Estimating muscle fatigue of the biceps brachii using high to low band ratio in EMG during isotonic exercise

The principal objective of this study was to estimate biceps brachii muscle fatigue using the fatiguing time (FT) and the initial slope (S_init) of the high to low frequency band ratio (H/LFB) in EMG during isotonic exercise until the endurance time (ET) at which the subject could no longer follow the fixed speed. Surface EMG was measured on the biceps brachii muscle of ten subjects (5 males and 5 females) as the subject performed repetitive elbow contraction tasks. The first task was with no load (“no load” task). The other tasks were performed until exhaustion (“load” task) with a load weighted at 10%, 20% and 30% of the subject’s maximum voluntary contraction (MVC). We extracted decreasing parameters of the EMG, such as median frequency (MDF) and three types of H/LFB (H1; 95∼500Hz, H2; 150∼350Hz, H3; 470∼500Hz and LFB; 15∼45Hz). Statistical analysis was conducted to select an appropriate parameter. The FT was defined as the time at which the selected H/LFB became smaller than the threshold (50% at 10% MVC, 60% at 20% MVC, and 65% at 30% MVC) with respect to the initial value, and S_init was defined as the slope of the linear regression line using H/LFB from the onset of exercise to FT. In order to predict ET, we proposed using an analytical method that employed a multiple linear regression model with two independent variables, FT and S_init. The results from this novel model were compared with those of previously established methods. In the “no load” task, there was no FT in the MDF and three H/LFBs. In the “load” task, the MDF and three H/LFBs gradually decreased, but the H3/LFB decreased most rapidly. A significant difference between the “no load” task and the “load” task at a 95% significant level was only observed in H3/LFB. ETs of all subjects were predicted at an error of approximately 30.4%. This error was better than that obtained using other methods (34.8% by Mathiassen’s method, 39.7% by Ma?setti’s method). FT detected from H3/LFB was a useful indicator to distinguish the EMG in the “load” task from that observed in the “no load” task, and the ET of a subject could be predicted using FT and S_init. Therefore, the H3/LFB provides more information on muscle fatigue than the other features under isotonic conditions, and may be suited to specific experimental protocols in workplace fatigue studies.     

A method of controllable pulse-heating for investigation of properties of short-lived liquids

A method of controlled pulse heating of low-inertia thermal probe immersed into the liquid under study with a temperatureT ₀ is described. The control system provides a “temperature plateau”-type heating mode, which consists in a rapid (t ₁∼10 μs) increase in the mass-average probe temperature to a chosen valueT _pl ≫T ₀ and maintains this value for a certain time interval (t ₂∼10³–10² μs) to within 1 K. Thermal effusivity of the substance, in relative units, is determined from the value of its internal heat flux. Sensitivity to changes in the thermal effusivity of a reference substance was 10⁻⁴. Due to the short pulse length and fine tuning of theT _pl value, the method allows one to conduct step-by-step scanning of “instantaneous” thermal properties of a substance in the region of its short-lived states.     

A multi-element thermal imaging system based on an uncooled bolometric array

A thermal imaging system based on a commercial uncooled microbolometric array of 384 × 288 elements has been developed and produced. The temperature and spatial resolutions of the system are <0.08°C and 0.96 mrad, respectively. The system has been designed to monitor the technical state of thermal power industry objects. Owing to the “open architecture” and the modular structure of the hardware and software, the system can be adapted for any thermal diagnostic task.     

Effect of boundary layer swirl on supersonic jet instabilities and thrust

This paper reports the effects of nozzle exit boundary layer swirl on the instability modes of underexpanded supersonic jets emerging from plane rectangular nozzles. The effects of boundary layer swirl at the nozzle exit on thrust and mixing of supersonic rectangular jets are also considered. The previous study was performed with a 30° boundary layer swirl (S=0.41) in a plane rectangular nozzle exit. At this study, a 45° boundary layer swirl (S=1.0) is applied in a plane rectangular nozzle exit. A three-dimensional unsteady compressible Reynolds-Averaged Navier-Stokes code with Baldwin-Lomax and Chien’sk-ε two-equation turbulence models was used for numerical simulation. A shock adaptive grid system was applied to enhance shock resolution. The nozzle aspect ratio used in this study was 5.0, and the fully-expanded jet Mach number was 1.526. The “flapping” and “pumping” oscillations were observed in the jet’s small dimension at frequencies of about 3,900Hz and 7,800Hz, respectively. In the jefs large dimension, “spanwise” oscillations at the same frequency as the small dimension’s “flapping“ oscillations were captured. As reported before with a 30° nozzle exit boundary layer swirl, the induction of 45° swirl to the nozzle exit boundary layer also strongly enhances jet mixing with the reduction of thrust by 10%.     

