bluuebunny/crossref_metadata_2025 huggingface dataset:
High performance CuO@brass supercapacitor electrodes through surface activation
Authors: Kumar Ambrish , Thomas Arpit , Garg Mayank , Perumal Gopinath , Grewal Harpreet S. , Arora Harpreet S.
Published: March 2021

The 3-dimensional hierarchical nano-porous copper oxide structure developed using thermo-mechanical processing and selective dealloying demonstrated excellent performance as a supercapacitor electrode.
Indium selenide for Q-switched pulse generation in a mid-infrared fiber laser
Authors: Chen Tenghui , Li Zhongjun , Zhang Chunxiang , Wang Zhenhong , Luo Mulin , Zhang Yuan , Wang Yachao , Xiao Quanlan , Zhang Han , Liu Jun
Published: March 2021

A novel broadband two-dimensional material, indium selenide (InSe), is prepared and characterized in the mid-infrared wavelength region. Stable Q-switching pulses are obtained from a 2.8 μm Er-ZBLAN fiber laser based on the InSe saturable absorber.
Prolonged Positional Downbeat Nystagmus in Benign Paroxysmal Positional Vertigo: A Case Report and Literature Review
Authors: Lee Hyun-Jin , Ahn Seong Ki , Yim Chae Dong , Kim Seong Dong , Hur Dong Gu
Published: March 2021

Purpose

This study aimed to report an unusual case of benign paroxysmal positional vertigo (BPPV), who showed prolonged positional downbeat nystagmus without latency and was diagnosed with cupulolithiasis of the anterior canal (AC). We compared this case with one of typical AC-BPPV, and possible mechanisms underlying the atypical characteristics were discussed.

Method

Two patients diagnosed with AC-BPPV were reported. Positional testing using video-oculography goggles was performed, and outcomes were measured via medical records and analysis of videos of the nystagmus.

Results

Downbeat nystagmus was observed in the contralateral Dix–Hallpike test in both cases. The torsional component was subtle or absent, but motion was induced toward the affected ear. The two cases differed in latency and duration of vertigo, as well as habituation. The patient with atypical nystagmus showed little or no latency and longer duration. Moreover, there was no habituation on repeated tests. The nystagmus showed several differences from that of typical AC-BPPV.

Conclusions

Based on our case, AC-BPPV may induce various unusual clinical manifestations of nystagmus. Accurate diagnosis requires careful consideration of the patient's symptoms and the characteristics of the nystagmus.

Supplemental Material

https://doi.org/10.23641/asha.14265356
Materials Matter: An Exploration of Text Complexity and Its Effects on Middle School Readers' Comprehension Processing
Authors: Dahl Amanda C. , Carlson Sarah E. , Renken Maggie , McCarthy Kathryn S. , Reynolds Erin
Published: March 2021

Purpose

Complex features of science texts present idiosyncratic challenges for middle grade readers, especially in a post–Common Core educational world where students' learning is dependent on understanding informational text. The primary aim of this study was to explore how middle school readers process science texts and whether such comprehension processes differed due to features of complexity in two science texts.

Method

Thirty 7th grade students read two science texts with different profiles of text complexity in a think-aloud task. Think-aloud protocols were coded for six comprehension processes: connecting inferences, elaborative inferences, evaluative comments, metacognitive comments, and associations. We analyzed the quantity and type of comprehension processes generated across both texts in order to explore how features of text complexity contributed to the comprehension processes students produced while reading.

Results

Students made significantly more elaborative and connecting inferences when reading a text with deep cohesion, simple syntax, and concrete words, while students made more evaluative comments, paraphrases, and metacognitive comments when reading a text with referential cohesion, complex syntax, and abstract words.

Conclusions

The current study provides exploratory evidence for features of text complexity affecting the type of comprehension processes middle school readers generate while reading science texts. Accordingly, science classroom texts and materials can be evaluated for word, sentence, and passage features of text complexity in order to encourage deep level comprehension of middle school readers.
Fragmentation and kinematics in high-mass star formation
Authors: Beuther H. , Gieser C. , Suri S. , Linz H. , Klaassen P. , Semenov D. , Winters J. M. , Henning Th. , Soler J. D. , Urquhart J. S. , Syed J. , Feng S. , Möller T. , Beltrán M. T. , Sánchez-Monge Á. , Longmore S. N. , Peters T. , Ballesteros-Paredes J. , Schilke P. , Moscadelli L. , Palau A. , Cesaroni R. , Lumsden S. , Pudritz R. , Wyrowski F. , Kuiper R. , Ahmadi A.
Published: March 2021

Context. The formation of high-mass star-forming regions from their parental gas cloud and the subsequent fragmentation processes lie at the heart of star formation research.

Aims. We aim to study the dynamical and fragmentation properties at very early evolutionary stages of high-mass star formation.

Methods. Employing the NOrthern Extended Millimeter Array and the IRAM 30 m telescope, we observed two young high-mass star-forming regions, ISOSS22478 and ISOSS23053, in the 1.3 mm continuum and spectral line emission at a high angular resolution (~0.8″).

