Development of Reformative Surgery Method Using Partial Freezing for the Liver

2006 ◽  
Vol 128 (6) ◽  
pp. 862-866
Author(s):  
M. Takahashi ◽  
S. Nomura ◽  
M. Jindai ◽  
S. Shibata ◽  
X. Zhu ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Degrees Of Freedom ◽  
Operation Time ◽  
Basic Research ◽  
Freezing Temperature ◽  
The Finite Element Method ◽  
Porcine Liver ◽  
Liver Sample ◽  
Peltier Module ◽  
Increment Rate

To minimize surgical stresses including blood loss and operation time to the patients during hepatic resection, we studied the feasibility of a combination of a partial liver freezing technique and shape-memory alloy, which also enables a free-designed resection curve. In this surgical procedure, the region surrounding a tumor in the liver is frozen to excise and prevent hemorrhage. The liver was frozen by a Peltier module. The effects of cooling rate and freezing temperature on the excision force that arise between a scalpel and the liver are carried out experimentally as a basic research for partial freezing surgical procedures. A porcine liver was used as a liver sample. The physical properties were estimated by using the finite element method based on the heat transfer characteristics of the liver. Isolation of the liver was conducted using a scalpel attached to the end-effector of a 3 degrees of freedom robot. In the experiments, the minimum excision force was obtained at a temperature between 272K and 275K; therefore, it is preferable that the liver be excised within this temperature range. Lowering of the cooling rate decreases the excision force even if the temperature of the liver remains unchanged. The lower the temperature of the liver is, the larger the increment rate of excision force is with regard to the cooling rate.

scholarly journals A Finite Element Approach to the Analysis of Rotating Bladed-Disk Assemblies Coupled With Flexible Shaft

1994 ◽  
Author(s):  
Wen Zhang ◽  
Wenliang Wang ◽  
Hao Wang ◽  
Jiong Tang
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Coupled System ◽  
Equation Of Motion ◽  
Coupled Systems ◽  
The Finite Element Method ◽  
Bladed Disk ◽  
Modal Synthesis ◽  
Element Approach ◽  
Final Equation

A method for dynamic analysis of flexible bladed-disk/shaft coupled systems is presented in this paper. Being independant substructures first, the rigid-disk/shaft and each of the bladed-disk assemblies are analyzed separately in a centrifugal force field by means of the finite element method. Then through a modal synthesis approach the equation of motion for the integral system is derived. In the vibration analysis of the rotating bladed-disk substructure, the geometrically nonlinear deformation is taken into account and the rotationally periodic symmetry is utilized to condense the degrees of freedom into one sector. The final equation of motion for the coupled system involves the degrees of freedom of the shaft and those of only one sector of each of the bladed-disks, thereby reducing the computer storage. Some computational and experimental results are given.

scholarly journals Kane’s Formalism Used to the Vibration Analysis of a Wind Water Pump

Symmetry ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1030
Author(s):  
Gabriel Leonard Mitu ◽  
Eliza Chircan ◽  
Maria Luminita Scutaru ◽  
Sorin Vlase
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Elastic Element ◽  
Vibration Analysis ◽  
Degrees Of Freedom ◽  
Transmission Mechanism ◽  
Water Pump ◽  
The Finite Element Method ◽  
Lagrange’S Equation ◽  
Elastic Elements

The paper uses Kane’s formalism to study two degrees of freedom (DOF) mechanisms with elastic elements = employed in a wind water pump. This formalism represents an alternative, in our opinion, that is simpler and more economical to Lagrange’s equation, used mainly by researchers in this type of application. In the problems where the finite element method (FEM) is applied, Kane’s equations were not used at all. The automated computation causes it to be reconsidered in the case of mechanical systems with a high DOF. Analyzing the planar transmission mechanism, these equations were applied for the study of an elastic element. An analysis was then made of the results obtained for this type of water pump. The matrices coefficients of the obtained equations were symmetric or skew-symmetric.

