Automated GUI performance testing

A significant body of prior work has devised approaches for automating the functional testing of interactive applications. However, little work exists for automatically testing their performance. Performance testing imposes additional requirements upon GUI test automation tools: the tools have to be able to replay complex interactive sessions, and they have to avoid perturbing the application’s performance. We study the feasibility of using five Java GUI capture and replay tools for GUI performance test automation. Besides confirming the severity of the previously known GUI element identification problem, we also describe a related problem, the temporal synchronization problem, which is of increasing importance for GUI applications that use timer-driven activity. We find that most of the tools we study have severe limitations when used for recording and replaying realistic sessions of real-world Java applications and that all of them suffer from the temporal synchronization problem. However, we find that the most reliable tool, Pounder, causes only limited perturbation and thus can be used to automate performance testing. Based on an investigation of Pounder’s approach, we further improve its robustness and reduce its perturbation. Finally, we demonstrate in a set of case studies that the conclusions about perceptible performance drawn from manual tests still hold when using automated tests driven by Pounder. Besides the significance of our findings to GUI performance testing, the results are also relevant to capture and replay-based functional GUI test automation approaches.     

Study of Silicon Cantilevers by the Photoacoustic Elastic Bending Method

Rectangular silicon cantilevers are studied by the photoacoustic (PA) elastic bending method. Experimental signals versus modulation frequency of the excitation optical beam are measured and analyzed in a frequency range from 20 Hz to 50 000 Hz. The procedure for experimental signal correction to eliminate the frequency characteristics of the measuring system is given. The corrected experimental signal shows a good correlation with theoretically calculated PA signal at frequencies below 32 000 Hz. The corrected experimental PA elastic bending signals for cantilevers with different thicknesses are analyzed. The experimental results allow identifying the resonant frequency (the first resonant mode) of the cantilever vibrations. These values are in good agreement with the theoretically computed values. A theoretical model of the optically excited Si cantilever is derived, taking into account plasmaelastic, thermoelastic, and thermodiffusion mechanisms. Dynamic relations for the amplitude and phase of electronic and thermal elastic vibrations in optically excited cantilevers are derived. The theoretical model is compared to the experimental results.     

The corrosion behavior of Ti3SiC2 in common acids and dilute NaOH

Hot isostatically processed bulk, fine (3-5 μm) grained samples of Ti₃SiC₂ were immersed in concentrated and dilute hydrochloric, HCl, sulphuric, H₂SO₄, nitric, HNO₃, dilute hydrofluoric, HF, acids and sodium hydroxide, NaOH, solutions at room temperature. Based on six-months weight changes the dissolution rates of Ti₃SiC₂ in concentrated and dilute HCl, H₂SO₄ and dilute NaOH were found to be negligible (<2 μm/yr). In dilute HF and concentrated HNO₃ the corrosion rates were, respectively, ≈5 μm/yr and 13 μm/yr respectively. In contrast to Ti metal, the weight losses of Ti₃SiC₂ in dilute HNO₃ were higher (≈250-320 μm/yr) and depended on concentration. Post-immersion scanning electron microscopic micrographs of samples immersed in HNO₃ indicated that an oxygen rich Si-based layer forms on the surface of the samples. This implies that the Ti atoms are leached out into the HNO₃ solution, leaving behind a Si-rich layer that is ultimately oxidized. Cyclic polarization and potentiostatic i-t transients in dilute HCl and H₂SO₄ acids, strongly suggest that a thin irreversible electrically insulating layer forms on the surface of Ti₃SiC₂. Exposing a sample to a constant current density of 0.6 mA/cm² for two days resulted in the formation of a 5 μm thick SiO₂-based layer on the surface. The presence of such a layer would explain the excellent corrosion resistance of Ti₃SiC₂ in these acids.     

Effects of Conformal Nanoscale Coatings on Thermal Performance of Vertically Aligned Carbon Nanotubes

The high aspect ratio and the porous nature of spatially oriented forest‐like carbon nanotube (CNT) structures represent a unique opportunity to engineer a novel class of nanoscale assemblies. By combining CNTs and conformal coatings, a 3D lightweight scaffold with tailored behavior can be achieved. The effect of nanoscale coatings, aluminum oxide (Al₂O₃) and nonstoichiometric amorphous silicon carbide (a‐SiC), on the thermal transport efficiency of high aspect ratio vertically aligned CNTs, is reported herein. The thermal performance of the CNT‐based nanostructure strongly depends on the achieved porosity, the coating material and its infiltration within the nanotube network. An unprecedented enhancement in terms of effective thermal conductivity in a‐SiC coated CNTs has been obtained: 181% compared to the as‐grown CNTs and Al₂O₃ coated CNTs. Furthermore, the integration of coated high aspect ratio CNTs in an epoxy molding compound demonstrates that, next to the required thermal conductivity, the mechanical compliance for thermal interface applications can also be achieved through coating infiltration into foam‐like CNT forests.     

