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In corneal transplantation, 16 submillimeter-sized sutures are generated around the circular-shaped graft cornea. A major challenge in corneal transplantation is the generation of uniformly shaped sutures, where the suture shapes need to be changed depending on the patient. In this study, a corneal suturing robot that can produce sutures of the desired shape with high uniformity is described. The proposed robot manipulates the corneal tissue deformation before inserting the needle for suture shape control. A simulation using the finite element method was proposed to predict the suture shape. The suturing experiment was conducted on a porcine model, and the result was compared with the simulation. As a result, the proposed robot was able to generate sutures with a standard deviation of 108 $\mu$ m in length and 36 $\mu$ m in depth. The mean absolute error between the simulation and the experiment was 95 $\mu$ m in length and 31 $\mu$ m in depth. This is the first study to suggest a method for controlling the suture shape and quantitatively analyzing it in ophthalmic surgery.

Two-dimensional (2D) transition metal dichalcogenide (TMD) hetero PN junctions with a van der Waals (vdW) interface have received much attention, because PN diodes are basically important to control the vertical current across the junction. Interestingly, the same vdW PN junction structure can be utilized for junction field-effect transistors (JFETs) where in-plane current is controlled along the junction. However, 2D vdW JFETs seem rarely reported, despite their own advantages to achieve when good vdW junction is secured. Here, we present high-performance p-MoTe2 JFETs using almost perfect vdW organic Alq3/p-MoTe2 junctions and demonstrate organic NPB/n-MoS2 JFETs. The p- and n-channel JFETs stably show high mobilities of 60-80 and ∼800 cm2/V s, respectively, along with a high ON/OFF current ratio (>1 × 105) and minimal gate leakage at 5 V even after a few months. Such performances are attributed to a quality vdW junction at organic layer/TMD interfaces.

In this paper, dry turning operation was carried out on four types of workpiece materials SCM420, SCM420H, SCM440 and SM45C in order to review the effect of cutting parameters on surface roughness (Ra) and resulting cutting force (F). The turning operation was conducted on the NC lathe with the CVD coated carbide inserts. The analysis of variance (ANOVA), linear regression model and main effect plot for mean were employed to investigate the correlation between responses (Ra and F) and cutting parameters. The predictive equations showed a satisfactory correlation with high coefficients of determination (R2) from 80.76 to 98.89%. The lowest feed rate and highest spindle speed were applied to minimize surface roughness, but both were performed at level 1 to minimize the resulting cutting force. The optimal experimental conditions showed the brilliant results as the surface roughness 1 μm and resulting cutting force 39.92 N. The SCM440 steel indicated the best surface roughness responses followed by SCM420, SCM420H and SM45C steel. The SCM440 steel revealed the lowest resulting cutting force followed by SCM420, SM45C and SCM420H steel.

Very recently, stacked two-dimensional materials are studied, focusing on the van der Waals interaction at their stack junction interface. Here, we report field effect transistors (FETs) with stack...

The main objective of the study is to analyze the various cutting parameters to investigate the surface quality of the minor scale diameter of magnesium alloy in the dry turning process using a different tool nose radius (r). The surface roughness (Ra) was gauged, and micro-images produced by scanning electron microscopy (SEM) were reviewed to evaluate the machined surface topography. The analysis of variance (ANOVA), linear regression model and signal-to-noise (S/N) ratio were applied to investigate and optimize the experimental conditions for surface roughness. The study results imply that the feed rate and tool nose radius significantly affected the surface quality, but the spindle speed did not. The linear regression model is valid to forecast the surface roughness. The cutting parameters for optimum surface quality are a combination of a spindle speed of 710 rpm, a feed rate of 0.052 mm/rev and a tool nose radius of 1.2 mm. The machined surface topography contains the feed marks, micro-voids, material side and material debris, but they become smaller and decrease at a lower feed rate, larger tool nose radius and higher spindle speed. These results show the good surface quality of magnesium alloys in a dry turning process, which could be applied in implant, orthopedic and trauma surgery.

