• Journal of Sericultural and Entomological Science
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• v.26 no.1
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• pp.30-34
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• 1984

In order to investigate an endocrinological effect on metamorposis of the midgut in silkworm, Bombyx mori, 20-hydroxyecdysone and rude extract of brain (PTTH) were injected into pupal isolated abdomens, devoid of prothoracic glands and also in the brainless diapausing pupae with the prothoracic glands (so-called dauer pupae). When ecdysone was assayed abdomens, drastic morphological changes occurred in the midgut. The wet weights of midguts were found decrease as like the normal pupae at metamorphosis. Proteineous changes in epithelial midgut were also observed; pupal specific proteins (PSP) vanished while the adult proteins were newly synthesized. Similar results were also found in the changes of protein in the midgut of dauer pupae by injecting ecdysone and PTTH.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.155-158
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• 2003

The effects of Mn, V addition on the behavior of structure and the effects of cooling rate of S20C steel for use of Tn housing and valve for automotive parts have been investigated. Transformation start temperature measured from inflection point of cooling curves has been found out to decrease with increasing cooling rate and to be more sensitive to Mn contents when cooling rate is fast. It was therefore shown that the grain was refined. If there is a big compacting pressure, it is indicated that hardness becomes much greater at surface than inside.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.961-969
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• 2007

The laser material processing has replaced a conventional material processing such as a welding, cutting, drilling and surface modification and so on. LTH(Laser Transformation Hardening) is one branch of the laser surface modification process. A lot of energy is needed for the LTH process to elevate workpiece surface to temperature of the austenite transformation($A_3$), which results from utilizing a beam with a larger size and lower power intensity comparatively. The absorptivity of the laser energy with respect to material depends on the wave length of a beam. This study is related to the surface hardening for the rod-shaped carbon steel by the high power diode laser(HPDL) whose beam absorptivity is better than conventional types of lasers such as $CO_2$ or Nd:YAG laser. Because a beam proceeds on the rotating specimen the pretreated hardened-phase can be tempered and softened by the overlapping between hardened tracks. Accordingly, the longitudinal hardness measurement and observation of the micro structure was carried out for an assessment of the hardening characteristics. In addition, a hardening characteristics as a hardenability of materials was compared in the point of view of the hardness distribution and hardening depth and width.

• Journal of Power System Engineering
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• v.16 no.4
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• pp.60-65
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• 2012

This study was carried out to investigate the effect of reverse transformation on the damping capacity in high manganese austenitic stainless steel. ${\alpha}^{\prime}$-martensite was formed with the specific direction and surface relief by deformation. Over 95% of the austenite phase was transformed to deformation-induced ${\alpha}^{\prime}$-martensite by 70% cold rolling. Reverse transformation became rapid above an annealing temperature of $550^{\circ}C$, but there was no significant transformation above $700^{\circ}C$. In addition, with increasing annealing time at $700^{\circ}C$, reverse transformation was induced rapidly, but the transformation was almost completed at 10 min. Damping capacity was increased up to $700^{\circ}C$, and than unchanged with the increasing annealing temperature. Damping capacity increased steeply with an increasing reverse treatment time up to 10min, whereas there were no significant change with a treatment time of more than 10 min. Damping capacity increased with an increasing the reversed austenite and was strongly affected by reversed austenite.

• Applied Microscopy
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• v.31 no.2
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• pp.143-156
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• 2001

The aim of this study was to clarify the differentiation of seminiferous epithelial cells and spermiogenesis in the testis of Rana catesbeiana. Spermatogenesis of R. catesbeiana consists of primary spermatogonia, secondary spermatogonia, primary spermatocytes, secondary spermatocytes and spermatids. They were subdivided into eight stages on the basis of the morphological features of the germ cell differentiation. From the spermatocytes except primary spermatogonia to before the spermiation of spermatids were surrounded by spermatocyst. Spermiogenesis of R. catesbeiana can also be divided into three stages on the basis of morphological features of the nucleus and the cytoplasm organelles. Spermatozoon contained a saccular acrosome, a cylindrical and tapered slighty at both ends head, and a tail with only the axoneme.

