Molecular mobility in bulk and in near-surface nano-layers of ultra-high-molecular-weight polyethylene

A comparative study of molecular dynamics in near-surface nanolayers and in a bulk of polyethylene is presented. Molecular mobility in near-surface nanolayers of polyethylene reactor powders and melt-crystallized films of various molecular weights prepared in different crystallization conditions were studied with the help of thermoluminescence technique using high frequency glow dicharge Ar plasma for surface activation. Molecular mobility in a bulk of the same samples was investigated by the method of radio thermoluminescence, in which a deeply penetrating γ-quanta from 60Co radiation was used for activation of the bulk. A marked difference in a temperature position of the peaks on the glow curves of plasma-induced thermoluminescence and those of radiothermoluminescence correspoding to γ- and ß-transitions was found to depend on crystallisation conditions and molecular weight. Quasi-independent segmental mobility (ß-relaxation) in the near-surface nano-layers of UHMWPE reactor powder particles synthesized at low temperatures appeared to be unexpectedly unfreezed at the temperature higher than that in the bulk. It was supposed that this happend because of crystallization under the confinement conditions during low-temperature polymerization leads to formation of a specific surface structure.

Automotive Grille Shutter Using Passive Shape Memory Alloy Actuation

Automotive grille shutters are used to reduce the aerodynamic drag of the vehicle when cooling requirements are low by blocking a portion of the airflow through the condenser, radiator, and fan module (CRFM); the lower aerodynamic drag improves fuel economy. A passively actuated SMA grille shutter was designed as a less complex and lower overall cost solution to current electro-mechanical designs. This paper presents the design and calibration process for the automotive grille shutter SMA actuator using passive temperature control. The initial design target opening and closing temperatures of the grille shutter system were determined by climatic wind tunnel and vehicle road tests measuring motor-driven grille shutter position versus CRFM exhaust temperature. The initial SMA actuator design almost met the temperature requirements; subsequent road testing confirmed the need to shift the start to close and fully closed temperatures at least 6 °C higher to meet specifications. The transformation temperatures of the SMA actuator were calibrated by varying stress on the SMA wires by means of the total cross-sectional area and biasing force. Tests were performed in an environmental chamber to characterize the temperature-position behavior during heating and cooling cycles, the best candidate improved the hysteresis band by 3 °C from the initial design. This study presents an industry need for the development of lower hysteresis SMA wires/springs for passive applications, which can maximize the benefit of SMA actuation by utilizing the temperature-stress-strain coupling behavior of SMA.

Структурные особенности фосфатов Ca-=SUB=-9-x-=/SUB=-M-=SUB=-x-=/SUB=-Dy(PO-=SUB=-4-=/SUB=-)-=SUB=-7-=/SUB=- (M=Zn-=SUP=-2+-=/SUP=-, Mg-=SUP=-2+-=/SUP=-)

Solid solutions of phosphate with whitlockite-type Ca9-xMxDy (PO4) 7 (M = Zn2 +, Mg2 +) were obtained. The samples were studied by a complex of methods, such as X-ray phase analysis, second harmonic generation, and luminescent spectroscopy. It was established that in the series of solid solutions a change in the symmetry of the unit cell R3c-> R 3c is observed during Ca2+ -M2+ substitution, and the concentration dependence was determined. The phase transitions of the ferroelectric and antiferroelectric type and their temperature position were established by dielectric spectroscopy. The synthesized samples demonstrate intense luminescence with 350 nm excitation and the resulting radiation is in the white region of color coordinates (CIE).

RESEARCH OF HUMAN FATIGUE AND MEASUREMENT PARAMETERS FOR WORKABILITY ASSESSMENT

Human fatigue is reduced working capability for certain period of time as the result of unusual or prolonged workload. Fatigue arises when the body’s energy requirements exceed its supply. Fatigue first manifests as reduced concentration capability causing movement coordination and precision disruption leading to decreasing workability. Fatigue is an object of research in physiology, psychology, work ergonomics, medicine, and biotechnology where each domain has a focus on mental fatigue. The functional state in the context of professional activity is defined as a complex of characteristics of functions and qualities that determine the fulfilment of labour activity. Furthermore, a comprehensive estimation of subject functional state in combination with other factors like subject self-assessment and objective performance tests (cognitive load tests) is a necessary input for the evaluation of workability and efficiency on task. The heterogeneous nature of fatigue as a systemic manifestation requires analysis of multiple key parameters which are relevant to the specific type. The current feasibility study focuses on human biological signal from electrical activity of heart, brain, muscles and skin potentials as well as temperature, position, and respiration to obtain diagnostic parameters reflecting the state of cardiovascular, muscles, and central nervous systems for physiological monitoring of vital signs. The fatigue physiological parameter and feature formalization aim to support the development of a platform with complex passive multi-level fatigue monitoring system and workability evaluation system designed in order to provide an integrated service.

Enhancing Photovoltaic solar panel Raising efficiency of photovoltaic solar panel by preventive actions

this document describes the main factors responsible for the reduction of the efficiency of photovoltaic (PV) solar panel. Those factors are: type of material used, accumulated dust on solar panel, higher temperature, position of the panel, and low area for photon capturing. To achieve higher efficiency, this paper investigated several ways to reduce the effects of the affecting parameters: reducing the temperature of the PV panel, eliminating the dust, controlling the position of the panel and adding a mirror to collect more photons. Those modifications were applied on a laboratory-scale prototype in order to enhance the performance of the (PV) to deliver higher efficiency.

Study on the Temperature of Workpiece in Low-Frequency Vibration Drilling

The cutting mechanism in different position on the cutting edge of flat drill is researched in low-frequency vibration drilling. Experiments are carried on to measure the temperature on the bottom and locate the highest temperature position. And also, the variation of temperature resulting from different amplitudes is analyzed. Experiment results show that low-frequency vibration drilling can reduce the highest temperature relative to normal drilling and temperature reduces by 37% with the 0.18mm amplitude.