design conditions of H − / L ∞ fault detection observers are proposed. These conditions make the error estimation system stable, and the residual has L ∞ disturbance attenuation performance for external disturbances and uncertain parameters. In addition, considering that fault occurs in the finite frequency domain, the residual also has H − fault sensitivity performance. To ease of solution, the observer design conditions are further transformed into linear matrix inequalities. On this basis, a dynamic threshold design method based on L ∞ analysis is presented. Finally, simulation results demonstrate the superiority of the proposed method.

Osteoporotic vertebral compression fracture (OVCF) is a common cause of pain and disability and is steadily increasing due to the growth of the elderly population. To date, percutaneous vertebroplasty (PVP) and percutaneous kyphoplasty (PKP) are almost universally accepted as appropriate vertebral augmentation procedures for OVCFs. There are many advantages of vertebral augmentation, such as short surgical time, performance under local anaesthesia, and rapid pain relief. However, there are certain issues regarding the utilization of these vertebral augmentations, such as loss of vertebral height, cement leakage, and adjacent vertebral refracture. Hence, the treatment for OVCF has changed in recent years. Satisfactory clinical results have been obtained worldwide after application of the OsseoFix System, the SpineJack System, radiofrequency kyphoplasty of the vertebral body, and the Kiva VCF treatment system. The following review discusses the development of the current techniques used for vertebral augmentation.

Abstract: Bone and cartilage regeneration is a dynamic and complex process involving multiple cell types such as osteoblasts, osteoclasts, endothelial cells, etc. Stem cells have been proved with efficient capability to promote bone and cartilage regeneration and repair but the usage of cells harbors some important safety issues, such as immune rejection and carcinogenicity. Exosomes are non-cell structures secreted from various cells. The content of exosomes is enriched with proteins, such as cytoskeleton proteins, adhesion factors, transcription factors, etc. and a variety of nucleic acids, such as mRNA (Messenger RNA), long-chain non-coding RNA, microRNA (miRNA), etc. Exosomes can deliver a variety of contents from the parent cells to the recipient cells in different tissue backgrounds, influencing the phenotype and function of the recipient cells. Recent studies have demonstrated that miRNAs play significant roles in bone formation, suggesting that miRNAs may be novel therapeutic targets for bone and cartilage diseases. Exosomes have been shown with low/no immune rejection in vivo, no carcinogenic risk of infection, nor other side effects. In recent years, stem cell exosomes have been utilized to promote bone and cartilage regeneration processes during bone defect, bone fracture, cartilage repair, osteoporosis and osteoarthritis. In this review, we discuss different exosomes derived from stem cells and their interactions with target cells, including osteoblasts, chondrocytes and osteoclasts. We also put special highlights on the various signaling pathways involved in stem cell exosome-related bone and cartilage regeneration.

Early fault diagnosis of bearings is the basis of condition-based maintenance. To overcome the difficulty of early fault diagnosis for the mechanical system, a new conception named quantile multiscale permutation entropy (QMPE) is defined, and a new feature extraction method based on QMPE is proposed. On the basis of the multiscale entropy, the multiscale permutation entropy for the gathered vibration signal of equipment is obtained, and the sample quantile is calculated, which is employed to analyze the weak change of the variation signal. The proposed method is verified with the full lifetime datasets of a certain bearing, which proves that signal features extracted by the QMPE method can not only truly express the bearing detailed condition changing from normal to fault but also duly detect the early fault of the bearing. Comparing with other methods for early fault diagnosis, the proposed method can advance the finding time of the early fault obviously.

The oxidative pyrolysis properties of cellulose, xylan, lignin, and rice straw were studied by thermogravimetric analysis–differential scanning calorimetry (TGA–DSC) coupled with mass spectrometry. The mass loss, reaction heat, and volatile release properties were analyzed to reveal the role of oxygen in the biomass thermal degradation process. Differential thermogravimetry (DTG) results show that the primary mass loss peak was brought forward with the increase of the oxygen concentration for all samples as well as the peak value. Oxygen improved the degradation rate of lignocellulose. The oxidative pyrolysis processes of all four types of material were accompanied by energy consumption or release, generally divided into three stages: moisture release stage, primary pyrolysis stage, and char evolution or oxidation stage. The primary degradation of cellulose under inert and 1% O2 atmospheres was distinctly endothermic. With the increase of the oxygen concentration, the endothermic peak decreased, while an ...

