• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.12
• /
• pp.1027-1031
• /
• 2001

A new constant growth technique to conserve an initial grating height of V-groove AlGaAs/InGaAs quantum nanostructures above 1.0 $\mu\textrm{m}$ thickness has been successfully embodied on submicron gratings using low pressure metalorganic chemical vapor deposition. A GaAs buffer prior to an AlGaAs barrier layer on submicron gratings plays an important role in overcoming mass transport effects and improving the uniformity of gratings. Transmission electron microscopy (TEM) image shows that high-density V-groove InGaAs quantum wires (QWRs) are well confined at the bottom of gratings. The photoluminescence (PL) peak of the InGaAs QWRs is observed in the temperature range from 10 to 280 K with a relatively narrow full width at half maximum less than 40 meV at room temperature PL. The constant growth technique is an important step to realize complex optoelectronic devices such as one-step grown distributed feedback lasers and two-dimensional photonic crystal.

• Journal of Welding and Joining
• /
• v.23 no.4
• /
• pp.48-52
• /
• 2005

To estimate welding deformation for large steel structures, either experiment result with small specimen or analysis result of FEM with small numerical model is used. Consequently, it is important to decide the welding length of specimen and numerical model not to have an effect on welding deformation for accurate estimation of whole welding deformation. This study experimentally clarifies the effect of welding length on angular distortion due to welding by varying welding length of specimens, but fixing width and thickness of specimens on V-groove butt welding, fillet welding and bead on plate welding. As a resell the critical welding length on fillet welding and on bead on plate welding is over 500mm and on V-groove butt welding is over 1,000mm.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.8
• /
• pp.691-697
• /
• 2004

Experimental study is carried out to investigate the heat transport capability and thermal resistance of sinusoidal axially grooved heat pipe, comparing its performance to trapezoidal axially grooved heat pipe. As a result from this work, the heat transport capability of sinusoidal grooved heat pipe is lower than that of trapezoidal grooved heat pipe for the same size of outer diameter. As the ratio of depth to width of sinusoidal groove heat pipe is higher, the heat transport capability of heat pipe becomes higher. It is found that Aluminum-ammonia heat pipes with sinusoidal and trapezoidal grooves have good thermal resistance, below 0.1$^{\circ}C$/W at evaporator section and below 0.05$^{\circ}C$/W at condenser section.

• Journal of the Korean Magnetic Resonance Society
• /
• v.8 no.2
• /
• pp.96-107
• /
• 2004

We prepared two oligonucleotides containing same base pairing, but different base sequence in the middle region, d(CGAATTCG) and d(CGTATACG). NMR and UV absorbance data represented that such variation in base sequence could cause a significant difference in melting temperature and dynamics between d(CGAATTCG)$_2$ and d(CGTATACG)$_2$ duplexes, which are regarded to be associated with the stacked structure and the width of the minor groove of them. The latter showed poor stability compared to the former, because of poor stacking of bases. And berenil could bind to the minor groove of d(CGAATTCG)$_2$ which is relatively narrow, more strongly than d(CGTATACG)$_2$ and this gave rise to large improvement in thermal stability of the d(CGAATTCG)$_2$ duplex, compared to d(CGTATACG)$_2$.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.5 s.170
• /
• pp.37-44
• /
• 2005

In this paper, wire electrochemical machining (Wire ECM) with ultra short pulses is presented. Platinum wire with $10{\mu}m$ diameter was used as a tool and 304 stainless steel was locally dissolved by electrochemical machining in 0.1M $H_{2}SO_4$ electrolyte. Wire ECM can be easily applied to the fabrication of arbitrarily shaped micro-grooves without tool wear. The change of machining gap according to applied pulse voltage, pulse on-time and pulse period was investigated and the optimal pulse condition for stable machining was obtained. Using this method, various micro-grooves with less than $20{\mu}m$ width were fabricated.

