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Copyright of Environmental & Social Management Journal / Revista de Gestão Social e Ambiental is the property of Environmental & Social Management Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The primary objective of this paper is to conduct a comparative analysis of diverse Electromagnetic Band Gap (EBG) antennas in terms of their suitability for Wi-Fi applications operating at 5 GHz. Wi-Fi primarily operates within the 2.4 GHz and 5 GHz frequency bands, with the 5 GHz band offering higher data rates and reduced interference compared to the 2.4 GHz band. Furthermore, its larger number of available channels makes it an optimal choice for environments with high user density. The antennas in this study are designed with dimensions of 28.11x32.40x1.6 mm³ (length x width x height) using RT/Duroid 5880 substrate, which has a thickness of 1.6 mm and a relative permittivity (εr) of 2.2. The integration of Electromagnetic Band Gap structures in antenna designs has gained substantial attention due to their unique properties that enhance antenna performance characteristics. The paper presents sixteen distinct EBG antennas, all designed using CST software. These antennas incorporate various EBG shapes, such as Fork, L-shape, C-shape, Hash, and Z-shape, positioned on a rectangular patch and in the ground plane. The study's results reveal that the Hash EBG on the patch offers superior performance compared to other EBG types. As a result, the Hash EBG on the patch, alongside various Z-shaped EBGs on the ground plane, is assessed for different antenna performance parameters, including return loss, radiation patterns, and gain. Finally, a diagonal Z-shaped EBG antenna is designed, simulated, and tested. The antenna return loss at 5.2GHz is -48 dB The proposed antenna achieved a peak gain of 7.3 dB at 5.2GHz. The proposed antenna exhibits omnidirectional properties. The antenna shows an efficiency of 90% at the resonant frequency. The experimentally measured results of the designed diagonal EBG antenna have shown satisfactory agreement and are consistent with the simulated results. The findings of this research contribute to a better understanding of EBG antennas potential for Wi-Fi applications in the 5 GHz frequency band.

In a blockchain network, a rule set called consensus mechanism is used to create and finalize a block. In a proof-of-stake (PoS), consensus-based blockchain network, nodes become validators, minters, or stakeholders' nodes to complete the consensus mechanism. In these networks, when a node becomes a validator node, its details need to be saved because the details of the validators are used in the network for many important decisions, such as selecting block proposers for the consensus process. In this paper, we present Sea Shield, which uses a validator chain to save a node's information when it becomes a validator or leaves its responsibility as a validator in the PoS-based blockchain network. The validator chain is a blockchain that can run with the main chain of a PoS-based blockchain. The internal features of the validator chain are similar to those of the blockchain. We designed and simulated a consensus mechanism to create and finalize the block for the validator chain with no forks. We present a process by which a node may join or unjoin as a validator in a PoS-based blockchain network to improve the overall security of the main chain-consensus process. [ABSTRACT FROM AUTHOR]

Estimating the applied power during a stabbing incident, or estimating the minimal force necessary to penetrate the body with a certain weapon is a challenging task in forensic practice. A thorough forensic evaluation of stabbing forces needs objective numerical experimental data. Stabbing tests of 12 different weapons – including knives, a pair of scissors, a fork, screwdrivers, a rasp, a corkscrew, and a utility knife blade – were performed with a Mecmesin MultiTest‐dV material tester on pork loin and ballistic gel to estimate the stabbing forces and dynamics. Penetration force (Fp) and maximal force (Fmax) were recorded, and the registered force curves were analyzed. Fmax was 159.8–212.07 Newton (N), 30.56–30.58 N, 168.9–185.48 N for various knives; 171.39–190.43 N for the pair of scissors, 233.6 N for the fork; 532.65–562.65 N, 370.31–367.19 N and 314.51–432.89 N for various screwdrivers, 44.14–56.62 N for utility knife during pork loin stabbing. The butter knife, corkscrew and rasp were not able to penetrate the pork loin, and the curved fork bent during stabbing. The results prove that weapon characteristics greatly influence the force necessary for penetration. Maximal stabbing force depends mostly on tip sharpness, and the force sharply decreases after penetration occurs, which indicates that edge sharpness is not as important as tip characteristics during stabbing perpendicular to skin surface. The penetration force during stabbing with a pair of scissors is comparable to the penetration force of knives. Stabbing with screwdrivers generally needs larger force than average knives but depends greatly on screwdriver size. [ABSTRACT FROM AUTHOR]

