A Low-Cost Wireless Bite Force Measurement Device

Assessing maximum voluntary bite force is important to characterize the functional state of the masticatory system. Due to several factors affecting the estimation of the maximum bite force, a unique solution combining desirable features such as reliability, accuracy, precision, usability, and comfort is not available. The aim of the present study was to develop a low-cost bite force measurement device allowing for subject-specific customization, comfortable bite force expression, and reliable force estimation over time. The device was realized using an inexpensive load cell, two 3D printed ergonomic forks hosting reusable subject-specific silicone molds, a read-out system based on a low-cost microcontroller, and a wireless link to a personal computer. A simple model was used to estimate bite force taking into account individual morphology and device placement in the mouth. Measurement reliability, accuracy, and precision were assessed on a calibration dataset. A validation procedure on healthy participants was performed to assess the repeatability of the measurements over multiple repetitions and sessions. A 2% precision and 2% accuracy were achieved on measurements of forces in the physiological range of adult bite forces. Multiple recordings on healthy participants demonstrated good repeatability (coefficient of variation 11%) with no significant effect of repetition and session. The novel device provides an affordable and reliable solution for assessing maximum bite force that can be easily used to perform clinical evaluations in single sessions or in longitudinal studies.     

Experimental Investigation of the Tensile Behavior of Selected Tire Cords Using Novel Testing Equipment

Aramid and polyamide cords are used in a wide range of applications, particularly in the automotive industry (tire reinforcement) and textile industry for military and fireguard purposes. The problem of the reliable experimental study of tensile behavior of synthetic cords is considered in this paper. In the available standards for synthetic cord testing, particularly ASTM D 885-03, the tensile test must result with the cord damage in the middle of gauge length, and the cords should be fixed in the machine clamps. The trial test gave damage near the clamps. We propose a novel testing stage mounted in the testing machine clamps to achieve the uniform tensile stress distribution in the gauge length of the measured cords. The results of the deformations were measured in two ways: using testing machine head displacement and a videoextensometer. Stress curves of four distinguished cords were evaluated and compared. The second method allowed to acquire results differing from the manufacturers’ data from 0.7% to 21.5%, which allowed for the conclusion that the designed test stand allows for obtaining reliable results for stretched cords.     

Study on Milling Force and Surface Quality during Slot Milling of Plain-Woven CFRP with PCD Tools

Carbon-fiber-reinforced polymers (CFRPs) have been widely used in many industrial fields, such as automobile, aerospace and so on, because of their excellent mechanical properties. However, due to their anisotropy and inhomogeneity, machining CFRPs is a great challenge. In this paper, the slot milling of a plain-woven CFRP with PCD tools is carried out, and the effects of cutting parameters and tool rake angle on cutting force and surface roughness are studied. The results show that the 4° rake angle PCD tool has smaller cutting force than the 0° rake angle PCD tool, but the effect of rake angle on surface roughness is not significant. The concept of equivalent cutting area is introduced to study the variation law of cutting force and surface roughness. It is found that the cutting force and surface roughness increase with the increase in equivalent cutting area, and decrease with the decrease in equivalent cutting area. The removal mechanism of surface materials under different equivalent cutting areas is different, which leads to the difference in surface roughness. Finally, the causes of delamination on the top layer after milling are explained.     

Analytical Model for Early Design Stage of Cable-Stayed Suspension Bridges Based on Hellinger–Reissner Variational Method

The cable-stayed suspension bridge is one type of bridge that has been increasingly applied to bridge engineering, especially in cross-sea projects. However, the complex combined system of this type of bridge makes it quite difficult for researchers to make a quick decision of the parameter values during the design stage. The Hellinger–Reissner method is applied here to analyze the deformation and force of the structural members in the bridge. The advantage of this method is that the solving of deformation and force is independent of each other, which would enhance the accuracy of the final results. Different load conditions are also considered in the analysis. The results from the present method are compared with test results and finite element analysis, and show good agreements. It implies that the Hellinger–Reissner is a comparatively more efficient method to help designers choose the key parameters for cable-stayed suspension bridges.     

