• Journal of Forest and Environmental Science
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• 제36권3호
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• pp.233-242
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• 2020

The Lake (Victoria) zone of Tanzania, which has the least forest resources in the country, is a potential economic growth zone in the country. Therefore, this study analyses the impact of implemented forest policies on the status of forest resources in the area, given the unique features. The study identifies the status of forested lands in the area, and then fits binary logistic regression to identify the impact of policies related elements (i.e. type of forest, type of management) on the status; forest area and location (region) are used as control variables. Results show that 63% of the forested land in the area is destructed; main activities being agriculture, residential, firewood, and charcoal burning activities. Logistic results showed natural forests, forests located in Geita region, forests managed by municipal councils are more likely to be destructed; while plantation forests, forests located in Kagera region, privately managed forests are less likely to be destructed. Thus, the study concludes that policies and measures are not enough for the preservation of forest resources in the area; some of the economic activities in the area are occurring at the expenses of the forests; hence recommend more sustainable development plans and incorporating different crossing cutting sectors in the policies.

• Asian-Australasian Journal of Animal Sciences
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• 제17권5호
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• pp.719-725
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• 2004

Mesquite or Vilayati babul (Prosopis juliflora) is a drought resistant, evergreen, spiny tree with drooping branches and a deep laterally spreading root system. It grows in semi-arid and arid tracts of tropical and sub-tropical regions of the world and is spreading because the leaves are unpalatable and animals do not digest its seed. The mesquite has become a major nuisance; cutting or pruning its branches to form a canopy would provide shade for travelers, aid harvesting of pods, as well as make available wood for fuel. An average plant starts fruiting by 3-4 years of age and yields annually 10-50 kg pods/ tree, which can be collected from May-June and September-October. Availability of pods worldwide is estimated to be about 2-4 million metric tonnes. Ripe pods are highly palatable; on dry matter basis they contain 12% crude protein, 15% free sugar, a moderate level of digestible crude protein (7% DCP) with a high level of energy (75% TDN). The pods contain low tannin levels below those toxic to animals. Seeds contain 31-37% protein; pods should be finely ground before feeding to facilitate utilization of the seeds. Mesquite pods could replace costlier feed ingredients such as grain and bran contributing 10-50% of the diet. Phosphorus supplements need to be added when mesquite pod, exceeds 20% of animals' diet.

• 대한의용생체공학회:의공학회지
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• 제24권4호
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• pp.247-257
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• 2003

This paper proposes a three-dimensional (3D) segmentation algorithm for extracting a diagnostic object from ultrasound images by using a LoG operator In the proposed algorithm, 2D cutting planes are first obtained by the equiangular revolution of a cross sectional Plane on a reference axis for a 3D volume data. In each 2D ultrasound image. a region of interest (ROI) box that is included tightly in a diagnostic object of interest is set. Inside the ROI box, a LoG operator, where the value of $\sigma$ is adaptively selected by the distance between reference points and the variance of the 2D image, extracts edges in the 2D image. In Post processing. regions of the edge image are found out by region filling, small regions in the region filled image are removed. and the contour image of the object is obtained by morphological opening finally. a 3D volume of the diagnostic object is rendered from the set of contour images obtained by post-processing. Experimental results for a tumor and gall bladder volume data show that the proposed method yields on average two times reduction in error rate over Krivanek's method when the results obtained manually are used as a reference data.

• Computers and Concrete
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• 제21권6호
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• pp.669-679
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• 2018

In this paper the behavior of reinforced concrete (RC) beam-column connections under cyclic loading was analyzed. The specimens, manufactured in a reduced-scale were made of (a) recycled aggregate concrete (RAC) by replacing 30% of natural coarse aggregate (NCA) with recycled coarse aggregate (RCA) and (b) RAC incorporating Polyethylene terephthalate (PET) fiber i.e., PET fiber-reinforced concrete (PFRC) at the joint region. PET fiber (aspect ratio=25) of 0.5% by weight of concrete used in the PFRC mix was obtained by hand cutting of post-consumer PET bottles. A reference specimen was also prepared using 100% of NCA and subjected to similar loading sequence. Comparing the results the structural behavior under cyclic loading of RAC specimens are quite similar to the reference specimens. Damage tolerance, load resisting capacity, stiffness degradation, ductility, and energy dissipation of the RAC specimens enhanced due to addition of PET fibers at the joint region. PFRC specimens also presented a lower damage indices and higher principal tensile stresses as compared to the RAC specimens. The results obtained gave experimental evidence on the feasibility of RAC for structural use. Using PET fibers as a discrete reinforcement is recommended for improving the seismic performance of RAC specimens.

