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Constant velocity (CV) joints are the primary component of a vehicle that transmits the driving force from an engine/transmission to a wheel at a constant speed. A CV joint comprises numerous mechanical parts. The roller and housing are in contact and, therefore, subjected to contact stresses. Contact stress causes sliding friction because of microslip in the contact area inside the CV joint. This internal friction generates an axial force, dependent on the kinematics. A generated axial force (GAF) is caused by the internal friction in a plunging-type CV joint. This force can have a direct impact on the degradation of the noise, vibration, and harshness characteristics of a vehicle. The typical vibration of a CV joint transmitted to the vehicle is shudder, which degrades the lateral oscillation of the vehicle. Shudder is generated by the GAF and results from the rotation of the CV joint during rapid acceleration, stimulating the lateral movement of the vehicle and causing discomfort to passengers. In this study, the radii of the roller and the housing were selected as the design parameters, and the contact stress was minimized through the sensitivity analysis. The GAF of the existing CV joint and optimized CV joint are compared through a multibody dynamic simulation. An axial force test is performed on the CV joint of a C-segment vehicle to verify the dynamic simulation results. The friction characteristics of the greases used in the CV joint were also confirmed by the schwingung reibung verschleiss (SRV) friction test. The results obtained can be used to reduce the GAF of the CV joint and to build an optimized CV joint model.

This paper describes the optimized design of a knee joint for an active transfemoral prosthesis with a fully active knee joint. The active transfemoral prosthesis which can help amputees to walk naturally with a powered motor has been actively developed around the world with advances in battery technology and others. However, most of them are designed for level walking, especially in South Korea, research about active prosthesis is insufficiently carried out, also depends on foreign technology. Therefore, this study focuses on the development of prosthetic knee joint that can overcome complex walking environment including stair walking. The developed prosthesis has one degree of freedom at the knee joint and can mimic the human walking mechanism. The prosthetic knee joint has a simple high-torque mechanism comprising a flat BLDC motor, harmonic drive, and pulley to generate the torque required for walking on stairs, which requires the largest torque. As one of the most important factors for comfort and fatigue, the total weight of the prosthesis should be minimized. Topology optimization was carried out to reduce the weight, and an advanced knee joint design was developed based on the optimization. The structural safety was validated via finite element analysis and a strain experiment under working conditions.

Low pressure materials pre-treatment process has been developed as an alternative to the existing high-temperature sludge drying, limestone calcination, and limonite dehydroxylation. Using the thermodynamic equilibrium relationship between temperature and pressure represented by the Clausius-Clapeyron equation, the operational temperature of these reactions could be lowered at reduced pressure for increased energy efficiency. For industrial sludge drying, the evaporation rate was controlled by interfacial kinetics showing a constant rate with time and significant acceleration in the reaction could be observed with reduced pressure. At this modified reaction rate under low pressure, the rate was also partially controlled by mass transfer. Temperature of limestone calcination was lowered, but the reaction was limited at the calculated equilibrium temperature of the Clausius-Clapeyron equation and slightly higher temperatures were required. The energy consumption during limestone calcination and limonite dehydroxylation were evaluated, where lower processing pressures could enhance the energy efficiency for limestone calcination, but limonite dehydroxylation could not achieve energy-savings due to the greater power consumption of the vacuum pump under lower pressure and reduced temperatures.

Direct fabrication of titanium (Ti) and niobium (Nb) alloys by direct magnesiothermic reduction from the respective initial metal oxides and complex oxides has been studied. TiO2, Nb2O5, and complex TiNb2O7 oxides were used as raw materials with Mg used as a reductant. To ensure a high chemical potential of the reactants to drive the spontaneous magnesiothermic reduction of the oxide mixtures, excess Mg five times higher than the required stoichiometric molar ratio was added. Samples were heated in a glove box under recycled and purified Ar atmosphere at 1073 K (800 °C) for 10 h. After the reduction of TiO2, intermediate oxide phases of Ti6O could still be observed, but reduction of Nb2O5 and TiNb2O7 showed metallic Nb and Ti-Nb to be present with negligible oxides according to the scanning electron microscope-energy dispersive spectroscopy and x ray diffraction analysis. This indicated that direct fabrication of Ti-Nb alloys through a complex TiNb2O7 oxide is possible and can be more efficient than alloying pure metallic elements of Ti and Nb.