Thermal-Induced Wear Mechanisms of Sheet Nacre in Dry Friction

Sheet nacre is a natural biocomposite with a multiscale structure including a mineral phase of calcium carbonate (97 wt.%) and two organic matrices (3 wt.%). The mineral phase is constituted by an arrangement of CaCO₃ biocrystal nanograins (ca 40 nm in size) drowned in an “intracrystalline” organic matrix (4 nm thick) in order to form a microsized flat organomineral aragonite platelet. These platelets are themselves surrounded by an “intercrystalline” organic matrix (40 nm thick) building up a very tough materials. This microarchitecture referred to as “bricks and mortar” nacre structure, is mainly studied for the creation of new organic/inorganic hybrid materials. Currently, only little is known about the nacre mechanical behaviour under dynamical loading and more particularly under tribological conditions which involve shocks and thermal effects simultaneously. This paper brings out the thermal-induced damage mechanisms effect on the wear of sheet nacre by the assessment of the thermal component of the friction with a scanning thermal microscope. Results reveal that the mean contact pressure is the main driving force involved in the degradation of the organic constituents. For the lowest mean contact pressure (<0.4 MPa), wear is rather weak because the friction-induced thermal component is not sufficient for degrading the organic matrices. In contrast, beyond 0.4 MPa, the friction-induced contact temperature rises up over the melting point of the organic matrices, and may even reach the temperature of the aragonite–calcite phase transformation increasing dramatically the wear of sheet nacre.     

Measuring the extraction time of negative ions from the ionization chamber of a static mass spectrometer

A technique for measuring the time of extraction of negative ions from the ionization chamber of the ion source of an MИ-1201“B” static mass spectrometer is described. The time of extraction of SF₆ negative molecular ions equal to ∼(8.5 ± 1.0) μs is comparable to the ion time of flight in the tube of the analyzer.     

A Further Discussion on Trends in the Development of Advanced Manufacturing Technology

This paper is a supplement to “Trends in the Development of Advanced Manufacturing Technology” (Yang and Wu in Chin. J. Mech. Eng., 39: 73, 2003) but delves deeper into it. It first points out the strategic status of manufacturing industry in state development. Then, a detailed analysis is given on the features and trends in the development of advanced manufacturing technology in a total of 12 points from three aspects: “precision,” “extreme,” and “culture” from the aspect of the product itself; “green,” “rapidness,” “saving,” and “efficiency” during the manufacturing process; and “digit,” “auto,” “integration,” “networking,” and “intelligence” in view of the manufacturing method. In addition, it emphasizes that all the above aspects should be based on two base points: “manufacture” and “machinery.” Finally, it puts forth the guiding ideologies for the development of advanced manufacturing technology and the aspects China should give priority to in development, while stressing on the principles of independence, innovation and “human orientation.”     

Planar optical waveguide temperature sensor based on etched bragg gratings considering nonlinear thermo-optic effect

This paper demonstrates the development of optical temperature sensor based on the etched silica-based planar waveguide Bragg grating. Topics include design and fabrication of the etched planar waveguide Bragg grating optical temperature sensor. The typical bandwidth and reflectivity of the surface etched grating has been ∼0.2 nm and ∼9 %, respectively, at a wavelength of ∼1552 nm. The temperature-induced wavelength change is found to be slightly non-linear over ∼200 °C temperature range. Typically, the temperature-induced fractional Bragg wavelength shift measured in this experiment is 0.0132 nm/°C with linear curve fit. Theoretical models with nonlinear temperature effect for the grating response based on waveguide and plate deformation theories agree with experiments to within acceptable tolerance.     

