Understanding occupancy and user behaviour through Wi-Fi-based indoor positioning

A 30-day monitoring campaign was conducted in a university library building to investigate the usefulness of a novel Wi-Fi-based indoor location system for revealing indoor occupancy patterns and related user behaviour. The system has demonstrated its effectiveness in providing occupancy information with a relatively high degree of granularity and accuracy in this study. The occupancy results revealed that the current 24-hour opening policy for the library during term time did not correlate with usage. On the other hand, the eight-hour library-opening duration during the summer holiday period could be extended to include the early evening hours to benefit user productivity. Four occupancy patterns were identified based on cluster analysis. Most users were found to belong to the short-occupancy one-time visitor type, while a minority were long-occupancy users. The cross-correlations between various occupancy parameters were investigated. For example, the pattern of user arrival times at the library was found to be significantly correlated with their study durations. Further, data analysis showed that the majority of long-occupancy users tended not to have frequent breaks with some taking no break for four hours. This could have implications for their health and wellbeing as well as their productivity.     

Rental security and the property manager in a tenant’s search for a private rental property

Abstract

This article builds on current understandings of rental security by exploring the important role of the property manager in a tenant's search for a private rental property. In the absence of any legislated right to housing, as is the case in many Anglophone societies, the decision to accept or reject a tenancy application is in the hands of the landlord, and, in many cases, the property manager, who provides expert advice to the landlord. A qualitative content analysis of blogs featured on two national websites advertising rental properties in Australia, identifies six aspects of interactions between the tenant and property manager argued to impact a tenant’s ability to secure a rental property: responsibility, making an impression, established relationships, honesty, flexibility and creative thinking. Findings suggest that understandings of rental security need to extend beyond a tenant’s experience while leasing and must incorporate experiences during the search for a private rental property.     

Vision-based estimation of the number of occupants using video cameras

Although occupancy information is critical to energy consumption of existing buildings, it still remains to be a major source of uncertainty. For reliable and accurate occupant modeling with minimal uncertainties, capturing precise occupant information on occupants is essential. This paper proposes a computer vision-based approach that utilizes deep learning architectures to estimate of the number of people in large, crowded spaces using multiple cameras. Various vision techniques (head detection, background elimination, head tracking) are implemented in three methods: (i) a method that instantaneously counts people in a scene, (ii) a method that incrementally counts people entering/exiting a room and (iii) a combination of the first two methods. These methods were applied in a classroom with heavy occlusions, and resulted in a high prediction capacity when compared to ground truth measurements. Future work in video-analytical approaches can address problems regarding lowering the computational cost of analysis, capturing occupancy data in complex room geometries and addressing concerns in privacy preservation.     

On the discontinuous yielding phenomena observed in a Nb---Ti---Al alloy

Alloys based on niobium have many attractive mechanical properties which make them candidate materials for use in high-temperature corrosive environments. In this work, alloys containing additions of titanium and aluminum have been studied since these elements provide improved oxidation resistance and lower density. This paper describes the discontinuous yielding phenomena which are observed in Nb-40Ti-15Al. A yield-point is seen after aging at intermediate temperatures, and serrated yielding is seen on tensile testing at various temperatures. Various experiments are described which indicate that a Portevin-Le-Chatelier-type effect occurs in this alloy. Evidence will be presented from which it is argued that this serrated yielding is caused by the dynamic precipitation and dissolution of the ω-phase.     

Coherent Spin Transport and Suppression of Spin Relaxation in InSb Nanowires with Single Subband Occupancy at Room Temperature

A longstanding goal of spintronics is to inject, then coherently transport, and finally detect electron spins in a semiconductor nanowire in which a single quantized subband is occupied by the electrons at room temperature. Here, the achieving of this goal in electrochemically self‐assembled 50‐nm diameter InSb nanowires is reported and substantiated by demonstrating both the spin‐valve effect and the Hanle effect. Observing both effects in the same sample allows one to estimate the electron mobility and the spin relaxation time in the nanowires. It is found that despite four orders of magnitude degradation in the mobility compared to bulk or quantum wells and a resulting four orders of magnitude increase in the Elliott‐Yafet spin relaxation rate, the spin relaxation time in the nanowires is still about an order of magnitude longer than what has been reported in bulk and quantum wells. This is caused by the elimination or suppression of the D’yakonov‐Perel’ spin relaxation through single subband occupancy. These experiments shed light on the nature of spin transport in a true quantum wire and raise hopes for the realization of a room‐temperature Datta‐Das spin transistor, where single subband occupancy is critical for optimum performance.     

