Kovalenko's Full-Rank Limit and Overhead as Lower Bounds for Error-Performances of LDPC and LT Codes over Binary Erasure Channels

We present Kovalenko's full-rank limit as a tight lower bound for decoding error probability of LDPC codes and LT codes over BEC. From the limit, we derive a full-rank overhead as a lower bound for stable overheads for successful maximum-likelihood decoding of the codes.Comment: A short version of this paper was presented at ISITA 2008, Auckland NZ. The first draft was submitted to IEEE Transactions on Information Theory, 2008/0

Thermal stress analysis of double-ceramic-layered thermal barrier coatings based on rare earth element

So far, many studies have been conducted to increase the operating temperature of gas turbine engine because it enables to achieve the high efficiency with lower emission. As a part of continuous studies, various thermal barrier coatings (TBCs) have been applied onto hot-components as an efficient thermal insulating system. A typical TBC system consists of four layers: a metallic substrate, bond-coats, top-coats and thermally grown oxide between bond-coats and top-coats. Conventionally, top-coats are made of ceramic material such as 8% mol yttria stabilized zirconia (8YSZ) because of its low conductivity. However, 8YSZ based TBC suffers from considerable damage during the operating above 1200° due to the phase transformation and sintering, resulting in volume change and a decrease of strain tolerance.1 Therefore, several oxide groups having the pyrochlore or fluorite structure are recommended to replace 8YSZ. To date, La2Zr2O7 (LZ), La2Ce2O7 (LC), LaTi2Al9O19 (LTA) and Sr(Zr0.9Yb0.1)O2.95(SZYb) are of high interest.1-3 Besides, double ceramic layer (DCL) is also applied on the bond-coats to improve the durability of TBC. Generally, the first top-coat (TC1) is made of the conventional 8YSZ as stress buffer on the bond-coats. Then, an alternative material is deposited as the second top-coat (TC2). In this study, using finite element (FE) analysis, we investigate thermal stress of the DCL typed TBC based on candidate materials when they have the same thermal insulating capacity above 1200°. As shown in fig. 1, a periodic FE model is constructed by taking both thermo-mechanical behavior and topological characteristics into account. Assuming that the turbine inlet temperature is 1500°, the surface of TC2 is heated by impinging gas of 1300° and the substrate is cooled by the internal cooling air equivalent to 700° for 3 cycles. As a result, the system having the lowest thermal stress is LC, followed by LTA, SZYb, and LZ. For all materials, the maximum stress always occurs during the heating period. Remarkably, the position and the moment where the maximum stress occurs are all different. The maximum stress is observed at the vicinity of the wavy oxide layer or TC2. But its moment is irregular such that it may occur at either the highest temperature or the room temperature. Consequently, it can be assumed that the service life is affected by not only the highest temperature but also the temperature difference during the operating cycle. Although LC is determined as the most suitable system to the given specific operation condition, there would exist the other optimal systems for different operation conditions, which can be further investigated by the proposed FE analysis in this study. Please click Additional Files below to see the full abstract

The Role of Government to Bridge Digital Gap between Urban and Rural Area in Korea

The Ministry of Food, Agriculture, Forestry and Fisheries (MIFAFF) in Korea has made an abundant effort to develop agricultural/rural informatization since the 1990’s. Initially, it focused on the development of three different types of infrastructure to bridge the gap between rural and urban areas: household personal computer (PC) penetration, Internet use, and broadband Internet connection accessibility. The 81% of broadband accessibility in 2002 increased to 100% in rural areas in 2007. In addition, from 1998 to 2002, a total of 241,356 farmers took diverse education programs provided by MIFAFF. As a big effort from MIFAFF, Food and Agro-product e-commerce of Farmers has also increased continuously; as of 2009, its transaction is estimated as 1.89 billion USD. Many projects on u-Farm have been launched for future intelligent farming. However, MIFAFF are now facing new challenges

Extract of Allium tuberosum Rottler ex Spreng

Allium tuberosum Rottler ex Spreng (ATRES) has been used as a traditional medicine for the treatment of abdominal pain, diarrhea, and asthma. In this study, we investigated the hair growth promoting activities of ATRES on telogenic C57BL6/N mice. Hair growth was significantly increased in the dorsal skin of ethanol extract of ATRES treated mouse group compared with the control mouse group. To enrich the hair promoting activity, an ethanol-insoluble fraction was further extracted in sequence with n-hexane, dichloromethane, ethyl acetate, n-butanol, and distilled water. Interestingly, we found that extraction with n-butanol is most efficient in producing the hair promoting activity. In addition, the soluble fraction of the n-butanol extract was further separated by silica gel chromatography and thin layer chromatography (TLC) resulting in isolating four single fractions which have hair growth regeneration potential. Furthermore, administration of ATRES extracts to dorsal skin area increased the number of hair follicles compared with control mouse group. Interestingly, administration of ATRES extract stimulated the expression of insulin-like growth factor-1 (IGF-1) but not of keratin growth factor (KGF) or vascular endothelial growth factor (VEGF). Taken together, these results suggest that ATRES possesses strong hair growth promoting potential which controls the expression of IGF-1

Bis[μ-N-(pyridin-2-ylmeth­yl)pyridin-2-amine-κ2 N:N′]disilver(I) bis(trifluoro­methane­sulfonate)

In the binuclear title compound, [Ag2(C11H11N3)2](CF3O3S)2, the complex cation is centrosymmetric, with the unique Ag+ cation coordinated by two pyridine N atoms from two symmetry-related N-(pyridin-2-ylmeth­yl)pyridin-2-amine ligands in a geometry slightly distorted from linear [N—Ag—N 161.02 (7)°]. This set-up leads to the formation of a 14-membered cyclic dimer. The two pyridine rings coordinated to the Ag+ cation are tilted by 80.19 (7)° with respect to each other. Inter­molecular N—H⋯O hydrogen-bonding inter­actions between the cyclic dimer and the anion exist. A two-dimensional network parallel to the ac plane is constructed by three weak Ag⋯(O,N) inter­actions as well as an F⋯F contact of 2.890 (4) Å

Analysis of Change in the Wind Speed Ratio according to Apartment Layout and Solutions

Apartment complexes in various forms are built in downtown areas. The arrangement of an apartment complex has great influence on the wind flow inside it. There are issues of residents’ walking due to gust occurrence within apartment complexes, problems with pollutant emission due to airflow congestion, and heat island and cool island phenomena in apartment complexes. Currently, the forms of internal arrangements of apartment complexes are divided into the flat type and the tower type. In the present study, a wind tunnel experiment and computational fluid dynamics (CFD) simulation were performed with respect to internal wind flows in different apartment arrangement forms. Findings of the wind tunnel experiment showed that the internal form and arrangement of an apartment complex had significant influence on its internal airflow. The wind velocity of the buildings increased by 80% at maximum due to the proximity effects between the buildings. The CFD simulation for relaxing such wind flows indicated that the wind velocity reduced by 40% or more at maximum when the paths between the lateral sides of the buildings were extended