• 한국세라믹학회지
• /
• 제54권2호
• /
• pp.75-85
• /
• 2017

Thermoelectric is a key technology for energy harvesting and solid-state cooling by direct thermal-to-electric energy conversion (or vice versa); however, the relatively low efficiency has limited thermoelectric systems to niche applications such as space power generation and small-scale or high-density cooling. To expand into larger scale power generation and cooling applications such as ATEG (automotive thermoelectric generators) and HVAC (heating, ventilation, and air conditioning), high-performance bulk thermoelectric materials and their low-cost processing are essential prerequisites. Recently, the performance of commercial thermoelectric materials including $Bi_2Te_3$-, PbTe-, skutterudite-, and half-Heusler-based compounds has been significantly improved through non-equilibrium processing technologies for defect engineering. This review summarizes material design approaches for the formation of multi-dimensional and multi-scale defect structures that can be used to manipulate both the electronic and thermal transport properties, and our recent progress in the synthesis of conventional thermoelectric materials with defect structures is described.

• Journal of Power Electronics
• /
• 제10권6호
• /
• pp.784-791
• /
• 2010

In this paper, a resonant pulse power converter (RPPC) is proposed. The proposed RPPC transfers the pulse-shape power from a DC source to a load periodically. The RPPC consists of a resonant circuit and a resonant pulse converter driven by a self-switching circuit. Depending on the magnitude difference between the input and output voltages, the operations of the RPPC are divided into 4 modes; boost mode, hybrid mode, direct mode and cut-off mode, respectively. The main switch of the RPPC turns on in the ZCS condition and off in the ZVS condition spontaneously. The operational principles of a RPPC using the self-switching technique are analyzed and verified in experiments. An example of a RPPC application is demonstrated in the area of thermoelectric energy harvesting.

• 한국세라믹학회지
• /
• 제55권3호
• /
• pp.203-223
• /
• 2018

The development of two-dimensional graphene layers has recently attracted considerable attention because of its tremendous application in various research fields. Semi-metal materials have received significant attention because of their excellent biocompatibility as well as distinct physical, chemical, and mechanical properties. Taking into account the technical importance of graphene in various fields, such as complementary metal-oxide-semiconductor technology, energy-harvesting and -storage devices, biotechnology, electronics, light-emitting diodes, and wearable and flexible applications, it is considered to be a multifunctional component. In this regard, material scientists and researchers have primarily focused on two typical problems: i) direct growth and ii) low-temperature growth of graphene. In this review, we have considered only cold growth of graphene. The review is divided into five sections. Sections 1 and 2 explain the typical characteristics of graphene with a short history and the growth methods adopted, respectively. Graphene's direct growth at low temperatures on a required substrate with a well-established application is then precisely discussed in Sections 3 and 4. Finally, a summary of the review along with future challenges is described in Section 5.

• 한국환경과학회지
• /
• 제24권2호
• /
• pp.253-260
• /
• 2015

Enlargement of street tree planting area is the proper and effective solution to reduce carbon dioxide. This solution bases on the ability of carbon storage and uptake by tree metabolism. However, the circumstance of road side has fatal disadvantages in tree metabolism such as growth and maturity because cutting and filling of roadsides cause unnatural soil composition. In this point, early rootage of street tree is the main factor of reducing carbon dioxide. This study aimed to find a appropriate transplantation planting method for sound and rapid rootage of street tree. For the study, Korean Mountain Ash(Sorbus alnifolia) were used for experimental groups. The groups were categorized by three groups such as trees produced on container with mulching treatment, trees produced in outdoor with mulching treatment, trees produced on container with weeding treatment. Each group consisted 10 trees with same size and transplanted in experimental site. Five months after transplanting, each group was estimated the biomass and carbon storage through a direct harvesting method. According to results of the study, the carbon storage of trees produced on container with mulching treatment is 42% more than trees produced in outdoor with mulching treatment. And the carbon storage of trees produced on container with mulching treatment is 19.5% more than trees produced on container with weeding treatment. These results may imply that transplantation of container produced tree with mulching treatment is the most rapid rootage among other groups. The weeding treatment is more effective than mulching treatment for rapid rootage of street trees.

• 농업과학연구
• /
• 제24권1호
• /
• pp.85-93
• /
• 1997

This paper is aimed to study on sales promotion strategies for the increment of farm income by cultivating Boxthron in Chongyang Area. Marketing Survey was done in Chongyang Boxthron market, Kyoung-dong herb market in Seoul. The results are as follows ; Reviewing the Boxthron market prices, the price of direct transaction was the highest one and that of Agricultural Cooperatives was next one, Chongyang market price was lowest one. Therefore, the efforts including exclusive labeling, high class packing strategies of Boxthron with lower pollution would be necessary. The seasonal variation Boxthron prices were lowest in Aug.-Sept., harvesting season, and highest in april-june prices, off-crop season. Farmers have sold 45% of all products in Aug.-Oct. at lowest price and the remaining 15% of that sold in april-june at the highest prices. On account of the above reasons, loan for Boxthron production, government purchasing and storage program of it especially in harvesting season from Aug. to Oct. should be adopted to increase Boxthron producer income. Finally, the strategies for sales promotion, enforcement of government supporting activities including export strategies and the development of new processed products of Boxthron should be propelled considering the products cycle.

