Light-Driven Linear Inchworm Motor Based on Liquid Crystal Elastomer Actuators Fabricated with Rubbing Overwriting

Linear displacement is used for positioning and scanning, e.g., in robotics at different scales or in—scientific instrumentation. Most linear motors are either powered by rotary drives or are driven directly by pressure, electromagnetic forces or a shape change in a medium, such as piezoelectrics or shape-memory materials. Here, we present a centimeter-scale light-powered linear inchworm motor, driven by two liquid crystal elastomer (LCE) accordion-like actuators. The rubbing overwriting technique was used to fabricate the LCE actuators, made of elastomer film with patterned alignment. In the linear motor, a scanned green laser beam induces a sequence of travelling deformations in a pair of actuators that move a gripper, which couples to a shaft via friction moving it with an average speed in the order of millimeters per second. The prototype linear motor demonstrates how LCE light-driven actuators with a limited stroke can be used to drive more complex mechanisms, where large displacements can be achieved, defined only by the technical constrains (the shaft length in our case), and not by the limited strain of the material. Inchworm motors driven by LCE actuators may be scaled down to sub-millimeter size and can be used in applications where remote control and power supply with light, either delivered in free space beams or via fibers, is an advantage.

Temperature profile and residual heat of monopolar laparoscopic and endoscopic dissection instruments

Background Endoscopic and laparoscopic electrosurgical devices (ED) are of great importance in modern medicine but can cause adverse events such as tissue injuries and burns from residual heat. While laparoscopic tools are well investigated, detailed insights about the temperature profile of endoscopic knives are lacking. Our aim is to investigate the temperature and the residual heat of laparoscopic and endoscopic monopolar instruments to increase the safety in handling ED. Methods An infrared camera was used to measure the temperature of laparoscopic and endoscopic instruments during energy application and to determine the cooling time to below 50 °C at a porcine stomach. Different power levels and cutting intervals were studied to investigate their impact on the temperature profile. Results During activation, the laparoscopic hook exceeded 120 °C regularly for an up to 10 mm shaft length. With regards to endoknives, only the Dual Tip Knife showed a shaft temperature of above 50 °C. The residual heat of the laparoscopic hook remained above 50 °C for at least 15 s after activation. Endoknives cooled to below 50 °C in 4 s. A higher power level and longer cutting duration significantly increased the shaft temperature and prolonged the cooling time (p < 0.001). Conclusion Residual heat and maximum temperature during energy application depend strongly on the chosen effect and cutting duration. To avoid potential injuries, the user should not touch any tissue with the laparoscopic hook for at least 15 s and with the endoknives for at least 4 s after energy application. As the shaft also heats up to over 120 °C, the user should be careful to avoid tissue contact during activation with the shaft. These results should be strongly considered for safety reasons when handling monopolar ED.

Vibration Analysis of the Drivetrain in Dependence on the Type of Gearbox Suspension Bushing

In the vast majority of technical applications, there is a necessity to transmit the torque from drive to driven machine together with the demand to overcome great distance between given devices. One of the solutions of this problem is the use of a cardan shaft. Operations of connecting shaft and drivetrain are accompanied by oscillations negatively influencing the driver comfort. Main subject of this article is the measurement of vibrations on different parts of a heavy truck and its evaluation by FFT analysis. Measurements are performed with two kinds of suspension bushing which are compared with to each other. Based on the previous measuring, influence of cardan shaft length was also investigated. First of all, dependency on the length of the cardan shaft on deflection angles for V arrangement was evaluated by analytical method. The theoretical introduction is followed by research of eigen frequency depending on the length of the cardan shaft. The results obtained by modal analysis in FEM are verified by experimental modal analysis [1].

Effect of Coupled Torsional and Transverse Vibrations of the Marine Propulsion Shaft System

In this study, the coupled torsional–transverse vibration of a propeller shaft system owing to the misalignment caused by the shaft rotation was investigated. The proposed numerical model is based on the modified version of the Jeffcott rotor model. The equation of motion describing the harmonic vibrations of the system was obtained using the Euler–Lagrange equations for the associated energy functional. Experiments considering different rotation speeds and axial loads acting on the propulsion shaft system were performed to verify the numerical model. The effects of system parameters such as shaft length and diameter, stiffness and damping coefficients, and cross-section eccentricity were also studied. The cross-section eccentricity increased the displacement response, yet coupled vibrations were not initially observed. With the increase in the eccentricity, the interaction between two vibration modes became apparent, and the agreement between numerical predictions and experimental measurements improved. Given the results, the modified version of the Jeffcott rotor model can represent the coupled torsional–transverse vibration of propulsion shaft systems.

