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1.
Economies ; 10(7):168, 2022.
Article in English | ProQuest Central | ID: covidwho-1963777

ABSTRACT

Faced with food supply disruptions due in part to geopolitics and political instability in its traditional food source markets in the Kingdom of Saudi Arabia and the United Arab Emirates, Qatar—a wealthy, highly import-dependent open economy—plans to identify a set of alternative markets that can assure it of a stable food supply chain and food security. This study develops a set of preferences and import substitution elasticities for the country’s four most important food categories: meats, dairy, vegetables, and cereals. We used quarterly food import data from 2004 to 2017 and the Restricted Source-Differentiated Almost Ideal Demand System (RSDAIDS) to estimate import-substitution elasticities for meats, dairy, vegetables, and cereals imported by Qatar. Based on our findings, India, Australia, and the Netherlands emerged as Qatar’s most competitive sources of food, followed by Brazil, Jordan, and Argentina. Qatar can assure sustained demand for food imports from the aforementioned countries in order to address its food security.

2.
Journal of Hypertension ; 40:e176-e177, 2022.
Article in English | EMBASE | ID: covidwho-1937730

ABSTRACT

Objective: Evaluation of the capability of a fixed combination of lisinopril + amlodipine + rosuvastatin (ECWAMER) in achieving additional angioprotection in patients with arterial hypertension (AH) and high pulse wave velocity (PWV) in patients after confirmed COVID-19 had 75 - 95% lung involvement, complicated by bilateral polysegmental viral pneumonia, with genetically engineered biological drugs (GIBD) therapy, who had not previously received combined antihypertensive therapy (AHT). Design and method: An open-label observational study with a duration of 12 weeks has been carried out. 30 patients who not previously received combined AHT was included. Patients underwent daily monitoring of blood pressure (ABPM), applanation tonometry (determination of the augmentation index (IA) and central blood pressure (CSAD)), measurement of PWV, laboratory tests (lipid composition of blood, fasting glucose, C-reactive protein - CRP, OAC, ferritin, fibrinogen, D-dimer, ALT, AST, creatinine, uric acid) before and after prescribing a fixed combination of lisinopril + amlodipine + rosuvastatin (ECVAMER). Results: At baseline, the patients had an increase in office blood pressure to 152.6 / 89.1 mm Hg. After prescribing a fixed combination of lisinopril + amlodipine + rosuvastatin, there was a decrease in systolic blood pressure (SBP) by 15.8% and diastolic blood pressure (DBP) by 12.2%. According to ABPM data, the decrease in SBP was 15% and DBP - 9%, decreased PWV by 23.8%, IA by 9%, CSAP by 12.4% (p < 0.05 for all comparisons with the baseline value). Vascular age (SV) was initially increased to 41.9 years with a passport age of 35.03 years. After the end of therapy, there was a significant decrease in CO up to 36.5 years, LDL by 46.8%, triglycerides by 16.8% and an increase in HDL by 10.7% (p < 0.05 for all comparisons with the baseline value). In addition, the levels of CRP, fibrinogen, D-dimer, glucose, and uric acid significantly decreased. Conclusions: The fixed combination of lisinopril + amlodipine + rosuvastatin provides better blood pressure control, improved vascular elasticity, and also improves lipid and carbohydrate metabolism in patients, reduces inflammation in patients with hypertension and hyperlipidemia after suffering from severe and extremely severe COVID-19.

