are driven by human life support systems, scientific exploration and Earth observation equipment, telecommunications, and electric propulsion systems. There is great interest in highly efficient perovskite-structured thin-film solar cells for space applications. [1,2] These are promising candidates due to their excellent optoelectronic characteristics, low-cost, high performance, [2][3][4] and their facile manufacturability [5] potentially suitable for in-space manufacturing. [6] These traits coupled with their defect tolerance, [7,8] and radiation tolerance [9] have garnered interest for aerospace applications. Prior to the widespread implementation of metal halide perovskites (MHPs) into the space environment, solar cells must pass rigorous American Institute of Aeronautics and Astronautics Standard 111 (AIAA-S111) space qualification testing. [10] Low earth orbit (LEO), 160-2000 km above the Earth's surface, is an ideal place to operate MHPs either on the International Space Station or on satellites. The harsh environment of LEO includes thermal cycling (±120 ⁰C), vacuum (10 −6 -10 −9 torr), ultra-violet radiation, exposure to atomic oxygen (flux 10 13 -10 15 AO/cm 2 with collision energy of 5 eV), plasma (10 6 cm −3 , ≤1 eV electron temperature), and ionizing radiation of electrons, protons, micrometeoroids (60 km s −1 ) and orbital debris (10 km s −1 ). [11] We must demonstrate MHP durability in relevant space environments to evidence feasibility. Implementing Metal halide perovskites (MHPs) have emerged as a prominent new photovoltaic material combining a very competitive power conversion efficiency that rivals crystalline silicon with the added benefits of tunable properties for multijunction devices fabricated from solution which can yield high specific power. Perovskites have also demonstrated some of the lowest temperature coefficients and highest defect tolerance, which make them excellent candidates for aerospace applications. However, MHPs must demonstrate durability in space which presents different challenges than terrestrial operating environments. To decisively test the viability of perovskites being used in space, a perovskite thin film is positioned in low earth orbit for 10 months on the International Space Station, which was the first long-duration study of an MHP in space. Postflight high-resolution ultrafast spectroscopic characterization and comparison with control samples reveal that the flight sample exhibits superior photo-stability, no irreversible radiation damage, and a suppressed structural phase transition temperature by nearly 65 K, broadening the photovoltaic operational range. Further, significant photo-annealing of surface defects is shown following prolonged light-soaking postflight. These results emphasize that methylammonium lead iodide can be packaged adequately for space missions, affirming that space stressors can be managed as theorized.
Aerospace In article number 2203920, Lyndsey McMillon‐Brown, Sayanatani Ghosh, and co‐workers report on the first long duration space flight of a metal halide perovskite photoactive layer on the International Space Station. Post‐flight analysis reveals that samples exhibit superior photo‐stability, no irreversible radiation damage, and a suppressed structural phase transition temperature, broadening the photovoltaic operational range. These results confirm that perovskite photovoltaics can be designed to endure the space environment.
Introduction The Zamzama gas field is located in the Kirthar Foldbelt, Sindh Province, Pakistan approximately 200 km north of Karachi and importantly, only 8km west of the existing Sui-Karachi pipeline (Figure 1). Since discovery in early 1998, a number of innovative approaches to field appraisal, gas marketing, infrastructure rationalisation and field development have been undertaken. This has resulted in the successful completion of the initial development phase, Phase 1, with the Zamzama gas plant coming on stream in July 2003. In addition, plans are well progressed towards realising an incremental Phase 2 development. Cornerstone to the success of development to date has been the implementation of an extended well test (EWT) of the exploration (Zamzama-1/ST1) and appraisal well (Zamzama-2), which came on line in early 2001. The EWT mitigated an entire host of perceived risks associated with a full development, with minimal financial exposure. This paper will examine:The evolution of the initial appraisal programme and its unfolding to dramatically narrow gas reserve uncertainty prior to significant production.The results of the successful Phase 1 development drilling programme and associated further field appraisal.Data collection and analysis and how this has been leveraged. Structural And Geologic Overview The Zamzama structure comprises a large north-south orientated, eastward verging thrusted anticline (Figure 2). The Late Cretaceous Pab sandstone forms the primary hydrocarbon reservoir in the Kirthar Foldbelt and the main reservoir in both the Zamzama and nearby Bhit gas field (Figure 3). At Zamzama, gas is also reservoired in sandstones of the overlying Khadro Formation of Paleocene age. Both the Pab and Khadro reservoirs are of relatively uniform thickness across the entire Zamzama structure. The Khadro formation averages 54m in thickness and varies by less than +/− 3m over an area of more than 150 km2. The Pab formation averages 216m in thickness and where fully penetrated varies by +/− 5m. The Pab Formation conformably overlies the Fort Munro Limestone, which is non-net at Zamzama. Top seal for both the Khadro and Pab reservoirs is provided by marine shales of the Girdo (Ranikot) Formation (Figure 4). The Pab is part of a sand-rich fluvio-deltaic, coastal plain and shoreface depositional system (Figure 5). The Khadro is a more heterogeneous reservoir and of poorer quality compared to the Pab due to the presence of volcaniclastics. The Khadro sands were deposited in a marginal marine-estuarine environment following the deposition of red-brown fluvial floodplain mudstones, which comprise the lower two thirds of the Khadro. The majority of the calculated gas volume (80%) is contained within the core area of the hangingwall (Figure 6). The remainder of the volume is distributed equally between the northern and footwall regions. Wells drilled in a more crestal location (Zamzama-2, −4/ST3 and −5) encounter gas on rock where the top Fort Munro, non-net limestone, is above the gas-water contact (GWC). The Pab formation is distributed extensively throughout the region and outcrops to the south of Zamzama in the Laki ranges. A strong active aquifer is expected throughout production life.
Recent federal court decisions have emphasized the need to eliminate schools whose racial composition varies from that of the whole district by more than a fixed percent. A linear programming model is presented to assist school administrators in developing desegregation plans that comply with these guidelines. An efficient solutional technique that exploits the special structure of this model increases problem‐size capabilities. A study of the Columbus City School District examines the tradeoffs involved at different levels of desegregation.
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