Conventional High Speed Research Articles

Invited: Coatings for Robust Metal Bipolar Plates

Metal bipolar plates have advantages of lighter weight and smaller volume over graphite based bipolar plates for automobile fuel cell stacks. Stainless steel has been identified as the primary candidate of the substrate. It has reasonable corrosion resistant, high electrical and thermal conductivity, suitable mechanical properties and formability to form the proper flow field by conventional high speed stamping process. The most important, SS foil is widely commercially available and used in various markets, which result in its low cost comparing with other corrosion resistant alloys. Additional treatment on stainless steel is necessary for three reasons. First is to reduce the surface electrical contact resistance with gas diffusion layer. The second is to further improve the corrosion resistance of stainless steel in PEM fuel cell stack operation conditions, especially under the transient high voltage conditions. The third is to minimize the absorption of leached ions on the electrode catalyst that may poison electrodes.Two types of coatings have been investigated. One is the coating using precious metal, the other is precious metal free coating technologies. The advantages and progresses of each coating will be reviewed. TreadStone has been involved in corrosion resistant metal plate development for several years. A unique design of metal plate coating and its low cost fabrication technology have been developed. It has demonstrated stable long term (2,000 hours) operation for automobile fuel cell stacks under dynamic operation conditions. More development activites are on-going to further reduce the cost with the supports from US Department of Energy.

Moderately stable emulsions produced by a double syringe method

Different emulsification techniques lead to emulsions with different targeted properties specific to their intended use. In this study, emulsions are generated using several emulsification techniques. They are compared as regards the component droplet size distribution and their stability in time. A particular technique based on the “Tessari” (known as double syringe system – DSS, as well) method – used originally for foam generation – is evaluated for emulsion production. Results show that DSS method leads to emulsions with mean droplet size about two orders of magnitude larger than in the case of emulsions obtained by conventional high speed and high pressure homogenizers (HPH). However, DSS emulsions have comparable viscosity behavior with the emulsions obtained by conventional methods and are stable for time intervals of a couple of hours which is convenient for specific medical applications. Furthermore, this study evaluates the effect of small quantities of some emulsion stabilizers on the mean droplet size distribution of emulsions. In the examined narrow range of values no significant modifications of the mean droplet size distribution was observed.

Experimental Investigation of the Effect of Hydrogen Addition on Combustion Performance and Emissions Characteristics of a Spark Ignition High Speed Gasoline Engine

Abstract Considering energy crises and pollution problems today much work has been done for alternative fuels for fossil fuels and lowering the toxic components in the combustion products. Expert studies proved that hydrogen one of the prominent alternative energy source which has many excellent combustion properties that can be used for improving combustion and emissions performance of gasoline-fuelled spark ignition (SI) engines. This article experimentally investigated the performance and emission characteristics of a high speed single cylinder SI engine operating with different hydrogen gasoline blends. For this purpose the conventional carburetted high speed SI engine was modified into an electronically controllable engine with help of electronic control unit (ECU) which dedicatedly used to control the injection timings and injection durations of gasoline. Various hydrogen enrichment levels were selected to investigate the effect of hydrogen addition on engine brake mean effective pressure (Bmep), brake thermal efficiency, volumetric efficiency and emission characteristics. The test results demonstrated that combustion performances, fuel consumption and brake mean effective pressure were eased with hydrogen enrichment. The experimental results also showed that the brake thermal efficiency was higher than that for the pure gasoline operation. Moreover, HC and CO emissions were all reduced after hydrogen enrichment.

