• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.391-394
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• 2006

Growth characteristics of methane-propane clathrate hydrate, growing under different undercooling conditions, was investigated. After the water within pressurized vessel was fully saturated with guest gas molecules by agitation, medium was rapidly undercooled and maintained at the constant temperature. The growth of hydrate was always Initiated with film formations at the upper bounding surface of liquid pool. The visual observation using microscope revealed detailed features of subsequent crystal nucleation, migration, growth and interference occurring within liquid pool. A number of small crystals ascended and settled at the hydrate film. When undercooling was small $({\Delta}T=3.2K)$, some of the settled crystals slowly grew into faceted columns. As the undercooling increased, the downward growth of crystals underneath the hydrate film became dendritic and occurred with greater rate and with finer arm spacing. The shapes of the floating crystals were diverse and included octahedron and triangular or hexagonal platelet When the undercooling was small, the octahedral crystals were found dominant. As the undercooling increased, the shape of the floating crystals also became dendritic. The detailed characteristics of floating crystals were reported in this study.

• Korean Chemical Engineering Research
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• 제45권4호
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• pp.400-409
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• 2007

메탄/프로판 혼합기체의 포접 하이드레이트를 다양한 과냉 조건 하에서 생성시키며 결정의 성장 특성을 연구하였다. 먼저 내압 용기를 물과 고압의 혼합기체로 충진하고 충분히 교반하여 용액을 포화시킨 후, 내부 온도를 하이드레이트 생성온도 이하로 급격히 떨어뜨리고 이후에는 일정하게 유지하며 하이드레이트 결정의 핵생성, 이동, 성장 및 간섭을 현미경을 통하여 관찰하였다. 수행한 모든 실험조건에서 하이드레이트의 생성은 기체와 액체의 상경계면에서 막의 형태로 시작되었으며, 이후 용기 하부에서 생성된 다수의 소결정들이 부상하여 일부는 막의 밑면에 부착하고 일부는 하이드레이트 막으로부터 자라는 결정과 간섭하며 아래 방향으로 성장하였다. 막 근처에서 성장하는 결정들은, 비교적 작은 과냉 조건에서는 다면 기둥의 형태를 가지며 과냉이 커짐에 따라 형상이 수지상(dendrite)으로 천이하고 성장속도는 증가하며 가지간격은 감소하였다. 액체 영역 내부에서 관찰 된 부유 결정(floating crystals)들은 팔면체, 삼각판 및 육각 판 등 다양한 형태를 보이며, 과냉이 작을수록 팔면체 형태가 지배적이었다. 과냉이 커짐에 따라 부유 결정 역시 수지상으로 천이하며 성장하였다. 상세한 하이드레이트 결정의 성장 특성을 과냉과 기억효과(memory effect; 하이드레이트가 분해된 후에도 액체에 물분자의 입체 그물 결합구조가 잔존하는 현상)가 미치는 영향을 중심으로 기술하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.234-237
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• 2004

As an automotive industry's demand for lighter materials gets bigger and bigger, a lot of new strength Al alloys have been developed recently. In the present study, Al 6xxx series alloys were designed to get the strength level of 350MPa with the elongation of $12\%$. For that purpose, three alloy systems were selected based on the thermodynamics calculation. The effect of both $Mg_{2}Si$ precipitate and excess Si amount on the newly designed alloys was investigated. Also, heat treatment procedure was studied to optimize the mechanical properties.

• 대한수의학회지
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• 제35권1호
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• pp.29-37
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• 1995

This study was carried out to investigate the morphological changes of the oxytocin secreting neurons in age-related rat hypothalamus by means of immunohistochemistry. The experimental group was 20 aged female rats (Sprague-Dawley, 25~30 months), and the control group was 10 adult female rats (10 months). All animals were perfused transcardially with 4% paraformaldehyde-lysine-periocdate(PLP), and serial transverse brain sections($30{\mu}m$) were prepared by means of cryotome, and were stained with rabbit anti-oxytocin antisera immunohistochemically, using the free floating method and avidin-viotin peroxidase complex. The results were as followings. 1. The immunostained oxytocin secreting neurons were located at the paraventricular nucleus and supraoptic nucleus of age-related rat hypothalamus chiefly. 2. The numbers of oxytocin secreting neurons decreased at the paraventricular nucleus and supraoptic nucleus of age-related rat hypothalamus(p<0.01) 3. The oxytocin secreting neurons of age-related rat hypothalamus immunostained less than those of the adult rat hypothalamus, and the paraventricular nucleus immunostained greater than supraoptic nucleus in age-related rat. 4. The numbers and expansion of dendrite and axonal varicosities decreased in the age-related rat hypothalamus greatly.