Natural Frequency Analysis of a Jeffcott Rotor Having Stepped Shaft

The Rotating shafts are mechanical elements used to transmit power or motion. A shaft with a step or steps is widely used instead of a shaft with a fixed (non-variable) diameter when operating at high speeds. The aim of this research is to study the effect of the step amount and its location in the shaft on the natural frequencies of the Jeffcott rotor model. Analytical methods are used to find an approximate formulation to obtain the natural frequencies of the Jeffcott rotor model neglecting the shaft mass. Lagrange equations are used to develop dynamic equations assuming elastic shaft with steps carrying a disk. The finite element method by using ANSYS is used to validate and compare the results obtained in the analytical method. The results obtained analytically and numerically were compatible and in good agreement. In addition, some parameters such as the step amount and the stepped shaft length are changed to check its effects on the natural frequencies. the results showed that the natural frequencies increase with an increase in the amount and length of the stepped part, while they decrease the closer the disc position to the center.

Працездатність підшипників ковзання як опор шестерень основного паливного насосу ГТД

The paper is about the performance capability of the journal bearings as a support of the fuel gear pump for gas turbine engines (GTE). Supports of the external gear pump usually operate in semi-dry friction conditions, which reduces residual life and is one of the limiting factors. For this investigation, the serial gear pump was chosen with the following parameters: the number of teeth z = 14, module m = 3.8, gear-loading Р = 7800 N. The authors have studied options for a pump with an electrical and mechanical (from the rotor of the GTE) drive. The main criterion for studying the bearing capacity is the minimum thickness of the working layer of a fluid with low viscosity (kerosene). For modeling, a common theory is used based on solutions of differential equations of the viscous fluid hydrodynamics, which relate pressure, velocity, and viscous shear resistance. For technological reasons, the minimum allowable kerosene layer is limited to 5 μm. The conducted analysis considers the multi-lobe (2-, 3- and 4-lobe) bearings with different lobe orientations relative to the force vector. It was found that the 2-lobe bearing has the best load capacity (provides the largest layer of kerosene). According to the results of the previous investigation for further work, the 2-lobe bearing was chosen. The influence of load, setting gap, eccentricity, the specific radius of lobe curvature, shaft length on the bearing load capacity was analyzed. A rational type of bearing design was proposed based on the load capacity criterion (the minimum layer of working fluid). It was shown that the hydrodynamic 2-lobe bearing can be sufficiently effective for the supports of the gear fuel pumps of GTE. Based on the results of the investigation, 2 variants of the pumping unit designs were proposed. The first one for the pump driven by the gas turbine engine rotor with parameters z = 19, m = 3.3, gears width B = 34, shaft diameter DS = 48, and shaft length LS = 56 (P = 10.2kN). The second one for the electrically driven pump, z = 28, m = 1,8, B = 15, DS = 34, and LS = 41 (P = 3.8 kN). The minimum angular velocity for the pump variants is 470 and 1055 rad/s, respectively. According to the investigation results, it was proposed to conduct related studies of the working process in pumps and bearings.

Wind tunnel comparison of four VAWT configurations to test load-limiting concept and CFD validation

The article describes results of experimental wind tunnel testing of four different straight-bladed vertical axis wind turbine model configurations. The experiment tested a novel concept of vertically dividing and azimuthally shifting a turbine rotor into two parts with a specific uneven height division in order to limit cycle amplitudes and average cycle values of bending moments at the bottom of the turbine shaft to increase product lifetime, especially for industrial-scale turbines. Testing reduction effects of simultaneously including a vertical gap between turbine rotor levels, increasing shaft length but also reducing aerodynamic interaction between rotor levels, has also been performed. Experiment results have shown very significant decreases of bending moment cycle amplitudes and average cycle values, for a wide range of measured wind speeds, for dual-level turbine configurations as compared to a single-level turbine configuration. The vertical spacing between levels equal to a blade's single chord length has proven to be sufficient, on laboratory scale, to limit interaction between turbine levels in order to achieve optimal reductions of tested parameters through an operating cycle shift between two position-locked rotor levels during a turbine's expected lifetime. CFD validation of maintaining the effect on industrial scale has been conducted, confirming the initial conclusions.

