| 1. |
- Abid, Muhammad, 1981-
(författare)
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Global Supply Chain Design : Exploring configurational and coordination factors
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis addresses the topic of global supply chain design. One major challenge concerns how to manage the tension between separation and integration pertaining to the localization of business activities. In this regard Ferdows (2008) worked to create two new production network models (rooted production network and footloose production network). Earlier studies have highlighted the choices that are involved in the network of facilities but lack in providing a comprehensive picture in terms of both configurational and coordination factors that govern the design of global supply chain. There is a need for a conceptual model where factors affecting the design process of a global supply chain can be applied. Two main research questions have been addressed in this study. First, exploring and identifying the factors affecting global supply chain design. Second, investigating the factors that influence the position on the spectrum of rooted and footloose supply chain design. A literature review analysis and multi-case studies have been performed for this study in order to explore the factors. The companies were selected in order to reflect upon the two types of network, i.e., rooted and footloose. The primary data were selected through interviews with the managers.This study highlighted that there are many factors that affect configurational and coordination decision areas within a global supply chain. This study categorized the factors and the configurational/coordination decision areas with two main competitive priorities, i.e., cost and differentiation in the form of a “conceptual model.” The study also highlighted the factors in a matrix, which showed their position on the spectrum of rooted and footloose network configurations. For instance, the coordination factors that drive towards a footloose network include: high orchestration capabilities, need access to new technology and knowledge, proximity to suppliers, etc. The configurational factors that drive towards a rooted network include: economic stability, proximity to market, concerns for sustainability issues, high transportation cost, need for high proximity between key functions, need for intellectual property rights protection, etc.
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| 2. |
- Ahlenius, Martin
(författare)
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The impact of motivation and person-job fit on employee turnover among Swedish real estate brokers: A mixed method approach
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Residential real estate is a vital part of the economy, and homes are important for individuals for both financial and emotional reasons. Residential homes change owners for numerous reasons, and there is a need for these transactions to be secure and efficient from both the economic and individual perspective. The general idea of residential real estate brokerage is to facilitate these transactions securely and efficiently. Real estate brokerage has therefore captured both media as well as scholarly interest. Some scholars even argue that brokerage is a relevant research and literature field of its own. Like other occupations within sales, the brokerage industry suffers from problems connected to recruiting and retaining employees, as put forth by several spokespersons within the industry and scholars alike. Prior studies argue that there is a need for further studies that describe the occupational life cycle of brokers and employee turnover antecedents, such as intrinsic motivation. Hence, the overarching purpose of this thesis is to describe and analyze occupational turnover and its antecedents among Swedish real estate brokers. This thesis sprung out of a firsthand occupational experience of Swedish brokerage, curiosity, and an abductive stance toward knowledge creation. It is primarily explorative, and the embedded articles consist of different types of methodologic approaches and therefore also different ways of gathering data such as interviews, surveys, and registered data. All data solely involves Swedish real estate brokers. Results of the four articles show that the occupational life cycle of brokers is significantly longer than expected and that Swedish brokers display high levels of work-related intrinsic motivation, occasionally rooted in affective commitment towards customers and gained trust from sellers. Furthermore, being driven by gained trust and customer relations has a positive effect on person-job fit which in turn reduces turnover intentions. A majority of the results within the four articles are not in line with prior studies, which is interesting and prompts speculation. The service landscape of brokerage, and particularly Swedish brokerage due to the broker’s intermediary role and personal responsibility for the entire transaction, arguably drives intrinsic motivation and reduces turnover. This is enhanced by the high educational threshold for becoming a broker in Sweden. This thesis contributes to the literature field of brokerage by providing insights about what motivates brokers and the theoretical field of person-job fit by suggesting ways of improving the operationalization and the validity of person-job fit.
