A finite element modeling-based approach to predict vibrations transmitted through different body segments of the operator within the workspace of a small tractor

Agricultural tractor drivers are subjected to high levels of whole-body vibrations and hand arm vibrations during most part of the farm activities due to unevenness of field surface, uneasy posture, improper workplace design, moving parts of the tractor, and other unavoidable circumstances. The comfort level of the operator inside a dynamic tractor is dependent on the level of vibration generated inside the different human body segments. In the present study, a finite element modeling was proposed to predict vertical vibrations (Z-axis) and frequencies at the different body segments of the seated small tractor operator. The forces required for different controls of the tractor were measured to be used as input parameters in the finite element modeling. The maximum mean forces of the brake (172.8 N) and clutch (153.2 N) were used as the input parameters for the simulation study. The simulated results were validated with the field measured values of vertical accelerations at selected body segments of the operator. The simulation could successfully predict vertical vibrations at selected points of interest (i.e., foot, leg, thigh, lower arm, upper arm, back, and head) except the chest of the body, as the buttock of the operator model was fixed (degree of freedom is equal to zero) in the simulation. The obtained results were compared with the international standards ISO 2631-1 (1985/1997) and ISO 5349-1 (2001) to assess the vibration characteristics at the different body segments of the operator. The foot, leg, lower arm, and upper arm of the operator were subjected to vertical vibration frequencies from 10 to 200 Hz. Most of the resonance of vertical accelerations occurred in one-third octave bands of 20–80 Hz frequencies. The thigh, chest, back, and head of the operator were exposed to vibration frequencies below 40 Hz during field operation. At these parts of the body, the vertical acceleration resonated at lower frequencies, between 2 and 8 Hz.     

User-Driven Frequency Scaling

We propose and evaluate user-driven frequency scaling (UDFS) for improved power management on processors that support dynamic voltage and frequency scaling (DVFS), e.g, those used in current laptop and desktop computers. UDFS dynamically adapts CPU frequency to the individual user and the workload through a simple user feedback mechanism, unlike currently-used DVFS methods which rely only on CPU utilization. Our UDFS algorithms dramatically reduce typical operating frequencies while maintaining performance at satisfactory levels for each user. We evaluated our techniques through user studies conducted on a Pentium M laptop running Windows applications. The UDFS scheme reduces measured system power by 22.1%, averaged across all our users and applications, compared to the Windows XP DVFS scheme     

Monte Carlo simulation of diffusive-to-ballistic transition in phonon transport

Heat conduction properties in Si nanostructures are analyzed using a Monte Carlo method developed for solving the phonon Boltzmann transport equation. The thermal resistances are evaluated for the systems with various sizes, and the transition from the diffusive to the ballistic heat conduction are investigated. We compare the two different phonon dispersion models (the realistic dispersion relation based on the adiabatic bond charge model and the analytically approximated model), and it is shown that the correct implementation of the phonon dispersion relation is essential to accurately simulate the quasi-ballistic heat conduction properties, which becomes obvious in the structures smaller than the phonon mean free path.     

Block copolymers combining semi-fluorinated poly(arylene ether) and sulfonated poly(arylene ether sulfone) segments for proton exchange membranes

A series of aromatic multiblock copolymers based on alternating segments of hydrophilic sulfonated polysulfone (PSU) and hydrophobic polyfluoroether (PFE) were prepared and characterized as proton exchange membranes. PSU precursor blocks were synthesized by polycondensation of dichlorodiphenylsulfone and resorcinol, and PFE precursor blocks were prepared by combining decafluorobiphenyl and isopropylidenediphenol. After preparation of the multiblock copolymers via a mild coupling reaction of the precursor blocks, the resorcinol units of the PSU blocks were selectively and almost completely sulfonated under mild reaction conditions using trimethylsilylchlorosulfonate. Transparent and robust membranes with different PSU-PFE copolymer compositions and ion-exchange capacities were cast from solution. Atomic force microscopy of the membranes revealed a distinct nanophase separated morphology. At 80 °C, the proton conductivity reached 10 mS cm⁻¹ under 65% relative humidity and 100 mS cm⁻¹ under fully hydrated conditions.     

Comparative studies on the nutritive and anti-nutritive properties of fruits in selected Berberis species of West Himalaya, India

Nutritional and anti-nutritional factors of five Berberis species, widely known for their wild edible fruits and medicinal properties, were investigated in the Indian west Himalaya. These fruits contained high content of fiber (pulp 7.0-8.1%; seeds 4.4-5.3%), protein (pulp 4.7-7.2%; seeds 5.9-8.5%) and fat (pulp 2.6-4.0%; seeds 4.6-5.3%) as compared to most of the known wild edibles in the region. They, however, contained reasonably lower food energy, largely due to low carbohydrate content. All the five species emerged as good source of minerals, especially Ca and K. The values of various nutrient and mineral elements varied significantly among species, which implies potential of different species can be harnessed for diverse attributes. The fruits, however, possessed anti-nutritional factors like tannins and phytic acid, which need to be tackled appropriately while considering these fruits for value addition as health food.     