Keloids are benign dermal tumors that arise from abnormal wound healing processes following skin lesions. Surgical excision followed by radiotherapy plays an important role in the treatment of keloids. Nevertheless, radioresistance remains a serious impediment to treatment efficacy. Investigation of the molecular response of keloids to radiation may contribute to radiosensitizing strategies. Primary keloid fibroblasts from human keloids were isolated and irradiated with X-ray. The expression profiles of messenger RNA (mRNA) in nonradiated and irradiated primary keloid fibroblasts were measured by mRNA sequencing analysis. Then, we identified common motifs and corresponding transcription factors of dysregulated mRNAs by using bioinformatic analysis of the proximal promoters. Whereafter, GO and KEGG were used to analyze the functional enrichment of the differentially expressed genes. We found that radiation not only suppressed proliferation but also increased cell senescence of primary keloid fibroblasts. There were 184 mRNAs and 204 mRNAs that showed significant changes in 4 and 8 Gy irradiated primary keloid fibroblasts, respectively. Among them, 8 upregulated and 30 downregulated mRNAs showed consistent alterations in 4 and 8 Gy irradiated primary keloid fibroblasts. More importantly, the xForkhead box O1 (FOXO1) signaling pathway was involved in the irradiation response. Pretreatment with the FOXO1 signaling inhibitor AS1842856 significantly promoted LDH release, apoptosis and senescence of primary keloid fibroblasts following irradiation. Our findings illustrated the molecular changes in human keloid fibroblasts in response to radiation, and FOXO1 pathway inhibition is expected to provide a novel strategy for the radiosensitization of keloids. [ABSTRACT FROM AUTHOR]

Let G = (V, E) be a graph. Fork is a tree obtained by subdividing any edge of a star of size three exactly once. In this paper, we investigate the necessary and sufficient condition for the fork-decomposition of Cartesian product of graphs. [ABSTRACT FROM AUTHOR]

In a blockchain network, a rule set called consensus mechanism is used to create and finalize a block. In a proof-of-stake (PoS), consensus-based blockchain network, nodes become validators, minters, or stakeholders’ nodes to complete the consensus mechanism. In these networks, when a node becomes a validator node, its details need to be saved because the details of the validators are used in the network for many important decisions, such as selecting block proposers for the consensus process. In this paper, we present Sea Shield, which uses a validator chain to save a node’s information when it becomes a validator or leaves its responsibility as a validator in the PoS-based blockchain network. The validator chain is a blockchain that can run with the main chain of a PoS-based blockchain. The internal features of the validator chain are similar to those of the blockchain. We designed and simulated a consensus mechanism to create and finalize the block for the validator chain with no forks. We present a process by which a node may join or unjoin as a validator in a PoS-based blockchain network to improve the overall security of the main chain-consensus process.

