Single vehicle routing with a predefined customer sequence and multiple depot returns

The optimal routing of a single vehicle with limited capacity that delivers one product to n clients according to a predefined client sequence can be determined using dynamic programming. In the present paper we propose and investigate three practical variations of this problem: (i) the case of multiple-product deliveries when each product is stored in its own compartment in the vehicle, (ii) the case of multiple-product deliveries when all products are stored together in the vehicle’s single compartment, and (iii) the case in which the vehicle picks up from and delivers a single product to each customer. Suitable dynamic programming algorithms that find the optimal routing of the vehicle are developed for each case. The efficiency of the algorithms is studied by solving large problem sets.     

Finite and infinite-horizon single vehicle routing problems with a predefined customer sequence and pickup and delivery

We consider the problem of finding the optimal routing of a single vehicle that starts its route from a depot and picks up from and delivers K different products to N customers that are served according to a predefined customer sequence. The vehicle is allowed during its route to return to the depot to unload returned products and restock with new products. The items of all products are of the same size. For each customer the demands for the products that are delivered by the vehicle and the quantity of the products that is returned to the vehicle are discrete random variables with known joint distribution. Under a suitable cost structure, it is shown that the optimal policy that serves all customers has a specific threshold-type structure. We also study a corresponding infinite-time horizon problem in which the service of the customers is not completed when the last customer has been serviced but it continues indefinitely with the same customer order. For each customer, the joint distribution of the quantities that are delivered and the quantity that is picked up is the same at each cycle. The discounted-cost optimal policy and the average-cost optimal policy have the same structure as the optimal policy in the finite-horizon problem. Numerical results are given that illustrate the structural results.     

Hyperalkaline and thermostable phosphatase inThermus thermophilus

The phosphatases existing in the extreme thermophilic bacteriumThermus thermophilus have been studied. Utilizing ion exchange, hydrophobic, pseudoaffinity, and affinity chromatography, a number of distinct phosphatase activities were identified. At least four phosphatases, with optimum pH ranging between 5.0 and 11.5, were assayed withp-nitrophenylphosphate, and two with optimum pH between 7.0 and 11.0, with³²P-casein as substrate. The authors have focused on the hyperalkaline phosphatase and have tried to purify and characterize it. This hyperalkaline phosphatase reaches a maximal level at the stationary phase of the growth, and is co-purified with alkaline phosphatase with optimum pH of 10.2. The enzymes present a relative mol wt of 65 and 58 kDa, respectively, as judged by SDS-PAGE and Sephadex G-150 column, and possess similar properties, indicating that they are isoforms. These enzymes barely function in the presence of tartrate, and are inhibited by EDTA, pyrophosphate, and molybdate. Among the metals tested, Hg²⁺ appeared as the strongest inhibitor of the hyperalkaline phosphatase. The two enzymes are thermostable and, upon treatment at 90°C for 10 min, 75% of their activity remains. The physiological role and function of these phosphatases need further investigation.     

COMPOSITION OF INDOOR AEROSOLS AT EMPEROR QIN''''S TERRA-COTTA MUSEUM, XI''''AN, CHINA, DURING SUMMER, 2004

Particle samples were collected in August 2004 both inside and outside Emperor Qin's Terra-Cotta Museum in Xi'an, China. Mass and chemical composition of total suspended particles (JSP, particles with aerodynamic diameter less than-30μm), PM2.5(particles with aerodynamic diameter <2.5μm) were determined. The average levels of indoor PM2.5 and TSP were 108.4 and 172.4 μg·m-3, respectively, with PM2.5 constituting 62.9% of the TSP mass. Sulfate ((32.4±6.2)%), organics ((27.7±8.0)%), and geological material ((12.5±3.4)%) dominated indoor PM2.5, followed by ammonium ((8.9±2.8)%), nitrate ((7.0±2.9)%), and elemental carbon (EC, (3.9±1.5)%). Particle size distribution varied with the number of tourists in the museum. The size of sulfate, organics, EC, nitrate, and ammonium was found to vary in the range of 0.43 to 3.3 μm in fraction. Ion balance indicated that the aerosol was acidic, with insufficient ammonium ions to neutralize the sulfuric and nitric acids. High concentrations of acidic aerosols will erode the Terra-cotta warriors and horses especially in the summer season with high temperature (30℃) and relative humidity (70%) and undesirable solar radiation inside the museum. More attention should be paid to protecting these precious antiques made 2000 years ago.     

Optimal maintenance of a production-inventory system with idle periods

In this paper we consider a production-inventory system in which an input generating installation supplies a buffer with a raw material and a production unit pulls the raw material from the buffer with constant rate. The installation deteriorates in time and the problem of its optimal preventive maintenance is considered. It is assumed that the installation after the completion of its maintenance remains idle until the buffer is evacuated. Under a suitable cost structure it is shown that the average-cost optimal policy for fixed buffer content is of control-limit type, i.e. it prescribes a preventive maintenance of the installation if and only if its degree of deterioration is greater than or equal to a critical level. Using the usual regenerative argument, the average cost of a control-limit policy is computed exactly and then, the optimal control-limit policy is determined. Furthermore, the stationary probabilities of the system under the optimal policy are computed.     

The mass spectral fragmentation of some substituted 3-Amino-2-salicylideneamino-benzofurans

Electron impact mass spectra of eight of the title compounds are discussed. The important fragment ions are shown by high resolution and deuterium labelling to contain the benzofuran nucleus and to involve extensive rearrangement processes. Fragmentation pathways have been confirmed by measurement of daughter ion spectra (B/E linked scans).     

Fluorescence spectra measurement of olive oil and other vegetable oils

Fluorescence spectra of some common vegetable oils, including olive oil, olive residue oil, refined olive oil, corn oil, soybean oil, sunflower oil, and cotton oil, were examined in their natural state, with a wavelength of 360 nm used as excitation radiation. All oils studied, except extra virgin olive oil, exhibited a strong fluorescence band at 430-450 nm. Extra virgin olive oil gave a different by interesting fluorescence spectrum, composed of 3 bands: one low intensity doublet at 440 and 455 nm, one strong at 525 nm, and one of medium intensity at 681 nm. The band at 681 nm was identified as the chlorophyll band. The band at 525 nm was at least partly derived from vitamin E. The low intensity doublet at 440 and 455 nm correlated with the absorption intensity at 232 and 270 nm of olive oil. The measurements of these fluorescence spectra were quick (about 5 min) and easy and could possibly be used for authentification of virgin olive oil.     

Xanthan gum production by Xanthomonas campestris w.t. fermentation from chestnut extract

Xanthomonas campestris w.t. was used for production of xanthan gum in fermentations with chestnut flour for the first time. Fermentations were carried out with either chestnut flour or its soluble sugars (33.5%) and starch (53.6%), respectively, at 28°C and 200 rpm at initial pH 7.0 in flasks. The effect of agitation rate (at 200, 400, and 600 rpm) on xanthan gum production was also studied in a 2-L batch reactor. It was found that xanthan production reaches a maximum value of 3.3 g/100 mL at 600 rpm and 28°C at 45 h.