• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권9호
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• pp.2173-2193
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• 2013

In order to reduce the distribution cost of sensor nodes, a mobile sensor deployment has been proposed. The mobile sensor deployment can be solved by finding the optimal layout and planning the movement of sensor nodes with minimum energy consumption. However, previous studies have not sufficiently addressed these issues with an efficient way. Therefore, we propose a new deployment approach satisfying these features, namely a tree-based approach. In the tree-based approach, we propose three matching schemes. These matching schemes match each sensor node to a vertex in a rake tree, which can be trivially transformed to the target layout. In our experiments, the tree-based approach successfully deploys the sensor nodes in the optimal layout and consumes less energy than previous works.

• 한국정보처리학회논문지
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• 제4권3호
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• pp.709-719
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• 1997

알고리즘의 성능은 여러 측면에서 측정할 수 있다 하나의 질의 구성(Quvery Formulaiton)알고리즘이 개발되었다고 가정할때, 이 알고리즘 검색 성능의 효과과성 (재현율과 정확율)이 다른 알고리즘에 비해 우수하다하였도 질의 작성 시간적인 측면, 즉 효율성에서 다른 알고리즘에 뒤진다면 모든 면에서 우수하다고 평가하기 어렵다.본 연구에서는 질의나무(Query tree)라고 불리는 자동 질의 재구성 알고리즘과 다른 2개의 알고리즘(DNF method,Dilon's method)을 이론적 측면과 실시간 측정에 Sun SparcsStation 2를 이용하여 비교하여 보았다. 3가지 Test set 인 CACM,CISI,그리고 Medlars을 이용하여 실험한 질과 질의나무 알고리즘이 이론적, 실시간 측면 모두에서 가장빠른 알고리즘이라는 결과가 나왔다.

• 한국농공학회지
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• 제17권3호
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• pp.3860-3871
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• 1975

This experiment was carried out to establish the mechanized methods in stumping and root-clearing, which were the most important works in the reclamation of sloping uplands. The determination of optimum teeth interval of rake blades and its operation methods to reduce the quantity of transported topsoil during the works, are the aims of this investigation. A newly designed rake blade, whose net teeth intervals could be regulated by three stages as 15cm, 25cm, and 35cm, was manufactured to attach to the bulldozer of 13ton. The experiments were carried out at Kilsang-Myon, Kwangwha-Gun, from Aug. 9 to Aug. 23, 1975. For each interval, 36 test plots of 50${\times}$10mn in size, which were regulated under three levels of land slopes of 10, 20, and 30% and two different tree stand density of high or medium values, were randomly chosen and arranged by two-replicated split-split plot design. Each stump classified by its diameter was stumped and cleared by the rake dozer to be related between diameter and stumping time. The results obtained in this experiment can be summarized as follows: 1. Stumping times for the diameters ranging from 6 to 18cm of stumps are almost the same and they are not varied by the difference of teeth intervals of rake dozer. 2. By back-ward stumping method, the number of stumps which can be stumped per hour ranges almost from 100 to 170, showing significant difference with respect to the teeth intervals. The working area is sharply varied with not only the stand density of stumps but the teeth intervals. 3. Optimum stumping distance for each teeth interval of rake dozer to minimize the quantity of transported topsoil are varied with such the rates as it is 15m or 20m for 15cm of teeth interval, but 25m for 25cm or 35cm, respectively. The clearing distance could be chosen almost double as long as the operating distance. 4. The working areas per hour of the simultaneous stumping and clearing methods are no significant difference among the various treatments of working conditions, but they are affected by the operating techniques. However, the influencing factors of the working conditions as classified before and the working directions are ranged from 10 to 15 per cent of total working area, respectively. 5. The residual rates of stumps which are not stumped by the rake dozer in each test plot are generally reduced as the teeth interval gets narrower, but there are no significant difference among them. The mean residual rates average to be about 4% for the simultaneous stumping and clearing method. The back-ward stumping method are recommended to be supervised and directed by more than one man, to show the operator where the stumps are located. 6. The results according to the stumping and clearing methods are summarized as Table IV-2. And the selection of working methods is recommended to follow as shown in Fig. IV-9 with respect to the stand density of the field. 7. Generally speaking, the narrower the teeth interval, the better become the working results, but the more the quantity of transported topsoil is increased. Therefore, it is recommended that the teeth interval should be reduced from the present distance of more than 30cm to 25cm or 15cm, by developing suitable working methods through more field works and experiments.

• 대한기계학회논문집B
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• 제26권9호
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• pp.1292-1301
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• 2002

An experimental study of turbine performance is conducted with various incidence angles on a rotating turbine rotor. 5 different incidence angles are applied from -17$^{\circ}$to 13$^{\circ}$with 7.5$^{\circ}$gaps. In order to precisely set up the incidence angles at the rotor inlet, 5 turbine discs are manufactured with the different fir tree section. Total-to-total efficiencies are obtained on the several off-design points with considering the exit total pressure, which is meas fred at 12 locations between the hub and casing using a pressure rake. The degree of reaction is 0.373 at the mean radius, and Reynolds number based on the rotor chord is 0.86$\times$10$^{5}$ at the turbine inlet on the design point experiment. The experiment on a single-stage turbine is conducted at the low-pressure and low-speed state, but it is sufficient to consider the blade loading effect due to the rotating apparatus even though the total pressure loss at the exit is increased proportionally to the turbine output power. The experimental results recommend 6$^{\circ}$as an optimum incidence angle on the turbine blade design. The total-to-total efficiency is steeply decreased when the incidence angle is over $\pm$9$^{\circ}$ from the optimum incidence angle. In the range of less than -10$^{\circ}$incidence angle, 7.5$^{\circ}$ reduction of incidence angle generates 15% decrease of total-to-total efficiency. This result is obtained on the same rotor blade by changing only the rotational speed to minimize the effect of profile and secondary flow loss in the passage. Experimental results show that the change rate of total-to-total efficiency according to the incidence angle change is unchanged although the turbine operates at the off-design condition.