The efficiency of thermoelectric energy converters is limited by the material thermoelectric figure of merit (zT). The recent advances in zT based on nanostructures limiting the phonon heat ...conduction is nearing a fundamental limit: The thermal conductivity cannot be reduced below the amorphous limit. We explored enhancing the Seebeck coefficient through a distortion of the electronic density of states and report a successful implementation through the use of the thallium impurity levels in lead telluride (PbTe). Such band structure engineering results in a doubling of zT in p-type PbTe to above 1.5 at 773 kelvin. Use of this new physical principle in conjunction with nanostructuring to lower the thermal conductivity could further enhance zT and enable more widespread use of thermoelectric systems.
The effect of the resonant impurity Tl, known to produce a high thermoelectric figure of merit in PbTe through a distortion of the density of states (DOS), is explored here in p-type PbTe1-xSx and ...PbTe1-ySey alloys with direct substitution of Tl for Pb, with the goal of combining its effect with a reduction of the thermal conductivity by alloy scattering. In PbTe1-xSx, the high DOS of PbTe:Tl (x = 0) is maintained up to x = 0.08, whereas the samples' mobility surprisingly increases monotonically with x. An optimal composition is found to reach zT = 1.6 at x = 0.08, using double-doping with both Tl and Na. The DOS of all PbTe1-ySey alloys decreases with y 0. KKR-CPA electronic structure calculations were performed to enlighten the experimental trends in transport properties: thallium triggers the formation of free-electron-like excess DOS near Fermi level by coupling a Tl 6s-level to the Te p-levels. We ascribe the loss of resonant behavior to a change in overlap between these two levels due to the decrease of the lattice constant with x and y.
A high-temperature thermoelectric generator (TEG) was recently integrated into two passenger vehicles: a BMW X6 and a Lincoln MKT. This effort was the culmination of a recently completed Department ...of Energy (DOE)-sponsored thermoelectric (TE) waste heat recovery program for vehicles (award #DE-FC26-04NT42279). During this 7-year program, several generations of thermoelectric generators were modeled, designed, built, and tested at the couple, engine, and full-device level, as well as being modeled and integrated at the vehicle level. In this paper, we summarize the history of the development efforts and results achieved during the project, which is a motivation for ongoing research in this field. Results are presented and discussed for bench, engine dynamometer, and on-vehicle tests conducted on the current-generation TEG. On the test bench, over 700 W of power was produced. Over 600 W was produced in on-vehicle tests. Both steady-state and transient models were validated against the measured performance of these TEGs. The success of this work has led to a follow-on DOE-sponsored TE waste heat recovery program for passenger vehicles focused on addressing key technical and business-related topics that are meant to enable TEGs to be considered as a viable automotive product in the future.
Due to the loss of agro-biodiversity, there is a strong effort to find apparent and efficient mechanisms for the conservation and sustainable use of genetic diversity. A joint monitoring of the ...diversity and collections structure of the Montenegrin maize landraces conserved in the Serbian (MRIZPGB) and Montenegrin (MGB) gene banks has been conducted in order to improve the composition of the collections and to identify and eliminate possible redundancy. Based on a separate analysis of white- and yellow-orange maize landraces, it can be concluded that the diversity and evolution of distinct maize landraces grown and collected in Montenegro have been simultaneously shaped by both environmental (i.e., natural selection) and socially driven factors (farmers’ selection, migration and colonization processes of the human population). Although it has been determined that the authenticity and variability of the Montenegrin maize landraces gene pool have largely been preserved in the MRIZPGB collection, a significant amount of redundancy was observed. The obtained results will contribute to the cost-efficient conservation of the maize gene pool in the Montenegrin and Serbian gene banks. The recognized and well-preserved original variability of the MRIZPGB and MGB Montenegrin gene pool represents a valuable source for pre-breeding activities on broadening the white and flint maize breeding programmes under temperate conditions.
Coronary artery fistula is a rare congenital or acquired anomaly. It involves an abnormal connection between the coronary artery and the cardiac chambers or the large thoracic vessels. In some cases, ...the feeding coronary artery can become extremely dilated. The treatment includes a transcatheter or a surgical intervention depending on the complexity of the anomaly. We present the surgical treatment of the coronary artery to coronary sinus fistula, which includes the complete exclusion of the giant right coronary artery and followed by triple bypass surgery.
In this paper, a study was completed investigating the financial viability of a 5 MW solar power plant in Montenegro with direct access to the market, rather than a long-term power purchase ...agreement. The empirical research included an econometric analysis and forecast of the prices on the exchange market, using two methods, autoregressive integrated moving average (ARIMA) and neural network auto regression (NNAR), which are compared to the forecast electricity prices. The former was used in order to obtain the electricity prices forecast, since it showed significantly better predictive performances. Consequently, the financial analysis results indicated this business strategy is a financially more viable option, even though it implies increased risks. All investigated metrics and sensitivity analysis pointed in favor of this option, which has significantly higher profitability with a shorter payback period, compared to the usual market strategy. The main conclusion and recommendation drawn from the analysis are that taking into account the entire environment and prospects for the following years, a riskier business strategy of entering the market directly, or a so-called structured PPA, is put forward to improve project returns and speed up energy-transformation processes in a developing country.
SUMMARY There is a lack of information on differences between organic and conventional soil management practices effects on the soil organic matter and aggregate fractions. ...our research aimed to ...investigate those land-use systems to better understand the relationship between soil organic carbon (SOC) and soil structural properties in field crops production. According to Bronick and Lal (2005) developments of soil structure depends on the soil aggregation processes and mediates many physical soil functions and gives us the understanding of the carbon turnover and distribution in relation to applied management practices. ...quantification of the labile SOM fraction could be better indicator because it is directly controlled by management practices. Since the SOM is a major pool of soil organic carbon (SOC), sensitive to changes in climate or local environment (Schmidt et al., 2011), investigation of fractions that is most prone to land-use changes are required (Ćirić, 2016). Though, an individual approach is required for each farm to assure proper selection of agro-biological measures suitable for pedo-climatic conditions. ...the aim of this study was to investigate differences between organic and conventional land-use systems to better understand the relationship between soil organic carbon (SOC) and structural properties in field crops production.
PDF
