Estimation of anisotropic properties of nano-structured arrays by modal vibration control at microscale

Nano-structured arrays are engineered to meet the requirements of a variety of applications such as microfilters, sensors, and structural interface due to their unique mechanical characteristics, which cannot be achieved by conventional solid materials. However, it is hard to evaluate the elastic properties of nano-structured arrays owing to the discrete structure, sample size, and availability of suitable techniques. To facilitate this, we develop an advanced three-dimensional microscale vibration testing process. In the test, a specially designed three-dimensional microspecimen with tuned mass is excited by a piezoelectric actuator, and the resonance frequencies are detected by a laser device successfully. The anisotropic elastic moduli of nano-structured array composed of helical nano-springs are identified from a single spectrum. This array shows so strong characteristic anisotropy that the solid one hardly can attain. The microscale testing technique can be extended to other materials and microstructures.     

Strength of spline joints assembled by forming

In this paper, a new assembling method of spline joints that enables tight fitting in a simple manner by allowing slight plastic deformation at the spline teeth was introduced. Experiments were carried out for the spline joints of medium carbon steel varying the overlap zone between the male and the female spline teeth. Axial joining strength was increased with increase in the overlap length due to the residual compressive stress by forming. The joint by the proposed method also showed higher torsional strength than the conventional joint. Improvement in the torsional strength was explained based on the deformation and hardness distribution around the spline teeth. With respect to the shape of overlap zone, better results were obtained when using the specimen having a uniform overlap length along the axial direction.     

A review on the renewable energy development in Algeria: Current perspective,energy scenario and sustainability issues

The quality of life and safeness of the present and future generations are strongly intertwined with the availability of energy sources and the sustainability of the energy infrastructure. Energy consumption in developed countries grows at a rate of approximately 1% per year, and that of developing countries, 5% per year (Muneer et al., 2005 [1]). Present reserves of oil and natural gas can only cover consumption at this rate for the next 50 years in the case of oil, and for the next 70 years in the case of natural gas. Therefore, one of the fundamental priorities for a country such as Algeria is to use several renewable energies (RE) sources and environmentally friendly energy conversion technologies. Algeria is endowed with large reserves of energy sources, mainly hydrocarbons and a considerable potential for the utilisation of RE sources especially with respect to solar energy. Algeria has the potential to be one of the major contributors in solar energy and become a role model to other countries in the world. RE are now one of the major elements of Algeria's energy policy and in view of boosting the national effort in terms of RE beyond 2011, Algeria has developed a national programme for the period 2011–2030 to promote concrete actions in the fields of energy efficiency and RE in line with the approach adopted by the government on February 3, 2011. Besides, it confirms Algerian's ambition to become an international hub for industrial and energy production and exportation in the solar sector. With this in mind, along with the environmental responsibility issues, public awareness gradually increased over the last seven years and alternative energy resources have become a new area of interest. As a tangible target, the Ministry of Energy and Mines (MEM) strategic plan aims to reach a 40% share of RE (mainly solar) in electric energy production by 2030. The various future projects are all factors that will undoubtedly give Algeria an important role in the implementation of RE technology in North Africa, the capacity for providing sustainable supply of cost-effective electricity from RE sources for the needs of the population, and the possibility of even exporting 10,000 MW to neighbouring and European market. This paper provides a detailed analysis of the existing renewable energy sector and a forecast for demand growth, additional capacity, investment requirements and Algeria's ambitious objectives of use of RE and environment protection. The paper also discusses the current energy scenario and explores the alternative energy like solar and wind to ensure energy security supply, reliability, greater efficiency in energy conversion, transmission and utilisation. Particular attention is paid to Algeria's global and sustainable solutions of the environmental challenges and the problems of conservation of fossil energy resources under the clean development mechanism (CDM) structure. The report also provides a detailed analysis of the existing renewable energy sector and a forecast for demand growth, additional capacity, and investment requirements     

A control law for vehicle merging inspired by dragonfly behavior

Autonomous control of vehicles has recently attracted considerable attention. In this sense, vehicle merging has become an important topic in this field of research. However, in conventional studies, the controlled vehicle must calculate the movement of other surrounding vehicles to complete the merge, requiring high computational costs. In this paper, we focus on dragonfly behavior to solve this issue. Indeed, insects can behave adaptively in the complex real world in spite of the limited size of their brains. They reduce the computational requirements of their brain by relying on different properties of their surroundings, basing their intelligent behaviors on simple strategies. The behavior of a dragonfly when chasing a prey is an example of these strategies. In this study, we address the vehicle merging maneuver by applying dragonfly’s strategies to control the movement of the merging vehicle. We propose a simple control method inspired by the aforementioned strategies and, finally, we present simulation results that were conducted to demonstrate the effectiveness of this method.     