A lab scale two staged hot rod reactor was constructed to stimulate the two staged downdraft biomass gasifier. The present study focused on the heterogeneous conversion of the pyrolysis tars over biomass char. A typical Chinese agricultural waste, the rice straw, was chosen for the raw material and the source of the biomass char. Effects of the temperature, the presence of the char and pretreatments of the char, including the water washed char and the char added with K 2 CO 3 powder, on the pyrolysis tar removal were investigated. The products of tars were qualitatively and quantitatively analyzed. The evolution of the inner pore structure of chars with different temperatures and residence times was also investigated. The char bed condition exhibited higher tar conversion efficiency than the thermal cracking condition. The results indicated that the presence of the char could catalytically promote the formation of alkyl monoaromatics and meanwhile inhibit the formation of PAHs (polycyclic aromatic hydrocarbons) from the primary tars. The alkali metal elements might play a key role for the catalytic effect of the char. The appropriate increases in the temperature and the residence time for the char production could promote the development of the micro pores in chars.

In order to reveal the synergy effect of partial oxidation and bio-char on tar reduction and develop more efficient tar removal method, the tar and bio-char evolution properties were investigated on a bench-scaled fixed-bed reactor. The tar components, tar conversion rates, physical and chemical structure of bio-char after reaction at the second stage were sampled and analyzed. Results showed that at 700 °C, the coupling of char and oxygen could result in the significant improvement of tar conversion rate (89.32%) than both two separated method (85.1% and 86.14%). At 900 °C, the synergy effect could reach the highest conversion rate of 95.84%. High oxygen concentration coupling with char may lead to carbon deposition and bring down tar conversion rate at 800 °C. But a light amount of oxygen greatly promoted the formation of porosity. The reaction between tar and bio-char at high temperature (800 °C above) was in favor of toluene conversion. The coupling of char and partial oxidation benefited the elimination of larger PAHs tar compounds as well as toluene. BET analysis results showed that oxygen promoted the development of bio-char porosity at 700 °C and 900 °C under all oxygen concentrations. Slight amount of oxygen would benefit the char pore development, but high oxygen concentration (5%) would lead to the carbon deposition on char pore surface at 800 °C. FTIR results indicated that temperature and oxygen promoted the aromatic or graphitization of bio-char. The IR band peak of 1060 cm −1 showed the similar tendency with aromatic ring band peak, which meant more carbon deposition on the surface of char pore but not graphitization. The coupling of partial oxidation and char catalysis is a feasible method for tar reduction of biomass tar.

A novel sorbent for the removal of fluoride is prepared by immobilizing Zr(IV) on carboxymethyl cellulose sodium (CMC-Zr). Batch adsorption experiments are performed on factors of pH, temperature, initial fluoride concentration, adsorbent dosage and contact time to evaluate the adsorption capacity. The results show that the saturation adsorption capacity is 47 mg/g at pH 4.0, 25 °C, concentration 300 mg/L for 24 h. Adsorption process could be well described by Langmuir isotherm model. The adsorption kinetic data is fitted well with pseudo-second-order model. Thermodynamic parameters are also evaluated and the results indicate that adsorption of fluoride on CMC-Zr is a spontaneous and endothermic process. The mechanism of modification and adsorption process on CMC-Zr is analyzed by FT-IR, SEM-EDX and XPS. Results show that Zr(IV) is loaded on CMC through ion exchange of sodium of CMC and surface adsorption, coordination reaction happened during the adsorption process between CMC-Zr and fluoride. CMC-Zr adsorbent is a promising adsorbent for the removal of fluoride from aqueous solutions.

Oxidative pyrolysis of pinewood was studied on a bench-scaled fixed-bed reactor. The qualitative and quantitative analysis of oxidative pyrolysis products, including permanent gases (CO, CO2, and CH4), water, char, and tar, was conducted. Two important parameters (temperature and oxygen concentration) were taken into consideration. Results showed that oxygen improved the yields of permanent gas and water but decreased the yields of char and tar. In comparison to char and water, oxidative pyrolysis had a greater effect on permanent gas and tar yields. CO and CH4 were mostly released between 300 and 400 °C, while CO2 was produced at all of the temperature investigated. CO2 was always the dominant gas in all cases. At a relatively low temperature (300 °C), the adsorption of an oxygen molecule on the reactive center and the subsequent decarbonylation reaction lead to the production of CO2. Little CO and CH4 generated when the temperature was higher than 400 °C. Gravimetric results of pyrolysis tar indicated t...