• 한국작물학회지
• /
• 제36권1호
• /
• pp.79-84
• /
• 1991

기계수확시 탈립된 종자들이 이듬해 발아 생장하여 휴경조건하에서 수량 및 수량구성 요소에 많은 변이를 보였기에 무경운 직파재배의 가능성을 타진하려 수도의 수량 및 수량구성요소를 조사하였고 또한 잡초종의 피도에 따른 수량변이를 상관계수를 통해 알아보았다. 무경운 무시비 조건에서도 단위면적당 최대 188kg/10a의 수량을 보여 입모확보가 보장된다면 무경운 직파재배는 가능할 것으로 판단되었다. 또한 성공적 무경운 직파를 위해서는 충분한 입모확보, 천이, 두과식물과의 적절한 혼파 초형개발에 관한 연구가 기대된다.

• 한국소음진동공학회논문집
• /
• 제22권9호
• /
• pp.896-902
• /
• 2012

For most applications of the vibration energy harvesting technology as in wireless sensor networks for smart buildings and plants, the evaluation of DC output performance of vibration energy harvesters is typically required. However, there is no dedicated algorithm for the evaluation. The lack of a dedicated algorithm results from difficulties in the direct incorporation of nonlinear rectifying and regulating circuitry into finite element models of piezoelectric vibration energy harvesters. In this study, we develop a dedicated algorithm and present software based on it for the evaluation of not only AC but also DC electrical quantities. Here, an equivalent electrical circuit model is employed. The COMSOL multiphysics simulation tool is adopted for extracting equivalent electrical circuit parameters of a piezoelectric vibration energy harvester and MATLAB is used to make a graphical user interface. The AC voltage and power outputs calculated by the proposed algorithm under various conditions are compared with those by a traditional finite element analysis. The DC output voltage and power through a rectifier are obtained for varying values of smoothing capacitance and external resistance.

• Ocean and Polar Research
• /
• 제31권4호
• /
• pp.305-318
• /
• 2009

A marine ranching project in Tongyoung was established in 1998, lasting 9 years to 2006. Project activities included the deployment of artificial reefs, the release of young fishes like jacopever and rockfish, and input/output control for specific marine ranching areas in Tongyoung. This report focuses on the economic feasibility of the project in hindsight. Analysis concentrates on three aspects; (a) direct economic benefits, such as increasing effects of fisheries income and savings in harvesting costs, (b) indirect benefits, including increasing effects of recreational fishing and saving R&D costs, and (c) costs, including releasing and purchasing costs of artificial reef and juvenile fish, R&D costs, maintenance costs and harvesting costs. Results show that NPV=4.7 billion won, IRR=8.55% and B/C ratio=1.286 under Scenario 1, which considers the saving effects of R&D costs, and NPV=0.9 billion won, IRR=6.03% and B/C ratio=1.11 under Scenario 2, which does not consider the saving effects of R&D costs, based on 5.5% of the social rate of discount. According to sensitivity analysis, the economic feasibility is very sensitive to the recapture rate.

• Wind and Structures
• /
• 제26권5호
• /
• pp.279-292
• /
• 2018

Inspired by the energy harvesting eel, a flexible flag behind a D-shape cylinder in a uniform viscous flow was simulated by using the immersed boundary method (IBM) along with low-speed wind tunnel experimentation. The flag in the wake of the cylinder was strongly influenced by the vortices shed from the upstream cylinder under the vortex-vortex and vortex-body interactions. Geometric and flow parameters were optimized for the flexible flag subjected to passive flapping. The influence of length and bending coefficient of the flexible flag, the diameters (D) of the cylinder and the streamwise spacing between the cylinder and the flag, on the energy generation was examined. Constructive and destructive vortex interaction modes, unidirectional and bidirectional bending and the different flapping frequency were found which explained the variations in the energy of the downstream flag. Voltage output and flapping behavior of the flag were also observed experimentally to find a more direct relationship between the bending of the flag and its power generation.

• 한국유기농업학회지
• /
• 제7권2호
• /
• pp.153-161
• /
• 1999

No-till direct-sown rice-wheat relaying cropping system has major advantages such as labor and cost saving by eliminating tillage and preparation of seed bed and transplanting. In this system, rice sowing was done simultaneously wheat harvesting. A paddy field experiment was conducted to evaluate effects of no-till years on soil microbial changes and soil physico-chemical characteristics with rice growth and development. Chemical fertilizers and agricultrual chemicals was not applied in no-till system. As the year in no-till direct-sown system the air permeability was increased and after water submerging soluble nitrogen was released Aerobic microbial-n was highest in May and then decreased after water irrigation. The population of aerobic soil microorganisms were steeply decreased after water submerging Soil microorganisms was decreased with the increased the soil depth. A month was needed for the seedling establishment in a no-tillage rice-wheat cropping system. Increased cropping years improved leaf greenness and leaf area index(LAI). But stomatal conductance(Gc) was higher in conventional cultivation system than no-till system. Stomatal conductance at panicle initiation stage was increased higher in conventional condition of leaves but the difference between conventional and no-till system was increased at heading stage. In no-till 4 years condition rice grain yield was spikelet numbers per panicle.