Sharif Digital Repository

Developing ocean energy extraction, including ocean thermal energy conversion (OTEC), has been of interest to researchers for many decades. OTEC is a free fuel technology and could be used as a baseline power generation. These advantages plus the engineering challenge have resulted in researchers striving to design and construct prototype devices. Making use of worldwide experience, all sections of a conceptual design including site selection, technical specifications and cost estimation were carried out for an Iranian OTEC power plant. A 5 MW closed cycle floating plant with an annual average temperature difference of 22°C was chosen at a 33 km distance from Chabahar harbour. Deep seawater... 

Lead-acid battery is a storage technology that is widely used in photovoltaic (PV) systems. Battery charging and discharging profiles have a direct impact on the battery degradation and battery loss of life. This study presents a new 2-model iterative approach for explicit modelling of battery degradation in the optimal operation of PV systems. The proposed approach consists of two models: namely, economic model and degradation model which are solved iteratively to reach the optimal solution. The economic model is a linear programming optimisation problem that calculates the optimal hourly battery use profile based on an assumed value of the battery degradation cost. The degradation model,... 

Natural compounds containing polysaccharide ingredients have been employed as candidates for treatment of skin tissue. Herein, for the first time, electrospinning setup was proposed to fabricate an efficient composite nanofibrous structure of Beta vulgaris (obtained from Beet [Chenopodiaceae or Amaranthaceae]) belonged to polysaccharides and an elastic polymer named nylon 66 for skin tissue engineering. Both prepared scaffolds including noncomposite and composite types were studied by Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical assay, and contact angle. Scanning electron microscope examinations have approved the uniform and homogeneous... 

In recent years, the city of Tehran has frequently experienced severe air pollution episodes, and the increase in the use of vehicles has exacerbated this critical situation. It is unclear to what extent each vehicle category contributes to the production of pollution during a pollution event. For this purpose, a combination of the weather research and forecasting (WRF) and the Comprehensive Air Quality Model with Extensions (CAMx) modeling systems was used to simulate the distributions of pollutant concentrations over Tehran in a pollution episode from December 3 to 23, 2017. First, the performance of the modeling system was evaluated with respect to the simulation outputs against... 

In this study, indigenous cyanogenic bacterial strains were isolated on nutrient, minimal salt, and soil extract media at various culture conditions from two distinct landfills of e-waste, Iran. Based on their cyanide formation profiles, five most potent isolates were selected for optimization and to this end, the influence of the most effective factors on cyanide production including pH, glycine concentration and temperature were assessed using one-factor at a time method (OFAT). Initial pH of 7, glycine concentration of 2 g/L and temperature of 30°C were obtained as optimal conditions for most of the isolates. Additionally, two bioleaching processes were applied for each bacteria to detect... 

In under-constrained spatial cable suspended robots, maximum number of cables are equivalent to the number of degree of freedom, therefore the equations of kinetostatic have unique solutions and invention of positive cable tensile forces in these robots must come into being by redundant cables, springs or by Moving Platform (MP) weight. In this research, MP weight is considered to create tension in cables so both increasing workspace volume and decreasing possibility of cable encounter with together can be created because of using less cables. The range of MP weight to generate tension in cables is calculated by using Interval method, optimum weight is selected and then optimal tension... 

The objective of this paper is designing, modeling and wrench feasible workspace analysis of a 3D cable suspended robot as IRPM (Incompletely Restrained Positioning Mechanism). This type of robots supports a load platform in space by less than or equal to six spatially arranged cables. We use the model of 6 cables spanned in the same manner as a Stewart parallel mechanism. This mechanism is suitable for the accurate positioning of heavy loads. Concentrating on the operations of heavy loads handling, studying the workspace and ways of increasing it is of high importance. Several workspaces exist amongst which the constant and total orientation statically reachable combined and wrench feasible... 

This article proposes modelling, simulation and applied wrench workspace analysis of a 3D cable based robots which are consist of six cables are studies. After modelling, the kinds of workspace are defined then an available static combined workspace for different geometric structures of fixed and moving platform is obtained. This workspace is defined as the situations of reference point of the moving platform (center of mass) which under external forces such as weight and with ignorance of inertial effects, the end effector should be in static equilibrium under conditions that length of all cables must not be exceeded from the maximum value and all of cables must be at tension (they must... 