Sensory professionals are looking for alternative ways to conduct laboratory sensory testing, especially central location testing (CLT), during the COVID-19 pandemic. One way could be conducting CLTs at home (i.e., in-home testing). It is questionable whether food samples under in-home testing should be presented in uniform utensils, as it does so under laboratory sensory testing. This study aimed to determine whether utensil conditions could affect consumer perception and acceptance of food samples evaluated under in-home testing. Sixty-eight participants (40 females and 28 males) prepared chicken-flavored ramen noodle samples and evaluated them for attribute perception and acceptance, under two utensil conditions, using either their utensils ("Personal") or uniform utensils provided ("Uniform"). Participants also rated their liking of forks/spoons, bowls, and eating environments, respectively, and attentiveness to sensory evaluation under each utensil condition. Results of the in-home testing showed that participants liked ramen noodle samples and their flavors under the "Personal" condition significantly more than under the "Uniform" condition. Ramen noodle samples evaluated under the "Uniform" condition were significantly higher in terms of saltiness than those evaluated under the "Personal" condition. Participants liked forks/spoons, bowls, and eating environments used under the "Personal" condition significantly more than those used under the "Uniform" condition. While overall likings of ramen noodle samples, evaluated under the "Personal" condition, significantly increased with an increase in hedonic ratings of forks/spoons or bowls, such significant correlations were not observed under the "Uniform" condition. In other words, providing uniform utensils (forks, spoons, and bowls) to participants in the in-home testing can reduce the influences of utensils on consumer likings of ramen noodle samples evaluated at home. In conclusion, this study suggests that sensory professionals should consider providing uniform utensils when they want to focus solely on consumer perception and acceptance of food samples by minimizing influences of environmental contexts, especially utensils, in the "in-home" testing. [ABSTRACT FROM AUTHOR]

Let G = (V,E) be a graph. Fork is a tree obtained by subdividing any edge of a star of size three exactly once. In this paper, we investigate a necessary and sufficient condition for the existence of fork-decomposition of some total graphs. [ABSTRACT FROM AUTHOR]

A h o l e is an induced cycle of length at least four, and an odd hole is a hole of odd length. A fork is a graph obtained from K 1 , 3 by subdividing an edge once. An odd balloon is a graph obtained from an odd hole by identifying respectively two consecutive vertices with two leaves of K 1 , 3. A gem is a graph that consists of a P 4 plus a vertex adjacent to all vertices of the P 4. A butterfly is a graph obtained from two triangles by sharing exactly one vertex. A graph G is perfectly divisible if for each induced subgraph H of G , V (H) can be partitioned into A and B such that H [ A ] is perfect and ω (H [ B ]) < ω (H). In this paper, we show that (fork, odd balloon)-free graphs are perfectly divisible (this generalizes some results of Karthick et al. [11]). As an application, we show that χ (G) ≤ ( ω (G) + 1 2 ) if G is (fork, gem)-free or (fork, butterfly)-free. [ABSTRACT FROM AUTHOR]

One of the features of the Bitcoin network today is that its participating nodes are located in different regions of the world. Generally, inter-region data transmission is relatively time-consuming compared with intra-region data transmission. Thus, an important challenge for a blockchain network is shortening the block propagation time in order to reduce forks and maintain fairness, i.e., similar mining durations, for all miners. Previous methods have tried to increase the block propagation speed at the expense of imposing a higher burden on each node and a higher risk of eclipse attack. This paper proposes a new neighbor selection method that is based on only the neighbor’s regional information and assumes that a node has a relatively small number of neighbors located outside its region. By using this simple method, the distribution of blocks throughout the network becomes faster and the random neighbor-selection nature of the blockchain network is kept intact; thus, risk of an eclipse attack is low. This paper also proposes a block propagation model over multiple regions for exploring the theoretical reasons for the effectiveness of the proposed neighbor selection method. Finally, it examines a migration scenario to the proposed method from the default neighbor selection method implemented in Bitcoin nodes, and evaluates the migration effects in various sizes of networks.

