An Accelerated Incremental Radiosity Algorithm

The incremental radiosity method has been shown to be an efficienttechnique for providing global illumination in dynamic environments as it exploitstemporal coherence in object space. This paper presents an accelerated incremental radiosity algorithm, which is based on a dynamically followed partial matrix.This not only reduces the computation cost in determining incremental form-factorswhen the geometrical relationships between objects are constantly changing, but alsosimplifies the management of user interaction with comparatively little storage cost.

A Radiosity Solution for Curved Surface Environments

Radiosity has been a popular method for photorealistic image generation.But the determination of form factors between curved patches is the most difficult and time consuming procedure, and also the errors caused by approximating source patch's radiosity with average values are obvious. In this paper,a radiosity algorithm for rendering curved surfaces represented by parameters is described. The contributed radiosity from differential areas on four vertices of the source patch to a receiving point is calculated firstly, then the contribution from the inner area of the source patch is evaluated by interpolating the values on four corners. Both the difficult problem of determining form-factors between curved surfaces and errors mentioned above have been avoided. Comparison of the experimental results using the new algorithm has been made with the ones obtained by traditional method. Some associated techniques such as the visibility test and the adaptive subdivision are also described.

AN HIERARCHICAL OCCLUSION TEST ALGORITHM FOR GLOBAL ILLUMINATION SOLUTION

This paper presents an efficient hierarchical occlusion test algorithm to support the global illumination solution such as Ray Tracing and Radiosity. This method, which is based on a cone volume intersection examination, can rapidly remove the irrelevant parts in a scene and find the vertices which fall into the shadow area of a given object. It is an effective alternative to the conventional shadow feeler method.

上海崇明东滩启动区两地块室内自然采光应用模拟分析

自然光是大自然赋予人类无可取代的、健康高效的、可再生的宝贵资源,自然光的利用率成为新型建筑设计的重要参考标准,充分的室内采光模拟分析是建筑设计的重要参照。采用 Dali2018 模拟软件对上海市崇明东滩启动区 CMS15-0501 单元 D07-01、D08-01 地块主要功能空间的室内光环境进行分析,从采光系数、达标状态方面分析,深度解析该地区的自然采光效果,得出最大的采光系数为 22%,满足 2.2% 的采光系数标准值。

Downlink/Uplink Identification of Time-Division Duplexing-OFDMA Systems for Cognitive Radios

When coexisting with dual-link primary systems,secondary systems in cognitive radios should first distinguish between the primary downlinks and uplinks in order to efficiently explore their respective spectrum opportunities.Because of the assumptive prior knowledge about the time-frequency locations of primary downlinks and uplinks,this procedure is usually not considered in the design of cognitive radios.In this paper,a cooperative method is proposed for the downlink/uplink identification of time-division duplex-based orthogonal frequency-division multiple access systems.In this method,the power level of the primary link is extracted as the key feature,which also contributes to the subsequent cognitive behaviours.The effects of the primary and secondary systems and the effects of the detection parameters on the identification accuracy are all analysed in detail.The simulation results show that the proposed method can identify the primary links precisely and quickly with low complexity.

基于radioss钢板弹簧异常变形原因分析

钢板弹簧被用做非独立悬架的弹性元件,由于它兼起导向机构的作用,使得悬架系统大为简化。这种悬架广泛用于货车的前、后悬架中以及SUV的后悬架也使用钢板弹簧非独立悬架。钢板弹簧在理想情况自由状态一般采用圆弧状,压平程直线状.但在实际使用中,钢板弹簧在承载时会出现异常变形。本文基于altair公司的求解器radioss中的非线性算法功能对平衡悬架用钢板弹簧受垂直载荷时的变形进行分析。随着计算机技术的发展,采用radioss非线性算法计算对钢板弹簧进行承载分析成为探索钢板弹簧的一种新的计算方法。

A Switch Agent for Wireless Sensor Nodes with Dual Interfaces: Implementation and Evaluation

Data generation in wireless sensor networks could be bursty as it is dictated by the presence or absence of events of interest that generate these data. While conventional sensor nodes possessed only one radio interface, next generation sensor nodes are expected to have two （possibly more） radio interfaces, each with different ranges, capacities, and power consumptions. Equipping sensor nodes with dual radios has its own benefits and can be quite useful in handling bursty traffic while at the same time satisfying the application＇s delivery requirements. In this paper, we propose an adaptive interface switch agent that intelligently selects the interface to be used for data transmission at a sensor node based on the data burst length or end-to-end delay while taking into consideration power consumption and throughput. The proposed work generalizes earlier works in this area to enable both the source nodes and intermediate data forwarding nodes to initiate the activation of high power radios so that they can be utilized to a higher degree for converge-cast communication. We have performed extensive simulations with sensor nodes containing both IEEE 802.15.4 and IEEE 802.11 compatible radios. Our simulation results indicate that the switch agent yields throughput, delay, and packet delivery ratio comparable to the higher bandwidth interface alone, without incurring much energy wastage.

Achievable rate region for the multiple-access channel with multiple cognitive transmitters

A scenario where one ＇dumb＇ radio and multiple cognitive radios communicating simultaneously with a common receiver is considered. In this paper, we derive an achievable rate region of the multiple-user cognitive multiple-access channel （MUCMAC） under both additive white Gaussian noise （AWGN） channel and rayleigh fading channel, by using a combination of multiple user dirty paper coding （DPC） and superposition coding. Through cognition, it is assumed that the secondary users （SUs） are able to obtain the message of the primary user （PU） non-causally beforehand. Using this side information, the SUs can perform multiple user DPC to avoid the interference from the SU. Besides, the SUs can also allocate part of their transmit power to aid the PU, using superposition coding. Therefore, the capacity region of traditional multiple-access channel （MAC） can be enlarged. Moreover, some asymptotic results are shown as the number of SUs increases. In the AWGN case, it is illustrated that the maximum achievable rate of the PU grows logarithmically with the increase of the number of SUs, whereas in the Rayleigh case, we show that the cognitive gain will increase with the decreasing of the channel signal to noise ratio （SNR）.

An Improved Cyclostationary Feature Detection Based on the Selection of Optimal Parameter in Cognitive Radios

Spectrum sensing is an important part of cognitive radio systems to find spectrum hole for transmission which enables cognitive radio systems coexist with the authorized radio systems without harmful interference.In this paper,an improved cyclostationary feature detection method is proposed to reduce computational complexity without loss of good performance based on the optimal parameter selection strategy for choosing detection parameters of cyclic frequency and lag.Taking binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) signals as examples,the theoretical analyses are presented for choosing the optimal parameters.Simulation results are given to certify the correctness of the proposed parameter selection strategy and show the performance of the proposed method.

Location-aware downlink and uplink power control and throughput optimization in cellular cognitive radio networks

In this paper,we consider throughput maximization in cognitive radio systems with proper power control.In particular,we incorporate location-awareness into the power control design and maximize the average throughput of the cognitive system.As we shall show,the proposed approach effectively utilizes the“spatial opportunity”to maximize the system throughput,which clearly outperforms traditional power control methods.Further,the proposed approach still exhibits significant throughput gain even considering imperfect position information,with appropriate robust design modifications.