Being one of the most spectacular events in nature, lightning is basically a transient high current electric discharge in the atmosphere, which extends up to kilometres. Cloud to ground discharge is the most hazardous one as far as ground based structures are considered. Among the different phases of a lightning flash, return stroke is considered to be the most energetic phase and is basically responsible for most of the damages. Hence, much emphasis has been given to return stroke modeling. A more realistic modeling of return stroke is very essential to accurately study the interaction of return stroke with the structures on ground. As return stroke is dominated by electromagnetic phenomenon, an electromagnetic model will be the most suitable one. It does not call for any assumption on the mode of wave propagation, as well as, electromagnetic coupling between the different channel portions. There are mainly two approaches adopted for electromagnetic models i.e. frequency domain and time domain approach. Time domain approach is more reliable as it can handle, in principle, the nonlinear processes in the lightning channel. It is also free of numerical frequency domain to time domain inversion problem, which are found to be quite severe. However, most of the previous works on time domain electromagnetic models suffered from following two serious limitations - (i) the initial charge on the channel, which forms the true excitation for the problem, is not considered and (ii) instead of the non-linearly rising conductivity of the channel, a constant resistance is employed. For a realistic simulation of the interaction between the channel and any intercepting system, a time domain model with the above two major aspects being fully represented is very essential. In an earlier work, all these aspects have been fully considered but a domain based numerical modelling was employed. Consequently, it was difficult to consider the down conductor and further the number of unknowns was considerably large. In view of this, the present work is taken up and its scope is defined as to develop a boundary based numerical time domain electromagnetic model in which the initial charge on the channel and the non-linearly evolving channel conductance are fully considered. For the electrical engineering applications, electromagnetic aspects of the lightning phenomena is more important than the other associated physical processes and hence, importance is given only to the electromagnetic aspects. In other words, the light emission, thunder, chemical reactions at the channel etc. are not considered. Also, for most of the electrical engineering applications, the critical portion of current would be the region up to and around the peak and hence, modeling for this regime will be given prime importance. Owing to the complexity of the problem, some simplifying assumptions would be very essential. The literature indicates that these assumptions do not affect the adequate representation of the phenomena. Lightning channel is considered to be vertically straight without any branches. Earth is considered to be perfectly conducting. Explicit reference to dynamically varying channel radius, temperature and the air density is not made. However, it is assumed that the arc equation employed to describe the temporal changes in conductivity would adequately take care of these parameters. Lightning channel is represented by a highly conducting small core, which is surrounded by a weakly conducting corona sheath. The initial charge on the channel is deduced by solving for electrostatic field, with leader portion set to possess an axial gradient of 60 V/cm and the streamer portion to 5 – 10 kV/cm. The radius of the corona sheath is set iteratively by enforcing a gradient of 24 kV/cm up to its radial boundary. As analytical solution for the problem is impractical, suitable numerical solution is sought. Since the spatial extension of this time marching problem is virtually unbound and that the significant conduction is rather solely confined to an extremely small cross section of the channel core, a boundary-based method is selected. Amongst the numerical methods, the present work employs the moment method for the solution of the fields associated with the return strokes. A numerical solution of the Electric Field Integral Equation (EFIE) for thin structures has been developed in the literature. The same approach has been employed in the present work, however, with suitable modifications to suit the lightning problem. The code was written in MATLAB and integrations involved in the EFIE were solved using MATLAB symbolic computation. Before introducing the channel dynamic conductance and the initial charge on the channel, the code developed is validated by comparing the results for a center fed dipole antenna with that given in the literature. Also, NEC (Numeric Electromagnetic Code) simulations for various cases of monopole and dipole antenna were performed. The results from the code developed are shown to have good matching with that obtained from NEC based time domain results. In an earlier work, the dynamic conductance of the return stroke channel core, which is a high current electric arc, was represented by a first order arc equation. The same approach is employed in the present work also. Similarly, the transition from streamer to leader was modeled by Braginskii’s spark law and the same has been considered in the present work. A value of 10-5 S/m was used for minimum value of streamer conductance. For numerical stability, upper (Gmax = 3 S/m) and lower bounds (Gmin = 0.0083 S/m) for the channel conductance are forced. Preliminary simulations were run with and without dynamic channel conductance. The initial charge distribution along the channel formed the excitation. Results clearly show that without the dynamically varying channel conductance, no streamer to leader transition and hence, no return stroke evolution can occur. In other words, the non-linearly evolving channel conductance is mainly responsible for the evolution of the return stroke. In order to consider the charge neutralization by the return stroke, the charge deposited by it is diffused into the corona sheath. A fixed value of the corona sheath conductance is employed and the diffusion process is modeled by an equation derived from the continuity equation. To study the effect of corona sheath, simulations were run with and without corona. From the simulation results it was observed that the corona sheath causes increase in peak value of the stroke current, as well as, time to front and a decrease in the velocity of propagation. For the validation of the model, the basic characteristics of the return stroke current like the current wave shape, temporal variation of stroke current at different heights, velocity of propagation and the vertical electric fields at various radial distances were compared with available field/experimental data. A good agreement was seen and based on this, it is concluded that the present work has successfully developed a boundary based time domain numerical model for the lightning return stroke. Natural lightning being a stochastic process, the values of the parameters associated with it would differ in every event. On other hand, any deterministic model like the one developed in the present work predicts a fixed pattern of the simulated quantities. Therefore, it was felt that some of the model parameters must be permitted to vary so that a range of results could be obtained rather than a single pattern of results. Incidentally, the model parameters like arc time constant, settling value of arc conductivity/gradient, bounds for channel conductivity, streamer gradient, radius of the core etc. are not precisely known for the natural lightning environment. Further, some of them are known to vary within an event. Considering these and that simplicity is very important in already complex model, the above-mentioned parameters are taken as tunable parameters (of course to be varied within the prescribed range) for deducing the return stroke currents with some desired characteristics. A study on the influence of these parameters is made and suggestions are provided. Simulations for the nominal range of stroke currents are made and results are presented. These simulations clearly show the role of cloud potential, which in turn dictates the length of final bridging streamer, on the return stroke currents. The spatio-temporal variation of the current, charge deposited by the return stroke and the channel conductivity are presented which, reveal the dynamic processes leading to the evolution of return stroke current. Subsequently, simulations for two cases of stroke to elevated strike object are attempted. The upward leader was modeled quite similar to the descending one. Many interesting findings are made. In summary, the present work has successfully developed a boundary-based time domain numerical electromagnetic model for the lightning return stroke, wherein, the initial charge deposited on the channel and the non-linearly rising channel conductance have been appropriately considered. Simulation using the model clearly depicts the dynamic evolution of the return stroke. The characteristics of the simulated return strokes are in good agreement with the field data. Some of the parameters of the model are suggested as tunable parameters, which permit simulation of strokes with different characteristics.

