Greater Performance Benefits Research Articles

CIGS bifacial solar cells with novel rear architectures: Simulation point of view and the creation of a digital twin

The performance of bifacial Cu(In,Ga)Se2 (CIGS) cells does not yet reach the one of monofacial cells, with standard Mo rear contacts. By exploring optoelectronic simulations, this study addresses the impact of a transparent conducting oxide layer used as rear contact in CIGS solar cells. These simulations, which aim to create a digital twin of bifacial CIGS solar cells, offer insight into the impact of novel rear contact architectures. It was observed that with an indium tin oxide (ITO) rear contact the CIGS cell performance lacks in comparison to a Mo one due to an electrical barrier, under rear side illumination these devices may only reach 3.9 % in conversion efficiency. The implementation of dielectric rear passivation schemes have great performance benefits in cells with Mo rear contacts. Therefore, the same passivation strategy in ITO contacts is discussed and additional novel architectures are proposed, from which a design of alternated lines between dielectric and 15 nm Mo layers on ITO showed promising results. Such rear architectures aim to achieve i) a highly transparent rear contact, ii) an ohmic-like behaviour with CIGS, and iii) a low defective interface with rear passivation. The selenization of the complete 15 nm Mo in the proposed novel architecture during the CIGS growth was considered, resulting in transmittance values above 70 % and, notably, reaching the transparency of bare ITO in the infrared range. Such rear architecture may provide for bifacial CIGS solar cells with conversion efficiency values surpassing 20 and 15 % for front and rear side illumination, respectively, allowing to fully exploit bifaciality.

M1 transcranial direct current stimulation augments laparoscopic surgical skill acquisition

The acquisition of basic surgical skills is a key component of medical education and trainees in laparoscopic surgery typically begin developing their skills using simulation box trainers. However, despite the advantages of simulation surgical training, access can be difficult for many trainees. One technique that has shown promise to enhance the deliberate practice of motor skills is transcranial electric stimulation (tES). The purpose of this study was to assess the impact of transcranial direct current stimulation (tDCS) on training induced improvements and retention of traditional time and kinematic based laparoscopic surgical skill metrics. Forty-nine medical students were randomly allocated to a neurostimulation or sham group and completed 5 training sessions of a bead transfer and threading laparoscopic task. Participants in both the sham and stimulation groups significantly improved their time and kinematic performance on both tasks following training. Although we did find that participants who received M1 tDCS saw greater performance benefits in response to training on a bead transfer task compared to those receiving sham stimulation no effect of neurostimulation was found for the threading task. This finding raises new questions regarding the effect that motor task complexity has on the efficacy of neurostimulation to augment training induced improvement and contributes to a growing body of research investigating the effects of neurostimulation on the sensory-motor performance of laparoscopic surgical skill.

Intensified Training Supersedes the Impact of Heat and/or Altitude for Increasing Performance in Elite Rugby Union Players.

To investigate whether including heat and altitude exposures during an elite team-sport training camp induces similar or greater performance benefits. The study assessed 56 elite male rugby players for maximal oxygen uptake, repeated-sprint cycling, and Yo-Yo intermittent recovery level 2 (Yo-Yo) before and after a 2-week training camp, which included 5 endurance and 5 repeated-sprint cycling sessions in addition to daily rugby training. Players were separated into 4 groups: (1)control (all sessions in temperate conditions at sea level), (2)heat training (endurance sessions in the heat), (3)altitude (repeated-sprint sessions and sleeping in hypoxia), and (4)combined heat and altitude (endurance in the heat, repeated sprints, and sleeping in hypoxia). Training increased maximal oxygen uptake (4% [10%], P = .017), maximal aerobic power (9% [8%], P < .001), and repeated-sprint peak (5% [10%], P = .004) and average power (12% [14%], P < .001) independent of training conditions. Yo-Yo distance increased (16% [17%], P < .001) but not in the altitude group (P = .562). Training in heat lowered core temperature and increased sweat rate during a heat-response test (P < .05). A 2-week intensified training camp improved maximal oxygen uptake, repeated-sprint ability, and aerobic performance in elite rugby players. Adding heat and/or altitude did not further enhance physical performance, and altitude appears to have been detrimental to improving Yo-Yo.