Air Catapult Transportation

The current flight passenger-transport and cargo systems have reached the peak of their development. In the last 30 years there has been no increase in speed or reductions in trip costs. The transportation industry needs a revolutionary idea, which allows jumps in speed and delivery capability, and dramatic drops in trip price. The author offers a new idea in transportation in which trip (flight) time practically does not depend on distance, and vehicle load capability doubles and has a driving engine that is located on the ground and can use any cheap source of energy. The author develops the theory and provides computations for project which contains five subprojects united the common idea: acceleration of the air vehicle on ground and continuation of flight by inertia (high speed catapulting). The initial speed is 290 - 6000 m/s, the range is 50 -10000 km (short, average, and long distances). Short transport system has range 50-70 km, for example: city - sub-city, strait and air bridges such as across the Straits of Gibraltar 16 km, the English Channel 40 km, Bering Straits 100 km (Russia-America), Sakhalin-Asia 20 km, Russia-Japan, etc. The long distance has range up 10000 km such as New York-Paris 5838 km, Washington-London 7373 km, San-Francisco - Tokyo 8277 km, San-Francisco - Vladivostok (Russia) 8377 km, New York - Moscow 7519 km, Moscow - Beijing 5800 km, Moscow - Tokyo 7487 km, New York - Berlin 6392 km, and so on. The offered catapult system having length of 400 km can be used as the space launch system which decreases the space launch cost in hundreds of times. That also may be used as the new conventional high speed (up 1000 km/h) transport system between cities. That will be significantly cheaper than used MagLev (Magnetic Levitation) systems, because suspending of the vehicle used the conventional wing. The offered system may be also used for the mass launch of bombs (projectiles) in war.

IR measurements of the thermodynamic effects in cavitating flow

The understanding of the thermodynamic effects of cavitating flow is crucial for applications like turbopumps for liquid hydrogen LH2 and oxygen LOx in space launcher engines. Experimental studies of this phenomenon are rare as most of them were performed in the 1960s and 1970s. The present study presents time resolved IR (Infra-Red) measurements of thermodynamic effects of cavitating flow in a Venturi nozzle.Developed cavitating flow of hot water (95°C) was observed at different operating conditions – both conventional high speed visualization and high speed IR thermography were used to evaluate the flow parameters.Both the mean features of the temperature distributions and the dynamics of the temperature field were investigated. As a result of evaporation and consequent latent heat flow in the vicinity of the throat a temperature depression of approximately 0.4K was measured. In the region of pressure recuperation, where the cavitation structures collapse, the temperature rise of up to 1.4K was recorded. It was found that the temperature dynamics closely follows the dynamics of cavitation structures.Finally experimental results were compared against a simple model based on the Rayleigh–Plesset equation and the thermal delay theory and plausible agreement was achieved.Experimental data is most valuable for further development of numerical models which are, due to poor ensemble of existing experimental results, still at a very rudimentary level.

Initial multicentre experience of high-speed myocardial perfusion imaging: comparison between high-speed and conventional single-photon emission computed tomography with angiographic validation

High-speed (HS) single-photon emission computed tomography (SPECT) with a recently developed solid-state camera shows comparable myocardial perfusion abnormalities to those seen in conventional SPECT. We aimed to compare HS and conventional SPECT images from multiple centres with coronary angiographic findings. The study included 50 patients who had sequential conventional SPECT and HS SPECT myocardial perfusion studies and coronary angiography within 3 months. Stress and rest perfusion images were visually analysed and scored semiquantitatively using a 17-segment model by two experienced blinded readers. Global and coronary territorial summed stress scores (SSS) and summed rest scores (SRS) were calculated. Global SSS ≥3 or coronary territorial SSS ≥2 was considered abnormal. In addition the total perfusion deficit (TPD) was automatically derived. TPD >5% and coronary territorial TPD ≥3% were defined as abnormal. Coronary angiograms were analysed for site and severity of coronary stenosis; ≥50% was considered significant. Of the 50 patients, 13 (26%) had no stenosis, 22 (44%) had single-vessel disease, 6 (12%) had double-vessel disease and 9 (18%) had triple-vessel disease. There was a good linear correlation between the visual global SSS and SRS (Spearman's ρ 0.897 and 0.866, respectively; p < 0.001). In relation to coronary angiography, the sensitivities, specificities and accuracies of HS SPECT and conventional SPECT by visual assessment were 92% (35/38), 83% (10/12) and 90% (45/50) vs. 84% (32/38), 50% (6/12) and 76% (38/50), respectively (p < 0.001). The sensitivities, specificities and accuracies of HS SPECT and conventional SPECT in relation to automated TPD assessment were 89% (31/35), 57% (8/14) and 80% (39/49) vs. 86% (31/36), 77% (10/13) and 84% (41/49), respectively. HS SPECT allows fast acquisition of myocardial perfusion images that correlate well with angiographic findings with overall accuracy by visual assessment better than conventional SPECT. Further assessment in a larger patient population may be needed to confirm this observation.

