Linearized inverse scattering based on seismic Reverse Time Migration

In this paper we study the linearized inverse problem associated with imaging of reflection seismic data. We introduce an inverse scattering transform derived from reverse-time migration (RTM). In the process, the explicit evaluation of the so-called normal operator is avoided, while other differential and pseudodifferential operator factors are introduced. We prove that, under certain conditions, the transform yields a partial inverse, and support this with numerical simulations. In addition, we explain the recently discussed 'low-frequency artifacts' in RTM, which are naturally removed by the new method

Government of Malawi's unconditional cash transfer improves youth mental

We explore the impacts of Malawi's national unconditional cash transfer program targeting ultra-poor households on youth mental health. Experimental findings show that the program significantly improved mental health outcomes. Among girls in particular, the program reduces indications of depression by about 15 percentage points. We investigate the contribution of different possible pathways to the overall program impact, including education, health, consumption, caregiver's stress levels and life satisfaction, perceived social support, and participation in hard and unpleasant work. The pathways explain from 46 to 65 percent of the program impact, advancing our understanding of how economic interventions can affect mental health of youth in resource-poor settings. The findings underline that unconditional cash grants, which are used on an increasingly large scale as part of national social protection systems in Sub-Saharan Africa, have the potential to improve youth mental wellbeing and thus may help break the vicious cycle of poverty and poor mental health

Government of Malawi's unconditional cash transfer improves youth mental

We explore the impacts of Malawi's national unconditional cash transfer program targeting ultra-poor households on youth mental health. Experimental findings show that the program significantly improved mental health outcomes. Among girls in particular, the program reduces indications of depression by about 15 percentage points. We investigate the contribution of different possible pathways to the overall program impact, including education, health, consumption, caregiver's stress levels and life satisfaction, perceived social support, and participation in hard and unpleasant work. The pathways explain from 46 to 65 percent of the program impact, advancing our understanding of how economic interventions can affect mental health of youth in resource-poor settings. The findings underline that unconditional cash grants, which are used on an increasingly large scale as part of national social protection systems in Sub-Saharan Africa, have the potential to improve youth mental wellbeing and thus may help break the vicious cycle of poverty and poor mental health

Cash Transfers, Early Marriage, and Fertility in Malawi and Zambia

There is increasing interest in the ability of cash transfers to facilitate safe transitions to adulthood in low-income settings; however, evidence from scaled-up government programming demonstrating this potential is scarce. Using two experimental evaluations of unconditional cash transfers targeted to ultra-poor and labor-constrained households over approximately three years in Malawi and Zambia, we examine whether cash transfers delayed early marriage and pregnancy among youth aged 14 to 21 years at baseline. Although we find strong impacts on poverty and schooling, two main pathways hypothesized in the literature, we find limited impacts on safe transition outcomes for both males and females. In addition, despite hypotheses that social norms may constrain potential impacts of cash transfer programs, we show suggestive evidence that pre-program variation in social norms across communities does not significantly affect program impact. We conclude with policy implications and suggestions for future research

Characteristics of Injuries in the Logging Industry of Louisiana, USA: 1986 to 1998

Characterizing injuries and their trends will allow safety managers to concentrate their resources on the areas of safety that will be most effective in the workplace. Injuries reported to the Louisiana Office of Workers' Compensation Administration for 1986 to 1998 were characterized according to the part of the body affected, the nature of the injury, the source of the injury, and the type of accident for the timber harvesting industry. Many of the injuries in the logging sector were sprains / strains to the knees. Injuries resulting from falling onto structures and surfaces were common and rising. Although the number of accidents in each category is generally decreasing, some trends should be of concern. There was no significant linear trend in overall accident rates since 1991. While the proportion of cuts and lacerations declined, the proportion of fractures increased. This coincided with a time period when logging operations in Louisiana experienced rapid mechanization and insurance companies started enforcing the use of personal protective equipment. The proportion of transportation accidents rose more than any other category. Some suggestions on focusing and improving current safety programs are given. The need for continued and improved training of managers and employees seems to be most critical

Transient Analysis of a Line-Focus Transducer Probing a Liquid/Solid Interface

The use of a line-focus ultrasonic transducer in a vertical scanning reflection acoustic microscope system is well known for quantitative materials characterization [1]. The technique relies on the measurement of the reflected radio frequency tone burst echo amplitude, V, as a fonction of amount of defocus, z, and analysis of the interference minima of the V(z) curve to obtain various interface wave speeds. The technique uses well developed theory [2,3,4] representing fixed frequency ultrasound generated and detected by a cylindrical lens in the frequency domain. We have developed a large aperture lensless line-focus transducer which is highly efficient and has a bandwidth wide enough to allow the generation and detection of narrow transient pulses [5]. From this transducer placed in water near a solid sample, the resulting echo waveforms have multiple features which can be interpreted as the arrival of a specularly reflected axial ray and leaky surface waves. Using this transducer, we have developed a time-resolved and polarization-sensitive testing technique for materials characterization [6]. The objective of this paper is to provide a theoretical basis for interpretation and analysis of these time domain waveforms

De tactische boer : het management en de informatiebehoefte van melkveehouders

Verslag van vraaggesprekken met 21 melkveehouders uit het noorden van het land over het management van hun bedrijf (planning, uitvoering en evaluatie) en over het gebruik van en wensen t.a.v. informatie en informatiesystemen. De betrokken veehouders waren gewend met veel informatie om te gaan, o.a. uit het LEI-volgboekhoudingssysteem VEEPR

Parameter identification in a semilinear hyperbolic system

We consider the identification of a nonlinear friction law in a one-dimensional damped wave equation from additional boundary measurements. Well-posedness of the governing semilinear hyperbolic system is established via semigroup theory and contraction arguments. We then investigte the inverse problem of recovering the unknown nonlinear damping law from additional boundary measurements of the pressure drop along the pipe. This coefficient inverse problem is shown to be ill-posed and a variational regularization method is considered for its stable solution. We prove existence of minimizers for the Tikhonov functional and discuss the convergence of the regularized solutions under an approximate source condition. The meaning of this condition and some arguments for its validity are discussed in detail and numerical results are presented for illustration of the theoretical findings