Global Public Goods and Global Health

The repair rate on electron beam welded diaphragm hasn’t been at the desired level at Siemens SIT for several years. An improvement program the past five years has reduce the repair rate from 60% to 12-15% but the goal of 5% repair rate hasn’t been met. Collection of diaphragm weld and repair data started in the fall 2011 and in this thesis the material composition of the materials used for the production will be analysed from a statistical perspective. The thesis includes a comprehensive research of the nonparametric statistical methods suitable for non normally distributed, highly kurtotic and skewed data. Unfortunately a lot of statistical tests loose their power to correctly reject a false hypothesis with this kind of data. All of the elements in the material composition and the mechanical properties were analysed individually. In some of the cases it was possible to use statistical methods but in other it was not possible to conclude anything with statistics. Every case of outliers was evaluated individually. The main conclusions are that in all of the four materials there are some elements and mechanical properties outside of the material specifications. A number of cases also had outliers inside of the material specification and in most cases those were causing the variability in the data and had higher repair rates than the overall repair rate. Some trends were found, for example the weld quality was better for lower yield strength in all materials and higher chromium content in material A produced better quality. The first steps to improvement for Siemens are to find out why materials outside of the material specifications are getting all the way to the production without anyone noticing. A simple material process control chart could visually notify if a material is outside of the specification limits or even just outside of the usual. Knowing exactly how the material is before starting the production will give time and space for preventive measures if they are necessary and could improve lead times and decrease costs.För några år har Siemens hatt kvalitetsproblem med Electron Beam svetsing av mellanväggar. Förbättringsprojekt har reducerat reparationer intensivt men fortfarande finns det problemer med svetsningen. Inga mellanväggar lämnar produktionen utan att ha bra kvalitet så att förbättringarna ska fokusera på att reducera produktionskostnader och ledtider. Hösten 2011 började Siemens att samla reparation data för mellanväggarna och i det examens arbetet blir materialsamansättningen analyserad med statistiska metoder. Arbetet innehåller övergripande analysis på non-parametriska statistiska metoder och hur dom funkerar på skevat data med hög kurtosis. Tyvärr finns det inte många metoder som har hög chans att förkasta falska hypoteser när man jobbar med sånt data. Alla elementer och mekaniska egenskaper av materialet blev analyserade, men tyvärr inte alltid med statistiska metoder. Alla extremvärden blev analyserade individuellt. I alla fyra materialer finns det elementer och mekaniska egenskaper utan förmaterialets specifikationer. I vissa fall finns det outliers inom materialets specifikationer men som har högre reparation procent än det vanliga och orsakar variationen i datat. Vissa tendenser kunne hittas, till exempel att det går bättre att svetsa materialer med lägre sträckgräns och högre kromhalt går bättre för material A. Simpelt processstyrningdiagram skulle kunna visa om material är utanför material specifikationen men också om materialet är utanför det ”vanliga”. Att veta exact hur materialet är innan produktion kan sjunka ledtider och produktionskostnader

A scaling-limit approach to the theory of laser transition

The conditions for the appearance of a sharp laser transition are formulated in terms of a scaling limit, involving vanishing cavity loss and light-matter coupling, $\kappa \to 0$, $g \to 0$, such that $g^2/\kappa$ stays finite. It is shown analytically that in this asymptotic parameter domain, and for pump rates above the threshold value, the photon output becomes large in a sense that is specified, and the photon statistics becomes strictly Poissonian. Numerical examples for the case of a two-level and a three-level emitter are presented and discussed in relation to the analytic result.Comment: Intended as contribution to "Photonics Europe 2012" Brussels, Belgiu

TPA (CHCH) rental survey 2013: a study of increasing rents and housing conditions in the Greater Christchurch Area

