Space-time Conditions Research Articles

Sense of safety toward tourism destinations: A social constructivist perspective

Travel is inherently associated with risk. Scholars have examined the composition of destination safety perceptions, safety climate, and the role of safety as a sub-dimension of destination image. This study aims to address a research gap by revealing a more detailed construction process of tourists' sense of destination safety from a social constructivist perspective. By collecting data from a leading Chinese tourism social media platform, tourists' sense of safety is constructed based on key subjects and contents at different travel stages, that is, before, during, and after a trip. The findings of the study contribute to the literature on tourism safety by emphasizing the need to understand tourists' sense of safety under various space–time conditions. Based on multiple stages of tourists’ sense-of-safety construction, this study provides practical implications to help destination management organizations enhance local tourism safety and management. • Sense of safety is constructed under various space-time conditions. • Sense of safety is formed via the interaction and negotiation between key subjects. • Key subjects vary at three stages of travel, pre-, during- and post. • Content of sense of safety changes at each stage of the trip.

A Field Study on the Law of Spatiotemporal Development of Rock Movement of Under-Sea Mining, Shandong, China

The phenomenon of rock movement in mining areas has always been a difficult problem in mining engineering, especially under complicated geological conditions. Although the backfilling method mitigates the destruction of the surrounding rock, deformation can still exist in the mining area. In order to ensure the safety of under-sea mining, it is necessary to study the rock movement laws and the mechanisms. This paper focuses on a settlement analysis of the monitoring data of the No. 55 prospecting profile. By analyzing the shape of the settlement curves, the spatial distribution characteristics of settlements of different mining sublevels are summarized. Additionally, the fractal characteristics of the settlement rate under different space–time conditions are studied. We also discuss the relationship between the fractal phenomenon and the self-organized criticality (SOC) theory. The findings are of great theoretical value for the further study of mining settlements to better understand the physical mechanisms of internal movement and rock mass failures through the fractal law of the settlement. Furthermore, elucidating the rock movement law is an urgent task for the safety of seabed mining.

Collaborative location recommendations with dynamic time periods

This study proposes a location-based collaborative filtering recommendation system with dynamic time periods (LCFDTPs) for recommending timely and suitable points of interest (POIs) to mobile users. The system expedites calculating similarity based on POI recency and enables mobile users to promptly obtain recommended items that closely match their current space–time conditions by selecting different strategies for dissimilar situations. The performance of the proposed system was evaluated through simulations. The simulation results revealed that compared with three existing strategies, the proposed LCFDTP system demonstrated higher recommendation accuracy and coverage and a shorter average recommendation time. When the users’ moving velocity was set to 50 km/h and the query radius was set to 2 km, the recommendation precision of the proposed system was 61% higher than those of the other strategies. Moreover, the recommendation coverage and average response time of the LCFDTP system were 9% higher and 62% shorter than those of the other compared strategies, respectively. The LCFDTP system can also improve the POI recommendation quality by applying location-based services, thus enhancing user satisfaction.

Gedanken Experiment for Looking at δg<sub>tt</sub> for Initial Expansion of the Universe and Influence on HUP via Dynamical Systems, with Positive Pre-Planckian Acceleration

We examine through the lens of dynamical systems a “one dimensional” time mapping of emergent VEV from Pre-Planckian space time conditions. As it is, we will from first principles examine what adding acceleration does as to the HUP previously derived. In doing so, we will be trying it in our discussion with the earlier work done on the HUP. not equal to zero, constant, but large would frequently imply which would have three dissimilar real valued roots. And the situation with not equal to zero yields more tractable result for which will have implications for the HUP inequality in Pre-Planckian space-time, and buttresses an analysis of a 1 dimensional “time” mapping for emergent VEV (vacuum expectation values).

Quantum volume and length fluctuations in a midi-superspace model of Minkowski space

In a (1+1)-dimensional midi-superspace model for gravitational plane waves, a flat space–time condition is imposed with constraints derived from null Killing vectors. Solutions to a straightforward regularization of these constraints have diverging length and volume expectation values. Physically acceptable solutions in the kinematic Hilbert space are obtained from the original constraint by multiplying with a power of the volume operator and by a similar modification of the Hamiltonian constraint, which is used in a regularization of the constraints. The solutions of the modified Killing constraint have finite expectation values of geometric quantities. Further, the expectation value of the original Killing constraint vanishes, but its moment is non-vanishing. As the power of the volume grows, the moment of the original constraint grows, while the moments of volume and length both decrease. Thus, these states provide possible kinematic states for flat space, with fluctuations. As a consequence of the regularization of operators, the quantum uncertainty relations between geometric quantities such as length and its conjugate momentum do not reflect naive expectations from the classical Poisson bracket relations.

