• 제목/요약/키워드: softening$K_0$ condition

검색결과 38건 처리시간 0.042초

예비열처리(豫備熱處理)에 의한 무우김치의 연화방지(軟化防止) (Pre-heating treatment for Prevention of Tissue Softening of Radish Root Kimchi)

  • 육철;장금;박관화;안승요
    • 한국식품과학회지
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    • 제17권6호
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    • pp.447-453
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    • 1985
  • 숙성중 무우 김치 조직의 연부현상을 방지하기 위하여 예비열처리와 $CaCl_2$의 효과를 조사하고 이를 이용하여 무우조직의 경도가 높은 김치를 제조하였다. 무우조직중의 펙틴분해효소인 폴리갈락투로나제(PG)는 펙틴에스테라제(PE)보다 더 낮은 농도의 $CaCl_2$에서 저해되었고, PE의 최적온도는 $50{\sim}55^{\circ}C,$ PG는 $45^{\circ}C$이었다. 따라서 0.05M $CaCl_2$용액에서 $55^{\circ}C$로 2시간동안 열처리 하여 PE는 활성화 시키고 PG는 억제시킬 수 있었다. 최적조건하에서 예비열처리를 하여 김치를 제조한 후 냉장고($4{\sim}10^{\circ}C$에서 저장하려면 pH, 환원당, 경도, 펙틴분해효소의 역가 그리고 펙틴물질의 변화를 측정하였다. 처리구의 무우김치는 비교구보다 숙성중 계속해서 높은 경도를 유지하였고 조직내에 있는 PE는 숙성중 계속 감소하였으며 PG는 초기에는 감소하다가 저장 말기에 가서는 증가하였다. 저장중 펙틴물질 조성의 변화는 비교구가 처리구에 비해 열수가용 펙틴질이 더 많이 증가하였으며 Sodium hexa meta phosphate soluble 펙틴은 더 많이 감소하였다.

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1-MCP와 에틸렌 혼용처리가 장기간 저온저장 후 상온에 보관된 '후지' 사과의 연화 억제에 미치는 영향 (Control of Softening of Long-Term Stored 'Fuji' Apples at Low Temperature and Subsequent Shelf-life by Combination Treatment of 1-MCP and Ethylene)

  • 최현석;정석규
    • 생물환경조절학회지
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    • 제26권2호
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    • pp.108-114
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    • 2017
  • '후지' 사과(Malus${\times}$domestica Borkh.)에 $1.0{\mu}L{\cdot}L^{-1}$ 1-MCP를 처리하거나 또는 1-MCP 처리 후 $10{\mu}L{\cdot}L^{-1}$ 에틸렌가스를 살포(1-MCP+에틸렌)하여 180일간 $0.5^{\circ}C$ 저온에서 과실의 저장성을 조사한 후에, 28일 동안 상온에서 보관하면서 연화정도를 비교하였다. 1-MCP 또는 1-MCP+에틸렌 처리된 과실의 산 함량과 경도는 저온저장 120일 이후부터 높은 수준으로 유지되었고, 이후 상온보관 28일 동안에서도 높게 나타났다. 1-MCP처리 과실은 저온저장+상온보관 동안 14N 이상으로 경도가 유지되었다. 과피 적색도는 저온저장 기간 중에는 처리에 따라 일관성 있는 결과가 나타나지 않았지만 상온보관 21일과 28일째에서는 1-MCP처리에 의하여 4.0 이상 높은 수준이 유지되었다. 대조구와 에틸렌 처리구는 저온저장 90일차에 에틸렌과 호흡량이 크게 상승되었고 클라이매터릭 맥시멈이 지나면서 노화가 더 빨리 진행된 것으로 판단되었다. 따라서 1-MCP가 처리된 과실은 $10{\mu}L{\cdot}L^{-1}$정도의 에틸렌에 노출되더라도 장기간 저온저장과 약 한달간의 상온저장 동안 상품성 유지가 가능한 것으로 평가되었다.

EVALUATION OF FRICTION WELDABILITY OF TYPE 5052 ALALLOY/LOW CARBON STEEL JOINT.

  • Kim, Kyung-Kyun;Lee, Won-Bae;Yeon, Yun-Mo;Kim, Dae-Up;Jung, Seung-Boo
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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    • pp.528-533
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    • 2002
  • The mechanical and metallurgical properties of friction welded joints type 5052 Al alloy/A36 steel have been studied in this paper. The joint strength increased with increasing upset pressure and friction time till it reached the critical value. The joint strength was fixed at low strength compare to that of base metal in the case of increasing friction time. Microstructure of 5052 Al alloy was greatly deformed near the weld interface. The very fine and equaxied grain structure was observed at the near interface. The elongated grain was formed outside dynamic recrystallizatoin region at the peripheral part, while the A36 steel' side was not deformed. The hardness of the near interface was slightly softer than that of 5052 Al alloy base metal. The maximum softening width was about 8mm from the interface. In the present work, the friction welding condition, t$_1$=0.5sec, P$_2$=137.5MPa, showed a maximum joint strength (202MPa) when friction pressure, upset time and rotation speed were fixed at 75MPa, 5sec, 2000rev/min and these were the optimum friction welding condition of 5052Al/A36 steel joints.

