Robust crew pairing for managing extra flights

This paper discusses a modeling approach to robust crew pairing when a set of extra flights is likely to be added to the regular flight schedule. The set of these possible extra flights is known at the planning stage. We demonstrate that these extra flights may be incorporated into the schedule if necessary by modifying the planned crew pairings appropriately and without delaying or canceling existing flights. To this end, we either identify a pair of crews whose schedules may be (partially) swapped while adding an extra flight into the schedule or show that an extra flight may be inserted into the schedule of a crew without affecting others. We note that deadheading may be necessary in either case. For these two types of solutions, we define the appropriate feasibility rules with respect to the common airline regulations. We then propose two robust mathematical programming models that consider incorporating such solutions into the set of selected pairings while keeping the increase in the crew cost at an acceptable level. The baseline solution for comparison is found by a conventional crew pairing model in the literature which ignores robustness at the planning stage and relies on recovery procedures at the time of operation. We also propose the variations of the two models, where the double counting of the possible solutions across extra flights is prevented. Finally, we conduct computational experiments on a set of data generated from the actual data of an airline company. We solve the crew pairing problem both with the proposed robust models and the conventional model. Our results demonstrate the benefits of the proposed modeling approach and indicate that the proposed robust models provide natural options to recovery without disrupting the existing flights at a relatively small incremental cost, which is visible at the planning stage.     

Extracellular Pectinase Production and Purification from a Newly Isolated Bacillus subtilis Strain

Pectinase is widely used in the fruit juice industry with various aspects, especially to reduce blur in fruit juice. To produce pectinase, Bacillus subtilis were isolated from Kilis soil contaminated by agricultural crop wastes. The extracellular pectinase was purified by using three different technics (cell-free supernatant, ethanol, and ammonium sulphate precipitation) and enzyme activity was measured with spectrophotometric analysis. The maximum specific activity was observed in enzyme preparate purified by ethanol precipitation, 217.44 U/mg. The degradation products of reaction–glucose, saccharose, and fructose–were identified by Fourier transform infrared spectroscopy and thin layer chromatography analysis. Two protein bands belong to pectinase of B. subtilis were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Molecular weights of bands were approximately calculated as 60 and 64 kDa.     

Optical and electrical properties of new organic thin film

This paper describes a new organic thin film (OTF) (50 nm) which was deposited by spin coated at room temperature. OTF has been constructed from chemically synthesized poly(pentachlorophenyl methacrylate-co-glycidyl methacrylate). Optical properties of the obtained poly(pentachlorophenyl methacrylate-co-glycidyl methacrylate) in solution were tested by ultraviolet–visible absorption spectroscopy. The analysis of the optical absorption data revealed an existence of a direct and indirect transition optical band gap (E_g). The electrical properties of ITO/PEDOT:PSS/OTF/Al heterojunction structure has been investigated by forward and reverse bias current–voltage (I–V) measurements at room temperature. The main electrical parameters such as barrier height (Φ_Bo), ideality factor (n) and reverse saturation current (I_o) have been calculated by applying thermionic emission theory as 0.80 eV, 3.69, 1.86 × 10^?8 A respectively. Additionally, series resistance (R_s), Φ_Bo and n were calculated from the forward bias I–V data using the methods of Cheung and Cheung with Norde and showed that these methods can be applied successfully for this structure.     

Energy inputs and crop yield relationships in greenhouse winter crop tomato production

In this study, energy use patterns and the relationship between energy inputs and yield for single crop (winter) greenhouse tomato production were examined in Antalya province, one of the most important greenhouse centres in Turkey. Data were collected using face-to-face surveys from 85 farms producing winter greenhouse tomatoes. The results indicated that the bulk of energy was consumed in fertilizer (38.22%), electricity (27.09%), manure (17.33%) and diesel-oil (13.65%). Average yield and energy consumption were calculated as 57,905.1 kg/ha and 61,434.5 MJ/ha, respectively. Results also determined an output–input ratio of 0.8 and a respective energy productivity and specific energy of 1.061 MJ/t and 0.94 kg/MJ. In addition, the Cobb Douglas production function was applied to test the relationship among different forms of energy consumption. The findings suggested that single crop tomato producers must optimize their use of indirect energy resources. Single crop producers applied an excess use of chemicals, resulting in an inverse effect on yield as well as imposing risks to natural resources and human health. This research suggested an expansion in energy use training opportunities to greenhouse farmers in the region.     

