The experimental investigations of recirculated exhaust gas on exhaust emissions in a diesel engine

The effects of recirculated exhaust gas on the characteristics of NOx and soot emissions under a wide range of engine loads were experimentally investigated by using a four-cycle, four-cylinder, swirl chamber type, water-cooled diesel engine operating at three engine speeds. The purpose of this study was to develop the EGR-control system for reducing NOx and soot emissions simultaneously in diesel engines. The EGR system is used to reduce NOx emissions, and a novel diesel soot removal device with a cylinder-type scrubber for the experiment system was specially designed and manufactured to reduce soot contents in the recirculated exhaust gas to the intake system of the engine. The experiments were performed at the fixed fuel injection timing of 4° ATDC regardless of experimental conditions. It was found that soot emissions in exhaust gases were reduced by 20 to 70% when the scrubber was applied in the range of the experimental conditions, and that NOx emissions decreased markedly, especially at higher loads, while soot emissions increased owing to the decrease in intake and exhaust oxygen concentrations, and the increase in equivalence ratio as the EGR rate is elevated.     

Dynamic behavior of composite joints in hydrodynamic ram simulator

The fracture behavior of carbon/epoxy composite joint structures under highly dynamic pressure loading was studied experimentally and numerically. The considered dynamic pressure loading, called hydrodynamic ram (HRAM), potentially causes fractures in structures filled with fluid. First, experiments using the HRAM simulator method were carried out to monitor the fracture behavior of the composite joint structure. In the experiment, highly dynamic pressure loading was generated which propagated and initiated the fracture of the composite joint. Next, numerical simulation was performed through finite element analysis using LS-DYNA. The dynamic pressure loading inside the fluid was predicted using the arbitrary Eulerian Lagrangian (ALE) method and the fracture behavior of the composite joint structure was simulated using cohesive zone modeling (CZM). The analysis was validated by comparing the predicted results with those from the experiment. The predicted pressure loadings were well-matched with the experimentally measured ones. The strain histories and failure strain values obtained by the analysis also agreed reasonably well compared to those in the experiment for selected points in the composite structure. Finally, the effects of impact velocity and the stiffness of the joint structure on the fracture behavior were examined.

     

Condition monitoring scheme via one-class support vector machine and multivariate control charts

A condition-based maintenance (CBM) has been widely employed to reduce maintenance cost by predicting the health status of many complex systems in prognostics and health management (PHM) framework. Recently, multivariate control charts used in statistical process control (SPC) have been actively introduced as monitoring technology. In this paper, we propose a condition monitoring scheme to monitor the health status of the system of interest. In our condition monitoring scheme, we first define reference data set using one-class support vector machine (OC-SVM) to construct the control limit of multivariate control charts in phase I. Then, parametric control chart or non-parametric control chart is selected according to the results from multivariate normality tests. The proposed condition monitoring scheme is applied to sensor data of two anemometers to evaluate the performance of fault detection power.

     

Biocompatibility of surface treated pure titanium and titanium alloy by<Emphasis Type="Italic">in vivo</Emphasis> and<Emphasis Type="Italic">in vitro</Emphasis> test

In the present study, commercial pure Ti and Ti-6Al-4V alloy specimens with and without alkali and heat treatments were implanted in the abdominal connective tissue of mice. Conventional stainless steel 316L was also implanted for comparison. After three months, their biocompatibility was evaluated byin vitro andin vivo experiments. Surface structural changes of specimens due to the alkali treatment and soaking in Hank’s solution were analyzed by XRD, SEM, XPS and AES. An apatite layer, which accelerates the connection with bone, was formed more easily on the alkali treated specimens than the non-treated specimens. The number of macrophages, which is known to increase as the inflammatory reaction proceeds, was much lower for the alkali and heat treated specimens than for the others. The average thickness of the fibrous capsule formed around the implant was much thinner for the alkali and heat treated specimens than for the others.     

Ink-jet printed transparent and flexible electrodes based on silver nanoparticles

In recent, silver (Ag) nanowires (NWs) have received much attention as an alternative to indium tin oxide (ITO) for transparent electrode application in printed and transparent electronics. However, Ag NWs have its breakup problem by joule heating during current. To overcome this problem, this paper demonstrates a mesh type electrode based on Ag nanoparticles, which is fabricated on PET substrate through an ink-jet printing technique. The proposed electrode has a low resistance of 108.5 Ω/sq and a good optical transparency around 92% at 300–800 nm. It has a relationship that the sheet resistance drops with the decrease of transparency due to depending hole size and the best curing temperature is found to be 120 °C. It also demonstrate an excellent flexible stability, showing <?2% resistance change after over 100 bending cycles. These resistance and transparency are similar with that of commercially ITO electrode, and are superior to other alternatives such as carbon nanotube electrodes. The proposed electrode can be considered as a commercial electrode to as an alternative to ITO electrode.     