Surface texture patterns have great potential for improving tribological performance in terms of reducing friction and wear. The most common methods for surface texturing are laser and injection molding. The 3D printing method is also used to build parts, patterns, and molds that feature fine details for a wide range of applications because texture manufacturing by 3D printing is faster, more flexible, and less expensive than traditional techniques. To date, there has been no research on textured surfaces produced by 3D printing. Therefore, a new fabrication method using 3D printing to improve friction and wear properties is a topic worth exploring. In this study, a reciprocating friction tester was used to evaluate the friction and wear properties of different surface textures produced by 3D printing. The surface of specimens was examined by electron microscope and scanning electron microscope before and after the test. The results show that surface texturing can be applied to 3D printed parts to improve their friction and wear performance.

This paper describes the complete design process of a passive prosthetic foot manufactured of Polylactic acid (PLA). It focuses on the reduction in the weight of prosthetic feet. Most of the prosthetic feet are designed with more weight and material than required. The structure of this passive prosthetic foot is designed and optimized as light as possible by using topology optimization. The topology-optimized model is printed from a Three-dimensional (3D) printer directly rather than interpreting the model using a Computer-aided design (CAD) software. The finite element analysis and the experiments are conducted to validate the structure. The test equipment is designed and installed for simulating the boundary conditions of the Heel strike (HS) and Toe off (TO). Since the weight of the prosthetic directly affects the mobility of patients, the weight of the proposed model is reduced 62 % when compared initial model to the final model.

The objective of this study is to develop a damper that can reduce the amplitude of vibration in various frequency ranges. Previous H/Shaft vibration reduction methods work in a passive way. A dynamic damper reduces the amplitude of vibration at its first mode, but vibration still appears at the second mode. A mass damper or hollow shaft can shift the natural frequency to a lower or higher region. The fixed operating frequency prevents vibration from being reduced outside the operating frequency range. The proposed damper uses electromagnets as either masses or actuators to change the damper mode between dynamic damper mode and mass damper mode. The electromagnetic damper (EMD) can change its mode to respond to the vibration excitation at both low and high frequencies. The vibration reduction performance was evaluated by FRF tests in laboratory and vehicle conditions. The results were compared with those of a dynamic damper and indicate that the amplitude of vibration is reduced by 95.6 % when the EMD is implemented on an H/Shaft, whereas only 61.9 % vibration reduction is achieved by the dynamic damper.

Improper clamping of wiper arms can cause problems in the operation of the wiper. An excessive clamping force can cause damage to the wiper arm head. On the other hand, an insufficient clamping force can cause self-loosening of the nut. Given the lack of direct research on the clamping force of the fastener in wiper assembly, this study verifies the existing clamping performance of the fastener in windshield wiper assembly by theoretical and experimental methods. The theoretical calculation results show that all the clamping performance are satisfied under the general snow load condition. However, under the critical load condition, maximum assembly preload and safety margin against slipping are in disagreement with the standard values. This problem is solved by increasing the strength grade of the bolt. The experimental results show a reducing tendency of the clamping force during the snow durability test. However, this reducing clamping force during the 60,000 test cycles is acceptable. In the case of nut reusing more than two times possibly cause a problem of its loosening because of insufficient clamping force. Therefore, it is recommended that the nut should not be reused more than two times.

