Search

Accurate parameter estimation of photovoltaic (PV) cells is crucial for establishing a reliable cell model. Based on this, a series of studies on PV cells can be conducted more effectively to improve power output; an accurate model is also crucial for the operation and control of PV systems. However, due to the high nonlinearity of the cell and insufficient measured current and voltage data, traditional PV parameter identification methods are difficult to solve this problem. This article proposes a parameter identification method for PV cell models based on the radial basis function (RBF). Firstly, RBF is used to de-noise and predict the data to solve the current problems in the parameter identification field of noise data and insufficient data. Then, eight prominent meta-heuristic algorithms (MhAs) are used to identify the single-diode model (SDM), double-diode model (DDM), and three-diode model (TDM) parameters of PV cells. By comparing the identification accuracy of the three models in two datasets in detail, the final results show that this method can effectively achieve parameter extraction, with advantages such as high extraction accuracy and stability, greatly improving the accuracy and reliability of parameter identification. Especially in the TDM, the I-V data and P-V data obtained from the PV model established through the identified parameters have very high fitting accuracy with the measured I-V and P-V data, reaching 99.58% and 99.65%, respectively. The research can effectively solve the low accuracy problem caused by insufficient data and noise data in the traditional method of identifying PV cells and can greatly improve the accuracy of PV cell modeling. It is of great significance for the operation and control of PV systems.

Six-axis motion is essential for the evaluation of the wear failure modes of dental prostheses with complete teeth morphologies, and a high occlusal force capacity is vital for static clenching and dynamic bruxism. Additionally, the saliva environment influences abrasive particles and crack growth. The present research was aimed at the development of a six-axis masticatory and saliva simulator with these capacities. The masticatory simulator was designed based on a six-axis parallel mechanism, and the saliva simulator consisted of a saliva circuit and a temperature control loop. A control system of the masticatory and saliva simulators was constructed. The operating interface includes a centric occlusal position search, a static test, a dynamic test, a saliva supply, and data reporting. The motion and force performances of the masticatory simulator were evaluated. The flow rate and temperature change of the saliva simulator were calculated. For the occlusal position-searching, the driving amplitude is linear with the moving variables during minor one-axis motion. For the static tests, the force capacity of the driving chain is 3540 N, while for the dynamic tests, the force capacity is 1390 N. The flow rate of the saliva is 0.18–51.84 mL/min, and the saliva can effectively wet the prosthesis without the risk of overflow. Moreover, the saliva temperature can increase from room temperature (23°C) to body temperature (37°C) in about 6 min. The proposed DUT-2 simulator with six-axis motion, high force, and a salvia environment provides an in vitro testing approach to validate numerical simulation results and explain the clinical failure modes of prostheses. The centric occlusal position-searching, static tests, and dynamic tests could therefore be executed using a single testing machine. Moreover, the proposed device is more compact than previously reported six-axis masticatory simulators, including the Bristol simulator and DUT-1 simulator.

The rhythmic chewing movement pattern is dynamically reshaped to adapt to a variable chewing environment. The variance affects the wear performance of dental prostheses. This study was aimed to generate these variable rhythmic chewing movements for dental testing equipment. A six-axis parallel chewing robot DUT-2 was adopted as the dental testing equipment. Four variances were extracted from the rhythmic movement, including period, offset, amplitude, and mode. The relevant movement cases, including gradually accelerating movement, gradually increasing movement, gradually shrinking movement, and bilateral movement, were designed. Then, a central pattern generator (CPG) model based on morphed phase oscillators was proposed. According to the coupling feature of the rhythmic movements, the specific modulation method of the CPG model was provided for these movements. The simulated incisor trajectory was outputted by importing the driving amplitudes from the CPG model to the virtual prototype of the chewing robot. The bite force (considering two-body and three-body contacts) was analyzed by writing the driving amplitudes into the motion controller of the chewing robot’s physical prototype. The relative errors of offset and amplitude in the z-direction were 4.14% and 0.74%, respectively. The transition was smooth around the turning point during the gradually increasing movement and bilateral movement. For two-body contact, the average relative error and bias of the maximum bite force were 4.15% and 1.08%, respectively. The food involvement decreased the accuracies to 13.18% and 2.50%, respectively. The CPG model supplies a bionic and explicit approach for generating the variable rhythmic chewing movements. The variable movements related to chewing preferences and food properties could be replicated. Besides, the high repeatability of the maximum bite force is beneficial for running the repetitive wear tests. Finally, the CPG model makes it possible to study the influence of the variance on wear performance.

