• Korean Journal of Human Ecology
• /
• v.5 no.2
• /
• pp.55-74
• /
• 2002

This study, observing each respectively packaged Kongdduk during 12-day storing period and comparing it with unpackaged Kongdduk, through a cross-sectional view of its fiber and temperament, through a sensory evaluation rheometer measurement of rheological change depending on storing period and packaging type and through the organic acid content, micro-organic change, and retrogressive process. The results are as follows: 1. Kongdduk made of bean oil shows better chewiness, cohesiveness, and moistness than Kongdduk made of bean flour while Kongdduk made of bean flour shows better rheological properties as to roasted nutty taste or roasted nutty order. 2. The test of the cutted loaves of Kongdduk shows that adding oil of proper proportion to the dough of steamed rice cake in accordance with the amount of rice flour has a good influence on rheological properties of softness. 3. Rice cakes were prepared by addition of yellow soybean flour or peanut flour and packaged with CMP or VP, and their physical characteristics were monitored by sensory evaluation and mechanical measurement while storing for 6 days. For VP samples, yellow soybean rice cake showed little changes in cohesiveness, moistness and chewiness for 6 days of storage, while pure rice cake and peanut rice cake showed an increase in strength and hardness from the 4th day of storage. In case of CMP, yellow soybean rice cake hardly showed a difference in cohesiveness, moistness and chewiness for 6 days, while pure rice cake and peanut rice cake showed a significant difference from the 4th day in sensory evaluation. 4. For rheometer measurement, yellow soybean rice cake with CMP or VP showed little changes in strength or hardness for 6 days, while peanut rice cake and pure rice cake showed a drastic decrease in cohesiveness, from the End day and adhesiveness from the 4th day of storage. As there was no remarkable difference or deterioration for 6 days of storage in yellow soybean rice cake between CMP and VP, the ingredients of rice cakeappeared to be more important than the type of packaging in terms of quality deterioration of rice cake. 5. As the storing period passed by, organic acid is detected less at CMP-packaged Knngdduk than at wrapped. and its increasing speed proves to be slower as well. 6. The one wrapped with plyethylene film began to get moldy from pure rice cake or Kongdduk (rice cake mixed with yellow soybean or peanut) after 6 days, and more and more modly after 9 daysor after 12 days, but the CMP-packaged ones didn't get modly until 12 days or more. 7. CMP-packaged Kongdduk showed higher enthalpy of retrogradation than PE-wrapped one. As storing Period Passed by, Kongdduk,s enthalpy grew high. That is to say, it shows that Kongdduk got retrograded.

• Journal of the Korean institute of surface engineering
• /
• v.40 no.6
• /
• pp.254-257
• /
• 2007

TiN coating on tool steel has been widely used for the improvement of durability of tools. In this work, radical nitriding(RN) is carried out on SKD61 at $450^{\circ}C$ for 5 hours in the ammonia gas pressure $2.7{\times}10^3\;Pa$. The TiN coating is carried out by arc ion plating(AIP) with the process parameters: arc power 150 A, bias voltage -50V, coating time 40 minutes and nitrogen gas pressure $4{\times}10^3\;Pa$. Hardness, elastic modulus, friction coefficient and adhesion of TiN coating on substrates of both TiN/SKD61 and TiN/RN SKD61 coatings are investigated comparatively. The primary crystalline faces of TiN surface are(200) and(111) for TiN/SKD61 and TiN/RN SKD61 respectively. In addition to the primary phase, Fe phase exists in TiN/SKD61 coating, but not in TIN/RN SKD61. The hardness of TiN/RN SKD61 is about 700 Hv, 250 Hv(56%) higher than that of TiN/SKD61 at the near interface of TiN and substrates. At the TiN surface, hardness of TiN/RN SKD61 is 2,149 Hv, 71 Hv(3%) higher than that of TiN/SKD61. The elastic modulus of TiN coating is improved to 26.7 GPa(6%) by radical nitriding. The adhesion is improved by the RN coating showing no spalling. buckling and chipping on the scratch test track which are shown on the non-RN TiN/SKD61.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.2 no.1
• /
• pp.120-127
• /
• 2006

