Search results for: forced convection

Authors: İrem Yetkin, Feray Maden, Seda Tosun, Yenal Akgün, Özgür Kilit, Koray Korkmaz, Gökhan Kiper, Mustafa Gündüzalp

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Forced migration, whether caused by conflicts or other factors, frequently places individuals in vulnerable situations, necessitating immediate access to shelter. To promptly address the immediate needs of affected individuals, temporary shelters are often established. These shelters are characterized by their adaptable and functional nature, encompassing lightweight and sustainable structural systems, rapid assembly capabilities, modularity, and transportability. The shelter design is contingent upon demand, resulting in distinct phases for different structural forms. A multi-phased shelter approach covers emergency response, temporary shelter, and permanent reconstruction. Emergency shelters play a critical role in providing immediate life-saving aid, while temporary and transitional shelters, which are also called “t-shelters,” offer longer-term living environments during the recovery and rebuilding phases. Among these, temporary shelters are more extensively covered in the literature due to their diverse inhabiting functions. The roles of emergency shelters and temporary shelters are inherently separate, addressing distinct aspects of sheltering processes. Given their prolonged usage, temporary shelters are built for greater durability compared to emergency shelters. Nonetheless, inadequacies in temporary shelters can lead to challenges in ensuring habitability. Issues like non-expandable structures unsuitable for accommodating large families, the use of short-term shelters that worsen conditions, non-waterproof materials providing insufficient protection against bad weather conditions, and complex installation systems contribute to these problems. Given the aforementioned problems, there arises a need to develop adaptive shelters featuring lightweight components for ease of transport, possess the ability for rapid assembly, and utilize durable materials to withstand adverse weather conditions. In this study, first, the state-of-the-art on temporary shelters is presented. Then, an adaptive temporary shelter composed of foldable plates is proposed, which can easily be assembled and transportable. The proposed shelter is deliberated upon its movement capacity, transportability, and flexibility. This study makes a valuable contribution to the literature since it not only offers a systematic analysis of temporary shelters utilizing kinetic systems but also presents a practical solution that meets the necessary design requirements.

Keywords: deployable structures, foldable plates, forced migration, temporary shelters

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Authors: Hyun-Woo Jun, Tae-Chul Jeong, Huai-Cong Liu, Ju Lee

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The paper presents the electromagnetic-thermal flow coupled analysis of permanent magnet synchronous motor (PMSM) which has cooling channel in stator core for forced air cooling. Unlike the general PMSM design, to achieve ohmic loss reduction for high efficiency, cooling channel actively used in the stator core. Equivalent thermal network model was made to analyze the effect of the formation of the additional flow path in the core. According to the shape and position changing of the channel design, electromagnetic-thermal coupled analysis results were reviewed.

Keywords: coupled problems, electric motors, equivalent circuits, fluid flow, thermal analysis

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Authors: Selma Bouasria, Mahi Abdelkader, Abbès Azzi, Herouz Keltoum

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This paper reports concept was used into the computational fluid dynamics (CFD) code cfx through user-defined functions to assess ventilation efficiency inside (forced-ventilation local). CFX is a simulation tool which uses powerful computer and applied mathematics, to model fluid flow situations for the prediction of heat, mass and momentum transfer and optimal design in various heat transfer and fluid flow processes to evaluate thermal comfort in a room ventilated (highly-glazed). The quality of the solutions obtained from CFD simulations is an effective tool for predicting the behavior and performance indoor thermo-aéraulique comfort.

Keywords: ventilation, thermal comfort, CFD, indoor environment, solar air heater

