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This study aimed to compare the effect of needle puncture and chondroitinase ABC (ChABC) injection on inducing intervertebral disc (IVD) degeneration (IVDD) in rabbits.Sixteen New Zealand white rabbits were used in this study. Briefly, the rabbits were divided into four groups. In the annulus fibrosis (AF) needle puncture group, a 16-G needle was used to puncture the L5-6 and L6-7 IVDs, while in the sham group, these IVDs were not punctured. In the ChABC group, 30 μL 0.5 Unit/mL ChABC was injected into L5-6 and L6-7 IVDs using a 26-G needle, while in the vehicle group, these IVDs were injected with 30 μL phosphate-buffered saline (PBS). X-ray and MRI scans were performed at the 4th, 12th and 16th weeks postoperatively. Histological, immunohistochemical and biochemical analyses were performed at the 16th week postoperatively.Both needle puncture and ChABC successfully established IVDD in rabbits at 4th, 12th and 16th weeks, confirmed by X-ray and MRI scan. The progression of IVDD went in a time-dependent manner. The IVDD in the ChABC group was less severe than in the needle puncture group throughout the study. Aggrecan and type II collagen significantly decreased, while tumor necrosis factor-α and superoxide dismutase 2 increased in the needle puncture and ChABC groups, compared with the sham and PBS groups.Both AF needle puncture and ChABC injection can successfully induce IVDD in rabbits. Compared with ChABC injection, AF needle puncture can induce more severe IVDD. more...

Stator and rotor cores of interior permanent magnet (IPM) motors are usually saturated, and the saturation distribution and saturation depth vary with the stator current. Also, their rotor structures are complex; hence the saturation cannot be accurately reflected by a saturation factor. These considerations lead to existing equivalent air-gap length models of induction motors and inset permanent magnet (PM) motors no longer suitable for IPM motors. Therefore, based on the consideration of stator and rotor saturation, this paper proposes the equivalent air-gap length model of IPM motors expressed by magnetic potentials on the stator inner surface and the rotor outer surface. The proposed equivalent air-gap length model can accurately reflect the influences of complex structure and severe saturation of IPM motors. Compared with existing models, the proposed one is no longer uniquely determined by motor structure parameters; it is also a function of stator current and rotor position. Furthermore, the obtained equivalent air-gap length model is combined with the winding function and the modified winding function to solve the inductances under different stator currents and different rotor eccentricity states. Finally, the proposed method is verified by both finite element analysis (FEA) and experiments. more...

This article proposed a predictive flux control strategy for permanent magnet synchronous machines based on flux trajectory optimization. Instead of minimizing the instantaneous flux tracking error at the end of each sampling period, the effect of different control sets on flux trajectories within the entire sampling interval is taken into account in the cost function. As a result, steady-state torque and flux ripples can be suppressed. Besides, inaccurate sector determination found in the conventional predictive control strategies can be successfully avoided. As well as highly dynamic performances inheriting from the predictive characteristics, enhanced steady-state torque control performances can be guaranteed under different operating conditions. Although the extended control set is utilized to augment the control freedom and further reduce torque ripple, the control effect of the proposed algorithm does not rely on the increase of switching frequency. Compared with the traditional predictive control strategies based on either finite control set or an extended control set, a superior control effect can be obtained while keeping a low switching frequency. Moreover, duty cycle signals are directly obtained in the prediction process, and no additional space vector pulsewidth modulation method is needed. Experimental validations and comprehensive comparison are conducted to demonstrate the effectiveness of the proposed strategy. more...

This article analyzes the realis converbs and irrealis converbs in Hwari (Dpa’ ris) Tibetan, an Amdo Tibetan dialect spoken in Tianzhu Tibetan Autonomous County, Wuwei City, Gansu Province, China. One peculiarity of Hwari Tibetan morphosyntax is the existence of a large set of converbal suffixes. A survey of previous descriptions reveals a lack of consensus in the analysis of these converbs. They have been included in the framework of Written Tibetan too often, which has led to confusion regarding their typological status. A primary objective of our paper is to rectify this approach by describing the language on its own terms by comparing the morphosyntactic behavior of eight selected suffixes with regard to relevant criteria, such as realis and irrealis. This empirical research feeds back into the theoretical discussion, as it shows that the Hwari Tibetan converbs can be described using conventional typological concepts if construed appropriately. Our second objective is to explain the semantic and pragmatic properties of these converbs, particularly -na and -ta. The conclusion is that the two converb types are located along a continuum from realis/irrealis to positive/negative, thus constituting an instantiation of syntax-semantics isomorphism. The clause chaining in Hwari Tibetan is representative. By describing the converbs in Hwari Tibetan from the perspective of realis and irrealis, and by focusing on the syntactic properties and pragmatic features of -Ce in realis converbs and -Ca in irrealis converbs, it is revealed that the irrealis converbs -na and -ta function in a unique way in Hwari Tibetan. more...

