Magnetic fluids are a kind of magnetic functional fluids, and they are stable colloidal dispersions of nano-sized magnetic particles in a carrier liquid. Magnetic fluids are available to satisfy particular applications in technological and biomedical fields. It is necessary to know basic characteristics of magnetic fluids in order to realize a wide range of applications.In this review paper, physical properties of magnetic particles, general structure of magnetic fluids, magnetization characteristics, interfacial phenomena, rheological characteristics, and some applications proposed by the author etc. are described. In particular, interfacial phenomena of magnetic fluids under magnetic fields and several micro magnetic fluid devices composed of magnetic fluid and small permanent magnet are detailed.
Solid refining agents are introduced into an inclined circular reactor of a continuous refining process together with molten iron containing impurities such as sulfur. In the course of passing through the reactor metallurgical reactions take place between the impurities and agents. The impurities can be removed after issuing out of the reactor. The terminal velocity of the agents therefore is one of key parameters affecting the efficiency of the process. In addition, the agents are usually poorly wetted by molten iron. Accordingly, information on the effect of the wettability of the agents on the terminal velocity is of essential importance. Wetted and poorly wetted spheres made of acrylic resin, polyamide, polyacetal, and fluororesin were used to obtain an empirical equation of the terminal velocity in an inclined pipe.
In recent years there has been a demand for the development of highly efficient heat exchangers for the purpose of saving energy and resources. In the surface heat exchanger with a condensation phenomenon, promoting the condensation heat transfer includes the superhydrophilic and superhydrophobic processing etc. of the condensing surface. In this study, the condensation heat transfer characteristics on the vertical condensing surface coated in the titanium dioxide (TiO2) photocatalyst which has the superhydrophilic property are investigated. Then, the condensation experiment of steam to the condensing surface coated in the TiO2 photocatalyst is carried out. As a result, we found that the condensation heat transfer was promoted about 51% when the condensing surface was coated in the TiO2 photocatalyst.
This paper describes the fabrication of hollow particles using microbubble generation technique. Conventional hollow particle generation techniques relate to several problems such as long synthesis time and complicated process. In this study, we succeeded in the fabrication of hollow particles having a diameter of <5 μm by simply blowing cyanoacrylate vapor into water in the form of microbubbles. However, in order to apply the hollow particles for medical applications, it is required to decreasing the diameter. Therefore, in the form of microbubbles and examined the effect of pH and gas supply on the fabricated particles. As a result, hollow particles fabricated in pH 3 condition were much smaller than those fabricated in pH 7 condition, and the use of poorly-soluble gas increased the ratio of hollow particles to solid particles. The CA particles prepared in this study would possibly have excellent thermal and sound insulation properties owing to the hollow structure. Furthermore, though further downsizing of hollow particles are required, CA particles can find the application for drug delivery to the targeted sites.
A thermal storage technique using phase-change materials has attracted considerable attention as a means of reducing energy consumption and protecting the environment against global warming. Sugar alcohol, a phase-change material, can be used for thermal storage; it has a higher thermal storage capacity and a high phase-change temperature than those of its widely used counterpart, paraffin. Micro-encapsulation of phase-change-materials increases both the surface area per unit volume and the transportability of the particles in the form of a slurry or emulsions. However, conventional methods of micro-encapsulation are associated with some problems such as long synthesis times and complex processes. The purpose of this study is to demonstrate a simple and quick fabrication process for sugar alcohol microcapsules by mixing a sugar alcohol/oil emulsion and cyanoacrylate/oil emulsion. We also report on the thermal properties of sugar alcohol microcapsules.
This study aims to obtain basic knowledge on the atomization by unlike-jet impingement which may be of use for simultaneous atomization and effective mixing of two liquids. A radial compound liquid-sheet jet was formed by normal impingement of two liquid-jets of immiscible liquids – water-solution of propylene-glycol and silicone oil #10. The breakup behavior of liquid-sheet was observed by the two-color flash photography. The breakup radius of liquid-sheet and the number of perforations on liquid-sheet were evaluated from the images. The mean diameter of produced droplets was measured by the laser-diffraction method. Sampling the droplets by the oil-sensitive paper, the configuration of individual droplets was also investigated. The results were compared with those of conventional liquid-sheet formed by alike-jets impingement, and the breakup process of the compound liquid-sheet was discussed.