In the design of most of the modern systems, lightning threat needs to be considered at the design phase itself. This demands a suitable model and owing to associated complexity, only simplified modeling have been attempted. As a consequence, it does not provide adequate insight into the phenomena. Considering these, a more realistic time-¬ domain electromagnetic model for the return stroke current evolution has been developed by incorporating the following underlying physical processes: (i) excitation formed by the electric field due to charge distribution along the channel, cloud and that induced on ground, (ii) the transient enhancement of series conductance at the bridging regime, which initiates the return stroke,( iii) the non¬linear variation of channel conductance along with (iv) the associated dynamic Electromagnetic Fields(EMFs) that supports the current evolution. The intended modeling begins from the instant of bridging and the pre-¬return stroke charge distribution along the channel is calculated using Charge Simulation Method(CSM). For the calculation of dynamic EMFs, the thin wire Time Domain Electric Field Integral Equation(TD¬EFIE) is employed The transient enhancement of conductance at the bridging/streamer region is emulated using Toepler’s spark law while that along the matured section of the channel is described by first order arc model. The macroscopic physical model developed depicts most of the salient features of current evolution and resulting remote electromagnetic fields in a self¬ consistent manner. The work is not limited by the simplifications adopted for the channel geometry. The strength of the model was exploited for investigating a couple of practically important questions, one of which had divided opinion in the literature. Firstly, analysis showed that the "secondary" current waves generated by successive reflection within struck TGO and that fed by branches do not get reflected at the main wave front. It is shown that the dynamic spatial resistance profile of the channel at the main wave front is primarily responsible for this behavior. Secondly, it is shown that the abrupt change in radii at TGO ¬channel junction is mainly responsible for reflection at the junction. In summary, a novel time-¬domain macroscopic physical model for the first return stroke of a downward cloud¬-to-¬ ground lightning has been successfully developed, which is capable of providing much deeper insight in to the complex phenomena.