The peroxisome proliferator-activated receptor δ (PPARD) and peroxisome proliferator-activated receptor γ coactivator 1α (PPARGC1A) genes recently have been suggested to have an association with athletic performance and physical endurance. These gene products are reported to be crucial components in training-induced muscle adaptation, since they are related with mRNA and/or protein activity in coordinated response to exercise. To assess the possible contribution of the PPARD T294C/PPARGC1A Gly482Ser polymorphism to differences in physical endurance, we performed a population-based study of 111 Korean athletes and 145 healthy controls based on their genotype distribution of the genes. The two loci were found to be not deviated from Hardy–Weinberg equilibrium. There were no differences in genotype distribution of PPARD T294C and PPARGC1A Gly482Ser between the athletic group and controls (p > 0.05). In contrast, we found a significant association between the PPARGC1A Gly482Ser polymorphism and the 20 m shuttle run activity (a measure of endurance performance) in the athletic group (p = 0.003). The result showed a remarkable increase in the numbers of shuttle run ratio from subjects with the PPARGC1A Gly/Gly genotype (85.29 ± 28.80) than those with the Gly/Ser (58.05 ± 32.76) and Ser/Ser (68.38 ± 30.47) genotypes. Thus, our data imply that the PPARGC1A Gly/Gly genotype may provide a beneficial effect on elite-level endurance status, although functional studies with larger sample sizes are necessary to elucidate these findings.

Background On November 20, 2016 two novel strains of H5N6 highly pathogenic avian influenza virus (HPAIVs) were isolated from three whooper swans (Cygnus cygnus) at Gangjin Bay in South Jeolla province, South Korea. Identification of HPAIVs in wild birds is significant as there is a potential risk of transmission of these viruses to poultry and humans. Results Phylogenetic analysis revealed that Gangjin H5N6 viruses classified into Asian H5 clade 2.3.4.4 lineage and were distinguishable from H5N8 and H5N1 HPAIVs previously isolated in Korea. With the exception of the polymerase acidic (PA) gene, the viruses were most closely related to A/duck/Guangdong/01.01SZSGXJK005-Y/2016 (H5N6) (98.90 ~ 99.74%). The PA genes of the two novel Gangjin H5N6 viruses were most closely related to AIV isolates previously characterized from Korea, A/hooded crane/Korea/1176/2016 (H1N1) (99.16%) and A/environment/Korea/W133/2006 (H7N7) (98.65%). The lack of more recent viruses to A/environment/Korea/W133/2006 (H7N7) indicates the need for analysis of recent wild bird AIVs isolated in Korea because they might provide further clues as to the origin of these novel reassortant H5N6 viruses. Conclusions Although research on the origins and epidemiology of these infections is ongoing, the most likely route of infection for the whooper swans was through direct or indirect contact with reassortant viruses shed by migratory wild birds in Korea. As H5N6 HPAIVs can potentially be transmitted to poultry and humans, continuous monitoring of AIVs among wild birds will help to mitigate this risk.

Generated axial force (GAF) induced by internal friction in a tripod constant velocity (CV) joint causes shudder, which is related to lateral vibration in a vehicle. GAF is produced by tripod dynamics in the CV joint, and its magnitude is related to an applied torque and articulation angle. GAF provides periodic frictional force, owing to its kinematics, and causes take-off shudder that occurs when a vehicle abruptly accelerates from a stop position. Therefore, accurately estimating the GAF in a CV joint is necessary. A non-rotating type GAF measurement tester is developed to measure GAF more accurately, considering the shudder condition. Results of GAF measurements are compared with those obtained using an existing rotating-type tester. The developed tester provides linear results regardless of test conditions; thus, it can be used to estimate the magnitude of GAF and evaluate the friction performance of grease.

This paper proposes a design for the linear state feedback control of the dual-actuator system, which is a dual-input single-output system for the high-precision manufacturing stage. The proposed control prevents saturation or reduces the unnecessary movement of the piezoelectric (PZT) actuator at the transient response by tracking the error between the estimated and actual positions of the coarse-actuator system at each control sample. Also, a new mechanism of the single-stage dual actuator is introduced. The axes of the stepper motor and the PZT actuator are co-axial. The coupling effects between the stepper motor and the PZT actuator are considered. Both the simulation and experiment results show that the proposed algorithm successfully prevents unwanted motions of the PZT actuator at the transient response. The experiment results show that the settling time and overshoot were enhanced by 45.7 and 95.9 %, respectively, for the proposed algorithm when the reference distance was 10 μm, which exceeds the stroke of the PZT actuator.

