Dual-fisheye lens stitching for 360-degree imaging

Dual-fisheye lens cameras have been increasingly used for 360-degree immersive imaging. However, the limited overlapping field of views and misalignment between the two lenses give rise to visible discontinuities in the stitching boundaries. This paper introduces a novel method for dual-fisheye camera stitching that adaptively minimizes the discontinuities in the overlapping regions to generate full spherical 360-degree images. Results show that this approach can produce good quality stitched images for Samsung Gear 360 -- a dual-fisheye camera, even with hard-to-stitch objects in the stitching borders.Comment: ICASSP 17 preprint, Proc. of the 42nd IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), New Orleans, USA, March 201

Municipal wastewater treatment with pond technology : historical review and future outlook

Facing an unprecedented population growth, it is difficult to overstress the assets for wastewater treatment of waste stabilization ponds (WSPs), i.e. high removal efficiency, simplicity, and low cost, which have been recognized by numerous scientists and operators. However, stricter discharge standards, changes in wastewater compounds, high emissions of greenhouse gases, and elevated land prices have led to their replacements in many places. This review aims at delivering a comprehensive overview of the historical development and current state of WSPs, and providing further insights to deal with their limitations in the future. The 21st century is witnessing changes in the way of approaching conventional problems in pond technology, in which WSPs should no longer be considered as a low treatment technology. Advanced models and technologies have been integrated for better design, control, and management. The roles of algae, which have been crucial as solar-powered aeration, will continue being a key solution. Yet, the separation of suspended algae to avoid deterioration of the effluent remains a major challenge in WSPs while in the case of high algal rate pond, further research is needed to maximize algal growth yield, select proper strains, and optimize harvesting methods to put algal biomass production in practice. Significant gaps need to be filled in understanding mechanisms of greenhouse gas emission, climate change mitigation, pond ecosystem services, and the fate and toxicity of emerging contaminants. From these insights, adaptation strategies are developed to deal with new opportunities and future challenges

Opportunities and challenges for the sustainability of lakes and reservoirs in relation to the sustainable development goals (SDGs)

Emerging global threats, such as biological invasions, climate change, land use intensification, and water depletion, endanger the sustainable future of lakes and reservoirs. To deal with these threats, a multidimensional view on the protection and exploitation of lakes and reservoirs is needed. The holistic approach needs to contain not just the development of economy and society but also take into account the negative impacts of this growth on the environment, from that, the balance between the three dimensions can be sustained to reach a sustainable future. As such, this paper provides a comprehensive review on future opportunities and challenges for the sustainable development of lakes and reservoirs via a critical analysis on their contribution to individual and subsets of the Sustainable Development Goals (SDGs). Currently, lakes and reservoirs are key freshwater resources. They play crucial roles in human societies for drinking water provision, food production (via fisheries, aquaculture, and the irrigation of agricultural lands), recreation, energy provision (via hydropower dams), wastewater treatment, and flood and drought control. Because of the (mostly) recent intensive exploitations, many lakes and reservoirs are severely deteriorated. In recent years, physical (habitat) degradation has become very important while eutrophication remains the main issue for many lakes and ponds worldwide. Besides constant threats from anthropogenic activities, such as urbanization, industry, aquaculture, and watercourse alterations, climate change and emerging contaminants, such as microplastics and antimicrobial resistance, can generate a global problem for the sustainability of lakes and reservoirs. In relation to the SDGs, the actions for achieving the sustainability of lakes and reservoirs have positive links with the SDGs related to environmental dimensions (Goals 6, 13, 14, and 15) as they are mutually reinforcing each other. On the other hand, these actions have direct potential conflicts with the SDGs related to social and economic dimensions (Goals 1, 2, 3 and 8). From these interlinkages, we propose 22 indicators that can be used by decision makers for monitoring and assessing the sustainable development of lakes and reservoirs