OverviewThe earthquakes that hit the Canterbury region in 2010/11 destroyed a significant amount of rental housing and damaged many homes. This has resulted in reduced supply, increased demand and increases in rental costs. The average weekly rent in the Greater Christchurch area has increased 31% since August 2010i. Tenants are significantly affected by issues of affordability, accessibility and suitability of rental housing.The TPA rental survey is a response to the concerns expressed by many tenants across Canterbury with these rent increases and with the quality of their housing.This report considers the results of the survey which asked tenants questions about rent increases, quality of rental housing and the effects of rising rents on tenants’ well-being post-earthquakes

A review of alternative approaches to the reduction of CO2 emissions associated with the manufacture of the binder phase in concrete

In this review we discuss a wide range of alternative approaches to the reduction of CO2 emissions associated with the manufacture of the binder phase in concrete. They are classified broadly as follows: (1) Use alternative fuels and/or alternative raw materials in the manufacture of Portland-based cements. (2) Replace Portland clinker with “low-carbon” supplementary cementitious materials (SCMs) in concrete. (3) Develop alternative low-carbon binders not based on Portland clinkers. The first approach mainly represents incremental improvements that can be achieved fairly easily and cheaply as long as suitable raw materials can be found. The second approach ranges from incremental improvements, if low levels of SCM substitution are used, all the way to major innovations for binders with very high Portland clinker replacement levels. The third approach is the most risky but also holds the greatest promise for truly significant CO2 reductions if it can be implemented on a large scale

Nonlinear plastic modes in disordered solids

We propose a framework within which a robust mechanical definition of precursors to plastic instabilities, often termed `soft-spots', naturally emerges. They are shown to be collective displacements (modes) $\hat{z}_0$ that correspond to local minima of the `barrier function' $b(\hat{z})$. The latter is derived from the cubic approximation of the variation $\delta U_{\hat{z}}(s)$ of the potential energy upon displacing particles a distance $s$ along $\hat{z}$. We show that modes $\hat{z}_0$ corresponding to low-lying minima of $b(\hat{z})$ lead to transitions over energy barriers in the glass, and are therefore associated with highly asymmetric variations $\delta U_{\hat{z}}(s)$ with $s$. We further demonstrate how a heuristic search for local minima of $b(\hat{z})$ can a-priori detect the locus and geometry of imminent plastic instabilities with remarkable accuracy, at strains as large as $\gamma_c-\gamma \sim 10^{-2}$ away from the instability strain $\gamma_c$, where the non-affine displacements under shear are still largely delocalized. Our findings suggest that the a-priori detection of plastic instabilities can be effectively carried out by the investigation of the landscape of $b(\hat{z})$.Comment: 8 pages, 8 figure

How collective contracts and works councils reduce the gender wage gap

"The gender wage gap in Germany is smaller in firms covered by collective contracts or having a works council, partly because these institutions are associated with lower unobserved productivity differences and less wage discrimination, partly because they compress the distribution of wage residuals." (Author's abstract, IAB-Doku) ((en))Lohnunterschied, Männer, Frauen, geschlechtsspezifische Faktoren, Tarifvertrag - Auswirkungen, Betriebsrat - Auswirkungen, Lohndifferenzierung, Lohndiskriminierung, IAB-Linked-Employer-Employee-Datensatz

Analyzing the changing gender wage gap based on multiply imputed right censored wages

"In order to analyze the gender wage gap with the German IAB-employment sample we have to solve the problem of censored wages at the upper limit of the social security system. We treat this problem as a missing data problem. We regard the missingness mechanism as not missing at random (NMAR, according to Little and Rubin, 1987, 2002) as well as missing by design. The censored wages are multiply imputed by draws of a random variable from a truncated distribution. The multiple imputation is based on Markov chain Monte Carlo (MCMC) technique. We complete the dataset with this technique in order to apply a Juhn-Murphy-Pierce-decomposition. As the main sources for the narrowing gender wage gap from 1991 to 2001 we identify an improvement of women's position within the wage distribution." (Author's abstract, IAB-Doku) ((en))Lohnunterschied, Lohnhöhe, geschlechtsspezifische Faktoren, IAB-Beschäftigtenstichprobe, Datenaufbereitung, Datenanalyse, angewandte Statistik, Imputationsverfahren