ABSTRACT
The polarization modulation of deep-UV light is an important process that incorporates functionality to selectively respond to light-mater interaction. Typically, optical anisotropy is foremost to the use efficiency of deep-UV birefringent crystals. Herein, a new congruently melting polyborate with extremely large birefringence (Δn(001) =0.14@589.3â nm) and band gap (6.89â eV) is discovered as a high performance birefringent crystal, which breaks the current deadlock of deep-UV polyborates that usually show small birefringence. The rigid tetrahedra, including [ZnO4 ] and edge-sharing [BO4 ] tetrahedra, make all the planar [BO3 ] triangles in the lattice adopt preferential arrangement and thereby lead to an extraordinary large birefringence that is larger than all the deep-UV borates with experimentally measured values. Structural analyses with the additional theoretical calculations were used to study the origin of strong optical anisotropy in BaZnB4 O8 .
ABSTRACT
Thermal comfort is an important indicator for evaluating the environment of urban public space, and appropriate thermal comfort can effectively prolong the duration of outdoor activities. In the existing studies, there is a lack of thermal comfort comparison between hot spots and cold spots. In this study, we selected the coastal city of Dalian in China as our study area and conducted field investigations on the thermal comfort of two landmark resorts, namely, a downtown commercial street and coastal leisure park. The study was conducted on typical summer days and consisted of interviewing several residents to understand their thermal comfort requirements. We investigated the thermal expectations of the interviewees through meteorological measurements and questionnaires. The universal thermal climate index (UTCI) was used to determine the thermal benchmarks of the on-site subjects. The results indicated that (1) globe temperature and air temperature were the most important factors that affected thermal comfort, followed by relative humidity and wind speed in summer daytime. (2) Shaded spaces are more comfortable than open spaces, and tree shade is preferred over artificial shade in coastal park. (3) The neutral UTCI (NUTCI) of the respondents were 24.1°C (coastal park) and 26.0°C (commercial street); the neutral UTCI ranges (NUTCIR) were 20.8-27.4°C (coastal park) and 23.3-28.7°C (commercial street). (4) The upper thermal acceptable range limits of the coastal park and commercial street were 30.2 and 32.1°C, respectively, which were substantially higher than the upper NUTCIR limit, indicating that the residents in Dalian were well-adapted to hot weather. The results can provide a good reference for determining ideal design strategies to optimize the thermal environment of urban outdoor recreation spaces in summers and improve the quality of life in coastal cities.
Subject(s)
Quality of Life , Thermosensing , Humans , Climate , Cities , ChinaABSTRACT
A new congruent-melting lead barium borate, Ba2.5Pb1.5B12O22, was synthesized via a high-temperature solid-state reaction under atmospheric pressure. It crystallizes in the noncentrosymmetric space group Cmc21 with a unit cell of a = 19.051(8) Å, b = 10.726(3) Å, c = 8.612(3) Å, and Z = 4. It features a new functional building block (FBB), [B12O26]16-, that is made up of five [B3O8]7- and one [BO3]3- connected by sharing vertex O atoms. It is derived by introducing Pb into Ba2B6O11, which leads to a structural transformation from a centrosymmetric to a noncentrosymmetric space group. Its second harmonic generation response (SHG) is approximately 0.9 times that of KDP at the fundamental wavelength of 1064 nm and is also phase-matchable. It has a wide transparent region with a UV cutoff edge of about 250 nm according to the reflectance spectra and high thermal stability, which illustrates that it is a potential candidate for ultraviolet nonlinear optical materials.
ABSTRACT
Three new iodates SrTi(IO3)6·2H2O, (H3O)2Ti(IO3)6, and SrSn(IO3)6 have been synthesized via a facile hydrothermal method. The three compounds have zero-dimensional crystal structures composed of one [MO6]8- (M = Ti, Sn) octahedron connected with six [IO3]- trigonal pyramids. However, the particular coordination of Sr2+ cations results in distinct arrangements of lone pair electrons in an [IO3]- trigonal pyramid, which leads to large birefringences. More importantly, this work enriches the species crystal chemistry for [M(IO3)6]2- (M = Ti, Sn) clusters-containing iodates.