Secular non-secular master equation

Redfield non-secular master equation governing relaxation of a spin in weak interaction with a thermal bath is studied. Using the fact that the relaxation follows the exponential law, we prove that in most cases the semi-secular approximation is sufficient to find the system relaxation rate. Based on this, a "secular" form of the non-secular master equation is for the first time developed which correctly set up one of most fundamental equations in relaxation investigation. This key secular form allows us to derive a general formula of the phonon-induced quantum tunneling rate which is valid for the entire range of temperature regardless of the basis. In incoherent tunneling regime and localized basis, this formula reduces to the ubiquitous incoherent tunneling rate. Meanwhile, in eigenstates basis, this tunneling rate is demonstrated to be equal to zero. From this secular form, we end the controversy surrounding the selection of basis for the secular approximation by figuring out the conditions for using this approximation in localized and eigenstates basis. Particularly, secular approximation in localized basis is justified in the regime of high temperature and small tunnel splittings. In contrast, a large ground doublet's tunnel splitting is required for the secular approximation in eigenstates basis. With these findings, this research lays a sound foundation for any treatments of the spin-phonon relaxation under any conditions provided that the non-secular master equation is relevant.Comment: 9 pages, 0 figure

Surgical and interventional treatments of congenital heart diseases in Da Nang Hospital, Vietnam

Background We conducted this study to explore the trend and the percentage of congenital heart disease (CHD) visited Da Nang hospital from 2010 to 2015. Another objective was to develop criteria that help to classify atrial septal defect (ASD) patients as patients suitable for surgical or transcatheter closure procedures. In addition, we compared the effectiveness and safety of surgical and transcatheter methods for ASD patients. Methods The data involved the information of all CHD patients treated in Da Nang hospital from January 2010 to December 2015. The selection involved all the patient cases treated with surgical and transcatheter closure procedures. All cases without clear data on transcatheter or surgical intervention were excluded. A total of 1220 cases were eligible for the study. All the data collected was based on paper medical records. Results A total of 1220 CHD patients were recruited in the study, of which 58.9% were women, and 41.1% were men. Most of CHD patients belonged to the age group of 0-9 (70.2%). A total of 266 ASD patients were included in the study, of which 186 women (69.9%) and 80 men (30.1%). The distribution of male and female proportions was relatively similar between years. After adjusting for sufficient rim among ASD patients, the cut-off point of the length of the defect for an operation would be 34.1 mm, while the width of the defect would be 33.3 mm. Both surgical and transcatheter closure procedures were safe for ASD patients. The total price for a case of ASD operation was significantly higher than that for a case of transcatheter closure. Conclusion We suggest that Vietnam should continue investing more in early diagnosis and treatment for CHD patients. Hospital in Vietnam should update the technology and find transcatheter closure devices with reasonable prices so that more ASD patients would afford to use

OPTIMIZATION OF OPERATING PARAMETERS IN LNG AP-X PROCESS

Natural gas (NG) has been known as the cleanest fossil fuel since it releases low level of harmful products when being burnt. Natural gas can be transported either in pipelines or in liquefied natural gas (LNG) carriers. In LNG carriers, LNG is liquefied to the temperature of -162 degree Celsius at atmospheric pressure so that its volume can be reduced up to 600 times. There are a lot of techniques available for liquefying natural gas. The most potential technique developed by APCI is AP-X process. This is an improvement from C3MR process by using nitrogen in the subcooling loop at the end of the process. It is very beneficial to know the optimum refrigerant flow rate for the purpose of saving energy consumed in the process. Moreover, the operating refrigerant flow rate also is optimized with subject to the compensation with the compressor load and the energy efficiency. HYSYS software is utilized to model the nitrogen loop of AP-X process. LNG flow rate, compressor load and heat duties exchanged are taken from HYSYS model. In this study, the optimum pure nitrogen flow rate was found to be at around 2500 kg/h. Besides, the flow rate for 5% methane mixed refrigerant is 2375 kg/hr, so that the process is most beneficial in term of revenue as well as energy efficiency. The optimum capacity of LNG plant using AP-X process is found at 9.1 MTPA, according to around 13.5% increase in train capacity compared with the current operating train capacity in Qatar