Which string instrument probably originated in the middle east?

The Oud is a string instrument probably originated in the Middle East. The Oud is a central instrument of Arabic music it has an ancient history. It is probably originated 3,500 years ago in Persia, where it was called at Barbat. The string is made of gut and now are made of plastic. 

Efficiency improvement

Technology advancements have improved efficiency levels significantly since the 1970s. Improvements of computational methods, supported by model turbine testing, have facilitated three-dimensional blade design to improve blade performance. Advanced sealing reduces losses from leakages and longer blades are in use based on modern material technologies. The conversion of double flow stages or modules to single flow stages or modules can give significant efficiency improvements due to the increase in blade height.

Improvements have also been realised by optimising the number of stages and by selecting the appropriate technology type for the application. Walker6 published a comprehensive summary. For fossil-fired cycles or an advanced gas-cooled reactor (AGR) a more efficient HP turbine comes with a reduced HP exhaust temperature and therefore reduces reheater inlet temperature. Slight additional heat input to the reheated steam is therefore required if the IP turbine inlet temperature is to remain at pre-retrofit level. If no additional heat is available it is important to understand that the reduced temperature will carry through the reheater to the IP turbine inlet and reduce the retrofit benefit, impacting on heat rate and power. More details on the individual effects are discussed in section 14.4.8. Adding to the reheater surface can increase the reheat input and retrofit benefit.