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The charge simulation technique (CST) was applied for computing the electric field in long space-charge-free rod-to-plane gaps with $G$ (=gap-spacing to rod-radius) ratio in the range of 50–500. In this article, a new formation of CST is proposed for computing the electric field in short positively stressed rod-to-plane gaps characterized by $G$ in the range of 2–160 and gap spacing up to 8 cm, provided that the gap can accommodate space charges. This is a prerequisite for computing the inception voltage of different corona modes, including burst pulses (BP), onset streamers (OS), and positive glow (PG). The criteria developed before for computing the inception voltage of BP and OS are refined for short rod-to-plane gaps. However, the inception criterion for PG cannot be extended to short gaps. A method is proposed for calculating the inception voltage of PG in short rod-to-plane gaps in the air at room temperature. The initiatory electrons for burst avalanches are produced by photoionization inside the ionization zone rather than by detachment of negative ions as experienced in long gaps. The resulting BP merges in time to form the steady glow at the rod surface in conformity with Loeb’s postulate. The computed inception voltage of BP, OS, and PG agreed reasonably with those measured experimentally for short rod-to-plane gaps.

A new method based on the charge simulation technique is proposed for computing the electric field in a short uniform field gap with space charge and without space charge of avalanches growing in the gap. The self-space-charge field of the avalanche is evaluated to result in field enhancement ahead of the avalanche due to electrons at its head and behind the avalanche due to positive ions in its wake. Also, a criterion is proposed for calculating the breakdown voltage and time-to-breakdown when the primary avalanche crosses the gap. The criterion is based on self-recurrence of the avalanche by secondary processes, and the most dominant one is the photoemission at the cathode. The condition of transition of the primary avalanche to anode- and cathode-directed streamers is formulated where the avalanche is chocked by its self-space-charge field. The number of electrons starting avalanche chains forming the streamers is evaluated in the gas ahead and behind the primary avalanche by photoionization and at the cathode by photoemitted electrons. The present computed values of the breakdown voltage of air at different pressures and N2 at atmospheric pressure as well as the time-to-breakdown in air at atmospheric pressure agree satisfactory with those recorded experimentally. The computed temporal variation of the size of the primary avalanche as influenced by its self-space-charge field agrees with that reported in the literature at different $E/N$ values. The computed current waveforms of the primary avalanche and its successor chains agree reasonably with those measured and those calculated using a finite-element method.

The strain developed around implants with angled abutments should be considered when selecting a superstructure material. Studies that evaluated the strain developed around implants with angled abutments when using fiber-reinforced polymer as the implant superstructure material are lacking.The purpose of this in vitro study was to assess the strain developed around implants with angled abutments (15 and 25 degrees) of biocompatible high-performance polymer (BioHPP) and reinforced nanohybrid polymer with a multilayered glass fiber (TRINIA) superstructure under axial and oblique loading. The strain developed around implants was evaluated by using strain gauges.Thirty-two polyurethane test blocks were divided into 2 main groups (n=16) according to the degrees of buccal tilting of the implant platform (15 and 25 degrees). Each group was divided into 2 subgroups (n=8), and each subgroup received different superstructure materials (BioHPP or TRINIA). Two buccal and palatal strain gauges were installed on their corresponding prepared sites to measure the microstrains in the medium surrounding the implant. A universal testing machine was used to apply the static load from 0 to 100 N in the axial and 45-degree oblique direction, with the loading tip of the device on the loading point at the central fossa of the crown. For each tested implant, loads were applied, microstrains were recorded with the strain gauges, and the strain developed around the implant was statistically evaluated with 1-way ANOVA, followed by multiple pairwise comparisons by using the Bonferroni adjusted significance level (α=.05).For superstructure materials, the microstrain values recorded around implants restored with TRINIA were significantly lower than those restored with BioHPP in all groups (P.001). The 25-degree implant angulation recorded significantly higher microstrain than 15 degrees buccally and palatally when axial and oblique loads were applied (P.05). The microstrain was significantly higher in the oblique load than in the axial load in both the BioHPP and TRINIA groups in 15- and 25-degree implant angulations on the buccal and palatal sides (P.001).The strain developed around dental implants was significantly affected by the superstructure material. The microstrain was considerably higher when the implant abutment angulation increased. When a 45-degree loading direction was used, this tendency became more pronounced.

This work studies, theoretically, the thallium-based quantum dot photodetectors. The structures studied are $$In_{.93} Tl_{.07} Sb$$, $$In_{.33} Tl_{.67} P$$, $$In_{.85} Tl_{.15} As/GaAs$$, and $$In_{0.8} Tl_{0.2} N$$. Some parameters of the structures, like band-edge discontinuity, are not determined, yet. Structure parameters, energy subbands, absorption, and quantum efficiency (QE) spectra are calculated. High QE was obtained with the first structure which can be tuned at the required wavelength. High QE is obtained for the structures $$In_{.93} Tl_{.07} Sb$$ and $$In_{.33} Tl_{.67} P$$ when the junction depth is comparable to or less than the hole diffusion length $$(L_{p} )$$, while for the other two structures ($$In_{.85} Tl_{.15} As$$ and $$In_{0.8} Tl_{0.2} N$$) the junction depth must be larger than the hole diffusion length. The proposed photodetectors are covering the infrared range 3000–12000 nm which have an important applications.

In Mobile Social Networks (MSNs), people contact each other through mobile devices, such as smartphones and tablets, while they move freely. The communication takes place on-the-fly by the opportunistic contacts between mobile users via local wireless bandwidth, such as Bluetooth or WiFi without a network infrastructure. Social Multicast is an important routing service in MSNs where data transmission is addressed to a group of users according to their social features. The aim of this paper is to find and recommend mobile nodes that can efficiently relay and consume messages based on their social features. Efficiency in this context is to achieve high delivery ratio while reducing considering resources constraints and limitations such as power and space. The proposed algorithm, TESS, measures social similarity based on Time-based Encounter of Socially Similar nodes. We compare the proposed algorithm with the known social multicast algorithms: Multi-CSDO, EncoCent and Epidemic. Simulations results show that the proposed algorithm outperforms others in terms of delivery ratio and network overhead.

Connecting mobile computing devices, such as smartphones and tablets, anytime and anywhere has been the target of mobile networks in recent decades. Nowadays, this concept is extended to connecting selected people, which requires knowing the social profile of the device users, and therefore created the Mobile Social Network (MSN).Multicast routing in MSNs is concerned with finding and selecting people to deliver a message. Traditional multicast routing protocols do not consider the users’ profile. Recently, some social multicast protocols have emerged. These protocols consider the social behavior and relationships of the users to decide which nodes can act as relays and which ones can be considered destinations.The aim of this paper is to experimentally compare and analyze the performance of three known protocols in MSNs. The performance measures used are: delivery ratio, relay count, overhead ratio, hop count and dropped packets. The experiments are run with different network sizes, variable buffer capacities and packets Time-To-Live (TTL). The paper is concluded with a summarized analysis of the compared protocols.

This paper is aimed at calculating the onset voltage of a sliding discharge established between two electrodes at the upper and bottom surfaces of a dielectric barrier plate; named sliding dielectric barrier discharge (SDBD) driven by AC voltage during negative half cycle. The onset voltage is based on the condition of self-sustenance of avalanche growth in the vicinity of the stressed electrode. This calls at first for calculation of the electric field in the vicinity of stressed electrode. The dependency of onset voltage on the thickness and permittivity of the dielectric barrier as well as the thickness of the stressed electrode and the inter-electrode spacing between the stressed and ground electrodes is investigated. The obtained results are discussed in the light of gas discharge physics.