3.
Int J Mol Sci ; 21(11)2020 May 29.
Article in English | MEDLINE | ID: covidwho-1934082

ABSTRACT

Starting from fertilization, through tissue growth, hormone secretion, synaptic transmission, and sometimes morbid events of carcinogenesis and viral infections, membrane fusion regulates the whole life of high organisms. Despite that, a lot of fusion processes still lack well-established models and even a list of main actors. A merger of membranes requires their topological rearrangements controlled by elastic properties of a lipid bilayer. That is why continuum models based on theories of membrane elasticity are actively applied for the construction of physical models of membrane fusion. Started from the view on the membrane as a structureless film with postulated geometry of fusion intermediates, they developed along with experimental and computational techniques to a powerful tool for prediction of the whole process with molecular accuracy. In the present review, focusing on fusion processes occurring in eukaryotic cells, we scrutinize the history of these models, their evolution and complication, as well as open questions and remaining theoretical problems. We show that modern approaches in this field allow continuum models of membrane fusion to stand shoulder to shoulder with molecular dynamics simulations, and provide the deepest understanding of this process in multiple biological systems.


Subject(s)
Cell Membrane/physiology , Lipid Bilayers/chemistry , Membrane Fusion , Molecular Dynamics Simulation , Animals , Elasticity , Humans , Models, Biological , Normal Distribution
4.
AIMS BIOENGINEERING ; 9(2):197-212, 2022.
Article in English | Web of Science | ID: covidwho-1911806

ABSTRACT

Spreading COVID-19 pandemic has been considered as a global issue. Many international efforts including mathematical approaches have been recently discussed to control this disease more effectively. In this study, we have developed our previous SIUWR model and some transmission parameters are added. Accordingly, the basic reproduction number and elasticity coefficients are calculated at the equilibrium points. Then, some key critical model parameters are identified based on local sensitivities. In addition, the validation of the suggested model is checked by comparing some collected real data in Iraq and France from January 1st, 2021 to December 25th, 2021. Interestingly, there are good agreements between the model results and the real confirmed data using computational simulations in MATLAB. Results provide some biological interpretations and they can be used to control this pandemic more effectively. The model results will be used for both countries in minimizing the impact of this virus on their communities.

5.
Aims Bioengineering ; 9(2):163-177, 2022.
Article in English | English Web of Science | ID: covidwho-1884491

ABSTRACT

The spreading of COVID-19 has been considered a worldwide issue, and many global efforts have been suggested. Suggested control strategies to minimize the impact of the disease have effectively worked with computational simulations and mathematical models. Model critical transmissions and sensitivities are also key elements to study this pandemic more widely. This work reviews and discusses susceptible-exposed-infected-recovered (SEIR) model to predict the spreading of this disease. Accordingly, the basic reproduction number and its parameter elasticity are considered at the equilibrium points. Furthermore, the real data of confirmed cases in the Kurdistan region of Iraq are used in estimating model parameters and model validating. Computational model results provide some important model improvements and suggest control strategies. Firstly, the model population states have different model dynamics using the estimated parameters and the initial values. Another result is that almost all model states are sensitive to the model parameters at different levels. Interestingly, contact rate, transition rate from exposed class to the infected class and natural recovery rate are the most important controllable parameters to reduce the basic reproduction number R o , and they become the model critical parameters. More interestingly, computational results for the real data provide that the basic reproduction number in the Kurdistan Region was about 1.28, which is greater than unity. This means that the new coronavirus still has a high potential to spread among individuals, and it will require more interventions and new strategies to control this disease further.

6.
Families, Relationships and Societies ; 11(2):287-302, 2022.
Article in English | Scopus | ID: covidwho-1875069

ABSTRACT

In 2012, David Morgan gave a talk titled ‘Neighbours, neighbouring and acquaintanceship: some further thoughts’ at the University of Turku, Finland. In this article we engage in dialogue with Morgan’s talk, as well as his 2009 book Acquaintances, in particular the observations he made about the simultaneous closeness and distance that characterises neighbouring relationships. We suggest that using the metaphors of elasticity and stickiness instead allows us to explore neighbouring relationships as more than inhabiting a space between intimates and strangers (Morgan, 2009), but as textured and messy everyday relationalities. We consider also how the ‘stickiness’ of this relationship as well as the significance of its ‘elasticity’ are likely to have been heightened during COVID-19 lockdowns, which have altered the usual configurations of intimate and stranger relationships. In doing so, our aim is to contribute further to Morgan’s theorising of the nature of neighbouring as a specific form of acquaintanceship. © Policy Press 2022.

