Quantitative Performance Analysis Research Articles

Time as a measure: Elementary students positioning the hands of an analog clock

Elementary students have difficulty with the topic of time. The present study investigated students’ actions to position hour and minute hands on an analog clock to indicate particular times of the day. Using one-on-one interviews with students in Grades 2 and 4 (n = 48), we analyzed whether students were more accurate for one hand indicator (hour or minute) versus the other as well as their solution approaches as they positioned each hand. We first present a quantitative analysis of student performance to document whether hour and minute hands posed differential challenges for students as they positioned hands to indicate particular times. Results indicate the hour hand is significantly more challenging to position accurately than the minute hand. Students’ solutions reflected varied approaches, including consideration of the quantitative hour-minute multiplicative relationship, attention to part-whole relations, and matching numbers from the provided time to numerals on the clock. We discuss implications for theory and instruction, including the relationship of time to length measure learning trajectories and the current treatment of time in K-12 mathematics standards for the United States.

Outage Probability Analysis and Dynamic Criterion Calculation Under the Plasma Sheath Channel

Dynamic plasma sheath can lead to the communication interruption because of its severe impact on the electromagnetic waves. Existing studies mainly focused on the numerical analysis, either regarding the specific experimental results or regarding the computational modeling of the plasma sheath channel, without theoretical and quantitative analysis of the communication performance. In this paper, the bit error rate and the outage probability with $m$ -ary frequency shift keying modulation are derived theoretically based on the hidden Markov model of plasma sheath channels. Specifically, since the outage probability can be viewed as the probability of an interruption in the communication system, it can reflect the intensity of the channel dynamics. Therefore, we analyze the effect of channel model parameters on the outage probability and propose a dynamic criterion calculation formula to model the dynamic of the plasma sheath channel. Finally, simulation results are carried out to reveal a positive correlation between the dynamic criterion and the outage probability, which shows that the dynamic criterion calculation formula can accurately illustrate the dynamic of the plasma sheath channel and the communication performance.

An Automatic Data-Driven Method for SAR Image Segmentation in Sea Surface Analysis

In the context of synthetic aperture radar (SAR) image segmentation, this paper proposes a new automatic unsupervised method addressing sea surface analysis with a focus on oil spill and ship segmentation. Being an evolution of an existing algorithm originally devoted to the detection of a single region of interest, the present method performs a global image segmentation of the whole image. The processing is independent of any model and is driven by data informative content along with intermediate results. Based on graph theory, it makes use of a new defined cost function and assigns cost values to the vertices rather than to the edges of the graph. The experimental results achieved and numerically evaluated on synthetic and real SAR images prove that the method is robust and repeatable, and it does not involve restrictions on image modality acquisition or sensors and does not require radiometric calibration. It can work on amplitude or intensity SAR images, independently on frequency band, polarimetry, and spatial resolution. Qualitative and quantitative performance analyses are carried out along with a comparison with other published works in the same application. Good results are achieved for both oil spill and ship segmentation and robustness by changing seed points position and number. Errors exhibit stable behavior when increasing the number of seed points. Finally, in contrast to most of the existing methods, the proposed technique does not depend on parameters and is generally more robust.

A comparative investigation on in-situ and laboratory standard test of the potential induced degradation of crystalline silicon photovoltaic modules

Abstract Potential induced degradation (PID) is one of the genuinely critical concerns of a sustainable power generation from a PV system. Generally, the PID behavior of a PV module is tested in the laboratory according to the IEC standard before installation into a plant. On the other hand, an electroluminescence imaging is a reliable technique to identify the different types of PV cell defects which cause the degradation of the PV modules. The aim of this research is to investigate the PID behavior of similar PV modules in both the real on-site test and the laboratory standard test conditions. This will facilitate the outcome of the tangible indoor PID test results with more ease and reliability. It has been observed from the EL images of the on-site degraded PV module that a performance degradation happens due to different types of PV cell defects, such as, localized shunting, cracks, front contact grid interruptions, etc. The maximum power versus EL mean intensity shows a linear relationship which predicts the quantitative performance analysis of a PV module from an EL imaging process. The PID of a PV module has been found in a negative voltage stress condition in both the on-site and the laboratory tests. The shunt resistance gradually decreases as a consequence of the negative voltage stress only. The on-site degradation levels of the Pmax, Voc, Isc, and FF are 46.5, 7.15, 30.4, and 17.35% respectively after a duration of nearly 11 years of a negative voltage stress generated from a 240 V string size. In a laboratory PID test, the Pmax, Voc, Isc, and FF are degraded due to a negative voltage stress with a value of 6.83%, 1.9%, 1.5%, and 3.5% respectively.