Installation for air cleaning from organic impurities by plasma formed by barrier discharge of nanosecond duration

A prototype installation for air cleaning by plasma, which consists of a barrier-type discharge reactor and a high-voltage nanosecond-pulse supply generator, which is based on drift step recovery diodes, is considered. A stable corona-type barrier discharge was obtained at a 3-kHz supply-pulse repetition frequency. The discharge remained nonlocalized even at a small gas-discharge gap (∼6 mm) due to a short (∼25 ns) pulse duration, which allows a quite uniform effect on the air flow. The high rise rate (∼6 kV/ns) of the applied supply voltage pulses determines the high voltage amplitude (∼25 kV) at the reactor at the breakdown moment and allows maintenance of high electric-field intensity and a high intensity of plasma chemical processes. Thus, an electrical power lower than 8 W is required at the reactor input to produce 1 g of ozone per hour. The concentration of methylmercaptan in air during waste-water smell deodorizing at State Unitary Enterprise “Vodokanal of St. Petersburg” was reduced down to an allowable level of 0.5 mg/m³ at the electrical power consumption no higher than 0.25 W per cubic meter of air.     

Production monitoring—A proven productivity tool

Production executives in modern factories are concerned with standards, real production and schedule maintenance, and with having early foresight into problem areas. The use of digital computers in the factory has for many years been largely divided between “closed-loop control” and “data processing” (DP), but today there is a growing need for “closed-loop information control” (CLIC). This paper describes a system for implementation of this concept using exclusively industry-standard hardware, and its application within smaller industrial operations rather than the industrial giants (although their need may indeed be greater). For many such smaller companies, production monitoring may be a first venture into CIM. Rather than “control” or “data” being the key, “information” is the cornerstone of the system described. The word “information” conjures up a variety of ideas in its normal use, but a visit to a real factory forces a closer look at its meaning, if the CLIC concept is to be even worth considering. Repeatable and verifiable data sources are very difficult to obtain on the factory floor. Physical compatibility is a real concern, because equipment that operates in the usual controlled DP environment is not usually reliable on the factory floor. The operating conditions demanded by much to today's DP equipment preclude heat, vibration, electromagnetic interference and the generally hostile conditions which are prevalent in many factories. Consequently, any factory-floor system is fraught with unique problems all the way from data capture, through communications, into efficient data structures and meaningful graphic presentation. This paper describes such a system and summarises its effect on productivity as proven by application in several factories in the US and Canada.     

A “gentle” method for finishing Si3N4 balls for hybrid bearing applications

This paper is an overview of the work carried out in the finishing of Si₃N₄ balls for bearing applications using a novel process known as the magnetic float polishing (MFP). It is a “gentle” process in which very low levels of controlled force (∼ 0.5–2 N) is applied. The process can be divided into the following three stages: (1) an initial high material removal stage where the objective is to remove material as rapidly as possible with minimal damage to the surface, (2) an intermediate stage of semifinishing where size and sphericity are carefully monitored, and (3) final finishing stage where size, sphericity, and finish are closely controlled to meet the final requirements. The first process predominantly involves mechanical removal of material with harder and coarser abrasives, e.g., coarse B₄C; the second process involves the use of “less” harder and finer abrasives, e.g., medium to fine B₄C or SiC; and the third process involves the use of “much” softer abrasives, e.g., CeO₂, ZrO₂, and Cr₂O₃ that can chemo-mechanically react with the workmaterial (Si₃N₄) and/or the environment (air or water) to generate a smooth surface. Chemo-mechanical polishing of Si₃N₄ balls with CeO₂ abrasive yields an extremely smooth and damage-free surface with a surface finish R _aof 4 nm and an R _t of 40 nm and a sphericity of 0.15–0.25 μm. This revised version was published online in July 2006 with corrections to the Cover Date.     

