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Sound and vibration analysis are prominent tools for machine health diagnosis. Especially, neural network (NN) strategies have focused on finding complex and nonlinear relationships between the sensor signal and the machine status to detect machine faults. However, it is difficult to collect enough amount of fault data as much as normal status data for training general NN models. To resolve the issue, this paper proposes the autoencoder-based anomaly detection framework for industrial robot arms using an internal sound sensor. The autoencoder uses signals in the normal state of the robots for training the model. It reconstructs the input signals as output, and anomalous states are found from high reconstruction error. Two stethoscopes were attached to the surface of the robot joint as sensors, and the sounds were recorded by USB microphone attached to the outlet of the stethoscopes. Features were extracted from STFT spectrogram images of the gathered sound, then used to train and test an autoencoder model. The reconstruction errors of the autoencoder were compared to distinguish the abnormal status from normal one. The experimental results suggest that the stethoscopes prevent the interference of noise, and the collected sound signals can be utilized for detecting machine anomalies.

Lymphoma is a heterogeneous disease with a highly variable clinical course and prognosis. Improving the prognosis for patients with relapsed and treatment-resistant lymphoma remains challenging. Current in vitro drug testing models based on 2D cell culture lack natural tissue-like structural organization and result in disappointing clinical outcomes. The development of efficient drug testing models using 3D cell culture that more accurately reflects in vivo behaviors is vital. Our aim was to establish an in vitro 3D lymphoma model that can imitate the in vivo 3D lymphoma microenvironment. Using this model, we explored strategies to enhance chemosensitivity to doxorubicin, an important chemotherapeutic drug widely used for the treatment of hematological malignancies. Lymphoma cells grown in this model exhibited excellent biomimetic properties compared to conventional 2D culture including (1) enhanced chemotherapy resistance, (2) suppressed rate of apoptosis, (3) upregulated expression of drug resistance genes (MDR1, MRP1, BCRP and HIF-1α), (4) elevated levels of tumor aggressiveness factors including Notch (Notch-1, -2, -3, and -4) and its downstream molecules (Hes-1 and Hey-1), VEGF and MMPs (MMP-2 and MMP-9), and (5) enrichment of a lymphoma stem cell population. Tiam1, a potential biomarker of tumor progression, metastasis, and chemoresistance, was activated in our 3D lymphoma model. Remarkably, we identified two synergistic therapeutic oncotargets, Tiam1 and Notch, as a strategy to combat resistance against doxorubicin in EL4 T and A20 B lymphoma. Therefore, our data suggest that our 3D lymphoma model is a promising in vitro research platform for studying lymphoma biology and therapeutic approaches.

In order to assemble a driver IC onto a LCD glass panel, Chip on glass (COG) bonding technology using Anisotropic conductive film (ACF) has been widely implemented. The key process parameters in the technology are the temperature, pressure and time during the thermo-compression bonding. These factors mainly affect the quality of the assembled ACF joint being represented by the contact resistance and adhesion strength. This study purposes to obtain the optimal process conditions for high reliability of the ACF joint. In order to determine the optimal condition, the experiments based on the response surface methodology were designed. Based on the experiments and statistical analysis, the empirical model of second-order polynomials approximating the relationships between the process conditions and the response variables of contact resistance and adhesion strength were obtained. The optimal process condition to lead lower contact resistance and higher adhesion strength of the ACF joint was also calculated from the relationships. The optimization was verified through the bonding experiments conducted under the derived optimal process condition. In addition, the reliability of the ACF joints according to the variation of the process conditions was evaluated in high temperature and humidity environment (85°C/85%RH). Consequently, it was shown that the reliability of ACF joints assembled under the optimal process conditions was superior to others after the 85°C/85%RH tests.

Tool condition monitoring plays one of the most important roles in the improvement of both machining quality and productivity. In this regard, various process signals and monitoring methods have been developed. However, most of the existing studies used cutting force or acoustic emission signals, which posed risks of interference with the machining system in dynamics, fixturing, and machining configuration. In this study, a feed motor current signal is used as a process signal representing process and tool states in tool breakage monitoring based on an adaptive autoregressive model and unsupervised neural network. From the experimental results using various cases of tool breakage, it is shown that the developed system can successfully detect tool breakage before two revolutions of the spindle after tool breakage.

