Service Investment and Pricing Strategies in E-commerce Platforms with Sellers Competition

With the development of the two-sided market, many platform enterprises classify their users into different types and cooperate with them with different strategies. The extant literature mainly explores the pricing and investment decisions for the platform, but pays little attention to the classification of sellers when making decisions. This paper investigates the investment of value-added service and pricing strategies for an e-commerce platform with competing sellers. Specifically, this paper considers a two-sided platform that is composed of an e-commerce platform, buyers and sellers. Sellers with high performance requirement and with low performance requirement compete for the buyers in the platform. This paper assumes that each buyer will choose the sellers’ type immediately after entering the platform and buy a unit of product in the platform. Through theoretical analysis the authors show that, the platform will gain more profits by investing in value-added services for type-A sellers and it will obtain the optimal profit when the transaction fee is moderate.

Key performance requirement of future next wireless networks (6G)

Given the massive potentials of 5G communication networks and their foreseeable evolution, what should there be in 6G that is not in 5G or its long-term evolution? 6G communication networks are estimated to integrate the terrestrial, aerial, and maritime communications into a forceful network which would be faster, more reliable, and can support a massive number of devices with ultra-low latency requirements. This article presents a complete overview of potential 6G communication networks. The major contribution of this study is to present a broad overview of key performance indicators (KPIs) of 6G networks that cover the latest manufacturing progress in the environment of the principal areas of research application, and challenges.

Improved Verifier-Based Three-Party Password-Authenticated Key Exchange Protocol from Ideal Lattices

With the advent of large-scale social networks, two communication users need to generate session keys with the help of a remote server to communicate securely. In the existing three-party authenticated key exchange (3PAKE) protocols, users’ passwords need to be stored on the server; it cannot resist the server disclosure attack. To solve this security problem, we propose a more efficient 3PAKE protocol based on the verification element by adopting a public-key cryptosystem and approximate smooth projection hash (ASPH) function on an ideal lattice. Using the structure of separating authentication from the server, the user can negotiate the session key only after two rounds of communication. The analysis results show that it can improve the efficiency of computation and communication and resist the server disclosure attack, quantum algorithm attack, and replay attack; moreover, it has session key privacy to the server. This protocol can meet the performance requirement of the current communication network.

Cost-Efficient LEO Navigation Augmentation Constellation Design under a Constrained Deployment Approach

The advantages of the Low Earth Orbit (LEO) satellite include low-latency communications, shorter positioning time, higher positioning accuracy, and lower launching, building, and maintenance costs. Thus, the introduction of LEO satellite constellation as a regional navigation augmentation system for the current navigation constellations is studied in this paper. To achieve the navigation performance requirement with the least system cost, a synthetic approach is presented to design and deploy a cost-efficient LEO navigation augmentation constellation over 108 key cities. To achieve lower construction costs, the constellation is designed to be deployed by constrained piggyback launches, which brings additional complexity to the constellation design. Two optimization models with discrete and continuous performance indices are established. They are solved by the genetic algorithm and differential evolution algorithm, and both Walker and Flower constellations are adopted. Results for 77 and 70 satellites are obtained. During the construction phase, a synthesis procedure containing five impulses is proposed by utilizing natural drift under J 2 perturbation. This work presents a method for designing the optimal LEO navigation constellation under a constraint deployment approach with the lowest construction cost and a strategy to deploy the constellation economically.

A case study in the measurement of door sound isolation with ASTM test standards

The use of the door transmission class rating in lieu of the apparent sound transmission class rating has yet to gain traction within building codes and specified project requirements. This paper presents a case study involving performance requirement testing conducted at a university's media facility, in which sound insulation properties were a critical design and construction focus. Both test methods described in ASTM E2964 and ASTM E336 were performed where a door was the test partition. Door transmission class ratings were presented in comparison to apparent sound transmission class ratings for the same partition. Testing was performed in a variety of situations, including scenarios both inside and outside of the minimum requirements of testing standards. Our analysis considers the effectiveness of the recently adopted ASTM E2964 in comparison to the methods of the ASTM E336. We also consider some of the subtle differences between the two test methods and how they may impact the testing of certain adjacencies.