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| 3. |
- Ahmadi, Zahra, 1966-
(författare)
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Market orientation and public housing companies in the Swedish declining market
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The licentiate thesis consists of three papers with the particular topic in public housing. They discuss how the public housing companies manage the transition to higher economic demands meeting increased customer and market requirements. These studies focus specifically on how the public housing company deal with market challenges associated with the decision to demolish, maintain and/or new construction. Market-oriented perspective can be a tool for the public housing companies to achieve better customer value and enhance economic development. Although the market orientation concept has contributed to valuable improvements in research, the thesis assumes that it is necessary to distinguish between that the public housing companies operate market-oriented to meet customer requirements and their focus on innovation.Paper I develops market/innovation types and then investigates how public housing companies adapt to these types. It was found that economic conditions in the municipality have a major impact on the housing companies, causing them to act innovatively and create superior customer value by innovations. The study confirms that the implementation of market and innovation orientation contributes to competitive advantages in growing markets, while weak economic conditions impair implementation in declining markets.Paper II addresses how public housing companies in declining markets act based on the concept of market intelligence. This study suggested and tested whether there is a positive link between collecting customer information, disseminating it in the organization, and responding to customer needs, and whether this link has an impact on strategic performance. The result shows that weak links exist in the process; the efficiency of intelligence distribution in public housing companies is affected mainly by their responsiveness to customer needs.Paper III also addresses the public housing companies’ market strategies in declining markets. This study, based on a market-strategic perspective, compares how public housing companies act in relation to customer wants compared to the private housing market. The result shows that public housing companies are more engaged in carrying out new construction, renovation, and reconstruction, as well as taking more social responsibility compared to the private sector. In particular, their concern for the customers’ social needs is evident.
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| 4. |
- Ahmadi, Zahra, 1966-
(författare)
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The role of market orientation in public housing companies: : A study of MO’s effect on construction strategies
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of public housing companies in Sweden is strongly influenced by legal, economic, and demographic changes. The companies long tradition of taking responsibility for customer welfare in living have recently been criticized for excessive dominance over price setting, which is claimed to give them competitive advantages in the housing market. New legislation in 2011 requires financial return on investment, implying increased competition with radical changes for the companies. Because of the law, they find themselves transitioning from the role of being responsible for living conditions in Sweden to having to work in a businesslike manner with increased competition.The purpose of this dissertation is to analyze how the public housing companies’ deal with market orientation constructs and what their impact is on construction strategy choices. Theoretically, the market orientation concept is seen as a tool for companies to create superior value for the customers and influence strategic performance, which is a relationship tested and analyzed in this dissertation.The research was conducted through data collection stages using qualitative and quantitative methods. In the first stage, a qualitative pilot study was conducted with interviews of 15 managers in 11 public housing companies in central Sweden. In the second stage, two quantitative comparative studies of public and private housing companies in declining markets in central Sweden were conducted, collecting data from 23 (22 survey respondents) public and 37 private housing companies (16 respondents). In the third and final stage, two quantitative studies were conducted, collecting data from all 289 public housing companies (165 respondents) in Sweden.Results of the five studies show, firstly, that economic condition in the municipality have a major impact on the housing companies’ construction strategies, causing them to act innovatively in order to create superior customer value. Secondly, market orientation efforts contribute to competitive advantages in growing markets, while weak economic conditions limit the companies’ construction strategy choices in declining markets. After analyzing the link between market orientation constructs and construction strategy in declining markets, results showed that the public housing companies demonstrate higher responsiveness to customer demands compared to the private sector, but these have no effects on construction strategy. Thirdly, the analysis of moderating (external) and mediating (corporate social responsibility) effects on the market orientation and construction strategy relationship confirms that economic conditions in society influence construction strategy planning and decisions. The results of the mediating effects of CSR indicate that environmental and social issues have a positive influence on the market orientation and construction strategy relationship.