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Authors: Fizza Saghir

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Rohingyas are an ethnic minority of predominantly Buddhist-Myanmar. Living in ghettos in Rakhine, one of the poorest states of Myanmar, for decades, they have been marginalized, discriminated, deprived of the basic amenities and have faced ghastly violations of their rights- politically, socially, economically and culturally. In 2012, in violence that, erupted between ethnic Rakhine Buddhists and Rohingya Muslims, hundreds of Rohingyas were slayed and many more displaced. The state does not recognize them as ‘citizens’ and the military and police have constantly persecuted and pushed them to either migrate to other countries like India, Bangladesh or else die of deprivation. Amidst the deadly violence, Rohingya women are the most vulnerable. Many of them have faced sexual abuse and gender-based violence. Minimalistic to insignificant studies have been done on the plight of Rohingya women refugees in context of India. Thus, this paper focuses on psycho-social status of Rohingya women refugees settled in Delhi, India. The research study used both quantitative and qualitative methods. It was explorative in nature and used non-probability sampling, purposive sampling, in particular. A sample size of 30 Rohingya women refugees was interviewed out of the universe of 45 Rohingya refugee families living in Kalindi Kunj Refugee Camp of Delhi. Case studies were developed. The paper explores the psychological and social status of the respondents along with a deep understanding of their issues and concerns. Moreover, it assesses the impact of violence and migration on respondents. It was found that Rohingya women refugees are deeply and severely affected by a violent past, an insecure present and an uncertain future. Major problems they face in Delhi, India are finding employment, lack of identity cards to avail government services, language barrier, lack of health and education facilities. All they desire is peace and shelter in India. Besides, recommendations and suggestions have been given to various stakeholders of the forced mass migration of Rohingya refugees which includes, Government of Myanmar, Government of India, other bordering nations of Myanmar, international NGOs and media and the Rohingya community, itself. Only an immediate, peaceful and continuous dialogue process can help resolve the issue of exodus of Rohingyas. Countries, including India, must come together to help the Rohingyas who are in need of urgent humanitarian aid and assistance.

Keywords: dialogue process, ethnic minority, forced mass migration, impact of violence and migration, psycho-social status, Rohingya women refugees, sexual abuse

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Authors: Daniel Kliewe, Arno Kühn, Roman Dumitrescu, Jürgen Gausemeier

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This paper examines the system protection for cyber-physical systems (CPS). CPS are particularly characterized by their networking system components. This means they are able to adapt to the needs of their users and its environment. With this ability, CPS have new, specific requirements on the protection against anti-counterfeiting, know-how loss and manipulation. They increase the requirements on system protection because piracy attacks can be more diverse, for example because of an increasing number of interfaces or through the networking abilities. The new requirements were identified and in a next step matched with existing protective measures. Due to the found gap the development of new protection measures has to be forced to close this gap. Moreover a comparison of the effectiveness between selected measures was realized and the first results are presented in the paper.

Keywords: anti-counterfeiting, cyber physical systems, intellectual property (IP), knowledge management, system protection

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Authors: Steffen Schieweck, Johannes Dregger, Sascha Kaczmarek, Michael ten Hompel

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Logistics distributors face the issue of having to provide increasing service levels while being forced to reduce costs at the same time. Same-day delivery, quick order processing and rapidly growing ranges of articles are only some of the prevailing challenges. One key aspect of the performance of an intra-logistics system is how often and in which amplitude congestions and dysfunctions affect the processing operations. By gaining knowledge of the so called ‘performance availability’ of such a system during the planning stage, oversizing and wasting can be reduced whereas planning transparency is increased. State of the art for the determination of this KPI are simulation studies. However, their structure and therefore their results may vary unforeseeably. This article proposes a concept for the establishment of ‘certified’ and hence reliable and comparable simulation models.