The full-contact model has been widely used in tooth preparation and prosthesis fabrication. However, it is rarely used in denture tests. The purpose of the present study was to design a suitable full-contact dental model for denture tests.A standard dental model with the complete tooth morphology was raster scanned and 3D reconstructed. Then, the positioning and fixing surfaces of the dental model were reshaped. The dental model was digitally trimmed into two parts: a fundamental part and a replaceable part. The modular design was presented according to dentition defects around the first molar. The prepared tooth replicas were designed through preparation/scanning/registration/separation sequences. The dental model was fabricated by stereolithography (SLA) 3D-printing rapid prototype technology. The static fracture force of the dental model was predicted using the finite element method. The effects of the four design methods on the suitability of the five testing operations (abutment fabrication, prosthesis fabrication, assembling, loading, and observation) were quantitatively analyzed. The static tests of three fixed partial dentures (FPDs), including tooth-supported, implant-supported, and tooth-tooth-supported prostheses, were conducted to investigate the fracture feature. The dynamic test of a removable partial denture (RPD) was undertaken to study the wear characteristic.The dental model could bear the maximum fracture strength of 4268.3 N. Seven positive and two negative effects of the design methods were produced. The maximum fracture strength of the FPDs were 1331.2 N, 1356.7 N, and 1987.7 N. The wear facets of the RPD in the dynamic denture test were distributed in three regions.The force capacity of the full-contact dental model allows the application of static denture tests. The dental model provides improvements in fixture design, removable design, and replica design for the testing operations. The dental model is recommended more in the dynamic test than in the static test.

The effects of mixotrophic cultivation on antioxidation and lipid production of Chlorella vulgaris in wastewater treatment were analyzed. The biomass and lipid content of the mixotrophic C. vulgari...

A 4-DOF redundantly actuated parallel robot (RAPR) for jaw movement achieved by adding two point-contact constraints (higher-kinematic-pairs, HKPs) is presented. The inverse dynamics and driving force optimization model based on pseudo-inverse method are established. In order to overcome the disequilibrium of driving forces of the redundant chains caused by inclusion of point-contact constraints, an optimized torque distribution based force/position hybrid control (OTDFP control) method for trajectory tracking is proposed for this RAPR. Experiments are carried out to evaluate the OTDFP control. Comparison with the conventional position control is performed, showing that the OTDFP control can reduce torque fluctuation and tracking errors of the RAPR. The chewing experiment of silicone shows the RAPR is not only able to track mandibular movement, but also able to emulate chewing force and temporomandibular joint (TMJ) force under the OTDFP control.

In this paper, fracturing flowback fluids were biologically treated by immobilized chlorella. The individual and interactive effects of three variables (sodium alginate concentration, CaCl2 concentration, and crosslinking time) on growth of immobilized algal were optimized by response surface methodology combined with Box-Behnken design. The results showed that the SA (sodium alginate) concentration most significantly affected algal density and treatment efficiency. The interaction between SA concentration and crosslinking time was weak, the interaction between CaCl2 concentration and crosslinking time was modest, while the interaction between SA concentration and CaCl2 concentration was significant. The immobilized chlorella performed the best when the SA concentration, CaCl2 concentration and crosslinking time were 2.42%, 2.69% and 16.76 h, respectively, and the COD removal rate of fracturing flowback fluids was significantly higher than that of the free algal (34.70% vs. 8.96%), indicating immobilization could improve growth and organics removal of chlorellas for processing fracturing flowback fluids.

PURPOSE To evaluate the stress distribution during chewing in a realistic loading condition on a prosthesis (single-tooth crown) using a static analysis. MATERIALS AND METHODS An all-ceramic crown in the mandibular first molar was selected as the representative prosthesis. First, three contact states (intrusive state, transition state, and extrusive state) were selected from the parametric chewing trajectory. Then, the distances between the antagonistic molars and the normal vectors of the mandibular first molar were calculated by using an automated contact analysis routine (independently developed). Next, normal and tangential forces were defined based on the contact information and the food property. Finally, the static analysis was executed by applying the force and the fixed boundary condition. RESULTS The distribution of the occlusal force was nonuniform in the static analysis. Compared to concentrated and uniform loading conditions, the stress distribution of the prosthesis under the nonuniform loading condition revealed new characteristics. CONCLUSION The generation procedure of the static analysis, based on fundamental contact analysis, was evidence-based. The static analysis with the nonuniform loading condition was more recommended than the other two conditions.