Employing of the composite electrospun scaffold containing herbal extract in conjugation with co-culturing of cells can open up new window to the design of efficient biomaterials for skin tissue regeneration. Here, we introduce the synergistic effect of composite electrospun nanofibrous scaffold of nylon66 loaded with Beta vulgaris (B. vulgaris) (extract of beet roots, a plants whose widely used in Iranian folk medicine as wound healing medicine) and co-culture of mesenchymal stem-cells (MSCs)-human keratinocyte (H-keratino) differentiation towards epithelial lineage. In vitro biocompatibility was examined through MTT assay and epithelial differentiation checked by real-time PCR and... 

Airborne hexavalent chromium is a known human respiratory carcinogen and allergen. Many workers are exposed to hexavalent chromium in various processes which chromium electroplating plants are the most common. In this study, the feasibility of a new control approach to remove this pollutant using chitosan beads as a biosorbent was investigated. Hexavalent chromium sorption was studied relative to pH, pollution concentration, sorbent concentration, temperature, and air velocity using one factor at a time approach and Taguchi experimental design. Polluted air with different chromium mist concentrations (10-5000 μg/m3) was contacted to chitosan beads (3.3-20 g/L), floating in distilled water... 

This paper examines the strategies of a local supplier of high technology capital goods (or complex product systems, CoPS) in a middle-income developing economy, Iran, in its efforts to acquire technology and catch up with market leaders. The study draws upon both the development and business strategy literatures to develop a novel conceptual framework of latecomer strategy which is then applied to the Iranian firm engaged in the design, production and implementation of electricity generation systems. Although exploratory, the study shows that the firm was able to exploit its linkages with local clients, favorable government policies and a growing domestic demand to overcome barriers to... 

Controlled graphitization has become known as a practical method for improvement of wear resistance and machining properties in steels. In this paper, the effect of heat treatment on microstructure of CK45 steel has been investigated. Austenitising was carried out at 920 °C for 5 h. Besides, isothermal transformation was conducted at 750 °C in the time range of 1-20 h. In this work, full potential carbon resource was tried to be used around samples as a factor to prevent the burning of the limited carbon in steel and also to increase the percentage of sample surface carbon in order to improve wear capability and machining. The microstructure of the steel considerably changes by this heat... 

Cobalt hydroxide modified glassy carbon electrodes (CHM/GC) prepared by the anodic deposition in presence of tartrate ions have been used for the electro-catalytic oxidation of methanol in alkaline solutions where the methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (IS) have been employed. In CV studies, in the presence of methanol the peak current of the oxidation of cobalt hydroxide increase is followed by a decrease in the corresponding cathodic current. This suggests that the oxidation of methanol is being catalysed through the mediated electron transfer across the cobalt hydroxide layer comprising of cobalt ions of various valence states. A... 

Blood vessels, especially large vessels have a greater thermal effect on freezing tissue during cryosurgery. Vascular networks act as heat sources in tissue, and cause failure in cryosurgery and reappearance of cancer. The aim of this study is to numerically simulate the effect of probe location and multiprobe on heat transfer distribution. Furthermore, the effect of nanoparticles injection is studied. It is shown that the small probes location near large blood vessels could help to reduce the necessary time for tissue freezing. Nanoparticles injection shows that the thermal effect of blood vessel in tissue is improved. Using Au, Ag and diamond nanoparticles have the most growth of ice ball... 

In this work, the effects of the surface-modified nanodiamond particles (NDs) on the barrier, rheological, mechanical and thermal properties of ethylene vinyl acetate (EVA) composites for the packaging applications were investigated. Fourier transform infrared spectroscopy, as well as thermal gravimetric analysis were employed to study the grafting of vinyltriethoxy silane (VTS) on the surface of NDs. Afterwards, EVA samples containing 0, 0.1, 0.5, 1, 1.5 and 2 wt% of surface-modified NDs were prepared by a two-stage process including the solution and injection processes. In order to evaluate the physicochemical, rheological, mechanical and thermal properties of the EVA/NDs samples, field...