On-site measurement and numerical investigation of thermal environment with different air distribution systems in ice arenas

It is important to strictly maintain the indoor thermal environment in ice arenas which have very different features to other commercial buildings. Separated air distribution system is widely used to create a dry and cold environment near the ice and a comfortable environment in the view stand. The warm and humid air from the view stand may lead to uneven temperature and humidity distribution in the rink, leading to extra energy consumption, even fog and frost on the ice. Unreasonable air supply in the ice rink zone will also make the spectators feel too cold and uncomfortable. Jet ventilation system is the most extensively used system in the ice rink zone. An innovative ground displacement ventilation system is proposed in the National Aquatics Centre, which will serve as the venue for the curling competition in the 2022 Beijing Winter Olympics. On-site measurement in the arena is carried out and computational fluid dynamics (CFD) simulation method is adopted in the present research. Measured thermal environment above the ice with different ventilation systems are compared and analysed. Result shows that the displacement ventilation system features a more obvious vertical stratification than jet ventilation system in this kind of large space buildings, and thus is more energy-efficient. A CFD model of the ice cube is setup and verified by measured data. The thermal environment in the ice rink with displacement ventilation under extreme condition is studied using the simulation method. The temperature and humidity in the ice field increases by 10.1 °C, 4.5 g/kg without air supply in the view stand, proving that the spectators in the view stand have a great impact on the thermal environment in the ice field.

Remote Sensing of the Polar Ice Zones with HF Radar

Radars operating in the HF band are widely used for over-the-horizon remote sensing of ocean surface conditions, ionospheric studies and the monitoring of ship and aircraft traffic. Several hundreds of such radars are in operation, yet only a handful of experiments have been conducted to assess the prospect of utilizing this technology for the remote sensing of sea ice. Even then, the measurements carried out have addressed only the most basic questions: is there ice present, and can we measure its drift? Recently the theory that describes HF scattering from the dynamic sea surface was extended to handle situations where an ice cover is present. With this new tool, it becomes feasible to interpret the corresponding radar echoes in terms of the structural, mechanical, and electrical properties of the ice field. In this paper we look briefly at ice sensing from space-borne sensors before showing how the persistent and synoptic wide area surveillance capabilities of HF radar offer an alternative. The dispersion relations of different forms of sea ice are examined and used in a modified implementation of the electromagnetic scattering theory employed in HF radar oceanography to compute the corresponding radar signatures. Previous and present-day HF radar deployments at high latitudes are reviewed, noting the physical and technical challenges that confront the implementation of an operational HF radar in its ice monitoring capability.

Lateral variation in slab window viscosity inferred from global navigation satellite system (GNSS)–observed uplift due to recent mass loss at Patagonia ice fields

The geographic coincidence of the Chile Ridge slab window and the Patagonia ice fields offers a unique opportunity for assessing the effects of slab window rheology on glacial isostatic adjustment (GIA). Mass loss of these ice fields since the Little Ice Age causes rapid but variable crustal uplift, 12–24 mm/yr around the North Patagonia ice field, increasing to a maximum of 41 mm/yr around the South Patagonia ice field, as determined from newly collected or processed geodetic data. We used these observational constraints in a three-dimensional Maxwell viscoelastic finite element model of GIA response above both the subducting slab and slab window in which the upper-mantle viscosity was parameterized to be uniform with depth. We found that the viscosity of the northern part of the slab window, ~2 × 1018 Pa·s, is lower than that of the southern part by approximately an order of magnitude. We propose that this along-strike viscosity contrast is due to late Cenozoic ridge subduction beneath the northern part of the slab window, which increases asthenospheric temperature and reduces viscosity.

The exploration of wave processes in the Arctics geological layers in the presence of the ice field.

The Arctic shelf zone is a very important region in our country due to the huge amounts of hydrocarbons, located there. The exploration of this region is difficult because of the presence of lots of various ice constructions, in particular, ice fields. While carrying out the seismic prospecting works, the reflected waves from the ice field contribute much to the seismograms. It sufficiently complicates the process of further interpretation of the seismograms. Only a few works are devoted to modelling the seismic waves spread through the geological layers of the Arctics in the presence of an ice field as this theme is rather new and needs deeper investigation. In this work we present the results of the investigation of the seismic waves spread in models with an ice field for the 3D case using the grid-characteristic method. The modelling results (wave fields of the velocity distribution and seismograms) allow to identify the reflected waves from the ice field from other waves. In addition, we carried out the comparative analysis of the wave fields and seismograms for the 2D model with an ice field on the surface of the calculated area for the problem description from the work of other authors. The results demonstrate a good qualitative coincidence under different approaches to the solution of the problem.

