Dynamic range of coherent analog fiber-optic links

We investigate the performance of coherent analog optical links employing amplitude modulation (AM), phase modulation (PM), and frequency modulation (FM). The performance of these coherent links is compared to that of AM direct-detection (DD) links. The signal-to-noise ratios, nonlinearities, and-spurious-free dynamic ranges (SFDR's) of the foregoing links are evaluated. We calculate the SFDR for links using DFB and Nd:YAG lasers with typical linewidths of 10 MHz and 5 kHz, respectively. The performance of PM and FM links is dominated by phase noise above a critical value of received optical power. For a linewidth of 10 MHz, and SFDR's of PM and FM links are 30 and 31 dB, respectively, for a received optical power above -27 dBm in a 1 GHz bandwidth. For a linewidth of 5 kHz, the corresponding SFDR's above a received power level of 0 dBm are 51 and 53 dB. The performance of DD and AM links is dominated by RIN above a critical value of received optical power. For a RIN level of -155 dB/Hz, the SFDR's of DD and AM links are 49 and 47 dB, respectively, for a received optical power of 10 dBm in a 1 GHz bandwidth. The SFDR's of the DD and coherent links used for transmission of subcarrier-multiplexed (SCM) signals are also derived. We evaluate target laser parameters needed by a number of different applications. For AM video and antenna remoting applications, linewidths of <1 and <3 kHz are required to use PM and FM links, respectively. For FM video, linewidths of <150 and <350 MHz are required to use PM and FM links. For SCM digital applications, linewidths of <80 and <200 MHz are required to use PM and FM links. The paper concludes with a discussion of system implementation issues, including linearization, optical frequency modulation, balanced receivers, and IF issues     

Strength distribution of particles under compression

From time immemorial people dealt with size reduction processes (mill, mineral liberation, etc.). As time has passed industrial units for comminution processes have become larger and more sophisticated, but still they perform with low efficiencies [1], [2] and [3]. The strength of a particle is one of its most crucial characteristics due to the mechanical stresses experienced by each particle within an industrial unit. This is because the final size of particles is mostly dependant on the strength distribution of the raw material [4]. In this present study, the ability of a number of statistical formulations to accurately describe the strength distribution of particles was examined. Additionally, selected equations were analyzed and a general expression including the effect of the material and particle size was developed. A number of approaches to define particle strength were considered, and strength in terms of crushing force was chosen. Particle strength in terms of force and in terms of energy was also compared and found to be size independent. Finally, particle strength in terms of stress was examined and compared to the particle strength in terms of force.The ability to describe the compression strength distribution will significantly improve the accuracy of the comminution processes simulation, design and optimization.     

Kinetic parameter estimation for cooling crystallization process based on cell average technique and automatic differentiation

In this paper, a cell average technique(CAT) based parameter estimation method is proposed for cooling crystallization involved with particle growth, aggregation and breakage, by establishing a more efficient and accurate solution in terms of the automatic differentiation(AD) algorithm. To overcome the deficiency of CAT that demands high computation cost for implementation, a set of ordinary differential equations(ODEs) entailed from CAT based discretized population balance equation(PBE) are solved by using the AD based high-order Taylor expansion. Moreover, an AD based trust-region reflective(TRR) algorithm and another interior-point(IP) algorithm are established for estimating the kinetic parameters associated with particle growth, aggregation and breakage. As a result, the estimation accuracy can be further improved while the computation cost can be significantly reduced, compared to the existing algorithms. Benchmark examples from the literature are used to illustrate the accuracy and efficiency of the AD-based CAT, TRR and IP algorithms in comparison with the existing algorithms. Moreover, seeded batch cooling crystallization experiments of β form L-glutamic acid are performed to validate the proposed method.     

Interfacial tension measurement between immiscible polymers: improved deformed drop retraction method

This paper describes an improvement of the technique to measure interfacial tension in immiscible polymer blends. Our method is based on the droplet retraction method, in which one relates the kinetics of relaxation of a deformed droplet to the interfacial tension between the matrix and droplet. Previously, the problem with this technique has been the difficulty in preparing axisymmetric ellipsoidal droplets. In our work, we demonstrate that perfect axisymmetric ellipsoidal droplets are produced at a later stage of relaxation of short imbedded fibers. With this technique, we utilize the strengths of both the deformed droplet method and the imbedded fiber retraction method while overcoming their shortcomings. The interfacial tension value thus obtained was compared to that by conventional methods. Additionally, the effect of confinement by external walls on the interfacial tension measurement was studied. Confinement affects interfacial tension measurement when the gap between the walls is less than two times the equilibrium drop size.     

A new method to implement comminution functions into DEM simulation of a size reduction system due to particle-wall collisions

The ability to design a size reduction system prior to full scale experiments and to optimize existing systems has long been a goal of designers. Such a design and optimization could be achieved by correctly simulating any system under any operating condition. In this paper we present a new and innovative procedure to implement empirical comminution functions into DEM–CFD simulations. The paper is focused on the implementation procedures and not the DEM/CFD simulations, which deserve full attention. Therefore, this paper is not aimed to study any specific mill. The comminution functions include: initial strength distribution, selection function, breakage function and fatigue function. First, the traditional comminution functions (strength distribution, selection and breakage functions) and the recently investigated fatigue function are briefly described and modified. Then a procedure for implementing the functions into a DEM–CFD model or any other source to provide impact velocities and number of impacts, is described in detail. The implementation involves converting the probability comminution functions into individual particle properties by a random method and then converting the velocity dependent comminution functions into strength dependent ones. In this way, and mainly owing to the use of the fatigue function (which defines the weakening of those particles that are not breaking), a real size reduction system, in which each particle is subjected to multiple impacts at various velocities can be simulated. Three case studies for multiple impact conditions at the same average velocity (several impacts at the same velocity, various velocities at each impact and randomly selected velocities) are presented and analyzed in order to confirm qualitatively the procedure, although the comminution functions need to be further quantitatively modified. It should be emphasized that although the new procedure presents a step towards the final goal, some limitations do exist and some questions remain open.     

Simulation model of general human and humanoid motion

In the last decade we have witnessed a rapid growth of Humanoid Robotics, which has already constituted an autonomous research field. Humanoid robots (or simply humanoids) are expected in all situations of humans’ everyday life, “living” and cooperating with us. They will work in services, in homes, and hospitals, and they are even expected to get involved in sports. Hence, they will have to be capable of doing diverse kinds of tasks. This forces the researchers to develop an appropriate mathematical model to support simulation, design, and control of these systems. Another important fact is that today’s, and especially tomorrow’s, humanoid robots will be more and more humanlike in their shape and behavior. A dynamic model developed for an advanced humanoid robot may become a very useful tool for the dynamic analysis of human motion in different tasks (walking, running and jumping, manipulation, various sports, etc.). So, we derive a general model and talk about a human-and-humanoid simulation system. The basic idea is to start from a human/humanoid considered as a free spatial system (“flier”). Particular problems (walking, jumping, etc.) are then considered as different contact tasks – interaction between the flier and various objects (being either single bodies or separate dynamic systems).