The hammer-milled characteristics of waste wood materials such as lumber, plywood, particleboard(PB), MDF and railroad tic were investigated in this study. The physical and mechanical properties of recycled boards according to types of recycled particle and the mixing ratios were also studied. The hammer-milled, waste wood materials had the dimensional distributions suitable for the core layer panicle. Bending strengths of recycled boards (one layer) were shown in order of plywood, PB(laboratory-fabricated with particles used in the PB factory), lumber, tego film-overlaid plywood, MDF, waste railroad tie, PB(factory-made) and LPL-overlaid PB. Cured resin and creosote containing waste wood contributed to dimensional stability of reconstituted boards. Considering the mixing effects between lumber and plywood with recycled PB particle, lumber particle was contributive to bending strength, MOE and internal bond(IB) strength, whereas plywood particle was contributive to dimensional stability. The bending and IB strength of 3 layer boards composing only recycled waste wood particles in core layer of board were in order of lumber, plywood, PB and MDF. On the other hand, the thickness swelling was in order of PB, lumber, plywood and MDF. Bending strength of the 3 layer boards mixed with recycled PB-particle in the core layer had a decreasing tendency, as the mixing ratios of recycled PB-particles increased. The dimensional stability of 3 layer recycled board was improved as the mixing ratio of recycled PB-particle increased same as in one layer. Formaldehyde emission of boards fabricated with recycled PB-particles in the core layer of the PB was in the range of E2 grade (below 5.0mg/l).

• Korean Journal of Optics and Photonics
• /
• v.21 no.2
• /
• pp.61-68
• /
• 2010

Optical simulation methods were applied to the edge-lit LED backlight for LCD TV applications in order to optimize the optical structure of the light guide plate(LGP), and thus to improve the uniformity properties by removing the bright spots caused by LED's. The edge-lit LED backlight consisted of three white LED's with a lamp cover, a light guide plate, and a reflection film. When there was no pattern on the entrance side surface of the LGP, the illuminance uniformity was sensitively dependent on the distance d between the LED and the entrance surface. The illuminance uniformity increased with d but its increasing rate slowed down when d was beyond ~ 1.5 mm. When micro-patterns such as a lenticular lens array (LLA) or a serration pattern were formed on the entrance surface, the illuminance uniformity was improved substantially even for the case of very small d. At the same simulation condition, the lightguide with serration pattern showed a better uniformity than that with LLA pattern. Additional improvement could be achieved by changing the refractive index of the micro-patterns. These results suggest that using micro-patterns is a very effective way to reduce the bright spots due to their refracting function for the concentrated incident rays onto the LGP.

• The Journal of Korean Academy of Prosthodontics
• /
• v.44 no.1
• /
• pp.103-111
• /
• 2006

Statement of problem: The previous unilateral bite force recorder has several limitations for taking long time for measuring and causing discomfort to subjects. Because of these reasons, it could not use widely for epidemiological researches. However, 'Dental Prescale System' which is new equipment for measuring bite force, is more convenient for measuring bite force than previous unilateral recorder. Purpose: The purpose of this study was to compare a new technique(Dental Prescale System) using pressure sensitive foils for recording of maximal jaw closing force with conventional measurement using unilateral bite force recorder Material and method: This studies included 22 healthy dental students in college of dentistry Yonsei university in Rep of Korea. Mean age was 23.9 years. All subjects had continuous dental arches and no significant malocclusion or signs from the teeth and craniomandibular system. The Dental Prescale System (Fuji Film, Tokyo, Japan) consists of a horseshoe-shaped pressure sensitive sheet (50H, R type) and a computerized scanning system.(FPD705) We also used unilateral bite force recorder(Denbotics Co. Seoul, Rep.Korea) for comparing with Dental Prescale. Results and conclusion: The total bite force recorded with Dental Prescale System (1423 N) was systematically higher than that recorded by unilateral bite force recorder. (256 N) However, the maximum bite force values measured in the two ways were significantly correlated (r=0.46, p<0.05). The Dental Prescale bite force calculated for first molar (208 N) was lower than that recorded by unilateral bite force recorder. (256 N) The two values were also very significantly correlated. (r=0.66. p<0.001) There were significantly different in bite force between two measurement methods. The reasons were first, unilateral bite force recorder measured only the bite force of a part of teeth, and Dental Prescale measured the total teeth force. Second, in measurement, a difference in muscle contraction appeared by an extent of mouth-opening. Third, unilateral bite force recorder has the reducing effect of the bite force by protective tape. Fourth, Dental Prescale has limitations during the computer scanning procedure. Therefore, Dental Prescale System is considered to be a very promising alternative to be conventional bite force recording methods.

• Food Science and Preservation
• /
• v.16 no.5
• /
• pp.644-649
• /
• 2009

We investigated quality changes in Setoka ([Citrus unshiu$\times$Citrus sinensis]$\times$Citrus reticulate]$\times$[Citrus reticulata$\times$Citrus sinensis]) wrapped in 30-m pore size low-density polyethylene film (LDPE) and stored at different temperatures. LDPE wrapping effectively inhibited weight loss, and fruits seemed fresh even after room temperature storage. The decay rate was higher at room temperature and with LDPE wrapping. The respiration rate of LDPE- wrapped fruits was somewhat higher than that of control samples. Thus, no modified atmosphere packaging (MAP) effect was observed when 'Setoka' citrus was studied. Acidity decreased at a constant but different rate with each storage method used, and these rates were correlated with respiration rates. Soluble solid content (SSC), however, increased during 45 days of storage a subsequent rapid decrease was then observed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.9
• /
• pp.581-588
• /
• 2016