On the question of the use of GTZA with direct transmission on linear nuclear icebreakers

В статье проведено краткое сопоставление основных характеристик гребных электрических установок, традиционно применяемых на отечественных атомных ледоколах, и судовых реверсивных главных турбозубчатых агрегатов. В работе показано, что естественные механические характеристики турбозубчатых агрегатов позволяют удовлетворить основные требования к работе ледокольных двигательно-движительных установок без построения сложных систем, которые имеют место в гребных электрических установках для получения искусственных механических характеристик электродвигателей с организацией диапазонов работы с постоянством мощности, диапазонов работы с ограничением крутящих моментов, а также – решения задачи утилизации рекуперируемой энергии при реверсах гребных винтов. В аналитическом разделе статьи показано, что в предложенной установке с прямой передачей мощности на гребной винт задача поддержания постоянства мощности энергоустановки на номинальных эксплуатационных режимах, задача обеспечения работы установки при движении в ледовом поле, когда требуется обеспечить «фрезерование» льда, чтобы исключить заклинивание и поломку гребного винта с ограничением максимальных перегрузочных крутящих моментов на гребном валу, задача реверсирования гребного винта решаются за счет использования естественных механических характеристик реверсивного турбозубчатого агрегата. При создании перспективных тяжелых атомных ледоколов рекомендуется применение более простой, надежной и экономичной схемы построения ледокольных главных энергетических установок на основе современных конструкций турборедукторных тепловых двигателей для привода гребных винтов. The article presents a brief comparison of the main characteristics of rowing electric installations, traditionally used on domestic nuclear icebreakers, and ship reversible main turbine with gearbox. The paper shows that the natural mechanical characteristics of turbine with gearbox allow us to meet the basic requirements for the operation of icebreaking propulsion systems without building complex systems that take place in rowing electric installations to obtain artificial mechanical characteristics of electric motors with the organization of ranges of operation with constant power, ranges of operation with limited torques, as well as solving the problem of utilization of recovered energy during propeller reversals. The analytical section of the article shows that in the proposed installation with direct power transmission to the propeller, the task of maintaining the constancy of the power plant's power at nominal operating conditions, the task of ensuring the operation of the installation when moving in an ice field, when it is necessary to ensure "ice milling" to eliminate jamming and breakage of the propeller with limiting the maximum overload torques on the propeller shaft, the task of reversing the propeller is solved by using the natural mechanical characteristics of a reversible turbine with gearbox. When creating promising heavy nuclear icebreakers, it is recommended to use a simpler, reliable and economical scheme for building icebreaking main power plants based on modern designs of turbine with gearbox as heat engines for driving propellers.

ICE Offices and Immigration Courts: Accompaniment in Zones of Illegality

In this article, I examine two sites of the contemporary illegality industry in the United States: the ICE Field Office and the Immigration Court. Drawing on ongoing ethnographic engagement, including accompaniment and observations in a regional Immigration and Customs Enforcement (ICE) Field Office and an Executive Office of Immigration Reform (EOIR) Court, I trace how human interactions and social relations in each of these bureaucratic sites structure and reinforce conditions of precarity, insecurity, and marginality among undocumented and asylum seeking people in the United States. In both sites, the enforcement power of the state is visible through the configurations of bureaucratic processes and the structures of interactions between migrants and federal government officials. Examining these two sites from the vantage point of engaged ethnography, I illustrate how routine, bureaucratic encounters (re)produce illegality and exclusion by enacting violence against migrants through the powers of surveillance and administrative monitoring, and the threat of deportation and family separation. I also reflect on the political potential that emerges through activist anthropology and accompaniment with migrants in sites of state violence.

Sub-kilometre scale distribution of snow depth on Arctic sea ice from Soviet drifting stations

The sub-kilometre scale distribution of snow depth on Arctic sea ice impacts atmosphere-ice fluxes of heat and light, and is of importance for satellite estimates of sea ice thickness from both radar and lidar altimeters. While information about the mean of this distribution is increasingly available from modelling and remote sensing, the full distribution cannot yet be resolved. We analyse 33539 snow depth measurements from 499 transects taken at Soviet drifting stations between 1955 and 1991 and derive a simple statistical distribution for snow depth over multi-year ice as a function of only the mean snow depth. We then evaluate this snow depth distribution against snow depth transects that span first-year ice to multiyear ice from the MOSAiC, SHEBA and AMSR-Ice field campaigns. Because the distribution can be generated using only the mean snow depth, it can be used in the downscaling of several existing snow depth products for use in flux modelling and altimetry studies.