A Survey of Positioning Systems Using Visible LED Lights

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As Global Positioning System (GPS) cannot provide satisfying performance in indoor environments, indoor positioning technology, which utilizes indoor wireless signals instead of GPS signals, has grown rapidly in recent years. Meanwhile, visible light communication (VLC) using light devices such as light emitting diodes (LEDs) has been deemed to be a promising candidate in the heterogeneous wireless networks that may collaborate with radio frequencies (RF) wireless networks. In particular, light-fidelity has a great potential for deployment in future indoor environments because of its high throughput and security advantages. This paper provides a comprehensive study of a novel positioning technology based on visible white LED lights, which has attracted much attention from both academia and industry. The essential characteristics and principles of this system are deeply discussed, and relevant positioning algorithms and designs are classified and elaborated. This paper undertakes a thorough investigation into current LED-based indoor positioning systems and compares their performance through many aspects, such as test environment, accuracy, and cost. It presents indoor hybrid positioning systems among VLC and other systems (e.g., inertial sensors and RF systems). We also review and classify outdoor VLC positioning applications for the first time. Finally, this paper surveys major advances as well as open issues, challenges, and future research directions in VLC positioning systems.Peer reviewe

Review of the advances in solar-assisted air source heat pumps for the domestic sector

Solar assisted air source heat pump shows great potential as a promising energy-saving heating technology, which integrates solar collector and air source heat pump. It is widely considered for supplying hot water, space heating and/or space cooling in the domestic sector. The performance of solar assisted air source heat pumps can be evaluated in system level by parameters such as coefficient of performance, seasonal performance factor, energy consumption, solar fraction as well as initial and operating costs, and in component level by parameters such as efficiencies of solar collection and thermal energy storage. Their performances are affected by many factors such as system configuration, components size, working fluid, working conditions and weather conditions. This paper presents a comprehensive review on the recent advances in solar assisted air source heat pump for the domestic sector in terms of system configuration, solar collectors, thermal energy storage, defrosting method and the perspective areas of further investigations. The results of this review confirm that research is still required to improve the performance of such a combined system and reduce initial cost compared with existing heating systems based on hydrocarbon combustion. The information presented in this paper is beneficial to the researchers, small and medium-sized enterprises supplying renewable energy system technologies, heating engineers and service workers, energy policy and decision makers, environmental activists and communities

Electrical and Structural Analysis of CNT-Metal Contacts in Via Interconnects

Vertically aligned carbon nanotubes grown by plasmaenhanced chemical vapor deposition offer a potentially suitable material for via interconnects in next-generation integrated circuits. Key performance-limiting factors include high contact resistance and low carbon nanotube packing density, which fall short of meeting the requirements delineated in the ITRS roadmap for interconnects. For individual carbon nanotube s, contact resistance is a major performance hurdle since it is the dominant component of carbon nanotube interconnect resistance, even in the case of vertically aligned carbon nanotube arrays. In this study, we correlate the carbon nanotube-metal interface nanostructure to their electrical properties in order to elucidate growth parameters that can lead to high density and low contact resistance and resistivity

Methylenetetrahydrofolate reductase (MTHFR) gene polymorphism is associated with abortion in Chinese Holstein cows

Polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene are associated with abortion, early embryo loss and recurrent spontaneous abortion in human. However, information on the association between MTHFR polymorphism and cow abortion is scarce. In the present study, the effects of MTHFR polymorphism on cow abortion were investigated. The PCR-SSCP and DNA sequencing were applied to detect the polymorphisms in exon 4 and 7 of MTHFR gene in a total of 569 Chinese Holstein cattles. The homocysteine levels during various periods of pregnancy were detected by HPLC. The results show that 8137C/T SNP was identified in exon 7 of MTHFR, but no polymorphism was detected in exon 4. Association analysis revealed that the 8137C/T mutation was significantly associated with cow abortion (P = 0.0002). Regarding relative risk of incidence, cows with CT genotype showed greater relative risk than those with CC (OR = 2.05, 95% CI = 1.40 to 3.00). The blood homocysteine levels of individuals with CT genotype were significantly higher than those with CC genotype during the first 6 months of pregnancy and in non-pregnant cows (P < 0.05). In conclusion, MTHFR may be a beneficial candidate gene to control cow abortion.Key words: Methylenetetrahydrofolate reductase (MTHFR), abortion, Chinese Holstein cattle, SN

Analysis of operation performance of three indirect expansion solar assisted air source heat pumps for domestic heating