Piezoelectric thick films of a soft $Pb(Zr,Ti)O_3$ (PZT) based commercial material were produced by a conventional tape casting method. Thereafter, the interdigitated (IDT) Ag-Pd electrode pattern was printed on the $25{\mu}m$ thick piezoelectric film at room temperature. Co-firing of the 10-layer laminated piezoelectric thick films was conducted at $1,100^{\circ}C$ and $1,150^{\circ}C$ for 1 h, respectively. Piezoelectric cantilever energy harvesters were successfully fabricated using the IDT electrode pattern embedded piezoelectric laminates for 3-3 operation mode. Their energy harvesting characteristics were investigated with an excitation of 120 Hz and 1 g under various resistive loads (ranging from $10k{\Omega}$ to $200k{\Omega}$). A parabolic increase of voltage and a linear decrease of current were shown with an increase of resistive load for all the energy harvesters. In particular, a high output power of 3.64 mW at $100k{\Omega}$ was obtained from the energy harvester (sintered at $1,150^{\circ}C$).

• Korean Journal of Food Science and Technology
• /
• v.32 no.2
• /
• pp.317-322
• /
• 2000

This study examined the effect of nitrogen$(N_2)$ gas packing and ${\gamma}-oryzanol$ treatment on the shelf life of Yukwa(Korean traditional snack). Yukwa were stored with $N_2$ gas packing(AN), $N_2$ gas packing with ${\gamma}-oryzanol$ treatment(ANA), and PE film packing with air(PE) for 20 days at $60^{\circ}C$. They were evaluated by POV, AV, conjugated diene, hexanal, color and sensory characteristics. The POV, AV and conjugated diene content increased abruptly in PE and AN, but increased slowly in ANA with prolonged storage. Higher sensory scores for Yukwa were found in ANA as compared to those in PE and AN. Hexanal content, yellowness and redness in AN were higher than those in ANA and PE. The moisture content, which is supposed to be related with browning of Yukwa, was 3 times higher in AN than that in PE. Oxygen content of each Yukwa pack, even in $N_2$ gas packing, increased remarkably as storage period increased because their highly porous, fragile and syrup-coated structure resulted in incomplete degassing before $N_2$ gas was flushed into package. Consequently, $N_2$ gas packing was inefficient, but $N_2$ gas packing combined with antioxidant(such as ${\gamma}-oryzanol$) treatment was effective for the extension of shelf life of Yukwa.

• Korean Journal of Food Science and Technology
• /
• v.32 no.2
• /
• pp.341-348
• /
• 2000

Effects of different types of sub-freezing methods on quality of raw pork loin, beef loin and tuna were studied. Storage tests were undertaken as follows; the three different types of sub-freezing methods, such as regular cold chamber at $-1^{\circ}C$, air-blast sub-freezing at $-5^{\circ}C$ and sharp-plate sub-freezing at $-5^{\circ}C$, were evaluated for extending freshness of samples. Pork loin packed with polyethylene-film showed no significant differences (P<0.05) in physico-chemical properties among the above sub-freezing methods. Air-blast sub-freezing methods revealed faster evaporation of moisture from samples. The same sub-freezing method also showed increased VBN values of pork loin and tuna samples. Regular cold chamber resulted in increased TBA values and K values of beef loin and tuna, respectively. It appeared that sharp-plate freezing system kept the food samples with the least loss of freshness among the above three sub-freezing methods. These results indicated that freshness of raw pork, beef and tuna could be significantly extended by the sharp-plate sub-freezing method.

• Journal of Adhesion and Interface
• /
• v.8 no.2
• /
• pp.15-21
• /
• 2007

To prepare a natural rubber-based pressure-sensitive adhesive (PSA) for protection film of opto- functionalized sheet, natural rubber (NR) was blended with a DCPD type tackifier and three types of aliphatic hydrocarbon resins, respectively. Also, to supply low cohesion strength of NR, in the fixed ratio of tackifier, synthetic rubber, styrene-isoprene-styrene (SIS) block copolymer was blended with NR as a function of SIS contents. PSA performance of prepared PSAs was evaluated using probe tack and peel strength. Probe tack of NR/tackifier blends was increased with increasing tackifier contents, and showed maximum peak. In addition, probe tack of NR/tackifier blends slightly increased with increasing softening point of aliphatic hydrocarbon resins. Their peel strength increased up to 50 wt% of tackifier contents, but in the over contents of tackifier, they showed stick-slip failure mode. Finally, probe tack of NR/SIS/tackifier blends showed the maximum values at 20~40 wt% of tackifier contents, but at 20 wt% of tackifier contents, they showed fibrillation. For this reason, peel strength showed maximum values at 40 wt% of tackifier contents.