Clinical evaluation of conventional and laser tooth preparation using visual analogue scale

Context: Use of lasers in painless contemporary restorative dentistry. Aims: To assess the extent of painless perception using lasers for tooth preparation based on visual analogue scale (VAS). To compare conventional and laser tooth preparation using VAS scale. Settings and Design: Adult patients reporting to the Department of Conservative Dentistry were selected. Fotona fidelis make for ER:YAG laser was used at preset laser settings for enamel and dentin removal with combination of air-water spray. Materials and Methods: Standardized class I tooth preparation for composite restorations were selected for individuals requiring treatment for teeth with similar enamel/dentinal configuration, that is, contralateral in the same individual. Carbide burs-SS White #245 were used for all preparations. Identical tooth preparations were carried out by the same operator for both the teeth using conventional high speed on one side and ER:YAG laser at noncontact mode on the other side. Fotona fidelis make was used at preset laser settings for enamel and dentin removal with combination of air-water spray. The patient was required to provide score according to the VAS scale. Statistical Analysis Used: Kruskal-Wallis test. Results: The median of pain while preparing tooth by conventional method is the highest in patient (8) and the smallest in ER:YAG laser (1). The P value is very small (less than the common alpha-level of 0.05), the test is significant. Thus, it is concluded that the method of tooth preparation does affect the pain perception. Conclusions: The statistical analysis of these findings comprehensively prove that laser tooth preparation is much more painless, hence comfortable for the patient, only the economics prove to be a deterrent in its widespread usage.

Preparative enantioseparation of β-blocker drugs by counter-current chromatography using dialkyl l-tartrate as chiral selector based on borate coordination complex

Counter-current chromatography (CCC) was applied for preparative enantioseparation of three β-blocker drugs, including propranolol, pindolol and alprenolol. The two-phase solvent system was composed of chloroform–0.05molL−1 acetate buffer containing 0.10molL−1 boric acid (1:1, v/v), in which 0.10molL−1 di-n-hexyl l-tartrate was added in the organic phase as chiral selector. Influence factors in the enantioseparation of propranolol were investigated. The chromatographic retention mechanism based on borate coordination complex was proposed. 116mg of racemic propranolol was completely enantioseparated using conventional high speed CCC in a single run, yielding 48mg of (+)-propranolol with HPLC purity of 98.9% and 47mg of (−)-propranolol with HPLC purity of 96.3%. Recovery for propranolol enantiomers from CCC fractions was in the range of 75–82%. pH-zone-refining CCC was also successfully applied in enantioseparation of propanolol and it was found that 356mg of racemic propranolol could be completely enantioseparated. 145mg of (+)-enantiomer with HPLC purity of 95.6% and 148mg of (−)-enantiomer with HPLC purity of 98.2% were recovered from pH-zone-refining mode. Separation mechanism about chiral separation by pH-zone-refining CCC was discussed.