This article introduces a method to achieve the variable action period (VAP) of voltage vector in the finite control set model predictive control (FCS-MPC). In the conventional FCS-MPC, the control behavior is limited since the action period of a voltage vector is normally fixed to the sampling period. This article aims to enhance the control performances by means of regulating the action period of selected voltage vectors, together with the selection of an optimal control action. A VAP-based predictive flux control strategy is thus proposed. The optimal voltage vector and its optimal action period are both obtained by means of a two-step cost function minimization. In this manner, the future states of the control objectives are taken into account in the construction of cost function. The action period for the selected voltage vectors is no longer fixed to the sampling period, which provides an additional control freedom to obtain improved reference tracking behaviors. Experimental validations and comparison studies demonstrate that enhanced steady-state performances as well as excellent dynamic behaviors can both be obtained with the proposed strategy adopted. more...

Open-end winding permanent magnet synchronous machines (OW-PMSMs) supplied by dual inverters have gained increasing research focus due to its advantages in multilevel modulation, flexible control capability, and enhanced fault-tolerant performance. Zero-sequence current is one of the most concerned issues when the common dc bus configuration is adopted. Feedback control of zero-sequence current has been previously proved to be an effective solution to suppress zero-sequence current. However, due to the existence of current measurement errors, dc disturbance and periodic disturbances will inevitably occur in zero-sequence current, which may result in obvious deteriorations of the suppression performance of zero-sequence current. Zero-sequence current circulates in the OW-PMSM, which will lead to unexpected power losses and reduced efficiency. In addition, current measurement errors also cause increased periodic disturbances in the torque and the rotor speed, resulting in torque ripples and speed fluctuations. To address these problems, the exact closed-form hold-equivalent model of OW-PMSMs is derived, and the specific periodic disturbances introduced by current measurement errors are analyzed. Subsequently, zero-sequence current controller and speed controller are designed with enhanced mitigation capability of periodic disturbances resulting from current measurement errors. Its effectiveness under different operation conditions is confirmed experimentally on a 2.3-kW OW-PMSM setup. more...

Hot pepper (Capsicum annuum) is one of the oldest domesticated crops in the world. Pepper has poor waterlogging tolerance and flooding often leads to plant death and yield reduction. It is important to understand the molecular mechanisms involved in pepper waterlogging tolerance to cultivate new varieties with stronger tolerance. In the present study, we found that the growth rate of waterlogging-tolerant pepper varieties was not strongly affected after five days of exposure to flooding. Physiological data showed that chlorophyll content was not strongly affected by flooding, but stomatal conductance changed significantly 0–5 days after flooding and the net photosynthesis rate changed significantly 5–10 days after flooding. We also found that waterlogging-tolerant varieties showed significantly higher root activity after flooding for 10 days than a control. This suggests that the impact of flooding is related to changes in the root environment, which indirectly affects photosynthesis. A comparison of transcriptome data found that antioxidase genes, cell wall synthesis pathway genes and calcium ion regulation pathway genes may also be related to waterlogging tolerance. Other genes identified in tolerant peppers include those related to lignin synthesis regulation, reactive oxygen species (ROS) regulation pathways and others related to stress resistance. We recorded significant changes in the expression levels of these genes at five days after waterlogging, which was consistent with a significant increase in oxidase content that was also observed on the fifth day after flooding. Our results show that ROS regulation, increases in antioxidase activity, the accumulation of lignin and the expression of stress resistance genes may facilitate flooding resistance in waterlogging-tolerant peppers to flooding stress in the early stage. These results provide a foundation for further analysis of the molecular mechanisms responsible for waterlogging tolerance in pepper and may be a useful reference for the breeding of other Solanaceae plants. more...