CMOS technology-based energy efficient artificial neural session key synchronization for securing IoT

In this paper, CMOS technology-based neural session key generation is proposed for integration with the Internet-of-Things (IoT) to enhancing security. Recent technological developments in the IoT era enable improved strategies to exacerbate the maintenance of energy efficiency and stability issues. The existing security solutions do not properly address IoT’s security. A small logic area ASIC implementation of a re-keying enabled Triple Layer Vector-Valued Neural Network (TLVVNN) using CMOS architectures with measurements of 65 and 130 nanometers are proposed for integration with IoT. The paper aims to defend IoT devices using TLVVNN synchronization to enhance security. For a 20% weight misalignment in the re-keying phase, the synchronization period may be decreased from 1.25 ms to less than 0.7 ms, according to behavioral simulations. Experiments to verify the proposed technique’s performance are conducted, and the findings demonstrate that the proposed method has greater performance benefits than the existing related techniques.

Chaos-guided neural key coordination for improving security of critical energy infrastructures

In this paper, chaos-guided artificial neural learning-based session key coordination for industrial internet-of-things (IIoT) to enhance the security of critical energy infrastructures (CEI) is proposed. An intruder might pose several security problems since the data are transferred across a public network. Although there have been substantial efforts to solve security problems in the IIoT, the majority of them have relied on traditional methods. A wide range of privacy issues (secrecy, authenticity, and access control) must be addressed to protect IIoT systems against attack. Owing to the unique characteristics of IIoT nodes, existing solutions do not properly address the entire security range of IIoT networks. To deal with this, a chaos-based triple layer vector-valued neural network (TLVVNN) is proposed in this paper. A chaos-based exchange of common seed value for the generation of the identical input vector at both transmitter and receiver is also proposed. This technique has several advantages, including (1) it protects IIoT devices by utilizing TLVVNN synchronization to improve CEI security. (2) Here, artificial neural coordination is utilized for the exchange of neural keys between two IIoT nodes. (3) Using this suggested methodology, chaotic synchronization can be achieved, enabling the chaos-based PRNG seed exchange. (4) Vector-valued inputs and weights are taken into consideration for TLVVNN networks. (5) The deep internal architecture is made up of three hidden layers of the neural network and a vector value as input. As a result, the attacker would have great difficulty interpreting the internal structure. Experiments to verify the performance of the proposed technique are conducted, and the findings demonstrate that the proposed technique has greater performance benefits than the existing related techniques.

Ecological effectiveness of payment for ecosystem services to identify incentive priority areas: Sloping land conversion program in China

Identifying incentive priority areas could improve the sustainability of payment for ecosystem service (PES) schemes. However, the lack of systematic and rigorous assessing ecological effectiveness of PES has resulted in some challenges to identify incentive priority areas in China. This study aimed to assess ecological effectiveness of China’s largest PES scheme, the Sloping Land Conversion Program (SLCP) for identifying the incentive priority areas. Firstly, we used the financial investments as the substitution variable of SLCP. And then the maximum marginal method was adopted to determine the reasonable lag periods of the SLCP`s financial investments. Finally, the panel fixed effect model (with regional dummy variable) was also applied for assessing its ecological effectiveness in different zones. We found that after the implementation of the SLCP, the vegetation improved significantly in Shaanxi province. The average normalized differential vegetation index (NDVI) was 0.831 in 2015, with an increasing rate of 15.097% compared with 2000, although it had some degeneration between 2010 and 2015. It took about four years after investments to realize its greatest performance benefits. The overall financial efficiency showed a pattern of "higher in the north, lower in the south" in Shaanxi province because the afforestation costs in the south were more expensive than that in the north of Shaanxi province. However, some previous key SLCP zones in the north had also been invested excessively, such as Wuqi, Zhidan and Ansai counties. Hence, the government should invest in higher financial efficiency zones based on the incentive priority areas if using the current payment price system.

Carbon Nanotubes as an Ultrafast Emitter with a Narrow Energy Spread at Optical Frequency.

Ultrafast electron pulses, combined with laser-pump and electron-probe technologies, allow ultrafast dynamics to be characterized in materials. However, the pursuit of simultaneous ultimate spatial and temporal resolution of microscopy and spectroscopy is largely subdued by the low monochromaticity of the electron pulses and their poor phase synchronization to the optical excitation pulses. Field-driven photoemission from metal tips provides high light-phase synchronization, but suffers large electron energy spreads (3-100 eV) as driven by a long wavelength laser (>800 nm). Here, ultrafast electron emission from carbon nanotubes (≈1 nm radius) excited by a 410 nm femtosecond laser is realized in the field-driven regime. In addition, the emitted electrons have great monochromaticity with energy spread as low as 0.25 eV. This great performance benefits from the extraordinarily high field enhancement and great stability of carbon nanotubes, superior to metal tips. The new nanotube-based ultrafast electron source opens exciting prospects for extending current characterization to sub-femtosecond temporal resolution as well as sub-nanometer spatial resolution.