• Laser Solutions
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• v.11 no.4
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• pp.7-12
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• 2008

Laser Transformation Hardening(LTH) is one branch of the laser surface modification processes. A lot of energy is needed for the LTH process to elevate workpiece surface to temperature of the austenite transformation($A_3$), which results from utilizing a beam with a larger size and lower power density comparatively. This study is related to the surface hardening for the rod-shaped carbon steel by the high power diode laser whose beam absorptivity is better than conventional types of lasers such as $CO_2$ or Nd:YAG laser. Because a beam proceeds on the rotating specimen, the pretreated hardened-phase can be tempered and softened by the overlapping between hardened tracks. Accordingly, the longitudinal hardness measurement and observation of the micro structure was carried out for an assessment of the hardening characteristics. In addition, a hardening characteristics as a hardenability of materials was compared in the point of view of the hardness distribution and hardening depth and width.

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.05a
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• pp.64-65
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• 1993

MPB 조성영역인 Zr/Ti=52/48의 composite ceramic target을 사용하여 RF magnetron sputtering 방법으로 기판온도 약 30$0^{\circ}C$에서 RZT 박막을 Pt/Ti/Si 기판위에 증착시켰다. 안정상인 perovskite 구조를 형성시키기 위하여 PbO분위기에서 furnace annealing 과 Repid thermal annealing을 실시하여 열처리 방법에 따른 상형성 및 계면반응과 그에 따른 전기적 특성을 고찰 하였다. Pt 의 두께가 250$\AA$인 경우 furnace annealing 시 $650^{\circ}C$에서 perouskite 상이 형성되었으나 Pt층이 산소의 확산을 방지하지 못하여 상부의 Ti 층이 TiOx로 변태하였으며 하부의 Ti는 Si 과 반응하여 Ti-silicide 롤 변태하였다. 또한 75$0^{\circ}C$,60sec 인 경우 Pt 층의 응집화가 관찰되어 하부전극으로서 적용이 적절하지 못하다. 급속열처리를 실시한 경우에도 마찬가지로 Ti 층이 TiOx 와 silicide 층으로 변태되었다. Pt의 두께가 1000$\AA$인 경우에도 250$\AA$와는 달리 RTA 시 (III)방향으로 Furace annealing 시(001)방향으로 우선 성장하였다. 이는 Ti(001), P(111),PZT(111)면의 lattic mismatch 가 매우 작은데다 RTA 시 계면반응이 거의발생하지 않아 PZT 박막이 (111) 방향으로 우선 성장한 것으로 보인다. Furnace annealing 경우는 심한 계면반응이 발생하여 Pt층에 어느 정도 영향을 주었기 때문에 우선성장 방향이 바뀌었다구 생각한다.

• Korean Journal of Materials Research
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• v.10 no.6
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• pp.409-414
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• 2000

Three different white cast irons alloyed with Cr, V, Mo and W were prepared in order to study their transformation behavior of matrix structures in heat-treated conditions. The specimens were produced using a 15kg-capacity high frequency induction furnace. Melts were super-heated to $1600^{\circ}C$, and poured at $1550^{\circ}C$ into Y-block pepset molds. Three combinations of the alloying elements were selected so as to obtain the different types of carbides and matrix structures : 3%C-10%Cr-5%Mo-5%W(alloy No. 1), 3%C-10%V-5%Mo-5%W(alloy No. 2) and 3%C-17%Cr-3%V(alloy No. 3). The heat-treatments were conducted as follows: frist of all, as-cast specimens were homogenized at $950^{\circ}C$ for 5h under the vacuum atmosphere. Then, they were austenitized at $1050^{\circ}C$ for 2h and followed by air-hardening in air. The air-hardened specimens were tempered at $300^{\circ}C$ for 3h. The observation of morphology of the matrix structures was carried out in the states of as-cast(AS), air-hardened(AHF) and tempered(AHFT). The matrix structures of each alloy were almost fully pearlitic in the as-cast state but it was transformed to martensite, tempered martensite and retained austenite by the heat-treatments such as air-hardening and tempering.

