Objectives: Specific work processes and management structures that contribute to high rates of occupational illness and injury in agricultural industries are not well described in academic literature. This qualitative study of work organization in the U.S. fresh tomato industry investigates how work processes and management structures impact tomato workers’ occupational health. Methods: After conducting literature review and key informant interviews, semi-structured interviews and focus groups were conducted with 36 individuals with experience working in the U.S. fresh tomato industry. Interviews and focus groups were audio-recorded, transcribed, coded, and analyzed using a modified grounded theory approach. Results: These data indicate that participants endured income insecurity and hazardous supervisory practices, including wage theft, retaliation, intimidation, and humiliation, that put them at risk of preventable illness and injury. Support from workers’ organizations and health-conscious supervisory practices helped mitigate some of these occupational hazards. Conclusion: Participants’ adverse work experiences may be considered sequelae of workers’ lack of job control and positions of socioeconomic structural vulnerability. Other aspects of tomato work organization, including health-conscious supervisory practices and the involvement of workers’ organizations, indicate that modifying work organization to better safeguard health is possible. Such modifications present compelling opportunities for employers, employees, organizations, community and government leaders, and health care professionals to help create healthier occupational environments for tomato workers.

Cooperative transmission involves the simultaneous transmission by a group of devices, alldevices sending the same data. The devices may use sidelink (SL) to share data prior to thejoint transmission. Cooperative transmission helps improve network coverage since it can usethe combined transmission power of all devices in a group, whereas single-hop transmissionby one device is limited to its own maximum uplink power. Cooperative transmission aim is toimprove the network coverage of devices involved. The cooperative transmission solutioncomprisestwo steps. The first step is when a device (source device) in the group wants to senddata in the UL and then transmits data via SL to the devices in a created group. In the secondstep, all users simultaneously transmit the data in the UL to the base station the group isassigned to.This master thesis studies both the performance in the uplink (UL), comparing cooperativewith direct transmission, and how to reduce the power consumption of the devices involvedin the cooperative transmission.A power consumption model was developed to analyze the energy consumption, both viaanalytical and simulations methods. The analytical results show that cooperative transmissioncan reduce energy consumption by 7% compared to direct transmission. An algorithm wasproposed for cooperative transmission, which helps reduce energy consumption by 31%.Furthermore, the performance of cooperative transmissions was also studied using a systemsimulator. The results shows that the UL total bit rate increases with cooperative transmissionand is proportional to the number of users in the group. The total bit rate increased by 57%for a group with five users and for a group of 10 the increase was 107% (with a carrierfrequency of 3GHz). Different scenarios were simulated, and the increase in total bit ratevaries from 50-150%. Cooperative transmission involves the simultaneous transmission by a group of devices, alldevices sending the same data. The devices may use sidelink (SL) to share data prior to thejoint transmission. Cooperative transmission helps improve network coverage since it can usethe combined transmission power of all devices in a group, whereas single-hop transmissionby one device is limited to its own maximum uplink power. Cooperative transmission aim is toimprove the network coverage of devices involved. The cooperative transmission solutioncomprisestwo steps. The first step is when a device (source device) in the group wants to senddata in the UL and then transmits data via SL to the devices in a created group. In the secondstep, all users simultaneously transmit the data in the UL to the base station the group isassigned to.This master thesis studies both the performance in the uplink (UL), comparing cooperativewith direct transmission, and how to reduce the power consumption of the devices involvedin the cooperative transmission.A power consumption model was developed to analyze the energy consumption, both viaanalytical and simulations methods. The analytical results show that cooperative transmissioncan reduce energy consumption by 7% compared to direct transmission. An algorithm wasproposed for cooperative transmission, which helps reduce energy consumption by 31%.Furthermore, the performance of cooperative transmissions was also studied using a systemsimulator. The results shows that the UL total bit rate increases with cooperative transmissionand is proportional to the number of users in the group. The total bit rate increased by 57%for a group with five users and for a group of 10 the increase was 107% (with a carrierfrequency of 3GHz). Different scenarios were simulated, and the increase in total bit ratevaries from 50-150%.