Very recently, stacked two-dimensional materials have been studied, focusing on the van der Waals interaction at their stack junction interface. Here, we report field effect transistors (FETs) with stacked transition metal dichalcogenide (TMD) channels, where the heterojunction interface between two TMDs appears useful for nonvolatile or neuromorphic memory FETs. A few nanometer-thin WSe

Two-dimensional (2D) transition metal dichalcogenides (TMDs)-based van der Waals (vdW) PN junctions have been used for heterojunction diodes, which basically utilize out-of-plane current across the junction interface. In fact, the same vdW PN junction structure can be utilized for another important device application, junction field effect transistors (JFETs), where in-plane current is possible along with 2D–2D heterojunction interface. Moreover, the 2D TMD-based JFET can use both p- and n-channel for low voltage operation, which might be its unique feature. Here we report vdW JFETs as an in-plane current device with heterojunction between semiconducting p- and n-TMDs. Since this vdW JFET would have low-density traps at the vdW interface unlike 2D TMD-based metal insulator semiconductor field effect transistors (MISFETs), little hysteresis of 0.0–0.1 V and best subthreshold swing of ~100 mV/dec were achieved. Easy saturation was observed either from n-channel or p-channel JFET as another advantage over 2D MISFETs, exhibiting early pinch-off at ~1 V. Operational gate voltage for threshold was near 0 V and our highest mobility reaches to ~>500 cm2/V·s for n-channel JFET with MoS2 channel. For 1 V JFET operation, our best ON/OFF current ratio was observed to be ~104. Van der Waals heterostructures of atomically thin semiconductors enable junction field effect transistors (JFETs). A team led by Seongil Im at Yonsei University fabricated JFETs using a heterojunction of semiconducting p-MoTe2 (or p-WSe2) and n-MoS2. The p-type transition metal dichalcogenide (TMDC) works as a gate for the n-type TMDC channel, whereas the n-type TMDC operates as a gate for the p-type TMDC channel. Owing to the low density of traps at the van der Waals interface, the devices exhibit low hysteresis of 0.05–0.1 V and achieve a subthreshold swing of ~100 mV/decade. The highest mobility reaches 500 cm2/V·s for the n-channel JFET with MoS2, whereas the p-channel JFET with MoTe2 is characterized by a much lower mobility of ~13 cm2/V·s. The highest ON/OFF current ratio was observed to be >104.

It is safe and light because it uses carbon/glass fiber reinforced plastics (hereinafter referred to as C/GFRP) through this technological development. Moreover, sunlight LED luminous bollard, which was harmonized with the surrounding environment with diverse colors, was developed. Luminous bollard can reduce its weight and also increase its strength by adjusting the intensity and thickness of a product customized for each usage on the basis of the characteristics of C/GFRP composite. In addition, C/GFRP and steel pipe were compared for the compression test in order to compare the objective rigidity. As a result, this study could obtain a positive result graph of luminous bollard. To develop luminous bollard, the composite development process was configured through a fixture of pullout and filament winding. Diverse colors can be applied to luminous bollard. Hence, it is possible to select a color customized for each region. It is also possible to create an aesthetic harmony with a surrounding environment through LED lamps at night. The pipe, which was 50 percent lighter than stainless and also which had excellent tensile strength, was designed to develop the bollard that has superior convenience in terms of construction, maintenance and repair.

Keratoplasty is the surgery that replace the diseased cornea to the new donor cornea. Keratoplasty requires about 16 sutures with deep and regular suture depth. However controlling suture depth is difficult because of lack of depth information in microscope image, high transparency and thin thickness of the cornea. In this paper, we proposed sensor embedded surgical forceps which can automatically grasp the cornea with desired depth. The sensor can detect the moment that the forceps tip reaches to the desired suture depth. The sensor and the automatic grasping device was fabricated and preliminary experiment was conducted to investigate the feasibility of the device.