• Journal of the Korean Society of Safety
• /
• v.13 no.4
• /
• pp.19-24
• /
• 1998

Elastic-plastic fracture toughness($J_{IC}$) by ultrasonic method is evaluated in terms of width and thickness. Widths of specimen in 6061-T6 aluminum alloy are 50mm and 100mm, thicknesses of those are 20mm and 25mm, respectively. Elastic-plastic fracture toughness by ultrasonic method is independent of specimen thickness and side groove. Angle beam probe which are placed on the end of the compact specimen detect the maximum crack extension effectively. Comparing with elastic-plastic fracture toughness by ultrasonic method and that of unloading compliance method, $J_{IC}$ of ultrasonic method are underestimated to that of unloading compliance method. Elastic-plastic fracture toughness of width 100mm specimen are underestimated to that of width 50mm specimen about 20%.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.7
• /
• pp.1280-1287
• /
• 2002

The old technique of sandblasting which has been used for decoration of glass surface has recently been developed into a powder blasting technique for brittle materials such as glass, silicon and ceramics, capable of producing micro structures larger than $100{\mu}$ m. This paper describes the performance of powder blasting technique in micro-line grooving of glass and the effect of the number of nozzle scanning on the depth and width of line groove. Experimental results showed that increasing the no. of nozzle scanning resulted in the increase of depth and width in grooves. Increase of width which may cause several problems in the precision machining results from wear of mask film. Therefore, well-controlled masking process is the most important factor for micro machining of glass with accuracy.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.5
• /
• pp.171-176
• /
• 2001

Plasma Display Panel(PDP) is a type of flat panel display utilizing the light emission produced by gas discharge. Barrier Ribs of PDP separating each sub-pixel prevents optical and electrical crosstalks from adjacent sub-pixels. Mold for forming barrier ribs has been newly researched to overcome the disadvantages of conventional manufacturing process such as screen printing, sand-blasting and photosensitive glass methods. Mold for PDP barrier ribs have stripes of micro grooves transferring glass-material wall. In this paper, Stripes of grooves of which width 48${\mu}{\textrm}{m}$ and 270${\mu}{\textrm}{m}$, depth 124${\mu}{\textrm}{m}$, pitch 274${\mu}{\textrm}{m}$ was acquired by machining hard and brittle materials of WC, Silicon, Alumina with dicing saw blade. Maximum roughness of the bottom and sidewall of the grooves was respectively 120nm, 287nm in grooving WC. Maximum tilt angle caused by difference between upper-most width and lower-most width was 2$^{\circ}$. Maximum Radius of bottom curvatures was 7.75${\mu}{\textrm}{m}$. This results satisfies the specification for barrier ribs of 50 inch XGA PDP if the groove form of mold was fully transferred to the barrier ribs. Barrier ribs were formed with Silicone rubber mold, which is transferred from grooved hard materials. Silicone rubber mold has elasticity accommodating the waveness of lower glass plate of PDP.

• The Journal of Korean Academy of Prosthodontics
• /
• v.47 no.1
• /
• pp.29-38
• /
• 2009

Statement of problem: A casting connection technique is widely used for repair, correction and addition to base metal framework. However, a casting connection technique may increase the risk of failure in clinical situations when high stresses exist. Purpose: The purpose of this study was to investigate the mechanical retentive groove design comparatively to increase the joint strength by using the three-dimensional finite element analysis model of a 3-unit fixed partial denture. Material and methods: Ten finite element models were constructed. (Model A: One retentive groove, Model B: Two retentive grooves, Model C: Three retentive grooves, Model D: Four retentive grooves, Model E: One horizontal groove and two vertical grooves, Model F: Two horizontal grooves and one vertical groove, Model G: One groove with the enlarged dimension, Model H: Two grooves with the enlarged dimension, Model I: One groove with the increased height, Model J: One groove with the increased width of base). The vertical force was applied to the mesial and the distal fossa to the casting connection of mandibular first molar. Results: The main factors, affecting joint strength of casting connection were both the retention between the primary cast and the secondary cast and the thickness of the primary cast remaining after preparing retentive groove. The increase of retentive force, according to the numbers and the dimension of retentive groove had an effect on distributing stress. However, in some cases, the increase of retentive force resulted in the increase of stress by reducing thickness of the primary cast in the connection area. Conclusion: The design of retentive groove that limits number of retentive groove for metal thickness and increases the depth of retentive groove for retention is highly recommended.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.52-55
• /
• 1997

This paper discusses an automatic visual-servoing system, in which a laser and a CCD camera are used for imaging the pattern of joint groove. The algorithm used here is simple and robust to find out the gap width and gap center. As a consequence, the speed of algorithm is very fast and optimized. A feature of this system is that it processes only by summing the vertical line and horizontal line of screen without any image preprocessing in order to get the energy information of lines alternatively. It is practical and useful for the system requiring a fast process time of vision.