We explored mined block temporarily holding (MBTH), MBTH with enforce fork (MBTH-EF), and intermittent MBTH-EF (iMBTH-EF) attacks to understand the effect of selfish mining on winning rate and fairness from the pool operation perspective. The temporary holding time of the current mined block provides a pool additional time to begin mining the next block early with MBTH attack. In this situation, the winning probability increases for the next block, but the pool may risk losing the mined block. One enhanced method to maintain the winning probability of the held block is to ensure the holding pool sends out the mined block once it receives the mined block message from the other pools with the MBTH-EF attack. The explored MBTH attacks differ from the existing selfish miner and pool attacks. The operations and effects of the MBTH-EF attack are different from stubborn mining strategies and a self-holding attack integrates selfish and stubborn mining attacks. We propose a mining competition solution that does not involve actual hash calculation. It entails using one stochastic target hash value for batch racing simulation to evaluate the holding threshold, holding periods, mining time, mining difficulty, pool sizes, and the rate of fork occurrences according to the operation data of the Bitcoin system. Accordingly, the dynamic time-by-time, block-by-block, and pool-by-pool simulations are adopted to study these attacks. We analyzed MBTH and MBTH-EF attacks as well as evaluated the effects of the win rate on when and how long a block is held. Because the periodic adjustment of mining difficulty reduces the holding effect, we further evaluated how an intermittent MBTH-EF (iMBTH-EF) attack model balance the average mining time and mining difficulty according to the mining difficulty adjustment of a stage. The effect of intermittent holding is examined on the mining game win rate for a long-term competition. We also identified suitable attack detection methods for the future work according to the simulation results.

Bitcoin is the first fully decentralized cryptocurrency. The security features of Bitcoin rely on blockchain technology, which comprises each current as well as the past transactions in the system. In a blockchain when more than one block extends from the same preceding block, the situation is termed as fork or Block race. A selfish miner abuses Bit coin's forks method to gain several unfair rewards. To tackle the issues caused by selfish mining, this work proposes a novel scheme called "Towards the Rear Attuned Defense Scheme". Accordingly, to identify the presence of selfish miners, the Newfangled selfish mining revelation algorithm with a Fork Tenacity Strategy is used here. A weighted fork with a secured fail parameter is established here to compete with the block race caused by the selfish miner. Finally, to ensure reliability, a Slice-up Tender mint consensus protocol is used. Thus, our proposed scheme ensures a better defense against the selfish mining attacks and achieves better time convergence with less electricity fee. [ABSTRACT FROM AUTHOR]

Proof of work (PoW) is a popular consensus mechanism for blockchain. However, it, consuming huge computing resources, does not serve useful purpose beyond reaching a consensus. Recently, proof of useful work (PoUW) has been proposed to overcome the drawback of PoW. With PoUW, each miner spends almost all the time in doing useful work (e.g., data classification), and then competes for the winner by the number of its consumed CPU instructions. Therefore, the time of doing useful work is a salient factor which is newly introduced to PoUW. In this paper, focusing on the new factor, we first model the fork probability of PoUW and then quantify its system throughput. Our model takes into account various design parameters (including the time of doing useful work) and produces a closed-form expression of the system throughput. We then run extensive simulations that verify the accuracy and effectiveness of our theoretical model. This study is very helpful for providing theoretically-guided parameter configurations for PoUW. [ABSTRACT FROM AUTHOR]

Long-years' archaeological excavations of Vlasta Fialová have brought a lot of metal finds but only a part of them can be evaluated. Non-ferrous metals resist the best to soil conditions (book fittings and fibulas, letters, printer's pins). Iron items have been preserved in a quite high number, the problem however is their fragmentary character, thus the limited possibility of their identification. A two tine fork with antler two-part handle with beaklike end stands out from such objects. It is an extraordinary item not only thanks to its good preservation condition. For an archaeological find from the turn of the 16th and 17th centuries, it is a very unusual object. The fork was the last part to join the dining cutlery. During the Middle Ages its two tine form was used only in the kitchen or for serving dishes and meat from a common plate. Its full usage is documented not only by iconographic sources and art historical collection items but now also by archaeological finds. [ABSTRACT FROM AUTHOR]