The load applied to a machine tool feed drive changes during the machining process as material is removed. This load change alters the Coulomb friction of the feed drive. Because Coulomb friction accounts for a large part of the total friction the friction compensation control accuracy of the feed drives is limited if this nonlinear change in the applied load is not considered. This paper presents a new friction compensation method that estimates the machine tool load in real time and considers its effect on friction characteristics. A friction observer based on a Kalman filter with load estimation is proposed for friction compensation control considering the applied load change. A specially designed feed drive testbed that enables the applied load to be modified easily was constructed for experimental verification. Control performance and friction estimation accuracy are demonstrated experimentally using the testbed.

Nonlinear friction is a dominant factor of the complexity growth of feed drive dynamic behavior. In particular, a feed drive system equipped with rolling contact components such as ball screws and linear motion (LM) guides undergoes impalpable friction behavior. Therefore, proper modeling and compensation of friction in feed drive components play a crucial role in improving the precision of a feed drive system. In this study, to overcome the accuracy limitation of the simplified feed drive model, a distributed component friction model (DCFM) of a feed drive system is developed. Friction has been modeled as a single element of entire feed drive system in the conventional model. However, the proposed DCFM is composed of models of individual feed drive components such as ball screw and LM guide including their friction behaviors. To take advantage of the DCFM by considering both presliding and sliding friction behaviors of each component, LuGre model is applied. For experimental verification of the accuracy of the proposed DCFM, a specially designed feed drive testbed is constructed. Using the testbed, the friction forces of ball screws and LM guides are measured independently. Using the DCFM, a friction observer is built for real-time monitoring and compensation of the friction force. A proportional-derivative feed drive position controller with an observer-based friction compensator is implemented and the experimental results are presented.

Patient-specific ex vivo models of human tumours that recapitulate the pathological characteristics and complex ecology of native tumours could help determine the most appropriate cancer treatment for individual patients. Here, we show that bioprinted reconstituted glioblastoma tumours consisting of patient-derived tumour cells, vascular endothelial cells and decellularized extracellular matrix from brain tissue in a compartmentalized cancer–stroma concentric-ring structure that sustains a radial oxygen gradient, recapitulate the structural, biochemical and biophysical properties of the native tumours. We also show that the glioblastoma-on-a-chip reproduces clinically observed patient-specific resistances to treatment with concurrent chemoradiation and temozolomide, and that the model can be used to determine drug combinations associated with superior tumour killing. The patient-specific tumour-on-a-chip model might be useful for the identification of effective treatments for glioblastoma patients resistant to the standard first-line treatment. A tumour-on-a-chip model featuring patient-derived glioblastoma cells, vascular endothelial cells and decellularized extracellular matrix from brain tissue can be used to identify patient-specific resistance to standard chemoradiotherapy.

Ultra‐precision positioning plays a crucial role in emerging tec hnologies such as electronics, bioengineering, optics, and various nanofabrication technologies. As a result, various nanopositioning methods have been presented. In particular, nanopositioning using a flexure mechanism and piezo ‐electric actuator is one of the most valuable methods because of its friction ‐free motion and subnanometer ‐scale motion resolution. In this study, a rotational nanoactuator based on a right ‐circular flexure mechanism and piezo ‐electric actuator was developed through a consideration of the kinematics and structural deformation. An experimental setup was constructed to verify the performance expectation. Consequently, it was demonstrated that the developed system had a maximum rotational angle of about 0.01 rad, as well as sufficient linearity with respect to the input voltage.Received 21 July 2014Revised 27 July 2014Accepted 30 July 2014

