• Structural Engineering and Mechanics
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• 제91권1호
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• pp.75-86
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• 2024

In this paper, the porous metal PM-35 is proposed as the filler material of filled thin-walled tubes (FTTs), and a series of experimental study is conducted to investigate the dynamic behavior and energy absorption performance of PM-35 filled thin-walled tubes under impact loading. Firstly, cylinder solid specimens of PM-35 steel are tested to investigate the impact mechanical behavior by using the Split Hopkinson pressure bar set (SHP); Secondly, the filled thin-walled tube specimens with different geometric parameters are designed and tested to investigate the feasibility of PM-35 steel applied in FTTs by the orthogonal test. According to the results of this research, it is concluded that PM-35 steel is with the excellent characteristics of high energy absorption capacity and low yield strength, which make it a potential filler material for FTTs. The micron-sizes pore structure of PM-35 is the main reason for the macroscopic mechanical behavior of PM-35 steel under impact loading, which makes the material to exhibit greater deformation when subjected to external forces and obviously improve the toughness of the material. In addition, PM-35 steel core-filled thin-wall tube has excellent energy absorption ability under high-speed impact, which shows great application potential in the anti-collision structure facilities of high-speed railway and maglev train. The parameter V0 is most sensitive to the energy absorption of FTT specimens under impact loading, and the sensitivity order of different variations to the energy absorption is loading speed V0>D/t>D/L. The loading efficiency of the FTT is affected by its different geometry, which is mainly determined by the sleeve material and the filling material, which are not sensitive to changes in loading speed V0, D/t and D/L parameters.

• 한국축산식품학회지
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• 제32권2호
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• pp.204-211
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• 2012

본 연구에서는 Arcobacter spp. 중 사람에게 위장염을 가장 빈번하게 일으키며 전 세계적으로 식육에 가장 많이 오염되어 있는 A. butzleri에 대해 자외선과 에탄올의 살균 효과를 확인하고자 하였다. $3{\times}3cm^2$ 크기의 스테인리스스틸 표면과 돈육 샘플에 각각 8 ${\log}_{10}CFU$/mL의 A. butzleri를 $200{\mu}L$씩 접종한 후 254 nm 선량으로 108-648 mWs/$cm^2$의 자외선을 조사하였다. 또한 10, 35, 70%의 에탄올에 broth 상태의 A. butzleri와 A. butzleri를 접종한 돈육을 10-30분 간 침지시키거나 에어로졸 상태로 분무 시켰다. 스테인리스스틸 표면의 A. butzleri에 자외선 조사 시 A. butzleri는 모든 자외선 선량에서 유의적으로 감소하였으나 돈육에 오염된 A. butzleri는 유의적 차이가 없거나 감소율이 매우 적은 것으로 나타났다(최고 감소량 $0.92{\pm}0.62-1.29{\pm}0.34\;{\log}_{10}CFU$/mL). 또한 broth 상태의 A. butzleri에 에탄올을 처리했을 경우 모든 농도의 에탄올에서 A. butzleri가 유의적으로 감소하였으나 식육에 오염 된 A. butzleri는 유의적인 차이가 없거나 감소율이 매우 낮은 것으로 나타났다(10% 에탄올의 최고 감소량은 $0.16{\pm}0.42-0.77{\pm}0.65\;{\log}_{10}CFU$/mL, 35% 에탄올은 $0.59{\pm}0.38-1.52{\pm}0.60\;{\log}_{10}CFU$/mL, 70% 에탄올은 $1.33{\pm}0.43-2.83{\pm}0.52\;{\log}_{10}CFU$/mL).

