Polling algorithm based on traffic burst characteristics of broadband wireless access systems

In this paper, we propose a novel polling algorithm to decrease the number of idle slots and collission slots during the polling cycle by evaluating the bandwidth request of the subscribe stations (SSs) in the next polling cycle for broadband wireless access (BWA) systems. We firstly analyze the feature of silent time intervals and deduce the Hurst index which symbolizes the degree of self-similarity and long-relative nature. Then we represent the inactive OFF time intervals by the Pareto model and estimate the shape parameter α by the group measured data. Finally we can evaluate the transmission probability of a silent SS before the next polling cycle. By this algorithm, we can find the optimal transmission opportunities for the base station (BS) to achieve the least collision or void timeslots in order to achieve the largest bandwidth efficiency. The theoretical analysis and simulation results show that this polling algorithm can improve the performance for BWA system.     

Universal jurisdiction as obligation to prosecute or extradite

Before searching for new legal solutions to manage maritime piracy problems, especially those related to jurisdiction, it is essential to examine and analyse the existing international legal framework to determine whether current international legal instruments are already appropriate to face off this threat. One such principle is the “Aut dedere aut iudicare” principle, which has been also codified into SUA Convention, at art. 6 par. 4. This obligation comes from an international treaty, so it cannot be disregarded by any state (short of becoming susceptible to international liability), neither can it be amended by a national law. If a state party has inadequate law resources to establish its jurisdiction, or if unable or unwilling to prosecute the pirate, then such state party has no choice but extradite the pirate. If we consider the above principle as a conventional obligation, then it should be limited only to state parties, and it should be applied only under conditions stated by SUA Convention. Instead, if we consider it as a customary law principle, because piracy—as crimen iuris gentium—offends international community as a whole, then such principle shall be binding without any limit or condition.     

A novel de-noising method based on discrete cosine transform and its application in the fault feature extraction of hydraulic pump

Aiming at the existing problems of discrete cosine transform (DCT) de-noising method, we introduce the idea of wavelet neighboring coefficients (WNC) de-noising method, and propose the cosine neighboring coefficients (CNC) de-noising method. Based on DCT, a novel method for the fault feature extraction of hydraulic pump is analyzed. The vibration signal of pump is de-noised with CNC de-noising method, and the fault feature is extracted by performing Hilbert-Huang transform (HHT) to the output signal. The analysis results of the simulation signal and the actual one demonstrate that the proposed CNC de-noising method and the fault feature extraction method have more superior ability than the traditional ones.     

Calculation on the solid solution forming enthalpies of Re-Mo-Ti gradient alloy in thermodynamics

The idea about preparation of Re-Mo-Ti alloy is put forward because of applications of Re and Mo-Re alloys in aerospace. Basing on the thermodynamics theory, the feasibility of developing a new high temperature alloy Re-Mo-Ti is investigated. The solid solution forming enthalpies of binary alloys Re-Ti, Mo-Ti and Mo-Re are calculated with the Miedema thermodynamics theory. The Miedema theory of binary alloy can be used in ternary alloy through Kohler model or Toop model. The calculated results show that the forming enthalpies of binary alloys Re-Ti, Ti-Mo and Re-Mo are negative, which indicates that binary alloys Re-Ti, Ti-Mo and Re-Mo can form solid solution in wider component area. The forming enthalpies of Re-Mo-Ti ternary alloy are still negative and smaller than those of binary alloys Re-Ti, Ti-Mo or Re-Mo, which indicates it is possible to form large solid solution graph area among ternary alloys of Ti, Mo, Re elements. It is feasible to develop a new high temperature material in thermodynamics, in this material Re-Mo-Ti solid solution as base phase, and the Ti₅Re₂₄ intermetallic compounds or interphase ω (Ti₄Mo₃) as strengthening phase.     

Proficiency improvement method in maritime education

The research conducted by the International Maritime Organization (IMO) shows that maritime education not always reaches its pre-established goal. One of the aspects in maritime education development process with the aim to prepare ship officers and other specialists is a thorough selection of the learning content according to real life necessities. Structuring the learning content of the subjects, both significant to profession and conforming to the requirements set by professional bodies, is one of the key issues addressed by curriculum developers. The aim of this research is to create a model for the curriculum development in scientific subjects for outcome-based maritime education. The main criterion which determines the significance/contribution level of the included topic in the curriculum is the anticipated learning outcome increasing the level of proficiency in students. Thus, the present research unveils the necessary steps for the evaluation of the proposed topics in the context of teaching/learning and gives grounds for their selection and the arrangement of topics in a logical order for further implementation in teaching/learning process. The present research is illustrated by a case study concerning the development of teaching/learning content for chemistry curriculum as a study subject in the secondary vocational maritime education programme.     