Phase-controlled synthesis of thermally stable nitrogen-doped carbon supported iron catalysts for highly efficient Fischer-Tropsch synthesis

Nano Research - Iron-based nanoparticles with uniform and high particle dispersion, which are supported on carbon structures, have been used for various applications. However, their preparation...     

Stress-state dependence of cavitation and flow behavior in superplastic aluminum alloys

A detailed and quantitative investigation of the stress-state dependence of superplastic cavitation in fine-grained aluminum alloys has been carried out to develop clear evidentiary support to build future models. Several stress states, such as uniaxial tension, plane-strain tension, plane-strain compression, shear, and equibiaxial tension have been examined. Tests were carried out to large strain in an interrupted manner under a constant effective strain rate ( _e ) in the range of 10⁻⁴ to 10⁻² s⁻¹. Measurements of volume fraction, population density, and size distribution of cavities, made by image analysis via optical microscopy, show continuous emergence of new cavities as well as growth of cavities during superplastic straining. The total cavity volume fraction (V) increases exponentially with strain. The cavity growth rate, represented by η (equal to d ln V/dε _e ), as well as the cavity population evolution rate with strain (dN _c /dε _e , where N _c is the cavity number/unit area) are found to increase with normalized mean hydrostatic tensile stress (σ _m / σ _e ). An empirical equation for the biaxial forming limit in terms of the principal surface strains (ε ₁ and ε ₂) has been defined for a fixed cavity volume, as given by ε ₁=a V ^b − α ε ₂, where a and b are constants determined from ε ₁ values for plane strain (ε ₂=0). The value of b is found to be 0.2 to 0.3, and α is 0.4 to 1.0.     

An approach to feature‐based software construction for enhancing maintainability

While the way we build software affects significantly its maintenance in terms of the effort and cost, the experience level of the maintainer in a software acquirers' organization is also one of concern. In this context, often the maintainer is the user of the system. Unfortunately, it is quite possible to lose the trustworthiness of the software due to the inexperience of the maintainer, especially when the maintainer is without the help of the original developers. One remedy for providing security against the effects of the maintainer's software modifications is to restrict the access to software parts (modules) relative to the experience level of the maintainers. For such a remedy to be successful, the software should be constructed in such a way that its parts under maintenance affect others as little as possible. We propose an approach to software construction aligning the dependencies among software parts in one direction so that they are allocated to maintainers based on their experience level. Our approach decomposes the software into parts based on functionality and orders the parts by essentiality, which indicates how difficult it is to change each part. Then, we align the dependencies in such a way that the less essential functionality is dependent on the more essential functionality. Consequently, any modification on less essential functionality does not affect the essential functionalities. To demonstrate the feasibility of our proposed approach, we applied it to a military application and found that the constructed software enables us to confine maintainers' activity within a limited working area, and thus the software is safer against maintainers' modification. Copyright © 2006 John Wiley & Sons, Ltd.     

The optimal determination of the space requirement and the number of transfer cranes for import containers

It is discussed how to determine the optimal amount of storage space and the optimal number of transfer cranes for import containers. A cost model is developed for the decision making. It includes the space cost, the fixed cost of transfer cranes which corresponds to the investment cost, the variable cost of transfer cranes and outside trucks which is related to the time spent for the transfer of containers. A simple solution procedure for the optimal solution is provided. The solution procedure is illustrated using a numerical example.     

Optimization of silicon solar cell fabrication based on neural network and genetic programming modeling

This study describes techniques for the cascade modeling and the optimization that are required to conduct the simulator-based process optimization of solar cell fabrication. Two modeling approaches, neural networks and genetic programming, are employed to model the crucial relation for the consecutively connected two processes in solar cell fabrication. One model (Model 1) is used to map the five inputs (time, amount of nitrogen and DI water in surface texturing and temperature and time in emitter diffusion) to the two outputs (reflectance and sheet resistance) of the first process. The other model (Model 2) is used to connect the two inputs (reflectance and sheet resistance) to the one output (efficiency) of the second process. After modeling of the two processes, genetic algorithms and particle swarm optimization were applied to search for the optimal recipe. In the first optimization stage, we searched for the optimal reflectance and sheet resistance that can provide the best efficiency in the fabrication process. The optimized reflectance and sheet resistance found by the particle swarm optimization were better than those found by the genetic algorithm. In the second optimization stage, the five input parameters were searched by using the reflectance and sheet resistance values obtained in the first stage. The found five variables such as the texturing time, amount of nitrogen, DI water, diffusion time, and temperature are used as a recipe for the solar cell fabrication. The amount of nitrogen, DI water, and diffusion time in the optimized recipes showed considerable differences according to the modeling approaches. More importantly, repeated applications of particle swarm optimization yielded process conditions with smaller variations, implying greater consistency in recipe generation.