Recently, various biochip environments have been presented. In this study, a novel transparent film with porous membrane windows, which is an essential component in a co-cultured biochip environment, is fabricated using spin-coating, 3D printing, and electrospinning processes. In detail, a transparent polystyrene film was fabricated by means ofthe spin-coating process followed bywindow cutting, after which apolycaprolactone-chloroform solution was deposited along the window edge to introduce an adhesion layer between the PS film and the PCL nanofibers. Nanofibers were electrospun into the window region using a direct-write electrospinning method. Consequently, it was demonstrated that the fabricated window film could be used in a co-culture biochip environment. Key Words : Electrospinning(전기방사), nanofibers(나노섬유), Microfiber(마이크로섬유), Porous membrane (다공성 박막) * School of Mechanical Engineering, Kyungpook National University.# Corresponding Author : Young Hun Jeong School of Mechanical Engineering, Kyungpook National University. E-mail : yhjeong@knu.ac.kr** School of Mechanical and Advanced Materials Engineering, UNIST. ***Department of Mechanical Engineering, Korea Polytechnic University.

Melt-electrospinning is a cost-effective and flexible process to fabricate micro-scaled polymeric fibers. Melt-electrospun microfiber structures have been receiving considerable attention from various fields due to their numerous advantages. However, the application of melt-electrospinning is limited by various factors, such as the sagging behavior and unstable whipping motion of microfibers. Here, we presented an experimental approach called beam bridge test to identify the sagging behavior of melt-electrospun microfibers for preparing 3D lattice structures with controllable architecture and well-defined pores in transverse direction. Consequently, the sagging behavior of melt-electrospun microfibers could be identified in a systematic manner. Moreover, the melt-electrospun 3D microfiber lattice structures with various grid sizes had sagging, which agreed well with the beam bridge test results. In addition, fibroblast cells (NIH-3T3) were cultured on the fabricated 3D microfiber lattice structures with various grid sizes. Cell culture results indicated that the cell growth was considerably influenced by microfiber sagging and the grid size of lattice structures. Also it was shown that the cell population for location could be controlled.

Article history: A precision linear motion table plays a crucial role in manufacturing systems used in various industries such as machine tools, semiconductors, and nanofabrication. In particular, one of the most typical mechanisms for a linear motion table is to use a ballscrew and LM guides. However, this mechanism is inevitably influenced by friction because of the relative motion in its joint regions. One of the most complex phenomena in friction is the hysteresis behavior of dynamic friction, which was compared with the steady dynamic friction that was presented using a Stribeck curve in this study. Therefore, we investigated the dynamic friction and its hysteresis behavior using a miniaturized linear table equipped with a ballscrewand LM guides that were lubricated with grease. Subsequently, it could be seen that hysteresis could be considered a time delay after zero-velocity crossing and that it was influenced by acceleration.

Al2O3 ceramic-reinforced photopolymer samples for SLA 3D printing technology were prepared using a silane coupling agent (VTES, vinyltriethoxysilane). Depending on the method used to coat the VTES onto the ceramic surface, the dispersion of ceramic particles in the photopolymer solution was remarkably improved. SEM, TEM and element mapping images showed Al2O3 particles well wrapped with VTES along with well-distributed Al2O3 particles overall on the cross-sectional surfaces of 3D-printed objects. The tensile properties (stress–strain curves) of 3D-printed objects of the ceramic-reinforced photopolymer were investigated as a function of the Al2O3 ceramic content when it ranged from 0 to 20 wt%. The results demonstrate that an Al2O3 ceramic content of 15 wt% resulted in enhanced tensile characteristics.

Fibers and fibrous structures are used extensively in various fields due to their many advantages. Microfibers, as well as nanofibers, are considered to be some of the most valuable forms of advanced materials. Accordingly, various methods for fabricating microfibers have been developed. Electrospinning is a useful fabrication method for continuous polymeric nano- and microfibers with attractive merits. However, this technique has limitations in its ability to control the geometry of fibrous structures. Herein, advanced electrospinning with direct-writing functionality was used to fabricate microfiber patterns with ivy shoot-like geometries after experimentally investigating the effects of the process conditions on the fiber formation. The surface properties of the fibers were also modified by introducing nanoscale pores through the use of higher levels of humidity during the fabrication process.