Results. We resolved 29 cores that are mostly located along filament-like structures. Depending on the temperature assumption, these cores follow a mass-size relation of approximately M ∝ r2.0 ± 0.3, corresponding to constant mean column densities. However, with different temperature assumptions, a steeper mass-size relation up to M ∝ r3.0 ± 0.2, which would be more likely to correspond to constant mean volume densities, cannot be ruled out. The correlation of the core masses with their nearest neighbor separations is consistent with thermal Jeans fragmentation. We found hardly any core separations at the spatial resolution limit, indicating that the data resolve the large-scale fragmentation well. Although the kinematics of the two regions appear very different at first sight – multiple velocity components along filaments in ISOSS22478 versus a steep velocity gradient of more than 50 km s−1 pc−1 in ISOSS23053 – the findings can all be explained within the framework of a dynamical cloud collapse scenario.

Conclusions. While our data are consistent with a dynamical cloud collapse scenario and subsequent thermal Jeans fragmentation, the importance of additional environmental properties, such as the magnetization of the gas or external shocks triggering converging gas flows, is nonetheless not as well constrained and would require future investigation.
The young Adelaide family: Possible sibling to Datura?
Authors: Vokrouhlický D. , Novaković B. , Nesvorný D.
Published: March 2021

Context.Very young asteroid families may record processes that accompanied their formation in the most pristine way. This makes analysis of this special class particularly interesting.

Aims.We studied the very young Adelaide family in the inner part of the main belt. This cluster is extremely close to the previously known Datura family in the space of proper orbital elements and their ages overlap. As a result, we investigated the possibility of a causal relationship between the two families.

Methods.We identified Adelaide family members in the up-to-date catalogue of asteroids. By computing their proper orbital elements we inferred the family structure. Backward orbital integration of selected members allowed us to determine the age of the family.

Results.The largest fragment (525) Adelaide, an S-type asteroid about 10 km in size, is accompanied by 50 sub-kilometre fragments. This family is a typical example of a cratering event. The very tiny extent in the semi-major axis minimises chances that some significant mean motion resonances influence the dynamics of its members, though we recognise that part of the Adelaide family is affected by weak, three-body resonances. Weak chaos is also produced by distant encounters with Mars. Simultaneous convergence of longitude of node for the orbits of six selected members to that of (525) Adelaide constrains the Adelaide family age to 536 ± 12 kyr (formal solution). While suspiciously overlapping with the age of the Datura family, we find it unlikely that the formation events of the two families are causally linked. In all likelihood, the similarity of their ages is just a coincidence.
Sublimation of ice-dust mixtures in cooled vacuum environments to reproduce cometary morphologies
Authors: Haack David , Lethuillier Anthony , Kreuzig Christopher , Feller Clément , Gundlach Bastian , Pommerol Antoine , Blum Jürgen , Otto Katharina
Published: March 2021

Aims. The morphology of cometary surfaces can provide important information to constrain the composition and evolution of comets. In this work, we investigate the sublimation behavior of comet analog materials and how the sample composition affects the evolution of morphological features in laboratory experiments. In our experiments, we used dust ice mixtures as analog material to form observed cometary morphologies.

Methods. We used ice-dust mixtures in different mixing ratios as cometary analog material. In order to obtain realistic results, we scaled the expected cohesive and gravitational forces on comets to laboratory conditions. The samples were placed in a vacuum sublimation chamber and permanently cooled down to temperatures below 150 K to simulate the space environment. In the experiment, the samples were insolated with a light source from two different directions and alterations on the surface were recorded with a camera.

Results. We find that the morphology of sublimation residues of ice-dust mixtures is strongly dependent on the ice-dust ratio as well as the insolation direction. High amounts of ice cause constant surface alteration and lead to exotic morphologies. Low amounts cause fewer and more episodic surface changes during its sublimation. Collapse events resulting in irregular and very rough surfaces occur during horizontal insolation.
Chromospheric and coronal heating and jet acceleration due to reconnection driven by flux cancellation
Authors: Syntelis P. , Priest E. R.
Published: March 2021

Context. Recent observations have shown that magnetic flux cancellation occurs at the photosphere more frequently than previously thought.

Aims. In order to understand the energy release by reconnection driven by flux cancellation, we previously studied a simple model of two cancelling polarities of equal flux. Here, we further develop our analysis to achieve a more general setup where the two cancelling polarities have unequal magnetic fluxes and where many new features are revealed.

Methods. We carried out an analytical study of the cancellation of two magnetic fragments of unequal and opposite flux that approach one another and are located in an overlying horizontal magnetic field.