Room temperature baroplastic processing of polystyrene (PS) and poly(n-butyl acrylate) (PBA) was investigated through the formation of nanoblends of their polymer nanoparticles. Instead of core-shell or block copolymer structures, PS and PBA nanoparticles were synthesized separately through aqueous emulsion polymerization and then mixed and precipitated. The resulting nano-blends provided semi-transparent molding at 25 °C under applied pressure, resembling that of core-shell and block copolymer baroplastic systems. Differential scanning calorimetry measurements of the compressed samples revealed the presence of intermixing glass transition between the two components, which indicated baroplastic processing. However, PS/poly(lauryl methacrylate) blends exhibited no intermixing glass transition, indicating no pressure-induced miscibility between the two phases.

Tripod constant velocity (TCV) joints are common components in automotive and mechanical applications. The benefits of the TCV joint are its high plunge capacity and high torque capacity. During power transmission, the friction inside the joint generates an axial force according to the kinematics. This force causes noise and vibration problems. In this study, a simplified multi-body dynamic model based on a phenomenological TCV joint friction model is developed. This model considers the generated axial force (GAF) of a TCV joint with different lubricate conditions. The efficiency and accuracy are verified by comparison with other prediction models and experiments. Thus, this model can be used to design and control the manufacture process of TCV joints.

The microdomain structures and crystallization behavior of the binary blends of poly(methyl methacrylate)-b-poly(pentafluorostyrene)-b-poly(methyl methacrylate) (PMMA-PPFS-PMMA) triblock copolymer with a low molecular weight poly(vinylidene fluoride) (PVDF) were investigated by small-angle X-ray scattering (SAXS), small-angle light scattering (SALS), transmission electron microscopy (TEM), optical microscopy, and differential scanning calorimetry (DSC). A symmetric, PMMA-PPFS-PMMA triblock copolymer with a PPFS weight fraction of 33% was blended with PVDF inN,N-dimethylacetamide (DMAc). In the wide range of PVDF concentration between 10.0 and 30.0 wt%, PVDF was completely incorporated within the PMMA microdomains of PMMAPPFS-PMMA without further phase separation on a micrometer scale. The addition of PVDF altered the phase morphology of PMMA-PPFS-PMMA from well-defined lamellar to disordered. The crystallization of PVDF significantly disturbed the domain structure of PMMA-PPFS-PMMA in the blends, resulting in a poorly-ordered morphology. PVDF displayed unique crystallization behavior as a result of the space constraints imposed by the domain structure of PMMA-PPFS-PMMA. The pre-existing microdomain structures restricted the lamellar orientation and favored a random arrangement of lamellar crystallites.

In order to obtain crosslinked poly(butylene succinate) (PBS) foams with a closed-cell structure, a commercial-grade PBS was first modified in the melt using two different branching agents to increase the melt viscosity. The rheological properties of the branched and crosslinked PBS were examined by varying the amount of the branching agents. The complex viscosity of the crosslinked PBS increased with increasing amount of the branching agent. However, it decreased with increasing frequency. When 2 phr of the branching agent was added to PBS, the storage modulus (G′) was higher than the loss modulus (G″) throughout the entire frequency range, showing that the addition of a branching agent increases the melt viscosity and elasticity of PBS effectively. Closed-cell PBS foams were prepared by mixing the chemical blowing agent with the crosslinked PBS. The effect of the foaming conditions such as temperature and time, and the amount of the crosssslinking agent on the structure of the expanded PBS foams were also investigated.

This report presents a new technical approach for evaluating the fiber orientation of composites using small-angle light scattering (SALS). Glass fiber (GF)/polypropylene (PP) composites with different fiber orientations were prepared by drawing compression-molded specimens. The drawn samples were remelted and then annealed at 150 °C in order to induce a crystalline structure on the fiber surface, and then underwent SALS analysis. The samples showed a combination of circular and streak patterns. The model calculations demonstrated that the number of nuclei on the fiber surface and the thickness of the transcrystalline layer affected the sharpness and intensity of the streak pattern. In addition, the azimuthal angle of the streak pattern was found to be dependent on the direction of the transcrystalline layer, which correlated with the fiber direction. This correlation suggests that the fiber orientation in the composites can be easily evaluated using SALS.

