Определение оптимального числа причалов в порту

Определение числа грузовых причалов является одной из основных задач, решаемых при проектировании морских терминалов. Согласно Нормам технологического проектирования морских портов, потребное число грузовых причалов определяется в зависимости от грузооборота порта, месячной пропускной способности и коэффициента занятости причала. Для контейнерных терминалов значение коэффициента занятости причала рекомендуется принимать равным 0,4-0,5. В статье показано, что такой подход к определению оптимального числа причалов является не вполне корректным и может приводить к существенным просчетам. В статье рассматривается более корректный метод решения задачи с применением методов теории массового обслуживания. В качестве критерия оптимальности используется комплексный оценочный показатель минимальные суммарные издержки вследствие простоев судов и причалов.Number of berths is one of the key parameters in the design of a port terminal. The Guidelines for the design of seaports approved by the Ministry of Transport suggest that the number of berths should be determined using a formula which is based mainly on the cargo throughput, the ship loading (discharging) rate and the berth occupancy factor. For container terminals the recommended value of the berth occupancy factor is 0.4-0.5. The aim of this article is to show that such approach to determining the optimum number of berths in a seaport can be quite misleading because it ignores the fact that optimum berth utilization is dependent on a number of various factors and can vary over a very widerange. A more accurate queueing-theory-based approach to determining the optimum number of berths is proposed.

Tetrakis(dimethoxyboryl)methane

The title compound, tetrakis(dimethoxyboryl)methane (systematic name: octamethyl methanetetrayltetraboronate), C9H24B4O8or C[B(OMe)2]4, is a useful synthetic intermediate. Crystals of this compound at 102 K conform to the orthorhombic space groupPbcn. The molecules, which reside on sites of crystallographic twofold symmetry, have idealized -4 point symmetry like most other CX4molecules in which eachXgroup bears two non-H substituents at the 1-position. The central C atom has a slightly distorted tetrahedral coordination geometry, with C—B bond lengths of 1.5876 (16) and 1.5905 (16) Å. One of the methoxy groups is disordered over two sets of sites; the major component has an occupancy factor of 0.676 (8).

Buprenorphine

In the crystal structure of a semi-synthetic opioid drug buprenorphine, C29H41NO4{systematic name: (2S)-2-[(5R,6R,7R,14S)-9α-cyclopropylmethyl-3-hydroxy-6-methoxy-4,5-epoxy-6,14-ethanomorphinan-7-yl]-3,3-dimethylbutan-2-ol}, the cyclopropylmethyl group is disordered over two sites with an occupancy factor of 0.611 (3) for the major component. One of the hydroxy groups is involved in intramolecular O—H...O hydrogen bond. The other hydroxy group acts as a proton donor in an intermolecular O—H...O interaction that connects molecules into a zigzag chain along thebaxis.

4-tert-Butylpyridinium chloride–4,4′-(propane-2,2-diyl)bis(2,6-dimethylphenol)–toluene (2/2/1)

In the title solvated salt, C9H14N+·Cl−·C19H24O2·0.5C7H7, two molecules of 4,4′-(propane-2,2-diyl)bis(2,6-dimethylphenol) are linkedviaO—H...Cl hydrogen bonds to two chloride ions, each of which is also engaged in N—H...Cl hydrogen bonding to a 4-tert-butylpyridinium cation, giving a cyclic hydrogen-bonded entity centred at 1/2, 1/2, 1/2. The toluene solvent molecule resides in the lattice and resides on an inversion centre; the disorder of the methyl group requires it to have a site-occupancy factor of 0.5. No crystal packing channels are observed.

K6[Fe8.27(HPO3)12]: a new mixed-valence iron phosphite

The title compound, hexapotassium octairon(II,III) dodecaphosphonate, exhibiting a two-dimensional structure, is a new mixed alkali/3dmetal phosphite. It crystallizes in the space groupR\overline{3}m, with two crystallographically independent Fe atoms occupying sites of \overline{3}m(Fe1) and 3m(Fe2) symmetry. The Fe2 site is fully occupied, whereas the Fe1 site presents an occupancy factor of 0.757 (3). The three independent O atoms, one of which is disordered, are situated on a mirror and all other atoms are located on special positions with 3msymmetry. Layers of formula [Fe3(HPO3)4]2−are observed in the structure, formed by linear Fe3O12trimer units, which contain face-sharing FeO6octahedra interconnected by (HPO3)2−phosphite oxoanions. The partial occupancy of the Fe1 site might be described by the formation of two [Fe(HPO3)2]−layers derived from the [Fe3(HPO3)4]2−layer when the Fe1 atom is absent. Fe2+is localized at the Fe1 and Fe2 sites of the [Fe3(HPO3)4]2−sheets, whereas Fe3+is found at the Fe2 sites of the [Fe(HPO3)2]−sheets, according to bond-valence calculations. The K+cations are located in the interlayer spaces, between the [Fe3(HPO3)4]2−layers, and between the [Fe3(HPO3)4]2−and [Fe(HPO3)2]−layers.

Bis(dipyridin-2-ylamine-κ2N2,N2′)palladium(II) dinitrate

The asymmetric unit of the title compound, [Pd(C10H9N3)2](NO3)2, contains one half of a cationic PdIIcomplex and one NO3−anion. In the complex, the PdIIion is four-coordinated by four pyridine N atoms derived from the two chelating dipyridin-2-ylamine (dpa) ligands. The PdIIatom is located on an inversion centre, and thus the PdN4unit is exactly planar. The dpa ligand itself is not planar, showing a dihedral angle between the pyridine rings of 39.9 (1)°. The anions are connected to the complex by intermolecular N—H...O hydrogen bonds between the two O atoms of the anion and the N—H group of the cation. Weak intermolecular C—H...O hydrogen bonds additionally link the constituents in the crystal structure. The NO3−anion was found to be disordered over two sites with a site-occupancy factor of 0.55 (10) for the major component.

Determination of site occupancies by the intermeasurement minimization method. I. Anomalous scattering usage for noncentrosymmetric crystals

New methods for the determination of site occupancy factors are described. The methods are based on the analysis of differences between intensities of Friedel reflections in noncentrosymmetric crystals. In the first method (Anomalous-Expert) the site occupancy factor is determined by the condition that it is identical for two data sets: (1) initial data without averaging of Friedel intensities and (2) data that are averaged on Friedel pairs after the reduction of the anomalous scattering contribution. In the second method (anomalous anisotropic intermeasurement minimization method, Anomalous-AniMMM) the site occupancy factor is refined to satisfy the condition that the differences between the intensities of Friedel reflections that are reduced on the anomalous scattering contribution must be minimal. The methods were checked for three samples of RbTi1−xZrxOPO4crystals (A,BandC) with KTiOPO4structure, at 295 and 105 K (five experimental data sets). Microprobe measurements yield compositionsxA,B= 0.034 (5) andxC= 0.022 (4). The corresponding site occupancy factors areQA,B= 0.932 (10) andQC= 0.956 (8). Using Anomalous-AniMMM and three independent refinements for the first and second samples, the initial occupancy factor ofQA,B= 0.963 (15) was improved toQA,B= 0.938 (7). Of the three room-temperature data sets, one was improved toQA,B= 0.934 (2). For the third sample and one data set, the initial occupancy factor ofQC= 1.000 was improved toQC= 0.956 (1). The methods improve the Hirshfeld rigid-bond test. It is discussed how the description of chemical bonding influences the site occupancy factor.