Results. The energy release as microflares and nanoflares occurs in two main phases. During phase 1a, a separator is formed and reconnection is driven at it as it rises to a maximum height and then moves back down to the photosphere, heating the plasma and accelerating plasma jets in the process. During phase 1b, once the separator moves back to the photosphere, it bifurcates into two null points. Reconnection is no longer driven at the separator and an isolated magnetic domain connecting the two polarities is formed. During phase 2, the polarities cancel out at the photosphere as magnetic flux submerges below the photosphere and as reconnection occurs at and above the photosphere and plasma jets and a mini-filament eruption can be produced.
Alfvén wave heating in partially ionized thin threads of solar prominences
Authors: Melis Llorenç , Soler Roberto , Ballester José Luis
Published: March 2021

There is observational evidence of the presence of small-amplitude transverse magnetohydrodynamic (MHD) waves with a wide range of frequencies in the threads of solar prominences. It is believed that the waves are driven at the photosphere and propagate along the magnetic field lines up to prominences suspended in the corona. The dissipation of MHD wave energy in the partially ionized prominence plasma is a heating mechanism whose relevance needs to be explored. Here we consider a simple 1D model for a non-uniform thin thread and investigate the heating associated with dissipation of Alfvén waves. The model assumes an ad hoc density profile and a uniform pressure, while the temperature and ionization degree are self-consistently computed considering either local themodynamical equilibrium (LTE) or non-LTE approximations for the hydrogen ionization. A broadband driver for Alfvén waves is placed at one end of the magnetic field line, representing photospheric excitation. The Alfvénic perturbations along the thread are obtained by solving the linearized MHD equations for a partially ionized plasma in the single-fluid approximation. We find that wave heating in the partially ionized part of the thread is significant enough to compensate for energy losses due to radiative cooling. A greater amount of heating is found in the LTE case because the ionization degree for core prominence temperatures is lower than that in the non-LTE approximation. This results in a greater level of dissipation due to ambipolar diffusion in the LTE case. Conversely, in the hot coronal part of the model, the plasma is fully ionized and wave heating is negligible. The results of this simple model suggest that MHD wave heating can be relevant for the energy balance in prominences. Further studies based on more elaborate models are required.
Trace element content, Amino acid composition and fatty acid profiles and of Timadidite’s lamb meat, raised in an agro-silvo-pastoral system of the Moroccan middle-Atlas
Authors: Belhaj Kamal , Mansouri Farid , Melhaoui Reda , Taaifi Yassin , Sindic Marianne , Boukharta Mohamed , Serghini C. Hana , Elamrani Ahmed
Published: March 2021

Traditional food products are often considered beneficial and healthy Foods. Timahdite sheep breed is the main sheep breed raised in the middle-Atlas in Morocco. The breeding of this local rustic breed plays a crucial socio-economic role in this mountain area. Indeed, it generates a significant economic input for the rural population and plays a role of valuing natural resources in forest areas. Little information is available on Timahdite sheep meat produced in a traditional production system. This study aimed to provide more insights on the quality and nutritional value of Tamahdite’s sheep meat, which is in the process of being labeled “Protected Geographical Indication” as a protected product from the Middle Atlas. The longissimus lumborum is used for meat analysis and quality parameter determination. Analyses of amino acid composition show that this meat has a high protein value with a protein digestibility-corrected amino acid score of 325.09 and EAA index of 162.20. The fatty acid profile analysis shows that this meat has polyunsaturated fatty acids (PUFA)/saturated fatty acids and n-6/n-3 PUFA ratios of 0.50 and 9.60, respectively. In addition, the results show that this meat contains 5.70 mg/100g of trace elements, where zinc and iron are the most abundant.
Assessment of the impact of Imzouren city’s WWTP on the quality of the surrounding groundwater, at the Rif Central (Northern Morocco)
Authors: Benyoussef Said , El Ouarghi Hossain , Arabi Mourad , El Yousfi Yassine , Azirar Maryam , Ait Boughrous Ali
Published: March 2021

The groundwater of the Ghis-Nekor aquifer (Central Rif of Morocco) is the main water resource used by the inhabitants for agricultural and domestic purposes. However, its low quality may affect the health of the consumer and weaken agricultural production. The existence of the WWTP at the level of this plain, makes it a probable source of pollution for these groundwater and requires urgent water managers’ intervention. Groundwater pollution in this area may be related to natural, anthropogenic and undefined sources (agricultural and industrial activities). To assess the impact of WWTP effluent on this aquifer, ten well water samples were collected upstream and downstream of this WWTP in 2018, and then analysed for physicochemical quality. Multivariate and principal Component Analysis (PCA) of the results obtained revealed two main components, in which the largest source of total variation being F1 presented at 54.75%. The PCA has visualized two groups that distinguish slightly mineralized well waters upstream to moderately from other wells downstream of the WTTP that are highly mineralized. Generally, the groundwater in the study area is characterized by high levels of salinization. The results of this study may be useful for monitoring and managing groundwater pollution in the study area.
Biomedical Waste Management (BMW) Assessment at the RHC Regional Hospital in Tangier, Morocco
Authors: El Morhit Amina , El Morhit Mohamed , Mourabit Nadira , Zouhdi Mimoun
Published: March 2021