Gasification is a key technology for efficiently utilizing solid fuels. The large moisture content in lignite can be utilized during gasification reactions. Since a fluidized bed gasifier usually operates at low temperature, highly concentrated tar is generated with syngas. It is important to design a system that can decrease tar. In this study, a new fluidized bed gasification system that use a tar reformer, which consists of a dual fluidized bed, was proposed. A tar reformer that contains tar-absorbing particles in the stage subsequent to the fluidized bed gasifier was employed. This allows for the re-utilization of tar-absorbing particles for extended periods of time by separating the tar-absorber and tar-absorber regenerator. The purpose of this study was to predict the behavior of the tar-absorbing particles in the tar reformer using a laboratory-scale cold model tar reformer. Additionally, the gasification characteristics of lignite were evaluated using a laboratory-scale hot model fluidized bed gasifier. As results, the behavior of particles in the tar reformer and the gasification characteristics of lignite were investigated by using a laboratory-scale fluidized bed. The calculated pressure profile in the tar reformer corresponds qualitatively to the measured pressure profile. Additionally, for the gasification characteristics of lignite, the gas yields in syngas were increased remarkably by the effect of steam, while the tar concentration in syngas decreased significantly.
The paper deals with the drag force acting on a car in a line of cars with an experiment using scale car models in a passing water tank. The drag force of a car model was measured and the velocity field around it was also measured by PIV.The drag force reduction on a car model in a line was confirmed, which was known as effects of a slipstream and a backslip.The velocity fields revealed the relationship of the vortex in the wake of the car model to the drag force.When the following car was in the wake of the leading car, the drag force of both the following and leading cars was reduced.
Commercial wood pellets are upgraded by the pyrolysis treatment in a wide temperature range of 378-773 K that includes both the torrefaction and carbonization temperature conditions. The trade-off relationship between apparent density and higher heating value of pyrolyzed wood pellets (PWP) is confirmed, which implies the existence of an optimum pyrolysis condition to produce PWP. The progression of pyrolysis is found to be identified by the mass yield of PWP. Noticing the color variation of PWP with the progression of pyrolysis, the relationship between the mass yield and CIELAB color parameters is examined. Two experimental correlations to estimate the mass yield are presented using the color coordinate, b* and the hue angle, h. From the comparison between predicted mass yields and experimental data, it is found that the experimental correlation using the hue angle can evaluate the mass yield with an accuracy of around ±10% in a wide range of mass yield between 0.2 and 1. Therefore, it is concluded that the hue angle can be one of the useful indicators for a nondestructive inspection method of PWP.
In this study, a novel dynamic mode decomposition (DMD) technique combining proper orthogonal decomposition (POD) and linear stochastic estimation (LSE) was developed. The availability was also examined experimentally for flow-induced sound from a forward-facing step by simultaneous measurements of surface pressure and resulting far-field sound in a low-noise wind tunnel, and the data obtained were analyzed by the proposed method. By using this method, a dominant surface-pressure-fluctuation mode, contributing to the sound radiation, was identified. Further, it was found that low-order POD modes of the surface-pressure-fluctuation of the step related to the large scale coherent structures did not necessarily have a strong impact on the far-field sound.
The sensitivity of the turbulence statistics of grid-generated turbulence to small variations in the mean flow velocity was investigated in this study. Such small velocity variations negligibly affect the anisotropy of grid-generated turbulence. The relative effects of these small velocity variations on the turbulent kinetic energy, its dissipation, the length scales of the turbulence, the invariance of the turbulence, and the turbulent diffusion coefficient were examined. The k–ε turbulence model, which is a standard computational fluid dynamics model, was used to estimate the relative effects. The small variations in the mean flow velocity were produced by adjusting the wind tunnel ceiling height. The relative effects of these variations on the turbulence statistics were compared by the gradients in their respective linear approximations. The invariance of the homogeneous turbulence was found to be the most sensitive to small velocity variations, whereas the two length scales were relatively insensitive to the variations. The sensitivity of the turbulence statistics was assessed using linear approximations in this study.