Compressed Animated Light Fields with Real-Time View-Dependent Reconstruction.

We propose an end-to-end solution for presenting movie quality animated graphics to the user while still allowing the sense of presence afforded by free viewpoint head motion. By transforming offline rendered movie content into a novel immersive representation, we display the content in real-time according to the tracked head pose. For each frame, we generate a set of cubemap images per frame (colors and depths) using a sparse set of of cameras placed in the vicinity of the potential viewer locations. The cameras are placed with an optimization process so that the rendered data maximise coverage with minimum redundancy, depending on the lighting environment complexity. We compress the colors and depths separately, introducing an integrated spatial and temporal scheme tailored to high performance on GPUs for Virtual Reality applications. A view-dependent decompression algorithm decodes only the parts of the compressed video streams that are visible to users. We detail a real-time rendering algorithm using multi-view ray casting, with a variant that can handle strong view dependent effects such as mirror surfaces and glass. Compression rates of 150:1 and greater are demonstrated with quantitative analysis of image reconstruction quality and performance.

Numerical analysis on the effect of bifurcation angle and inlet velocity on the distribution uniformity performance of consecutive bifurcating fluid flow distributors

2-D numerical models have been used to analyze flow distribution performance in consecutive bifurcating fluid flow distributors according to constructal theory. The quantitative analysis of flow distribution uniformity performance for Y shape distributors with different bifurcation angles as well as inlet velocities are evaluated with water as working fluid, a hypothesis on the mechanism for the maldistribution is also presented. It is found that the flow distribution uniformity deteriorates with the increase of bifurcation angles from 15° to 90°, and the worst performance occurs when bifurcation angle is 90°, where the largest pressure drop also appears. Furthermore, the flow distribution performance also decreases with increasing inlet velocity for the same distributor. Finally, an improvement to obtain more uniform flow uniformity for the T shape distributor is proposed by ‘shrinking’ the vertical channel width of each bifurcation. The conclusions obtained in this paper are potentially helpful for the design of fluid distributors for multi channel devices.

Off-design performance analysis of a combined cooling and power system driven by low-grade heat source

The combined cooling and power (CCP) system integrating the organic Rankine cycle with the ejector refrigeration cycle is a modern solution for low-grade geothermal water. This paper conducts a quantitative analysis of the off-design performance of a CCP system based on a specially designed combination of a radial inflow turbine, an ejector and plate heat exchangers. The CCP system operating at a vapor split ratio of 0.5 is studied, and a novel preliminary design and off-design simulation process are presented. The sliding pressure operation strategy is used to achieve good off-design performance. The results indicate that the CCP system produces 153.76 kW cooling and has a cooling to net power ratio of 1.58 at the design point. The increasing geothermal water mass flow rate ratio could lower thermal efficiency, exergy efficiency and cooling to net power ratio. Higher geothermal water inlet temperature results in lower thermal efficiency. Among the geothermal water inlet temperature, the saturated condensing temperature and the evaporator saturated temperature, the net power is affected mostly by the saturated condensing temperature while the cooling and thermal efficiency are mostly influenced by the evaporator saturated temperature.

Quantitative analysis of the anti-noise performance of an m-sequence in an electromagnetic method

Quantitative analysis of the anti-noise performance of an <i>m</i>-sequence in an electromagnetic method

Numerical simulation of mixing process in T-shaped and DT-shaped micromixers

ABSTRACTRecently, numerous studies have been done on the micro- and nano-scale equipment because of their importance and wide range of application. Micromixers are among the equipment in which two or more fluids are mixed and have applications in the processes, such as chemical synthesis. In this research, a numerical investigation using finite volume approach is done on mixing two incompressible fluids in 3D mixers with T- and double-T-(DT) shaped geometries in the range of Reynolds numbers 75–400. One of the important parameters for the quantitative analysis of the mixing performance of micromixers is the mixing index. So, the effects of different geometries, Reynolds number and channel length on this parameter are studied. The results show that, at different Reynolds numbers, the mixing index of fluids in the DT-shaped channel with 90° is less than the corresponding one in T-shaped mixers because changing the flow regime occurs at higher Reynolds numbers in the DT-shaped channels. The amount of mixing index increases by decreasing the angle of branches in the DT-shaped channel. It is observed that the mixing index of fluids increases along the channel, which tends to a constant value far away from the inlet.