Sensory professionals are looking for alternative ways to conduct laboratory sensory testing, especially central location testing (CLT), during the COVID-19 pandemic. One way could be conducting CLTs at home (i.e., in-home testing). It is questionable whether food samples under in-home testing should be presented in uniform utensils, as it does so under laboratory sensory testing. This study aimed to determine whether utensil conditions could affect consumer perception and acceptance of food samples evaluated under in-home testing. Sixty-eight participants (40 females and 28 males) prepared chicken-flavored ramen noodle samples and evaluated them for attribute perception and acceptance, under two utensil conditions, using either their utensils (“Personal”) or uniform utensils provided (“Uniform”). Participants also rated their liking of forks/spoons, bowls, and eating environments, respectively, and attentiveness to sensory evaluation under each utensil condition. Results of the in-home testing showed that participants liked ramen noodle samples and their flavors under the “Personal” condition significantly more than under the “Uniform” condition. Ramen noodle samples evaluated under the “Uniform” condition were significantly higher in terms of saltiness than those evaluated under the “Personal” condition. Participants liked forks/spoons, bowls, and eating environments used under the “Personal” condition significantly more than those used under the “Uniform” condition. While overall likings of ramen noodle samples, evaluated under the “Personal” condition, significantly increased with an increase in hedonic ratings of forks/spoons or bowls, such significant correlations were not observed under the “Uniform” condition. In other words, providing uniform utensils (forks, spoons, and bowls) to participants in the in-home testing can reduce the influences of utensils on consumer likings of ramen noodle samples evaluated at home. In conclusion, this study suggests that sensory professionals should consider providing uniform utensils when they want to focus solely on consumer perception and acceptance of food samples by minimizing influences of environmental contexts, especially utensils, in the “in-home” testing.

Bitcoin is an innovative decentralized cryptocurrency that records transactions in a public log, termed the blockchain. Due to delays in the Bitcoin network, the Bitcoin blockchain has the potential for forming forks. In this paper, we consider a mining strategy in which the player who created the fork can attract other miners by posting rewards and the third party (other miners) has the ability to choose the fork based on their interests. We provide a model to formalize the considered case and analyze its feasibility. Based on certain game theoretical models, the best policies for two players, termed the creator of the fork and the third party, are presented. Finally, some cases of the considered model are simulated, and the average revenue of each player is compared with the theoretical revenue to verify the correctness of our strategy. When the delay varies from 0 to 400 milliseconds, adopting our strategy can acquire 23% more revenue than adopting the default strategy. The result shows that the default strategy of a miner is not always a good choice.

A super edge-magic total (SEMT) labeling of a graph ℘(V, E) is a one-one map ϒ from V(℘)∪E(℘) onto {1, 2,…,|V (℘)∪E(℘) |} such that ∃ a constant “a” satisfying ϒ(υ) + ϒ(υν) + ϒ(ν) = a, for each edge υν ∈E(℘), moreover all vertices must receive the smallest labels. The super edge-magic total (SEMT) strength, sm(℘), of a graph ℘ is the minimum of all magic constants a(ϒ), where the minimum runs over all the SEMT labelings of ℘. This minimum is defined only if the graph has at least one such SEMT labeling. Furthermore, the super edge-magic total (SEMT) deficiency for a graph ℘, signified as μs(℘)$\mu_{s}(\wp)$ is the least non-negative integer n so that ℘∪nK1 has a SEMT labeling or +∞ if such n does not exist. In this paper, we will formulate the results on SEMT labeling and deficiency of fork, H -tree and disjoint union of fork with star, bistar and path. Moreover, we will evaluate the SEMT strength for trees.

Copyright of Acta Musei Brukenthal is the property of Brukenthal National Museum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The paper, from the perspective of picturesque scene and space design, analyzes in detail the painting intention, spatial details and scenery of the fork of the northeast veranda of Bu Yuan, assisted by the narration of Yuan Ye written by Ji Cheng and Wen Zhengming's traditional Chinese landscape painting. And the paper analyzes how the garden seeks a balance between painting environment and gardening rules. [ABSTRACT FROM AUTHOR]