Ballistic Performance Evaluation of Kevlar-Glass Fibre Hybrid Composite Laminate against Medium Velocity Impact

In this paper, the post ballistic impact behaviour of kevlar-glass fibre hybrid composite laminates was investigated against 9×19 mm projectile. Eight different types of composite laminates with different ratios of kevlar woven fibre to glass fibre were fabricated using hand lay-up with epoxy matrix. Ballistic behaviour like ballistic Limit (V50), energy absorption, specific energy absorption and Back Face Signature (BFS) were studied after bullet impact. The results indicated that as the Percentage of glass fibre is increased there was a linear increment in the ballistic behaviour. Addition of 16% kevlar fabric, composite sample meets the performance requirement of NIJ0101.06 Level III-A. Since the maximum specific energy absorption was observed in Pure Kevlar samples and the adding of glass fibre increases the weight and Areal Density of the sample, further investigations need to be carried out to utilize the potential of glass fibre for ballistic applications.

Experimental Study on Two-Hour Fire Resistance Performance of Slabs in Modular Buildings under Loads

For a floor of a building with no less than four stories and no more than twelve stories, the two-hour fire resistance performance should be satisfied. In the case of slabs with steel studs, no two-hour fire resistance performance has been proposed in Korea. In this study, the two-hour fire resistance performance of slabs with steel studs performing as structural elements of modular buildings was evaluated. These specimens were redesigned based on the typical slab used in Europe and North America by modifying the 45 mm fire-resistant board to achieve two-hour fire resistance. The experimental results showed that the FR-001 specimens with 140 mm mineral wool applied to the lower slab and the FR-002 specimens containing 100 mm lower-slab glass wool and 150 mm upper-slab mineral wool did not satisfy the two-hour fire resistance performance, owing to the rapid deformation of the specimens after 75 and 110 min, respectively. However, the FR-003 specimens containing 100 mm glass wool, 150 mm mineral wool in the upper slab, and concrete in the slab satisfied the two-hour fire resistance performance requirement.

Research on Satellite Selection Strategy for Receiver Autonomous Integrity Monitoring Applications

Satellite selection is an effective way to overcome the challenges for the processing capability and channel limitation of the receivers due to superabundant satellites in view. The satellite selection strategies have been widely investigated to construct the subset with high accuracy but deserve further studies when applied to safety-critical applications such as the receiver autonomous integrity monitoring (RAIM) technique. In this study, the impacts of subset size on the accuracy and integrity of the subset and computation load are analyzed at first to confirm the importance of the satellite selection strategy for the RAIM process. Then the integrated performance impact of a single satellite on the current subset is evaluated according to the performance requirement of the flight phase. Subsequently, a performance-requirement-driven fast satellite selection algorithm is proposed based on the impact evaluation to construct a relatively small subset that satisfies the accuracy and integrity requirements. Comparison simulations show that the proposed algorithm can keep similar accuracy and better integrity performances than the geometric algorithm and the downdate algorithm when the subset size is fixed to 12, and can achieve an average 1.0 to 2.0 satellites smaller subset in the Lateral Navigation (LNAV) and approach procedures with vertical guidance (APV-I) horizontal requirement trial. Thus, it is suitable for real-time RAIM applications and low-cost navigation devices.

Aircraft Flight Stabilizer System by CDM Designed Servo State-Feedback Controller

This research presents an automatic flight control system whose advantage is its ease of modification or maintenance while still effectively meeting the system’s performance requirement. This research proposes a mixed servo state-feedback system for controlling aircraft longitudinal and lateral-directional motion simultaneously based on the coefficient diagram method or CDM as the controller design methodology. The structure of this mixed servo state-feedback system is intuitive and straightforward, while CDM’s design processes are clear. Simulation results with aircraft linear and nonlinear models exhibit excellent performance in stabilizing and tracking the reference commands for both longitudinal and lateral-directional motion.