The solid structure of the crystalline 1:1 complexes of 18-crown-6 (1,4,7,10,13,16-hexaoxacyclo-octadecane) with 4-ethoxyanilinium perchlorate [1] has been determined at 298 and 93 K, respectively. The measurements of the unit cell parameters versus temperature show that the values of a axis and crystal volume change abruptly and remarkably at ∼163 K, indicating that this phase character may be a first-order. The crystal structural analysis of both two temperatures shows that in addition to van der Waals' forces, conventional N-H 3 3 3 O, C-H 3 3 3 O hydrogen bonds, and C-H 3 3 3 π interaction are the main molecular interactions. The most distinct differences between the structures in room-temperature phase and low-temperature phase are of the twist of molecules viewing along a-axis. DSC measurements further confirm that this inclusion compound undergoes a reversible structural phase transition at about 163 K with a thermal hysteresis of 3.6 K in which relatively large latent heat (H) makes 1 a good candidate for PCMs (phase change materials). As usual, the physical properties, such as dielectric constant and specific heat (C p ), will change a lot near phase transition temperature (T c ). No distinct dielectric constant anomaly was observed in frequency and temperature ranges of 10-1000 kHz and 100-298 K.

One novel organic-inorganic hybrid compound, (p-CH 3 -OC 6 H 4 NH 3 ) + (18-crown-6)·H 2 PO 4 -·2H 3 PO 4 (1) ((p-CH 3 OC 6 H 4 NH 3 ) + = 4-methoxyphenylammonium; 18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), has been synthesized and characterized by IR spectroscopy, thermogravimetric analysis and single crystal X-ray diffraction. In the structure, the organic (p-CH 3 OC 6 H 4 NH 3 ) + (18-crown-6) supermolecular cation layer and inorganic phosphate anion layer arrange

Light-emitting diode (LED) access point (AP) scheduling can provide both significant performance gains and flexible user access for visible light communications. However, the scheduling for multiple moving users, which requires adaptive LED AP scheduling for user movements and is practical in common scenarios, has so far rarely been studied. An incremental scheduling scheme is proposed to introduce a time division scheduling framework to solve the scheduling problem with multiple moving users. The proposed scheme consists of two phases: global scheduling and local scheduling. In the global scheduling phase, a scheduling scheme based on graph theory is proposed to assign users to different timeslots to eliminate inter-user interference. In the local scheduling phase, the result of global scheduling is adjusted for user movements. Simulation results show that the proposed scheme improves system capacity with reduced complexity.Introduction: Visible light communication (VLC) is a short-range wireless transmission of visible light through free space. In a VLC system, the light-emitting diode (LED) is not only used as a lighting device, but also as a communication device [1]. Compared with conventional short-range wireless communications, VLC can guarantee better security, support ubiquitous infrastructure and improve power efficiency and data rate [2]. One of the major concerns that arise with VLC is LED access point (AP) scheduling for a VLC system with multiple users. LED AP scheduling is to realise multiple user access and efficient resource allocation by managing the communication of LED APs of a VLC system. An LED association scheme was proposed in [3] for throughput enhancement by adjusting the transmission beam. However, beam adjustment is unusual for an LED to guarantee the illumination. In [4], a bandwidth-based scheme was proposed to realise flexible user access, but the scheme considers a static scheduling scenario and user mobility is not taken into consideration.In this Letter, we propose an incremental scheduling scheme (ISS) for a VLC system with multiple moving users. The proposed ISS introduces a time division scheduling framework and it can be divided into two phases. In the first phase, global scheduling based on graph theory is proposed to assign users to different timeslots where users can be served by available LED APs without interference. In the second phase, a local scheduling scheme is presented to adjust the LED APs allocation result according to the user movements by backtracking. To the best of our knowledge, this is the first exploration that introduces a scheduling framework for VLC with user mobility.

In the crystal of the title mol­ecular salt, C7H8NO+·ClO4 −, the ions are linked by N—H⋯O hydrogen bonds, resulting in chains propagating in [010]. The packing is reinforced by C—H⋯O inter­actions.

Abstract.A new phase transition compound 4-ethoxybenzenammonium iodide (1)