• Progress in Superconductivity
• /
• 제3권2호
• /
• pp.146-150
• /
• 2002

We performed the point contact spectroscopy on newly discovered superconductor $MgB_2$ thin films with Au tip. In the point contact spectroscopy of the metallic Sharvin limit, the differential conductance below the gap is twice as that above the gap by virtue of Andreev Reflection. After some surface cleaning processes of sample preparation such as ion-milling and wet etching, the obtained dI/dV versus voltage curves are relatively well fitted to the Blonder-Tinkham-Klapwijk (BTK) formalism. Gaps determined by this technique were distributed in the range of 3meV~ 8meV with the BCS value of 5.9meV in the weak coupling limit. We attribute these discrepancies to the symmetry of the gap parameter and the degradation of the surface of the sample. We also present the temperature dependence of the conductance vs voltage curve and thereby the temperature dependence of the gap.

• 전기학회논문지
• /
• 제64권4호
• /
• pp.592-597
• /
• 2015

3D-IC is a novel semiconductor packaging technique stacking dies to improve the performance as well as the overall size. TSV is ideal for 3D-IC because it is convenient for stacking and excellent in electrical characteristics. However, due to high-density and micro-size of TSVs, they should be tested with a non-invasive manner. Thus, we introduce a TSV test method on test prober without a direct contact in this paper. A capacitive coupling effect between a probe tip and TSV is used to discriminate small TSV faults like voids and pin-holes. Through EM simulation, we can verify the size of eye-patterns with various frequencies is good for TSV test tools and non-contact test will be promising.

• Archives of Plastic Surgery
• /
• 제37권5호
• /
• pp.671-675
• /
• 2010

Purpose: In order to maintain corrected nasal tip projection, strong support is important. Authors used calvarial bone graft method for this purpose. Patients were followed up about permanency of the bone graft for a long time. Methods: From 1995 to 1998, author performed calvarial bone graft on 30 adult patients with secondary cleft lip and nose deformity. Patients were observed for 34 months. There were no specific complications, and results were satisfactory. We could confirm the permanence of the calvarial bone graft in 3 patients by photography and radiologic studies for 10 years follow-up. Results: None of the patients showed size change or displacement. But the portion of graft facing the tip was absorbed resulting in loss of tip projection and short nose in two patients. One patient had fracture on the middle of the graft. This caused depression from lower portion of the dorsum to the tip. Conclusion: Despite of autogenous grafts such as calvarial bone, absorption of the bone may occur when compressed with tension for a long period. And the graft in the nasal tip not having any contact with the nasal bone may cause absorption of the graft.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2009년도 추계학술대회 논문집
• /
• pp.317-318
• /
• 2009

• 대한기계학회논문집A
• /
• 제29권8호
• /
• pp.1078-1084
• /
• 2005

The relationship between fatigue crack opening behavior and the reversed plastic zone sizes is studied. An elastic-plastic finite element analysis (FEA) is performed to examine the opening behavior of fatigue crack, where the contact elements are used in the mesh of the track tip area. The smaller element size than reversed plastic zone size is used fer evaluating the distribution of reversed plastic zone. In the author's previous results the FEA could predict the crack opening level, which crack tip elements were in proportion to the theoretical reversed plastic zone size. It is found that the calculated reversed plastic zone size is related to the theoretical reversed plastic zone size and crack opening level. The calculated reversed plastic zone sizes are almost equal to the reversed plastic zone considering crack opening level obtained by experimental results. It can be possible to predict the crack opening level from the reversed plastic zone size calculated by finite element method. We find that the experimental crack opening levels correspond with the opening values of contact nodes on the calculated reversed plastic zone of finite element simulation.

• 정보저장시스템학회:학술대회논문집
• /
• 정보저장시스템학회 2005년도 추계학술대회 논문집
• /
• pp.185-189
• /
• 2005

We reported here nano-scale electrical phase-change recording in amorphous $Ge_2Sb_2Te_5$ media using an atomic force microscope (AFM) having conducting probes. In recording process, a pulse voltage is applied to the conductive probe that touches the media surface to change locally the electrical resistivity of a film. However, in contact operation, tip/media wear and contamination could major obstacles, which degraded SNR, reproducibility, and lifetime. In order to overcome tip/media wear and contamination in contact mode operation, we adopted the W incorporated diamond-like carbon (W-DLC) films as a protective layer. Optimized mutilayer media were prepared by a hybrid deposition system of PECVD and RF magnetron sputtering. When suitable electrical pulses were applied to media through the conducting probe, it was observed that data bits as small as 25 nm in diameter have been written and read with good reproducibility, which corresponds to a data density of $1 Tbit/inch^2$. We concluded that stable electrical phase-change recording was possible mainly due to W-DLC layer, which played a role not only capping layer but also resistive layer.

