Rethinking place-making: aligning placeness factors with perceived urban design qualities (PUDQs) to improve the built environment in historical district

Understanding the concept of place is critically important for urban design and place-making practice, and this research attempted to investigate the pathways by which perceived urban design qualities (PUDQs) influence placeness factors in the Chinese context. Twelve hypotheses were developed and combined in a structural equation model for validation. The Tanhualin historical district in Wuhan, China was selected for the analysis. As a result, place attachment was verified as a critical bridge factor that mediated the influence of PUDQs on place satisfaction. Among the five selected PUDQs, walkability and space quality were revealed as the most influential factors associated with place attachment and place satisfaction. Accessibility was actually indirectly beneficial to place-making via the mediation of walkability. Corresponding implications and strategies were discussed to maintain the sense of place for historic districts

OPSquare:towards petabit/s optical data center networks based on fast WDM cross-connect switches and optical flow control

\u3cp\u3eOPSquare is an optical DCN architecture that potentially addresses the DCN scaling issues by employing parallel intra- and inter-cluster switching networks based on distributed fast WDM optical cross-connect switches and a novel top-of-rack switch architecture.\u3c/p\u3

OPSquare:towards petabit/s optical data center networks based on WDM cross-connect switches with flow control

\u3cp\u3eScaling the capacity while maintaining low latency and power consumption is a challenge for hierarchical data center networks (DCNs) based on electrical switches. In this work we present a novel optical DCN architecture called OPSquare that potentially addresses the scaling issues by employing parallel intra- and inter-cluster switching networks based on distributed fast WDM optical cross-connect (OXC) switches and a novel top-of-rack (ToR) switch architecture. The WDM OXC switches with nanoseconds reconfiguration time allow flexible switching capability in both wavelength and time domains and statistical multiplexing. Packet loss, latency, throughput, multi-path dynamic switching with flow control operation, and scalability will be discussed and experimentally evaluation by employing a 4×4 OXC prototypes. The potential of switching higher-order modulation and waveband signals further proves the suitability of OPSquare architecture for Petabit/s and low-latency DCN by using optical switches with moderate radix.\u3c/p\u3

Towards petabit/s all-optical flat data center networks based on WDM optical cross-connect switches with flow control

Scaling the capacity while maintaining low latency and power consumption is a challenge for hierarchical data center networks (DCNs) based on electrical switches. In this work we present a novel all-optical flat DCN architecture OPSquare that potentially addresses the scaling issues by employing parallel intra-/inter-cluster switching networks, distributed fast WDM optical cross-connect (OXC) switches, and a novel top-of-rack (ToR) switch architecture. The fast (nanoseconds) WDM OXC switches allow flexible switching capability in both wavelength and time domains and statistical multiplexing. The OPSquare DCN performance targeting Petabit/s capacity has been thoroughly assessed. First the packet loss, latency, throughput, and scalability are numerically investigated under realistic data center traffic model. Results indicate that when scaling the DCN size up to 1024 ToR switches, a packet loss ratio below 10-6 and a server end-to-end latency lower than 2 μs can be guaranteed at load of 0.3 with limited 20 kB buffer. Then, the experimental evaluation of the DCN by employing 4 × 4 OXC prototypes shows multi-path dynamic switching with flow control operation. The case deploying 32 × 32 and 64 × 64 OXC switches connecting 1024 and 4096 ToRs are emulated and limited performance degradation has been observed. The potential of switching higher-order modulation and waveband signals further proves the suitability of OPSquare architecture for Petabit/s and low-latency DCN by using optical switches with moderate radix

On the cost, latency, and bandwidth of lightness data center network architecture

We investigate and compare the cost, bandwidth, and latency of the LIGHTNESS data center network (DCN) architecture adopting optical switching technologies with current DCN architectures based on electrical switching technologies. The studies include the cost and latency models of all the required opto-electronics (electronic switches, transceivers, cables) and optical (circuit and packet switches) components to build the DCN architectures. Numerical results show that the LIGHTNESS DCN architecture has the lowest cost due to the huge reduction of expensive transceivers. Moreover, the flat LIGHTNESS DCN architecture outperforms the multi-stage electronic DCN architecture in terms of latency, while the bisection bandwidth can be dynamically and flexibly re-configured according to the required application

High performance DCN architecture based on flow-controlled optical switching system

present a novel high performance flat DCN employing bufferless and distributed sub-microsecond optical switches with wavelength, space, and time switching operation. Numerical and experimental investigations indicate potential scalability of the DCN to Petabit/s capacity

OPSquare:a flat dcn architecture based on flow-controlled optical packet switches

\u3cp\u3eAiming at solving the scaling issues of bandwidth and latency in current hierarchical data center network (DCN) architectures, we propose and investigate a novel optical flat DCN architecture in which the number of interconnected ToRs scales as the square of the optical packet switches' (OPS) port count (OPSquare). The proposed flat DCN architecture consists of two parallel interand intra-cluster networks that are built on a single-hop OPS with nanosecond time and wavelength switching for efficient statistical multiplexing operations. Fast optical flow control is implemented for solving packet contentions that may occur at the buffer-less optical switches. The performance of OPSquare DCN in terms of scalability, packet loss, latency, and throughput is assessed by a numerical simulation employing OMNeT++ under realistic data center (DC) traffic. The results report a server-to-server latency of less than 2 ?s (including packet retransmission), a packet loss <10?5 at a load of 0.4, and aDC size of 10,240 servers with a ToR buffer size equal to 50 KB for all traffic patterns. Moreover, the cost and power consumption of the OPSquare DCN have been studied and compared with fat-tree DCN based on electrical switches and H-LION connected by an arrayed wave guide grating router (AWGR). The results indicate 23.8% and 39% cost and power savings, respectively, for the OPSquare DCN supporting 160,000 servers with respect to the fat-tree DCN. The OPSquare has a cost saving of 56% compared with H-LION for a 160,000-server DCN.\u3c/p\u3