Effect of friction stir processing on microstructure of laser clad cobalt-based alloy

(The microstructural refinement of cobalt-based alloy (Stellite No. 6) by laser cladding and friction stir processing (FSP) was studied. A nanometer-sized microstructure consisting of fine carbide (particle size: 100–200 nm) and a grain (grain size: 150–250 nm) was successfully fabricated by the FSP on the laser clad cobalt-based alloy. The nanostructured cobalt-based alloy (Stellite No. 6) had an extremely high hardness of about 750 HV.     

Nickel‐Catalyzed Suzuki–Miyaura Coupling of a Tertiary Iodocyclopropane with Wide Boronic Acid Substrate Scope: Coupling Reaction Outcome Depends on Radical Species Stability

We describe a nickel‐catalyzed Suzuki–Miyaura arylation of a tertiary iodocyclopropane with arylboronic acids; this is an efficient and convergent strategy for providing various enantioenriched arylcyclopropanes with a quaternary stereogenic center. This is the first metal‐catalyzed coupling between a tertiary alkyl electrophile and a wide range of aromatics, including heteroaromatics. We found that the outcome of the Ni‐catalyzed coupling with halides as electrophiles was dependent on the stability of the radical species formed during the reaction. The use of tert‐butyl alcohol (t‐BuOH) as the reaction solvent was very effective, because of its stability under the radical‐generating reaction conditions.

     

Spray-dry synthesis of β-Cu1.8Zn0.2V2O7 ceramic fine particles showing giant negative thermal expansion

We used spray-dry method to synthesize fine powder of β-Cu_1.8Zn_0.2V₂O₇ showing large negative thermal expansion (NTE) linearly to temperature over a wide temperature range. The NTE of β-Cu_1.8Zn_0.2V₂O₇ is produced by microstructures consisting of voids and anisotropic thermal deformation of crystal grains in ceramics. By reducing the size of the microstructures that produce NTE, large NTE equivalent to that of bulk was realized, even for ceramic particles of about 2 μm size. Comparison with particles produced using a conventional method demonstrates that the particle size distribution is narrow and that the particles are nearly spherical. This achievement is expected to pave the way to use of NTE materials in micrometer-scale control of thermal expansion.     

Friction coefficients in cold forging: A global perspective

Worldwide, at least twenty different tribological tests have been proposed for the empirical determination of friction coefficients in cold forging processes. Due to the varying test setups, means of measurement, and level of abstraction, the comparability of the outcomes is, however, disputable. Within this work, six established test principles are compared using identical tribological systems. Large differences between the empirically determined friction coefficients are observed but can be explained under consideration of the respective tribological loads. Additional investigations of an extrusion process reveal that friction models also have to take into account the varying local thickness of the lubricant film.     

A feasible core design of lead bismuth eutectic cooled CANDLE fast reactor

Among the innovative reactor concepts, CANDLE has several advantages over conventional reactor designs. However, when CANDLE is extended to long life, the clad integrity at high neutron fluence, the build-up of fission product gases, and the pressure drop for long cores pose technological challenges which have to be overcome. In this paper, we propose practically viable design procedures, such as recladding the entire fuel pins and replacement of different amounts of fuel at different radial positions, to ensure clad integrity and flat power distribution, respectively. We demonstrate the efficacy of such design procedures by calculations that are performed on a LBE CANDLE reactor. Our calculations show that for a reactor operation period of 3700 days the various reactor parameters are within the limits proposed by Japan Atomic Energy Agency (JAEA).     

Development of localization system using ultrasonic sensor for an underwater robot to survey narrow environment

This paper describes a localization system for a swimming robot to survey underwater narrow environments. In that environment, external sensors cannot be set up to localize the robot position, as there are many structures and the robot moves three-dimensionally. Therefore, the position needs to be calculated only by internal sensors. In this work, a new localization method based on map-matching is proposed, referring to cross-sectional shape data cut from a three-dimensional computer-aided design (CAD) data as an environmental map and structural shapes measured by a range sensor. As a range sensor, an ultrasonic sensor which is two-dimensional scanning-type was developed. The reflected signals of the ultrasonic sensor have some noise. Only structural shape data are extracted from the reflected signals. The image correlation is used as the matching method. Experiments to evaluate the performance of the proposed system were implemented at a mock-up environment. As a result, it was confirmed that the position was detected with an accuracy of 100 mm. The error is mainly caused by measurement error of the ultrasonic sensor that is used to calculate structural shapes. We concluded to improve the measurement accuracy of the ultrasonic sensor to reduce localization error.