Analysis of ship drifting in a narrow channel using Automatic Identification System (AIS) data

With maritime transportation has played an important role in global economy development, ship traffic has become more congested. Therefore, ships navigate under risk conditions, and thus maritime accidents have occurred frequently. Especially, ship passing through a narrow channel is even more dangerous. Because, the ships are easy to be affected by external forces such as wind and currents that can cause ship drifts. Many latent risks are present during navigation. In order for the development of a sensible and appropriate traffic model for the safety and efficiency ship navigation, this study has focused on the actual ship behavior to understand the ship drift in the Kurushima Strait, Japan, which is one of the most dangerous routes in Japan. The analysis of ship behavior was carried out using the Automatic Identification System (AIS) data. As a result, the ships drift was understood in detail, and the latent risk was unveiled when ships pass through the narrow route. Moreover, the risk areas were obtained and visualized by the ship drift behavior analysis. The obtained results can be applied to ensure safe navigation and the development of an eco-friendly and economy efficient for ship navigation.     

Analyzing the dispersion of cargo vapors around a ship’s superstructure by means of wind tunnel experiments

In a previous study, it was found that cargo tank operations like cleaning and venting, lead to higher cargo vapor concentrations around the ship’s superstructure. Can wind tunnel experiments confirm these findings? Is there an improvement when using higher outlets at high velocities compared to lower outlets with a low outlet velocity? Is there a relation between relative wind speed and measured concentration? These questions were investigated in the Peutz wind tunnel. By using a tracer gas for the wind tunnel experiments, concentration coefficients have been calculated for various settings. The study shows that using high-velocity outlets is an efficient way to keep concentrations as low as possible. The only exception is for relative wind directions from the bow. In this last case using a manhole as ventilation outlet leads to lower concentrations. With increasing wind speeds the building downwash effect resulted in higher concentration coefficients near the main deck. This study confirms our on-board measurements and suggests the lowering of the ventilation inlet of the accommodation, so that the high-velocity outlet can be used safely at all times.     

Optimization of integrated scheduling of handling and storage operations at automated container terminals

Increasing demand for containerization compels container terminals to improve their performance. Uncoordinated scheduling of operations is one of the main factors accounting for poor performance at automated container terminals (ACTs). To increase land utilization efficiency and lower operational times, a new storage system called the split-platform automated storage/retrieval system (SP-AS/RS) has been introduced for temporary storage of containers. This paper describes a multi-objective mixed-integer programming (MIP) model that is based on a combination of multiple interacting sub-tasks. It is aimed at optimizing the integrated scheduling of handling and storage operations in ACTs. The MIP model objective function is to minimize delays in the loading/unloading tasks of the cranes and the travel time of vehicles and platforms in the SP-AS/RS. At the same time, a simulated annealing algorithm (SAA) that provides near-optimal solutions for the problem in a reasonable computation time is appraised. The results of this study show that the objective function of the MIP model is, on average, 58 % lower than that of the non-integrated scheduling method. On the other hand, the best objective function values obtained by the SAA indicate only a 3.7 % disadvantage in comparison with optimal values determined by the MIP model, demonstrating that the SAA is able to provide near-optimal solutions for the integrated scheduling of handling and storage operations.     

Robust principal component analysis via truncated nuclear norm minimization

Robust principal component analysis(PCA) is widely used in many applications, such as image processing, data mining and bioinformatics. The existing methods for solving the robust PCA are mostly based on nuclear norm minimization. Those methods simultaneously minimize all the singular values, and thus the rank cannot be well approximated in practice. We extend the idea of truncated nuclear norm regularization(TNNR) to the robust PCA and consider truncated nuclear norm minimization(TNNM) instead of nuclear norm minimization(NNM). This method only minimizes the smallest N-r singular values to preserve the low-rank components, where N is the number of singular values and r is the matrix rank. Moreover, we propose an effective way to determine r via the shrinkage operator. Then we develop an effective iterative algorithm based on the alternating direction method to solve this optimization problem. Experimental results demonstrate the efficiency and accuracy of the TNNM method. Moreover, this method is much more robust in terms of the rank of the reconstructed matrix and the sparsity of the error.     

Research on gray system and quantitative model about the fund-raising ability to China private equity fund

It is a rather challenging project to seek the amount of funds raised by funds-raising companies. This paper is focused on China private equity funds that have succeeded in raising their funds. The grey systemic model is applied in the research and a formula is established for the law of fund-raising of the private equity funds in order to sum up the capacity of China private equity investment funds and to establish a model accordingly.