The use of ion current signals generated during the combustion process of mixed gas as a function of initial mixture composition, temperature and pressure to detect cylinder combustion states is the most recent approach in the design, development, and optimisation of automotive engine combustion control. This paper aims to design predictive identification and computationally fast and accurate ion current models for obtaining combustion information in the engine cylinder in real time. To build a more comprehensive ion current calculation model, the effect of the flame ionisation process, the geometry of the spark plugs, and the combustion pressure and temperature are considered in the new building ion current model. The simulation ion current waveform, which has a double-peak structure, is in good agreement with the experiment values; thus, the ion current model has the potential to be used for real-time control and optimisation of engine cylinder combustion. more...

In the control of permanent magnet synchronous machines (PMSMs), predictive controllers have received considerable attention due to the enhanced dynamic responses. However, periodic disturbances caused by dead-time effects and sampling errors deteriorate the performances of PMSMs. In order to suppress periodic disturbances, one typical control structure is to adopt several corresponding resonant controllers connected in parallel with the main controller. Even though excellent steady-state performances can be obtained, coupling effects between reference tracking and periodic disturbance attenuation can be observed, leading to significant transient oscillations under the situation of a reference step change. In order to realize decoupling between reference tracking and disturbance attenuation, this paper proposes a dual-loop predictive control structure, in which the reference tracking is only determined by the primary predictive controller. Periodic disturbance attenuation is achieved through an embedded disturbance rejection loop. By applying the proposed controller, periodic disturbances are strongly attenuated while smooth and fast transient performances are simultaneously guaranteed. Furthermore, a wide range of low frequency harmonics can be successfully suppressed, including but not limited to the main periodic harmonics. The steady-state performance, dynamic responses, and robustness against parameter variations of the proposed controller are verified through experiments based on a 2.3-kW PMSM. more...

The semicontrolled open-winding permanent magnet synchronous generators (OW-PMSGs) with a common dc bus system have received more attention in recent years due to its advantages of reduced cost and simpler power supply. Good control performances could be achieved under the zero power factor angle (PFA). However, current clamping problem is normally presented under non-zero PFA condition, resulting in unexpected torque pulsations and voltage pulse disturbances. Meanwhile, misjudgment of voltage vectors and subsequent deteriorations in steady-state performances can be observed at current zero-crossing points. In order to improve the control performances of semicontrolled OW-PMSGs, a virtual zero-crossing detection method is proposed in this paper to effectively suppress the oscillation of voltage vectors at current zero-crossing points. In addition, a segment injection strategy of third-order harmonic current is proposed. With the proposed strategy adopted, the current clamping problem can be successfully solved, and more importantly, the torque ripple and third-order harmonic current could be simultaneously suppressed. Relevant experimental validations and performance comparisons based on a 2.3-kW semicontrolled OW-PMSG system are presented to verify the proposed control strategies. more...

The mass fraction burned (MFB) of the gas mixture in combustion process as the function of the combustion duration time, reflects the percentage of fuel consumed at the every moment in the combustion process, and is an important factor for analysing of the fuel combustion performance, and it has high engineering value for evaluating engine design parameters and operating performance and for improving the combustion process in-cylinder combustion process. The ion current signal directly originated from the fuel combustion process in the cylinder, and contained much information about the combustion process; the MFB of fuel in combustion process can be obtained based on the correlation between the MFB and ion current signal. In this paper, the ion current method is constructed to calculate the MFB of fuel in combustion process under different initial conditions (initial pressure from 1 bar to 3 bar, equivalence ratio from 0.8 to 1.2, hydrogen mass fraction from 0% to 10%, and CO2 dilution ratio from 0% to 10%), the method based on the waveform parameters of ion current signal for obtaining the efficiency factor and the form factor of Wiebe function, and further to slove the mass fraction burned of combustion process. The mass fraction burned is obtained through ion current method reduced assumptions error and improved the calculation accuracy compared with the well-known Rassweiler–Withrow method, and the ion current method has an advantage that not requires an high-cost sensor and some rather complex measuring instruments. The ion current method is a simple but powerful calculation model that provide a new technical path for analysing and online obtaining the MFB of fuel in combustion process. more...