To achieve the goal set for net-zero emissions of greenhouse gases in the UK by 2050, the domestic heating must be decarbonised. Solar assisted air source heat pumps, integrating solar collector, thermal energy storage tank and heat pump, offers a promising alternative application under the UK weather conditions. Literature review shows that investigations of solar assisted air source heat pumps in the regions like the UK are still insufficient. The serial, parallel and dual-source indirect expansion solar assisted air source heat pumps are modelled and simulated under the weather conditions in London using TRNSYS to investigate the operation performance over a typical year. These three heat pumps are applied to provide space heating and hot water of 300 L per day for a typical single-family house. The simulation results show comparisons of the three systems. The serial type heat pump shows the highest seasonal performance factor of 5.5, but requiring the largest sizes of the solar collector and thermal energy storage tank. The dual-source and parallel type heat pumps show slightly lower seasonal performance factors of 4.4 and 4.5, respectively, requiring smaller sizes of solar collector and thermal energy storage tank. Furthermore, the results show that the air source part contributes to an important proportion of the heat provision and stable operation of the systems. The yearly seasonal performance factor higher than 4.4 achievable by the three heat pumps suggests that they are potentially applied in the regions with relatively lower solar irradiance. The economic analyses indicate that the parallel and dual-source type heat pumps provide good alternatives to replacing the gas-boiler heating system

A coupled modeling framework for sustainable watershed management in transboundary river basins

There is a growing recognition among water resource managers that sustainable watershed management needs to not only account for the diverse ways humans benefit from the environment, but also incorporate the impact of human actions on the natural system. Coupled natural– human system modeling through explicit modeling of both natural and human behavior can help reveal the reciprocal interactions and co-evolution of the natural and human systems. This study develops a spatially scalable, generalized agent-based modeling (ABM) framework consisting of a process-based semi-distributed hydrologic model (SWAT) and a decentralized water system model to simulate the impacts of water resource management decisions that affect the food–water–energy–environment (FWEE) nexus at a watershed scale. Agents within a river basin are geographically delineated based on both political and watershed boundaries and represent key stakeholders of ecosystem services. Agents decide about the priority across three primary water uses: food production, hydropower generation and ecosystem health within their geographical domains. Agents interact with the environment (streamflow) through the SWAT model and interact with other agents through a parameter representing willingness to cooperate. The innovative twoway coupling between the water system model and SWAT enables this framework to fully explore the feedback of human decisions on the environmental dynamics and vice versa. To support non-technical stakeholder interactions, a web-based user interface has been developed that allows for role-play and participatory modeling. The generalized ABM framework is also tested in two key transboundary river basins, the Mekong River basin in Southeast Asia and the Niger River basin in West Africa, where water uses for ecosystem health compete with growing human demands on food and energy resources. We present modeling results for crop production, energy generation and violation of ecohydrological indicators at both the agent and basin-wide levels to shed light on holistic FWEE management policies in these two basins

The swap operation in the two-qubit Heisenberg XXZ model-effects of anisotropy and magnetic field

In this paper we study the swap operation in a two-qubit anisotropic XXZ model in the presence of an inhomogeneous magnetic field. We establish the range of anisotropic parameter within which the swap operation is feasible. The swap errors caused by the inhomogeneous field are evaluated

Asymmetric bagging and feature selection for activities prediction of drug molecules

<p>Abstract</p> <p>Background</p> <p>Activities of drug molecules can be predicted by QSAR (quantitative structure activity relationship) models, which overcomes the disadvantages of high cost and long cycle by employing the traditional experimental method. With the fact that the number of drug molecules with positive activity is rather fewer than that of negatives, it is important to predict molecular activities considering such an unbalanced situation.</p> <p>Results</p> <p>Here, asymmetric bagging and feature selection are introduced into the problem and asymmetric bagging of support vector machines (asBagging) is proposed on predicting drug activities to treat the unbalanced problem. At the same time, the features extracted from the structures of drug molecules affect prediction accuracy of QSAR models. Therefore, a novel algorithm named PRIFEAB is proposed, which applies an embedded feature selection method to remove redundant and irrelevant features for asBagging. Numerical experimental results on a data set of molecular activities show that asBagging improve the AUC and sensitivity values of molecular activities and PRIFEAB with feature selection further helps to improve the prediction ability.</p> <p>Conclusion</p> <p>Asymmetric bagging can help to improve prediction accuracy of activities of drug molecules, which can be furthermore improved by performing feature selection to select relevant features from the drug molecules data sets.</p