Phase-turbulence intensity can be used to visualize the separation and reattachment points of an airfoil, which are closely related to its stall. In this paper, we detect these points above the surface of a NACA0012 airfoil by using threedimensional phase-turbulence intensity. Moreover, because the previous intensity could not discriminate between separation and reattachment points, we introduce an expanded phase-turbulence intensity that includes the velocity gradient normal to the airfoil surface in order to solve this problem. Using this intensity, we can discriminate between separation and reattachment points. We measure the three-dimensional phase-averaged velocity field around a NACA0012 airfoil by means of stereoscopic PIV in multiple cross-sections in a periodic flow for Reynolds number Re=4542 and reduced frequency k=3.68.
A two-phase converging-diverging nozzle is a device converting the thermal energy of a liquid-gas flow at the inlet to the kinetic energy of supersonic flow at the outlet. The pressurized dissolution method is one of the micro-bubble generation methods, by reducing the pressure of the water after the water had been saturated with gas under a high pressure. In the previous study, the pressurized dissolution method using a converging-diverging nozzle was used to generate a supersonic flow but it didn’t succeed. Therefore, the pressurized dissolution method was modified by connecting two converging-diverging nozzles in the present study. The aim of connecting two nozzles is to generate a two-phase flow before the downstream nozzle because one nozzle makes only single phase flow at the throat. As increasing the CO2 dissolved gas rate, the many bubbles were generated and the void fraction also increased but the liquid velocity decreased at the throat. Therefore, the study shows the proper condition to obtain a supersonic flow.
A new wave power generation system is proposed to be installed in a vertical slit type breakwater. The merits of the system are as follows: (i) no occupation of sea surface, (ii) low cost maintenance, and (iii) high energy efficiency by using accelerated flow from the slit of breakwater. In this study, a new, higher efficiency generator is proposed. An elastic rectangular plate connected to a wheel and axle via a wire is set in the water chamber. When the wave drag bends the plate, tension appears in a wire causes rotation of a wheel connected to a generator. To estimate the power of the proposed system at full scale, the wave energy flowing into the breakwater was simulated numerically. The results show that more than 60% of the wave energy is collected in the water chamber behind the slit with a small opening ratio. Although the output power of the bending plate is rather small, the power per unit of occupied sea area is somewhat superior to that of existing systems.
The performance of an undershot micro water wheel for the power generation in a snow drainageway was investigated by the field test. The power coefficient of water wheel with arc blades is better than that with the straight blades. The peak value of maximum power coefficient CPmax depends on the submerged blade height hc/D, and it is found that the power coefficient of the water wheel with arc blades of β = 30° is larger than the other inlet angle.
In the present study, an experimental investigation is performed to obtain two-dimensional velocity field of the turbulent flow through the double bend pipe outlet. The main objective of the study is to investigate the velocity fluctuation in the recirculating flow region on the double bend pipe layout. Phased Array Ultrasonic Velocity Profiler is applied to obtain two-dimensional velocity field in a turbulent flow condition. In a water circulation piping system, the experiments are conducted in the turbulent flow condition, Reynolds number Re = 10,000. The measurement positions are located x/D = 1 and 1.5 (D = 50 mm) downstream of the double bent pipe outlet. Two-dimensional velocity field from the measurement result of Phased Array is compared with Particle Image Velocity (PIV) method. The reattachment point of the recirculating flow is found at the position x/D = 1. The axial and radial velocity fluctuations are analyzed near the reattachment point. The flow distortion and flow-accelerated phenomenon occur at the measurement positions downstream of the double bend pipe outlet.