南海白频谱占用度的测量和分析

为了掌握数字红利频谱在南海上的实际利用情况,根据最新的频谱占用度建议书ITU-R SM.1880以及移动监测设备建议书ITU-R SM.1723-2,搭建海上移动测量软硬件环境,对该频段在环海南岛近海海域的频谱占用度进行实际的移动测量,并根据李氏定律进行采样,最后分析所得数据,得出时间-频率-占用度的对照图,测试结果显示被测海域的数字红利频谱利用率偏低。     

~(13)C固体核磁共振法测定CH_4-THF二元水合物的微观结构特征

认识天然气水合物的微观结构特征对于研究其形成机理和储运技术具有重要的意义。为此,采用~(13)C固体核磁共振(SSNMR)技术分析了四氢呋喃(THF)水合物和CH_4—THF二元水合物的笼型结构特征,确定了后者的结构类型和客体分子分布特征,并获得了后者客体分子的笼占有率和水合指数。实验结果表明:①纯THF水合物的2个共振谱峰的化学位移分别为668.3和δ26.1,其THF分子填充在Ⅱ型水合物大笼(5~(12)6~4)中;②CH_4—THF二元水合物和纯THF水合物一样,同为Ⅱ型结构,其THF分子仅填充在大笼(5~(12)6~4)中,笼占有率为0.994 8,而CH_4分子仅占据小笼(5~(12)),笼占有率较低,仅为0.482 5;③由于CH_4分子填充率较低,二元水合物的水合指数为8.67,明显大干理想值(5.67),水合物储气量较小;④CH_4—THF二元水合物中客体分子笼占有率的大小与水合物的生成条件(温度、压力)及制备方法(反应状态、时间等)有关,改变水合物的形成条件,在一定程度上可以调节笼型水合物客体分子的笼占有率,从而提高水合物的储气密度。     

Optimization of the Pore Structures of MOFs for Record High Hydrogen Volumetric Working Capacity

Metal–organic frameworks (MOFs) are promising materials for onboard hydrogen storage thanks to the tunable pore size, pore volume, and pore geometry. In consideration of pore structures, the correlation between the pore volume and hydrogen storage capacity is examined and two empirical equations are rationalized to predict the hydrogen storage capacity of MOFs with different pore geometries. The total hydrogen adsorption under 100 bar and 77 K is predicted as n_tot= 0.085× V_p − 0.013× V_p² for cage-type MOFs and n_tot= 0.076× V_p − 0.011× V_p² for channel-type MOFs, where V_p is the pore volume of corresponding MOFs. The predictions by these empirical equations are validated by several MOFs with an average deviation of 5.4%. Compared with a previous equation for activated carbon materials, the empirical equations demonstrate superior accuracy especially for MOFs with high surface area (i.e., S_BET over ≈3000 m² g⁻¹). Guided by these empirical equations, a highly porous Zr-MOF NPF-200 (NPF: Nebraska Porous Framework) is examined to possess outstanding hydrogen total adsorption capacity (65.7 mmol g⁻¹) at 77 K and record high volumetric working capacity of 37.2 g L⁻¹ between 100 and 5 bar at 77 K.     

Enhancement of Probabilistic Grid-based Map for Mobile Robot Applications

In this paper, a novel approach for fine-tuning of the grid-based map-building algorithm is reported. The traditional occupancy grid-based map-building algorithm uses a fixed probability distribution function of the sonar readings and disregards the information from the environment. In our approach, the probability distribution function is tuned by fuzzy rules formed from the information obtained from the environment at each sonar data scan. A Bayesian update rule is then used to update the occupancy probabilities of the grid cells. The proposed map-building algorithm is compared with other grid-based map-building methods through simulations and experiments. The simulation and experimental studies suggest that sharp grid maps can be obtained by incorporating fuzzy rules during the grid-based map generation. In comparison with other algorithms, improved convergence has also been noted.     

一种交通拥堵自动检测方法

目前,高速公路交通拥堵日趋频繁,然而大部分高速公路的管理方式仍然是通过人工查看轮巡监控视频来发现交通拥堵,效率低下。本文提出一种对高速公路轮巡监控视频自动检测交通拥堵的方法。该方法实时检测监控视频场景是否轮巡、切换、变动,自适应提取变动场景的道路边界结构并分类,然后在提取的道路边界结构范围内,计算宏观边缘占有率与加权平均光流速度两个宏观交通状态参数,并构造特征集,根据不同的道路边界类型选择对应支持向量机来实现对交通拥堵的自动检测和判别。实验结果表明,该方法能有效地对轮巡模式工作的高速公路监控视频检测交通拥堵,检测时间不大于30s,检测正确率达91.8%。