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동-텅스텐 소결합금(Cu-W)과 동(Cu)의 마찰용접 특성에 미치는 업셋압력의 영향에 관한 연구 (Effects of Upset Pressure on Weldability in the Friction Welding of Cu to Cu-W Sintered Alloy)

  • 강성보;민택기
    • Journal of Welding and Joining
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    • 제17권5호
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    • pp.69-76
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    • 1999
  • A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of upset pressure on friction weldability. Under the condition of friction time 0.8sec, upset pressure 150MPa, the tensile strength and Charpy impact value of the friction welded joint were 336MPa, $400KJ/m^2$ respectively. And highest temperature of the weld measured was below $800^{circ}K$ which is very lower than melting point of Cu($1356^{circ}K$). Under the same conditions, W grains picked up in Cu matrix from Cu-W profitably affected on these mechanical fracture, and were dispersed in Cu by plastic flow during brake time.

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저온피해 단감의 대형포장 저장에 따른 품질 변화 (The Quality Change and Storage Life of 'Fuyu' Persimmon Chill-injured in Tree)

  • 정대성;배정은
    • 한국포장학회지
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    • 제20권2호
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    • pp.59-63
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    • 2014
  • 단감을 저온피해 정도에 따라 저온저장하여 품질변화를 조사하였다. 중량감모율은 모든 처리구간에 큰 차이는 없었지만, 저온피해 정도와 저장기간이 길어질수록 모든 처리구에서 중량감소를 보였다. 경도의 경우는 단감의 품질을 좌우하는 중요한 요소로 저온피해가 길어질수록 경도가 낮아지면서 연화가 빨리 진행되었다. 정상과는 25.5 N에서 큰 변화는 없었다. 반면에 저온피해 1일과는 26.7 N에서 점점 낮아져 18.2 N까지 낮아졌으며, 저온피해 3일과는 16.1 N에서 12.22 N으로, 저온피해 5일과는 10.8 N에서 5.8 N까지 낮아졌다. 가용성 고형물 함량과 총산함량은 처리구간에 유의적인 차이는 없었다. 에틸렌은 정상과보다 2배의 에틸렌을 생성하였다. 저온피해가 심해질수록 에틸렌의 발생량은 증가하였고, 경도변화와도 관련됨을 알 수 있었다.

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연강 판재에 대한 연강 구의 고속경사충돌 수치해석 (Numerical Simulation of High-Velocity Oblique Impact of Mild Steel Spheres Against Mild Steel Plates)

  • 유요한;장순남;정동택
    • 대한기계학회논문집A
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    • 제26권3호
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    • pp.576-585
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    • 2002
  • A three-dimensional Lagrangian explicit time-integration finite element code for analyzing the dynamic impact phenomena was developed. It uses four node tetrahedral elements. In order to consider the effects of strain rate hardening, strain hardening and thermal softening, which are frequently observed in high-velocity deformation phenomena, Johnson-Cook model is used as constitutive model. For more accurate and robust contact force computation, the defense node contact algorithm was adopted and implemented. In order to evaluate the performance of the newly developed three-dimensional hydrocode NET3D, numerical simulations of the oblique impact of mild steel plate by mild steel sphere were carried out. Ballistic limit about various oblique angle between 0 degree and 80 degree was estimated through a series of simulations with different initial velocities of sphere. Element eroding by equivalent plastic strain was applied to mild steel spheres and targets. Ballistic limits and fracture characteristics obtained from simulation were compared with experimental results conducted by Finnegan et al. From numerical studies, the following conclusions were reached. (1) Simulations could successfully reproduce the key features observed in experiment such as tensile failure termed "disking"at normal impacts and outwards bending of partially formed plus segments termed "hinge-mode"at oblique impacts. (2) Simulation results fur 60 degrees oblique impact at 0.70 km/s and 0.91 km/s were compared with experimental results and Eulerian hydrocode CTH simulation results. The Lagrangian code NET3D is superior to Eulerian code CTH in the computational accuracy. Agreement with the experimentally obtained final deformed cross-sections of the projectile is excellent. (3) Agreement with the experimental ballistic limit data, particularly at the high-obliquity impacts, is reasonably good. (4) The simulation result is not very sensitive to eroding condition but slightly influenced by friction coefficient.