A road energy harvester was designed and fabricated to convert mechanical energy from the vehicle load to electrical energy. The road energy harvester is composed of 24 piezoelectric cantilevers and a vehicle load transfer mechanism. Applying a vehicle load transfer mechanism rather than directly installing energy harvesters under roads decreases the area of road construction and allows more energy harvesters to be installed on the side of the road. The power generation amount with respect to the vehicular velocity change was assessed by installing the vehicle load transfer mechanism and the energy harvester in the form of speed bumps and underground. The energy harvester installed in a speed bump form generated power of 7.61 mW at the vehicular velocity of 20 km/h. Also, power generation of the energy harvester installed in the underground form was 63.9 mW at the vehicular velocity of 28 km/h. Although the number of piezoelectric cantilevers was reduced by 1/3 to 24 in comparison to the previous research results with 72 piezoelectric cantilevers, similar power generation characteristic value was obtained within the vehicular velocity of 20 km/h by altering the vehicle load transfer mechanism and cantilever vibration method.

In recent times, simulation techniques have been rapidly accepted by the machine tool industry. However, most existing simulation studies have focused on a particular machine tool and described an entire machine tool feed drive as a single combined system. This paper presents a method to accurately predict motor current (torque) behavior and acquire a more generalized and accurate dynamic simulation model for a machine tool feed drive. To improve the generality, a component-based approach is introduced. In this approach, the feed drive model is composed of subcomponent models, and each component mechanism is then independently modeled. In the developed model structure, the parameters of the subcomponent model can easily be determined by using product datasheets or simple parameter identification based on motor current measurements. To enhance the model accuracy in predicting the motor current, an improved friction model including time-dependent frictional characteristics and rolling contact conditions was introduced to the simulation. The performance of the developed dynamic simulation model is demonstrated through a comparison with real machine tool behavior.

In this paper a three-dimensional geometric simulation method of micro-EDM milling processes is proposed, which introduces a Z-map algorithm to precisely represent the geometries of a machined workpiece and the evolution of the tool shape caused by tool wear during the machining. The micro-EDM milling process is mathematically and geometrically modeled. In order to verify the performance of the developed simulator, an actual square cavity is machined and compared to the simulation result. The developed EDM simulator can be used for tool path generation for tool wear compensation as well as for prediction of tool wear.

The discrete systems in a machining centre, such as the automatic tool changer and automatic pallet changer, play important roles in improving productivity in machining automation. However, system configuration and sequential logic programming still require considerable skill and are handled on a case by case basis. A simulation-based verification environment could improve system performance, reduce ramp-up time and cost, and avoid false setup and system deterioration. In this study, we developed a simulation model as well as a visualisation of a disk-type automatic tool changer (ATC) to assist with ATC mechanical design and PLC logic verification. Our simulation model was based on an object-oriented modelling approach, and consisted of model blocks corresponding to essential components such as the motor, gear set, cam-follower, and proximity sensors. We tested the model in a real-time simulation that used the software component of an actual machine tool controller in the simulation loop to evaluate the real-time calculation performance and the feasibility in a real application such as logic and configuration verification. The results related to the feed drive motion with limit sensor action in the ATC turret operation showed that our approach was practical and met the real-time requirements.

EDM is an efficient machining process for the fabrication of a micro-metal hole with various advantages resulting from its characteristics of non-contact and thermal process. However, this process has a serious problem caused by the tool wear, which significantly deteriorates the machining accuracy. In this paper, a geometric simulation model of EDM drilling process with cylindrical tool is proposed to predict the geometries of tool and drilled hole. The geometries of tool and workpiece are represented by two-dimensional matrix. For accurate prediction of their geometries, the tool motion, the sparking gap width, the spark frequency, the crater made by a single spark, and the tool wear ratio are considered as simulation parameters. To verify the simulation model the prediction results are compared with the actual experimental ones. Consequently, it is shown that the geometry prediction results match the experimental ones well within the error of 13%. Developed model can be used in offline compensation of tool wear in the fabrication of a blind hole. For the purpose of this, a compensation scheme based on the developed model is introduced, it is then demonstrated that the scheme is successfully applied to an actual micro-hole machining.

