一种平衡式环行器收发隔离电路的设计与实现

对于收发天线一体、收发频率相近、收发信号同时存在的无线电通信应用场景,比如UHF RFID的读卡器,目前一般使用单独的环行器来进行收发隔离,但其隔离度有限,一般在20 dB左右。从理论上分析了由两个环行器组成的平衡式环行器隔离电路的隔离原理,并提出了一种改进平衡式环行器收发隔离电路,同时制作了电路模块。网络分析仪测试表明,该改进平衡式环行器收发隔离电路的发射端到天线端的传输损耗和天线端到接收端的传输损耗都在1 dB以内,在连接驻波比为1.2∶1的板式天线情况下,其收发隔离度达到了50 dB以上;实测当射频输入功率处于0.1 W~8.0 W区间时,该电路的收发隔离度稳定在40 dB以上,较使用单独环行器时的隔离度至少提高了20 dB。

悬臂式悬挂环行轨的可靠性强度设计与置信水平评估

悬臂式悬挂环形轨由于结构形式的特性，其稳定性与可靠性以及使用置信水平已成为设计的焦点，本文从设计入手，用可靠性强度理论加以阐述，并用可靠度方式对其结构的置信水平进行评估。

浅析供热系统的热网系统形式

本文将对集中采暖热网系统的几种形式加以综合分析,并提出了同程管网系统在集中供热管网系统的可行性。

采暖热网系统形式的探讨

本文将集中采暖热网系统的几种形式作以综合分析,提出了同程管网系统在集中供热管网系统的可行性。由于集中供热系统具有如下优点:(1)可以节约大量能源;(2)可以大量减少锅炉房管理操作人员,提高专业人员的水平;(3)可以大大改善环境污染问题,为人们创造一个清新的生活环境。因此,城市集中供热近几年在迅猛发展。

管壳式换热器的改进设计

本文通过介绍环行分程隔离管壳式换热器的结构和设计思路,对换热器设备进行更新,不仅节约成本,还使换热器换热效果得到明显提升。

Ethogram of Yangtze finless porpoise calves (Neophocaena phocaenoides asiaeorientalis)

Underwater behavioral patterns of one Yangtze finless porpoise （Neophocaena phocaenoides asiaeorientalis） calf in captivity and those performed on the water surface by two calves in semi-natural environment were focally followed and continuously recorded until one year postpartum to construct the ethogram. The results indicate that 1） the three calves could display diverse and active behavioral patterns; 2） soon after birth, patterns critical for survival appeared first; 3） playful and social patterns predominated the ethogram; 4） most of the patterns were alike across age classes; 5） most of the patterns appeared at the calves’ early life stage. It is possible that the above characteristics are adaptively shaped by the aquatic and social life of this subspecies.

Mixing Characteristics and Bubble Behavior in an Airlift Internal Loop Reactor with Low Aspect Ratio

The present study summarizes the results of macro-and micro-mixing characteristics in an airlift internal loop reactor with low aspect ratio(H/D≤5) using the electrolytic tracer response technique and the method of parallel competing reactions respectively. The micro-mixing has never been investigated in airlift loop reactors. The dual-tip electrical conductivity probe technique is used for measurement of local bubble behavior in the reactor. The effects of several operating parameters and geometric variables are investigated. It is found that the increase in superficial gas velocity corresponds to the increase in energy input, liquid circulation velocity and shear rate, decreasing the macro-mixing time and segregation index. Moreover, it is shown that top clearance and draft diameter affect flow resistance. However, the bubble redistribution with a screen mesh on the perforated plate distributor for macro-mixing is insignificant. The top region with a high energy dissipation rate is a suitable location for feeding reactants. The analysis of present experimental data provides a valuable insight into the interaction between gas and liquid phases for mixing and improves the understanding of intrinsic roles of hydrodynamics upon the reactor design and operating parameter selection.

Analysis and Measurement of Mass Transfer in Airlift Loop Reactors

Inter-phase mass transfer is important to the design and performance of airlift loop reactors for either chemical or biochemical applications, and a good measurement technique is crucial for studying mass transfer in multiphase systems. According to the model of macro-scale mass transfer in airlift loop reactors, it was proved that the airlift loop reactor can be regarded as a continuous stirred tank reactor for measuring mass transfer coefficient. The calculated mass transfer coefficient on such a basis is different from the volumetric mass transfer coefficient in the macro-scale model and the difference is discussed. To describe the time delay of the probe response to the change of oxygen concentration in the liquid phase, a model taking into account the time constant of response is es-tablished. Sensitivity analysis shows that this model can be used to measure the volumetric mass transfer coefficient. Applying this model to the measurement of volumetric mass transfer coefficient in the loop reactor, results that co-incide with the turbulence theory in the literate were obtained.

A Ring Signature Suitable for Wireless Sensor Networks

Wireless Sensor Network （WSN） nodes are severely limited by their power, communication bandwidth, and storage space, and the traditional signature algorithm is not suitable for WSN environments. In this paper, we present a ring signature scheme designed for WSNs. In this scheme, all of the wireless sensor nodes are divided into several sub-groups and the sub-group nodes are used to generate the signature instead of the WSN cluster nodes. This scheme can effectively avoid the single node failure problem, and it also has a high availability. All nodes are flee to sign their own message, and the nodes that generate signatures can simultaneously calculate their own part of the signature, meeting the distributed parallel computing requirements. Compared with the traditional ring signature, this scheme reduces the energy consumption, and therefore is very suitable for WSNs.