• 한국환경보건학회지
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• 제35권3호
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• pp.226-234
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• 2009

The main objective of this study was to evaluate the effects on shape and size, compressive strength, water absorption and heavy metals leaching with various weight mixing ratios in waste ash brick products using waste recycling MSWI(Municipal Solid Waste Incinerator) bottom ash, steel slag and waste building material. The manufacturing processes for the waste ash brick consist of screening, mixing, conveyor transmission, compaction.forming, and curing steps of raw materials. The weight mixing ratios of steel slag around bottom ash were adjusted within the ranges of 10% to 30%. The reported results show that the width and thickness of the manufactured waste ash brick could be satisfied with $90{\pm}2mm\;and\;57{\pm}2mm$, respectively which are K.S. standards of products qualities. And in case of length, only 20-Ba50Ss30, 20-Ba60Wb20 and 20-Ba50Wb30 for the mixing ratios could be satisfied with $190{\pm}2mm$ that is K.S. standards of products quality. The compressive strength and water absorption for 20-Ba50Ss30 and 20-Ba70Wb10 were over $8N/mm^2$ and below 15% respectively that are K.S. standards of manufactured waste ash brick. The results of tests for the heavy metals leaching in the all manufactured waste ash bricks are also passed to the wastes management regulations. The cost analysis of 20-Ba50Ss30 is evaluated. The manufacturing cost is evaluated 34.3 won/brick with 8 hours and 20tons of raw material per day. Incinerators with problems in bottom ash disposal can therefore derive significant benefits from the application of waste ash brick production.

• 대한치과교정학회지
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• 제19권2호
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• pp.7-24
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• 1989

The physical properties of seven sizes of control groups and experimental group in stainless steel orthodontic wires were studied in tension, hardness, bending, torsion and observation of microstructure. The wires (0.40-0.90mm dia.) of round type were tested in the as-received condition. The wires of control groups were TRU-CHROME and REMANIUM, and experimental group was SK wire which was developed by ourselves and made in Korea. The results were as follows; 1. The chemical compositions of control groups and experimental group were austenite stainless steel wires of SOS 304. 2. Higher values of tensile and yield strength in tension were control group I, experimental group, control group II. Maximum tensile and yield strength of experimental group were $203.63{\pm}1.41kg/mm^2$ in 0.70mm diameter and $148.96{\pm}4.88kg/mm^2$ in 0.60mm diameter, and maximum elongation was $5.20{\pm}0.57%$ in 0.45mm diameter. 3. Hardness values of experimental group were similar to control groups. Maximum hardness values were $596.2{\pm}13.66Hv$ in 0.45mm diameter wire of control group I, $590.5{\pm}20.08Hv$ in 0.50mm diameter wire of control group II, and $563.6{\pm}5.35Hv$ in 0.70mm diameter wire of experimental group. 4. Torsion properties of experimental group were similar to control group I and more than control group II. Maximum torsion cycles were $31.8{\pm}2.48$ in 0.45mm diameter of control group I, $17.4{\pm}4.84$ in 0.60mm diameter of control group II, and $24.6{\pm}3.04$ in 0.45mm diameter of experimental group. 5. Maximum bending cycles of experimental group were smaller than control groups. Maximum bending cycles were $9.00{\pm}0.00$ in 0.50mm diameter wire of control group I, $10.0{\pm}0.82$ in 0.40mm diameter wire of control group II, and $8.0{\pm}1.26$ in 0.50mm diameter wire of experimental group. 6. Microstructures of experimental and control groups co-existed with martensited austenite structure and elongated austenite structure. 7. The direction of wire fracture was propagated parallel to torsion direction typically and there was no probability showing wire fracture at inclusions and surface scratches. 8. The type of wire fracture was brittle fracture at initiation site and ductile fracture at core.

• 한국표면공학회지
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• 제35권4호
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• pp.199-205
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• 2002

TiN and TiAlN films were deposited on SKD 11 steel substrates by an arc ion plating (AIP) technique. The crystallinity and morphology for the deposited films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanical properties of both films were investigated through the indentation, impact, and wear test. Those films fairly adherent to SKD 11 steel substrate, showed hardness values of 2300 $\pm$ 100kg/$\textrm{mm}^2$ and 3200 $\pm$ 100kg/$\textrm{mm}^2$ with a load of 25g, respectively. During impact test, TiAlN films showed much superior impact wear resistance to TiN films. It could be suggested that the TiN films was failed relatively by plastic deformation with oxidation during impact test, while TiAlN films was failed by brittle fracture and resisted the oxidation by the impact energy. The friction coefficient of TiAlN films became lower than that of TiN films at high sliding speed condition although it was higher than that of TiN films at low speed. Therefore, TiAlN films was suggested to be more advantageous than TiN films for high speed machining fields.

