The image displays a close-up, top-down view of several technical documents on a flat, light-colored surface in the city of Byala Palanka, Bulgaria

The image displays a close-up, top-down view of several technical documents on a flat, light-colored surface in the city of Byala Palanka, Bulgaria. The primary subject is a partially visible sheet of paper, likely from a binder, containing both typed and handwritten content in Bulgarian (Cyrillic script). The upper right portion of this main document features typed text, including a heading that translates to "Speed characteristic of a diesel..." and mentions "A diesel engine of brand "HOLSET" is tested." Below this, "Table 1. Data from testing a diesel engine..." presents a grid with numerical data in columns labeled "n [min^-1]", "Me [Nm]", "Ne [kW]", "ge [g/kWh]", and "Gh [kg/h]", indicating engine performance parameters. Further typed text at the bottom right includes phrases such as "from calculated data:", "[kg\\m^3]", and "throttle device efficiency," along with instructions to plot curves: "The curves are Sn, ge = f(n); = f(n)." Overlapping the typed text on the left side of the main document are extensive handwritten notes in blue ink. These cursive notes, also in Bulgarian, appear to be explanatory text or calculations related to the technical content. One discernible phrase mentions "of reality for dissipations." The lower left section of the main document features a hand-drawn graph in pen, overlaid on printed grid lines. This graph illustrates several curves labeled "Me," "Ne," "gc min," "ge," and "n," which represent typical engine performance characteristics such as torque, power, minimum specific fuel consumption, specific fuel consumption, and rotational speed. Arrows and vertical lines indicate specific points or ranges on the graph, with the x-axis labeled "n." A smaller, partially visible document with typed and handwritten notes in blue ink is present in the upper left, partially obscured by the main paper. The dark edge of a binder or folder, possibly black, is visible along the bottom right, securing the main document. No people are visible.