DEVELOPMENT OF A MODEL FOR THE DYNAMICS OF PROBABILITIES OF STATES OF SEMI-MARKOV SYSTEMS

The subject is the study of the dynamics of probability distribution of the states of the semi-Markov system during the transition process before establishing a stationary distribution. The goal is to develop a technology for finding analytical relationships that describe the dynamics of the probabilities of states of a semi-Markov system. The task is to develop a mathematical model that adequately describes the dynamics of the probabilities of the states of the system. The initial data for solving the problem is a matrix of conditional distribution laws of the random duration of the system's stay in each of its possible states before the transition to some other state. Method. The traditional method for analyzing semi-Markov systems is limited to obtaining a stationary distribution of the probabilities of its states, which does not solve the problem. A well-known approach to solving this problem is based on the formation and solution of a system of integral equations. However, in the general case, for arbitrary laws of distribution of the durations of the stay of the system in its possible states, this approach is not realizable. The desired result can only be obtained numerically, which does not satisfy the needs of practice. To obtain the required analytical relationships, the Erlang approximation of the original distribution laws is used. This technique significantly increases the adequacy of the resulting mathematical models of the functioning of the system, since it allows one to move away from overly obligatory exponential descriptions of the original distribution laws. The formal basis of the proposed method for constructing a model of the dynamics of state probabilities is the Kolmogorov system of differential equations for the desired probabilities. The solution of the system of equations is achieved using the Laplace transform, which is easily performed for Erlang distributions of arbitrary order. Results. Analytical relations are obtained that specify the desired distribution of the probabilities of the states of the system at any moment of time. The method is based on the approximation of the distribution laws for the durations of the stay of the system in each of its possible states by Erlang distributions of the proper order. A fundamental motivating factor for choosing distributions of this type for approximation is the ease of their use to obtain adequate models of the functioning of probabilistic systems. Conclusions. A solution is given to the problem of analyzing a semi-Markov system for a specific particular case, when the initial distribution laws for the duration of its sojourn in possible states are approximated by second-order Erlang distributions. Analytical relations are obtained for calculating the probability distribution at any time.

Dispersal of earthworms from the Rudny Altai (Kazakhstan) into Western Siberia

The aim of our study was to determine the current distribution, habitats, ecology, and possible dispersal routes of three species of the Rudny Altai (East Kazakhstan): Eisenia tracta, E. nana, and E. ventripapillata. We found that these species dispersed far beyond their original distribution into the flatland part of western Siberia (Russia) up to the central forest steppe of the Omsk oblast. E. tracta, E. nana, and E. ventripapillata were found in both floodplains and interfluvials. Hydrochory was the most plausible way of northward dispersal, while on interfluvials, they were probably introduced by humans. The studied species showed no preference for a particular habitat or river bank. The habitats were diverse and significantly different from the original ones in Rudny Altai. The factors that allowed E. tracta, E. nana, and E. ventripapillata to colonize western Siberia were probably their wide tolerance range to soil pH, temperature, density, and humidity, along with the decrease of winter soil freezing in recent decades. This is the first information about the occurrence of these species of earthworms in Siberia.

A MATHEMATICAL APPROXIMATION TO LEFT-SIDED TRUNCATED NORMAL DISTRIBUTION BASED ON HART’S MODEL

Left-sided truncated distributions (LSTD) have been found in different situations in the industry. For example, the life distribution of used devices is left-sided truncated distribution. Moreover, if a lower specification exists without the upper specification limit, the product distribution is truncated from the left side. Left-sided truncated normal distributions (LSTND) is a special case where the original distribution is normal. LSTND characteristics, as well as cumulative densities and probabilities can be difficult to employ manually, with most practitioners relying largely on specialized (and expensive) software. In many cases, practitioners are against purchasing software, as they are often limited in the number of estimations. The paper will provide an accurate and straightforward approximation to the cumulative density of LSTND. Hart’s normal distribution is simplified and used as a foundation of this model. The maximum absolute error for the curve at different truncation points (i.e., ZL) over the definition range (i.e., [zL: ∞]) is as follows: 0.004303 for ZL=-4, 0.00432 for ZL=-3, 0.00449 for ZL=-2, 0.005727 for ZL=-1, and 0.0106 for ZL=0. Even the maximum errors are very ignorable in probability applications. Further, it is rare to find a truncation point of higher than -2 in the industry.