• 한국생산제조학회지
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• 제21권2호
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• pp.191-195
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• 2012

Heavy flint optical glass(SF57HHT) is new material that has extremely high transmittance. Due to brittleness and high hardness, optical glass is one of the most difficult to materials for ultra-precision turning. According to the hypothesis of ductile machining, all materials, regardless of their hardness and brittleness, will undergo transition from brittle to ductile machining region below critical undefromed chip thickness. In this study, cutting test was carried out to evaluate cutting performance of heavy flint glass using ultra-precision machine with single crystal diamond bite. The machined workpiece surface topography, tool wear and surface roughness were examined using AFM and SEM. The experimental results indicate that the machining mode become the brittle mode to ductile mode, when the maximum undeformed chip thinkness is large than critical value. Tool wear mainly occurs on the flank face and its wear mechanism is dominated by abrasion. This study demonstrates the feasibility of SF57HHT by diamond turning.

• 한국작물학회지
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• 제48권3호
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• pp.147-151
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• 2003

제주지역에서 상위급 씨감자 가을채종재배 시 폴리에칠렌(PE)멀칭이 감자의 생육 및 수량성에 미치는 효과를 구명하고자 일반종서, 경삽 및 소서 플러그묘를 2001년 8월 20일에 직파 또는 정식한 후 무멀칭, 투명 및 흑색 PE멀칭재배를 하여 얻어진 결과를 요약하면 다음과 같다. 1. 주당 총서수는 멀칭처리에 큰 영향을 받지 않고 4.6개 내외였으나, 종묘종류별로는 직파구에서 5.14개로 가장 많았고 경삽묘 및 소서묘정식구에서는 각각 4.15, 5.15개였다. 2. 총서수량은 무멀칭구에서 21.16톤/ha이었는데, 투명 및 흑색 PE멀칭에 의하여 각각 16, 8% 증수되었고, 경삽묘정식구가 가장 많았으며 다음으로 소서묘, 직파구 순이었다. 3. 평균서중은 무멀칭구에서 평균 72.2g이었고 투명 및 흑색 PE멀칭에 의하여 각각 14, 12%증가되었는데, 멀칭효과는 경삽묘정식구에서 가장 컸었다.

• 대한의용생체공학회:의공학회지
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• 제15권3호
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• pp.237-244
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• 1994

1Hz에서 20Hz까지의 단속 주파수를 지닌 청각자극을 가해 얻은 EEG 신호에서 자극에 따른 신호의 정성적이고 정량적인 특성을 카오스 분석방법을 통해 밝혔다. 먼저, 뇌전위 신호에 전반적으로 나타나는 일반적인 카오스 특징(fractal mechanism, I/f frequency spectrum, positive Lyapunov exponent 등등)을 확인하였다. 유발전위에 대해서는 자극의 주파수에 따른 주기배증을 경유한 카오스로 가는 길(route to chaos)과 2차원 pseudo-Phase portrait의 뿌앙까레 단면에서의 기하학적 모양(topological property)의 변화를 관찰하였고, 자발전위가 포함된 유발전위에 대해서는 적절한 bases를 지닌 3차원 phase space에서 기이한 끌개(chaotic attractor)가, 유발전위의 정보를 지닌채 보여졌다. 끝으로 자극 주파수(단속 주파수)변화와 측정이 이루어진 머리표면에서의 공간적 위치에 따른 Lyapunov exponent값 변화를 의미있게 해석하였다. 이 결과는 무질서하게 보이는 뇌전위신호에서 주어진 청각자극에 대한 정보를 얻는 새로운 방법을 제시하게 된다.

• 한국초지조사료학회지
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• 제29권2호
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• pp.111-120
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• 2009