Keywords: intra-logistics, performance availability, simulation, warehousing

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Authors: Kaltrina Kusari

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Displaced populations have received increasing attention, yet the experiences of return migrants remain largely hidden within social sciences. Existing research, albeit limited, suggests that policies which impact return migrants, especially those forced to return to their home countries, do not reflect their voices. Specifically, the United Nations Hight Commissioner for Refugees has adopted repatriation as a preferred policy solution, despite research which substantiates that returning to one’s home country is neither durable nor the end of the migration cycle; as many of 80% of returnees decide to remigrate. This one-size-fits-all approach to forced displacement does not recognize the impact of intersecting identity categories on return migration, thus failing to consider how ethnicity, gender, and class, among others, shape repatriation. To address this, this qualitative study examined the repatriation experiences of return migrant women from Kosovo and the role of social workers in facilitating return. In 2015, Kosovars constituted the fourth largest group of asylum seekers in the European Union, yet 96% of them were rejected. Additionally, since 1999 Kosovo has ranked among the top 10 countries of origin for return migrants. Considering that return migration trends are impacted by global power dynamics, this study relied on a postcolonial and transnational feminist framework to contextualize the mobility of displaced peoples in terms of globalization and conceptualize migration as a gendered process. Postcolonial and feminist theories suggest that power is partly operationalized through language, thus, Critical Discourse Analysis was used as a research methodology. CDA is concerned with examining how power, language, and discourses shape social processes and relationships of dominance. Data collection included interviews with 15 return migrant women (eight ethnic minorities and seven Albanian) and 18 service providers in Kosovo. The main findings illustrate that both returnee women and service providers rely on discourses which 1) challenge the voluntariness and sustainability of repatriation; 2) construct Kosovo as inferior to EU countries; and 3) highlight the impact of patriarchy and ethnic racism on return migration. A postcolonial transnational feminist analysis demonstrates that despite Kosovars’ challenges with repatriation, European Union countries use their power to impose repatriation as a preferred solution for Kosovo’s government. These findings add to the body of existing repatriation literature and provide important implications for how return migration might be carried out, not only in Kosovo but other countries as well.

Keywords: migration, gender, repatriation, transnational feminism

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Authors: Yong-Il Lee, Do-Yeon Hwang, Won-Seog Jeong, Duckshin Park

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Recently, because of the high-speed trains forced ventilation, it is important to control the ventilation. The ventilation is for controlling various contaminants, temperature, and humidity. The high-speed train route is straight to a destination having a high speed. And there are many mountainous areas in Korea. So, tunnel rate is higher then other country. KTX HVAC block off the outdoor air, when entering tunnel. So the high tunnel rate is an effect of ventilation in the KTX cabin. It is important to reduction rate in CO2 concentration prediction. To meet the air quality of the public transport vehicles recommend standards, the KTX cabin of CO2 concentration should be managed. In this study, the concentration change was predicted by CO2 prediction simulation in route to be opened.

Keywords: CO2 prediction, KTX, ventilation, infrastructure and transportation engineering

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Authors: Han-Taw Chen, Tzu-Hsiang Lin, Chung-Hou Lai

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This study applies the inverse method and three-dimensional CFD commercial software in conjunction with the experimental temperature data to investigate the heat transfer and fluid flow characteristics of the plate-fin heat sink in a rectangular closed enclosure. The inverse method with the finite difference method and the experimental temperature data is applied to determine the approximate heat transfer coefficient. Later, based on the obtained results, the zero-equation turbulence model is used to obtain the heat transfer and fluid flow characteristics between two fins. To validate the accuracy of the results obtained, the comparison of the heat transfer coefficient is made. The obtained temperature at selected measurement locations of the fin is also compared with experimental data. The effect of the height of the rectangular enclosure on the obtained results is discussed.

Keywords: inverse method, fluent, heat transfer characteristics, plate-fin heat sink

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Authors: Dara Singh, Keikhosrow Firouzbakhsh, Mohammad Taghi Ahmadian

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In this study, a validated 3D finite volume model of human eye is developed to study the fluid flow and heat transfer in the human eye at steady state conditions. For this purpose, discretized bio-heat transfer equation coupled with Boussinesq equation is analyzed with different anatomical, environmental, and physiological conditions. It is demonstrated that the fluid circulation is formed as a result of thermal gradients in various regions of eye. It is also shown that posterior region of the human eye is less affected by the ambient conditions compared to the anterior segment which is sensitive to the ambient conditions and also to the way the gravitational field is defined compared to the geometry of the eye making the circulations and the thermal field complicated in transient states. The effect of variation in material and boundary conditions guides us to the conclusion that thermal field of a healthy and non-healthy eye can be distinguished via computer simulations.