The Essence of Group Discussions

Group discussions are very important in oral English classes. It maximizes students＇ speaking time in a specified-time period. Group discussions have a strong positive effect on the atmosphere in the classroom and the behaviors of the students as they can get more ideas from their friends, and sometimes students don＇t even understand the topic for discussion but by interacting with others they can understand the topic. Particularly it is a good warm-up in conversational classes. The most important reason for using group discussions before speaking tasks is to reduce students＇ nervousness of making mistakes. And this encourages students to be more active in speaking class.

Estimating walking access area for rail transit station based on discrete choice model

The discrete choice model is used to estimate the walking access area of rail transit stations while considering the influence of existing competition from other traffic modes. The acceptable walking access area is determined according to the willingness of passengers to walk who prefer rail transit compared with bus and automobile. Empirical studies were conducted using the survey data of six stations from the rail transit in Nanjing, China. The results indicate that the rail transit is more preferable compared with bus and private automobile in this case when excluding the influence of individual and environmental factors. It is found that passengers tend to underestimate their willingness to walk. The acceptable walking access area of every rail transit station is different from each other. Suburban stations generally have a larger walking access area than downtown stations. In addition, a better walking environment and a scarcer surrounding traffic environment can also lead to a larger walking area. The model was confirmed to be effective and reasonable according to the model validation. This study can be of benefit to the passenger transportation demand estimation in the location planning and evaluation of rail transit stations.

Experiment investigation on visualization and operating characteristics of closed loop plate oscillating heat pipe with parallel channels

Using ethanol or acetone as the working fluid, visualization of oscillations in steady state was observed visually by high-speed cameras, and temperature oscillating and heat transfer characteristics of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying liquid filled ratios(50%, 70%, 85%), section scales(1 mm×1 mm and 1 mm×1.5 mm), inclination angles, working fluids and heating inputs. It was found that during operating there was mixed flow consisting of plug flow and annular flow in channels of oscillating heat pipe at steady-state. There was an equilibrium position for working fluid of condenser during oscillating, and periodic oscillations occurred up and down in the vicinity of equilibrium position. With heat input increasing, equilibrium position rose slowly as a result of vapor pressure of evaporation.Evaporation temperature oscillating amplitude possessed a trend of small-large-small and frequency trend was of small-large during steady-state. It may be generally concluded that temperature, whether evaporator or condenser, fluctuated sharply or rose continuously when oscillating heat pipe coming to dry burning state. Simultaneously, it was found that temperature difference of cooling water possibly dropped with heat input rising during dry burning state. Thermal resistance of No. 2 with acetone was lower than that of No. 1 during experiments, but No. 2 achieving heat transfer limit was earlier than No. 1. However, with ethanol, thermal resistance of No. 1 and No. 2 were similar with the heating input less than 110-120 W and filling ratios of 50% and 70%. And with filling ratio of 85%, heating transfer performance of No. 2 was better compared to No. 1 during all the experiments.

Green Product Purchase Behaviour： Relevance for Muslims

Recent climate change phenomenon and other prevailing environmental problems have marked a need for human beings to rethinking their way of life, particularly in their relationship with the environment. In Islam, human beings are made responsible at his/her best efforts in preserving the environment including practising pro-environmental behaviour. Due to strong pressures by Western public movements since past decades, the emergence of green products in marketplace has provided an alternative and better way of consumption in reducing adverse environmental impacts. However, little attention has been paid on relating green product purchase behaviour with Islamic teachings. Therefore, the paper discusses the role of green products purchase behaviours in reducing adverse environmental impacts and its relationship with Islamic teachings as mentioned in AI-Quran and As-Sunnah. Besides, the importance of green product knowledge in determining green product purchase behaviour is also discussed. Implications from the study would provide some insights on links between green product purchase behaviours and Islamic teachings as well as improving understanding on the influence of knowledge on pro-environmental behaviours both in empirical manner and as being outlined in Islam.

The Ecological Crisis and the Principle of Relationality in African Philosophy

The way that humans think about the earth certainly affects the way that they relate and behave towards the earth and all its life forms. The various ideologies or worldviews that humanity has experienced such as dualism, capitalism, holism, animism, ubuntu, ukama, vital force, colonialism, and so forth are all different ways of thinking and relating to the earth. The paper argues that dualistic ways of thinking or viewpoints that radically separate the human as distinct from the earth are hostile to both human and earth flourishing. It further argues that the ecological crisis which has witnessed the destruction and pollution of the ecosystems and other devastations cannot be solved when humans continue to see the earth as an object for conquest and exploitation. Using a critical hermeneutics method, the paper affirms that the African principle of relationality can help in mitigating the environmental crisis. It finds and concludes that if this principle is radically practiced, a better environment will be created.

Geodesic Acoustic Mode in Toroidally Axisymmetric Plasmas with Non-Circular Cross Sections

The geodesic acoustic mode （GAM）, first predicted by Winsor, Johnson and Dawson in an attempt to explain some experimentally observed low frequency oscillations in stellarators, is a special electrostatic fluid mode with low mode number and coupled with the so-called geodesic curvature of a toroidally confined plasma. The recent on this mode are due to the close relevance of the stabi- lization of drift turbulence by both the zonal flow and the GAM. Previously, the GAM was illustrated in very simple geometries,

Effect of Different Blood Cycle Modeson Mass Transfer of Artificial Kidney

Based on the one-dimensional and unsteady-state Krogh model, this paper investigates mass transfer of artificial kidney under three blood cycle modes during the course of hemodialysis. The variations of the permeable solute clearance with increasing time and the dialysis time with increasing blood flux are simulated in detail,and then one optimal blood cycle mode is acquired. The results are very important to improve the clinical dialysis efficiency of artificial kidney.