Wet Modal Analyses of Various Length Coaxial Sump Pump Rotors with Acoustic-Solid Coupling

The dynamic characteristics of the rotor components were determined using a first-order modal model of the rotor components for various sump pump shaft lengths for actual working environments. By employing ANSYS-Workbench software, this paper uses a fluid-solid coupling analysis to calculate the reaction forces of the fluid on the rotor with results, which is then used in dry and wet modal analyses of the rotor parts to calculate the vibration modal characteristics with and without prestresses. The differences between the wet and dry modal characteristics were compared and investigated by ANSYS. The results show that increasing the sump pump shaft length reduces the first-order natural frequency of the prestressed rotor components. The structure also experiences stress stiffening, which is more obvious in the high-order modes. The natural frequency of the rotor in the wet mode is about 16% less than that in the dry mode for the various shaft lengths due to the added mass of the water on the surface which reduces the natural frequency. In the wet modal analysis, when the structure is in a different fluid medium, the influence of its modal distribution will also change, this is because the additional mass produced by the fluid medium of different density on the structure surface is different. Thus, the wet modal analysis of the rotor is important for more accurate dynamic analyses.

Defining Aesthetic Preferences for the Penis: A Photogrammetric and Crowdsourcing Analysis

Background Achieving an aesthetic phalloplasty result is important for patients with acquired or congenital defects of the penis, or with genital-related dysphoria. However, aside from length and girth, aesthetic proportions of the male penis have not been defined. Objectives This study aimed to determine proportions of the male penis through photogrammetric analysis of nude male photographs and to verify these proportions with a crowdsourcing-based survey. Methods Nude male photographs (n=283) were analyzed to define aesthetic proportions of the male penis. Photographs were analyzed for the position of the penis on the torso in relation to the umbilicus and for the ratio of the dorsal and ventral glans of the penis in relation to the entire shaft length. Proportions were then further studied by crowdsourcing 1,026 respondents with Amazon mechanical Turk. Results The ideal position of the penis below the umbilicus is about 55% (6/11 th) of the distance from the jugular notch to the umbilicus (measured average 53.6%, survey weighted average 58.9%). The dorsal glans of the penis is about 33% (1/3 rd) of the length of the entire shaft (measured average 32.1%, survey weighted average 37.5%). The ventral glans of the penis is about 12.5% (1/8 th) of the length of the entire shaft (measured average 12.6%, survey average 11.7%). Conclusions Measured proportions of the human penis follow exact fractions. Crowdsourcing data helped support photogrammetric analysis, with survey preferred ratios within 5% of measured ratios. With further validation, this data can aid surgeons performing phalloplasty.

Partial Threading of Pedicle Screws in a Standard Construct Increases Fatigue Life: A Biomechanical Analysis

This study proposed a pedicle screw design where the proximal 1/3 of the screw is unthreaded to improve fixation in posterior spinal surgery. This design was also expected to reduce the incidence of mechanical failure often observed when an unsupported screw length is exposed outside the vertebra in deformed or degenerated segments. The aim of this study was to evaluate the fatigue life of the novel pedicle screw design using finite element analysis and mechanical testing in a synthetic spinal construct in accordance with American Society for Testing and Materials (ASTM) F1717. The following setups were evaluated: (i) pedicle screw fully inserted into the test block (EXP-FT-01 and EXP-PU-01; full thread (FT), proximal unthread (PU)) and (ii) pedicle screw inserted but leaving an exposed shaft length of 7.6 mm (EXP-FT-02 and EXP-PU-02). Corresponding finite element models FEM-FT-01, FEM-FT-02, FEM-PU-01, and FEM-PU-02 were also constructed and subjected to the same loading conditions as the experimental groups. The results showed that under a 220 N axial load, the EXP-PU-01 group survived the full 5 million cycles, the EXP-PU-02 group failed at 4.4 million cycles on average, and both EXP-FT-01 and EXP-FT-02 groups failed after less than 1.0 million cycles on average, while the fatigue strength of the EXP-FT-02 group was the lowest at 170 N. The EXP-FT-01 and EXP-FT-02 constructs failed through fracture of the pedicle screw, but a rod fractured in the EXP-PU-02 group. In comparison to the FEM-FT-01 model, the maximum von Mises stress on the pedicle screw in the FEM-PU-01 and FEM-PU-02 models decreased by −43% and −27%, respectively. In conclusion, this study showed that having the proximal 1/3 of the pedicle screw unthreaded can reduce the risk of screw fatigue failure when used in deformed or degenerated segments.