• Title/Summary/Keyword: 저항증가

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Effects of Resistance Training on BMD and Bone Metabolism Related Markers in Aging Rats (저항성 훈련이 노화흰쥐의 골밀도 및 골대사 관련 지표에 미치는 영향)

  • Kang, Hyung-Sook;Kim, Sang-Bae;Yoon, Jin-Hwan
    • 한국노년학
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    • v.31 no.2
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    • pp.303-315
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    • 2011
  • The purpose of this study was to investigate effect of resistance training on BMD and bone metabolism related markers in aging rats. Thirty male Spraugue-Daweley rats were divided into sedentary (CON; n=10 ) non-load resistance trained(NLRTG; n=10), and load resistance trained(LRTG; n=10) groups at the age of 64 weeks. The rats in the resistance training groups((NLRTG and LRTG) performed the tower climbing exercise 4 times a week. The LRTG groups were conditioned to climb a vertical ladder with weights appended to their tail 4 days/wk for 12 wks. After 12 weeks of exercise, serum osteocalcin, bone mineral density (BMD), breaking force, ash, Ca, and P in the femur were measured. After training, serum osteocalcin (OC) was significantly (p < 0.05) higher in both LRTG and NLRTG when compared to Control. Right femur BMD was significantly (p < 0.05) greater for LRTG when compared to both NLRTG and Control with no significant difference between NLRTG and Conrtol. The breaking force of femur was significantly (p < 0.05) greater for LRTG and NLRTG when compared to Control. The Ash, Ca, content of femur were significantly increased in resistance training groups than control group. These results suggest that the increase in bone mineral density induced by resistance training is mediated by changes in bone microarchitecture as well as training intensity and osteocalcin.

Interfacial Evaluation and Nondestructive Damage Sensing of Carbon Fiber Reinforced Epoxy-AT-PEI Composites using Micromechanical Test and Electrical Resistance Measurement (Micromechanical 시험법과 전기저항 측정을 이용한 탄소섬유 강화 Epoxy-AT-PEI복합재료의 비파괴적 손상 감지능 및 계면물성 평가)

  • Joung-Man Park;Dae-Sik Kim;Jin-Woo Kong;Minyoung Kim;Wonho Kim
    • Composites Research
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    • v.16 no.2
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    • pp.62-67
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    • 2003
  • Interfacial properties and damage sensing for the carbon fiber/epoxy-amine terminated (AT)-polyetherimide (PEI) composite were performed using microdroplet test and electrical resistance measurements. As AT-PEI content increased, the fracture toughness of epoxy-AT-PEI matrix increased, and interfacial shear strength (IFSS) increased due to the improved fracture toughness by energy absorption mechanisms of AT-PEI phase. The microdroplet in the carbon fiber/neat epoxy composite showed brittle microfailure mode. At 15 phr AT-PEI content ductile microfailure mode appeared because of improved fracture toughness. After curing, the change in electrical resistance $\Delta\textrm{R}$) with increasing AT-PEI content increased gradually because of thermal shrinkage. Under cyclic stress, in the neat epoxy case the reaching time until same stress was faster and their slope was higher than those of 15 phr AT-PEI. The result obtained from electrical resistance measurements under curing process and reversible stress/strain was correspondence well with matrix toughness properties.

Flow Resistance Characteristics of Hollowness-Block Channel Bed (중공블럭 하상의 흐름저항 특성)

  • Chae, Kuk-Sheok;Park, Sang-Deok;Shin, Seung-Sook;Cho, Jae-Woong
    • Proceedings of the Korea Water Resources Association Conference
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    • 2007.05a
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    • pp.870-873
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    • 2007
  • 하천의 수공 구조물은 홍수 시 작용하는 유수력에 대한 안정성을 확보해야 한다. 본 연구에서는 최근 개발된 친환경 식생호안블록인 중공블록을 하상에 설치할 경우 흐름에 미치는 영향을 연구하였다. 중공블록을 설치한 개수로에 대한 수리모형 실험을 실시하여 흐름저항과 경계층 특성에 대한 중공블록의 영향을 평가하였다. 흐름저항 특성 인자인 Manning의 조도계수와 Darcy-Weisbach의 마찰손실계수는 일정한 유량과 하상경사의 경우 수심에 큰 영향을 받고 이들은 서로 비례관계에 있음을 확인하였다. 그러나 마찰손실계수가 증가하더라도 어느 한계점 이상이 되면 조도계수는 일정한 값으로 수렴한다. 개수로의 경계층의 높이는 하천의 흐름특성과 구조특성을 반영하는 것으로 수심, 유속, 에너지경사, 경계면의 상대조도, Reynolds수, Froude수 등의 함수로 나타낼 수 있다. 중공블록이 설치된 개수로의 조도계수는 일반하천의 경우와 비교하여 큰 값을 나타내고 있어 중공블록이 흐름저항을 크게 증가시키는 것으로 판단된다.