Let n be a positive integer, q a power of a prime, and ℒ n (q) the poset of subspaces of an n-dimensional vector space over a field with q elements. This poset is a normalized matching poset and the set of subspaces of dimension ⌊n/2⌋ or those of dimension ⌈n/2⌉ are the only maximum-sized antichains in this poset. Strengthening this well-known and celebrated result, we show that, except in the case of ℒ 3 (2) , these same collections of subspaces are the only maximum-sized families in ℒ n (q) that avoid both a ∧ and a ∨ as a subposet. We generalize some of the results to brooms and forks, and we also show that the union of the set of subspaces of dimension k and k + 1, for k = ⌊n/2⌋ or k = ⌈n/2⌉ − 1, are the only maximum-sized families in ℒ n (q) that avoid a butterfly (definitions below). [ABSTRACT FROM AUTHOR]

During the process of appropriating the spoon, children need to detect and acquire a series of functional motor skills, as well as certain social norms associated with the use of this tool. With this descriptive study we intend to obtain information on the temporal sequencing of access to the spoon and other cutlery, and what explorations the children make in the Portuguese family context. Data on 115 Portuguese toddlers were obtained through a structured online questionnaire. The results reveal that: i) there is a clear notion that the child needs an object scaled to the size of his/her hand; ii) the spoon favors the opportunity to physical, functional, solitary and social play; iii) explore spoon-use spoon-explore fork-explore knife is the temporal sequence of access to cutlery, significantly phased throughout the early childhood; iv) the toddler is able to explore the spoon as an instrument for functions other than those related to eating. Thus, the spoon has a very diverse potential for learning how to use an instrument, for exploring the functional properties of objects and for the social and cultural development of young children. [ABSTRACT FROM AUTHOR]

Two double-spend attack strategies on a proof-of-stake consensus are considered. For each strategy, the probability of its success is obtained, which depends on the network parameters and the number of confirmation blocks. These results can be used to define how many confirmation blocks a vendor should wait after a correspondent transaction before sending goods or services.

At present, the speed of production and its complexity increases with each passing year due to the shorter product life cycle and competition in the global market. This trend is also observed in the machine-building industry, therefore, in order to ensure the competitiveness of enterprises and reduce the cost of production, it is necessary to intensify production. This is especially true in the machining of complex parts that require a great number of setups, and technological equipment. The problem-oriented analysis of complex parts was carried out, the parts classification was structured and developed according to the design and technological features. This made it possible to offer advanced manufacturing processes for complex parts like levers, forks, and connecting rods. The flexible fixtures for specified complex parts were developed. The effectiveness of the proposed manufacturing processes, as compared with the typical ones, provides significant improvement in the production. [ABSTRACT FROM AUTHOR]

This research aims to extend the framework of the current studies in philosophy or sociology of technology, making an approach to a practice emerged in the communities and free software movement of last years, known as fork. A practice described initially as making a copy of the source code of software to be developed in other direction than the original code, but analyzed in detail suggests a wide range of issues concerning to the specific behavior of these communities.

In terms of software, “continuous development” of the software is the best quality assurance. Continuous development requires either the original developer to continue development, or the next generation of developers to take over the development. It has been noted that when the original developer has used “open source,” a development paradigm in which the source code is kept open to all, highly motivated and competent developers will participate in development. This makes it easier for a project to survive. However, at the same time, when the source code is opened to a broad audience a fork in the source code tends to occur. When this happens, those with a high level of competence and motivation abandon the development and go their separate ways. In such a situation, it is difficult for a project to survive. In the case of Denshin 8 go, a guardian for the source code was appointed, and the original developer and the guardians avoided this dilemma. Richard Stallman of the GNU project and Linus Torvalds of Linux project act as legitimate guardians to avoid fork.