Stress distribution of denture is an important criterion to evaluate the reasonableness of technological parameters, and the bite force derived from the antagonist is the critical load condition for the calculation of stress distribution. In order to improve the accuracy of stress distribution as much as possible, all-ceramic crown of the mandibular first molar with centric occlusion was taken as the research object, and a bite force loading method reflecting the actual occlusal situation was adopted. Firstly, raster scanning and three dimensional reconstruction of the occlusal surface of molars in the standard dental model were carried out. Meanwhile, the surface modeling of the bonding surface was carried out according to the preparation process. Secondly, the parametric occlusal analysis program was developed with the help of OFA function library, and the genetic algorithm was used to optimize the mandibular centric position. Finally, both the optimized case of the mesh model based on the results of occlusal optimization and the referenced case according to the cusp-fossa contact characteristics were designed. The stress distribution was analyzed and compared by using Abaqus software. The results showed that the genetic algorithm was suitable for solving the occlusal optimization problem. Compared with the reference case, the optimized case had smaller maximum stress and more uniform stress distribution characteristics. The proposed method further improves the stress accuracy of the prosthesis in the finite element model. Also, it provides a new idea for stress analysis of other joints in human body.义齿应力分布数据是评价义齿工艺参数合理性的重要判据，而源于对颌牙的咬合力是计算该数据的关键载荷条件。为了尽可能地提高义齿应力分布数据的准确性，本文以正中咬合下的下颌第一磨牙全瓷冠为研究对象，采用一种能够反映咬合实际状况的咬合力加载方式。首先对标准牙颌模型中下颌第一磨牙咬合面形貌进行光栅扫描与三维重建，同时根据预备体制备工艺进行结合面的曲面造型，并运算得到义齿与预备体几何模型；其次，借助咬合动力学分析软件（OFA）函数库开发参数化的咬合分析程序，并使用遗传算法对正中颌位进行优化；最后，基于咬合优化结果设计网格模型优化工况，同时以尖窝接触特征设计参考工况，将以上数据均导入有限元分析软件 Abaqus 中进行应力分布的对比分析。本文研究结果表明，遗传算法适用于咬合优化问题的解决；相较于参考工况，咬合优化后的义齿具有更小的应力最大值和更均匀的应力分布特征。基于以上研究结果证明，本文所提出的正中咬合优化方法能够进一步提升义齿在有限元模型中的受力准确性，也为人体其他关节的受力分析提供了新思路。.

As a representative part of the oral system and masticatory robot system, the modeling method of the dental model is an important factor influencing the accuracy of the multi-body dynamic model. Taking the right first molars of the masticatory robot as the research object, an equivalent model, point-contact higher kinematic pair composed of v-shaped surface and sphere surface, was proposed. Firstly, the finite element method was used to analyze the occlusal dynamics of the original model in three static contact cases (intrusive contact, centric occlusion, and extrusive contact) and one dynamic chewing case, and the expected bite force was obtained. Secondly, the Hertz contact model was adopted to establish the analytical expression of the bite force of the equivalent model in three static contact cases. The normal vectors and contact stiffness in the expression were designed according to the expected bite force. Finally, the bite force performance of the equivalent model in three static contact cases and one dynamic chewing case was evaluated. The results showed that the equivalent model could achieve the equivalent bite force of 8 expected items in the static contact cases. Meanwhile, the bite force in the early and late stages of the dynamic chewing case coincides well with the original model. In the middle stage, a certain degree of impact is introduced, but it can be weakened by subsequent trajectory planning. The equivalent modeling scheme of the dental model proposed in this paper further improves the accuracy of the dynamic model of the multi-body system. It provides a new idea for the dynamic modeling of other complex human contacts.牙颌模型作为口颌系统与咀嚼机器人系统的代表性部件，其建模方式是影响此类多体系统动力学模型准确度的重要因素。本文以咀嚼机器人右侧第一磨牙为研究对象，提出一种由 V 型面与球面构成的点接触高副等效建模方式。首先，利用有限单元法对原始模型的 3 种静态接触工况（咬入接触、正中接触、咬出接触）与动态咀嚼工况进行咬合动力学分析，得到期望咬合力；其次，运用赫兹接触模型建立点接触高副等效模型静态接触工况的咬合力解析式，根据期望咬合力对解析式内法向量与咬合刚度等参数进行等效设计；最后，对等效模型在静态接触与动态咀嚼工况中的咬合力表现进行评价。本文结果表明，等效模型能够实现静态接触工况 8 项期望咬合力的等效，同时对动态咀嚼工况初期与末期咬合力变化吻合良好，中期引入一定程度的冲击，但可通过后续轨迹规划进行弱化。本文所提出的牙颌模型等效建模方案，进一步提升了多体系统动力学模型准确性，也为人体其他复杂接触的动力学建模提供了新思路。.