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Drag Characteristics According to Ground Rope and Seabeds in the Bottom Trawl (저층트롤의 발줄 및 저질의 종류에 따른 저항특성)

  • 신정욱;이주희;권병국
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.38 no.1
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    • pp.58-68
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    • 2002
  • The model experiments for the Eastern sea bottom trawl were conducted for the 3 types of ground ropes and 2 types of seabeds to examine drag characteristics according to towing speed. The model net was based on the net of trawler with 750ps and made by 1/78 of a full scale net. This experiments focused on the drags for 3 types of ground rope, the serving wire, the original and the chain types and 2 types of seabeds, mud and sand of bottom. The results obtained are summarized as follows 1. In the case of the sand bottom, the drags by 3 types of ground rope were orderly increased in turn of the chain, the serving wire and the original type. But, in the case of the mud bottom, the drag of the original type is higher than that of the serving wire type and less than the chain type. 2. In the case of the serving wire type of ground rope, the drags by the diameters of ground rope, ø 1.3, ø 1.9, ø 2.6 and ø 3.25 were increased respectively by 23g, 25g, 32g and 42g at the towing speed of 0.4m/s. 3. The drags of ground ropes were increased exponentially in proportion to the towing speed, in the same way in all of three types of ground rope. 4. The ratios of drag of ground rope against that of the trawl net by the type of ground rope at the towing speed of 0.4m/s on the mud bottom were 0.69 in the chain type, 0.64 in the serving wire type and 0.67 in the original type respectively. 5. The Coefficient of drag($C_d$) by type of ground rope according to the towing speed were 10.0~56.7, 3.0~l6.0 and 1.5~8.5 respectively in turn of the chain type, the serving wire type and the original type on the mud bottom, and that on the sand bottom were 10.0~60.0, 3.0~14.0 and 1.2~6.0 respectively In turn of the chain type, the serving wire type and the original type.

Effects of Buffer Layer and Annealing Temperature on Magnetororesistance in Co/Cu Multilayers (기저층 및 열처리 효과가 Co/ Cu 다층박막의 자기저항에 미치는 영향)

  • 김미양;최규리;최수정;송은영;이장로;황도근;이상석;박창만;이기암
    • Journal of the Korean Magnetics Society
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    • v.7 no.2
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    • pp.82-89
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    • 1997
  • Dependence of magnetoresistance on the thickness of Cu, type and thickness of buffer layer, and the stacking number of multilayer in the form buffer /$[Co(17{\AA}/Cu(t{\AA})]_{20}$ were investigated. To evaluate effect of annealing on this samples, X-ray diffraction analysis, vibrating sample magnetometer analysis, and magnetoresistance measurement (4-probe method) were performed. The magnetoresistance ratio exhibits a maximum of 21% for the multilayer with Cu thickness of 24$\AA$ and Fe buffer layer thickness of 50$\AA$. Deposition of film under low base pressure induces in increase magnetoresistance ratio by preventing oxidation. The multilayer annealed below 30$0^{\circ}C$ temperature allowed larger textured grain without loss in the periodicity. Magnetoresistance ratios of the multilayer with Cu thickness of 24$\AA$ and 36$\AA$ were increased due to the increase in the antiferromagnetically coupled fraction after annealing.

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Effect of Fcrromagnetic Layer and Magnetoresistance Behavior of Co-Evaporated Ag-CoFe Nano-Granular Alloy Films (Ag - CoFe 합금박막의 자기저항 및 강자성 상하지층의 효과)

  • 김용혁;이성래
    • Journal of the Korean Magnetics Society
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    • v.7 no.6
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    • pp.308-313
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    • 1997
  • The magnetoresistance (MR) and the saturation field behavior of the CoFe-Ag nano granular films as a function of the ferromagnetic underlayer and overlayer materials were investigated. The maximum MR ratio of 25.7 % and the saturation field of 2.1 kOe in the as-deposited 3000 $\AA$ $(Co_{92}Fe_8)_{31}Ag_{69}$ single alloy films at room temperature were obtained. The MR ratio and the saturation field of the 100 $\AA$ alloy film were 1.2 % and 5.2 kOe, respectively. Those of the sandwiched alloy films of 200 $\AA$ thick with the Fe under and overlayer of 100 $\AA$ were 11 % and 1.8 kOe respectively. The reduction of saturation field in the sandwiched alloy films is due to the exchange coupling between the ferromagnetic layers and the alloy layer. Among the Fe and FeNi, the more effective materials to reduce the saturation field of the sandwiched alloy films was Fe.

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농업기술 - 논 잡초, 이렇게 잡으세요!

  • Park, Tae-Seon
    • 농업기술회보
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    • v.52 no.4
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    • pp.16-17
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    • 2015
  • 농사는 잡초와의 싸움이라고 하였다. 벼농사에서 파종, 육묘, 이앙 등의 재배과정은 기계화로 인해 투입 시간이 매년 절감되고 있으나 잡초 방제 투입 시간은 증가하고 있을 뿐만 아니라 제초제 사용 횟수도 증가하고 있다. 이러한 원인의 가장 큰 이유는 논에서 제초제 저항성 잡초들이 전국적으로 빠르게 확산하고 있기 때문이다. 제초제 저항성 잡초의 발생 원인과 잡초 제거 방법에 대해 알아본다.