• 대한화학회지
• /
• 제61권1호
• /
• pp.12-15
• /
• 2017

We presented a mapping the work function of the vanadium pentoxide ($V_2O_5$) nanonet structures by scanning Kelvin probe microscopy (SKPM). In this measurement, the $V_2O_5$ nanonet was self-assembled via dropping the solution of $V_2O_5$ nanowires (NWs) onto the $SiO_2$ substrate and drying the solvent, resulting in the networks of $V_2O_5$ NWs. We found that the SKPM signal as a surface potential of $V_2O_5$ nanonet is attributed to the contact potential difference (CPD) between the work functions of the metal tip and the $V_2O_5$ nanonet. We generated the histograms of the CPD signals obtained from the SKPM mapping of the $V_2O_5$ nanonet as well as the highly ordered pyrolytic graphite (HOPG) which is used as a reference for the calibration of the SKPM tip. By using the histogram peaks of the CPD signals, we successfully estimated the work function of ~5.1 eV for the $V_2O_5$ nanonet structures. This work provides a possibility of a nanometer-scale imaging of the work function of the various nanostructures and helps to understand the electrical characteristics of the future electronic devices.

• Journal of Mechanical Science and Technology
• /
• 제16권8호
• /
• pp.1117-1126
• /
• 2002

A conducting crack in an electrostrictive ceramic under combined electric and mechanical loading is investigated. Analysis based on linear dielectric model predicts that the surfaces of the crack are not open completely but they are contact near the crack tip. The complete solution for the crack with a contact zone in a linear electrostrictive ceramic under combined electric and mechanical loading is obtained by using the complex variable formula. The asymptotic problems for a semi-infinite crack with a partial opening zone as well as for a fully open semi-infinite crack in a nonlinear electrostrictive ceramic are analyzed in order to investigate the effect of the electrical nonlinearity on the stress intensity factor under small scale nonlinear conditions. Particular attention is devoted to a finite crack in the nonlinear electrostrictive ceramic subjected to combined electric and mechanical loading. The stress intensity factor for the finite crack under small scale nonlinear conditions is obtained from the asymptotic analysis.

• Journal of Welding and Joining
• /
• 제14권5호
• /
• pp.87-94
• /
• 1996

It has been well known in GMA welding process that wire feeding speed (WFS) or deposition rate increases linealy with the increase of wire extension. In this investigation, however, such an well-known relationship was .reconsidered in terms of contact-tube to work distance (CTWD) instead of wire extension. To verify the proposed relationship between WFS and CTWD, bead-on-plate welding was performed with various CTWDs in the range of 15∼35mm under the condition of near-constant voltage and current As expected, the test results showed an excellent linear relation between WFS and CTWD. Furthermore, the value of the slope turned out to be quite similar to those of previous investigators obtained either theoretically or experimentally through the Precise measurement of electrode extension. Present result also demonstred that the increase of CTWD could be very practical measure for increaring deposition rate without any increase of heat input Depending on the tip recess the practical maximum of CTWD was appeared to be limited somewhere in 25∼30mm mainly due to the entrappment of porocity.

• 소성∙가공
• /
• 제29권3호
• /
• pp.144-150
• /
• 2020

In this paper, we propose the generation of a double enveloping worm thread profile with a non-developable ruled surface. Thread surface machining cuts all the way from the tip to the tooth root at one time, like full-face contact machining, rather than cutting several times like point machining. This cutting can reduce the cutting duration and achieve the smooth surface that does not require a grinding process for the threaded surface. The mathematical model of the cutting process was developed from theoretical equations, and the tooth surface was generated using two parameters and modeled in the CATIA using the generated Excel data. Additionally, the machining process of the worm was simulated in a numerical control simulation system. To verify the validity of the proposed method, the deviation between the modeling and the workpiece was measured using a 3D measuring machine.