Rotor Dynamic Analysis of an Eccentric Hydropower Generator With Damper Winding for Reactive Load

2007 ◽  
Vol 74 (6) ◽  
pp. 1178-1186 ◽  
Author(s):  
Martin Karlsson ◽  
Jan-Olov Aidanpää ◽  
Richard Perers ◽  
Mats Leijon
Keyword(s):  
Degrees Of Freedom ◽  
Reactive Power ◽  
Tangential Component ◽  
Design Parameters ◽  
The Finite Element Method ◽  
Unbalanced Magnetic Pull ◽  
Hydroelectric Generator ◽  
Electromagnetic Models ◽  
The Stability ◽  
Damper Winding

Asymmetry in the magnetic circuit, around the air gap circumference, in a hydroelectric generator will give rise to a unbalanced magnetic pull. In this paper, a hydropower rotor system is modeled and the influence of electro-mechanical forces due to overexcitation is analyzed. The active power has been kept constant and the rotor excitation has been changed in order to vary the output of reactive power. The electromagnetic field is solved with the finite element method. Two electromagnetic models are compared: one with and one without damper winding. The mechanical model of the generator consists of a four degrees of freedom rigid disk connected to an elastic shaft supported by two bearings with linear properties. It has been found that the unbalanced magnetic pull slightly increases for reactive loads resulting in a decrease of natural frequencies and an increase of unbalance response. When the damper winding is included, the magnetic pull will decrease compared to the model without damper winding, and the pull force has two components: one radial and one tangential. The tangential component can influence the stability of the mechanical system for a range of design parameters.

Sea Motion Simulation, Very Low Frequency Vibration, and Motion Sickness

1976 ◽  
Vol 20 (20) ◽  
pp. 462-462
Author(s):  
Michael E. McCauley
Keyword(s):  
Motion Sickness ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Vertical Motion ◽  
Basic Research ◽  
Future Research ◽  
Naval Research ◽  
Low Frequency Vibration ◽  
Office Of Naval Research ◽  
Linear Oscillation

The office of Naval Research/Human Factors Research (ONR/HFR) Motion Generator was designed with three degrees of freedom (heave, pitch, and roll) to simulate the motion of an air-sea craft in varying ocean conditions through Sea State 5. Recent upgrading of the device has provided the capability for simulating the motion of advanced design sea craft as well as certain aspects of vertical motion common to land, sea, and air vehicles. Since 1968, the simulator has been used for investigation of the following topics: (1) basic research to provide equations for the prediction of motion sickness incidence based on parameters of vertical linear oscillation, (2) crew performance during simulated motion of two types of proposed naval vessels, and (3) evaluation of the efficacy of antimotion sickness medications in alleviating the symptoms of motion sickness. This simulator provides the opportunity for future research on the effects of motion on physiological and psychological processes as well as task performance.

42 COMPARISON OF COOLING RATES IN OOCYTE VITRIFICATION SYSTEMS USING A NUMERICAL SIMULATION

2012 ◽  
Vol 24 (1) ◽  
pp. 133 ◽  
Author(s):  
M. Sansinena ◽  
M. V. Santos ◽  
N. Zaritzky ◽  
J. Chirife
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cooling Rate ◽  
External Heat ◽  
Experimental Comparison ◽  
The Finite Element Method ◽  
Cooling Rates ◽  
External Heat Transfer