ual-three phase permanent magnet synchronous motors (DTP-PMSM) are becom ing more popular in the automotive field. Their potential to increase the reliability and efficiency of the vehicle makes them an attractive replacement for the three phase alternative. However, the increased number of phases makes the control of the machine more complex. As a result, conventional controllers can see reduced perfor mance, especially at high speeds and torques. Currently, with the increased process ing power of modern micro-controllers and field-programmable gate arrays (FPGA), many researchers are investigating whether finite-control set model predictive control (FCS-MPC) can be a suitable alternative. FCS-MPC is simple to implement and can achieve a better dynamic performance when compared to other controllers. Furthermore, the algorithm can be augmented for specific optimization goals and non-linearities to the system, which gives the designer creativity in improving the system response. However, Model-Predictive Control suffers from a variable switching frequency as well as reduced steady-state performance. It generally has increased current ripple in the phase currents. This thesis presents a method of reducing the steady-state ripples in FCS-MPC by introducing the use of virtual-flux in the model equations, the incremental model, and a dynamic vector search-space. All three of these applications make FCS-MPC have a iv significantly improved steady-state performance when compared to the conventional algorithm, while still keeping the benefit of the improved dynamic response. The benefits of the proposed techniques techniques are verified through simulation as well as on an experimental setup. / Thesis / Master of Applied Science (MASc)

No description available.

The Multiple Remote Tower Center concept (mRTC) is a cutting edge project which allows one air traffic control officer (ATCO) to be in charge of multiple remotely situated airports simultaneously. When implemented, it will revolutionise how air traffic is managed at smaller airports and allow for increased efficiency and decreased operational costs. Consequently, at the time of writing a lot of effort is going into evaluating this new way of air traffic management from a safety perspective. Air traffic management has been defined as an issue maintaining situational awareness and exercising control. This thesis aims to investigate how the phenomenon target fascination affects the ATCOs ability to exercise control over its controlled airspace and maintain its situation awareness. It does so by creating a baseline scenario of work in a mRTC, and then comparing the ATCOs performance in the baseline scenario with its performance in the same corresponding scenario, but with elements of target fascination introduced. The differences in the scenarios are analysed using the Contextual Control Model, the Extended Control Model and a holistic framework for studying situation awareness. The analysis shows that target fascination does affect the ATCOs ability to maintain control, but not radically so, and only for a short period of time. The target fascination forces the ATCO to rely on information in the immediate environment to a higher degree than during regular work, as opposed to making decisions based on a holistic understanding of the situation and high level goals. However, once the understanding of the situation have been re-established, the level of control quickly returns to normal levels. Situation awareness is thus a key concept in maintaining control. The situation awareness analysis show that target fascination affects situation awareness by causing the ATCOs understanding of the situation to become outdated without the ATCOs knowledge. Because of this, there may be developments in the situation that the ATCO is not aware of, which hinders it from acting as it normally would. In some cases an intervention from an external actor or element may be necessary to break the fascination and re-establish the ATCOs understanding for the situation. As soon as the fascination is broken, the ATCO quickly takes steps to re-establish its situation awareness and return to normal operations.

No description available.