7.
AIMS Mathematics ; 7(7):12842-12858, 2022.
Article in English | Scopus | ID: covidwho-1847435

ABSTRACT

Several newly nonlinear models for describing dynamics of COVID-19 pandemic have been proposed and investigated in literature recently. In light of these models, we attempt to reveal the role of fractional calculus in describing the growth of COVID-19 dynamics implemented on Saudi Arabia’s society over 107 days;from 17 Dec 2020 to 31 March 2021. Above is achieved by operating two fractional-order differential operators, Caputo and the Caputo-Fabrizio operators, instead of the classical one. One of expanded SEIR models is utilized for achieving our purpose. With the help of using the Generalized Euler Method (GEM) and Adams-Bashforth Method (ABM), the numerical simulations are performed respectively in view of the Caputo and Caputo-Fabrizio operators. Accordance with said, the stability analysis of the two proposed fractional-order models is discussed and explored in view of obtaining the equilibrium points, determining the reproductive number (R0) and computing the elasticity indices of R0. Several numerical comparisons reveal that the fractional-order COVID-19 models proposed in this work are better than that of classical one when such comparisons are performed between them and some real data collected from Saudi Arabia’s society. This inference together with the cases predictions that could easily deduced from the proposed fractional-order models can allow primary decision makers and influencers to set the right plans and logic strategies that should be followed to face this pandemic. © 2022 the Author(s), licensee AIMS Press.

8.
Statistical Modelling: An International Journal ; : 1, 2022.
Article in English | Academic Search Complete | ID: covidwho-1840718

ABSTRACT

We propose a model of retail demand for air travel and ticket price elasticity at the daily booking and individual flight level. Daily bookings are modelled as a non-homogeneous Poisson process with respect to the time to departure. The booking intensity is a function of booking and flight level covariates, including non-linear effects modelled semi-parametrically using penalized splines. Customer heterogeneity is incorporated using a finite mixture model, where the latent segments have covariate-dependent probabilities. We fit the model to a unique dataset of over one million daily counts of bookings for 9 602 scheduled flights on a short-haul route over two years. A control variate approach with a strong instrument corrects for a substantial level of price endogeneity. A rich latent segmentation is uncovered, along with strong covariate effects. The calibrated model can be used to quantify demand and price elasticity for different flights booked on different days prior to departure and is a step towards continuous pricing;something that is a major objective of airlines. As our model is interpretable, forecasts can be created under different scenarios. For instance, while our model is calibrated on data collected prior to COVID-19, many of the empirical insights are likely to remain valid as air travel recovers in the post-COVID-19 period. [ FROM AUTHOR] Copyright of Statistical Modelling: An International Journal is the property of Sage Publications, Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)

9.
Public Finance Quarterly ; 66(1):50-67, 2021.
Article in English | ProQuest Central | ID: covidwho-1836580

ABSTRACT

There is no uniform theoretical standpoint on the effects of changing interest rates and the role of money among economists. Though these disputes exercise a great influence on the economic policy measures adopted as well. For the management of the 2008 global financial crisis many central banks entered into forceful interest rate cuts to contribute to the revitalisation of the economy. The economic recession caused by the pandemic of 2020 again raises the issue how central banks can stimulate growth. In this study we deal with the liquidity trap issue attributed to Keynes. Keynes pointed out that there might exist a lower interest rate limit under which money demand becomes infinite. His conceptions put the foundations to the question, at what interest rate levels might the liquidity trap – a term coined later by Robertson – phenomenon become effective. He was followed by numerous renowned economists dealing with the conception. In this paper we are discussing the most important theoretical approaches – among others the views of Hansen, Hicks, Tobin, Patinkin, Krugman, Brunner and Meltzer and Eggertson. We provide an overview on the effects of low interest rate levels adopted by Japan, by the central banks of Japan, the USA and the ECB aimed at stimulating the economy. Based on the study it can be confirmed that central banks can contribute to economic growth keeping interest rates low and therewith fostering investment. Nevertheless, beyond keeping short-term interest rates low, it might be adequate to control interest rates of other maturities and, especially under deflationary expectations, central banks should express their prolonged commitment to low interest rates.