The aerodynamic characteristics of sports suits play a crucial role in helping professional athletes gain a competitive edge in their chosen sport. The fluid forces acting on the body of the sports competitor are influenced by the surface topology of the fabric, position and size of the seams, use of fasteners, and air permeability of the fabric. Wind tunnel experiments and numerical simulations provide deep insight on the aerodynamic characteristics of sports suit designs. Ski jumping is a sport in which the competitor is judged based on the flight form and flight distance; therefore, ski jumpers attempt to fly as far as possible upon take-off. The fabric used for ski jumping suits plays a crucial role in achieving favorable aerodynamic characteristics. According to the rules and regulations for ski jumping competitions, the outstretched fabric should have a minimum air permeability of 40 L/m2/s at a water pressure of 98 Pa (10 mmAq). To date, little is known regarding the effects of air permeability on the aerodynamic characteristics of ski jumping suits, which forms the motivation of this study. The purpose of this study is to investigate the effect of air permeability on the aerodynamic characteristics of ski jumping suits. Wind tunnel experiments were carried out on an elliptic cylinder clothed with ski jumping suit fabrics of different air permeability. The aerodynamic forces acting on the fabric-clothed elliptic cylinder were measured using a three-component force balance. The velocity profiles were also measured to examine the effect of air permeability on the flow around the fabric-clothed elliptic cylinder. The experimental results show that the drag forces decrease with an increase in air permeability and the stall characteristics are greatly affected by the air permeability. The maximum lift coefficients are lower for fabrics with higher air permeability. However, this is compensated by the occurrence of stall delay for these fabrics and an increase in the lift-to-drag ratio at higher angles of attack. The velocity profiles around the fabric-clothed elliptic cylinder also vary, depending on the air permeability of the fabric.
A mercury target vessel, composed of SUS316L stainless steel, is used for the pulsed spallation neutron source and is assembled via gas tungsten arc welding. While in operation, the target vessel suffers approximately 109 loading cycles with a high strain rate of approximately 50 s-1 because of the proton-beam-induced pressure waves in mercury. The gigacycle fatigue strength for solution annealed SUS316L stainless steels and its welded specimens were investigated through ultrasonic fatigue tests. The experimental results showed that an obvious fatigue limit was not observed at fewer than 109 cycles for the base metal. In the case of no weld defects observed via penetration tests, the fatigue strength of the removed-weld-bead specimen, in which the weld lines were arranged at the center of the specimen, appeared to be slightly higher than that of the base metal. By contrast, as-welded specimens with the weld bead intact showed apparent degradation of the fatigue strength owing to the stress concentration around the weld toe.
The authors have developed a new recycling method for high water content mud which is called “Fiber-Cement-Stabilized Soil method”. In this method, paper debris (fragments of old paper) and solidification material are mixed with mud to produce modified soils. The modified soils have several features such as large failure strength, large failure strain, and high durability in wetting and drying condition. However, recently, as the price of old paper is increasing, development of new fiber materials which can substitute for paper debris is strongly desired. In this study, the applicability of gypsum board paper to Fiber-Cement-Stabilized Soil method was investigated. The board paper was cut into small pieces with the same size of conventional paper debris, and they were used to produce modified soils. As a result, modified soils using board paper only did not have enough failure strength compared to modified soils produced by using conventional paper debris. However, when the board paper and paper debris were used together to improve the sludge, the amount of paper debris was reduced to a half of the amount used in conventional Fiber-Cement-Stabilized Soil method to get enough failure strength.
The estimation of the slip deformation under the multiaxial stress state in the polycrystalline structure, which is caused by highly anisotropic deformation in microscopic scale of material, can provide an important information to understand the deformation mechanisms of crystalline material. In the present study, an evaluation method of slip deformation in the microscopic local region is proposed by coupling the Digital Image Correlation (DIC) Method and the crystalline plasticity theory. Microscopic strain field and slip deformation of the polycrystalline pure copper under uniaxial tension were evaluated using the proposed method. The nonuniform deformation in the crystal grain was firstly evaluated by DIC. Then, the slip deformation for all grains and all slip systems were estimated using the proposed method. Although the initial crystalline orientations were similar for different grains, the active slip systems for the grains did not coincide due to the interaction with surrounding grains. The multiple slip deformation occurred for almost crystal grain regardless of the degree of the total slip in the FCC metal.
