• Korean Journal of Materials Research
• /
• v.14 no.4
• /
• pp.293-299
• /
• 2004

Transition metal ions doped $TiO_2$ nanostructured powders were prepared with simply heating aqueous $TiOCl_2$ solutions, contained various metal ions (Ni, Al, Fe, Zr, and Nb) of 1.47 mol% added as metal-chlorides, at $100^{\circ}C$ for 4 hrs by homogeneous precipitation process under suppressing conditions of water vaporization. The characterizations for prepared $TiO_2$ powders were carried out to observe doping of metal ions, their concentrations and microstructures using XRD, UV-VIS (DRS), XPS, SEM, TEM and ICP. Also, photo-oxidative abilities were evaluated by decomposition of 4-chlorophenol (4CP) under ultraviolet light irradiations. No secondary oxide phases were formed in all the $VTiO_2$ powders, showing doping with various transition metal ions. When adding ions ($Ni^{2+}$ or$ Al^{3+ }$ and $Zr^{4+}$ ) having valance states or ionic radii greatly different from those of $Ti^{4+}$ , the $TiO_2$ powders of mixed anatase and rutile phases were formed, whereas in the case of additions of $^Fe{3+ }$ and $Nb^{ 5+}$ as well as no addition of metal ion the powders with pure rutile phase alone were formed. Among the prepared $TiO_2$ powders, Ni$^{2+}$ doped $TiO_2$ powders, containing a small amount of anatase phase, showed excellent photo-oxidative ability in 4CP decomposition because of relative decreases in electron-hole recombination and poisoning of $TiO_2$ surface during the photoreaction.n.

• Journal of the Korean Institute of Gas
• /
• v.15 no.2
• /
• pp.69-74
• /
• 2011

As a way to propose a method for the establishment of practical damage-minimizing plan for chemical plants, the release scenario was established by using API-581 BRD and the effect zone was estimated by the KS-RBI program supporting the quantitative cause analysis. And the risk assessment was performed. As a result, we found that to minimize the damage of a chemical plant, it is effective to use four release hole diameters (small, medium, large and rupture) and release time estimated according to the classes of detection and isolation systems. In addition, it can be safely said that through appling the damage areas considering weighted average by failure frequency and worst-case simultaneously, industrial sites can come up with the effective emergency response plan.

• Journal of the Korean Society of Costume
• /
• v.57 no.8
• /
• pp.37-47
• /
• 2007

This study is considered about the fabrics of the tomb of King Muryeong at the Baekje(百濟) Period. First, there were silk fabrics such as compound woven silk(錦), twill damask(綾), complex gause(羅) and plain weaved silk(平絹). All of compound woven silk(錦) are the warp-faced compound tabby(經錦) of plain weave and the density is various from high to low one. The twill damask(綾) was a variation of twill damask weaved with a six strand warp thread. The complex gause(羅) made patterns as a set of 2 strand, 4 strand, 6 strand and 8 strand warp threads are weaved alternately with the weft. There were three kinds of plain weaved silk(平絹). The first was weaved densely without space between strands. The second was weaved with a small space between strands. And the third was weaved with a two strand warp thread, having a space between the threads. On the other hand, several pieces of well preserved ramie cloth were excavated. Of the, the densest one has the density of 125 strand/inch for the warp and the weft. In addition, strings made of flax thread were found. This suggests that flax fabrics may be found additionally if the hardened lumps of fabrics are resolved and analyzed. Other materials discovered include knits, knotted strings, embroideries, threads and floss. Pieces considered knits and knotted strings occupy a large part of fabrics excavated from King Muryeong's Tomb, and in particular knotted strings show various knotting methods. In addition, embroideries such as chain stitch and button hole stitch are clearly observed. What is more, there are silk threads and hemp threads, which are presumed to have been used for dangling ornaments such as Yeongrak(瓔珞) and beads or for sewing. Besides, floss was found between fabrics.

• Korean Journal of Applied Biomechanics
• /
• v.20 no.4
• /
• pp.447-455
• /
• 2010

The objective of this study was to analyze the difference in kinematic variables for successful and unsuccessful golf putting strokes. The study population included 8 male secondary school golf players who had played golf for over 3 years and whose handicap was 4 or lower. A hole was made on a 5-m-long artificial flat mat for practice, and an environment similar to that of a real green was created. The participants' motions were analyzed through 3D image analysis, and the difference in kinematic variables for successful and unsuccessful putting strokes in the same direction was determined. Data analysis revealed the following findings: The time spent for a segment of putting was the greatest for the backswing segment for both successful and unsuccessful strokes. During address and impact, the both changed to a larger extent. For successful putting strokes, the change in the elbow angle during the downswing was greater for the right elbow than for the left elbow. For both successful and unsuccessful putting strokes, the left shoulder angle increased during the segment from address to the turning point and decreased during the segment from the turning point to impact. In contrast, the right shoulder angle significantly differed between successful and unsuccessful putting strokes only during address. During successful and unsuccessful motions, the swing was executed with the moving displacement of the X-axis of the club head maintained almost constant along a straight light without back and forth movement. In the backswing segment, moving displacement of the Y- and Z-axes was greater in successful strokes than in unsuccessful strokes; however, this difference was very small for the Y-axis. The velocity of the club head for successful and unsuccessful motions significantly differed during address and at the turning point. The highest velocity of the ball was greater for successful than for unsuccessful putting strokes.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.12
• /
• pp.152-158
• /
• 2001