Poly(l-lactic acid-co-succinic acid-co-1,4-butane diol) (PLASB) was synthesized by direct condensation copolymerization ofl-lactic acid (LA), succinic acid (SA), and 1,4-butanediol (BD) in the bulk using titanium(IV) butoxide as a catalyst. The weight-average molecular weight of PLASB was 2.1 × 105 when the contents of SA and BD were each 0.5 mol/100 mol of LA. Electrospinning was used to fabricate porous membranes from this newly synthesized bioabsorbable PLASB dissolved in mixed solvents of methylene chloride and dimethylformamide. Scanning electron microscopy (SEM) images indicated that the fiber diameters and nanostructured morphologies of the electrospun membranes depended on the processing parameters, such as the solvent ratio and the polymer concentration. By adjusting both the solvent mixture ratio and the polymer concentration, we could fabricate uniform nanofiber non-woven membranes. Cell proliferation on the electrospun porous PLASB membranes was evaluated using mouse fibroblast cells; we compare these results with those of the cell responses on bulk PLASB films.

The PBL (Polybutadiene Latex) production process is a t ypical batch process. Changes of the reactor char- acteristics due to the accumulated scaling with the increase of batch cycles require adaptive tuning of the PID controller being used. In this work we propose a tuning method for PID controllers based on the closed-loop identification and the genetic algorithm (GA) and apply it to control the PBL process. An approximated process transfer function for the PBL reactor is obtained from the closed-loop data by using a suitable closed-loop identification method. Tuning is performed by GA optimization in which the objective function is given by ITAE for the setpoint change. The pro- posed tuning method showed good control performance in actual operations.

We have studied the lamellar-level morphology of poly(ethylene terephthalate) (PET)/polycarbonate (PC) blends using small-angle X-ray scattering (SAXS). Measurements were made as a function of the holding time in the melt. We determined the morphological parameters at the lamellar level by correlation function analysis of the SAXS data. An increased amorphous layer thickness was identified in the blend, indicating that some PC was incorporated into the interlamellar regions of PET during crystallization. The blend also exhibits a larger lamellar crystalline thickness (l c ) than that of pure PET. A possible reason for the increase inl c is that the inclusion of the PC molecules in the interlamellar regions causes an increase in the surface free energy of folding. At the early stage of isothermal crystallization, we observed a rapid drop in the value ofl c in the blend; this finding indicates that a relatively large fraction of secondary crystals form during the primary crystallization. In contrast, the value ofl c for the sample that underwent a prolonged holding time increased with time in the secondary crystallization-dominant regime; this observation suggests that the disruption of chain periodicity, which results from transesterification between the two polymers, favors the development of fringed micellar crystals that have larger values ofl c , rather than the development of normal chain-folded crystals.

The supermolecular structures of poly(ethylene terephthalate) (PET), poly(ethylene 2,6-naphthalate) (PEN), and their blend were investigated with optical microscopy and small angle light scattering. With increasing the crystallization temperature, incomplete spherulitic texture was developed for the PET samples. At a high crystallization temperature of 220°C, the light scattering pattern represented a random collection of uncorrelated lamellae. The general morphological appearances for the PEN samples were similar to that of the PET. A notable feature was that the spherulites of the PEN formed at 200°C showed regular concentric bands arising from a regular twist in the radiating lamellae. The spherulitic morphology of the PET/PEN blend was largely influenced by the changes of the sequence distribution in polymer chains determined by the level of transesterification. The increased sequential irregularity in the polymer chains via transesterification caused a morphological transition from a regular folded crystallite to a tilted lamellar crystallite.