Studiens syfte är att undersöka vilken värdeförändring som sker för det avknoppade bolaget på kort och lång sikt under tidsperioden 1996–2018 på den svenska marknaden. Avknoppning inträffar när ett moderbolag delar ut innehavet av aktier i ett dotterbolag till aktieägarna. Avknoppning kan antingen vara fokuserad eller icke fokuserad. Fokuserad avknoppning innebär att moderbolaget knoppar av till ett nytt bolag inom samma bransch och icke fokuserad avknoppning innebär avknoppningen sker till annan bransch än moderbolaget. Anledning till att genomföra en avknoppning är att öka aktievärdet för bolagets aktieägare. Bolagen i studien har genomfört minst en fokuserad eller icke fokuserad avknoppning efter införandet av Lex Asea på den svenska marknaden. Lex Asea är ett regelverk som möjliggör utdelning av aktier från moderbolaget till aktieägarna utan att påverka beskattningen för aktieägarna. Enligt tidigare studier är avknoppning förenat med överavkastning. Problematiken uppstår i att tidigare studier har studerat olika förklarande variabler till övereller underavkastning på andra börsmarknader. Resultat av detta vill vi i vår studie studera om förklarande variablerna relativ storlek och Return On Asset påverkar över- eller underavkastningen för bolag noterade på Stockholmsbörsen. Över- eller underavkastning på kort sikt studeras med Cumulative Abnormal Return (CAR) på 1, 2, 3, 4 och 5 dagars sikt. Över- eller underavkastning på lång sikt studeras med Buy-andhold Abnormal Return (BHAR) på 6, 12, 18 och 24 månaders sikt. Studiens data gällande aktiekurser och dess prisutveckling hämtas från Thomson Reuters Eikon. Information om vilka avknoppningar som genomförts på den svenska marknaden under tidsperioden 1996– 2018 hämtades från Skatteverket. I studien genomförsregressionsanalys i form av multivariat analys med tillhörande förklarande variabler. Analysen genomförs för att försöka hitta samband om dessa variabler kan förklara över- eller underavkastning för studerande bolag i studien. Studiens resultat påvisade underavkastning under det observerade eventfönstret på kort sikt och överavkastning på lång sikt. Den genomsnittliga underavkastningen uppgick under en femdagarsperiod till -2,4% och den genomsnittliga överavkastningen uppgick under en period på 24 månader till 48,5%. / The purpose of the paper was to investigate the abnormal return in the short and the long run for spinoffs during the time period 1996-2018. The result of the study showed a negative abnormal return during the observed event window in the short run and a positive abnormal in the long run. The average abnormal return during a five-day period was -2,4% and the average abnormal return during a 24-month period was 48,5%. The study investigated whether ROA and the relative size of the company could explain the abnormal return.

Returbeteendet för kläder köpta online ökar i takt med digitaliseringen. Milda returpolicys gör det lättare för konsumenter att utföra returer, inte minst avsiktliga returer. Genom fria returer kan konsumenten enkelt beställa hem stora mängder i varierande storlekar med avsikten att returnera hela eller delar av beställningen. Syftet med studien har varit att undersöka huruvida konsumenters returbeteende hör samman med deras attityd samt företags returpolicy. Syftet besvarades med hjälp av en kvantitativ studie. Vidare utgår studien från teorin för Theory of planned behaviour, Categories of online returning behaviour samt tidigare forskning inom returpolicys. Tidigare forskning har påvisat tydligt gap mellan returattityd och beteende. Vad konsumenter tycker och vad de gör stämmer således inte överens. Däremot kommer studiens resultat fram till att gapet inte alltid är markant. Konsumenters attityd är inte konstant då de kan skilja i styrka beroende på område och situation. Detta betyder att gapet mellan attityd och beteende kan variera. Vår studie konstaterar att attityd kopplat till hållbarhet inte visar samband med returbeteende. Däremot stämmer returattityden gentemot överdriven returnering överens med returbeteendet. Vidare konstaterar studien att konsumenter som värderar returpolicy är mer benägna att genomföra avsiktliga returer. / The return behaviour for clothes bought online increases in conjunction with digitalisation. Mild return policies make it easier for consumers to make returns, not least intentional ones. Through free returns, the consumer can easily order large quantities in varying sizes with the intention of returning the whole or part of the order. The purpose of the study has been to investigate whether consumers' return behaviour is related to their internal attitude and external circumstances such as return policy. The purpose was answered through a quantitative study. Furthermore, the study is based on the Theory of planned behaviour, Categories of online returning behaviour, and categorization of return policies. Previous research has shown a significant gap between return attitude and behaviour. This means what consumers think and what they do don’t interrelate. However, our study concludes that the gap is not always significant. Consumers' attitudes are not constant as they can differ in strength depending on area and situation. This implies that the gap between attitude and behaviour can vary. Our study states that attitudes regarding sustainability do not correlate with return behaviour. On the other hand, the return attitude towards excessive returns is in line with the return behaviour. Furthermore, the study finds that consumers who value return policies are more likely to make intentional returns. The thesis of the study is written in Swedish.