Leveling is an important part of a machine tool installation process because it significantly influences the product quality, machine tool accuracy, and machine lifetime. Conventional leveling procedures are performed by skilled engineers using leveling instruments such as spirit or electronic levels. It is difficult to monitor the level of a machine tool because an accurate leveling instrument is expensive and difficult to install. Therefore, a novel methodology for estimating the inclination angle of a machine tool feed drive is proposed in this paper to overcome the difficulties of leveling. The proposed methodology utilizes motor current measurements and a new mathematical model of the machine tool feed drive that considers the inclination. Experimental results showed that the proposed method successfully estimates the inclination angle and enhances the accuracy of the machine tool feed drive model by considering the inclination effects.

Development of a feed drive system with high speed and accuracy has been a major issue in the machine tool industry. Linear motors can be used as efficient tool to achieve the high speed and accuracy. However, a high speed feed drive system with linear motors, in turn, can generate heat problems. Also, frictional heat is produced at the ball or roller bearing of LM block when driven at high speed. It can affect the thermal deformation of the linear scale as well as that of the machine tool structure. In this paper, important heat sources and resulting thermal errors in a machine tool equipped with linear motors were investigated when it was operated at high speed. The thermal deformation characteristics were identified through measuring the thermal error caused from thermal deformation of the linear scale and the machine tool structure. The dominant thermal error components were identified from the thermal error analysis using finite element method. It was shown that the proposed analysis scheme is efficient in identifying the dominant thermal error components and its magnitudes such as the thermal expansion and movement of the linear scale, thermal deformation of the machine tool slide.

The cross-feed directional cutting force acts normal to the machined surface of a workpiece. It is important to estimate and control this force, since it directly affects the machined surface. However, using the current supplied to a stationary motor to predict the cutting state poses difficulties, because of the current's somewhat undesired behaviour. In this paper, a largely empirical approach was used to help resolve this problem. We show that the current's undesired behaviour is related to infinitesimal rotations of the motor. Subsequently, the relationship between the current and the cutting force was identified with an error of less than 15%. The predictions obtained using two machine tools with different characteristics were compared to confirm the validity of the method when investigating the characteristics of the stationary feed motor current.

The feed motor current of a machine tool contains substantial information about the machining state. The current has been used as a measure of cutting forces in much previous research; however, this indirect measurement of the cutting forces was feasible only in a low frequency range up to about 60 Hz when milling machining. In this paper, the bandwidth of the current sensor was expanded to 130 Hz. The unusual current behavior between 45 and 60 Hz was examined and analyzed. It is necessary to estimate the cross-feed directional cutting force that is normal to a machined surface, since it directly affects the error of that surface. However, because of the undesired behavior of the stationary motor current, difficulties are encountered when using it to estimate the cutting state. An empirical approach was used to resolve this problem. As a result, we show that the current is related to the infinitesimal rotations of the motor, and it is this that causes the undesired behavior of the current. Subsequently, a relationship between the current of the stationary feed motor and the cutting force normal to machined surface was identified with an error of less than 20%.

Anomalous X-ray reflectivity measurements have been performed to extract electron density profile as a function of depth. Using a model independent analysis scheme based on distorted wave Born approximation, we have demonstrated that element-specific density profiles in a film can be obtained from reflectivity measurements done at two different X-ray energies, one at an absorption edge of the corresponding metal and another one away from it. The merit of this technique has been demonstrated with the results on high dielectric constant metal oxide Ta 2 O 5 films on Si(001). Our results show different Ta profiles near interfaces for Ta 2 O 5 /Si interface and Ta 2 O 5 /SiO 2 interface, implying different kinetics at these interfaces during annealing process.