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| 5. |
- Alizadeh, Mahmoud
(författare)
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Characterisation, Modelling and Digital Pre-DistortionTechniques for RF Transmitters in Wireless Systems
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireless systems have become an inevitable part of modern technologies serving humankind. The rapid growth towards large dimensional systems, e.g. 5th generation (5G) technologies, incurs needs for improving the performance of the systems and considering aspects to make them as far as possible environmentally friendly in terms of power efficiency, cost, and so on. One of the key parts of every wireless communication system is the radio frequency (RF) power amplifier (PA), which consumes the largest percentage of the total energy. Hence, accurate models of RF PAs can be used to optimize their design and to compensate for signal distortions. This thesis starts with two methods for frequency-domain characterisation to analyse the dynamic behaviour of PAs in 3rd-order non-linear systems. Firstly, two-tone signals superimposed on large-signals are used to analyse the frequency-domain symmetry properties of inter-modulation (IM) distortions and Volterra kernels in different dynamic regions of RF PAs in a single-input single-output (SISO) system. Secondly, three-tone signals are used to characterise the 3rd-order self- and cross-Volterra kernels of RF PAs in a 3 × 3 multiple-input multiple-output (MIMO) system. The main block structures of the models are determined by analysing the frequency-domain symmetry properties of the Volterra kernels in different three-dimensional (3D) frequency spaces. This approach significantly simplifies the structure of the 3rd-order non-linear MIMO model.The following parts of the thesis investigate techniques for behavioural modelling and linearising RF PAs. A piece-wise modelling technique is proposed to characterise the dynamic behaviour and to mitigate the impairments of non-linear RF PAs at different operating points (regions). A set of thresholds decompose the input signal into several sub-signals that drive the RF PAs at different operating points. At each operating point, the PAs are modelled by one sub-model, and hence, the complete model consists of several sub-models. The proposed technique reduces the model errors compared to conventional piece-wise modelling techniques.A block structure modelling technique is proposed for RF PAs in a MIMO system based on the results of the three-tone characterisation technique. The main structures of the 3rd- and higher-order systems are formulated based on the frequency dependence of each block. Hence, the model can describe more relevant interconnections between the inputs and outputs than conventional polynomial-type models.This thesis studies the behavioural modelling and compensation techniques in both the time and the frequency domains for RF PAs in a 3 × 3MIMO system. The 3D time-domain technique is an extension of conventional 2D generalised memory polynomial (GMP) techniques. To reduce the computational complexity, a frequency-domain technique is proposed that is efficient and feasible for systems with long memory effects. In this technique, the parameters of the model are estimated within narrow sub-bands. Each sub-band requires only a few parameters, and hence the size of the model for each sub-band is reduced.
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| 6. |
- Amin, Shoaib Amin, 1985-
(författare)
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Characterization and Linearization of Multi-channel RF Power Amplifiers
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The demands for high data rates and broadband wireless access require the development of wireless systems that can support wide and multi-band signals. To deploy these signals, new radio frequency (RF) front-ends are required which impose new challenges in terms of power consumption efficiency and sources of distortion e.g., nonlinearity. These challenges are more pronounced in power amplifiers (PAs) that degrade the overall performance of the RF transmitter. Since it is difficult to optimize the linearity and efficiency characteristics of a PA simultaneously, a trade-off is needed. At high input power, a PA exhibits high efficiency at the expense of linearity. On the other hand, at low input power, a PA is linear at the expense of the efficiency. To achieve linearity and efficiency at the same time, digital pre-distortion (DPD) is often used to compensate for the PA nonlinearity at high input power. In case of multi-channel PAs, input and output signals of different channels interact with each other due to cross-talk. Therefore, these PAs exhibit different nonlinear behavior than the single-input single-output (SISO) PAs. The DPD techniques developed for SISO PAs do not result in adequate performance when used for multi-channel PAs. Hence, an accurate behavioral modeling is essential for the development of DPD for multi-channel RF PAs. In this thesis, we propose three novel behavioral models and DPD schemes for nonlinear multiple-input multiple-output (MIMO) transmitters in presence of cross-talk. A study of the source of cross-talk in MIMO transmitters have been investigated to derive simple and powerful modeling schemes. These models are extensions of a SISO generalized memory polynomial model. A comparative study with a previously published MIMO model is also presented. The effect of coherent and partially non-coherent signal generationon DPD performance is also highlighted. It is shown experimentally that with partially non-coherent signal generation, the performance of the DPD degrades compared to coherent signal generation. In context of multi-channel RF transmitters, PA behavioral models and DPD schemes suffer from a large number of model parameters with the increase in nonlinear order and memory depth. This growth leads to high complexity model identification and implementation. We have designed a DPD scheme for MIMO PAs using a sparse estimation technique for reducing model complexity. This technique also increases the numerical stability when linear least square estimation model identification is used. A method to characterize the memory effects in a nonlinear concurrent dual-band PAs is also presented. Compared to the SISO PAs, concurrent dual-band PAs are not only affected by intermodulation distortions but also by cross-modulation distortions. The characterization of memory effects inconcurrent dual-band transmitter is performed by injecting a two-tone test signal in each input channel of the transmitter. Asymmetric energy surfaces are introduced for the intermodulation and cross-modulation products, which can be used to identify the power and frequency regions where the memory effects are dominant.