Interest in oocyte cryopreservation has increased due to the application of assisted reproductive technologies and the need for the establishment of ova/gene banks worldwide. In order to maintain cell viability, biological functions must be halted, inducing a suspended animation state by cooling it into a solid phase. Compared to cryopreservation of male gametes, oocytes represent a greater challenge due to their low surface area:volume. Vitrification, the solidification into an amorphous, glassy state while maintaining absence of intra- and extracellular ice crystals, requires high concentrations of cryoprotectants and extremely rapid cooling rates. Several vitrification devices such as open pulled straws (OPS), ultra fine pipette tips, nylon loops and polyethylene films have been introduced to manipulate minimal volumes and achieve high cooling rates. However, experimental comparison of cooling rates presents difficulties mainly because of the reduced size of these systems. To circumvent this limitation, a numerical simulation of cooling rates of various vitrification systems immersed in liquid nitrogen was conducted, solving the non-stationary heat transfer partial differential equation using the finite element method. Three external heat transfer coefficients (h = 200, 1000 and 2000 W m–2 K) were considered. The Cryotip® and OPS were approached as 2 concentric finite cylinders; differential equations representing heat transfer in cylindrical coordinates were described considering radial and axial coordinates and were numerically solved as a 1-dimensional heat conduction problem in an infinite cylinder. The Cryoloop® was approximated as a 1-dimensional heat flow system in Cartesian coordinates and Cryotop® was numerically described as an irregular bi-dimensional axial-symmetric problem. All differential equations were numerically solved using the finite element method in COMSOL Multiphysics 3.4. The domain was discretized in triangular (Cryotip®, OPS and Cryotop®) and linear elements (Cryoloop®) in order to obtain accurate numerical approximations. In each case, the warmest point of the system was identified to determine the time-temperature curve that allows the evaluation of the slowest cooling rate (worst condition). Results indicate the nylon loop (Cryoloop®) is the most efficient heat transfer system analysed, with a predicted cooling rate of 180 000°C min–1 for an external heat transfer coefficient h = 1000 W m–2 K when cooling from 20 to –130°C; in contrast, the pipette tips (Miniflex® showed the lowest performance with a cooling rate of 6164°C min–1 at same value of external heat transfer coefficient. Predicted cooling rates of OPS and Cryotop® (polyethylene film) were 40 909 and 37 500°C min–1, respectively for the same heat transfer coefficient. It can be concluded that in oocyte cryopreservation systems, in which experimental comparison of cooling rates presents difficulties due to the reduced size of the vitrification devices, the numerical simulations and the analysis of the predicted thermal histories could contribute to determine the performance of the different techniques.

Conformational Entropy as a Means to Control the Behavior of Poly(diketonenamine) Vitrimers In and Out of Equilibrium

2019 ◽  
Author(s):  
Changfei He ◽  
Peter Christensen ◽  
Trevor Seguin ◽  
Brandon Wood ◽  
Kristin Persson ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Characteristic Time ◽  
Degrees Of Freedom ◽  
Freezing Temperature ◽  
Thermomechanical Behavior ◽  
Polymer Chains ◽  
Network Density ◽  
Conformational Entropy ◽  
Conformational Degrees Of Freedom

Here we show how to control the thermomechanical behavior of vitrimers, both in and out of equilibrium, by incorporating into the dynamic covalent network linear polymer segments varying in both molecular weight (MW = 0–12 kg mol–1) and conformational degrees of freedom. While increasing MW of linear segments predictably yields a lower storage modulus (E’) at the rubbery plateau after softening above the glass transition (Tg), due to the lower network density, we further find that both Tg and the characteristic time (t*) of stress-relaxation when deformed are independently governed by the conformational entropy of the embodied linear segments. We also find that activation energies (Ea) for vitrimer bond exchange in the solid-state are lower, by as much as 19 kJ mol−1, for networks incorporating flexible chains, and that the network’s topology freezing temperature (Tv) decreases with increasing MW of flexible linear segments, but increases with increasing MW of stiff linear segments. Therefore, the dynamics of vitrimer reconfigurability are influenced not only by the energetics of associative bond exchange for a given network density, but also foundationally by the entropy of polymer chains within the network.