Biomedical waste is a real danger to public health and the environment. The quantity of this waste, mainly from hospitals, is constantly increasing, leading to various forms of pollution. This is a cross-sectional, observational study that took place in 2017. A questionnaire was submitted to nurses, doctors and those responsible for hospital hygiene and the operation of waste incinerators to assess the mechanisms and knowledge of medical staff in terms of biomedical waste management. It was confirmed that the hospital wastes are still poorly managed due to the absence of a plan or program for MPSD in all the structures studied, which attests to the non-application of the regulations in force and an inadequate internal management system in most laboratories. Due to the non-availability of health technicians and the lack of material resources in quality and quantity, a staff that is poorly informed about the regulations that apply to BMW, and a poorly recognized and disrespected BMW process that breaks even the clearest instructions regarding incineration and landfill disposal. It has become very urgent to adopt new strategies to be planned for an adequate training to be included for better medical waste management.
Substantiation and Selection of Optimal Method of Angren Section Field Drainage
Authors: Baimirzaev Bakhtiyor Z. , Matkarimov Sokhibjon T.
Published: March 2021

This article describes the results of the timely drainage of the Angren section using the horizontal drains method. It thereby creates favorable conditions for the effective operation of all technological links of the unit, protecting water resources of the area where the section is located using drainage and quarry waters in the national economy.
Homogeneous succinylation of cellulose acetate: Design, characterization and adsorption study of Pb(II), Cu(II), Cd(II) and Zn(II) ions
Authors: Zannagui Chahid , Amhamdi Hassan , El Barkany Soufian , Jilal Issam , Sundman Ola , Salhi Amin , Abou-Salama Mohamed , El Idrissi Abderahmane
Published: March 2021

In this study, the removal of Pb(II), Cu(II), Cd(II), and Zn(II) ions from aqueous solutions was investigated using succinic anhydride modified cellulose monoacetate. In the first part, the cellulose acetate was successfully succinylated in a homogenous medium of DMF using 4-dimethylaminopyridine (DMAP) as a catalyst. The obtained material (AcS) was analyzed by FTIR and CP/MAS13C NMR Spectroscopy, thermogravimetry analysis and DRX patterns. The titration method was used to determinate the degree of hydroxyl group substituted by carboxyl group (DS) and was found to be 1.36. In the second part, the Bach technique was used to study the effects of pH, contact time, concentration of metals, ionic selectivity and regeneration. Maximum sorption capacities of AcS for Pb(II), Cu(II), Cd(II), and Zn(II) were 241.81, 133.76, 156.61 and 73,58 mg.g-1, respectively. The Langmuir isotherm and the pseudo second order kinetic models provided best fit to the experimental data of metal ion sorption. The nature of the adsorption process was exothermic and spontaneous in nature with negative values of ΔG° and ΔH°. Regeneration of the modified cellulose acetate was accomplished using nitric solution and showed high stability and good recyclability.
Analysis of Leachate and Water Resource Quality Surrounding Municipal Solid Waste Landfill of Tamellast (Agadir, Morocco)
Authors: Asouam Saadia , Faik Farid , El Morjani Zine El Abidine
Published: March 2021

The aim of this work was to study the physicochemical characterization and heavy metal testing results carried out for leachate generated by the landfilling of household and similar waste in the Tamellast landfill of Agadir. The surface and groundwater resource (often used as drinking source) samples collected from Tamellast and different water sources wells surrounding the landfill were used to find out the impact of leachate percolation on surface and groundwater quality. The Physico-chemical parameters analyzed were, pH, Electrical Conductivity (EC), Dissolved oxygen, Sodium, Potassium, while biological parameters tested were Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), E.Coli and Coliform tot. The contamination was investigated by measuring the concentration of heavy metals (Pb, Zn, Cr, Ni, As, and Fe). The Electrical Conductivity (EC), COD, BOD, Sodium, Potassium, in leachate were found to be 13180 µs/cm, 3150 mgO2/l, 1000 mgO2/l, 2000 mg/L, and 10700 mg/L, respectively. The concentration in the surrounding dug wells varied from 8.33 – 9.13 mg/L for Dissolved Oxygen, 9.8 – 18 mg/L for potassium, 0.22 – 0.6 mg/L for Fe, and 0.012 – 0.1 mg/L for total Mn. The concentration of Mn, Fe, and other parameters decreased with increasing distance between the landfill and wells.
Short term measurements of indoor air quality when using the home office in Norway
Authors: Alonso Maria Justo , Jørgensen Rikke Bramming , Mathisen Hans Martin
Published: March 2021