Masticatory robots have a broad application prospect in the field of denture material tests and mandible rehabilitation. Mechanism type of temporomandibular joint structure is an important factor influencing the performance of the masticatory robot. In view of the wide application of elastic components in the field of the biomimetic robot, an elastic component was adopted to simulate the buffering characteristics of the temporomandibular joint disc and formed the elastic temporomandibular joint structure on the basis of point-contact high pair. Secondly, the influences of the elastic temporomandibular joint structure (on mechanism degree, kinematics, dynamics, etc.) were discussed. The position and velocity of the temporomandibular joint were analyzed based on geometric constraints of the joint surface, and the dynamic analysis based on the Lagrange equation was carried out. Finally, the influence of the preload and stiffness of the elastic component was analyzed by the response surface method. The results showed that the elastic temporomandibular joint structure could effectively guarantee the flexible movement and stable force of the joint. The elastic joint structure proposed in this paper further improves the biomimetic behavior of masticatory robots. It provides new ideas for the biomimetic design of viscoelastic joint discs.咀嚼机器人在义齿材料测试和下颌康复训练领域具有广阔的应用前景，而颞下颌关节的机构型式是影响咀嚼机器人性能表现的重要因素。鉴于目前弹性元件已在仿生机器人领域得到广泛应用，因此本文在点接触高副的基础上采用弹性元件模拟颞下颌关节内关节盘缓冲振荡的生物力学特点，形成弹性颞下颌关节机构型式；然后，本文探讨了弹性颞下颌关节对咀嚼机器人在自由度、运动学与动力学等方面的影响，根据关节面几何约束对颞下颌关节的位置与速度进行运动学分析，并进行基于拉格朗日方程的动力学分析；最后，使用响应面法对弹性元件预载荷以及刚度取值的影响进行分析。本文结果表明，弹性颞下颌关节能够有效保证关节的灵活运动与稳定受力。综上，本文所提出的弹性颞下颌关节机构方案进一步提升了咀嚼机器人仿生性，也为粘弹性关节盘的仿生设计提供了新思路。.

Purpose: The chewing trajectory in the dynamic analysis of dental prosthesis is always defined as a two-segmental straight polyline without enough consideration about chewing force and motion laws. The study was aimed to design a realistic human chewing trajectory for the dynamic analysis based on force and motion planning methods. Methods: The all-ceramic crown restored in the mandibular first molar was selected as the representative prosthesis. Firstly, a dynamic model containing two molar components and one flat food component was built, and an approximate chewing plane was predefined. According to the desired forces (25 N, 150 N and 25 N), three force planning points were calculated by using tentative trajectories. The motion planning was then executed based on four-segment cubic spline model. Finally, the new trajectory was re-imported into the dynamic model as the displacement load for evaluating its stress influence. Results: The maximum lateral velocity was 26.81 mm/s. Besides, the forces in the three force planning points were 14.11 N, 126.75 N and 13.56 N. The overall repetition rate of chewing force was 77.21%. The force and stress profiles were similar to the sine curve on the whole. The maximum dynamic stress of the crown prosthesis was 398.5 MPa. Conclusions: The motion law was effectively brought into the chewing trajectory to introduce the dynamic effect. The global force performance was acceptable, and the force profile was more realistic than the traditional chewing trajectory. The additional reliable characteristic feature of the stress distribution of the dental prosthesis was observed.