Keywords: bio-heat, boussinesq, conduction, convection, eye

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Authors: Jayahar Sivasubramanian

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Understanding laminar-turbulent transition process in hyper-sonic boundary layers is crucial for designing viable high speed flight vehicles. The study of transition becomes particularly important in the high speed regime due to the effect of transition on aerodynamic performance and heat transfer. However, even after many years of research, the transition process in hyper-sonic boundary layers is still not understood. This lack of understanding of the physics of the transition process is a major impediment to the development of reliable transition prediction methods. Towards this end, spatial Direct Numerical Simulations are conducted to investigate the instability waves generated by a localized disturbance in a hyper-sonic flat plate boundary layer. In order to model a natural transition scenario, the boundary layer was forced by a short duration (localized) pulse through a hole on the surface of the flat plate. The pulse disturbance developed into a three-dimensional instability wave packet which consisted of a wide range of disturbance frequencies and wave numbers. First, the linear development of the wave packet was studied by forcing the flow with low amplitude (0.001% of the free-stream velocity). The dominant waves within the resulting wave packet were identified as two-dimensional second mode disturbance waves. Hence the wall-pressure disturbance spectrum exhibited a maximum at the span wise mode number k = 0. The spectrum broadened in downstream direction and the lower frequency first mode oblique waves were also identified in the spectrum. However, the peak amplitude remained at k = 0 which shifted to lower frequencies in the downstream direction. In order to investigate the nonlinear transition regime, the flow was forced with a higher amplitude disturbance (5% of the free-stream velocity). The developing wave packet grows linearly at first before reaching the nonlinear regime. The wall pressure disturbance spectrum confirmed that the wave packet developed linearly at first. The response of the flow to the high amplitude pulse disturbance indicated the presence of a fundamental resonance mechanism. Lower amplitude secondary peaks were also identified in the disturbance wave spectrum at approximately half the frequency of the high amplitude frequency band, which would be an indication of a sub-harmonic resonance mechanism. The disturbance spectrum indicates, however, that fundamental resonance is much stronger than sub-harmonic resonance.

Keywords: boundary layer, DNS, hyper sonic flow, instability waves, wave packet

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Authors: Syukri Himran, Rustan Taraka, Anto Duma

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The aim of the study is to improve the understanding of latent and sensible thermal energy storage within a paraffin wax media by an array of cylindrical tubes arranged both in in-line and staggered layouts. An analytical and experimental study was carried out in a horizontal shell-and-tube type system during the melting process. Pertamina paraffin-wax was used as a phase change material (PCM), where as the tubes are embedded in the PCM. From analytical study we can obtain the useful information in designing a thermal energy storage such as : the motion of interface, amount of material melted at any time in the process, and the heat storage characteristic during melting. The use of staggered tubes is proposed as superior to in-line layout for thermal storage. The experimental study was used to verify the validity of the analytical predictions. From the comparisons, the analytical and experimental data are in a good agreement.

Keywords: latent, sensible, paraffin-wax, thermal energy storage, conduction, natural convection

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Authors: Fariyal Mir

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The largest minority group over Pakistan lives in the farthest region of KPK, Chitral, which enclosed all its people in one closet despite their diversity. Chitral is considered a tourist hub and piece of paradise on earth. The major attraction of Chitral is the Kalash valley, which is also known as the homeland of kafir or 'weavers of the black robes'. Kalash people are counted as the primitive pagan tribe who practice culture, beliefs, and a lifestyle which dated beyond and distinct from the rest of the region. Their religious belief is known to be as 'animism', which means that objects, places, and creatures all possess a distinct spiritual essence. They also believe that nature plays a highly significant and spiritual role in their daily life. As they have their different festivals like (a) Chilam Josh: celebrated in May to welcome spring, (b) Uchaw: which is observed in late August to ensure good crops of wheat, (c) Chanmos: which is being observed in December for more than two weeks, grand festival and is celebrated to welcome New Year. Their concept of purity and impurity is also very traditional and part of their religious belief as well. They used to call the man as pure 'Oshniru' (pure, holy) and woman as impure 'Chetu' (dirty, polluted, or contaminated). This study is based on ethnomethodology, which focuses on the way people make sense of their daily life. Their unique belief system connects them with the descendants of the armies of Alexander the Great, who called the Hindu Kush 'Parapamisus', meaning mountains over which eagles can fly. With time, their cultural system was molded into many ways, and the same is going on with the true beauty of Chitral in the form of conversion to Islam and adaptation of modern lifestyle. Ethnomethodology also supports this, that people are always good in their original form so they can be called the true representatives of their origin and cultural identity. It also argues that human society is based on the method of achieving and displaying not on the imposition of others' order and laws. So, everybody is obliged to respect and not to harm the beliefs and culture of all other human fellows. Some historians believe that these Kalash people are from Afghanistan and their origin is Saim which is known as Thailand, but those Kalash tribe from Afghanistan were forced to embrace Islam and only Pakistan keeps these people who own unique cultural values, ornaments and entire culture. Kalasha culture has been listed by UNESCO for consideration as World Heritage. It is necessary to save these people from the cultural invasion caused by modernity, forced religious conversion to maintain the pluralistic diversity of our country.