The characteristics of the ionization current, pressure, and flame schlieren photos during the combustion process of natural gas-hydrogen/CO2 blends were studied using high-speed schlieren data acquisition technology and flame ionization analysis methods. According to the ion current waveform, pressure waveform, and flame propagation photos, the relationship of the characteristic parameters between the ion current and pressure were analysed using available experimental data. The ionization current waveform can reflect not only the entire combustion process (including ignition phase, the front flame phase and the post flame phase) but also the effect of the initial pressure, equivalence ratios, hydrogen fraction and CO2 dilution ratios on the combustion process. This results of this study show that the amplitude and characteristic timing of the ion current can be used to predict the change of the chamber pressure. The ion current and pressure will increase with the increase of the initial pressure, equivalence ratio and hydrogen fractions, but the parameters will decrease with the increase of the CO2 dilution ratio. The characteristic timing of the ion current and pressure peaks is advanced with the increase of the equivalence ratio and hydrogen fractions; however, the peaks are postponed by the increase in the initial pressure and CO2 dilution ratio. The corresponding relationship of the characteristic timing between the ion current and pressure is basically unchanged. The results of this study provide a new approach for exactly controlling the combustion process. more...

In this paper, an observer-based predictive vector-resonant current control strategy for permanent magnet synchronous machines is proposed, which can effectively improve system performance in case of disturbances caused by converter dead-time effect and model mismatch. Taking the external periodic, nonperiodic disturbances, and system delay into consideration, the system model in discrete-time domain is built. This model is then embedded with vector-resonant scheme with the aim of suppressing periodic disturbances resulting from converter dead-time effect and rotor flux harmonics. An extended-state observer is constructed in order to predict system behavior and to estimate the nonperiodic disturbances caused by parameter variations. The overall control law is then derived on basis of cost function minimization. With the proposed method adopted, the undesired anomalous peak around the resonant frequency in the frequency responses can be avoided. Moreover, enhanced transient performances and wider stability margin can also be obtained. The effectiveness and advantages of the proposed strategy are verified by frequency-domain analysis and comparative experimental studies. more...

The Fisher Information Matrix (FIM) determinant and the precision of the circle parameters are derived for generic configurations with n data points. The conditions for maximizing the FIM d...

To analyze the epidemiological characteristics and changing trends of lumbar fractures in Xingtai Orthopedic Hospital in the past 10 years, and to improve the prevention and treatment of lumbar fractures.Using the hospital information system, data on patients with lumbar fractures in our hospital from 2009 to 2018 were collected regarding their age, gender, fracture time, injury mechanism, and the type of fracture. The epidemiological characteristics and trends of lumbar fractures for the period were summarized and analyzed.The age of male patients with a high incidence of lumbar fractures was 61 to 70 years, followed by 51 to 60 years. The age of female patients with the highest incidence rate was 61 to 70 years, followed by 51 to 60 years (19.22%). Lumbar fractures in group A were predominantly of men. The majority of lumbar fractures in group B were of women. In group A, the incidence rate was higher in young men (21-50 years) than in women and higher in women51 years. Most of the affected individuals were women. In group B, there were more middle-aged and young men (21-50 years) than women; however, there were more women than men aged ≥51 years. Car accident injury was the main cause of fractures, but in group B women, low-energy injuries were the main cause of fractures. The periods of high incidence in groups A and B were 4 to 6 years and 7 to 9 years, respectively. The number of injuries in group A was the highest and burst fracture was the main fracture type. In group B, the number of fall injuries was the highest, followed by car accident injuries, and compression fracture was the main fracture type.The number of lumbar fractures in women caused by low-energy injuries showed an increasing trend. The type of compression fracture increased, which might be related to osteoporosis caused by the decrease in the estrogen level after menopause. more...