Determination of Transport Routes using the Saving Matrix Method at PT XYZ

PT XYZ is a company engaged in manufacturing that produces electronic components and installation services for these components. In this study, the company will send components and help install them in nine locations in Sumatra. The analysis of determining distribution routes uses the saving matrix method. The results of the analysis using the saving matrix method show that the original distribution distance of 9926 kilometers can be reduced to 2937.7 kilometers, which means that the distance can be shortened and more efficient by 70% or around 6988.3 kilometers. The original cost was Rp. 54,386 .000 down to Rp. 16,716,000 Thus there is a distribution channel savings of Rp. 37,670,000 or about 69.2%.

A partial knowledge of friends of friends speeds social search

Milgram empirically showed that people knowing only connections to their friends could locate any person in the U.S. in a few steps. Later research showed that social network topology enables a node aware of its full routing to find an arbitrary target in even fewer steps. Yet, the success of people in forwarding efficiently knowing only personal connections is still not fully explained. To study this problem, we emulate it on a real location-based social network, Gowalla. It provides explicit information about friends and temporal locations of each user useful for studies of human mobility. Here, we use it to conduct a massive computational experiment to establish new necessary and sufficient conditions for achieving social search efficiency. The results demonstrate that only the distribution of friendship edges and the partial knowledge of friends of friends are essential and sufficient for the efficiency of social search. Surprisingly, the efficiency of the search using the original distribution of friendship edges is not dependent on how the nodes are distributed into space. Moreover, the effect of using a limited knowledge that each node possesses about friends of its friends is strongly nonlinear. We show that gains of such use grow statistically significantly only when this knowledge is limited to a small fraction of friends of friends.

Vegetation diversity and structure of urban parks in Cilegon City, Indonesia, and local residents’ perception of its function

Muhlisin, Iskandar J, Gunawan B, Cahyandito MF. 2021. Vegetation diversity and structure of urban parks in Cilegon City, Indonesia, and local residents’ perception of its function. Biodiversitas 22: 2589-2603. The existence of urban parks is very essential for cities because they provide ecosystem services and benefits to humans. Diversity and structure of vegetation in urban parks play significant role in delivering several functions of ecosystem services. This paper aims to explore and analyze the vegetation diversity and structure, as well as ecosystem services of eight urban parks in Cilegon City, Banten Province, Indonesia. Vegetation analysis and residents’ perception are also conducted in this research. The analysis of vegetation is focused on horizontal structure of vegetation,including plant diversity, plant habitus, the original distribution of the plants, and vertical structure of vegetation (canopy stratification and vegetation profile). The residents’ perceptions are collected using interviews of selected respondents. The identification of vegetation recorded 114 plant species from 46 families are found in the concerned urban parks, however, the diversity and species richness in these parks tended to be low. The vegetation communities are uncertain and dominated primarily by non-native and invasive species. The canopy stratification is relatively homogeneous with the dominant plants having less than one meter in height, such as Ruellia simplex and Syzygium paniculatum. The vegetation planted in the urban parks are mostly ornamental plants that provide much more aesthetic function rather than ecological purpose, daily human needs, or other ecosystem services. This fact shows that urban parks in the study area have only few ecosystem services, hence they need some improvements in order to have more environmental services and to be able to enjoy more by the community.