Biophysical strain has been applied widely for bone regeneration. However, application of low-magnitude strains to cells on small-thickness scaffolds is problematic, especially in rodent calvarial defect models, because general translation systems have limitations in terms of generating low-magnitude smooth signals. To overcome these limitations, we developed an in vitro biophysical-stimulation platform for stimulation of cells on small-thickness scaffolds for rodent calvarial bone defects. The customized flexure-based translational nanoactuator enables generation of low-magnitude smooth signals at the subnano- to micrometer-scale. This nanoactuator, which is equipped with a piezoelectric actuator, is suitable for biological applications because it can generate friction-free motion with a high resolution. Moreover, its operation without wear or deterioration eliminates contamination factors in cell culture environments. The developed in vitro biophysical-stimulation platform using these nanoactuators showed predictable operational characteristics. Also, a few-micrometer sinusoidal signal was generated successfully without any distortion. Three-dimensional scaffolds fitting the critical-size rat calvarial defect model were fabricated using poly(caprolactone), poly(lactic-co-glycolic acid), and tricalcium phosphate. Runt-related transcription factor 2 expression was increased upon stimulation of human adipose-derived stem cells (ASCs) on these scaffolds were stimulated in the in vitro biophysical-stimulation platform. Additionally, the use of this platform resulted in up-regulation of alkaline phosphate, osteopontin, and osterix expression compared to the non-stimulated group. These preliminary in vitro results suggest that the biophysical environment provided by the in vitro biophysical-stimulation platform influences the osteogenic differentiation of ASCs.

In this paper we discuss a self-calibration technique for a dual-actuated, single-axis nanopositioner and extend ideas from this method to develop a calibration technique for a two-axis system. The proposed methods exploit concepts of measurement transitivity and redundancy that are will established in self-calibration theory. The developed method has been applied to a dual-actuated single-axis nanopositioner equipped with capacitive displacement sensors with a calibration error in the sub-nanometer range. For the two-axis system, the technique uses a right angle prism as an artifact to calibrate two orthogonal axes. Transitivity between the axes is obtained through the use of a redundant or 'dummy' uncalibrated sensor that maintains the hypotenuse of the right angle prism invariant during sets of measurements. Because, the approach relies on the accuracy of the prism, it cannot be considered to be a self-calibration technique. Nevertheless, experiments indicate that it calibrates a two-axis stage to within 1 nm of the prism.

Because electrode wear in microelectrical discharge machining significantly deteriorates the machining accuracy, the electrode wear must be compensated in process to improve the geometric accuracy of the product. Therefore, there has been a substantial amount of research on electrode wear and the compensation for EDM processes. In this study, a novel control method for a micro-EDM process using discharge pulse counting is proposed. The method is based on the proportional relationship between the removed workpiece volume and the number of discharge pulses. A model-based control was designed using the relationship between the pulse frequency and gap distance, and implemented in an actual micro-EDM system. Experimental results demonstrated that the developed method makes two- and three-dimensional micro-EDM milling processes fast and accurate without complex path planning to compensate electrode wear.

Gastrointestinal tuberculosis that is not an unusual form of extrapulmonary tuberculosis and it is usually associated with immunocompromised condition that may present with clinical symptoms including fever, weight loss or pain. Terminal ileum and cecum are the common sites of involvement, but involvement of the stomach is rare. Furthermore, synchronous tuberculosis involving both the stomach and lower gastrointestinal tract has been reported in very few cases. Herein, we report a case of incidentally detected synchronous tuberculosis involving both the stomach and terminal ileum that was successfully treated by antituberculosis therapy in an asymptomatic immunocompetent patient.

Recently, liquid crystal displays (LCDs) have played vital roles in a variety of electronic devices such as televisions, cellular phones, and desktop/laptop monitors because of their enhanced volume, performance, and functionality. However, there is still a need for thinner LCD panels due to the trend of miniaturization in electronic applications. Thus, chip-on-glass (COG) bonding has become one of the most important aspects in the LCD panel manufacturing process. In this study, a novel sensor was developed to measure the parallelism between the tooltip planes of the bonding head and the backup of the COG main bonder, which has previously been estimated by prescale pressure films in industry. The sensor developed in this study is based on a flexure mechanism, and it can measure the total pressing force and the inclination angles in two directions that satisfy the quantitative definition of parallelism. To improve the measurement accuracy, the sensor was calibrated based on the estimation of the total pressing force and the inclination angles using the least-squares method. To verify the accuracy of the sensor, the estimation results for parallelism were compared with those from prescale pressure film measurements. In addition, the influence of parallelism on the bonding quality was experimentally demonstrated. The sensor was successfully applied to the measurement of parallelism in the COG-bonding process with an accuracy of more than three times that of the conventional method using prescale pressure films.