This study was to develop a feasible and safe animal model for minimally invasive injectable lumbar interbody fusion using a novel biomaterial, mineralized collagen-polymethylmethacrylate bone cement (MC-PMMA), with unilateral pedicle screw fixation in an in vivo goat model. Eight goats ( Capra aegagrus hircus) were divided into three groups: MC-PMMA, unmodified commercial-polymethylmethacrylate bone cement (UC-PMMA), and a control group (titanium cage filled with autogenous bone, TC-AB). Each group of goats was treated with minimally invasive lumbar interbody fusion at the L3/L4 and L5/L6 disc spaces (injected for MC-PMMA and UC-PMMA, implanted for TC-AB). The pedicle screws were inserted at the L3, L4, L5, and L6 vertebrae, respectively, and fixed on the left side. The characteristics of osteogenesis and bone growth were assessed at the third and the sixth month, respectively. The methods of evaluation included the survival of each animal, X-ray imaging, and 256-layer spiral computed tomography (256-CT) scanning, imaged with three-dimensional microfocus computed tomography (micro-CT), and histological analysis. The results showed that PMMA bone cement can be extruded smoothly after doping MC, the MC-PMMA integrates better with bone than the UC-PMMA, and all goats recovered after surgery without nerve damage. After 3 and 6 months, the implants were stable. New trabecular bone was observed in the TC-AB group. In the UC-PMMA group a thick fibrous capsule had formed around the implants. The MC-PMMA was observed to have perfect osteogenesis and bone ingrowth to adjacent bone surface. Minimally invasive injectable lumbar interbody fusion using MC-PMMA bone cement was shown to have profound clinical value, and the MC-PMMA showed potential application prospects. more...

Horizontal curve identification is important both for road safety management and railway maintenance. Parameters of a transition curve are introduced to perform an orthogonal least-squares ...

In this study, the flame propagation characteristics of premixed natural gas–hydrogen–air mixtures were studied in constant volume combustion bomb by using the high-speed schlieren photography system. The flame radius, laminar flame propagation speed and the flame stretch rate were obtained under different initial pressure, temperature, equivalence ratios and hydrogen fractions. Meanwhile, the flame stability and their influencing factors were obtained by analyzing the Markstein length and the flame propagation schlieren photos under various combustion conditions. The results show that the stretched laminar propagation speed increases with the increase of the initial temperature and hydrogen fraction of the mixture, and will decreases with the increase of the initial pressure. Meanwhile, according to the Markstein length and the flame propagation pictures, the flame stability decreases with the increase of the temperature and hydrogen fraction, and the slight flaws occurred at the early stage; at larger flame radius, the flame stability is more sensitive to the variation of the initial temperature and hydrogen fraction than to that of initial pressure and equivalence ratio. more...

Background. Fluoroscopy-guided blockade of the greater occipital nerve (GON) is an accepted method for treating the symptoms of cervicogenic headaches (CGHs). However, the spread patterns among different injectate volumes of fluoroscopy-guided GON blocks are not well defined. Objective. A cadaveric study was established to determine the spread patterns of different volumes of dye injectate within a fluoroscopic GON block. Study Design. Cadaveric study. Setting. Xingtai Institute of Orthopaedics; Orthopaedic Hospital of Xingtai. Methods. 15 formalin-fixed cadavers with intact cervical spines were randomized in a 1 : 1 : 1 ratio to receive a fluoroscopy-guided GON injection of a 2, 3.5, or 5 ml volume of methylene blue. The suboccipital regions were dissected to investigate nerve involvement. Results. The suboccipital triangle regions, including the suboccipital nerves and GONs, were deeply stained in all cadavers. The third occipital nerve (TON) was stained in 7 of 10 administered 2 ml injections and in all the 3.5 ml and 5 ml injections. Compared to the 3 ml injectate group, the 5 mL cohort consistently saw injectate spreading to both superficial and distant muscles. Limitations. Given that cadavers were used in this study, cadaveric soft tissue composition and architecture can potentially become distorted and consequently affect injectate diffusion. Conclusions. A 3.5 or 5 mL fluoroscopy-guided GON injection of methylene blue successfully stains the GON, TON, and suboccipital nerves. This suggests that such an injection would generate blockade of all three nerve groups, which may contribute to the efficacy of the block for CGH. A volume of 3.5 ml may be enough for the performance of a fluoroscopy-guided GON block for therapeutic purposes. more...

The effects of initial pressure, equivalence ratio, hydrogen fraction, and CO2 dilution ratio on the characteristics of ion currents and heat release rate (HRR) were comparatively investiga...