An extended floor field model was proposed to investigate evacuation behaviors of pedestrians under the threat of artificial attack. In this model, pedestrian movement governed by the static and dynamic floor field, and the motion and assault of artificial attacker were involved simultaneously. Further, injuries with lower velocity and deaths of pedestrians caused by the attacker during evacuation were considered. And a new parameter k t was introduced. It is the sensitivity coefficient of attack threat floor field and could reflect quantitatively the extent of effect of attack threat on the decision-making of the individual. Moreover, effects of several key parameters such as the sensitivity coefficient, assault intensity and pedestrian density on evacuation dynamics were studied. Results show that pedestrian evacuation would display interesting phenomena transiting from rolling behavior to along-the-wall motion with aggravating extent of the impact of attackers on pedestrians, which refers k t in the model varying from 0.5 to 0.8. As assault intensity increases, more casualties would be caused and the available evacuation time would decrease, which means people have to flee the room in a shorter time period for survival. When the pedestrian density increases, more clogging at the exit would be generated and pedestrians would be more difficult to evacuate due to the limited capacity of egress and the reduction in the average speed of pedestrian flow caused by the injured. And the injured with limited motion capacity could hardly complete the evacuation owing to that they need more evacuation time and would retard the speed of the pedestrian flow.

The effects of mixotrophic cultivation on antioxidation and lipid production of

In this paper, a highly sensitive and selective method based on the poly (sulfosalicylic acid) modified electrode (PSA /CPE) to detect phenol was established. The morphologies and interface properties of PSA film were characterized by scanning electron microscopy and electrochemical impedance spectroscopy. It was illustrated that the PSA/CPE had an excellent electrocatalytic ability towards the oxidation of phenol. Meanwhile the influence of parameters such as pH and scan rate effect on the analytical performance of the sensor was evaluated. Moreover, the interference from o-nitrophenol can be neglected. By using differential pulse voltammetry (DPV), linear calibration curves were obtained as 5–175 and 220–555 μmol L−1 for phenol. The detection limits are 2.2 μmol L−1 for phenol. With favorable selectivity and sensitivity, the present method has been applied to the determination of phenol in oilfield wastewater.

Summary This paper details the study of a new fracturing fluid that is based on a supramolecular complex between associative polymer and viscoelastic surfactant (VES). The crosslinked complex gel was based on weak physical attractive forces, such as van der Waals, hydrogen bonding, and electrostatic interaction between associative polymer and wormlike micelles of VES. The concentration of surfactant in the new fluid is 10 times less than that of VES fracturing fluid. The combination of VES and associative polymer synergistically enhances the viscosity to several times more than that of the individual components alone. The fluid system was optimized by experimental design. The microstructure of wormlike micelles and complex formation was verified by electron microscopy. The fluid is shear stable at high temperature for 1 hour. The dynamic rheological properties of the supramoleulcar fluid show high viscoelasticity, in which the elastic moduli are higher than the loss moduli below an angular frequency of 0.1 rad/s. The proppant-transport test in a large-scale fracture simulator showed good proppant-suspension ability. The fluid has 50% lower formation damage than conventional guar. The fluid was prepared with fewer additives, formed gel instantly, and can be mixed on the fly in the field. The gel can be completely broken with almost no residue. Field application of the new fracturing fluid in a gas well showed the enhancement of gas production by more than 100%. The fluid has 20% lower friction pressure than guar fluid. Hence, the new supramolecular fluid is an effective fracturing fluid.

Summary Corrosion inhibitors are widely used to control corrosion under the sweet and sour environments in the oil and gas industry. More effective and environmentally friendly corrosion inhibitors need to be developed. This paper studies a new gemini imidazoline (GIM) corrosion inhibitor, in which two hydrocarbon chains and two head groups are linked by a rigid spacer. The GIM was synthesized through the reaction of oleic acid with triethylene tetramine at 2:1 molar ratio. The performance of the GIM on inhibition of carbon dioxide (CO2) corrosion was evaluated by linear polarization resistance in sparged-beaker testing. Rotating-wheel testing was performed to evaluate the film persistency of the test inhibitors. The results showed that corrosion inhibition of the GIM was more effective at lower concentration than that of conventional imidazoline. The mixture of GIM and fatty acid also showed better film persistency than conventional imidazoline. The emulsion tendency of the GIM was less than that of conventional imidazoline. The mechanism of the highly effective GIM was studied. It showed that GIM has much-higher surface activity than conventional imidazoline. The critical micelle concentration (CMC) of GIM is several times lower than that of conventional imidazoline. Hence, the new GIM corrosion inhibitor and its mixture give more-effective corrosion inhibition at low concentration; there is also a lesser environmental effect.