In order to investigate the causes of the large number of cracks and porosities formed in 33MnCrTiB fork flat steel produced by a special steel plant, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) analysis, and large sample electrolysis of the obtained steel samples were carried out in different steps of the steelmaking processes. The main micro-inclusions in the fork flat steel samples were Al2O3, CaO-MgO-Al2O3-SiO2, and TiN, and the macro-inclusions were mainly Al2O3, CaO-Al2O3, CaO-Al2O3-SiO2-TiO2, and CaO-MgO-Al2O3-SiO2-TiO2-(K2O) systems which originated from the ladle slag and mold flux in the production process. In order to reduce the number of micro-inclusions effectively, the control range of components in the refining slag was confirmed by the thermodynamic calculation, where the mass ratio of CaO/Al2O3 should be in the range of 1.85⁻1.92, and the mass fraction of SiO2 and MgO should be controlled to 7.5⁻20% and 6⁻8%, respectively. In addition, the numbers of macro-inclusions in the flat steel should be effectively reduced by optimizing the flow field of mold and preventing the secondary oxidation, and the flat steel quality problems caused by the inclusions can be improved by the optimization process above.

In the investment casting of shifting fork, hot cracking is a common defect. In order to analyze the hot cracking in the investment casting, the ProCAST software was adopted, and the investment casting process was simulated, The filling field, temperature field and stress field were analyzed, and the cause of crack was predicted. Results show that as the local area receives larger tensile stress from around, the shrinkage cavity appears; as a result, hot cracking occurs. By decreasing the pouring temperature, increasing preheating temperature of the shell, or chamfer angle of the fork, the casting stress can be reduced, and thus the crack will be avoided. [ABSTRACT FROM AUTHOR]

Forking is the creation of a new software repository by copying another repository. Though forking is controversial in traditional open source software (OSS) community, it is encouraged and is a built-in feature in GitHub. Developers freely fork repositories, use codes as their own and make changes. A deep understanding of repository forking can provide important insights for OSS community and GitHub. In this paper, we explore why and how developers fork what from whom in GitHub. We collect a dataset containing 236,344 developers and 1,841,324 forks. We make surveys, and analyze programming languages and owners of forked repositories. Our main observations are: (1) Developers fork repositories to submit pull requests, fix bugs, add new features and keep copies etc. Developers find repositories to fork from various sources: search engines, external sites (e.g., Twitter, Reddit), social relationships, etc. More than 42 % of developers that we have surveyed agree that an automated recommendation tool is useful to help them pick repositories to fork, while more than 44.4 % of developers do not value a recommendation tool. Developers care about repository owners when they fork repositories. (2) A repository written in a developer's preferred programming language is more likely to be forked. (3) Developers mostly fork repositories from creators. In comparison with unattractive repository owners, attractive repository owners have higher percentage of organizations, more followers and earlier registration in GitHub. Our results show that forking is mainly used for making contributions of original repositories, and it is beneficial for OSS community. Moreover, our results show the value of recommendation and provide important insights for GitHub to recommend repositories. [ABSTRACT FROM AUTHOR]

Lenses and quasi-lenses on a space X form models of erratic non-determinism. When X is equipped with a quasi-metric d , there are natural quasi-metrics d P and d P a on the space of quasi-lenses on X , which resemble the Pompeiu-Hausdorff metric (and contain it as a subcase when d is a metric), and are tightly connected to the Kantorovich-Rubinstein quasi-metrics d KR and d KR a of Parts I, II and III, through an isomorphism between quasi-lenses and so-called discrete normalized forks. We show that the space of quasi-lenses on X is continuous complete, resp. algebraic complete, if X , d is itself continuous complete, resp. algebraic complete. In those cases, we also show that the d P -Scott and d P a -Scott topologies coincide with the Vietoris topology. We then prove similar results on spaces of (sub)normalized forks, not necessarily discrete; those are models of mixed erratic non-determinism and probabilistic choice. For that, we need the additional assumption that the cone L X of lower continuous maps from X to R ‾ + , with the Scott topology, has an almost open addition map (which is the case if X is locally compact and coherent, notably); we also need X to be compact in the case of normalized forks. The relevant quasi-metrics are simple extensions of the Kantorovich-Rubinstein quasi-metrics d KR a of Parts I, II and III. [ABSTRACT FROM AUTHOR]