Performance Evaluation of MRI Tumor Segmentation Using Clustering Algorithms

Background: Magnetic resonance imaging (MRI) segmentation assumes great importance in research and clinical applications. The brain segmentation using MRI is challenging due to a significant amount of noise caused by operator performance, scanner, and the environment, which can lead to serious inaccuracies with segmentation. Evaluations of segmentation results in medical imaging are caused by the absence of a gold standard. So, the performance evaluation of these methods would be necessary. Methods: In this paper, the performance of clustering algorithms such as Fuzzy C-Means (FCM), Hard C-Means (HCM), and Neural Gas (NG) for tumor detection is evaluated on 100 downloaded images. For this purpose, we evaluated these 3 algorithms under noise condition, convergence speed. Compared with manual segmentation by an expert radiologist, sensitivity, specificity, and accuracy are calculated for each segmentation methods. Results: It can be stated, based on the results, that among the HCM and NG algorithms, the highest degree of accuracy and robustness to noise belongs to FCM. Moreover, optimum convergence rate and iteration need to gain final result using FCM algorithm. Conclusion: All the quantitative performance analysis and visual comparisons clearly demonstrated the superiority of FCM algorithm for MRI-based tumor detection.

Robust-Adaptive Controller Design for Robot Manipulators Using the $\mathcal{H}_{\infty}$ Approach

This paper proposes a model-free robust-adaptive controller for Euler–Lagrange systems with a quantitative performance analysis in terms of state-errors. The controller has only few parameters, and the procedure of finding the controller parameters is intuitive and easy to implement. The controller acts as an adaptive computed-torque controller and consists of two feedback loops: the inner loop evaluates the robot dynamics to linearize the system and the outer loop is a simple proportional derivative controller. Input-to-state stability is used to derive the control law and tune the controller parameters. Inverse-optimal control using the Hamilton–Jacobi–Isaacs equations is utilized to confirm the optimality of the controller. Robustness of the proposed controller is proved using the $\mathcal {H}_{\infty }$ optimality technique. The controller starts with zero system information and adapts itself to the real system dynamics. Finally, the proposed technique is validated on a three-degree-of-freedom and a seven-degree-of-freedom robot manipulator.

Improved patch‐based NLM PolSAR speckle filter based on iteratively re‐weighted least squares method

The non-local means filters are popular and effective in speckle filtering as well as preservation of subtle details but have certain limitations. The limitation of NLM filter is its biased estimation in case of excessive speckle noise. Also, the similarity measure which preserves polarimetric or scattering property of data is the matter of interest in recent works. In this paper, a speckle filtering technique is presented which apart from reducing speckle noise, preserves polarimetric property, fine structures of the polarimetric SAR data and leads to an unbiased estimation in excessive noise. The filtering method adjusts weights iteratively, such that norm of distances is minimized. The proposed method is validated over two real PolSAR datasets (captured over San Fransisco Bay, USA & Mumbai coastal area, India by RADARSAT-2) and a synthesized SAR image. The qualitative and quantitative performance analysis is presented for the proposed method in terms of visual appearance of span, RGB PolSAR images, ENL and B-index. The proposed method is also evaluated for PSNR and SSIM on synthesized SAR image. It is found that the proposed method performs better than NLM filter and can be considered as a good alternative to NLM filters.

Morphological analysis and reliability assessment: systemic-structural activity theory approach

Currently the most common ergonomic experiments often do not have sufficient external validity. To overcome this negative factor it is important to develop formalised and analytical methods of studying human performance. In this work authors describe the morphological analysis of tasks offered by systemic-structural activity theory. Morphological analysis is a general method for non-quantified modelling of various objects. In systemic-structural activity theory it is a systemic qualitative description of the structure of designed and often not yet existing activity. Such morphological analysis facilitates farther quantitative analysis of the operators' performance. It allows not just to optimise the methods of performance but also to improve equipment and HCI design.

A Survey on Virtual Machine Migration: Challenges, Techniques, and Open Issues

When users flood in cloud data centers, how to efficiently manage hardware resources and virtual machines (VMs) in a data center to both lower economical cost and ensure a high service quality becomes an inevitable work for cloud providers. VM migration is a cornerstone technology for the majority of cloud management tasks. It frees a VM from the underlying hardware. This feature brings a plenty of benefits to cloud providers and users. Many researchers are focusing on pushing its cutting edge. In this paper, we first give an overview of VM migration and discuss both its benefits and challenges. VM migration schemes are classified from three perspectives: 1) manner; 2) distance; and 3) granularity. The studies on non-live migration are simply reviewed, and then those on live migration are comprehensively surveyed based on the three main challenges it faces: 1) memory data migration; 2) storage data migration; and 3) network connection continuity. The works on quantitative analysis of VM migration performance are also elaborated. With the development and evolution of cloud computing, user mobility becomes an important motivation for live VM migration in some scenarios (e.g., fog computing). Thus, the studies regarding linking VM migration to user mobility are summarized as well. At last, we list the open issues which are waiting for solutions or further optimizations on live VM migration.