In this paper, we have developed an electro discharge machine for micro drilling driven by a voice coil actuator. Because the voltage signal of the electro-discharging circuit shows a lot of peaks and valleys, the active type low-pass filtering technique is adopted to get the average of the signal. Since the motion of the voice coil is precisely controlled by the error value between the object voltage value and the measured one, it is possible to prevent the mechanical contact between the rotating electrode and the workpiece and to maintain the appropriate machining conditions during the process. The electro-chemical machining technology was also adopted to make small diameter electrodes. Pure water is used as a dielectric. The machining procedure is performed to verify the feasibility of the developed system. It takes about 10 seconds to drill the ${\phi}m$100${\mu}m$ hole to the 100${\mu}m$ thickness stainless steel plate. The machining time depends on the values of the resister and the capacitor. There may exist the optimal values of time constant and the tendency is displayed In the appendix.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.782-787
• /
• 2005

The bottom structure of an instrumented capsule is a part which is joined at the receptacle of the flow tube in the reactor in-core. A geometrical change or the bottom structure has an effect on the pressure drop and the vibration of the capsule. The out-pile test to evaluate the structural Integrity of the material capsule called 04M-l7U was performed by using a single channel and a half core test loop. From the pressure drop test, the optimized diameter of the cone shape's bottom structure which satisfies HANARO's flow requirement (19 6 kg/s) is 71 mm. The maximum displacement of the capsule measured at the half core test loop is lower than 1.0 mm. From the analysis results, it is found that the test hole will not be interfered with near the flow tubes because its displacement due to the cooling water is very small at 0.072 mm. The fundamental frequency of the capsule under water is 9.64 Hz. It is expected that the resonance between the capsule and the fluid flow due to the cooling water in HANARO's In-core will not occur. Also, the new bottom structure of a solid cone shape with 71 mm in diameter will be applicable to the material and special capsules in the future.

• Applied Chemistry for Engineering
• /
• v.9 no.5
• /
• pp.674-679
• /
• 1998

Small water leak experiment was carried out in liquid sodium atmosphere using a specimen of ferrite steel, which will be expected to be a material of the heat transfer tube of liquid metal fast breeder reactor. Self-plugging phenomena of leak path could be explained by the products of reaction and corrosion by sodium-water reaction. Also, re-opening mechanism of self-plugged path could be explained by the thermal transient and vibration of heat transfer tube. As a result, perfect re-opening time of self-plugged leak path was observed to be 129 minutes after water leak initiation. Re-opening shape of a specimen was appeared with double layer of circular type, and re-opening size of this specimen surface was about 2 mm diameter on sodium side.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2012.05a
• /
• pp.63-64
• /
• 2012

A pyrotechnic actuated device (PAD) is a component that delivers high power in remote environments by combustion of a self-contained energy source. Historically, the design of these devices has been largely empirical and considered to be an art. In this study, an overview for developing an analytical model is introduced that efficiently evaluates performance of PAD. The model is integrated by three parts of different disciplines that are coupled in sequence with each other. First is the solid explosive burning to form product gas within an actuator and transport to an expansion chamber. Second is the insertion of initially tapered piston into a small hole by gas pressure in the chamber. Third is the shear cutting of the diaphragm from the piston to enable gas flow into the conduit. Some results of preliminary study for each of three parts are introduced in the presentation.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.13 no.2
• /
• pp.64-76
• /
• 2009

Experimental and numerical studies are conducted on the characteristics of flame extinction and edge flame oscillation in counterflow diffusion flames. The characteristics of flame extinction and edge flame oscillation are well described varying burner diameter, separation distance between two burners, global strain rate, and velocity ratio. It is verified numerically and experimentally that radial conduction heat loss significantly contributes to flame extinction and edge flame oscillation at low strain rate flames in zero- and micro-gravity. It is also shown that for appropriately small burner diameters flame extinction modes are grouped into four and these are significantly attributed to excessive radial conduction heat loss. The edge flame oscillation can be characterized well by one curve with Strouhal number and Peclet number.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.2
• /
• pp.96-107
• /
• 2018

Flow analysis using computational fluid dynamics was conducted to investigate the effect of the igniter flame caused by the gap between the igniter and the propellant grain in a solid rocket motor. Two propellant grain types were assumed; namely cylinder type (1 mm, 3 mm, and 5 mm gap) and the slot type. The slot type had two igniter hole locations. One was located at the small gap of the propellant grain, and the other one was located at the large gap. In the case of the cylinder type, the pressure in the igniter zone was higher with a thinner gap. Additionally, in the case of the cylinder type, the pressure difference between the igniter installed zone and the free volume was also higher as the gap became lower. The cylinder types were affected by the gap distance, but the slot types were not. Moreover, the results of the slot types were similar to the 5-mm gap case of the cylinder type.