K2O-CaO-SiO2-P2O5계 유리의 형성 및 용출특성 (Glass Formation and Dissolution Characteristics of K2O-CaO-SiO2-P2O5)

  • 윤태민;윤영진;이용수;강원호
    • 한국재료학회지
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    • 제14권1호
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    • pp.67-72
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    • 2004
  • The glass-forming conditions are investigated in the $K_2$O-CaO-$SiO_2$ $-P_2$$O_{5}$ system with 10~65 mole% of$ P_2$$O_{5}$. Thermal properties and dissolution properties were investigated according to variation of the SiO and KO contents in selected compositions. The glass formation condition was determined when $K_2$O/$P_2$$O_{5}$ mole ratio 0~0.24, $SiO_2$/($SiO_2$+$P_2$$O_{5}$ ) mole ratio 0~0.29, and CaO/$P_2$$O_{5}$ mole ratio 0~1.00. In the result of the thermal properties, the glass transition temperature($T_{g}$) and softening temperature($T_{s}$ ) were gradually shifted to the lower temperature range with increase of $K_2$O contents. The maximum value of the chemical durability was shown in $K_2$$PO_2$$O_{5}$ mole ratio 0.17 when the $SiO_2$ contents were changed, and $K_2$O was fixed at 10 mole%. Hence the change of the $K_2$O/$P_2$$O_{5}$ mole ratio was found that a new main factor of the chemical durability.

분무성형을 통해 제조된 과공정 Al-Si 합금의 기계적 특성 (Deformation Behavior of Spray-formed Hypereutectic Al-Si Alloys)

  • 박우진;하태권;안상호;장영원
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2001년도 추계학술대회 논문집
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    • pp.285-288
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    • 2001
  • Hypereutectic Al-25Si-X alloys, expected to be applied to the cylinder-liner-part of the engine-block of an automobile due to the excellent wear resistance, low density and low thermal expansion coefficient has been fabricated through a spray forming process. The obtained microstructure of the hypereutectic Al-25Si-X alloy appeared to consist of Al matrix and equiaxed Si particles of average diameter of $5-7{\mu}m$. To characterize the deformation behavior of this alloy, a series of load relaxation and compression tests have been conducted at temperatures ranging from RT to $500^{\circ}C$. The strain rate sensitivity parameter (m) of this alloy has been found to be very low (0.1) below foot and reached 0.2 at $500^{\circ}C$. During the deformation above 300'c in compression, strain softening has been observed. The diagram of extrusion pressure vs. ram-speed has been constructed, providing the extrusion condition of Al-25Si-X alloys.

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표면결정화유리에 관한 연구 (A Study on the Surface Crystallization of Glass)

  • 박용완;강은태
    • 한국세라믹학회지
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    • 제14권4호
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    • pp.230-235
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    • 1977
  • In this paper the conditions of surface crystallization of glass were studied. The basic glass which is apt to crystallize, with $SiO_2$ 72.50, $Al_2O_3$ 5, 00, $Na_2O$ 8.00 $K_2O$ 3.50, CaO 5.00, MgO 3.00, $B_2O_3$ 3.00 Wt% is chosen. The strain point and softening point of this glass is 4$25^{\circ}C$ and 778$^{\circ}C$ each, and between the two temperatures we could get grystal on its surface by immersion in salt baths during some controlled hours. The kind of crystal on the surface of glass was confirmed by X-ray diffraction analysis and the change of the thickness of crystalline layers depending on temperature and time, was surveyed by using optical microscope. The results are as follows; 1. The chloride group is more suitable than sulfate group for the treating salt. 2. In the condition with 50 LiCl.50NaCl at 62$0^{\circ}C$ for 2 hrs and with 50 LiCL.20-30 NaCl.30-20 $CaCl_2$ at 72$0^{\circ}C$ for 15-20 min. we could get the best crystalline layers. 3. The crystal was silica-O and petalite with a little tridymite and nepheline. 4. The thickness of crystalline layers increased with increasement of temperature and time.

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12% Cr 로터강의 강도 개선에 관한 연구 (Study on the Improvement of Strength for 12% Chromium Steel Rotor)

  • 장윤석;오세욱
    • 한국해양공학회지
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    • 제3권2호
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    • pp.625-625
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    • 1989
  • To check technical improvement in the soundness and strength of 12% Cr steel rotor, a 25 tons of rotor with 65 tons of ingot was made in real size and was cut to pieces to take test samples, and the various mechanical tests such as impact, tensile, creep, and fatigue were carried out. The strengths are compared with those of 1% Cr-Mo-V rotor of same size. Microstructures of the samples are examined and reviewed. The results can be summarized as follows. 1) Fracture appearance transition temperatures are 80.deg. C at the center part and 60.deg. C near surface of 12% Cr rotor, and 8.deg. C near surface of 1% Cr-Mo-V rotor. 2) Comparative rapid softening occurs at higher temperatures above 600.deg. C for 12% Cr steel and 550.deg. C for 1% Cr-Mo-V steel in tension tests. 3) Fatigue crack propagation rate of 12% Cr steel is almost same as that of 1% Cr-Mo-V steel at the same corresponding surface part of the rotors. The crack growth rate of center part of 12% Cr rotor is faster than near surface part of the rotor, and the crack growth rate at the load condition of R=0.04 is slower than that of the load condition of R=0.5 for both 12% Cr steel and 1% Cr-Mo-V steel. 4) Crack growth rate of radial direction near surface of 12% Cr rotor is faster than that of transverse direction at the same part because of the difference in residual stresses. 5) Both creep and fatigue strengths of 12% Cr steel are superior to those of 1% Cr-Mo-V steel and the difference is thought the effect of climb and glide controlled creep by solid solution of alloying elements and dispersion of carbides.