A van der Waals (vdW) Schottky junction between two-dimensional (2D) transition metal dichalcogenides (TMDs) is introduced here for both vertical and in-plane current devices: Schottky diodes and metal semiconductor field-effect transistors (MESFETs). The Schottky barrier between conducting NbS

Article history: Due to recent industrial growth and development, there has been a high demand for light and highly durable materials. Therefore, a variety of new materials has been developed. These new materials include carbon fiber reinforced plastic (CFRP or CRP), which is a wear-, fatigue-, heat-, and corrosion-resistant material. Because of its advantageous properties, CFRP is widely used in diverse fields including sporting goods, electronic parts, and medical supplies, as well as aerospace, automobile, and ship materials. However, this new material has several problems, such as delamination around the inlet and outlet holes at drilling, fiber separation, and tearing on the drilled surface. Moreover, drill chips having a fine particulate shape are harmful to the work environment and engineers’ health. In fact, they deeply penetrate into machine tools, causing the reduction of lifespan and performance degradation. In this study, CFRP woven and unidirectional prepregs were formed at 45° and 90°, respectively, in terms of orientation angle. Using a high-speed steel drill and a TiAIN-coated drill, the two materials were tested in three categories: cutting force with respect to RPM and feed speed; shape changes around the input and outlet holes; and the shape of drill chips.

The cutting characteristics of biomaterials (Ti-6Al-4V ELI) by tools are investigated with respect to cutting force, work piece surface roughness and tool flank wear by the vision system. Ti-6Al-4V ELI titanium turning is carried out with various cutting conditions; spindle rotational speed and feed rate. Back propagation neural networks (BPNs) are used for detection of tool wear. The input vectors of neural network comprise of spindle rotational speed, feed rates, vision flank wear, and cutting force signals. The output is the tool wear state which is either usable or failure. The detection of the abnormal states using BPNs achieves 97.5% reliability even when the spindle rotational speed and feed rate are changed.

Corneal suturing in keratoplasty is a difficult task due to its high precision and regularity requirements. A robot-assisted microsurgical technique could bring a better prognosis therefore investigation of the suturing motion is an essential preliminary study. Total 20 corneal sutures were performed on porcine eyes manually and the suturing motion was recorded by a haptic device. The needle tip trajectory was projected to a plane using PCA. Cross sectional images of suture outcome were acquired using the OCT(Optical Coherence Tomography) system. The characteristics in manual suturing motion were analyzed. However, finding a distinct relationship between the suture motion input and the suture outcome was limited. A microsurgical suturing robot will be developed in the future based on this work

New materials widely used for automobile related industry, aircraft, space development area are mostly high hardness materials. The hardness value of some hardened materials is over HRC45 and machining of this hardened materials is called as hard turning. Hard turning has its advantage on processing flexibility, cycle time and tool cost reduction. Also this process obtains high efficiency in processing and precise surface roughness through application of the CBN tools. In hard turning process with CBN tool, surface integrity is the important factor for considering the design of machine part and component under high stress and load conditions. A purpose of this study is to analyze optimal condition in hard turning process of AISI 52100 steel (HRC62) with high CBN and low CBN on turning characteristics, tool wear mechanism comparison and surface integrity.

We have fabricated van der Waals (vdW) Schottky junction between high work function conducting NbS2 transition metal dichalcogenide (TMD) and semiconducting n-MoS2 TMD for metal semiconductor field effect transistors (MESFETs). The Schottky barrier between NbS2 and MoS2 appeared as large as ~0.5 eV due to their work function difference, as measured by scanning Kelvin probe. Schottky effect MESFET operates with a low threshold gate voltage of -0.5 ~ -1 V exhibiting easy saturation. Since this FET contains low density traps at the vdW interface, little gate hysteresis and ideal subthreshold swing of 60~80 mV/dec are expected. In addition, source/drain (S/D) contact for n-channel MoS2 could significantly affect device mobility. In the case of the graphene S/D contact, the device shows the highest mobility of more than 800 cm2/V s, although the device shows the lowest mobility of ~15 cm2/V s in the case of Au/MoS2 contact without an annealing process. TMD-based MESFET with NbS2/n-MoS2 junction is considered novel and promising in future 2D device electronics.