• 한국지구과학회:학술대회논문집
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• 2010.04a
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• pp.99-100
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• 2010

충남 서부에 위치한 보령 지역은 트라이아스기 후기로 알려진 육성 기원의 남포층군이 널리 분포하고 있다. 남포층군은 하부로부터 하조층, 아미산층, 조계리층, 백운사층 및 성주리층으로 구분된다. 남포층군에서 산출되는 화석의 대부분은 식물 화석이며, 기타 이매패 화석, 어류 화석, 곤충의 유충 화석, 패갑류(conchostracans) 등의 화석이 산출되고 있지만, 양적으로 극히 적다. 이들 화석 중에서 체계적으로 연구가 된 것은 식물 화석뿐이고, 나머지 화석들은 전문 연구가의 부재 등에 의해 극히 미미한 연구 수준에 머물러 있다. 이번의 연구를 통해서 아미산층에서 채집된 곤충화석은 모두 107점이고, 그중에서 유충 화석이 94점, 날개 화석이 14점이다. 이들의 분류학적 연구 결과, 아미산층의 곤충화석군은 소시목, 강도래목, 날도래목, 하루살이목, 잠자리목, 바퀴벌레목, 벌목, 매미목을 비롯한 8목 11종에 이르는 유시류의 곤충들로 구성된다. 이들은 현재까지 우리나라에서 발견된 곤충화석 중 시대적으로 가장 오래된 화석이다. 유충 화석은 모두 수서 곤충의 유충화석이다. 이들의 유충은 수중생활에 적응하여 지상생활을 하는 성충과 형태적으로 큰 차이가 있는 불완전변태류 또는 외시류이다. 날개 화석은 수서곤충의 성충의 날개이고 일부는 육상 생활을 하는 곤충의 날개가 포함되어 있다. 아미산층에서 나온 곤충화석에는 육상에서 생활하는 매미목과 바퀴목도 있는데 이들은 불완전변태류에 속한다. 그러나, 똑같은 육상생활자이면서도 벌목은 완전변태류 또는 내시류에 속하는 것도 있다. 따라서 아미산층에서 산출된 곤충화석군에는 불완전변태류와 완전변태류가 섞여 있는 특징을 보인다. 이들은 실제로 같은 시대에 비슷한 장소에서 함께 생활을 했던 생물군집이지만, 서로 살던 장소가 다른 집단들이 섞여 있다는 것은 육상생활자의 일부가 죽은 후 수류에 의해 퇴적분지로 유입되어 매몰된 혼합집단으로 볼 수 있다. 현생의 하루살이목, 강도래목 등은 대표적인 유수성 곤충이고, 잠자리, 노린재 등은 대표적인 정수성 곤충으로 알려져 있다. 이들이 지층에 밀집하여 산출되는 것으로 보아 살던 장소에서 많은 퇴적물의 유입에 따른 급격한 매몰에 의해 화석화된 것으로 판단된다. 동아시아의 중생대 초기에서 보고된 곤충 화석은 양적으로도 수적으로도 그리 많지 않다. 그중에서 일본의 Mine에서 보고된 화석군이 가장 대표적이며 바퀴류(Blattaria)와 딱정벌레(Coleoptera)의 화석이 가장 큰 비율을 차지하지만, 아미산층 곤충화석군과의 공통종은 한 종도 없다. 아미산층의 곤충화석군은 비록 다양성은 쥐라기의 곤충상에 비해 떨어지지만 조성적으로는 쥐라기의 곤충상에 매우 유사하다. 육상에 사는 곤충이 화석으로 보존되기 어렵다는 것을 감안하면 아미산층에서 산출된 곤충화석은 학술적으로 매우 귀중하고 큰 의미가 있다. 보령 지역의 곤충화석은 중생대의 쥐라기와 백악기를 거쳐 현재로 이어지는 곤충 진화사의 잃어버린 고리를 이어줄 수 있는 귀중한 자료로 평가된다.

• Proceedings of the Korean Magnestics Society Conference
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• 1997.05a
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• pp.60-61
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• 1997