• The Journal of Advanced Prosthodontics
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• 제7권3호
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• pp.257-263
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• 2015

PURPOSE. In this study, we aimed to evaluate the amount of marginal gap with two different substructure materials using identical margin preparations. MATERIALS AND METHODS. Twenty stainless steel models with a chamfer were prepared with a CNC device. Marginal gap measurements of the galvano copings on these stainless steel models and Co-Cr copings obtained by a laser-sintering method were made with a stereomicroscope device before and after the cementation process and surface properties were evaluated by scanning electron microscopy (SEM). A dependent t-test was used to compare the mean of the two groups for normally distributed data, and two-way variance analysis was used for more than two data sets. Pearson's correlation analysis was also performed to assess relationships between variables. RESULTS. According to the results obtained, the marginal gap in the galvano copings before cementation was measured as, on average, $24.47{\pm}5.82{\mu}m$ before and $35.11{\pm}6.52{\mu}m$ after cementation; in the laser-sintered Co-Cr structure, it was, on average, $60.45{\pm}8.87{\mu}m$ before and $69.33{\pm}9.03{\mu}m$ after cementation. A highly significant difference (P<.001) was found in marginal gap measurements of galvano copings and a significant difference (P<.05) was found in marginal gap measurements of the laser-sintered Co-Cr copings. According to the SEM examination, surface properties of laser sintered Co-Cr copings showed rougher structure than galvano copings. The galvano copings showed a very smooth surface. CONCLUSION. Marginal gaps values of both groups before and after cementation were within the clinically acceptable level. The smallest marginal gaps occurred with the use of galvano copings.

• 대한치과보철학회지
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• 제35권2호
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• pp.417-430
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• 1997

The purpose of this study was to compare the fracture resistance of copy-milled and conventional In-Ceram crown. Four groups of ten uniform sized all-ceramic crowns were fabricated. In-Ceram Spinell and In-Ceram Alumina crowns were fabricated as control group, Celay In-Ceram Spinell and Celay In-Ceram Alumina crowns were fabricated as test group. All specimen were cemented on stainless steel master die with resin cement, and stored in $37^{\circ}C$ water for 1 day prior to loading in Instron testing machine. Using a steel ball at a crosshead surfed of 0.5mm/min, the crowns were loaded at $30^{\circ}C$ angle until catastrophic failure occurred. The results obtained were as follows : 1. With the value of $984.8N{\pm}103.67N$, the strength of Celay In-Ceram Alumina crowns had a significantly higher fracture strength than conventional In-Ceram Alumina crowns ($876.2N{\pm}92.20N$) (P<0.05) 2. The fracture strength of Celay In-Ceram Spinell crowns($706.3{\pm}70.59N$) was greater than that of conventional In-Ceram Spinell crowns($687.4{\pm}90.26N$), but there was no significant difference(P>0.05). 3. The In-Ceram Alumina crowns had a significantly higher fracture strength than In-Ceram Spinell crowns in both methods(P<0.05). 4. Ther order of fracture strength was as followed : Celay In-Ceram Alumina, In-Ceram Alumina, Celay In-Ceram Spinell and In-Ceram Spinell crowns

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.237-239
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• 2003

A high-temperature superconductor (HTS) journal bearing was studied for loss. Two HTS bearings support the rotor at top and bottom. The rotor weight is 4 kg and the length is about 300 mm. Both the top and bottom bearings have two permanent magnet (PM) rings with an iron pole piece separating them. Each HTS journal bearing is composed of six pieces of superconductor blocks of size 35$\times$25$\times$10 mm. The HTS blocks are encased in a cryochamber through which liquid nitrogen flows. The inner spool of the cryochamber is made from G-10 to reduce eddy current loss, and the rest of the cryochamber is stainless steel. The magnetic field from the PM rings ＜ 10 mT on the stainless part. The rotational drag was measured over the same speed range. Results indicate that the 10 mT design criteria for magnetic field on the stainless part of the cryochamber is too high.