The tension-compression asymmetry under plastic deformation of cast and extruded AZ31 magnesium alloys was investigated. The cast alloy had a rather random texture, while the extruded alloy had a strong texture in which most of grains have an orientation of their basal planes parallel to the direction of extrusion, namely a basal fiber texture. Uniaxial tension test, uniaxial compression test, and equi-biaxial compression test were performed on both alloys. Based on the results obtained, influences of the deformation pattern and the initial texture on the stress-strain relation and the variation of plastic work were discussed. It was found that the activity of the extension twinning strongly influenced on the stress-strain relations under uniaxial deformations, with regard to the relation between the crystallographic preferred orientation and the loading direction. The comparison of the result under the equi-biaxial compression with that under the uniaxial tension revealed the similarity of mechanical responses, even on strongly textured extruded alloy, owing to the geometrical equivalence on deformation of the specimens. On the other hand, there were clear differences on the fracture stresses as well as the fracture morphologies between the equi-biaxial compression and the uniaxial tension, because of the different fracture mode under compression and tension.
Out-of-plane impact is one of the most extreme forces acting on carbon fiber reinforced plastics (CFRP), because it can internally damage CFRP laminates easily. In particular, delamination is a major factor that decreases in-plane compressive strength. Therefore, a method to improve and recover this compression strength after impact is necessary. Previous research has focused on the repair of delaminated carbon fiber reinforced thermoplastics (CFRTP) laminates via thermal fusion bonding (TFB). In this study, the authors investigated the relationship between the shear strength and the repair conditions, temperature, and time of TFB for repairing delaminated CFRTP laminates. The results showed that the interlaminar shear strength increased with increasing repair temperature. A longer repair time led to a slightly higher interlaminar shear strength.
The purpose of this study is to propose an effective procedure to predict the low cycle fatigue life of stainless steel products．By using the cantilever type rotational bending fatigue tester, the low cycle fatigue behavior of stainless steel was evaluated. In order to confirm the obtained low cycle fatigue behavior is correct, the fatigue life prediction of drilled flat bar specimen under cyclic four points bending load was conducted. Test results showed that the low cycle fatigue characteristics could be evaluated by developed fatigue tester. Moreover, the fatigue life of flat bar specimen was well predicted by the Miner’s Cumulative Damage Rule．Test results showed that the low cycle fatigue characteristics could be evaluated by developed fatigue tester. Moreover, the fatigue life of flat bar specimen was well predicted by the proposed procedure.
This paper provides an analysis of transducer creep by quantifying the individual creep contributions of the counterforce; strain gage backing and adhesive; and strain gage resistive metal foil. The analysis utilizes 14 plane-strain finite element models of a 30-kg aluminum bending beam load cell instrumented with strain gages made with Cu-Ni (constantan) and Ni-Cr (modified Karma) resistive metal foil and with end loop lengths varying from 0.09 to 0.30 mm. Physical measurement of transducer creep is also performed using dead-weight load application of aluminum bending beam load cells corresponding to the finite element models. This paper demonstrates good correlation between finite element analysis and dead-weight creep test results: minimum transducer creep of -22 and -30 μV/V is achieved for strain gages made of Ni-Cr and Cu-Ni resistive metal foil with end loop lengths of 0.18 and 0.20 mm, respectively.These results are consistent with the analysis in that the relative lengths of the end loops for the two resistive metal foils correspond with their relative creep contributions.