Improvement of a Reduced Torsional Model by Means of Parameter Identification

1989 ◽  
Vol 111 (1) ◽  
pp. 17-26 ◽  
Author(s):  
P. Schwibinger ◽  
R. Nordmann
Keyword(s):  
Finite Element ◽  
Mechanical Model ◽  
Degrees Of Freedom ◽  
Short Circuit ◽  
Original System ◽  
Element Model ◽  
The Finite Element Method ◽  
System A ◽  
Reduction Methods ◽  
Short Circuits

Turbogenerator sets in operation may be excited to transient torsional vibrations by dynamic electrical moments at the generator due to short-circuits or faulty synchronization. For the solution of the torsional vibration problem it is essential to find an appropriate torsional model of the original system. A common approach is to model the torsional system finely by the finite element method which normally results in a very accurate mechanical model with many degrees of freedom (DOF). However for some applications it is desirable to have a torsional model with a reduced number of DOF which reproduces the original system exactly only in the lower eigenfrequencies and modes. This paper describes a method which allows finding a most accurate reduced torsional model with discrete masses and springs from a finite element model with many DOF. The results for the eigenfrequencies, the modes, and internal moments due to a short-circuit excitation of a 600 MW turbogenerator set are presented. They are compared with other reduction methods.

Liquid Chromatographic Determination of Aflatoxicol in Porcine Liver

1987 ◽  
Vol 70 (3) ◽  
pp. 475-478
Author(s):  
Krystyna Tyczkowska ◽  
James E Hutchins ◽  
Winston M Hagler
Keyword(s):  
Limit Of Detection ◽  
Chromatographic Determination ◽  
Porcine Liver ◽  
Liver Sample ◽  
Aqueous Fraction ◽  
Silica Cartridge ◽  
Liquid Chromatographic Determination ◽  
Phase Liquid ◽  
Liquid Chromatographic

Abstract A liquid chromatographic (LC) method for determination of aflatoxicol in porcine liver was developed. Liver sample is homogenized with water, diluted with saturated Na2S04 solution, and extracted with acetone. After filtration, less polar interferences are removed by partition with isooctane. Aflatoxicol in the aqueous fraction is partitioned into CHC13. The extract is dried over anhydrous Na2S04 and evaporated nearly to dryness at 35°C under a gentle flow of dry filtered air or nitrogen. Residue is dissolved in CHCl3-hexane and applied to a hexane-activated silica cartridge. The cartridge is washed with hexane-CHClj, then aflatoxicol is eluted with CHCl3-acetone. Purified extract is evaporated to dryness, dissolved in methanol, and analyzed by C18 reverse phase liquid chromatography using a water- CHjCN-acetic acid mobile phase and fluorescence detection. Recovery of aflatoxicol from spiked liver samples at levels ranging from 0.25 to 4.0 ng aflatoxicol/g wet tissue averaged 92% with a limit of detection of about 0.1 ng aflatoxicol/g liver.

Spray Performances and Cryogenic Characteristics of C02 Snow under Cryosurgery Guided by Endoscopic

2014 ◽  
Vol 30 (3) ◽  
pp. 247-253
Author(s):  
T.-C. Lin ◽  
Y.-J. Shen ◽  
M.-R. Wang
Keyword(s):  
Cooling Rate ◽  
Design Parameter ◽  
Injection Pressure ◽  
Operation Time ◽  
Conversion Ratio ◽  
Main Flow ◽  
Cylinder Pressure ◽  
Bypass Flow ◽  
Impact Area ◽  
Effective Design

ABSTRACTThis research experimentally investigated effects of injection pressure, formation chamber and bypass flow on spray performances and cryogenic characteristics of CO2 snow under cryosurgery guided by endoscopic. Results show that CO2 snow has a superior freezing capability in the application of cryosurgery. The length of formation chamber is an effective design parameter to control spray performances and cryogenic characteristics. Increase in the length of formation chamber can increase snow size and conversion ratio, as well as the cooling rate and impact area of the tissue. Thus, it is suitable for the application on wider range nidus. Moreover, the bypass flow can efficiently modulate the cooling effect of the main flow with CO2 snow particles, and extend the operation time of cryosurgery. The experimental results also show that decrease the cylinder pressure, decrease the length of formation chamber, and increase the diameter of bypass apertures can slow down the flying velocity of CO2 snow which are effective methods to control the jet velocity and prevent the risk of penetration.

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