Thesis (MBA)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Portfolio managers and investors have developed numerous stock-picking strategies for managing stock market portfolios, many of which have been researched extensively in international markets. For example, research has shown that value stocks have higher returns than growth stocks in markets around the world (Fama & French 1998). A very popular value investing strategy is the ‘magic formula’ developed and published by Joel Greenblatt, in 2006, in his book The little book that beats the market. This strategy is based on constructing portfolios where return on capital and earnings yield are used as selection criteria. Greenblatt (2010) provided results that showed that the magic formula strategy was able to persistently outperform the United States stock market from 1988 to 2009. This study provides a back-test of the magic formula on stocks listed on the Johannesburg Stock Exchange for the period 1 January 1998 to 31 December 2013. The return was benchmarked against the FTSE/JSE J203 All Share Total Return Index and several other popular value investing strategies over the same period. It was found that, even after adjusting for risk, the magic formula was able to consistently outperform the market index. While the magic formula was able to outperform the market index, it was not the top performing value investing strategy evaluated in this study. The magic formula was outperformed by the combination of size and book-to-market, book-to-market alone, dividend yield, and earnings yield value investing strategies. While the magic formula, and the above mentioned value investing strategies, were able to outperform the market index in terms of overall geometric mean returns, there is not enough evidence to conclude that these value investing strategies outperformed the market index by a statistically significant margin.

Thesis (MBA)--Stellenbosch University, 2015. / ENGLISH ABSTRACT:The main aim of this study was to determine the effect of unanticipated information, or noise, on the returns of cap-weighted portfolios in various segments of the JSE for the period 1995 to 2014. Capital Market Theory states that the optimal ex ante portfolio comprises all shares in a market/segment weighted by ex ante market capitalisation. The optimal ex ante portfolio is however rarely the optimal ex post portfolio, because it is underweighted in shares that will unexpectedly become ‘winners’ during the investment period and overweighted in those that will become ‘losers’. According to Fuller, Han and Tung (2012), all investors in a segment would gain maximum alpha from a portfolio weighted by ex post market capitalisation – in other words, a ‘perfect foresight’ (PF) portfolio. The excess return of the PF portfolio over the benchmark portfolio therefore is an estimate of the negative effect of noise on the return of the benchmark portfolio. In this study, the returns of PF portfolios were compared with the All Share, Large Cap, Mid Cap, Small Cap, Financials, Industrials and Resources segments of the JSE. Intuitively, information to guide decisions on portfolio weighting would be more valuable and deliver more profit when the cross-sectional standard deviation of share returns is high. A secondary aim was therefore to investigate the correlation between cross-sectional standard deviation and PF excess return. It was found that a strong positive correlation (more than 88%) existed between cross-sectional standard deviation and PF excess return in all segments. In ascending order of cross-sectional standard deviation and PF excess return, the results for the segments were Financials (25% and 5%), Resources (28% and 6%), Large Cap (29% and 8%), Industrials (30% and 9%), All Share (32% and 9%), Mid Cap (36% and 13%) and Small Cap (43% and 17%).

No description available.