In 2020, due to the outbreak of COVID-19 many workers have been sent home to avoid the sickness spread. As a result, rooms that otherwise had domestic use, living rooms or bedrooms, have become offices. This change has happened in many houses without improving the ventilation systems. In many cases, the rooms were overcrowded, and no attention was paid to ventilation. Thus, this study collects measurements of one to two weeks in different home offices. Measurements were taken in home offices used by one or more occupants. These home offices were designed as bedrooms and living rooms with and without separation from the kitchen. During the pandemic they are used as offices during working hours and as designed otherwise. One or more occupants shared the rooms. Natural and mechanically ventilated and older and newer home offices were studied. Winter measurements of CO2, temperature, relative humidity, particulate matter, formaldehyde and TVOC were collected via low-cost sensors. The sensors were placed on the working space in front of the user to map the exposure to pollutants. The results show an analysis of the concentration of pollutants close to the breathed air. Some users were smart, remembering the aeration, whereas others were exposed to high concentrations of CO2 and other pollutants sometimes higher than the health-based thresholds.
Control of Indoor climate of Historical cult buildings
Authors: Metals Martins , Lesinskis Arturs , Turauskis Kristaps
Published: March 2021

There are 320 historical cult buildings as cultural monuments of national significance in Latvia. Cultural and historical art monuments and artifacts (paintings, organs, chairs, altars, pulpits) must be preserved and protected in these cultural buildings. Specific indoor climate is necessary to maintain in historical cult buildings to pass on to future generations, but those specific requirements often are complete opposite of the actual microclimate and what the user wants.

Indoor climate measurements have been carried out in five brick wall and two wooden churches with and without heating systems. Potential condensation risks are determined using calculations. Typical air flow has been formed using building’s termography measurements. Heating systems and making use of buildings influence historical buildings and this has been determined. The main aim of the article is to determine potential indoor climate type of control in historical cult buildings avoiding humidification and dehumidification, and it is similar in the coastal climate of the Baltic Sea.

Results show that: great humidity fluctuations have been observed in buildings which have been used during winter, outdoor air has a great impact to buildings, less humidity fluctuations have been observed in buildings with controlled heating systems.
Experimental testing of exterior wall mounted mechanical ventilation exhaust air outlet devices
Authors: Palmiste Ülar , Meier Tauno , Kurnitski Jarek , Voll Hendrik
Published: March 2021

The purpose of the study was to experimentally test the performance of four types of wall-mounted mechanical ventilation exhaust air outlet devices. A full-scale mock-up of a segment of an external wall with an exhaust air outlet was constructed. The tested exhaust air devices include a gravity louver, fixed-blade louver, louver plate, and exhaust nozzle. The performance assessment included two types of experiments over the exhaust airflow rate range of 25–94 l/s at isothermal conditions with no influencing wind: (i) the particle tracer method with smoke to visualize the exhaust air jets from the outlets, and (ii) the tracer gas method to measure the dilution of CO2 concentration in the exhaust air jet. Furthermore, the aerodynamic performance was comparatively evaluated in terms of pressure drop and exhaust air face velocity at the outlet. The qualitative comparison of airflow patterns by smoke visualization showed notable differences between the tested device types. Concentration decrease evaluation indicated that the exhaust air pollutants are more efficiently transported away from the building wall by exhaust outlets that discharge at 0–45 degrees downwards from the horizontal plane. Discharge angles 60–90 degrees downwards produced a wall-attached jet and the pollutant tracer concentration remained relatively high in the vicinity of the wall.
Survey of facial masks using behaviour during COVID-19 outbreak
Authors: Yu Xinkai , Yang Hao , He Junzhou
Published: March 2021

Wearing facial masks has been indicated as an effective way to reduce the risk of COVID-19 transmission among people. To get a deeper understanding of the habit of using face masks in normal life during COVID-19 outbreak and seek ways to solve the problems of mask using, we conducted a large-scale survey in China through online questionnaires. Totally 1004 respondents, including community outreach workers, non-healthcare professionals, retired people, and students participated in this study. Detailed information regarding the types of masks that people usually use, the habit of changing masks, the methods of mask cleaning, and the attitude toward reusing masks and their potential impact on the environment were collected and analyzed. Results show that more than 98% of people in China used masks during the pandemic, and the types of masks using and frequency of masks changing/reuse varied between different people. Moreover, most of the respondents had a healthy mask-changing habit for preventing the spread of COVID-19 and worried about the safety of mask reusing. The study would help enhance public awareness and develop policies for a better habit in face of the pandemic.
Energy Production in Solar Collectors in a University Building Used to Improve the Internal Thermal Conditions in Winter Conditions
Authors: Conceição Eusébio , Gomes João , Lúcio Mª Manuela , Awbi Hazim
Published: March 2021

In this numerical study the energy production in solar collectors in a University building used to improve the internal thermal conditions is made. Passive and active solutions, using external solar collector and internal thermo-convectors, are used. The numerical simulation, in transient conditions, is done for a winter typical day with clean sky. This numerical study was carried out using a software that simulates the Building Dynamic Response with complex topology in transient conditions. The software evaluates the human thermal comfort and indoor air quality levels that the occupants are subjected, Heated Ventilation and Air Conditioned energy consumption, indoor thermal variables and other parameters. The university building has 107 compartments and is located in a Mediterranean-type environment. External solar water collectors, placed above the building’s roof, and internal thermo-convectors of water/air type, using mixing ventilation, are used as passive and active strategies, respectively. The thermal comfort level, using the Predicted Mean Vote index, and the indoor air quality, using the carbon dioxide concentration, are evaluated. The results show that in winter conditions the solar collectors improve the thermal comfort conditions of the occupants. The indoor air quality, in all ventilated spaces, is also guaranteed.
Factors affecting the deep renovation of a single-family building – a case study
Authors: Bergmann Triinu , Ruus Aime , Kalbe Kristo , Kiviste Mihkel , Tintera Jiri
Published: March 2021