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| 7. |
- Amin, Shoaib
(författare)
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Characterization and Linearization of Multi-band Multi-channel RF Power Amplifiers
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The World today is deeply transformed by the advancement in wireless technology. The envision of a smart society where interactions between physical and virtual dimensions of life are intertwined and where human interaction is mediated by machines, e.g., smart phones, demands increasingly more data traffic. This continual increase in data traffic requires re-designing of the wireless technologies for increased system capacity and flexibility. In this thesis, aspects related to behavioral modeling, characterization, and linearization of multi-channel/band power amplifiers (PAs) are discussed.When building a model of any system, it is advantageous to take into account the knowledge of the physics of the system and include into the model. This approach could help to improve the model performance. In this context, three novel behavioral models and DPD schemes for nonlinear MIMO transmitters are proposed.To model and compensate distortions in GaN based RF PAs in presence of long-term memory effects, novel models for SISO and concurrent dual-band PAs are proposed. These models are based on a fixed pole expansion technique and have infinite impulse response. They show substantial performance improvement. A behavioral model based on the physical knowledge of the concurrent dual-band PA is derived, and its performance is investigated both for behavioral modeling and compensation of nonlinear distortions.Two-tone characterization is a fingerprint method for the characterization of memory effects in dynamic nonlinear systems. In this context, two novel techniques are proposed. The first technique is a dual two-tone characterization technique to characterize the memory effects of self- and cross-modulation products in concurrent dual-band transmitter. The second technique is for the characterization and analysis of self- and cross-Volterra kernels of nonlinear 3x3 MIMO systems using three-tone signals.
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| 8. |
- Andersson, Daniel, et al.
(författare)
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M-Sequence UWB Radar for Industrial Applications
- 2010
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Ingår i: Program of GigaHertz Symposium 2010, March 9-10, at Lund University.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Ultra Wideband Radar has the potential of dramatically improving the control and surveillance of industrial processes in confined areas. An example is the application of UWB radar for surveillance of furnaces for heath treatment of steel billets developed by Radarbolaget in Gävle. In our installation at AB Sandvik Materials Technology, we have shown that by using a non-destructive UWB Radar technique it is possible to visualize in real-time the ongoing process inside the furnace behind a 0.5 m thick ceramic wall. Since the operating temperature inside the furnace is 1200 °C, there is today no other known method capable of visualizing the process for the operator of the furnace. The system is therefore designed to sustain high temperatures and powerful electromagnetic disturbances while performing measurement with wide dynamics and high stability. The design of this radar is based on the idea of transmitting a continuous m-sequence and then detecting the correlated impulse response (see figure below). The wide bandwidth is a requirement for obtaining high spatial accuracy and resolution but puts further requirements on the design of the antennas and the electronics. Our results show that with this technique it is possible to determine the deformation of the steel billets inside the furnace with an accuracy of less than 5 mm. The radar system is also able to detect deformations in the furnace wall The m-sequence radar has many advantages over other UWB radar technologies since it e.g. does not require many analogue components. Its performance is a result of the choice of code length, sampling rate and averaging. However, the resolution is still limited by the impulse response of the analogue antenna (ringing). In this paper system parameters that affect the overall performance of an m-sequence radar are reviewed and means of enhancing its performance are discussed.
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| 9. |
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| 10. |
- Antón Remírez, Raúl, 1977-
(författare)
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Experimental and numerical study of the thermal and hydraulic effect of EMC screens in radio base stations : detailed and compact models
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today’s telecommunication cabinets use Electro Magnetic Compliance (EMC) screens in order to reduce electromagnetic noise that can cause some miss functions in electronic equipment. Many radio base stations (RBSs) use a 90-degree building architecture: the flow inlet is perpendicular to the EMC screen, which creates a complex flow, with a 90-degree air turn, expansions, compressions, perforated plates and PCBs. It is of great interest to study how the EMC screen interacts with the rest of components and analyze the total pressure drop and how much the flow pattern changes due to the placement of the screen. Velocity, pressure and temperature measurements as well as flow pattern visualizations have been carried out to gain good insight into the flow and heat transfer characteristics in a subrack model of an RBS. Furthermore, these measurements have been very useful for validating detailed CFD models and evaluating several turbulence models. Nowadays, industrial competition has caused a substantial decrease in the time-to-market of products. This fact makes the use of compact models in the first stages of the design process of vital importance. Accurate and fast compact models can to a great extent decrease the time for design, and thus for production. Hence, to determine the correlations between the pressure drop and flow pattern on the PCBs as a function of the geometry and the Reynolds number, based on a detailed CFD parametric study, was one objective. Furthermore, the development of a compact model using a porous media approach (using two directional-loss coefficients) has been accomplished. Two correlations of these directional loss coefficients were found as a function of the geometry and Reynolds number.
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