Simulation of spray development and turbulent combustion processes in low and high speed diesel engines by the CMC-ISR model

Simulation is performed to analyse the characteristics of turbulent spray combustion in conventional low and high speed diesel engine conditions. Turbulence–chemistry interaction is resolved by the Conditional Moment Closure (CMC) model in the spatially integrated form of an Incompletely Stirred Reactor (ISR). After validation against measured pressure traces, characteristic length and time scales and dimensionless numbers are estimated at the locations of sequentially injected fuel groups. Conditional flame structures are calculated for sequentially evaporated fuel groups to consider different available periods for ignition chemistry. Injection overlaps the combustion period in the high rpm engine, while most combustion occurs after injection and evaporation are complete in the low rpm engine. Ignition occurs in rich premixture with the initial peak temperature at the equivalence ratio around 2–4 as observed in Dec [2]. It corresponds to the most reactive mixture fraction of the minimum ignition delay for the given mixture states. Combustion proceeds to lean and rich sides in the mixture fraction space as a diffusion process by turbulence. The mean scalar dissipation rates (SDRs) are lower than the extinction limit to show stability of diffusion flames throughout the combustion period.

An Assessment of Cutting Force for Dental Implant Drilling

Bone drilling is widely used in orthopedics and dental surgery; it is a technically surgical procedure. Recent technological improvements in this area are focused on efforts to reduce forces in bone drilling. The aim of this study was to compare changes in cutting force during dental bone drilling at various drilling conditions and drill tool geometry. In the present in vitro study, dog jaw bone with uniform thickness of cortical bone was used. Cutting force changes were measured during drilling process. Drill jig was designed and manufactured to fix jaw workpiece and mounted on the tool dynamometer to measure cutting force in drilling process. The dental implant drilling tests were conducted at various cutting speeds and feed rates. In this study drilling thrust force was observed 1.5~3.6[N] for MS type implant drilling and 3.1~4.9[N] for conventional high speed steel drilling, respectively. This further research will provide a basic quantitative approach for the timely issue of wide application of implant drilling in dental and orthopedic surgery fields.

전차선로 전기적 특성 평가 시스템 구현

Currently in Korea, the simple catenary type overhead contact line system is being applied to both conventional lines and high speed lines of electric railway, and circulation current flowing into the catenary system frequently bring undesirable consequences. Namely, the connector wire has many problems according to a flow of excessive circulation current and arc current on catenary when an electric train runs at high speed. This paper presents the development and application of a real-time data acquisition system designed to measure the electrical characteristics of an overhead catenary system in electric railways. The developed system is capable of storing data of a 25 kV power source in a live wire state through a telemetry environment. The field test results show that the proposed technique and the developed system can be practically applied to measure characteristics of current of an overhead catenary system.

Study of Electroslag Remelted and Nitrogen Containing High Speed Tool Steel M41

Mossbauer Effect (ME) spectra, microstructure and hardness of some alloyed and conventional AISI M41 high speed tool steel samples produced by induction furnace as well as after doing electro-slag refining (ESR) process under different slag compositions have been investigated. The obtained ME spectra for all samples could be analyzed to a singlet and three sextets. The appeared singlet in the conventional steel and that alloyed with nitrogen as well as two refined samples using electro-slag remelting 1 and 2 (ESR1, M41N and ESR2, M41N) can be attributed to γ–austenite phase, while the singlet that appeared in the refined sample 3 (ESR3, M41N) can be attributed to some iron nitride of the form ( e-Fe2N). In the refined sample, which does not contain nitrogen, γ–austenite phase cannot be found and some α-Fe2O3 was detected. The observed three sextets were attributed to three different magnetic martensite phases. It appeared also that some transformations in between the three martensite phases and between martensite and austenite take place, and all these changes were thoroughly discussed. It is interesting to state that the obtained ME results are in agreement with those obtained from optical microscopy and micro-hardness measurements.