The phase behaviors of dihydrogenated tallowalkyl dimethyl ammonium chloride (DHTDMAC), water and different hydrocarbons were studied. Addition of different hydrocarbons to DHTDMAC and water system formed rich aggregates, including two liquid crystal aggregates and water in oil microemulsion. The polarity of hydrocarbon affects stability and phase behavior of hydrocarbon–DHTDMAC–water. The polar hydrocarbons, cyclohexane and benzene stabilize the phase structure. Interaction of different hydrocarbon molecules with liquid crystal phase was studied by the small angle X-ray diffraction. The results indicate that the variable hydrocarbon and water fraction penetrate into surfactant association structure with the different hydrocarbons, which affects the stability and Kraft point of surfactant aggregates. Less water penetrates into lamellar liquid crystal where more oil penetrates into the same area, which stabilizes the aggregate's phase structure.

A non-equilibrium model for adsorption process of single ionic species onto solid adsorbent has been proposed within the framework of irreversible thermodynamics. Based on Ziegler’s principle of maximal rate of dissipation and combining mass balance equation of ionic species, a theoretical formulation of general description for non-equilibrium adsorption was obtained. Fatherly, the dispersion-type energy functions included two Helmholtz free energy and one dissipation rate density were constructed by complementary error function, which introduced into the general form of non-equilibrium model to achieve the specific form. The predicted results of the presented model were compared with the tested kinetics of adsorption processes of Pb2+ and Cd2+ onto Beidellite, which provided a better agreement with the experimental data.

Many functional materials have been used in oil and gas industries. Special materials were needed for to withstand the high temperature and pressure harsh environment of oil and gas reservoir. Nanotechnologies have the potential to introduce revolutionary changes of materials used in the areas of the oil and gas industries. This paper gives an overview of the nanotechnology application for enhanced oil recovery, fracturing fluids, flow assurance, drilling, completion and specialty composite in the oil and gas industry in the last few years. Applications of nano-materials, in the form of solid composites and functional nanoparticle-fluid in these areas are reviewed. The future challenges of nanotech-based solutions for the petroleum industry are also discussed.

The normal stiffness between teeth is an important parameter to design an effective force controller of chewing robot. The normal stiffness analysis of antagonistic molars with crown prosthesis in chewing robot was carried out. Right first antagonistic molars of the dental model were modelled by raster scanning, 3D reconstruction, and separation. Then an occlusal kinematics analysis was made in Occlusal Fingerprint Analyser software, which turned an initial statistical chewing trajectory into an optimized chewing trajectory matching the teeth morphology. Next, normal direction along the optimized chewing trajectory was defined for calculating the normal force by the dynamic finite element method. Finally, the normal stiffness at the feature time point was calculated by data processing. The result showed that in the intrusive and excursive phase, the normal stiffness kept 2.5–7.5 MPa, and in the medial phase, it increased to 47.5–60.0 MPa.

Poly-silicic-cation coagulants (PSiCs) with different pH were prepared by synchronous-polymerization. The characteristics and coagulation performances of the coagulants were analyzed. The results show that the crystal, structure and morphology of PSiC are influenced by pH and the optimal preparation pH is 1.5. The crystal analysis shows that some new complex compounds are formed in PSiC. The polymerization form and complexation degree of PSiC with pH of 1.5 are better than at other pH values. The structure and morphology analyses imply that the contents of ionic polymerized bonds, high polymers and irregular PSiC units decrease, and cross-copolymerization of Fe (III) and Al (III) hydroxyl polymers is weakened when pH is too low or too high. Coagulation experiments also indicate that the PSiC with pH value of 1.5 exhibits better coagulation performance in removing turbidity, COD and chroma of paper mill wastewater.

Phenol and its derivatives are common organic contaminants, which are known to have adverse impacts on humans, thus the detection of phenol is very important. Herein, an amperometric sensor was fabricated based on electrochemical polymerization of zincon onto a carbon paste electrode (CPE) surface. The cyclic voltammogram of phenol on the sensor exhibited a well-defined anodic peak at 0.640 V in 0.1 mol L−1 phosphate buffer solution (PBS, pH 7.0). The sensor was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Meanwhile, the influence of various parameters such as pH and scan rate on the analytical performance of the sensor was evaluated. Under the optimized conditions, the oxidation peak current was proportional to the phenol concentration change in the range from 21 μmol L−1 to 292 μmol L−1 and 357 μmol L−1 to 922 μmol L−1 with correlation coefficients of 0.9911 and 0.9966, respectively. The limit of detection was estimated to be 9 × 10−6 mol L−1 (S/N = 3). Furthermore, the fabricated sensor was successfully applied to determine phenol in oilfield wastewater.