조사료 생산에 유망한 동계작물중 보리, 밀, 호밀, 귀리, 트리티케일(라이밀) 등 5종의 총체맥류에 대하여 월동 후 예취시기에 따른 생육 및 조사료 생산성에 관한 생장곡선을 조사하기 위하여 충남 예산군 소재의 충남농업기술원 답리작 포장에서 2006${\sim}$2007년에 수행한 결과는 다음과 같다. 지상부 건물중에서 줄기가 차지하는 비율은 월동 후 점차 증가하다가 어느 정점부터는 감소하는 2차원적인 경향을 보였는데, 줄기의 구성비율이 최고가 되는 시기는 각각 영양 보리 5월 1일, 금강 밀 5월 5일, 곡우 호밀 5월 10일, 신영 트리티케일 5월 11일, 삼한 귀리 5월 13일경이었다. 잎은 월동 후 성숙이 진행될수록 직선적으로 감소하는 경향을 보였다. 이삭이 차지하는 비율은 영양 보리가 출수 후 직선적으로 증가하였는데 밀, 트리티케일, 귀리에 비하여 높았고, 호밀이 가장 낮았다. 영양 보리가 출수기 이후에 다른 총체맥류에 비하여 줄기의 구성비율이 낮고 이삭과 잎의 구성비율이 높은 전형적인 총체맥류에 속하였고, 다음은 밀과 귀리이었으며, 호밀은 알곡 비율이 적은 조사료 작물에 해당하였다. 사일리지 제조에 알맞은 수분 함량(60${\sim}$ 70%에 도달하는 시기는 영양 보리 5월 25일, 금강 밀 5월 25일${\sim}$6월 5일, 삼한 귀리 6월 5일이었고, 이 때 생체수량은 곡우호밀>삼한 귀리>신영 트리티케일>영양 보리>금강 밀 순으로 높았다. 생체수량은 월동 후 생육이 진전됨에 따라 증가하다가 일정시기 이후 감소하는 경향을 보였는데, 중부지역에서 생체수량이 최대로 되는 시기는 영양 보리 5월 7일경, 금강 밀 5월 14경, 곡우 호밀 5월 9일, 신영 트리티케일 5월 17일경, 삼한 귀리 5월 말이었다. 건물수량은 4종의 총체맥류 모두 월동 후 성숙기까지 직선적으로 증가하는 양상을 보였고, 사일리지 제조에 알맞은 수분 함량에 도달하는 시기에 조사한 건물수량은 귀리 > 보리 > 밀 > 트리티케일 > 호밀 순으로 높았다. 상대 생장률은 월동 후 서서히 증가하다가 정점 이후로 감소하는 2차원적인 생장을 보였는데, 월동 후 예취시기가 빠를수록 곡우 호밀이 높은 상대생장률을 보였고, 예취시기가 늦을수록 삼한 귀리가 높았으며, 금강 밀, 영양 보리, 신영 트리티케일은 비슷한 상대생장률을 보였다.

• 열처리공학회지
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• 제18권1호
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• pp.29-40
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• 2005

Formation of nanocrystalline ferrite was investigated using milled powders obtained by planetary ball milling of chips, which were made by high speed mechanical cutting of a low carbon steel(0.15%C-1.1%Mn-0.01%Ti). After 4 hour milling the chips were changed to powders of $50{\mu}m$ in average size, and with increasing milling time the powders were refined to about $3{\mu}m$ for 128 hour and showed more equiaxed shapes. Nanocrystalline(nc) region appeared in the surfaces of powders milled for 1 hour, and the 4 hour milled powders were almost filled with nc region. Hardness of nc region was much higher than that of work-hardened(WH) region. With increasing milling time, ferrite and cementite in pearlite were severely deformed and lamellar spacing was decreased, and then cementites began to disappear after 4 hour milling due to dissolution into ferrite. Deformation bands formed in lightly work-hardened region showed large width and similar crystallographic orientations. Spacing of deformation bands was decreased with deformation and the layered microstructure consisting of narrow deformation bands subdivided into variously oriented small grains was formed by more deformation, and eventually this structure seemed to be evolved to the nc structure by further deformation. It is also conjectured the growth of nc ferrite grains occurred through the coalescence of nanocrystalline ferrites rather than the nucleation and growth of recrystallized grains.

• Journal of Welding and Joining
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• 제17권3호
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• pp.79-89
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• 1999

The study was carried out to examine in more detail metallurgical and mechanical properties of brazed joints of diamond cutting wheel. In this work, shank(mild steel) and sintered bronze-base tips were brazed with three different filler materials(W-40, BAgl and BAg3S). The machine used in this work was a high frequency induction brazing equipment. The joint thickness, porosities and microstructure of brazed joints with brazing variables(brazing temperature, holding time) were evaluated with OLM, SEM, EDS and XRD. Bending(torque) test was also performed to evaluate strength of brazed joints. Further wetting test was performed in a vacuum furnace in order to evaluate the wettability of filler metals on base metals9shank and tips). The brazing temperature had a strong influence on the joint strength and the optimum brazing temperature range was about $700~850^{\circ}C$ for the bronze/steel combinations. The strength of the brazed joint was found to be influenced by the three factors : degree of reaction region, porosity content, joint thickness. The reaction region was formed in the bronze-base tip adjacent to the joint. The reaction region resulted in a bad influence on the strength due to the formation of Cu5.6Sn, CuZn4, $\beta(CuZn)$ and CdAg, etc. Porosities increased as brazing variables(brazing temperature, holding time) increased, and the brazed joints with porosities of less than about 3-5% had an optimum strength for the bronze-base tip.