Keywords: Chitral, cultural identity, ethnomethodology, Kalasha culture

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Authors: Lu Liao

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This paper studies the impact of private labels on the advertising incentives of national brands. The worldwide expansion of private labels over the past two decades not only transformed the choice sets of consumers but also forced manufacturers of national brands to design new marketing strategies to maintain their market positions. This paper first develops a consumer demand model that incorporates spillover effects of advertising for antacids, including private labels and finds positive spillovers of national brands’ advertising on demand for private label antacids. With the demand estimates, it provides a simulation for the equilibrium prices and advertising levels for leading national brands in a counterfactual where private labels are eliminated to quantify national brands’ advertising incentives as a response to the rise of private labels.

Keywords: advertising, private label, marketing, demand

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Authors: Saeed Mohammadirad

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During the first commitment period of the Kyoto Protocol, many developed countries were forced to restrict carbon emissions. Although Iran was one of the countries of Kyoto protocol, due to some special conditions, it was not required to restrict its carbon emissions. Flexible mechanisms were developed to assist countries responsible for reducing their carbon emissions, and regulated carbon markets were introduced. Carbon credits which are provided by organizations in countries with no responsibility to restrict their carbon emissions are traded in voluntary markets. This study focuses on how to measure and report the carbon allowances and carbon credits from accounting view point under both regulated and voluntary markets.

Keywords: carbon credits, carbon markets, accounting, flexible mechanisms

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Authors: A. B. Disu, M. S. Dada

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This study was conducted to investigate two dimensional heat transfer of a free convective-radiative MHD (Magneto-hydrodynamics) flow with temperature dependent viscosity and heat source of a viscous incompressible fluid in a porous medium between two vertical wavy walls. The fluid viscosity is assumed to vary as an exponential function of temperature. The flow is assumed to consist of a mean part and a perturbed part. The perturbed quantities were expressed in terms of complex exponential series of plane wave equation. The resultant differential equations were solved by Differential Transform Method (DTM). The numerical computations were presented graphically to show the salient features of the fluid flow and heat transfer characteristics. The skin friction and Nusselt number were also analyzed for various governing parameters.

Keywords: differential transform method, MHD free convection, porous medium, two dimensional radiation, two wavy walls

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Authors: Tareq N. Issa

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The main pressuring challenges of global competition and high returns have forced businesses to shift their strategic competitive advantage from physical distribution management to integrated logistics management, finally moving into supply chain management. Conventionally, corporate profitability is a function of cost, capital employed, revenue and customer service. This article gives an insight into the effect of supply chain management on each of the above variables. It investigates the impact of the changing levels/ effects of these variables on corporate profitability and the means of measuring supply chain financial effectiveness. Information technology tools form the basis for supply chain optimal performance through alignment of supply chain systems in this ever increasing complexity in business decisions.

Keywords: corporate profitability, sypply chain systems, business decisions, competitive advanage

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Authors: Shubham Jaiswal

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During modeling of transport phenomena in porous media, many nonlinear partial differential equations (NPDEs) encountered which greatly described the convection, diffusion and reaction process. To solve such types of nonlinear problems, a reliable and efficient technique is needed. In this article, the numerical solution of NPDEs encountered in porous media is derived. Here Jacobi collocation method is used to solve the considered problems which convert the NPDEs in systems of nonlinear algebraic equations that can be solved using Newton-Raphson method. The numerical results of some illustrative examples are reported to show the efficiency and high accuracy of the proposed approach. The comparison of the numerical results with the existing analytical results already reported in the literature and the error analysis for each example exhibited through graphs and tables confirms the exponential convergence rate of the proposed method.