Lowering the cost of carbon fiber

Carbon fiber offers a great many performance and lightweighting benefits for composites. Lower cost manufacture and increased use of recycled material now promise to widen the range of applications that could benefit from its properties.

Innovation and firm growth: Does firm age play a role?

This paper explores the relationship between innovation and firm growth for firms of different ages. We hypothesize that young firms undertake riskier innovation activities which may have greater performance benefits (if successful), or greater losses (if unsuccessful). Using an extensive Spanish Community Innovation Survey sample for the period 2004–2012, we apply panel quantile regressions to study the effect of R&D activities on firm growth (i.e. sales growth, productivity growth and employment growth). Our results show that young firms face larger performance benefits from R&D at the upper quantiles of the growth rate distribution, but face larger decline at the lower quantiles. R&D investment by young firms therefore appears to significantly riskier than R&D investment by more mature firms, which suggests some policy implications.

Smart Grid ICT Research Lines out of the European Project INTEGRIS

The Smart Grid is at the same time a part of the Internet of Things and an example of a cyber-physical system where the physical power grid is surrounded by many intelligent and communication devices that allow for an enhanced management of the power network itself. The Smart Grid may bring great performance benefits to the society in terms of enabling the massive introduction of renewable energy sources in the power grid, the reduction of carbon emissions and improved sustainability among others. However, it may also bring big computer networking challenges to achieve the needed high reliability and low latency and even risks in terms of cybersecurity since it opens the power system to at least the same threats faced by the Internet. In fact, it is reasonable to think that the vulnerabilities will be still larger, considering the novel, heterogeneous and distributed nature of the Smart Grid. Furthermore, cybersecurity in Smart Grids is essential for the survival and feasibility of this electricity concept, thus making the risks still more relevant. Such ICT systems and computer networks supporting the Smart Grid concept need to be very efficient and to comply with very stringent requirements, at least for some of the services to be provided. They also need to efficiently integrate and manage in a single network a vast array of technologies among which diverse link layer technologies, meshed and non-meshed Ethernet networks, different cybersecurity protocols, networking at different layers, cognitive systems and storage and replication of data. The objective is to provide a system capable of providing adequate service to the wide array of applications foreseen for the Smart Grid but the complexity of the problem is really impressive and it is not possible to focus all of its aspects in a single paper or even project. The present paper presents these requirements, the solutions and results developed and tested in the FP7 European Project INTEGRIS as well as the future challenges and research lines identified as a result of the project and some prospective solutions.

Estimation of the Number of Distinct Values over Data Stream Based on Compound Sliding Window

Estimating the number of distinct values in a data stream is a vital problem with many applications such as complex join query over multiple data streams. In this paper, we focus on the continuous and periodic distinct values estimation over sliding windows. We propose a compound sliding window model to compute the distinct values over basic sliding windows in an incremental way. LDV, HDV and AHDV are the three algorithms that are based on compound sliding windows. The basic idea behind the compound sliding windows is to organize the basic windows into a Hash table according to distinct values. Whenever a new data arrives at the data stream, it is inserted into a basic window. Once the basic window is full, a scan using distinct values is executed and the distinct values number is updated incrementally. Theoretical analysis and experiment results show that the distinct values estimation algorithms based on compound sliding windows have a great performance benefits.

Field-Trial of an All-Optical PSK Regenerator/Multicaster in a 40 Gbit/s, 38 Channel DWDM Transmission Experiment

The performance of future ultra-long haul communication systems exploiting phase-encoded signals is likely to be compromised by noise generated during signal transmission. One potential way to mitigate such noise is to use Phase Sensitive Amplifiers (PSAs) which have been demonstrated to help remove phase as well as amplitude noise from phase-encoded signals. Recently, we showed that a PSA-based signal regenerator based on degenerate four-wave mixing can be implemented in a network-compatible manner in which only the (noisy) signal is present at the device input (black-box operation). The developed regenerator was also able to perform simultaneous wavelength conversion and multicasting, details/analysis of which are presented herein. However, this scheme was tested only with artificial noise generated in the laboratory and with the regenerator placed in front of the receiver, rather than in-line where even greater performance benefits are to be expected. Here, we address both theoretically and experimentally the important issue of how such a regenerator, operating for convenience in a multicasting mode, performs as an in-line device in an installed transmission fiber link. We also investigate the dispersion tolerance of the approach.