Liquid-liquid (L-L) phase separation and its effects on crystallization in polypropylene (PP)/ethylene-propylene rubber (EPR)/ethylene-α-olefin copolymer (ECP) ternary blends obtained by melt extrusion were investigated by time-resolved light scattering (TR-LS) and optical microscopy. L-L phase separation via spinodal decomposition (SD) was confirmed by TR-LS data. After L-L phase-separation at 250°C for various durations, the blend sample was subjected to temperature-drop to 130°C for isothermal crystallization and the effects of L-L phase separation on crystallization were investigated. Memory of L-L phase separation via SD remained for crystallization. The crystallization rate decreased with increasing L-L phase-separated time at 250°C. Slow crystallization for the long L-L phase-separated time could be ascribed to decrease in chain mobility of PP by decrease in rubbery components in the PP-rich region. The ethylene-octene copolymer exhibited good affinity with PP, leading to a slow growth of a concentration fluctuation during annealing.

Influenza viruses are responsible for respiratory illness with significant morbidity and mortality. To curb the disease, two-pronged attack on the virus, therapeutic and prophylactic, is being actively pursued. The therapeutic use of existing anti-influenza drugs, such as amantadine and rimantadine, is limited by their significant adverse side effect, emergence of resistant viral strains, and lack of activity against influenza B virus. A new class of antiviral agents designed to inhibit influenza neuraminidase are currently under active development for use in the prophylaxis and treatment of influenza A and B virus infections. Two of these compounds, zanamivir (GG167) and GS4104 have reached clinical trials. Limitations in the effectiveness and application of inactivated vaccines have stimulated development of alternative approaches to influenza immunization. One such approach is a live, intranasally administered vaccine, attenuated by cold-adaptation of a master strain with subsequent genetic reassortment with circulating wild-type strains. Recently developed reverse-genetics techniques have made it possible to use RNA viruses as vector. Besides DNA viral vectors, live influenza virus vectors may emerge as a useful alternative for the vaccination against different pathogens.

The effect of cure on the crystallization rates of polyphenylene sulfide (PPS) and PPS/carbon fiber composites has been studied by differential scanning calorimetry (DSC). The crystallization rate of PPS increased with increasing degree of cure. The carbon fiber acted as a nucleating agent to enhance the crystallization rate of PPS. The fully cured PPS seemed to be saturated with nucleating sites formed through the cure reaction. Therefore, the presence of carbon fibers gave little effect on the crystallization rate of the fully cured PPS.

Porous low dielectric films containing nano pores (∼20Å) with low dielectric constant (

Influenza vaccine strains have been traditionally developed by annual reassortment between vaccine donor strain and the epidemic virulent strains. The classical method requires screening and genotyping of the vaccine strain among various reassortant viruses, which are usually laborious and time-consuming. Here we developed an efficient reverse genetic system to generate the 6:2 reassortant vaccine virus from cDNAs derived from the influenza RNAs. Thus, cDNAs of the two RNAs coding for surface antigens, haemagglutinin and neuraminidase from the epidemic virus and the 6 internal genes from the donor strain were transfected into cells and the infectious viruses of 6:2 defined RNA ratio were rescued. X-31 virus (a high- growth virus in embryonated eggs) and its cold-adapted strain X-31 ca were judiciously chosen as donor strains for the generation of inactivated vaccine and live-attenuated vaccine, respectively. The growth properties of these recombinant viruses in embryonated chicken eggs and MDCK cell were indistinguishable as compared to those generated by classical reassortment process. Based on the reverse genetic system, we generated 6+2 reassortant avian influenza vaccine strains corresponding to the A/Chicken/Korea/ MS96 (H9N2) and A/Indonesia/5/2005 (H5N1). The results would serve as technical platform for the generation of both injectable inactivated vaccine and the nasal spray live attenuated vaccine for the prevention of influenza epidemics and pandemics.

A computer simulation model was established to analyze the crystallization behavior during the gel spinning of semi-dilute solution of ultra-high molecular weight polyethylene in paraffin oil. A numerical calculation was carried out to predict the temperature and crystallinity profile within a filament. The effects of the fiber radius, cooling temperature, and spinning temperature on the cooling time were discussed for searching the optimum cooling condition during the spinning.