In recent years, with the rapid development of nanotechnology, structural health monitoring (SHM) based on carbon nanotubes (CNTs) has been developed with CNTs’ excellent self-sensing ability. This paper presents an experimental methodology on detection and imaging of damages for composites by using electrical impedance tomography (EIT). A CNT film is attached on the surface of a glass fiber reinforced polymer (GFRP) plate as a smart sensing skin. EIT is then used to reconstruct the change of internal conductivity of the CNT film caused by damages with boundary voltage measurements. It is formulated as a linear inverse problem, and an inverse analysis with Tikhonov regularization is used to perform the reconstruction. Two criteria, i.e., L-curve and generalized cross validation (GCV), are adopted to determine an appropriate parameter for Tikhonov regularization. Experimental results have demonstrated that combined with CNT film’s electrical properties, EIT can successfully reconstruct the localized areas with significant conductivity reduction caused by damages, providing a versatile tool to quantitatively indicating the location and size of the damages.
The infrared thermographic test has the advantages of safety, efficiency, and ease of use. However, the test is often subjected to environmental influences, which sometimes causes false detection of flaws. Background reflection from sunlight or neighboring structures is one of the major factors contributing to this issue. In most cases, the background reflection results in a higher temperature, which is recognized as a flaw indication. In this study, the authors apply a polarization theory to address the problem and propose a quantitative separation method of background reflection and flaw indication. As the first step of the study, the polarized emissivity and the polarized reflectivity were quantitatively evaluated. Based on these results, a quantitative extraction program for detection of flaws has been proposed.
For the external wall of building, non-destructive inspection is recently needed, because fall accidents of tiles and mortar are increasing. In infrared thermographic testing as this inspection method, background reflection is one of the main causes of false detection. The authors developed image processing program to reduce the background reflection from a thermal image. The program mainly consists of two parts. The first part is the correction of emissivity. The correction of emissivity is carried out for each pixel in the thermal image according to the emissivity theory. The authors confirmed that the first part of this program can correct efficiently the emissivity change for a flat plate and a curved surface. The second part of the program is the reduction of a background reflection. To reduce the reflection, the background heat source should be measured separately. In measuring the reflection, there are two important points about a focus and a specular reflectivity. Consequently, this program can reduce the effect of reflection and extract only the emission of the flaw part from the thermal image including the background reflection.
Japanese swords are fabricated by craftsmen called swordsmiths. Furthermore, they are finally finished by a hand-polishing process by craftsmen called Japanese sword polishers. Japanese sword polishers polish the swords using various sword-polishing stones and draw out their beauty to the maximum extent possible. In this study, we investigated both the mechanical characteristics of sword-polishing stones and the Kansei (sophisticated sensation) evaluation by sword polishers. According to the results of our evaluations, the abrasive grains of natural polishing stones are smaller than those of artificial polishing stones. Moreover, we evaluated the Kansei of Japanese sword polishers using the DEMATEL method and we attempted to visualize the process by which sword polishers acquire their expertise.
Recently, a film-type sensor was developed for understanding the force between contact interfaces. This sensor is thin and flexible, and can easily measure force distribution quantitatively. In this study, we used the film sensor to measure the circumferential pressure distribution between a model tube and balloon catheter. The number of measurement points was 30, and the pitch was taken as 1.5 mm (9.5° apart in an 18-mm-diameter circle). The fabricated sensor sheet was rolled and inserted between the silicone model tube, with a pseudo-plaque, and the balloon. As a result, the contact pressure value measured at the step region near the plaque was significantly smaller than that at other regions. Poor contact was expected to occur because of the presence of the plaque. In addition, the contact pressure at the plaque region was slightly higher than that at the smooth surface region. This sensor is thought to be useful for understanding the balloon pressure distribution on irregularly shaped model vessels and/or special shaped balloons such as the scoring balloon.
We developed a measurement system with force-torque sensors that is able to analyze mechanical loads acting on a plastic ankle foot orthosis (PAFO) from the sole of the foot during swing phase of orthotic gait. Using this system, we compared kinetic loads applied to the orthosis during walking between hemiplegic patients and healthy volunteers. The results show that the system can be used to measure kinetic loads and revealed differences in the range of kinetic loads acting on the orthosis from the sole of the foot between the volunteer group and the patient group. The range of heel kinetic load was 11.8 times larger in the volunteer group than in the hemiplegic patient group, and the range of toe kinetic load was 2.6 times larger. In conclusion, we developed a system for measuring kinetic loads between the sole of the foot and an orthosis during swing phase. Also, some differences in kinetic loads were found between healthy volunteers and hemiplegic patients.