Morphological analysis and reliability assessment: systemic-structural activity theory approach

Currently the most common ergonomic experiments often do not have sufficient external validity. To overcome this negative factor it is important to develop formalised and analytical methods of studying human performance. In this work authors describe the morphological analysis of tasks offered by systemic-structural activity theory. Morphological analysis is a general method for non-quantified modelling of various objects. In systemic-structural activity theory it is a systemic qualitative description of the structure of designed and often not yet existing activity. Such morphological analysis facilitates farther quantitative analysis of the operators' performance. It allows not just to optimise the methods of performance but also to improve equipment and HCI design.

The role of decision support frameworks in industrial policy development: A South African iron and steel scrap case study

Downstream mineral resource beneficiation has potential to promote socio-economic growth in resource-rich nations, which has resulted in it receiving growing prioritisation and promotion in a number of African nations. Decisions surrounding downstream mineral beneficiation are complex due to the multitude of factors to be considered to ensure maximum sustainable benefits are realised. Decision support frameworks (DSFs) are recognised to be of value for strategic planning in the minerals sector. This paper explores DSF applicability by means of a case study of the South African iron and steel scrap industry, with a focus on the potential for increased local beneficiation of scrap in steel mills or foundries. The findings reinforce the value of the stakeholder consultation process that underpins DSFs in enabling the exploration of the underlying complexities and factors that contribute to any challenges an industry may be facing, as well as their effect on different stakeholders. In this case, a policy intervention was implemented in a bid to increase local beneficiation. However, there has been no indication of it achieving its objectives with stakeholders reporting it was not effectively tailored in the context of the sustainability issues being faced by the industry, due to insufficient meaningful stakeholder consultation. The structure of DSFs forced stakeholders who prioritised micro-economic issues to engage with sustainability issues beyond their purview. The results of the quantitative performance analysis demonstrate the complexity associated with sustainability performance assessments with no alternative definitely out-performing the others. Thus, in existing industries, DSFs can facilitate informed decision-making based on the current health of an industry as well as long-term potential sustainability benefits that could be realised. Ultimately, this may enable the development of well-informed targeted strategies and policies that take into consideration the realities of the industry as well as stakeholder perspectives, increasing the likelihood of their success. This is of particular importance in the context of African downstream mineral beneficiation, which in many cases has been bedevilled by a lack of grounded and targeted policies.

Study on off-design performance of transcritical CO2 power cycle for the utilization of geothermal energy

Exploiting renewable energy could greatly alleviate current severe energy situation. Transcritical CO2 (tCO2) cycle system as a type of competitive and promising energy converter could utilize low temperature geothermal energy effectively. In this paper, the methodology for the off-design operation of tCO2 system has been proposed and the quantitative performance analysis is carried out for the utilization of geothermal energy. With the aim at obtaining better thermodynamic and economic performance, the optimal power cycle parameters can be determined by the non-dominated sorting genetic algorithm-II (NSGA-II) in the design stage. The models of exergoeconomic analysis and main system components including turbine, pump and heat exchangers are established. The sliding pressure control strategy is applied to respond to the varieties of heat source and heat sink conditions in the off-design stage. Results show that there exists an optimal value of geothermal resource mass flow rate to maximum the thermal efficiency. The pump rotational speed increases linearly with the increasing geothermal resource temperature and geothermal resource mass flow rate while the pump rotational speed is gradually sensitive to the increase of heat sink temperature. The guideline listed in the table for pump could provide effective reference for practical operation.