• 한국식품영양과학회지
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• 제39권5호
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• pp.776-781
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• 2010

격막식으로 생산한 강산성전해수(SEW)의 유효염소농도는 $35{\pm}1.2\;ppm$, pH는 $2.3{\pm}0.2$, ORP는 $1,140{\pm}20.4\;mV$이었으며, AEW의 유효염소농도는 $0.1{\pm}0.01\;ppm$, pH는 $11.6{\pm}1.1$, ORP는 $-900{\pm}18.2\;mV$이었다. 6종의 병원성세균(초기균수 $1.0{\times}10^7\;CFU/mL$)에 대한 SEW의 살균효과를 조사한 결과, 대조구로 사용한 유효염소농도 35 ppm의 차아염소산 나트륨 용액의 경우, 60초간 처리하여도 2~4 log 정도의 균밖에 감소하지 않았으나 SEW는 60초간 처리로 포자를 형성하는 B. cereus를 제외한 나머지 5종의 병원성세균을 모두 살균하였으며, B. cereus의 경우 완전하게 살균하지는 못하였지만 약 4 log CFU/g 이상이 감소하여, 같은 유효염소농도라도 SEW가 차아염소산나트륨 용액보다 살균력이 뛰어나다는 것을 알 수 있었다. 채소의 경우, AEW로 세척 후 SEW 처리하였을 때가 SEW 단독처리보다 살균효과가 더 좋았다. 한편 콩나물, 무순의 경우 AEW로 30초간 세척 후 SEW로 30초간 처리하여도 균수는 각각 $2.50{\pm}0.13$, $2.19{\pm}0.13$만 감소하였고 4 log CFU/g 이상의 균이 잔존하고 있었다. 식기와 컵은 차아염소산나트륨 용액(유효염소농도 35 ppm) 30초간 처리로는 1.19~1.28 log CFU/$100\;cm^2$ 정도만 감소하였지만, SEW 30초간 처리로 균이 검출되지 않았다. 고무장갑의 경우 유일하게 대장균군이 검출되었으며 SEW 30초간 처리로 고무장갑 표면의 일반세균과 대장균군은 대조군인 수도수에 비하여 약 2 log CFU/$100\;cm^2$ 이상 감소하였으나 완전한 살균은 되지 않았다.

• The Korean Journal of Physiology and Pharmacology
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• 제2권6호
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• pp.687-693
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• 1998

This study was performed to examine the mean arterial pressure and nociceptive jaw opening reflex after microinjection of glutamate into the amygdala in freely moving rats, and to investigate the mechanisms of antinociceptive action of amygdala. Animals were anesthetized with pentobarbital sodium (40 mg/kg, ip). A stainless steel guide cannula (26 gauge) was implanted in the amygdala and lateral ventricle. Stimulating and recording electrodes were implanted into each of the incisor pulp and anterior digastric muscle. Electrodes were led subcutaneously to the miniature cranial connector sealed on the top of the skull with acrylic resin. After 48 hours of recovery from surgery, mean arterial pressure and digastric electromyogram (dEMG) were monitored in freely moving rats. Electrical shocks (200 ${\mu}sec$ duration, $0.5{\sim}2$ mA intensity) were delivered at 0.5 Hz to the dental pulp every 2 minutes. After injection of 0.35 M glutamate into the amygdala, mean arterial pressure was increased by $8{\pm}2$ mmHg and dEMG was suppressed to $71{\pm}5%$ of the control. Injection of 0.7 M glutamate elevated mean arterial pressure by $25{\pm}5$ mmHg and suppressed dEMG to $20{\pm}7%$ of the control. The suppression of dEMG were maintained for 30 minutes. Naloxone, an opioid receptor antagonist, inhibited the suppression of dEMG elicited by amygdaloid injection of glutamate from $28{\pm}4\;to\;68{\pm}5%$ of the control. Methysergide, a serotonin receptor antagonist, also inhibited the suppression of dEMG from $33{\pm}5\;to\;79{\pm}4%$ of the control. However, phentolamine, an ${\alpha}-adrenergic$ receptor antagonist, did not affect the suppression of dEMG. These results suggest that the amygdala can modulate both cardiovascular and nociceptive responses and that the antinociception of amygdala seems to be attributed to an augmentation of descending inhibitory influences on nociceptive pathways via serotonergic and opioid pathways.