The Relationship between Nanocluster Precipitation and Thermal Conductivity in Si/Ge Amorphous Multilayer Films: Effects of Cu Addition

We have used a molecular dynamics technique to simulate the relationship between nanocluster precipitation and thermal conductivity in Si/Ge amorphous multilayer films, with and without Cu addition. In the study, the Green-Kubo equation was used to calculate thermal conductivity in these materials. Five specimens were prepared: Si/Ge layers, Si/(Ge + Cu) layers, (Si + Cu)/(Ge + Cu) layers, Si/Cu/Ge/Cu layers, and Si/Cu/Ge layers. The number of precipitated nanoclusters in these specimens, which is defined as the number of four-coordinate atoms, was counted along the lateral direction of the specimens. The observed results of precipitate formation were considered in relation to the thermal conductivity results. Enhancement of precipitation of nanoclusters by Cu addition, that is, densification of four-coordinate atoms, can prevent the increment of thermal conductivity. Cu dopant increases the thermal conductivity of these materials. Combining these two points, we concluded that Si/Cu/Ge is the best structure to improve the conversion efficiency of the Si/Ge amorphous multilayer films

A Consideration of Life Cycle Cost of a Ship

This chapter analyzes main items of fabrication cost and maintenance cost of a ship focusing on hull structure part, based on the actual data from shipyards and ship owners and the relations between these costs. Fabrication cost occupies more than 30%. Hull structural part occupies about 50% and outfitting part occupies about 15%, depending on the features of ships. Building cost is a part of life cycle cost and occupies a big amount. It is considered that building cost occupies about 2/3 of life cycle cost and maintenance cost occupies about 1/3. Material cost of a ship occupies a big amount and reaches to 50–60 % of the total building cost. Among material costs, steel cost is the biggest one and occupies 35%. By increasing the application ratio of higher tensile strength steel from 23% to 80% of hull structural steel, total steel weight is reduced by about 6% and building cost is reduced by about 1%. Maintenance costs are influenced by the management policies of ship owners. Inspections are generally made at periodical survey and intermediate survey in accordance with ship classification rules. In some ships, self inspections are made by ship owners and crews. By utilizing this information the scopes and costs of repairs are estimated. By applying heavy duty painting to very large crude oil carrier (VLCC) at the building stage the life cycle cost will be reduced by about 3% compared with an ordinarily painted one

Nanopore Formation in CeO₂ Single Crystal by Ion Irradiation: A Molecular Dynamics Study

The nanopore formation process that occurs by supplying a thermal spike to single crystal CeO2 has been simulated using a molecular dynamics method. As the initial condition, high thermal energy was supplied to the atoms in a nano-cylinder placed at the center of a fluorite structure. A nanopore was generated abruptly at around 0.3 ps after the irradiation, grew to its maximum size at 0.5 ps, shrank during the time to 1.0 ps, and finally equilibrated. The nanopore size increased with increasing effective stopping power gSe (i.e., the thermal energy deposited per unit length in the specimen), but it became saturated when gSe was 0.8 keV/nm or more. This finding will provide useful information for precise control of the size of nanopores. Our simulation confirmed nanopore formation found in the actual experiment, irradiation of CeO2 with swift heavy ions, but could not reproduce crystalline hillock formation just above the nanopores