Information security is of utmost concern in a multiuser environment. The importance of security is felt much more with the widespread use of distributed database. Information is by itself a critical resource of an enterprise and thus the successful operation of an enterprise demands that data be made accessible only by authorized users and that the data be made to reflect the state of the enterprise. Since many databases are online, accessed by multiple users concurrently, special mechanisms are needed to insure integrity and security of relevant information, This thesis describes a model for computer database security that supports a wide variety of security policies. The terms security policies and security mechanism are presented in Chapter I. The interrelated topics of security and integrity are discussed in some detail. The importance and means of insuring security of information is also presented in this chapter. In Chapter 2, the work done In the field of Computer Security and related topic has been presented. In general computer security models could be classified broadly under the two categories. (1) Models based on Access Control Matrix and (2) Models based on Information Flow Control. The development of the models baaed on the above two schemes as also the policies supported by some of the schemes are presented in this chapter. A brief description of the work carried out in database security as aim the definition of related terns are given in Chapter 3. The interrelationship between the operating system security and database security is also presented in this chapter. In general the database security mechanism depends on the existing operating system. The database security mechanism are thus only as strong as the underlying operating system on which it is developed. The various schemes used for implementing database security such as access controller and capability lists are described in this chapter. In Chapter 4, a model for database security has been described. The model provides for: (a) Delegation of access rights by a user and (b) Revocation of access rights previously granted by a user. In addition, algorithms for enforcing context dependent and content dependent rules are provided in this cheer. The context-dependent rules are stored in the form of elements of a bit matrix. Context-dependent rules could then be enforced by suitably manipulating the bit matrix and interpreting the value of me elements of the matrix, The major advantage of representing the rules using bit matrices is that the matrix itself could be maintalnet3 in main memory. The time taken to examine if a user is authorized to access an object is drastically reduced because of the reduced time required to inspect main memory. The method presented in this chapter, in addition to reducing the time requirement for enforcing security also presents a method for enforcing decentralized authorization control, a facility that is useful in a distributed database environment. Chapter 5 describes a simulation method that is useful for comparing the various security schemes. The tasks involved in the simulation are – 1. Creation of an arrival (job). 2. Placing the incoming job either in the wait queue or in the run state depending on the type of access needed for: the object. 3. Checking that the user on whose behalf the job is being executed is authorized to access the object in the mode requested. 4. Checking for the successful completion of the job and termination of the job. 5. Collection of important parameters such as number of jobs processed, average connect time. Simulation was carried out for timing both the access controller scheme and bit matrix scheme, The results of the simulation run bear the fact that the bit matrix scheme provides a faster method Six types of access were assumed to be permissible, three of the access types requiring shared lock and the rest requiring exclusive locks on the objects concerned, In addition the only type of operation allowed was assumed to be for accessing the objects. It is be noted that the time taken to check for security violation is but one of the factors for rating the security system. In general, various other factors such as cost of implementing the security system, the flexibility that offers enforcing security policies also have to be taken into account while comparing the security systems. Finally, in Chapter 6, a comparison of the security schemes are made. In conclusion the bit matrix approach is seen to provide the following features. (a) The time required to check if an access request should be honoured is very small. (b) The time required to find a11 users accessing an object viz, accountability is quite small. (c) The time required to find all objects accessible by a user is also quite small. (dl The scheme supports both decentralized and centralized authorization control. (e) Mechanism for enforcing delegation of access rights and revocation of access rights could be built in easily. ( f ) The scheme supports content-dependent, context-dependent controls and also provides a means for enforcing history-dependent control. Finally, some recommendations for further study in the field of Computer Database Security are presented.

<p>The purpose of the project, which led to this thesis, was to investigate the possible effects different horizontal Fields of View (FoV) have on driving performance when driving at night with a Vision Enhancement System (VES). The FoV chosen to be examined were 12 degree and 24 degree FoV, both displayed on a screen with the horizontal size of 12 degree FoV. This meant that the different conditions of FoV also had different display ratios 1:1 and 1:2. No effort was made to separate these parameters. </p><p>A simulator study was performed at the simulator at IKP, Linköping University. Sixteen participants in a within-group design participated in the study. The participants drove two road sections; one with a 12 degree FoV and the other with a 24 degree FoV. During each section four scenarios were presented in which the participants passed one of three types of objects; a moose, a deer or a man. In each section, two of the objects stood right next to the road and two were standing seventeen meters to the right of the road. As the drivers approached the objects standing seventeen meters to the right of the road, the objects moved out of the VES when the vehicle was 200 meters in front of the object with a 12 degree FoV. The objects could be seen with the naked eye when the vehicle was 100 meters in front of the object. When the drivers approached the objects with a 24degree FoV the objects moved out of the VES display when it was possible to see them unaided. </p><p>Results show that a 24 degree FoV displayed with a 1:2 ratio gives the drivers improved anticipatory control, compared to a 12 degree FoV displayed with a 1:1 ratio. The participants with a broader FoV were able to make informed decisions whereas with a narrow FoV some participants started to reaccelerate when they could not see an object. Results also show that any difference in recognition distance that may exist between a 12 degree and a 24 degree camera angle displayed in a 12 degree FoV display do not seem to have any adverse effect on the quality of driving.</p>