Studies on the interactions between ZDOL perfluoropolyether lubricant and the carbon overcoat of rigid magnetic media

Current high performance magnetic storage devices, i.e., hard disk drives, typically operate at elevated temperatures of nominally 45–60°C. As a consequence, understanding the thermal response of the materials used in the construction of the drive becomes imperative. In this report, we focus on the thermal behavior of a common perfluoropolyether lubricant (ZDOL) used on the carbon-overcoated, hard disk. In particular, we show that evaporative loss of this disk lubricant, as well as bonding of the lubricant to the carbon-overcoated disk, can occur at the temperatures encountered in the hard-disk drive. Surface energy measurements show that the interaction of the hydroxyl-terminated perfluoropolyether ZDOL occurs principally through the end-groups. On unannealed disks, the interaction between this “mobile” lubricant and the carbon overcoat is characterized by hydrogen bonding with the strength of these interactions being only slightly stronger than the intermolecular hydrogen bonding characteristic of bulk ZDOL. Upon annealing at temperatures in the range of 60–150°C, the ZDOL lubricant becomes “bonded” to the disk. The surface energy of the bonded lubricant is substantially lower than the mobile lubricant reflecting the increased interaction strength that occurs as a result of bonding. Since the bonded state is the lower energy state, transitions from the mobile state to the bonded state are thermodynamically favored. The kinetics of this bonding transition, as well as the kinetics of lubricant evaporation were studied as a function of temperature. Using a model of two competing reaction channels, the activation energies for both lubricant bonding and lubricant evaporation were determined to be 3.6 kcal/mole and 5.4 kcal/mole respectively. Ab initio quantum chemical modelling was used to investigate possible interaction sites on the carbon surface. Both experiment and theory indicate that interaction of the hydroxyl-terminated ZDOL to the carbon overcoat occurs via hydrogen bonding to oxygenated species on the carbon overcoat, with a binding energy of 5–8 kcal/mole. An esterification reaction between the hydroxyl end-groups of ZDOL with carboxyl groups on the carbon surface as a result of annealing is shown to be consistent with the both the surface energy data and the kinetic data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Proposal of new eco-manufacturing feature interaction-based methodology in CAD phase

Following the environmental crises of recent decades, a turning point in the awareness of the fragility of ecosystems has been marked, i.e., environmental awareness. This has contributed to the development of various environmental laws and regulations such as the “Waste Electrical and Electronic Equipment,” the “Restriction of Hazardous Substances,” and the “Registration, Evaluation, Authorization and Restriction of Chemicals” regulations and the “Energy Using Products” Directives. Our work contributes to the development of eco-friendly product manufacturing processes. In order to estimate and optimize the environmental impacts of a product, most of the methodologies, concepts, and tools that integrate computer-aided design (CAD) and life cycle assessment systems generally exploit the feature technology at the level of each feature independently of the others, i.e., “microplanning.” The feature interaction technology (FIT) is treated only in few studies, but it is pivotal in the eco-manufacturing process. In this paper, we propose a new manufacturing-scenarios-based methodology by using FIT and a Multi-criteria Decision Support Method (MCDSM), which helps manufacturers maintain their marketplaces by producing goods in an eco-friendly way. In fact, this methodology helps designers choose from the CAD design phase the most ecological manufacturing process from possible existent scenarios in real time.     

A source of broad homogeneous beams of low-energy (∼0.5 keV) gas ions

A source of gas ions (argon, oxygen, nitrogen, etc.), the operating principle of which is based on the use of a glow discharge in an electrode system of a wide-aperture hollow cathode and anode in a magnetic field, is described. The exit aperture diameter of the hollow cathode, increased up to a size close to the ion beam diameter (10 cm), ensures the uniform ion emission of the plasma generated in the discharge region near the anode. A decreased angular divergence or increased ultimate ion-beam current density is achieved by a change in the potential drop in the space charge sheath between the plasma and the ion optics. The source generates broad (50 cm²) slightly diverging (ω/2∼3°–5°) ion beams with energies of 300–1000 eV at a beam current density of ∼0.5 mA/cm².     