The Energy Performance of Buildings Directive (EPBD) of the EU states that Each Member State shall establish a long-term renovation strategy to support the renovation of building stock into a highly energy efficient and decarbonised building stock by 2050. The motive for the study was the dissatisfaction of inhabitants of a single-family building about the heating costs and thermal discomfort. In this study both the emotional and resource efficiency aspects were considered. The structures and technical systems of the studied small dwelling are typical of representing single-family buildings of the Estonian building stock. The initial purpose was to improve the energy efficiency of a building while preserving the existing load bearing structures as much as possible. The research questions were: 1) what the situation before the renovation was, 2) what solutions can be used, 3) making decisions, whether to renovate or demolish. Calculations were carried out – the thermal transmittance of the envelope structures was calculated based on the construction information, and the linear thermal transmittance of geometrical thermal bridges was calculated by using the software Therm. Field tests performed - the thermography and the air leakage of the building was found by standard blower-door test. Specific air leakage rate qE50=11.1 m3/(hm2) was estimated. A renovation solution was offered considering the need for extra insulation and airtightness. The dwelling energy performance indicator was reduced from the existing 279 kWh/(m2y) to 136 kWh/(m2y). For significant energy efficiency improvement deep renovation measures must be used and the question was whether it is rational. Before making the final decision, several aspects have to be considered: 1) emotional – the demolition or renovation of somebody’s home, 2) environmental aspects and resource-efficiency – the possibilities of the reuse of materials.
Cost-optimal nZEB HVAC configurations with onsite storage
Authors: Ochs Fabian , Magni Mara , Venturi Elisa , Tosatto Alice , Streicher Wolfgang
Published: March 2021

By 2021, all new buildings in the European Union must be nearly zero-energy buildings in order to contribute to the achievement of the EU-CO2 neutrality by 2050. As the technical options to achieve highly-efficient building envelopes are available and well-known, there is no doubt that the most promising Heating Ventilation and Air Conditioning systems will include heat pumps and photovoltaic panels. However, there exist ongoing discussions on the optimal system layout and the integration of storage to achieve nZEB. In particular, there are some good arguments in favour of very low demand, while contrariwise also high flexibility is seen as an important feature to enable so-called grid-reactive operation of the building stock. Integration of onsite storage and its influence on the energy demand of the buildings and the corresponding electric load profile with focus on peak power is investigated.
Requirements for Building Thermal Conditions under Emergency Operations in Cold Climates
Authors: Zhivov Alexander M. , Rose William B. , Patenaude Raymond E. , Williams W. Jon
Published: March 2021

This paper provides recommendations on thermal and moisture parameters in different types of buildings under emergency operation in cold/arctic climates. We consider three scenarios under normal operating conditions: occupied, temporarily unoccupied, and long-term unoccupied. These thermal parameters are necessary to: (1) perform required work safely and efficiently, (2) support building processes, and (3) support long-term integrity of the building under emergency conditions (i.e., interruption of fuel, steam, hot water, and electrical service that interrupts building space conditioning). Under emergency conditions, requirements of thermal parameters for different categories of buildings may change. Mission critical areas can be conditioned to levels that support the agility of personnel who perform critical operations, but not to optimal comfort levels. Critical process requirements are given priority. This paper was developed for military applications, based on research performed under the International Energy Agency’s Energy in Buildings and Communities Program, Annex 73; under the Department of Defense Environmental Security Technology Certification Program project EW18-D1-5281, “Technologies Integration to Achieve Resilient, Low-Energy Military Installations,” and under the Office of the Deputy Assistant Secretary of the Army project “Thermal Energy Systems Resiliency for Army Installations located in cold climates.” Results are applicable to similar public and private sector buildings.
HVAC Best Practices in Arctic Climates
Authors: Winfield Emily C. , Rader Robin J. , Zhivov Alexander M. , Dyrelund Anders , Fredeen Craig , Gudmundsson Oddgeir , Goering Brent
Published: March 2021