Cancrum oris: management, incidence, and implications of human immunodeficiency virus in Zambia

BACKGROUND: Limitations in the imaging views that can be obtained with transesophageal echocardiography (TEE) have hindered development of a widely adopted Doppler method for cardiac output (CO) monitoring. The authors evaluated a CO technique that combines steerable continuous-wave Doppler with the imaging capabilities of two-dimensional multiplane TEE. METHODS: From the transverse plane transgastric, short-axis view of the left ventricle, the imaging array was rotated to view the left ventricular outflow tract (LVOT) and ascending aorta. Steerable continuous-wave Doppler was subsequently used to measure aortic blood flow velocities. Aortic valve area was determined using a triangular orifice model. Matched thermodilution and Doppler CO measurements were obtained serially during surgery. RESULTS: The left ventricular outflow tract was imaged in 32 of 33 patients (97%). Data analysis reveal a mean difference between techniques of -0.01 l/min, and a standard deviation of the differences of 0.56 l/min. Multiple regression showed a correlation of r = 0.98 between intrasubject changes in CO. Multiplane TEE correctly tracked the direction of 37 of 38 serial changes in thermodilution CO but with a modest 14% underestimation of the magnitude of these changes. CONCLUSIONS: These results indicate that multiplane TEE can provide an alternative method for the intraoperative measurement of CO. The ability of the rotatable imaging array to align with the left ventricular outflow tract and the need for only minimal adjustments in probe position advance the utility of intraoperative TEE.     

Chaos-based multi-user time division multiplexing communication system

A chaos-based multi-user time division multiplexing (TDM) communication system has been proposed and its benchmark performance compared to that of the chaos-based direct sequence code division multiple access (DS-CDMA) system in the noisy and Rayleigh fading channels. The benchmark performance of the systems is investigated in terms of the bit error rate (BER) under the assumption of perfect synchronisation. The chaotic spreading signals, used to encrypt the binary messages, are generated using the logistic map. The degradation in performance of the systems in the Rayleigh fading channel when compared with the noisy channel is demonstrated. Furthermore, it is shown that in both noisy and Rayleigh fading channels, the chaos-based multi-user TDM system outperforms the chaos-based DS-CDMA system for a large number of users in the system, whereas the chaos-based DS-CDMA system yields better performance for low user numbers. The overall BER performance degradation for the chaos-based DS-CDMA multi-user system in noisy and Rayleigh fading channels is characterised by the flattening of the BER curves at low levels of noise due to the prevailing effects of the interuser interferences.     

Quality control engineering in automated ceramic tile production using a signal information content approach

The pressing process in the automated production of ceramic tiles is a complicated process that involves fully functional machinery and efficient coordination of the working crew. Quality control (QC) of the process relies on reasoning and acting on information coming from measured signals on the automated machinery. For QC, it is necessary to establish that these measurements are correct for the purpose of final product quality. In the process, tile batches are produced within a tolerable range of tile rejection. However, if the percentage of rejects rises above a certain threshold, e.g. 6%, the QC staff are responsible for finding the cause of the defect.The aim of this work is the investigation of a short-term information measure, expanded tessellation entropy, which can aid the QC staff in discovering the causes of deviations in the quality of batch production of ceramic tiles. This unique signal measure is calculable from as few as four consecutive machinery signal measurements, it is sensitive to small changes in the signal, and its computation is fast. Its noise sensitivity is tested for a set of four standard analytical process signals, with the addition of 1% random noise, and is shown to be robust with appropriate setting. The information measure is applied to measured process-machinery signals, and the results are compared with the QC signal that measures the tile rejection rate. An interpretation procedure is proposed and applied that reveals which signals are significant for increased tile rejection. The procedure is based on comparing signals and QC sequences with similar information code patterns. The results show that the defects are mainly due to human error, and that they usually start with improper furnace handling or uncompensated tile humidity. The method is compared to Shannon entropy, approximate entropy, Pearson correlation, and control charts, and it is shown to be superior for detection of faults in a setting where there is not much historical data available for statistical analysis, and where the quality of the process (percentage of rejects) is continuously measured as a target signal. In employing the proposed procedure, all of the QC defects were explained. The interpretation procedure is not fully automated at this moment. However, it is shown to be applicable to monitoring automated press machines in a ceramic tile plant, and thus preventing future defects. It can be applied to other similar automated industrial processes.     

Performance comparison of multi-user chaos-based DS-CDMA synchronisation unit within AWGN and Rayleigh fading channel

The performance of a multi-user chaos-based direct sequence code division multiple access (DS-CDMA) communication system with a sequence synchronisation unit incorporated is examined. Synchronisation is achieved through code acquisition and maintained through the code tracking phase. The performance of the proposed system is evaluated in a Rayleigh fading channel with additive white Gaussian noise and interuser interference. Results are compared to a fade-free channel. It is shown that, although the system is robust to the influence of noise and interuser interferences, it fails to satisfy the maximum allowable bit error rate limit of 10^-3 in the Rayleigh fading channel.     

Trace metal concentrations in Mediterranean blue mussel and surface sediments and evaluation of the mussels quality and possible risks of high human consumption

The concentrations of trace metals (Fe, Zn, Mn, Ni, Cu, Co and Cr) were determined for the first time in Mediterranean blue mussels (Mytilus galloprovincialis) and surface sediments. The mussel and sediment samples were collected from five sites on the Montenegrin coastal area (southeastern Adriatic Sea) in the fall of 2005 and 2006. The collected samples were digested with a microwave digestion system. The maximum Fe, Zn, Mn, Ni, Cu, Co and Cr mean concentrations in the mussel samples were 603.0, 345.0, 85.0, 18.9, 17.2, 9.1 and 4.2 mg/kg of sample dry weight, respectively. The maximum Fe, Mn, Cr, Ni, Zn, Cu and Co concentrations in the sediment samples were 40867, 943.0, 382.0, 336.0, 67.2, 24.8 and 16.9 mg/kg of sample dry weight, respectively. A correlation between the metal levels found in the mussel soft tissues with those found in sediments, for both 2005 and 2006, could be established, except for the levels of Zn observed.