Keywords: nonlinear porous media equation, shifted Jacobi polynomials, operational matrix, spectral collocation method

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Authors: Agnetha Schuchardt, Jennifer Hartmann, Laura Schulte, Roman Peperhove, Lars Gerhold

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If critical infrastructures fail, even for a short period of time, it can have significant negative consequences for the affected population. This is especially true for the food sector that is strongly interlinked with other sectors like the power supply. A blackout could lead to several cities being without food supply for numerous days, simply because cash register systems do no longer work properly. Following the public opinion, securing the food supply in emergencies is considered a task of the state, however, in the German context, the key players are private enterprises and private households. Both are not aware of their responsibility and both cannot be forced to take any preventive measures prior to an emergency. This problem became evident to officials and politicians so that the law covering food security was revised in order to include private stakeholders into mitigation processes. The paper will present a scientific review of governmental and regulatory literature. The focus is the inclusion of the food industry through a law reform and the challenges that still exist. Together with legal experts, an analysis of regulations will be presented that explains the development of the law reform concerning food security and emergency storage in Germany. The main findings are that the existing public food emergency storage is out-dated, insufficient and too expensive. The state is required to protect food as a critical infrastructure but does not have the capacities to live up to this role. Through a law reform in 2017, new structures should to established. The innovation was to include the private sector into the civil defense concept since it has the required knowledge and experience. But the food industry is still reluctant. Preventive measures do not serve economic purposes – on the contrary, they cost money. The paper will discuss respective examples like equipping supermarkets with emergency power supply or self-sufficient cash register systems and why the state is not willing to cover the costs of these measures, but neither is the economy. The biggest problem with the new law is that private enterprises can only be forced to support food security if the state of emergency has occurred already and not one minute earlier. The paper will cover two main results: the literature review and an expert workshop that will be conducted in summer 2018 with stakeholders from different parts of the food supply chain as well as officials of the public food emergency concept. The results from this participative process will be presented and recommendations will be offered that show how the private economy could be better included into a modern food emergency concept (e. g. tax reductions for stockpiling).

Keywords: critical infrastructure, disaster control, emergency food storage, food security, private economy, resilience

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Authors: Saeid Jalilzadeh, Majid Pakdel

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The customer demand for better power quality and higher reliability has forced the power industry to use distributed generations (DGs) such as wind power and photo voltaic arrays. Islanding is a phenomenon occurs when a power grid becomes electrically isolated from the power system and the distribution system is energized by distributed generators. It is necessary to disconnect all distributed generators immediately after islanding occurrence. Therefore a DG system should have the capability to detect islanding phenomena. In this paper, a novel micro controller based relay for anti-islanding protection of a typical DG system is proposed. The simulation results using Proteus software verify the proper operation and effectiveness of the proposed protective relay.

Keywords: islanding, distributed generation (DG), protective relay, micro controller, proteus software

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Authors: Itze Coronel Salomon

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The rise of organized crime and violence related to drug cartels in Mexico has created serious challenges for the authorities to provide security to those who live within its borders. However, to achieve a significant improvement in security is absolute respect for fundamental human rights by the authorities. Irregular migrants in Mexico are at serious risk of abuse. Research by Amnesty International as well as reports of the NHRC (National Human Rights) in Mexico, have indicated the major humanitarian crisis faced by thousands of migrants traveling in the shadows. However, the true extent of the problem remains invisible to the general population. The fact that federal and state governments leave no proper record of abuse and do not publish reliable data contributes to ignorance and misinformation, often spread by the media that portray migrants as the source of crime rather than their victims. Discrimination and intolerance against irregular migrants can generate greater hostility and exclusion. According to the modus operandi that has been recorded criminal organizations and criminal groups linked to drug trafficking structures deprive migrants of their liberty for forced labor and illegal activities related to drug trafficking, even some have been kidnapped for be trained as murderers . If the victim or their family cannot pay the ransom, the kidnapped person may suffer torture, mutilation and amputation of limbs or death. Migrant women are victims of sexual abuse during her abduction as well. In 2011, at least 177 bodies were identified in the largest mass grave found in Mexico, located in the town of San Fernando, in the border state of Tamaulipas, most of the victims were killed by blunt instruments, and most seemed to be immigrants and travelers passing through the country. With dozens of small graves discovered in northern Mexico, this may suggest a change in tactics between organized crime groups to the different means of obtaining revenue and reduce murder profile methods. Competition and conflict over territorial control drug trafficking can provide strong incentives for organized crime groups send signals of violence to the authorities and rival groups. However, as some Mexican organized crime groups are increasingly looking to take advantage of income and vulnerable groups, such as Central American migrants seem less interested in advertising his work to authorities and others, and more interested in evading detection and confrontation. This paper pretends to analyze the introduction of this new trend of kidnapping migrants for forced labors by drug cartels in Mexico into the forms of contemporary slavery and its implications.