Arctic climates provide unique challenges for designers of HVAC, plumbing, and thermal energy systems. The importance of considering the operation outside air temperatures, system reliability, and building resiliency cannot be understated. The paper describes best practice examples of robust and reliable systems with the emphasis on their redundancy, durability, and functionality. The paper also discusses the most common heating and ventilation system approaches used in arctic climate with the emphasis on the importance of a maintenance program that allows building operators to successfully troubleshoot and maintain buildings in the arctic. More detailed discussion of concepts presented in this paper can be found in the Guide [1] where these concepts are illustrated by best practice examples from U.S. military bases in Alaska and Søndre Strømfjord, the international airport of Greenland that previously was used as a U.S. military base. The paper results from experts’ discussions during the Consultation Forum “Thermal Energy Systems Resilience in Cold/Arctic Climates” [2] and research conducted under the IEA EBC Annex 73, the Environmental Security Technology Certification Program (ESTCP) Project “Technologies Integration to Achieve Resilient, Low-Energy Military Installations” and U.S. Army Program project 633734T1500 under Military Engineering Technology Demonstration. The paper is complementary to the ASHRAE Cold Climate Design Guide [3] with a focus on resilience of thermal energy systems.
Energy Efficient Air Curtains for Industrial Gates in Cold Climates
Authors: Strongin A.S. , Zhivov A.M.
Published: March 2021

In geographical areas with cold climates, large, massively constructed industrial and warehouse buildings and logistics complexes are large consumers of energy resources. The great height and large contained volumes of the premises, the presence of a significant number of doors, and building configurations that include many transport corridors all require the use of air-thermal curtains to increase the energy efficiency of the buildings’ heating, ventilating, and air-conditioning (HVAC) systems, which commonly produce several thousand kilowatts of thermal power. Optimization of air curtains can improve the microclimates of the premises, achieve savings in the initial construction costs, and also reduce energy consumption during operation by 10–20%.
Impact of different mechanical ventilation strategies for night purging on indoor air quality in public buildings
Authors: Lestinen Sami , Kilpeläinen Simo , Kosonen Risto , Jokisalo Juha
Published: March 2021

Night-time ventilation has been used in non-residential buildings to enhance indoor air quality before occupied periods. However, many hypotheses exist on how this ventilation should be used. A typical choice has been to shut down the ventilation after occupancy and restart the ventilation again 2 hours before occupancy. Another option has been to ventilate the buildings continuously. In this study, the shut-down, continuous, and intermittent ventilation strategies were compared by evaluating indoor air quality. The daily occupied-hour ventilation was kept as usual. Each test case lasted for 2 weeks. Indoor air quality was assessed by measuring TVOC concentrations. Also, the thermal conditions, carbon dioxide, and pressure differences over the building envelope and over the air distribution devices were measured. The results show that the averaged TVOC concentrations were at the same level in the mornings with all those ventilation strategies. The evening concentrations reached a minimum level after a 2-hour purging period. TVOC concentrations were higher during the day than at night. This reveals that space usage had the largest effect on TVOC concentrations. The results indicate that a 2-hour purging is enough to cleanse indoor air before occupancy, and therefore the continuous night-time ventilation is not necessary.
Recommendations for model identification for MPC of an all-Air HVAC system
Authors: Carton Quinten , Merema Bart , Breesch Hilde
Published: March 2021

Rule-based control (RBC) strategies are often unable to execute the optimal control action, which leads to unnecessary energy consumption and suboptimal comfort. Model predictive control (MPC) is a dynamic control strategy for heating, ventilation and air-conditioning (HVAC) systems that is mostly more capable of performing optimal control actions. The identification process of predictive models is an essential aspect of MPC. However, this model identification process remains time consuming due to the large variation in buildings and systems. The aim of this paper is to determine guidelines to identify predictive grey-box models more time efficient, thus enhancing the applicability of MPC.

This paper focusses on a case study building equipped with an all-air HVAC system, which combines ventilation, heating and cooling. Making both temperature and CO2-concentration key parameters to predict. The grey-box model represents an open zone in a landscaped office, making the influence of neighbouring zones an additional challenge.

Different models for predicting the zone temperature and CO2-concentration are identified, evaluated and validated using CTSM-R. The following aspects are studied: the dataset size, the influence of neighbouring zones, the difference between winter and summer conditions, number of states and the prediction horizon.

A three state RC-model with the implementation of the zone temperature of one neighbouring zone is preferred for predicting the indoor temperature with an acceptable prediction horizon of one day. However, this temperature model is not suitable during sunny periods. A simple model representing a mass balance obtains accurate predictions of the zone CO2-concentration for a timestep of 15 minutes. For both model types the utilization of 5-day datasets is favoured over 12-day datasets due to a shorter monitoring period, lower prediction error and an easier parameter convergence. The usage of 12-day datasets is only preferred when an accurate estimation of the thermal inertia is pursued.
Implementation of MPC for an all-air system in an educational building
Authors: Merema Bart , Carton Quinten , Saelens Dirk , Breesch Hilde
Published: March 2021