Faktor-Faktor yang Mempengaruhi Sisa Hasil Usaha Koperasi Syariah Masjid di Bandung

The purpose of this research is (1) to identify the factors that influence the rest of the result of sharia mosque cooperative business in Bandung, (2) To describe the implementation of sharia system to acquire SHU in sharia cooperative mosque in Bandung. The object of research is ten sharia co-operative mosque in Bandung which already have legal body and active in its operational activity. The research variables consist of independent variables (X1: number of cooperative members, X2: business volume, X3: amount of deposits, X4: total debt) and dependent variable (residual result of SHU). Sharia cooperative performance is measured by: Capital Ratio, Efficiency Ratio, Liquidity Ratio, Independence Rate Ratio and Cooperative Growth followed by regression and correlation analysis between independent and dependent variable. Quantitative performance analysis results show the average capital ratio, efficiency ratio, profitability, service operational independence from 2010 to 2012 increased. The liquidity ratio shows the capability of the sharia mosque cooperative in fulfilling its short-term obligations in 2010-2011 just in time. The results showed that business volume factors (X2) and the amount of debt (X4) had a dominant influence in SHU formation in Shariah cooperative mosque in Bandung City. Implementation of Sharia System on the acquisition of SHU in Sharia Cooperative Mosque in Bandung City has shown complied with the calculation of sharia pattern in accordance with the Decree of State Minister of Cooperatives and Small and Medium Business Dam. 91 /KEP / M.KUKM / IX / 2004. Sharia co-operative mosque in Bandung city applies instrument in developing people economy through syariah financing instrument in the form of mudharabah, murabahah instrument, musyarakah instrument, giving training on syariah cooperative, sacrificial saving, holiday saving, service.

Crystal growth, characterization and photo detection properties of 2H–V0.75W0.25Se2 ternary alloy with 1T–VSe2 secondary phase

Transition metal chalcogenides have shown great potential for the applications in high performance optoelectronic devices. Here, we demonstrate for the first time the growth of V0.75W0.25Se2 van der Waals ternary alloy and its application in high performance photodetection. The crystals of V0.75W0.25Se2 were grown by direct vapour transport technique and chemical composition was confirmed by EDAX. The powder XRD results reveal the good crystallinity of grown samples, exhibits hexagonal lattice structure with P63/mmc space group. The XRD pattern also reveals the presence of 1T–VSe2 secondary phase. The SEM and TEM analysis are also carried out for structural analysis. The optical response, studied by photoluminescence spectroscopy discloses the various excitonic mechanisms of V0.75W0.25Se2 ternary alloy. The results of Raman spectroscopy discloses the presence of A1g and E2g modes of vibration and confirms the 2H-poly-type of grown V0.75W0.25Se2 ternary compound. The moderately fast time-resolved photoresponse is demonstrated under 670 nm laser light of power intensity 3 mW cm−2 at 0.3 V bias voltage. The quantitative analysis of performance was carried out from the determined detector parameters such as response time, photo-responsivity, external quantum efficiency and detectivity.

Quantitative criteria to benchmark new and existing bio-inks for cell compatibility

Recent advancements in 3D bioprinting have led to the fabrication of more complex, more precise, and larger printed tissue constructs. As the field continues to advance, it is critical to develop quantitative benchmarks to compare different bio-inks for key cell–biomaterial interactions, including (1) cell sedimentation within the ink cartridge, (2) cell viability during extrusion, and (3) cell viability after ink curing. Here we develop three simple protocols for quantitative analysis of bio-ink performance. These methods are used to benchmark the performance of two commonly used bio-inks, poly(ethylene glycol) diacrylate (PEGDA) and gelatin methacrylate (GelMA), against three formulations of a novel bio-ink, Recombinant-protein Alginate Platform for Injectable Dual-crosslinked ink (RAPID ink). RAPID inks undergo peptide-self-assembly to form weak, shear-thinning gels in the ink cartridge and undergo electrostatic crosslinking with divalent cations during curing. In the one hour cell sedimentation assay, GelMA, the RAPID inks, and PEGDA with xanthan gum prevented appreciable cell sedimentation, while PEGDA alone or PEGDA with alginate experienced significant cell settling. To quantify cell viability during printing, 3T3 fibroblasts were printed at a constant flow rate of 75 μl min−1 and immediately tested for cell membrane integrity. Less than 10% of cells were damaged using the PEGDA and GelMA bio-inks, while less than 4% of cells were damaged using the RAPID inks. Finally, to evaluate cell viability after curing, cells were exposed to ink-specific curing conditions for five minutes and tested for membrane integrity. After exposure to light with photoinitiator at ambient conditions, over 50% of cells near the edges of printed PEGDA and GelMA droplets were damaged. In contrast, fewer than 20% of cells found near the edges of RAPID inks were damaged after a 5 min exposure to curing in a 10 mM CaCl2 solution. As new bio-inks continue to be developed, these protocols offer a convenient means to quantitatively benchmark their performance against existing inks.