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Dependence of Magnetoresistance on the Underlayer Thickness for Top-type Spin Valve (Top형 스핀밸브 구조의 Si 기판에서의 하지층 두께에 따른 자기저항 특성 연구)

  • Ko, Hoon;Kim, Sang-Yoon;Kim, Soo-In;Lee, Chang-Woo;Kim, Ji-Won;Jo, Soon-Chul
    • Journal of the Korean Magnetics Society
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    • v.17 no.2
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    • pp.95-98
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    • 2007
  • In this paper, the magnetic properties and the annealing behavior of spin valve structures with Mo(MoN) underlayers were studied for various underlayer thickness. The spin valve structure was Si substrate/Mo(MoN)$(t{\AA})/NiFe(21{\AA})/CoFe(28{\AA})/Cu(22{\AA})/CoFe(18{\AA})/IrMn(65{\AA})/Ta(25 {\AA})$. Mo and MoN films were deposited on Si substrates and their thermal annealing behavior was analyzed. The deposition rate of the MoN thin film was decreased and tile resistivity of the MoN thin films were increased as the $N_2$ gas flow was increased. The variations of MR ratio and magnetic exchange coupling field of spin valve structure were smaller with MoN underlayers than that with Mo underlayers up to thickness of $51{\AA}$. MR ratio of spin valves with Mo underlayers was 2.86% at room temperature and increased up to 2.91 % after annealing at $200^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased about 2.16%. The MR ratio of spin valves structure with MoN underlayers for $N_2$ gas flow 1 sccm was 5.27% at room temperature and increased up to 5.56% after annealing at $200^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased about 4.9%.

결정질 실리콘 태양전지의 전면 전극 최적화 설계에 대한 연구

  • Yu, Gyeong-Yeol;Baek, Gyeong-Hyeon;Baek, Seung-Sin;Lee, Jun-Sin
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.08a
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    • pp.407-407
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    • 2011
  • 태양전지에서 Fill Factor를 저하시키는 직렬저항의 성분들은 베이스저항, 에미터 저항, contact 저항, finger 저항, busbar 저항 등이 있다. 각각의 저항 성분은 전극의 width및 height, 그리고 전극과 전극 사이의 spacing을 가변함에 따라 각기 다른 값을 나타내는데, 낮은 직렬저항 값을 달성하기 위해 전극의 면적을 크게 하는 것이 바람직하지만, 이는 cell의 shading loss를 증가시켜 cell의 JSC를 저하시킨다. 그러므로 cell의 면적과 전면 에미터의 면저항을 고려하여 shading loss와 직렬저항을 최소화 하는 최적의 전면 전극의 설계가 중요하다. 본 논문에서는 시뮬레이션을 통해 전면 전극의 height, spacing 및 width를 가변하여 1 by 1, 2 by 2, 3 by 3의 cell 면적에서의 전면 전극의 설계를 최적화 하였다. 시뮬레이션 결과 각각의 cell면적에서 단위면적당 저항 값이 500 $m{\Omega}$ 이하, shading loss가 4% 미만인 전극을 설계하였다.

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Oxygen Reduction Mechanism and Electrode Properties of (La,Sr)$MnO_3$-YSZ Composite Cathode for Solid Oxide Fuel Cell (Part II: Electrode Properties) (고체산화물 연료전지용 (La,Sr)$MnO_3$-YSZ 복합체 양극의 산소환원 반응기구 및 전극 특성 (Part II: 전극 특성))

  • 김재동;김구대;이기태
    • Journal of the Korean Ceramic Society
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    • v.38 no.1
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    • pp.93-99
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    • 2001
  • (La,Sr)MnO$_3$(LSM)-YSZ 복합체 양극에 있어서 소결온도 및 전극두께와 cathodic potential이 전극 특성에 미치는 영향을 고찰하였다. 양극의 소결은 삼상계면의 양을 결정하는 중요한 변수로 LSM 단미 양극과 YSZ가 40 wt% 포함된 LSM-YSZ 복합체 양극 모두 120$0^{\circ}C$에 소결했을 때 가장 낮은 분극저항을 나타내었다. 또한 양극 후막의 두께가 얇아지면 양극의 in-plane 저항이 증가하여 ohmic 저항이 증가하였는데, LSM-YSZ 복합체 양극의 경우 약 30$mu extrm{m}$ 정도의 전극두께가 가장 효과적인 전극 특성을 나타내었다. 한편, LSM-YSZ 복합체 양극에 -0.5 V의 cathodic potential을 인가함에 따라 양극에서 일어나는 산소환원반응의 활성이 증가하였는데, 1가 산소이온의 표면확산반응의 분극저항은 감소하였으나, 고주파수 영역에서 나타나는 산소이온전달반응의 저항은 거의 변화하지 않았다. 이것은 Mn의 환원에 의한 양극표면에 생성된 산소공공에 기인한다.

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