Study on Edge Contact Area and Surface Integrity of Workpiece in Point Grinding Process

During cylindrical grinding process, the geometric configuration and size of the edge contact area between the grinding wheel and workpiece have the heavy effects on the workpiece surface integrity. In consideration of the differences between the point grinding and the conventional high speed cylindrical grinding, the geometric and mathematic models of the edge contact area in point grinding were established. Based on the models, the numerical simulation for the edge contact area was performed. By means of the point grinding experiment, the effect mechanism of the edge contact area on the ground surface integrity was investigated. These will offer the applied theoretic foundations for optimizing the point grinding angles, depth of cut, wheel and workpiece speed, geometrical configuration and size of CBN wheel and some other grinding parameters in point grinding process.

Design and Synthesis of Pareto Buffers Offering Large Range Runtime Energy/Delay Tradeoffs Via Combined Buffer Size and Supply Voltage Tuning

This paper presents a formalized synthesis methodology for variable tapered buffer chains achieving Pareto optimal energy-delay (E/D) tradeoffs via the buffer gate sizes and adding supply voltage as an extra tuning knob. In addition, a detailed discussion of the practically achievable tradeoff ranges via the gate size and especially supply voltage tuning is present. We have applied the methodology for the design and fine tuning of the run-time switchable buffers within the Level-1 (L1) embedded SRAMs (eSRAM), confirming that a very wide range in delay and energy reduction (up to 50%) can be achieved when compared to solely optimal speed eSRAM design using conventional high speed buffers.

Study on Edge Contact Area and Surface Integrity of Workpiece in Point Grinding Process

During cylindrical grinding process, the geometric configuration and size of the edge contact area between the grinding wheel and workpiece have the heavy effects on the workpiece surface integrity. In consideration of the differences between the point grinding and the conventional high speed cylindrical grinding, the geometric and mathematic models of the edge contact area in point grinding were established. Based on the models, the numerical simulation for the edge contact area was performed. By means of the point grinding experiment, the effect mechanism of the edge contact area on the ground surface integrity was investigated. These will offer the applied theoretic foundations for optimizing the point grinding angles, depth of cut, wheel and workpiece speed, geometrical configuration and size of CBN wheel and some other grinding parameters in point grinding process.

A novel compact high speed x-ray streak camera (invited)

Conventional in-line high speed streak cameras have fundamental issues when their performance is extended below a picosecond. The transit time spread caused by both the spread in the photoelectron (PE) "birth" energy and space charge effects causes significant electron pulse broadening along the axis of the streak camera and limits the time resolution. Also it is difficult to generate a sufficiently large sweep speed. This paper describes a new instrument in which the extraction electrostatic field at the photocathode increases with time, converting time to PE energy. A uniform magnetic field is used to measure the PE energy, and thus time, and also focuses in one dimension. Design calculations are presented for the factors limiting the time resolution. With our design, subpicosecond resolution with high dynamic range is expected.

Micromorphologic assessment of CVD (chemical vapor deposition) and conventional diamond tips and their cutting effectiveness

The aim of this study was to compare the micromorphology of CVD diamond tips coupled to ultrasound with conventional high speed diamond tips after cavity preparations, and to measure the width and depth of the cavities obtained. Two hundred bovine teeth were divided into 20 subgroups. Each of the diamond tips (10 CVD and 10 conventional) were used to prepare 10 standardized cavities, using an apparatus that controlled the time (t: 27 s), speed (5.3 mm/s) and load (0.012 KGF) of the tip against the teeth during preparation. The unused and the used (after one, five and 10 preparations) tips were analyzed by scanning electronic microscopy. The images were randomly assessed by 3 examiners with regard to the presence or absence of micromorphologic alterations. Cavity measurements were made after visualization under a stereoscopic microscope. Cavity widths and depths were analyzed by the ANOVA Factorial test (p < 0.05). The CVD diamond tips presented less wear than the conventional tips after all the cavity preparations performed, but produced shallower cavities that were equivalent in width to those made by conventional tips after the fifth preparation. CVD diamond tips may be suggested as an alternative to conventional diamond tips due to their conservative preparation and greater longevity.