10.
10th International Conference on Communications, Signal Processing, and Systems, CSPS 2021 ; 878 LNEE:557-565, 2022.
Article in English | Scopus | ID: covidwho-1826329

ABSTRACT

The worldwide spread of COVID-19 has greatly hit global economy by now. The world’s major economies including both developed and developing countries have felt the resulting impact on their financial markets. Accordingly, learning residents’ consumption structure is significant for boosting consumption demand and recovering financial market. In this paper, the Extend Linear Expenditure System (ELES) model is explored to learn both urban and rural residents’ consumption structures of China during COVID-19. In specific, the indices of marginal propensity to consume, income elasticity of demand, and price elasticity can be yielded via the ELES model based on the disposable income and the consumption data. Furthermore, the consumption structures before and during the corona virus epidemic can be quantitatively compared. Extensive experimental results demonstrate that the epidemic has made profound impacts on the consumption structure of residents. Among them, the marginal propensities on food and medical services have greatly increased, while the proportions of other expenditures have been decreased. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

11.
The Journal of the Association of Physicians of India ; 70(4):11-12, 2022.
Article in English | Scopus | ID: covidwho-1824553

ABSTRACT

Iron overload occurs as a result of multiple blood transfusions and increased iron absorption in thalassemia patients. Iron deposition in liver results in liver stiffness and fibrosis. Non invasive methods including imaging and serum biomarkers have been introduced for assessment of liver fibrosis. We aimed to study liver stiffness using transient elastography and serum hyaluronic acid levels and correlate them with serum ferritin levels in adult transfusion dependent beta thalassemia patients. MATERIAL: 70 transfusion dependent thalassemia patients of age ≥18 years, registered at Thalassemia Day Care Centre were subjected to investigations like CBC, Liver function tests, viral markers, serum ferritin, serum hyaluronic acid levels and transient elastography. Fibrosis indices like FIB-4, AAR and APRI were also calculated. 45 patients had T2*MRI reports with them;which were also included and analysed. Spearman coefficient r was used to test correlations between TE values and serum HA levels with other variables. OBSERVATION: 70 patients (41 male and 29 female) with mean age of 24.09±5.38 years and BMI 20.51 ±3.47 kg/m², were enrolled. Median values of hemoglobin, AST, ALT, TE, serum HA and serum ferritin were, 9.15 g/dl, 42 IU/L, 47.50 IU/L, 9.1 kPa, 284 ng/dl and 1841 ng/ml, respectively . TE values had significant positive correlation with serum ferritin (r=0.5, p < 0.001), ALT (r=0.59, p < 0.001), AST (r=0.58, p< 0.001), APRI (r=0.5, p<0.001) and FIB-4 (p=0.02), respectively and significant negative correlation with T2* MRI (ms) (r= -0.5, p<0.001). No significant correlation of HA was found with any variable. CONCLUSION: Transient elastography can be used as a non expensive, easily accessible and non invasive marker of liver iron overload. Further detailed studies are required to establish the role of serum Hyaluronic acid in thalassemia patients. © Journal of the Association of Physicians of India 2011.