Phylogeny of Anisepyris Kieffer (Hymenoptera: Bethylidae: E pyrinae), with investigation of diagnostic features

A cladistic analysis based on 120 morphological characters and 72 OTUs was conducted for the flat wasp genus Anisepyris Kieffer. The genus is mainly Neotropical region with few Nearctic species. The analysis retrieved well-supported relationships among the Anisepyris species and exposed the distribution of synapomorphies among the lineages, particularly concerning the mandible shape, dorsal pronotal area sulcus, and mesopleural foveae. The main diagnostic characters, described by Barbosa and Azevedo (2018) for the 13 species-groups of Anisepyris, were scrutinized. Transformation series and evolutionary hypotheses were also discussed. This discussion elucidates the importance of each character in the evolution and diversification along the different lineages. A discussion on the species-groups distribution is proposed, in relation to their diagnostic features. A hypothesis about the original distribution and the subsequent diversifications was also discussed. In conclusion, due to a possible recent origin for Anisepyris species, the dispersion could be related primarily to dense forest areas; and the retrieved synapomorphies could be related to posterior distributions of the species in disparate areas from their original environment.

Improvement of Mechanical Properties of Cu/Graphene Composite by In Site Reduction and Matrix Alloying with Titanium

To reduce the agglomeration of graphene and enhance the interface bonding between reduced graphene oxide (RGO) and copper substrate, copper plating on the graphene surface was prepared by the in-situ reduction method. To improve the strength of the copper matrix, the microalloying strategy of adding titanium to the matrix was adopted. By changing the mass fraction of titanium in the matrix, the optimum ratio of RGO was obtained( Ti mass fraction was 5:1), and the tensile strength was maximized. The results show that RGO did not agglomerate obviously in the matrix. At the same time, the composite powder could be densified rapidly by spark plasma sintering (SPS), which could effectively protect the original distribution of the additive phase in the matrix. In this paper, Cu@RGO/Cu-Ti was prepared and the strengthening mechanism of the composites discussed, providing a new insights into the interface design and carbide formation mechanism of advanced graphene/copper composites with high mechanical properties.

Improving the Return Loading Rate Problem in Northwest China Based on the Theory of Constraints

This paper introduces how to improve the return loading rate problem by integrating the Sub-Tour reversal approach with the method of the Theory of Constraints (TOC). The proposed model generates the initial solution derived by the Sub-Tour reversal approach in phase 1 and then applies TOC to obtain the optimal solution, meeting the goal of improving the return loading rate to more than 50% and then lowering the total transportation distance in phase 2. To see our model capability, this study establishes an original distribution layout to compare the performance of the Sub-Tour reversal approach with our model, based on the simulation data generated by the Monte Carlo simulation. We also conduct the pair t-test to verify our model performance. The results show that our proposed model outperforms the Sub-Tour reversal approach in a significant manner. By utilizing the available data, our model can be easily implemented in the real world and efficiently seeks the optimal solutions.

Vegetation diversity and structure of urban parks in Cilegon City, Indonesia, and local residents’ perception of its function

Muhlisin, Iskandar J, Gunawan B, Cahyandito MF. 2021. Vegetation diversity and structure of urban parks in Cilegon City, Indonesia, and local residents’ perception of its function. Biodiversitas 22: 2589-2603. The existence of urban parks is very essential for cities because they provide ecosystem services and benefits to humans. Diversity and structure of vegetation in urban parks play significant role in delivering several functions of ecosystem services. This paper aims to explore and analyze the vegetation diversity and structure, as well as ecosystem services of eight urban parks in Cilegon City, Banten Province, Indonesia. Vegetation analysis and residents’ perception are also conducted in this research. The analysis of vegetation is focused on horizontal structure of vegetation, including plant diversity, plant habitus, the original distribution of the plants, and vertical structure of vegetation (canopy stratification and vegetation profile). The residents’ perceptions are collected using interviews of selected respondents. The identification of vegetation recorded 114 plant species from 46 families are found in the concerned urban parks, however, the diversity and species richness in these parks tended to be low. The vegetation communities are uncertain and dominated primarily by non-native and invasive species. The canopy stratification is relatively homogeneous with the dominant plants having less than one meter in height, such as Ruellia simplex and Syzygium paniculatum. The vegetation planted in the urban parks are mostly ornamental plants that provide much more aesthetic function rather than ecological purpose, daily human needs, or other ecosystem services. This fact shows that urban parks in the study area have only few ecosystem services, hence they need some improvements in order to have more environmental services and to be able to enjoy more by the community.