Keywords: international law, migration, transnational organized crime

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Authors: Maria Terezinha Santos Leite Neta, Mônica Silva de Jesus, Hannah Caroline Santos Araujo, Rafael Donizete Dutra Sandes, Raquel Anne Ribeiro Dos Santos, Narendra Narain

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Mango is one of the most consumed and appreciated fruits in the world, mainly due to its peculiar and characteristic aroma. Since the fruit is perishable, it requires conservation methods to prolong its shelf life. Mango cubes were dehydrated at 40°C, 50°C and 60°C and by lyophilization, and the effect of these processes was investigated on the physicochemical characteristics (color and texture) of the products and monitoring of the main volatile compounds for the mango aroma. Volatile compounds were extracted by the SPME technique and analyzed in GC-MS system. Drying temperature at 60°C and lyophilization showed higher efficiency in retention of main volatile compounds, being 63.93% and 60.32% of the total concentration present in the fresh pulp, respectively. The freeze-drying process also presented features closer to the fresh mango in relation to color and texture, which contributes to greater acceptability.

Keywords: mango, freeze drying, convection drying, aroma, GC-MS

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Authors: Aiman Alshare, Sahar Qaadan

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A curvature dependent force correction algorithm for planning force controlled grinding process with off-line programming flexibility is designed for ABB industrial robot, in order to avoid the manual interface during the process. The machining path utilizes a spline curve fit that is constructed from the CAD data of the workpiece. The fitted spline has a continuity of the second order to assure path smoothness. The implemented algorithm computes uniform forces normal to the grinding surface of the workpiece, by constructing a curvature path in the spatial coordinates using the spline method.

Keywords: ABB industrial robot, grinding process, offline programming, CAD data extraction, force correction algorithm

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Authors: Ali Reza Tahavvor, Saeed Hosseini, Afshin Karimzadeh Fard

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In this paper the effect of wall waviness of side walls in a two-dimensional wavy enclosure is numerically investigated. Two vertical wavy walls and straight top wall are kept isothermal and the bottom wall temperature is higher and spatially varying with cosinusoidal temperature distribution. A computational code based on Finite-volume approach is used to solve governing equations and SIMPLE method is used for pressure velocity coupling. Test is performed for several different numbers of undulations. The Prandtl number was kept constant and the Ra number denotes that the flow is laminar. Temperature and velocity fields are determined. Therefore, according to the obtained results a correlation is proposed for average Nusselt number as a function of number of side wall waves. The results indicate that the Nusselt number is highly affected by number of waves and increasing it decreases the wavy walls Nusselt number; although the Nusselt number is not highly affected by surface waviness when the number of undulations is below one.

Keywords: cavity, natural convection, Nusselt number, wavy wall

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Authors: Clarinda Vitorino Nhangumbe, Ercília Sousa

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Weather derivatives are financial products used to cover non catastrophic weather events with a weather index as the underlying asset. The rainfall weather derivative pricing model is modeled based in the assumption that the rainfall dynamics follows Ornstein-Uhlenbeck process, and the partial differential equation approach is used to derive the convection-diffusion two dimensional time dependent partial differential equation, where the spatial variables are the rainfall index and rainfall depth. To compute the approximation solutions of the partial differential equation, the appropriate boundary conditions are suggested, and an explicit numerical method is proposed in order to deal efficiently with the different choices of the coefficients involved in the equation. Being an explicit numerical method, it will be conditionally stable, then the stability region of the numerical method and the order of convergence are discussed. The model is tested for real precipitation data.