The temporomandibular joint (TMJ) is a complex bilateral articulation, and its movements are a combination of hinge movement and gliding movement guided by its articular surfaces. A masticatory robot with higher kinematic pairs (HKPs) simulating TMJ behavior is introduced. Kinematic equations of the HKPs are derived based on three-dimensional kinematics of rigid bodies and differential geometry. Position, velocity and acceleration of the contact points are analyzed according to the characteristics that the condyle movement involves rotation and translation simultaneously. Given a target trajectory, the position of contact point, velocity and acceleration relative to articular surface of fossa are obtained by simulation based on the contact kinematics of the HKPs. The result provides a useful tool for studying kinematics behavior of human TMJs.

N,N,N-Trimethyl chitosan (TMC) with 40% quaternization was used as a vector for small interfering RNA (siRNA) delivery. Nano-sized complexes were formed in water by mixing siRNA with TMC; the smallest particle sizes were obtained at a N/P ratio of 10. The complexes had a positive surface charge that increased with increases in the N/P ratio and leveled off at +20 mV with N/P ratios > 10. The majority of particles had a diameter 10, the binding efficiency of TMC with siRNA was >90%. In 25% fetal bovine serum, the TMC/siRNA complexes with N/P ratios of 10 and 20 were intact for 12 and 48 h, respectively. TMC/siRNA complexes with an N/P ratio > 5 efficiently entered the human embryonic kidney (HEK) 293 cells and trapped initially in the lysosomes, which could then relocate in the cytoplasm. Gene silencing, tested by using enhanced green fluorescent protein (EGFP), was reduced to ~60% by the complexes with N/P ratios of 10 and 20. Specific silencing was confirmed by dose dependency and nonsilencing effect of sequence-mismatch siRNA. No significant cytotoxicity was detected for the TMC/siRNA complexes. In this study, the influence of the N/P ratio on TMC/siRNA complexes was systematically investigated and TMC was found to be an effective vector for siRNA delivery using optimized formulations.

Rheological properties of wormlike micelle solutions of zwitterionic surfactant were studied as a function of cosurfactant, organic salt, and solvents at high temperature. Addition of cosurfactant and organic salt increases the viscoelasticity at high temperature. Addition of isopropanol as solvent shifts the maximum viscosity of wormlike micelle to lower temperature. Addition of propylene glycol as solvent has less effect on the viscoelasticity of the wormlike micelle solution. An analysis based on the polarity of the solvent and phase behavior in concentrate region explains the effect of solvents on worm-like micelle.

A numerical model for jack-up penetration process was built based on the geotechnical centrifugal model test by Hossain M S. The soil flow mechanism and the relationship between penetration depth and penetration resistance were analyzed based on numerical results. The distribution pattern of the spudcan bottom pressure was investigated for the first time. The numerical results are in good agreement with Hossain M S experimental results, which indicates that the proposed model is reliable. The numerical results show that, soil flow failures, such as surface and interface swelling, cavity formation, and soil backflow, happen in the penetration process; the lower the strength ratio between stiff and soft clay is, the smaller the volume of stiff block under the spudcan is, the more continuous and uniform the stiff clay distribution above the spudcan is, and the deeper the cavity is. The higher the soil unit weight, the more the backflow stiff soil above the spudcan and the shallower the cavity. The soil unit weight has almost no effect on the stiff soil shape and volume under spudcan. The higher the strength ratio between stiff and soft clay or the lower the soil unit weight is, the more likely the punch-through occurs. The bottom pressure first increase, then decrease, and increase sharply, from inside to outside, which proves that the linear assumption of the spudcan bottom pressure in ‘Rules for Mobile Offshore Drilling Units’ does not conform to the fact. Key words: jack-up, penetration process, numerical model, spudcan bearing capacity, spudcan bottom pressure

Quasi-static numerical model of jack-up spudcan penetration in layered sandy soil was presented in this paper, based on explicit procedure. Three different methods, such as Lagrangian analysis, Lagrangian analysis with distortion control and Lagrangian-Eulerian analysis, were used to control soil negative element volumes or other excessive distortion. The results showed that, reasonable and stable numerical results could be solved by Lagrangian-Eulerian analysis. The magnitude of plastic strain, however, decreases at first and then increases to the maximum.