• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.73-73
• /
• 2011

We will report a few methods to improve the efficiency and stability in small molecule based organic solar cells, including the formation of bulk heterojunctions (BHJs) through alternative thermal deposition (ATD), the use of a micro-cavity structure and interface modifications. By ATD which is a simple modification of conventional thermal evaporation, the thicknesses of alternative donor and acceptor layers were precisely controlled down to 0.1 nm, which is critical to form BHJs. The formation of a BHJ in copper(II) phthalocyanine (CuPc) and fullerene (C60) systems was confirmed by AFM, GISAXS and absorption measurements. From analysis of the data, we found that the CuPc|C60 films fabricated by ATD were composed of the nanometer sized disk shaped CuPc nano grains and aggregated C60, which explains the phase separation of CuPc and C60. On the other hand, the co-deposited CuPc:C60 films did not show the existence of separated CuPc nano grains in the CuPc:C60 matrix. The OPV cells fabricated using the ATD method showed significantly enhanced power conversion efficiency compared to the co-deposited OPV cells under a same composition [1]. We will also present by numerical simulation that adoption of microcavity structure in the planar heterojunction can improve the short circuit current in single and tandem OSCs [2]. Interface modifications also allowed us to achieve high efficiency and high stability OSCs.

• Journal of The Korean Association For Science Education
• /
• v.25 no.2
• /
• pp.133-145
• /
• 2005

The purpose of this study was to identify the relation between preservice teachers' philosophical views on science and types of responses to alternative hypotheses. To identify preservice teachers' philosophical views on science, the extraterrestrial impact theory and the volcano-greenhouse theory, alternative hypotheses related to dinosaur extinction were administered to 37 elementary preservice teachers and 52 secondary preservice teachers. Subjects were required to write down their ideas before and after reading the alternative hypotheses, and then the dimensions of responses to initial ideas were analyzed. To analyze, Soh's Philosophical Perspectives Prove(PPP) was used. The results of this study were as follows: (a) elementary and secondary preservice teachers' philosophical views on science corresponds to eclecticism, (b) the main types of responses were partial theory change in elementary preservice teachers and rejection in secondary preservice teachers, (c) preservice teachers' philosophical views on science and types of responses were eclecticism-partial theory change in elementary preservice teachers and eclecticism-rejection in secondary preservice teachers.

• Journal of computational fluids engineering
• /
• v.13 no.4
• /
• pp.50-57
• /
• 2008

The prediction of hydrate pellet decomposition characteristics is required to design the regasification process of GTS (gas to solid) technology, which is considered as an economic alternative for LNG technology to transport natural gas produced from small and stranded gas wells. Mathematical model based on the conservation principles, the phase equilibrium relation, equation of gas state and phase change kinetics was set up and numerical solution procedure employing volume averaged fixed grid formulation and extended enthalpy method are implemented. Initially, porous methane hydrate pellet is at uniform temperature and pressure within hydrate stable region. The pressure starts to decrease with a fixed rate down to the final pressure and is kept constant afterwards while the bounding surface of pellet is heated by convection. The predicted convective heat and mass transfer accompanied by the decomposed gas flow through hydrate/ice solid matrix is reported focused on the comparison of spherical and cylindrical pellets having the same effective radius.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.915-923
• /
• 2011

Our country is promoting the introduction of new means of transportation due to insufficient supply according to the existing demand of road traffic. Among them, manless light railroad transit is settled down as the most definite alternative. However, new traffic systems such as manless light railroad have certain difference between characteristics of hardware and software and subway system. Therefore, there will be many differences compared to the existing contingency system when accidents occur. Railway management organization has to establish railway contingency plan and acquire permission from the minister of the Ministry of Land, Transport, and Maritime Affairs. However, as commercial transportation is available, a new traffic system also should establish contingency plan. Therefore, the establishment of systematic contingency plan is suggested in order to analyze characteristics of manless light railroad in the beginning of introduction and to make contingency response available.