Ultrasound-assisted third-liquid phase-transfer catalyzed esterification of sodium salicylate in a continuous two-phase-flow reactor

The esterification of sodium salicylate to synthesize butyl salicylate by third-liquid phase-transfer catalysis under ultrasound irradiation was investigated in a continuous two-phase-flow reactor. The reactor was designed to keep the third-liquid phase in the middle part and to have the aqueous and organic phases flowing through it in countercurrent. Using tetra- n-butylphosphonium bromide to prepare the third-liquid phase for this esterification, the product yield in the organic outlet (toluene) at 70 °C was 49.7% in silent condition, showing the reaction promoted simply by countercurrent mixing of the aqueous and organic phases. In the conditions of space time at 168 min, stirring at 150 rpm and ultrasound irradiation (28 kHz, 300 W), the product yield was greatly enhanced to 78.2%. As prepared, above 90% of the added catalyst existed in the third-liquid phase, and after 4-h on stream for a large excess of n-butyl bromide to sodium salicylate, the fraction of catalyst retaining in the reactor was reduced to around 80%. The distributions of catalysts between phases before and after reaction were analyzed. A kinetic model was proposed to estimate the apparent rate constants, and the feasibility for third-liquid phase-transfer catalysis assisted by ultrasound irradiation in a continuous flow reactor was demonstrated.

Modeling and Simulation of a Non-Isothermal Tubular Thermal Cracker

A 2-dimensional model for thermal cracking of ethane under laminar flow conditions has been established. Based on a molecular mechanistic model for ethane cracking, the model consists of eight mass balance equations along with energy balance and momentum balance equations. This set of coupled partial differential equations is solved numerically by using finite difference backward implicit scheme. The species concentration and temperature profiles in radial and axial directions are predicted with variation of properties with temperature and composition. The model predicts maxima in the concentrations of propylene and acetylene within the reactor. The simulations for the effect of operational parameters on product distribution and temperature are also carried out. The parameters—space time and wall temperature and their range of variations are considered. Wall temperature variation is taken from 950 to 1100°C and space time conditions are taken from 0.2 to 0.45 s. An increase in space time and/or wall temperature results in higher ethane conversion.

Necessary Space—Time Conditions for Human Interaction

Key scientific and application questions concern the relationships between individual-level activities and their effects on broader human phenomena, such as transportation systems and cities. Continuing advances in geographic information science, location-aware technologies, and geosimulation methods offer great potential for observational and simulation studies of human activities at high levels of spatiotemporal resolution. The author contributes by developing rigorous statements of the necessary space–time conditions for human interaction by extending a measurement theory for time geography. The extended measurement theory identifies necessary conditions both for physical and for virtual interaction. The theory suggests elegant and tractable solutions that can be derived from data available from location-aware technologies or geosimulation methods. These conditions and their solutions could be used to infer the possibilities for human interaction from detailed space–time trajectories and prisms generated from observation or simulation studies.

Halocarbons in Aqueous matrices from the Rennick Glacier and the Ross Sea (Antarctica)

Aqueous matrices from Antarctica were analysed for three volatile chlorinated hydrocarbons (VCHCs): tetrachloromethane (CCl4), trichloroethylene (C2HCl3) and tetrachloroethylene (C2Cl4). The matrices analysed were snow from Rennick Nèvè and Rennick Glacier sampled during the Italian Expeditions of 1995/96 and 1996/97, respectively, and seawater, pack ice, sea-microlayer, subsuperficial water and freshwater, collected during the Italian Expedition of 1997/98. Extractions from the aqueous matrices were carried out in Antarctica (the laboratories of the Italian Base, Terra Nova Bay). Because of the critical space–time conditions in these laboratories, an extraction procedure was developed, suitable for large volumes of water (10 L), in order to combine the extraction of other classes of organic compounds (polychlorinated biphenyls, polycyclic aromatic hydrocarbons and chlorinated pesticides) with those of our direct interest. The VCHC organic extracts were analysed in Italy by GC-ECD and GC-MS. The analyses confirmed the presence of the three halocarbons in Antarctica in quantities ranging from units to some dozens of nanograms per kilogram. The results were evaluated with respect to the local distribution of these compounds and their diffusion on a global scale.

INTERLOCKING PROPERTIES OF THE LINEAR DATA DEPENDENCE METHOD

We analyse the properties of linear transformations used in the Data Dependence method. Actually the Dependence Graph lDGr is mapped to a Space Time Graph lSTGr with special properties. The transformation is valid if 4 conditions are satisfied: the timing condition, the space time condition, the regular data flow condition and the existence condition. The obtained STG has not been analysed in the literature previously. STG will have the special property interlocking translation. This property can be efficiently used to obtain the folding or the fast systolic design so the efficiency of the obtained systolic designs will be doubled. As an example, the interlocking translation and composition is implemented for the ARMA Biter, with many applications in modern digital signal processing. The H. T. Kung ARMA filter linear array uses 50p more communication links and the processors are twofold more complex than the new proposed implementation. The processors are utilized in every time ...