12.
MECAS Studies - International Sugar Organization|2021. ((21)06):ii + 51 pp. ; 2021.
Article in English, French, Spanish, Russian | CAB Abstracts | ID: covidwho-1786961

ABSTRACT

The global obesity issue is often linked to the use of added sugars, but this relationship is unproven and there is no internationally recognised evidence that points to a direct link between the consumption of sugar and excess weight. However, in the sphere of public opinion, it is perceived as being beyond question. Furthermore, the objective of reducing added/free sugar from our basic diet has taken on a pathway of its own. This view is not supported by scientific research or published guidelines and should be challenged. Governments have largely chosen to target a reduction in the sugar content of soft drinks as a public health objective. This has been done through taxing sales or sugar content. Our analysis finds that there is a statistically significant impact on sugar consumption in some countries, mainly through the voluntary reformulations undertaken by beverage companies. But that this impact is small in terms of the volume of sugar eliminated. The study sees the application of similar taxes on food manufacturing as challenging, as sugar is used as a functional ingredient and food formulations are inherently more complex. From a public heath perspective, the study notes both a lack of historic evidence for a correlation between sugar consumption growth and obesity as well as a divergence between public health objectives and the current use of sugar. The study also considers behavioural aspects for consumers and food and beverage producers, surmising that the tax effect on consumers is partly short term while producers remain broadly focused on sales and marketing objectives, with public health changes seen as an industry-wide issue. More broadly, the study also notes that COVID-19 will skew results for many years to come. The report also considers the supply and demand dynamics of the sugar market in view of slowing demand, partly contributed to by sugar taxes. With low elasticity for both consumption and production, and with limited growth in the former, the implication is volatile world market prices. Sugar industries more than ever before will need to embrace diversification options such as bio energy and other bio products to ensure a sustainable future in a slowing sugar demand growth environment.

13.
Open Economies Review ; 33(1):157-185, 2022.
Article in English | ProQuest Central | ID: covidwho-1782881

ABSTRACT

We examine the impact of geographic distance, economic size, and jurisdictional borders on Canadian interprovincial trade in services at the industry level. Using a gravity model, we find that the average elasticity of service trade with respect to distance is − 1.1, which coincides with the median estimate of average elasticity of merchandise trade with respect to distance. However, the point estimates of the elasticity of distance are significantly higher in magnitude in Arts and Health, while distance matters much less for Telecommunications and Information Technology. We also find that the elasticity of trade with respect to exporter and importer gross domestic product is highly industry specific. Our findings suggest that distance is still a key determinant of service trade and the income elasticity of demand is heterogeneous within the service sector.

14.
Comput Econ ; 59(3): 1113-1134, 2022.
Article in English | MEDLINE | ID: covidwho-1782851

ABSTRACT

The stochastic elasticity of variance model introduced by Kim et al. (Appl Stoch Models Bus Ind 30(6):753-765, 2014) is a useful model for forecasting extraordinary volatility behavior which would take place in a financial crisis and high volatility of a market could be linked to default risk of option contracts. So, it is natural to study the pricing of options with default risk under the stochastic elasticity of variance. Based on a framework with two separate scales that could minimize the number of necessary parameters for calibration but reflect the essential characteristics of the underlying asset and the firm value of the option writer, we obtain a closed form approximation formula for the option price via double Mellin transform with singular perturbation. Our formula is explicitly expressed as the Black-Scholes formula plus correction terms. The correction terms are given by the simple derivatives of the Black-Scholes solution so that the model calibration can be done very fast and effectively.

15.
Future Healthc J ; 9(1): 41-44, 2022 Mar.
Article in English | MEDLINE | ID: covidwho-1776632

ABSTRACT

Background: The Baveno VI consensus identifies patients with compensated advanced chronic liver disease (cACLD) who can safely avoid screening endoscopy. However, concordance in clinical practice with this guidance is unknown. We audited clinical practice and the provision of transient elastography (TE) aiming to identify potential cost savings and benefits. Methods: Retrospective data collection from 12 sites across London over 6 months by reviewing oesophagogastroduodenoscopy (OGD) reports, platelet count and TE results as well as information on site-specific provision of TE. Results: Three-hundred and fifty-one screening procedures were identified; 177 (50.43%) had a TE test performed within the preceding 12 months; 142 (80.23%) patients with a recent TE test did not meet criteria for screening OGD. TE provision varied widely between sites. Conclusion: Improving concordance with the Baveno criteria through improved provision of TE would have benefits for patients, healthcare systems and the environment and would help to address the challenges of moving on from the COVID-19 pandemic.