Thermo-economic analysis of a direct supercritical CO2 electric power generation system using geothermal heat

A comprehensive thermo-economic model combining a geothermal heat mining system and a direct supercritical CO₂ turbine expansion electric power generation system was proposed in this paper. Assisted by this integrated model, thermo-economic and optimization analyses for the key design parameters of the whole system including the geothermal well pattern and operational conditions were performed to obtain a minimal levelized cost of electricity (LCOE). Specifically, in geothermal heat extraction simulation, an integrated wellbore-reservoir system model (T2Well/ECO2N) was used to generate a database for creating a fast, predictive, and compatible geothermal heat mining model by employing a response surface methodology. A parametric study was conducted to demonstrate the impact of turbine discharge pressure, injection and production well distance, CO₂ injection flowrate, CO₂ injection temperature, and monitored production well bottom pressure on LCOE, system thermal efficiency, and capital cost. It was found that for a 100 MW_e power plant, a minimal LCOE of $0.177/kWh was achieved for a 20-year steady operation without considering CO₂ sequestration credit. In addition, when CO₂ sequestration credit is $1.00/t, an LCOE breakeven point compared to a conventional geothermal power plant is achieved and a breakpoint for generating electric power generation at no cost was achieved for a sequestration credit of $2.05/t.     

A simple and efficient sun tracking mechanism using programmable logic controller

To increase the unit area illumination of solar ray on PV panel, it is required to track the sun throughout the day. So to reach the goal various type of sun tracking mechanism is already developed but in this paper we designed two different types of sun tracking mechanism: single axis and dual axis tracking using programmable logic controller (PLC) as it has numbers of unique advantages like??it is faster, reliable, requires less maintenance and reprogrammable. A comparative study between those two systems is also presented in this paper. The whole system has been designed and tested using GE, FANUC PLC.     

A design approach for myoelectric arm with hand and wrist motions using single actuator

This paper relates to the development of prosthetic myoelectric hand that performs many functions of real human hand like opening and closing of fingers and wrist rotation. This dual movement of prosthetic hand is controlled by a single DC motor. Below-elbow amputee persons with missing limbs can append this prosthetic hand with the available stump and can do some of the hand operations with multiple degrees of freedom by voluntary activation of muscles using electromyogram (EMG) electrodes. To rehabilitate such a person, facilities like opening, closing, grasping, and lifting objects of different weight with variable grip force are available like natural hand. The main design consideration includes degrees of freedom, number of actuators, power of actuators, reliability, electronic control, light weight, economic viability, wrist rotation, variable grip force pattern, and ease of attachment with limb. Use of electromagnetic clutches along with the coupling logic of DC motor and microcontroller based on grip force generation and wrist rotation based on EMG signals imparts a new function to the device. It will be useful for both robotic and prosthetic industry.     

Phase characterization and mechanical and flame‐retarding properties of nano‐CaSO4/polypropylene and nano‐Ca3(PO4)2/polypropylene composites

An in situ deposition approach was used for the synthesis of nano‐CaSO₄ and nano‐Ca₃(PO₄)₂. The nanosize particles were confirmed with an X‐ray diffraction technique. Composites of polypropylene (PP) with 0.1–0.5 wt % nano‐ or commercial CaSO₄ or nano‐Ca₃(PO₄)₂ were prepared. The transition from the α phase to the β phase was observed for 0.1–0.3 wt % nano‐CaSO₄/PP and nano‐Ca₃(PO₄)₂/PP composites. This was confirmed by Fourier transform infrared. A differential scanning calorimetry analysis was carried out to determine the thermal behavior of the nanocomposites with increasing amounts of the nano‐CaSO₄ and nano‐Ca₃(PO₄)₂ fillers. Increases in the tensile strength and Young's modulus were observed up to certain loading and were followed by a decrease in the tensile strength. A continuous decrease in the elongation at break (%) was also observed for commercial CaSO₄ and larger nano‐Ca₃(PO₄)₂. A decrease in the mechanical properties after a certain loading might have been due to the agglomeration and phase transition of PP in the composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 670–680, 2007     

Methacrylate/acrylate terminated derivatives of diglycidyl hexahydrophthalate: Synthesis,structural, and thermal characterization

Mono‐ or di(meth)acrylate‐terminated derivatives of diglycidyl hexahydrophthalate (ER) were prepared by reacting 1 : 1 or 1 : 2M ratio of ER and methacrylic acid or acrylic acid. These vinyl ester (VE) resins were characterized by determining epoxy equivalent weight, acid number, and molecular weight by gel permeation chromatography. Structural characterization was done by FTIR and ¹H NMR spectroscopy. In the ¹H NMR spectra of acrylate‐terminated VE resins, three proton resonance signals were observed in the region 5.8–6.4 ppm due to vinyl group while in methacrylate‐terminated VE resins only two proton resonance signals due to vinylidene protons were observed at 5.6–6.1 ppm. The Brookfield viscosity (room temperature (25 ± 2)°C) of these resins diluted with varying amounts of MMA was determined at 20 rpm. Curing behavior was monitored by determination of gel time and differential scanning calorimetry. An exothermic transition was observed in the DSC scans in the temperature range of (81–150)°C. Isothermal curing of MMA‐diluted VE resins containing AIBN as an initiator was done at 60°C for 2 h in N₂ atmosphere, and then heating for another 2 h in static air atmosphere. Thermal stability of isothermally cured resins in N₂ atmosphere was evaluated by thermogravimetric analysis. All cured resins decomposed above 310°C in single step. Thermal stability of the cured resins having acrylate end caps was marginally higher than the resins having methacrylate end groups. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006