The building sector has to significantly reduce the total energy use. A predictive control could be a solution to control an HVAC system more energy efficiently since it takes into account the current measurements and the future demand. In this study a predictive control framework is implemented in an educational building with two lecture rooms. The airflow rate is controlled by VAV boxes based on measurements of CO2 concentration and operative temperature. The dynamic model used for optimization of the control input is a grey-box model, previously identified using measurement data. Weather forecasts and weekly lecture schedules are used as forecasts for the optimization of future control actions. The control actions resulting from the optimization are written to the set points for supply air temperature and VAV damper position using the BACnet interface. Results of the first trial indicate that the predictive control is able to control the room temperature and CO2 concentration, even with uncertainty introduced by the forecasts. Prediction errors observed were 0.17 ˚C for room temperature and 87 ppm for indoor CO2 concentration.
Comparison of Heat Recovery Ventilator Frost Control Techniques in the Canadian Arctic: Preheat and Recirculation
Authors: Berquist Justin , Banister Carsen , Pellissier Mathieu
Published: March 2021

Air-to-air heat/energy recovery ventilators can effectively reduce the cost associated with ventilating a home. However, high indoor moisture levels, in conjunction with extreme temperature differences between the outdoor and indoor air can cause frost accumulation in the mechanical equipment, leading to performance degradation or failure. In this research, a demonstration house using a heat recovery ventilation system in Iqaluit, Nunavut, Canada was used to compare the performance of two frost control techniques: recirculation and electrical preheat. The advantages and disadvantages of each method are outlined to highlight the need to adapt southern strategies to ensure system functionality in the Arctic. The system was equipped with a heat recovery ventilator (HRV) with built-in recirculation technology to defrost the HRV, as well as two electric preheaters that can be used instead of recirculation and prevent frost formation. Between December 2018 and April 2019 the ventilation system’s performance was monitored for seven weeks while using either recirculation or electrical preheat. The experiments showed the ventilation system equipment consumed more absolute energy with electrical preheat than with recirculation as the frost control technique. However, when using recirculation, the ventilation system experienced more losses throughout the ventilation system, causing the whole building to consume more energy due to an increase in energy consumption by the home’s heating system. Moreover, the quantity of outdoor air that was restricted while using recirculation made electrical preheat the superior option for this ventilation system design. The energy use of the ventilation system with electric preheat enabled was 35% lower on a per volume of outdoor air basis. Contrary to some belief that preheating is a poor approach for frost control in heat/energy recovery ventilators, this research finds that preheating can be a more energy efficient method to provide ventilation if controlled well.
Building performance indicators and IEQ assessment procedure for the next generation of EPC-s
Authors: Võsa Karl-Villem , Ferrantelli Andrea , Tzanev Dragomir , Simeonov Kamen , Carnero Pablo , Espigares Carlos , Escudero Miriam Navarro , Quiles Pedro Vicente , Andrieu Thibault , Battezzati Florian , Cordeiro Katia , Allard Francis , Magyar Zoltan , Turturiello Giusy , Piterà Luca Alberto , d’Oca Simona , Willems Eric , Veld Op ’t Peter , Lițiu Andrei Vladimir , Lungu Cătălin , Catalina Tiberiu , Kurnitski Jarek
Published: March 2021

In the current implementation of EPC-s, the assessment focus is purely on the energy consumption data. For the next generation of EPC-s, new performance indicators are proposed to address relevant building performance aspects, such as sustainability, productivity and market value. These indicators would enable evidence-based decision-making processes and facilitate the delivery of renovation triggers. Within the EPC framework, the problem is not the availability of such performance indicators, but the assessment effort required. Only easily available data can justifiably be introduced to bulk EPC-s, either as direct complementary input or as a performance indicator. Availability of such data was analysed from case studies that included EPC-s from 11 EU member states, mainly non-residential buildings. Analysed data included relevant HVAC information such as ventilation air flows, heating and cooling set-points and installed power, but also output data, such as EPC classes, net and primary energy need and GHG emissions. Based on our findings, we outlined two different development paths - one for existing buildings and one for new buildings and major renovations. Two categories of complementary indicators to energy are proposed – IEQ and power indicators.
HVAC’s Role in the Decarbonisation of the Existing BuildingStock - case Finland
Authors: Vainio Terttu , Nippala Eero , Kauppinen Timo
Published: March 2021

The Energy Performance of Buildings Directive together with the Energy Efficiency Directive and Renewable Energy Sources Directive define the frame and target state for energy performance of the existing building stock. This should be very energy efficient and decarbonised by 2050. The Finnish target is more ambitious, to achieve the target state already in 2035. In this paper, we discuss and concretise the role of HVAC in overcoming the challenge. Buildings in the Nordic countries are already very energy efficient. Structural improvements of energy efficiency are relatively expensive and have limited potential for energy saving. The best cost-benefit ratio can be obtained by combining HVAC with dynamic building automation systems. Also the EPBD calls for improvement of building automation systems and related measurements in new as well as existing buildings. The performance of buildings can be verified and deviations can be detected by monitoring-based commissioning during their life cycle. This means that special attention must be paid to the instrumentation level and an improved online reporting system for stakeholders. As a conclusion, we see that HVAC systems are in a key role in decarbonisation of existing buildings and a strategic sector on the way to a carbon-neutral society.