电针心经对心肌缺血性家兔心力环面积的影响

以心力环面积为指标,静脉滴注垂体后叶素造成家兔心肌缺血动物模型,结果表明,电针心经地心脏功能的调节作用比电针肺经显著,有相对特异性,说明心经作为一条经脉,与心脏机能活动有密切关系。     

Investigation of Technological and Load Intensity Parameters of the Finishing Process of Materials on Equipment with Tools Translational Kinematics

The regularities of the formation of the resulting raster tool trajectories based on Lissajous figures for the lapping process of planes are established. This makes it possible to maximize the cutting ability of the tool, which contributes to its more uniform wear and increased productivity and processing quality. Optimal parameters of productivity and roughness of the treated surface during lapping of zirconium ceramics are achieved through the use of ASM paste 28/20 µm. Based on Preston’s hypothesis, an exponential dependence of the change in the contact area during the lapping of planes of different initial shape of the macrorelief is obtained. The obtained theoretical and practical results of the study of the process of flat lapping with constant and variable clamping force of the treated surface to the surface of the tool. The influence of the force factor on the formation of the surface in the process of abrasive lapping has been established. Studies have been carried out and the main technological recommendations of precision surface treatment of workpieces based on hard, brittle ceramic material and bronze samples on equipment with a raster trajectory of the tool movement are presented. The optimal pressure value when processing ceramics should be considered 203–270 kPa (2.1–2.8 kg/cm²).     

Experimental Study on Self-Centering Performance of the SMA Fiber Reinforced ECC Composite Beam

The combination of superelastic shape memory alloy fibers and ECC materials can form a new SMA fiber reinforced ECC composite material (SMAF-ECC) with good self-centering performance. In order to study the self-centering performance of the new composite material, 6 groups of pre-notch beam specimens were made for three-point bending cyclic loading tests, and the failure phenomenon, hysteresis curve, self-centering effect and influencing factors of the specimens were analyzed. The research results show that when the SMA fibers are effectively anchored in the ECC matrix, the SMA fibers can exert the superelastic properties to provide the ECC beams with recoverying force, and realize the crack self-closure and deflection self-recovery function for the beams, with the minimum residual crack width and deflection is only 0.9 mm and 1.3 mm respectively. Increasing fiber content can cause a small increase in the self-centering ability of the beams. However, only when the fiber diameter is appropriate, better self-centering effect can be achieved, but the difference caused by fiber diameter in the test was only 5%. SMA Fiber end forms have significant influence on self-centering performance. The knotted end beam can get a more than 70% self-centering ratio, while the straight end beams and bended end beams have no self-centering ability. The research results provide important reference for the research and application of this new self-centering materials and their structures.     

Membrane technology for optimizing process optimization of small bioactive compounds in Mailuoning Injection factory effluene北大核心CSCD

Objective: To enrich small bioactive compounds from Mailuoning Injection factory effluene by polyether sulfoxide hollow fiber membrane. Methods: The retention rate of the common polymer (protein, tannin, starch, and pectin) and the permeability of the small molecule pharmacodynamic substance chlorogenic acid were the indicators, and the stop time and membrane type in ultrafiltration process were optimized. The temperature, pressure, and feed rate were investigated to determine the influence degree of each factor on the permeability and retention rate, and then the optimum process parameters of the ultrafiltration membrane process were optimized by using Box-Behnken design-response surface method. Results: The sequence of common polymer retention rate from high to low is: the influencing factor A (temperature), B (pressure), C (feed rate), and there was a negative correlation with the temperature. For the chlorogenic acid transmission rate, the influencing factor A (temperature) was larger than B (pressure), and C (feed rate) was lowest. There was a “∩” relationship between chlorogenic acid permeability and pressure at a certain temperature and rate. The results of optimized process were as follows: liquid temperature was 35 ℃, feed rate was 262 mL/min, and membrane pressure was 15.0 psi (1 psi = 6.895 kPa). The chlorogenic acid transmission rate was (91.470 ± 0.988)%, and polymer retention rate was (80.080 ± 2.296)%. The comprehensive score was (85.780 ± 1.641)% and RSD was 0.46%. There was a small difference between the two processes. Conclusion: Hollow fiber membrane, which is a sustainable and green resource utilization, has a good permeability for small bioactive compounds in wastewater, and has excellent retaining effect on common macromolecules. © 2019, Editorial Office of Chinese Traditional and Herbal Drugs. All right reserved.