16.
2nd International Conference on Big Data Economy and Information Management, BDEIM 2021 ; : 110-113, 2021.
Article in English | Scopus | ID: covidwho-1774572

ABSTRACT

As people become more accustomed to online buying, an increasing number of individuals are purchasing cell phones over the internet. In this paper, the price elasticity of mobile phones from Taobao is estimated using a logarithmic function model, and the link between price elasticity and market share, online sales, and pricing is empirically investigated. This study used data analytic to discover that as the price of a brand with a significant market share drops, the sales volume increases. In addition, this study examines elasticity changes caused by COVID-19 and shows practical implications with proposed business solutions;this study found that The price drop will affect the sales volume, and the sales volume will change with the price change. The findings will give helpful information to internet cell phone vendors. © 2021 IEEE.

17.
J Urol ; 207(1): 152-160, 2022 01.
Article in English | MEDLINE | ID: covidwho-1769451

ABSTRACT

PURPOSE: Urologists will benefit from an imaging modality which can assess intra and extraluminal characteristics of urethral strictures. We conducted a prospective pilot study evaluating the utility of contrast-enhanced ultrasound and shear wave elastography for the evaluation of bulbar urethral stricture disease. MATERIALS AND METHODS: Patients with a single, bulbar urethral stricture were prospectively recruited. Contrast-enhanced ultrasound and shear wave elastography were performed at the time of surgical repair and at 4 months' followup using an Aplio i800 scanner (Canon Medical Systems, Tustin, California) with an i8CX1 transducer. Sulfur hexafluoride lipid-type A microsphere ultrasound contrast (Lumason®, Bracco Imaging, Princeton, New Jersey) was injected retrograde through the urethra. Stiffness of the corpus spongiosum was measured at and adjacent to the stricture site. Stricture lengths based on retrograde urethrogram, grayscale ultrasound and contrast-enhanced ultrasound were correlated with measured intraoperative stricture length. RESULTS: Thirty men were enrolled. Contrast-enhanced ultrasound (R2=0.709) showed the best correlation with intraoperative measured stricture length compared to retrograde urethrogram (R2=0.016) or grayscale ultrasound (R2=0.471). Stiffness of the spongiosum was greater at the site of the stricture (32.6±5.4 vs 27.3±5.8 kPa, p=0.044) and in narrower caliber strictures (p=0.044) but did not differ by stricture length (p=0.182). At followup (4.3±1.1 months) contrast-enhanced ultrasound detected stricture recurrence with 80% sensitivity, 100% specificity, and 93% accuracy compared to cystoscopy. CONCLUSIONS: This pilot study demonstrates the ability of contrast-enhanced ultrasound and shear wave elastography to become safe, accurate, and potentially efficacious modalities for assessing bulbar urethral strictures and spongiofibrosis.


Subject(s)
Contrast Media , Elasticity Imaging Techniques , Urethral Stricture/diagnostic imaging , Adult , Aged , Humans , Male , Microspheres , Middle Aged , Pilot Projects , Prospective Studies , Ultrasonography/methods
18.
Sustainability ; 14(6):3555, 2022.
Article in English | ProQuest Central | ID: covidwho-1765896

