Fatigue Damage Spectrum calculation in a Mission Synthesis procedure for Sine-on-Random excitations

In many real-life environments, certain mechanical and electronic components may be subjected to Sine-on-Random vibrations, i.e. excitations composed of random vibrations superimposed on deterministic (sinusoidal) contributions, in particular sine tones due to some rotating parts of the system (e.g. helicopters, engine-mounted components,...). These components must be designed to withstand the fatigue damage induced by the "composed" vibration environment, and qualification tests are advisable for the most critical ones. In the case of an accelerated qualification test, a proper test tailoring which starts from the real environment (measured vibration signals) and which preserves not only the accumulated fatigue damage but also the "nature" of the excitation (i.e. sinusoidal components plus random process) is important to obtain reliable results. In this paper, the classic time domain approach is taken as a reference for the comparison of different methods for the Fatigue Damage Spectrum (FDS) calculation in case of Sine-on-Random vibration environments. Then, a methodology to compute a Sine-on-Random specification based on a mission FDS is proposed

A Software Defined Radio Test-bed for WLAN Front Ends

In our Software Defined Radio (SDR) project we aim at combining two different types of standards, Bluetooth and HiperLAN/2 on one common flexible hardware platform. The HiperLAN/2 hardware is that complex compared to the Bluetooth hardware, that Bluetooth capability may be added to the HiperLAN/2 platform at limited cost. The question is how to do this. In this paper we first describe the radio front-end functions and their implementation. Subsequently the test-bed that will assist us in building the hardware platform is described.We present the method by which we use the HiperLAN/2 front-end for Bluetooth reception purposes Our system consists of three parts: analog signal processing, digital channel selection and digital demodulation. The analog processing function is capable of reception of both standards.The demodulation function and channel selection function are implemented in two separate software programs (one for each standard) that allow the exploration of different design alternatives and the assessment of computational cost of the receiver

Incomplete recovery in patients with minor head injury directly discharged home from the emergency department:a prospective cohort follow-up study

OBJECTIVES: To determine the frequency of post-traumatic complaints and recovery rate of non-hospitalised patients with minor head injury (MHI) and their relationship with demographic and injury characteristics. We also evaluated the differences between patient groups in this least severe category of brain and head injury. DESIGN: Prospective cohort follow-up study. SETTING: Patients admitted to the emergency department (ED) of a tertiary hospital in the Netherlands. PARTICIPANTS: 242 patients with MHI (n=100 with head injury only and n=142 with mild traumatic brain injury (mTBI)) discharged home directly after evaluation at the ED. OUTCOME MEASURES: The primary outcome measure was incomplete recovery at 3 months measured by the Glasgow Outcome Scale-Extended score <8. Secondary outcome measures were number of post-traumatic complaints assessed 2 weeks and 3 months postinjury by a standardised questionnaire. Also the number of patients that visited their general practitioner because of persistent complaints was determined. RESULTS: Three months postinjury 48% of patients reported more than one post-traumatic complaint. Half (51%) of patients showed incomplete recovery. Incomplete recovery was associated with headache directly postinjury (OR 3.27, 95% CI 1.28 to 8.34), age (OR 1.02, 95% CI 1.00 to 1.05) and the number of post-traumatic complaints (OR 1.24, 95% CI 1.09 to 1.40) and depression (OR 6.31, 95% CI 1.24 to 32.00) 2 weeks postinjury. Incomplete recovery was comparable between the head injury only and mTBI group (55% vs 50%, 95% CI -12.5 to -23.0). In total 36 MHI patients (28%) visited their general practitioner because of complaints related to their head injury. CONCLUSION: Half of the non-hospitalised patients with MHI experienced incomplete recovery after 3 months without differences between head injury only and mTBI patients. Therefore, early identification of patients at risk for incomplete recovery must be started at the ED to provide appropriate aftercare to avoid long-term post-traumatic complaints

Short-term effects of conservation agriculture on vertisols under tef (Eragrostis tef (Zucc.) Trotter) in the northern Ethiopian highlands

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Toward practical implementation of conservation agriculture : a case study in the May Zeg-zeg catchment (Ethiopia)

Conservation agriculture (CA) is often quoted as a beneficial resource-saving technique for dryland agriculture, but its large-scale implementation is frequently hindered by the lack of farmers' acceptance. To date, few studies have investigated the impact of spatial factors, costs and benefits and regional agroecosystem differentiation on adoption of CA. This study, therefore, aims to assess the impact of these factors through a case study in the North Ethiopian Highlands. One hundred eight farmers of 11 villages surrounding an experimental plot were interviewed in order to identify their knowledge and acceptance of the technique. The results show that several spatial factors play a role in CA acceptance. The lack of knowledge on the resource-saving technique proved primarily dependent (R = -0.73) on spatial impedance with the innovation source and on the strength of sociospatial networks. Next, a consumer model showed that perceived costs and benefits seem to balance each other. Finally, some agronomic traditions were identified that are related to the regional agroecosystem, which are not favoring the implementation of zero-tillage practices. Since this study identified acceptance problems related to several spatial and regional factors, future CA adoption schemes must allow better regional differentiation optimized to local contexts and conditions