Comparison of thermal fatigue behaviour of ASTM A 213 grade T-92 base and weld tubes

Super-heater tubes are subjected to alternate heating and cooling in power plants causing them to crack and eventually fail. This phenomenon is referred to as “thermal fatigue.” In this paper, a laboratory simulation for reproducing the thermal fatigue phenomenon is developed to determine the number of cycles necessary before failure occurs in super-heater tubes. The temperature and strain distributions along the specimen were computed theoretically using ANSYS software for the applied temperature condition. The thermal fatigue test was conducted for both base and shielded metal arc (SMA) welded tubes separately and both passed in the non-destructive tests. These tubes were subjected to thermal cycles from 800°C (accelerated temperature) to room temperature. Oxy-acetylene heating setup was utilized as a heating source, and a water bath was utilized for quenching purposes. The tests were carried out until open cracks were identified. Surface cracks were identified in the base and weld tubes after 90 and 60 cycles respectively. This study reveals that heating and cooling cause thermal fatigue, initiate cracks in the tubes.     

Novel piezoelectric pump with &#8220;E&#8221;-shaped valve found from sub-experiments

Increasing the driving frequency of a piezoelectric vibrator can resolve the bottleneck of low flow in a valve piezoelectric pump. However, a piezoelectric pump of a traditional valve body presents the hysteretic nature of the valve, and macroscopic performance is up-frequency to flow-sharply. This research is to settle the bottleneck mentioned above. First, through the sub-experiment on various parameters of the plate valve of a piezoelectric pump, the reasons why a valve body itself can influence “up-frequency to flow-sharply”, which causes the hysteretic nature of the valve, were discovered. Second, an “E”-shaped valve and piezoelectric pump with an “E”-shaped valve (PPEV) were invented. Finally, the efficiency of PPEV has been proved helpful to reduce hysteretic nature in experiments. Under the similar conditions, compared with traditional pumps, the driving frequency of novel PPEV can be more than 10 times high, and the flow rate also can be several times high.     

Space Tribometers: Design for Exposed Experiments on Orbit

Eight pin-on-disk tribometers have been made for testing materials in space on board the International Space Station. They will be exposed directly to the low earth orbit (LEO) environment on board the “Materials on the International Space Station Experiments” platform where they will experience extreme conditions including atomic oxygen, ultrahigh vacuum, radiation (including UV radiation), and thermal ranges from −40 to 60 °C. In order to survive launch and LEO, these tribometers were designed to be extremely compact, rugged, and reliable. Pin-on-disk tribology experiments are now being performed with a 13.2 mm/s sliding velocity (14 RPM at 9 mm wear track radius) and a 1 N normal load with hemispherical pin of 1.5875 mm radius. Materials tested include MoS₂/Sb₂O₃/Au, MoS₂/Sb₂O₃/C, YSZ/Au/MoS₂/DLC, and SiO-doped DLC coatings, and bulk samples of polytetrafluoroethylene (PTFE) alumina nanocomposites and gold.     

Manufacturing cell formation using modified ART1 networks

The primary objective of group technology (GT) is to enhance the productivity in the batch manufacturing environment. The GT cell formation problem is solved using modified binary adaptive resonance theory networks known as ART1. The input to the modified ART1 is a machine-part incidence matrix comprised of the binary digits “0” and “1”. And the outputs are the list of part families and the corresponding part list, machine cells and their corresponding list of machines, and the number of exceptional elements. This method is applied to the known benchmarked problems found in the literature and it is found to outperform other algorithms in terms of minimizing the number of the exceptional elements. The relative merits of using this method with respect to other known algorithms/heuristics in terms of computational speed and consistency are presented .     

Fast algorithm of detection of boundary points in images

A method of detecting boundary points in brightness images, based on subpixel calculation of the brightness difference, is proposed. In a fragment 4×4 pixels in size, this method allows calculating 12 directions of the jump in brightness; the algorithm complexity is ∼34N atomic operations. The method considered is compared with available methods of detection of boundary points in the image. The algorithm proposed is demonstrated to be more stable to the “salt and pepper” noise, ensures more stable determination of the brightness jump direction, and provides a more intense response to the signal. An application of the method is noted.     

An investigation into friction behaviour of dispersion-strengthened copper under severe railway braking conditions

A dispersion-strengthened copper (DSC) has been studied as an alternative material for railway brake discs, to be used in severe railway braking applications. Compared to standard steel, the DSC shows a more homogeneous thermal field at the friction surface. This also applies in depth, both avoiding hot spots. This thermal behaviour implies a lower wear and a very interesting friction coefficient evolution without any “anti-fade” phenomenon.