ABSTRACT

A well-thought-out strategy for shaping the transport of the future is a challenge for countries and integration groups. The answer to which modes of transport should become a priority in the context of incurred and planned investments should largely depend on their observed and forecasted environmental impact. This paper focuses on the scope and content of EU macro-regional strategies. The main objectives of the study were to identify common assumptions and differences between the Adriatic and Ionian Region and the Baltic Sea Region in terms of sustainable transport and provide a critical assessment of the EU Strategy for the Adriatic and Ionian Region (EUSAIR) and the EU Strategy for the Baltic Sea Region (EUSBSR) compliance with the assumptions of the White Paper on Transport, as well as the attempt to answer the question of which modes of transport should be prioritized by the analyzed macro-regions, making transport decarbonization one of their main goals. It is possible to state that the assumptions of both the strategies of the macro-regions seem to be partially consistent with the White Paper on Transport vision. However, the emphasis of the macro-regions on the development of maritime transport is somewhat omitted in the White Paper. Among the countries of both areas (EUSAIR, EUSBSR), estimates showed a statistically significant (p < 0.05) positive impact on the volume of loads transported by road transport. An increase in the volume loads by 1% resulted in an increase in air pollution by 0.446% (EUSAIR) and 0.728% (EUSBSR). The elasticity of air pollution, regarding loads’ road transport changes, was the highest compared to other transport modes in the studied areas. This proves the highest emissivity of road transport. In the EUSAIR countries, an increase by 1% of the volume of transport by railway resulted in a decrease in air pollution, with emissions of greenhouse gases decreasing by 0.063%. Considering the analyzed documentation, reports, strategies, and assumptions, it seems right to clearly emphasize the role of rail transport in the decarbonization of transport. According to the authors, mainly, this branch of transport can significantly reduce the emission of gases into the atmosphere and thus contribute to the so-called “green deal”. However, many activities must be undertaken for this to happen, not only investment ones. First of all, it is worth paying attention to the coherence of regional strategies with the European transport development plan contained in the White Paper.

19.
Semiconductor Science and Technology ; 37(5):7, 2022.
Article in English | Web of Science | ID: covidwho-1758594

ABSTRACT

Aluminum gallium nitride (AlGaN) plays an essential role in deep ultra-violet light emitting diodes and high electron mobility transistors etc. For example, 2 nm - 5 nm AlGaN nanofilms consist of the quantum wells in ultra-violet light emitting diodes, which have been attracting extensive attention since the rise of COVID 2019. Since most photons and heat are generated in these AlGaN nanofilms, the thermal properties of AlGaN nanofilms are strongly influenced by the heat dissipation of devices. In this paper, utilizing elastic theory and the Boltzmann transport equation, the phonon dispersion relations, density of states, specific heat capacities and thermal conductivities of 2 nm Al (delta) Ga1-delta N nanofilms with various delta are theoretically calculated at different temperatures. The thermal conductivity of nanofilm is significantly smaller than that of its bulk counterpart. In contrast with bulk AlGaN, due to the dominance of boundary scattering and alloy disorder scattering, the thermal conductivity of Al (delta) Ga1-delta N exhibits a similar dependence on Al concentration to bulk Al (delta) Ga1-delta N. Meanwhile, since the screening of Umklapp scattering, the saturation temperature of thermal conductivity is delayed from 50 to 100 K in bulks to about 300 K in nanofilms. The shrinkage of nanofilms' thermal conductivity is also slower than for bulks. We believe that our work will be helpful in controlling the self-heating effect of devices based on AlGaN nanofilms.

20.
SSRN; 2022.
Preprint in English | SSRN | ID: ppcovidwho-330581

ABSTRACT

This research investigates if consumers were less price sensitive to life necessities during the COVID-19 pandemic via a demand modeling system. Consumers' price sensitivity was explicitly quantified by the price elasticity of demand. Consumer behavior in nine categories of products considered as life necessities were studied in two non-overlapping time periods: a year before the onset of the COVID pandemic and a year following the initial panic buying caused by the declaration of the COVID pandemic. The changes in price elasticity of demand between the the two periods across the nine product categories were determined from the weekly sales data of a Dutch retailer. Using the proposed demand modeling system applied to available data, it was empirically found that the majority of essential food products were price inelastic, while the majority of non-food products were price elastic during the COVID period. Among the nine product categories, four categories were identified to have significantly different elasticities across the two time periods, while eight categories were observed to have practically smaller magnitudes in elasticities. These insights not only prove the usefulness of the proposed demand modeling system, but also provide valuable theoretical and managerial implications for retail business practitioners, particularly in pricing and inventory planning.

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