In recent years, the number of patients with articular cartilage disease has been increasing. To diagnose the disease at an early stage, a non-contact diagnostic method is required. This paper describes the development of a method for measuring the viscoelastic properties of articular cartilage by acoustic excitation at low frequency. In this method, the articular cartilage's complex shear modulus is obtained by measuring the phase velocity of a stationary wave on the articular cartilage that is excited by a wide range speaker; the displacement response at the surface of the specimen is simultaneously measured at multiple points by two laser displacement sensors. The phase velocities of shear waves are obtained from the displacement responses and then the viscoelastic properties are evaluated using a Voigt model. In this paper, the effectiveness of the system was investigated by measuring the viscoelastic properties of a gelatin phantom with a collagen concentration of 5 wt. % at 50~120 Hz excitation. The results showed that vibrations with the same frequencies as the input waves were produced in the specimen and that the obtained phase velocities and viscoelastic properties were similar to those obtained in previous studies.
The purpose of this study was to construct a system to estimate brain concussion risk based on video footage of collisions during American football games. In this system, the collision motions of collegiate football players are reproduced from the video by using motion analysis of a whole-body model, and the mechanical parameters thus obtained are input into two helmeted finite-element human head models as the initial condition of the collision analysis. The injury risk of each collision is then estimated using 9 risk predictors based on the kinematic behavior of the head or the deformation of the brain. In this study, 17 head impact accidents (9 concussion cases and 8 non-injured cases) were reproduced using this system to determine the injury risk functions using logistic regression analysis. These analyses led to the conclusion that the estimated risk in the injured cases was higher than in the non-injured cases, when using a new risk predictor that combines translational acceleration of the head and von Mises stress in the brain compared with that when using either of the predictors alone.
The fingers are capable of extremely fine motions, and they play a critical role in everyday activities. Movements of the fingers that occur frequently during activities of daily living (ADLs) include pinching and grasping. For pinching, the thumb is in an opposing position, and in most instances, either the index or middle finger is used. For grasping, the fingers are completely flexed. By acting in an opposing position during these movements, the thumb enables the hand to perform its role in a normal manner. In clinical practice, the interphalangeal (IP) joint of the thumb is a common location where arthritis and other inflammatory diseases tend to occur because of the excessive burden on this joint. Therefore, understanding the articulating surface motion of the joint is important. The authors used magnetic resonance imaging (MRI) to investigate the variation in contact area and contact distribution of the in vivo IP joints of the thumb in static joint angles during ADLs. The aim of the present study was to analyze in vivo movement using MRI to examine the cartilage contact and three-dimensional motion of the IP joint of the thumb during ADLs.
The radiocarpal joint transfers loads from the forearm to the hand, and facilitates fine tasks of the hand and fingers by providing a considerable degree of stability. Investigations of in vivo articular contact behavior at the radiocarpal joint are important for understanding the biomechanical functions under physiological loading. Further, knowledge about the biomechanics of the radiocarpal joint would provide a useful clinical indicator for assessing the joint instability and diagnosing osteoarthritis. The objective of this study was to assess in vivo articular contact behavior between the radius and scaphoid and between the radius and lunate using a two-dimensional (2D) to three-dimensional (3D) image matching technique. Four wrist joints of four normal male subjects were enrolled in this study. Biplanar X-ray images were taken during dorsal/ palmar flexion and ulnar/radial deviation of the wrist joint. The articular contact was estimated from the joint space distance smaller than the mean cartilage layer thickness measured using an MRI scanner. The distributions of estimated contact area and the contact point locations varied markedly with wrist positions. The present result would be able to provide a fundamental knowledge about the biomechanics of the wrist joint.