Skidding analysis of angular contact ball bearing subjected to radial load and angular misalignment

Journal of Mechanical Science and Technology - Skidding is a phenomenon that frequently occurs in ball–raceway contact areas of bearings and often leads to their early failure. This paper...     

An efficient method for identification of motion error sources from circular test results in NC machines

This paper proposes an efficient method for the identification of motion error sources involved in NC machines by the circular test, which is often used in estimating the motion accuracy of NC machines. The motion error signal from the circular test is classified into two fundamental patterns: a nondirectional error pattern (the mean of the clockwise and counterclockwise test signals); and a directional error pattern (deviation of clockwise or counterclockwise test signals from a nondirectional error pattern). The present paper proposes two identification schemes: the frequency analysis method and the weighted residual method. The frequency analysis method is used for identifying error sources of the nondirectional error pattern and the weighted residual method is used for identifying error sources of the directional error pattern. A menu-driven, user-oriented computer program is written to realize the entire proposed identification procedure. The proposed identification method is applied to two typical circular test results in order to verify its effectiveness.     

Optimization of partially crowned roller profiles for tapered roller bearings

The roller profile plays a key role in the overall performance of roller bearings. In traditional profile design for roller bearings, the roller profile was often analyzed in terms of the bearing performance, particularly the fatigue life. However, the bearing dynamic stiffness and fatigue life were seldom considered simultaneously in the design of Tapered roller bearings (TRBs). Among the available roller profiles, the partially crowned roller profile has been acknowledged as one of the best from the viewpoint of the bearing fatigue life and stiffness characteristics. This paper presented a design optimization for the partially crowned roller profile to improve the performance of TRBs. Two profile parameters of rollers employed for TRBs including the central flat length and crown radius were investigated. The optimal design parameters for the roller profile were obtained in consideration of both bearing fatigue life and stiffness. The proposed design approach was useful and applicable for further geometrical optimization, manufacturing, and engineering application of rolling bearings.     

Statistical investigation into the effects of distributed roller diameter error on the fatigue life of tapered roller bearings

This study examined the effect of distributed roller diameter error on the fatigue life of a Tapered roller bearing (TRB). To this end, a comprehensive analysis procedure to perform a statistical analysis of the fatigue life with respect to dimensional error was presented. The roller diameter error was assumed as normally distributed, with a designated mean value and a varying standard deviation. Simulations were conducted to investigate the effects of roller diameter deviation on the fatigue life of the TRB. The numerical results showed that the normally distributed roller diameter error did not necessarily result in a normally distributed bearing fatigue life. The adequate distribution function for the bearing fatigue life with respect to the roller diameter error was explored and found to be dependent on the amount of standard deviation of roller diameter error. The Weibull distribution is appropriate for a small standard deviation, while the gamma distribution and normal distributions are appropriate for large and in-between standard deviations, respectively.

     

Rapid detection of food pathogens using RNA aptamers-immobilized slide

The purpose of this study was to develop a simple and rapid detection system for foodborne bacteria, which consisted of an optical microscope and its slide chip with artificial antibodies, or RNA aptamers. From an RNA pool, three each RNA aptamers were built by the method of SELEX (systematic evolution of ligands by exponential enrichment) for components of cell wall, LPS (lipopolysaccharide) from E. coli O157:H7, teichoic acid from Staphylococcus aureus and a cell membrane protein of OmpC from Salmonella typhimurium, respectively. These aptamers were hybridized with thiol-conjugated 16 dT-linker molecules in order to be immobilized on silver surface which was, in advance, fabricated on glass slide, using a spin-coating method. To confirm that each aptamers retained its specific binding activities to their antigenic live bacteria, microscopic view of bound cells immobilized on silver film were observed. Furthermore, we observed the fluorescence-emitting bacteria-aptamer complex immobilized on silver film after adding RNA aptamers hybridized with fluorophore, FAM-conjugated 16 dT-linker molecules. As a result, the RNA aptamers-immobilized slide system developed in this study was a useful new tool to rapidly monitor individual food pathogens.     

Three-Level Capacitor Clamping Single Sustaining Driver With Dual Energy Recovery Path for Low Cost AC Plasma Display Panel

This paper proposes a novel single sustaining driver with half the device voltage stresses for plasma display panel (PDP). Since proposed driver lowers the voltage stress of sustain switches by series-connected configuration of switches and clamping capacitor between switches, it uses half voltage rating of sustain switches and, thus, reduces the conduction loss of power switches compared with those of the conventional single sustaining driver. Despite device count possibly increasing, by using low voltage switches and capability to produce zero voltage level in sustaining inverter, the circuit cost does not increase compared with the conventional. In addition, the proposed driver has two energy recovery inductors that are utilized to separate the energy recovery path. This feature reduces the power loss of energy recovery circuit (ERC), which gives an improvement in system efficiency. A comparative analysis and experimental results are presented to show the validity of the proposed single sustaining driver.     

A multiple-hypothesis approach for multiobject visual tracking.

In multiple-object tracking applications, it is essential to address the problem of associating targets and observation data. For visual tracking of multiple targets which involves objects that split and merge, a target may be associated with multiple measurements and many targets may be associated with a single measurement. The space of such data association is exponential in the number of targets and exhaustive enumeration is impractical. We pose the association problem as a bipartite graph edge covering problem given the targets and the object detection information. We propose an efficient method of maintaining multiple association hypotheses with the highest probabilities over all possible histories of associations. Our approach handles objects entering and exiting the field of view, merging and splitting objects, as well as objects that are detected as fragmented parts. Experimental results are given for tracking multiple players in a soccer game and for tracking people with complex interaction in a surveillance setting. It is shown through quantitative evaluation that our method tracks through varying degrees of interactions among the targets with high success rate.     

Aptamers for Anti-Viral Therapeutics and Diagnostics

Viral infections cause a host of fatal diseases and seriously affect every form of life from bacteria to humans. Although most viral infections can receive appropriate treatment thereby limiting damage to life and livelihood with modern medicine and early diagnosis, new types of viral infections are continuously emerging that need to be properly and timely treated. As time is the most important factor in the progress of many deadly viral diseases, early detection becomes of paramount importance for effective treatment. Aptamers are small oligonucleotide molecules made by the systematic evolution of ligands by exponential enrichment (SELEX). Aptamers are characterized by being able to specifically bind to a target, much like antibodies. However, unlike antibodies, aptamers are easily synthesized, modified, and are able to target a wider range of substances, including proteins and carbohydrates. With these advantages in mind, many studies on aptamer-based viral diagnosis and treatments are currently in progress. The use of aptamers for viral diagnosis requires a system that recognizes the binding of viral molecules to aptamers in samples of blood, serum, plasma, or in virus-infected cells. From a therapeutic perspective, aptamers target viral particles or host cell receptors to prevent the interaction between the virus and host cells or target intracellular viral proteins to interrupt the life cycle of the virus within infected cells. In this paper, we review recent attempts to use aptamers for the diagnosis and treatment of various viral infections.     

Linear ball guide design optimization considering stiffness,friction force,and basic dynamic load rating using particle swarm optimization

Journal of Mechanical Science and Technology - Linear-motion ball guides are one of the most common supporting elements in machine tools. Their design optimization is highly crucial for engineers...