Electrolysis of coal slurries to produce hydrogen gas: Relationship between CO2 and H2 formation

The purpose of this study was to produce hydrogen gas by electrolysis of coal slurries and to investigate the relation between hydrogen (H₂) and carbon dioxide (CO₂) formation. Electrolysis of coal slurries was evaluated at 40 °C and 1.0 V cell potential to examine H₂ and CO₂relationship. When electrolysis was performed after the coal slurry was mixed with Fe(II)/Fe(III) ions and stirred overnight (>12 h), no CO₂ gas was observed at the anode compartment. The results of total organic carbon (TOC) indicated that after electrolysis, few organic compounds were transformed into the solution and these organic compounds did not convert into CO₂. GC analysis, on the other hand, revealed that the H₂ collected at the cathode was pure and did not require any further purification process. Hydrogen generation or electrolysis efficiency of coal slurries cannot be calculated or estimated by examining CO₂ generation as reported in the literature. Low temperature and low cell potential were not sufficient to oxidize coal quantitatively.     

Effect of cultivation area and climatic conditions on volatiles of virgin olive oil

To elucidate the influence of the cultivation area and climatic conditions on volatiles of virgin olive oil from Gemlik cultivar, an investigation was carried out. Five Turkish geographical zones (Bal?kesir, Ayd?n, Manisa, Antalya and Hatay) were chosen. From these areas, fruits were collected at the same maturity stage and processed using a small experimental olive oil mill, applying identical processing conditions for all olive samples. Headspace solid‐phase microextraction (HS‐SPME) technique coupled to GC/MS was used for volatile analysis. Twenty‐seven compounds were identified and characterised, representing 96.40–98.74% of the total GC area. The major volatile representing about 50% was the (E)‐2‐hexenal. This compound was found in higher concentrations on olive oils from Antalya than from Hatay area. Hexanal was the second most abundant volatile compound and varied between 13.89 and 28.96%. Comparing the olive growing areas Hatay and Antalya, the hexanal concentration was about 29 and 14%, respectively. Generally, a significant difference in the composition of volatile compounds between the oils from the same olive cultivar and from different geographic regions was recorded. The results suggest that climatic factors, latitude and longitude affect the formation of volatiles.     

Synthesis,characterization and dielectric behavior of (ES)-form polyaniline/cerium(III)-nitrate-hexahydrate composites

In this study, morphological, thermal and dielectric properties of chemically synthesized polyaniline (PANI) and its cerium(III)-nitrate-hexahydrate (Ce(NO₃)₃·6H₂O) doped composites with various doping levels were investigated. Characteristic bands of emeraldine salt (ES)-form of PANI was clearly observed in UV–visible (UV–vis) and Fourier transform infrared (FTIR) spectroscopies. Thermal analyses carried out by Differential scanning calorimetry (DSC) indicated that there was a glass transition at about 70 °C and the doping process increased thermal stability of the polymer. In the surface morphologies examined by scanning electron microscopy (SEM), various microstructures depending on the doping level were observed. Real dielectric constant exhibited a significant decrease due to the increase in the doping level especially at higher frequencies. Conductivity mechanisms of PANI and its composites were investigated by universal power law as conventional models could not provide a complete picture for all the samples. Dramatic increases up to 45, 35 and 30 times in the conductivity of 10% doped PANI were observed for 300, 350 and 400 K, respectively.     

Echocardiographic epicardial adipose tissue measurements provide information about cardiovascular risk in hemodialysis patients

Epicardial adipose tissue (EAT) is a cardiovascular risk predictor in general population. However, its value has not been well validated in maintainance hemodialysis (MHD) patients. We aimed to assess associations of EAT with cardiovascular risk predictors in nondiabetic MHD patients. In this cross‐sectional study, we measured EAT thickness by transthoracic echocardiography in 50 MHD patients (45.8 ± 14.6 years of age, 37 male). Antropometric measurements, bioimpedance analysis, left ventricular (LV) mass, carotis intima media thickness, blood tests, homeostasis model assessment for insulin resistance (HOMA‐IR) and hemodialysis dose by single‐pool urea clearence index (spKt/V) were determined. The mean EAT thickness was 3.28 ± 1.04 mm. There were significant associations of EAT with body mass index (β = 0.590, P < 0.001), waist circumference (β = 0.572, P < 0.001), body fat mass (β = 0.562, P < 0.001), percentage of body fat mass (β = 0.408, P = 0.003), percentage of lean tissue mass (β = ?0.421, P = 0.002), LV mass (β = 0.426, P = 0.002), carotis intima media thickness (β = 0.289, P = 0.042), triglyceride/high‐density lipoprotein cholesterol ratio (β = 0.529, P < 0.001), 1/HOMA‐IR (β = ?0.386, P = 0.006), and spKt/V (β = ?0.311, P = 0.028). No association was exhibited with visfatin C, high‐sensitivity C‐reactive protein, interleukin‐6, and tumor necrosis factor‐alpha (for all, P > 0.05). Body mass index, waist circumference, body fat mass, percentage of lean tissue mass, LV mass, triglyceride/high‐density lipoprotein cholesterol ratio, HOMA‐IR, and spKt/V appeared as independent predictors of EAT. EAT was significantly associated with body fat measures, cardiovascular risk predictors, and dialysis dose in MHD patients.