Evaluación del comportamiento de herramientas de corte en el proceso de cilindrado, mediante el uso de números adimensionales

El presente trabajo consiste en la aplicación de la técnica de análisis adimensional utilizando el teorema p de Buckingham al estudio del desgaste de herramientas de acero rápido sinterizado, acero rápido, de metal duro widia e inserto de carburo de tungsteno, realizando operaciones de cilindrado. Las pruebas se llevaron a cabo en talleres industriales de Bogotá y Barrancabermeja, utilizando diferentes materiales para la pieza de trabajo y variadas condiciones de corte para la herramienta hasta llegar a desgastarla. La información recopilada permitió graficar la relación log-log entre dos parámetros adimensionales (PI1, PI2). Los datos de corte mostraron convergencia en torno a zonas particulares que facilitaron hacer las comparaciones entre herramientas. La comparación experimental, basada en los parámetros adimensionales PI1 y PI2, demostró que es posible elaborar una norma Colombiana para evaluar herramientas en variadas condiciones de operación.

DEVELOPMENT OF SEMI-VLBI SYSTEM AND OBSERVATION OF SUN AT 21 cm

We report the development of a semi-VLBI observation system operating at 21 cm and present the measurement of visibility function toward the sun using this system. The system consists of two 2.3 meter antennas with a maximum separation of 35 meter, a conventional high speed data acquisition system, and a set of programs for software correlation. Since two local oscillators of receiver modules are independent, data had to be fringe-fitted to yield the visibility amplitude. It is found that the visibility amplitude decreases and then bounces back as baseline increases. We confirm that solar disk with brighter limb best explains the measured visibility amplitude.

金属ガラスの最適製造プロセスの開発および得られた金属ガラスの性質

In this report, structures and mechanical properties were studies for rapidly solidified Ni-Nb-Zr alloys and glassy Fe-based alloys shots with high strength and long life time for shot peening. The results obtained are summarized as follows.Rapidly solidified Ni-Nb-Zr alloys were formed in a wide composition range of 20 to 75at%Ni, 0 to 60 at%Nb and 0 to 80 at%Zr for formation of amorphous phase, 50 to 70at%Ni, 5 to 35 at%Nb and 5 to 45 at%Zr for formation of glass phase, respectively. The largest value of the supercooled liquid region was 51 K for Ni60Nb20Zr20 alloy. The crystallization temperature (Tx), Vickers hardness (Hv) and fracture strength (σf) of the amorphous (Ni0.5Nb0.5)100-xZrx (x=10, 20, 30 40) alloys were in the rang from 770 to 870 K, 540 to 760 and 1530 to 2300 MPa, respectively. The σf and Hv of the glassy Ni60Nb20Zr20 alloy with the largest supercoold liquid region are 2160 MPa and 700, respectively. The hydrogen permeability of the amorphous (Ni0.6Nb0.4)70Zr30 alloy ribbon was 1.3×10-8 mol/m-1/s-1/Pa-1/2 at 673 K which is slightly larger than that of thin pure Pd metal. Wide ribbons of 50 mm in wide were prepared for the amorphous Ni42Nb28Zr30 and glassy Ni60Nb20Zr20 alloys.Amorphous/glassy phases with volume fraction exceeding 98% in (Fe, Co, Ni)75B14Si8Mo3 alloy powder with spherical form of about 500μm in diameter were formed with wide composition ranges of 45 to 100at%Fe, 0 to 50at%Co and 5 to 55at%Ni, respectively. Glass transition temperature (Tg), Tx and supercoold liquid region (ΔTx=Tx-Tg) of Fe46Co5Ni24B14Si8Mo3 alloy were 789 K, 833 K and 44 K, respectively. The endurance life time of the glassy Fe-based alloy shots was 4 to 10 times longer than those for the conventional cast steel and high speed steel shots in the same shot peening condition. The maximum value of compressive residual stress in the tool (SKD11) steel shotted were 1600 MPa for the glassy Fe-based alloy shot and 1470 MPa for high speed steel shot, respectively.