Performance on a neurocognitive measure of alerting differentiates ADHD combined and inattentive subtypes: A preliminary report

The performance of 16 attention-deficit hyperactivity disorder (ADHD)/C, 26 ADHD/IA, and 24 control children was compared using a computer reaction time task designed to measure the effects of Posner's orienting, conflict and alerting attentional systems. No group differences in orienting or conflict were found. In contrast, children with ADHD/IA showed stronger alerting effects than those with ADHD/C, as indicated by relatively greater performance benefits following a warning cue. Although neither ADHD group differed significantly from controls on alerting, effect size comparisons indicated that children with ADHD/IA showed a somewhat larger ( d = .57) and children with ADHD/C a somewhat smaller ( d = .44) alerting effect relative to control children. The results are among the first to document unique patterns of attentional capacity for ADHD subtypes.

Accelerating peer-to-peer networks for video streaming using multipoint-to-point communication

Existing transport layer protocols such as TCP and UDP are designed specifically for point-to-point communication. The increased popularity of peer-to-peer networking has brought changes in the Internet that provided users with potentially multiple replicated sources for content retrieval. However, applications that leverage such parallelism have thus far been limited to non-real-time file downloads. In this article we consider the problem of multipoint-to-point video streaming over peer-to-peer networks. We present a transport layer protocol called R/sup 2/CP that effectively enables real-time multipoint-to-point video streaming. R/sup 2/CP is a receiver-driven multistate transport protocol. It requires no coordination between multiple sources, accommodates flexible application layer reliability semantics, uses TCP-friendly congestion control, and delivers to the video stream the aggregate of the bandwidths available on the individual paths. Simulation results show great performance benefits using R/sup 2/CP in peer-to-peer networks.

Using Apples to Schedule Simple SARA on the Computational Grid

Computational Grids, composed of distributed and often heterogeneous computing resources, have become the platform of choice for many performance-challenged applications. Proof-of-concept implementations have demonstrated that both Grids and clustered environments have the potential to provide great performance benefits to distributed resource-intensive applications. However, at the present time, careful staging, scheduling, and/or reservation of resources is essential in order for applications to achieve performance in Grid environments. If Computational Grids and shared computational clusters are to achieve their full potential, it must be possible for users to achieve application performance at any given time, and when other users are present in the system. In this paper, we describe the initial development of an AppLeS (application-level scheduler) for the resource selection portion of the Synthetic Aperture Radar Atlas (SARA) application, developed at the Jet Propulsion Laboratory (JPL) and the San Diego Supercomputer Center (SDSC). We demonstrate the effectiveness of application scheduling for distributed data applications such as SARA by providing a performance-efficient strategy for retrieving SARA data files in everyday, multiple-user Grid environments.

A status report on research in transparent informed prefetching

This paper focuses on extending the power of caching and prefetching to reduce file read latencies by exploiting application level hints about future I/O accesses. We argue that systems that disclose high-level knowledge can transfer optimization information across module boundaries in a manner consistent with sound software engineering principles. Such Transparent Informed Prefetching (TIP) systems provide a technique for converting the high throughput of new technologies such as disk arrays and log-structured file systems into low latency for applications. Our preliminary experiments show that even without a high-throughput I/O subsystem TIP yields reduced execution time of up to 30% for applications obtaining data from a remote file server and up to 13% for applications obtaining data from a single local disk. These experiments indicate that greater performance benefits will be available when TIP is integrated with low level resource management policies and highly parallel I/O subsystems such as disk arrays.

Operational Benefits and Design Approaches for Combining JTIDS and GPS Navigation

This paper describes the Joint Tactical Information Distribution System (JTIDS) Navigation Function and the Global Positioning System (GPS), emphasizing their technical similarities and differences. Based on these, the paper discusses the operational benefits, performance, and design approaches for combining the navigational and time data from these two systems. Both JTIDS and GPS are time synchronous, spread spectrum systems which provide high accuracy navigation data through the use of time-of-arrival measurements and pseudo-ranging techniques. Both are subject to Geometric Dilution of Precision (GDOP) effects, though under different conditions; and both are highly resistent to interference, though to different degrees. JTIDS is more a tactical or local system, while GPS is global in nature. Exchanging data between the two systems, under certain constraints, therefore has the potential of great performance and operational benefits with respect to system availability, under a variety of operational scenarios and interference conditions. These benefits and proposed methods for combining the data from the two systems are described in the paper.