Syftet med studien var att undersöka samband mellan personlighetsdimensioner och upplevd stress på arbetsplatser utifrån fem-faktormodellen samt krav-kontrollmodellen. 128 deltagare deltog i enkätundersökningen; 58 män och 66 kvinnor mellan åldern 20-69 år. Studien var en tvärsnittsstudie med självskattningsfrågor och urvalet gjordes genom ett bekvämlighetsurval. Enkäterna besvarades på arbetsplatser i Örebro, Eskilstuna, Västerås och Stockholm. Tidigare forskning påvisar samband mellan personlighet och stress, men få undersöker detta utifrån krav-kontroll-stödmodellen. Föreliggande studie undersöker detta utifrån graden av krav och kontroll. T-test visade skillnader utifrån kön, envägs ANOVA visade skillnader i yrkestitel och ålder. Korrelationsanalyser visade positivt samband mellan krav och upplevd stress samt negativt samband mellan kontroll och upplevd stress. Resultatet visade positivt samband mellan agreeableness, openness, conscientiousness och krav samt positivt samband mellan openness och kontroll. / The purpose of the study was to examine correlations between personality traits and perceived stress at work places based upon the Five Factor model and demand-control model. 128 participants attended; 58 men and 66 women aged 20-69 years. The study was cross-sectional with self-report measures and convenience sampling. Surveys were answered at work places in Örebro, Eskilstuna, Västerås and Stockholm. Previous research show correlations between personality and stress, but few examine this through the demand-control-support model. Present study examine this through the demand-control model. T-test showed differences between gender, one-way ANOVA showed differences in occupation and age. There was a positive correlation between demand and perceived stress and a negative correlation between control and perceived stress. The results showed positive correlations between agreeableness, openness, conscientiousnness and demand, positive correlations between openness and control.

O modelo demanda e controle de Karasek, elaborado na década de 1970, postula que os trabalhadores expostos a situações de alta exigência no trabalho, decorrente da combinação entre altas demandas psicológicas e baixo controle sobre o processo de trabalho, tem maior risco de apresentar eventos em saúde relacionados ao estresse, em particular doenças cardiovasculares. Os objetivos desta tese incluíram: avaliar propriedades psicométricas do instrumento Demand-Control-Support Questionnaire (DCSQ) e conduzir uma meta-análise dos estudos publicados sobre a associação entre alta exigência no trabalho e hipertensão arterial. Três artigos foram elaborados. O primeiro artigo avaliou a validade dimensional e consistência interna da versão brasileira do instrumento DCSQ, quando aplicado a trabalhadores de um hospital e nove restaurantes no Rio de Janeiro. O segundo artigo comparou as propriedades psicométricas do DCSQ no contexto dos trabalhadores de hospital no Brasil e na Suécia. O terceiro artigo apresentou uma meta-análise dos estudos de associação entre alta exigência no trabalho e hipertensão arterial. Os resultados evidenciaram que o instrumento DCSQ tem estrutura tridimensional e equivalente nas versões brasileira e sueca (original), representada por demandas psicológicas, uso de habilidades e autonomia para a decisão. O modelo de melhor ajuste excluiu a dimensão apoio social no trabalho e o item trabalho repetitivo (uso de habilidades). A meta-análise revelou que os estudos foram heterogêneos, a população-alvo foi restrita a países da Europa, EUA e Japão, sem evidência de associação entre alta exigência no trabalho, demanda e controle, e hipertensão arterial. / Proposed in the 1970s, the demand control model stated that workers in high strain jobs, a combination of high levels of psychological demands and low levels of control, have an increased risk of stress-related outcomes, particularly cardiovascular diseases. The aim of this thesis is to evaluate the psychometric properties of the Demand-Control-Support Questionnaire (DCSQ) and to conduct a meta-analysis of published studies about the association of job strain and hypertension. Three articles were presented. The first article evaluated the dimensional validity and internal consistency of the Brazilian version of DCSQ, when applied to hospital and restaurant workers in Rio de Janeiro. The second article compared the psychometric properties of the Swedish and Brazilian versions of DCSQ, when applied to hospital workers. The third article presented a meta-analysis of the association studies of job strain and hypertension. The results evidenced a three-factor structure of the DCSQ, which was equivalent in the Brazilian and Swedish versions and closely related to psychological demands, skill discretion and decision authority dimensions. The best fit model was achieved by excluding the social support at work dimension and the item repetitive work (skill discretion). The meta-analysis revealed no association between high strain, and related dimensions, and hypertension in samples restricted to European countries, USA and Japan, in which heterogeneity between studies was evidenced.