• The Journal of the Korean dental association
• /
• v.50 no.7
• /
• pp.384-393
• /
• 2012

Successful treatment of a badly broken down tooth with pulpal disease depends not only on good endodontic therapy, but also on good prosthetic reconstruction of the tooth after endodontic therapy is completed. The ideal treatment of endodontically treated teeth has been widely and controversially discussed. Endocrown is a restorative option for endodontically treated teeth. Endocrown design incorporates the core and short post into the crown as a single restoration. The preparation of endocrown consists of a circular equigingival butt-joint margin and central retention cavity of the entire pulp chamber instead of employing intraradicular posts. This design significantly increases the surface area of the preparation available for cementation. It is particularly useful in young patient teeth for long-term provisional restoration and in teeth with short clinical crowns. This technique represents a promising and conservative method for the treatment of endodontically treated teeth that require long-term protection and stability. Endocrown can be considered as a feasible alternative to full crowns or composite overlays for the restoration of non vital teeth.

• The Journal of Sustainable Design and Educational Environment Research
• /
• v.13 no.1
• /
• pp.41-49
• /
• 2014

Currently G-SEED certification standards was in an effort to building energy-saving and carbon emissions reduction. In this study, focusing on school facilities to suggest an alternative improve green building certification standards through data analysis and conduct an expert Delphi survey. In this study, evaluation of the existing areas of green building certification 7-5 suggest that one out. There are five proposed areas of ecology, health, function, energy and resources. Further it can add areas of economics and $LCCO_2$. Through the assessment items of foreign certification standards evaluated to the feasibility of introducing in Korea. Furthermore taking into account the characteristics of each class, kindergarten, elementary, primary, middle and high schools, College or University were broken down by purpose.

• Journal of Korean Society of Water and Wastewater
• /
• v.18 no.5
• /
• pp.573-579
• /
• 2004

Electroflotation, which is used as an alternative to sedimentation, is a separation treatment process that uses small bubbles to remove low-density particulates. Making allowances for recent collision efficiency diagram based on trajectory analysis, it is necessary to tailor zeta potential of bubbles that collide with negatively charged particles. In this paper, the study was performed to investigate the effects of magnesium and aluminium ions on zeta potential of bubbles. And, it was studied to find out factors which could affect the positively charged bubbles. Consequently, zeta potential of bubbles increased both with higher concentration of metal ions and in the acidic pH value. And, a probable principle that explained the procedure of charge reversal could be a combined mechanism with both specific adsorption of hydroxylated species and laying down of hydroxide precipitate. It also depended on the metal ion concentration in the solution to display its capacity to control the bubble surface.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2002.02a
• /
• pp.27-30
• /
• 2002

The particle velocity in superfluid helium (He II) induced by a gas dynamic shock wave impingement onto He II free surface were studied experimentally by using Schlieren visualization method with an ultra-high speed video camera. It is found form visualization results that a dark zone in the immediate vicinity of the vapor-He II interface region is formed because of the high compressibility of He II and is developed toward bulk He II with the flowing-down speed of the vapor-He II interface. The mass velocity behind a transmitted compression shock wave that is equal to the contraction speed of He II amounts to 10 m/sec, the Reynolds number of which reaches $10^{7}$. This fact suggests that the superfluid shock tube facility can be applied to an experimental facility for high Reynols number flow as an alternative to the superfluid wind tunnel.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.6
• /
• pp.187-195
• /
• 1996

Because an alternative refrigerant(HFC-134a) is being used instead of CFC-12 for automotive air-conditioning system, newly designed air-conditioning components are necessary due to changes in characteristics. Optimum design scheme for receiver dryer in an automotive air-conditioning system is described with emphases upon the volume of desiccant and container. The volume of the container, that is manufactured based on the study, is reduced down to one half of the existing receiver dryers.

• Journal of the Korean Vacuum Society
• /
• v.6 no.S1
• /
• pp.89-95
• /
• 1997

A new type of piexoelectric membrane traveling wave motor has been designed and forbricated. The small motor is composed by the stator which is the combination of annular/circular membrane and metal elastic base using as the common electrode at some time and the rotor which is placed on the metal elastic body. Thus the motor structure is simple and easy to fabricate. The material of a piezoelectric membrane is fabricated by sol-gel method or wear-down method. A piezoelectric traveling wave motor has been fabricated with the stator diameter 8mm The total thickness of the stator is 350$\mu$m. Under the alternative excitation voltage 10-12V the revolving speed of the rotor is more than 100RPM.