The tar problems are the major limit for development of biomass gasification. Biomass char has been proven to be an economical and effective catalyst of tar destruction for both utilizations inside the gasifier and in downstream processes after the gasifier. In order to investigate the mechanism of catalytic cracking of tar over a biomass char bed, experimental research was performed in a bench-scale tube flow reactor, choosing rice straw char as the catalyst bed, naphthalene as the model tar compound, and argon as the inert atmosphere. The effects of temperature (700–1000 °C), tar concentration, time on stream (0–330 min), presence of syngas, and pretreatment of char (treated with deionized water or Ni(NO3)2 solution) on tar conversion were evaluated. The variation of the inner pore structure of biomass char during the process of tar removal was also investigated. Results showed that the original biomass char exhibited good catalytic activity in tar cracking and better stability compared with Ni(NO3)2 pr...

This paper presents digital panel assembly (DPA) methodologies and applications for sheet component assembly in automotive body manufacturing processes. Core to DPA is the customized finite element analysis formulas we have developed, which simulates assembly processes and predicts assembly dimensions by taking into consideration the panel compliances. Two key analysis types of the DPA are presented, the deterministic analysis and variation analysis. We present a methodology to utilize the quadratic form of Taylor series expansion to approximate the assembly dimensions efficiently in variation simulation, and discuss its pros and cons versus the traditional Monte Carlo method under different modeling conditions. For either the deterministic or variation analysis, linear models (without contact, efficient but less accurate), and nonlinear models (with contact, less efficient but accurate) can be established. It is shown that the linear models are only valid when panels do not penetrate, and that the nonlinear models should generally be used for accurate assembly dimension prediction. Based on the DPA methodologies, a software tool called Elastic Assembly Variation Simulation (EAVS) is presented, followed by application case studies. The confidence intervals for variation analysis are also discussed.

This paper presents a general theory to determine the sensitivity of tolerances to the performance quality of mechanisms and a technique to identify a robust design, which is the least sensitive to the tolerances. The method is demonstrated in position synthesis of linkages. The sensitivity Jacobian is first introduced to relate the performance tolerances and the dimensional tolerances. The Rayleigh quotient of the sensitivity Jacobian, which is equivalent to Taguchi’s signal to noise ratio, is then used to define the performance quality and a sensitivity index is introduced to measure the sensitivity of the performance quality to the dimensional tolerances for the whole system. The ideal tolerance distribution is obtained in closed form. It shows how the tolerance specification affects the performance quality and that the performance quality can be significantly improved by tightening a key tolerance while loosening the others. The theory is general and the technique can be adapted easily for other mechanical systems, including multiple-loop linkages.

This paper presents methodologies and results of variation simulations for digital panel assembly, using GM proprietary software called EAVS. EAVS provides two alternative algorithms for variation simulation of digital panel assembly, i.e., Taylor Series Expansion (TSE) based and Monte Carlo Simulation (MCS) based. In this paper, algorithms of the two methods are reviewed, and pros and cons are studied. Several case studies are presented to illustrate the capabilities of the two methods. Based on the case studies, the EAVS variation simulation guidelines will be established ensuring analysis accuracy at reasonable computational time.Copyright © 2003 by ASME

A new method for evaluating the robustness of compliant assembly systems is developed based on previously developed variation simulation models. This method can be used for selecting a robust assembly system at product/process development stage. Examples are presented to illustrate the proposed method.

An automotive body assembly system usually consists of processes and machines in a multi-leveled hierarchy. As a result, dimensional variation in the final product is accumulated as the product moves along the assembly system. To identify variation problems in such a complex system, proper design and placement of measurement systems is essential. In this paper, analytical models are proposed to aid the design of measurement configurations. First, the concept of assembly fault diagnosability for automotive body assemblies is introduced so that which stations or subassemblies in the multi-leveled assembly system need to be measured can be identified. Second, quantitative indices are proposed to evaluate measurement configurations so that effective fault diagnosis can be achieved optimally. Finally, a simple 1-D sheet metal assembly and an automobile door assembly are given as examples to demonstrate the effectiveness of the proposed methodologies.

By employing Taguchi’s concept to mechanism synthesis, this paper presents the theory and technique to identify a robust design, which is the least sensitive to the tolerances, for mechanisms and to determine the tolerance specification for the best performance and manufacturability. The method is demonstrated in finite and infinitesimal position synthesis. The sensitivity Jacobian is first introduced to relate the performance tolerances and the dimensional tolerances. The Rayleigh quotient of the sensitivity Jacobian, which is equivalent to Taguchi’s signal to noise ratio, is then used to define the performance quality and a sensitivity index is introduced to measure the sensitivity of the performance quality to the dimensional tolerances for the whole system. The ideal tolerance specification is obtained in closed form. It shows how the tolerance specification affects the performance quality and that the performance quality can be significantly improved by tightening a key tolerance while loosening the others. The theory is general and the technique is readily adaptable to almost any form and type of mechanical system, including multiple-loop linkages and mechanical assemblies or even structures.