Keywords: finite differences method, ornstein-uhlenbeck process, partial differential equations approach, rainfall derivatives

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Authors: Nicolas Thiers, Romain Gers, Olivier Skurtys

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In this work, we study numerically the effect of a thermal perturbation on the heat transfer in a rectangular differentially heated cavity of aspect ratio 4, filled by air. In order to maintain the center symmetry, the thermal perturbation is imposed by a square wave at both active walls, at the same relative position of the hot or cold boundary layers. The influences of the amplitude and the vertical location of the perturbation are investigated. The air flow is calculated solving the unsteady Boussinesq-Navier-Stokes equations using the PN - PN-2 Spectral Element Method (SEM) programmed in the Nek5000 opencode, at RaH= 9x107, just before the first bifurcation which leads to periodical flow. The results show that the perturbation has a major impact for the highest amplitude, and at about three quarters of the cavity height, upstream, in both hot and cold boundary layers.

Keywords: direct numerical simulation, heat transfer enhancement, localized thermal perturbations, natural convection, rectangular differentially-heated cavity

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Authors: Rajan Ghimire

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One of the diseases caused by the coronavirus shook the whole world. This situation challenged the education system across the world and compelled educators to shift to an online mode of teaching. Many academic institutions that were persistent to keep their traditional pedagogical approach were also forced to change their teaching methods. This study aims to assess science education students' experiences and perceptions of this global issue, especially on the science teaching and learning process. The study is based on qualitative research and through in-depth interviews with respondents and data is analyzed. Online distance teaching and learning processes meet the requirements of students who cannot or prefer not to participate in conventional classroom settings. But there are some challenges for the students and teachers in the science teaching learning process. This study recommends some points to all stakeholders.

Keywords: electronic devices, internet, online and distance learning, science education, educational policy

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Authors: Xiaolin Tang, Wei Yang, Xiaoan Chen

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The research described in this paper was aimed at exploring the torsional vibration characteristics of a power-split hybrid powertrain equipped with a dual mass flywheel. The dynamic equations of governing torsional vibration for this hybrid driveline are presented, and the multi-body dynamic model for the powertrain is established with the software of ADAMS. Accordingly, different parameters of dual mass flywheel are investigated by forced vibration to reduce the torsional vibration of hybrid drive train. The analysis shows that the implementation of a dual mass flywheel is an effective way to decrease the torsional vibration of the hybrid powertrain. At last, the optimal combination of parameters yielding the lowest vibration is provided.

Keywords: dual mass flywheel, hybrid electric vehicle, torsional vibration, powertrain, dynamics

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Authors: M. J. Uddin, M. M. Rahman

Abstract:

The unsteady convective heat transfer flow of nanofluids in a half circular-annulus shape enclosure using nonhomogeneous dynamic model has been investigated numerically. The round upper wall of the enclosure is maintained at constant low temperature whereas the bottom wall is heated by three different thermal conditions. The enclosure is permeated by a uniform magnetic field having variable orientation. The Brownian motion and thermophoretic phenomena of the nanoparticles are taken into account in model construction. The governing nonlinear momentum, energy, and concentration equations are solved numerically using Galerkin weighted residual finite element method. To discover the best performer, the average Nusselt number is demonstrated for different types of nanofluids. The heat transfer rate for different flow parameters, positions of the annulus, thicknesses of the half circular-annulus and thermal conditions is also exhibited.

Keywords: nanofluid, convection, semicircular-annulus, nonhomogeneous dynamic model, finite element method

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Authors: Seyed Sadegh Naseralavi

Abstract:

This paper presents a Kernel parallelization equation for damage identification in structures under unknown periodic excitations. Herein, the dynamic differential equation of the motion of structure is viewed as a mapping from displacements to external forces. Utilizing this viewpoint, a new method for damage detection in structures under periodic loads is presented. The developed method requires only two periods of load. The method detects the damages without finding the input loads. The method is based on the fact that structural displacements under free and forced vibrations are associated with two parallel subspaces in the displacement space. Considering the concept, kernel parallelization equation (KPE) is derived for damage detection under unknown periodic loads. The method is verified for a case study under periodic loads.

Keywords: Kernel, unknown periodic load, damage detection, Kernel parallelization equation

Procedia PDF Downloads 257