We utilize the model of Llorente, Michaely, Saar and Wang (2002) to exam the dynamic volume-return relation of individual stocks in Taiwan stock market. In the LMSW (2002) model, investors trade to share risk and speculate on private information, and the show that hedging trades generate negatively autocorrelation returns, whereas speculative trades generate positively autocorrelation returns. We use daily volume and return data of stocks listed on TSEC to test the prediction of the model. Our results, which are consistent with LMSW (2002), show the cross-sectional variation in the relation between volume and return autocorrelation is related to the degree of information asymmetry. When we use some difference proxies of information asymmetry to test, the dynamic volume-return relation in Taiwan still consists with the theoretical prediction of LMSW (2002).

台灣自民國五十一年至九十七年期間歷經了七次的承銷制度改革，配售方式由原先的公開抽籤，歷經競價拍賣與公開抽籤並行，一直到民國九十三年，市場旋以詢價圈購為主流。本文除整理台灣承銷市場於此段時期的制度沿革外，並探究民國八十年至九十七年間，三種制度的施行是否直接地造成期初異常報酬的差異。 透過實證研究發現，初次上市上櫃公司選擇不同的承銷配售方式確實對期初報酬的影響程度確有著顯著的不同，而三種方式的期初報酬以詢價圈購為最高，公開申購次之，競價拍賣為價格發現能力最好的承銷配售方式，其結果與國外文獻相同。但對於制度改革而言，與期初報酬並沒有直接關連性。如民國八十四年就已開放詢價圈購方式，但由於其相關承銷規定背離市場習慣，導致此方式乏人問津，直至民國九十三年做更進一步的放寬限制，方才改變市場的承銷配售方式，由此可知法令變革的宣告並無法直接影響期初價格，而是待法令改革之後，實際落實於市場方會改變市場期初報酬的現象。 / There are seven main reforms of initial public offering methods in Taiwan during 1962 to 2008. From the fixed price method transform to auction, and in 2004 the bookbuilding became the mainstream in the IPO market. In this thesis we not only compile the reform processes in IPO methods in Taiwan capital market but also study the relationship between the initial returns and the IPO methods during 1991 to 2008. Through the empirical studies, there are significant differences between the initial returns and three IPO methods. The auction owns the highest initial return and bookbuilding own the best price discovering mechanism. However the reform announcements could not affect the initial returns directly. The bookbuilding method is allowed in 1995 but due to deviating from custom, no firms applied it in the IPO until the further reform in 2004. The simple reform announcement could not affect the initial returns directly.

In this thesis, I examine the ideas of home among Irish-born return migrants who left the Republic of Ireland in the late-1980s/early-1990s for the United States, and then came back at the beginning of the 2000s. Drawing on an analysis of intensive interviews, I elucidate the ways in which my research participants articulate and use the concept of home to negotiate their (re)settlement experiences. The overarching argument of the thesis is that participants’ interpretations represent an alternative to fixed, bounded and exclusionary understandings of home, without necessarily downplaying the longing for a discreet, foundational and originary home. This is important because their accounts of home begin to challenge narrow readings of locality and stable definitions of identity. Moreover, their narratives of home force researchers to address awkward questions about who belongs to particular places, and on what basis claims to membership are made. I develop this argument throughout the thesis by analyzing participants’ descriptions of (re)settlement in the old/new places they inhabit. I show that the majority of participants conventionally justify the return decision as the restoration of a settled sense of home. The actual experience of (re)settlement, however, requires many participants to redefine home upon return. The anxieties associated with the return experience means that home can be simultaneously a space of both homecoming and leavetaking, blurring distinctions between ‘here’ and ‘there’, home and away. In effect, what participants’ narratives draw attention to is the often-overlooked tension between home’s dual meaning: its lived and longed-for aspects. While the reality of return revises the expectations surrounding homecoming, opening out home to broader sets of connections does not necessarily mitigate the longing to belong ‘at home’, to anchor the elusive aspects of home. Participants’ accounts of (re)settlement point towards an accommodation of both grounded and uprooted homes simultaneously: translocally lived, yet longed-for as discreetly-defined. These findings are significant, as they foreground the moored and mobile moments of home as complementary and co-existing rather than conflicting and contending. Return migrants’ (re)settlement experiences offer a productive entry point into investigating this paradoxical nature of home in contemporary societies.