Leveraging Large Language Models in Conversational Recommender Systems

A Conversational Recommender System (CRS) offers increased transparency and control to users by enabling them to engage with the system through a real-time multi-turn dialogue. Recently, Large Language Models (LLMs) have exhibited an unprecedented ability to converse naturally and incorporate world knowledge and common-sense reasoning into language understanding, unlocking the potential of this paradigm. However, effectively leveraging LLMs within a CRS introduces new technical challenges, including properly understanding and controlling a complex conversation and retrieving from external sources of information. These issues are exacerbated by a large, evolving item corpus and a lack of conversational data for training. In this paper, we provide a roadmap for building an end-to-end large-scale CRS using LLMs. In particular, we propose new implementations for user preference understanding, flexible dialogue management and explainable recommendations as part of an integrated architecture powered by LLMs. For improved personalization, we describe how an LLM can consume interpretable natural language user profiles and use them to modulate session-level context. To overcome conversational data limitations in the absence of an existing production CRS, we propose techniques for building a controllable LLM-based user simulator to generate synthetic conversations. As a proof of concept we introduce RecLLM, a large-scale CRS for YouTube videos built on LaMDA, and demonstrate its fluency and diverse functionality through some illustrative example conversations

Ecological vulnerability assessment of coral islands and reefs in the South China Sea based on remote sensing and reanalysis data

Coral reefs are ecosystems that are highly vulnerable to external environmental impacts, including changes associated with ocean acidification and global warming. Assessing the vulnerability of coral reef growth environments over large areas of the sea is a difficult and complex process, as it is influenced by many variables. There are few studies on environmental vulnerability assessment of coral islands and reefs in the South China Sea. It is therefore particularly important to understand the environmental sensitivity of corals and how coral communities respond to changes in climate-related environmental variables. In this study, indicators were selected mainly from natural environmental factors that hinder the development of coral reefs. The sea surface temperature (SST), sea surface salinity (SSS), wind velocity (WV) and direction, sea level height (SL), ocean currents (OC), and chlorophyll concentration (Chl) of coral reefs in South China Sea Island were integrated to calculate the coral reef environmental vulnerability region. In a GIS environment, Spatial Principal Component Analysis (SPCA) was used to develop sensitivity models and evaluate the ecological vulnerability of coral reefs. Based on the Environmental vulnerability indicator (EVI) values, the study area was classified as 5 grades of ecological vulnerability: Potential (0.000–0.577), Light (0.577–0.780), Medium (0.780–0.886), Heavy (0.886–0.993) and Very Heavy (0.993–1.131). Sensitivity models identified regional gradients of environmental stress and found that some coral reefs in western Malaysia and southwestern Philippines have higher vulnerability. Meanwhile, the study found that the reefs of Paracel Islands and Macclesfield Bank areas of medium vulnerability. Future use of high-precision data from long time series will allow better estimates of site-specific vulnerability and allow for the precise establishment of marine protected areas so that the ecological diversity of coral reefs can be sustained

On Optimal Physical Synthesis of Sleep Transistors

Considering the voltage drop constraint over a distributed model for power/ground (P/G) network, we study the following two problems for physical synthesis of sleep transistors: the min-area sleep transistor insertion (and sizing) (T IS) problem with respect to a fixed P/G network, and the simultaneous sleep transistor insertion and P/G network sizing (T IPGS) problem to minimize the weighted area of sleep transistors and P/G network. We show that there may exist multiple sleep transistor insertion solutions that all lead to a same minimum area in the T IS and T IPGS problems. We develop optimal algorithms to T IS and T IPGS problems by modeling the circuit as a single current source, and then extend to the case modeling the circuit as distributed current sources. Compared with the best known approach, our algorithms achieve area reduction by up to 44.1% and 61.3% for T IS and T IPGS, respectively

Hydrological drought in dongting lake area (China) after the running of three gorges dam and a possible solution

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Dongting Lake is located at the downstream of Three Gorges Dam (TGD) and the hydrological drought is intensified after the impoundment of TGD as the dry period has been extended from 123 days/year before the operation of TGD (1981–2002) to 141 days/year (2003–2016) on average. Particularly, the Dongting Lake’s water shortage becomes very severe. To solve the problem caused by upstream dams, an innovative flood control scheme (IFCS) was introduced, and its feasibility of application in Dongting Lake is studied using the hydrodynamic module of Mike 21. The results show the IFCS can effectively convert the peak discharge of floodwater in wet seasons into water resources in dry seasons as the IFCS could significantly increase the usable water storage of the lake. For example, the usable water storage could increase to 2.85 billion m3 and 1.81 billion m3 in the extreme drought year of 2006 and 2011, respectively. The average increment of the water level would be about 0.4 m, 0.6 m, and 0.5 m in the West Dongting Lake (WDL), South Dongting Lake (SDL), and the East Dongting Lake (EDL), respectively, if the water stored in the inner lake was discharged uniformly in 30 days (27 November to 27 December 2006) with the application of IFCS. This study may provide an innovative method to alleviate the water shortage problem in Dongting Lake and other similar lakes

Estimation of Residence Time and Transport Trajectory in Tieshangang Bay, China

The pollutant residence time and transport trajectory in Tieshangang Bay are considered to have significant effects on deteriorating water quality. To understand the pollutant transport behaviors in Tieshangang Bay, we developed a combination model (MIKE 21 FM) of the hydrodynamic module and particle tracking module. Simulation results suggest that the water velocities in the west and east troughs (near the entrance of the bay) are distinctly higher than any other areas. Meanwhile, small semi-enclosed bays adjacent to the shoreline could affect local water flow patterns, thereby causing gyres within them. The residence time of pollutants in Tieshangang Bay is significantly affected by seasonal variations (i.e., the residence time of pollutants in Tieshangang Bay in winter is less than that in summer). The results of transport trajectory simulations reveal that the bay head is a slow flushing zone, while the entrance of the bay (west trough) can be identified as a fast flushing zone

Floorplanning Optimization with Trajectory Piecewise-Linear Model for Pipelined Interconnects

Interconnect pipelining has a great impact on system performance, but has not been considered by automatic floorplanning. Considering interconnect pipelining, we study the floorplanning optimization problem to minimize system CPI (cycles per instruction) and in turn maximize system performance. We develop an efficient tablebased model called trajectory piece-wise linear (TPWL) model to estimate CPI with interconnect pipelining. Experiments show that the TPWL model differs from cycle-accurate simulations by less than 3.0%. We integrate this model with a simulated-annealing based floorplan optimization to obtain CPI-aware floorplanning. Compared to the conventional floorplanning to minimize area and wire length, our CPI-aware floorplanning can reduce CPI by up to 28.6% with a small area overhead of 5.69% under 100nm technology and obtain better results under 70nm technology. To the best of our knowledge, this paper is the first in-depth study on floorplanning optimization with consideration of interconnect pipelining

Simulating the Impacts of an Upstream Dam on Pollutant Transport: A Case Study on the Xiangjiang River, China

Water pollution incidents can cause rapid deterioration of water quality, potentially leading to the illness and death of surrounding residents. Therefore, it is imperative to assess the impact of water pollution incidents, and to understand the mechanisms of pollutant transport and transformation. To address this problem, this paper constructed a hydraulic water quality model for the lower reaches of the Xiangjiang River, China, using the hydrodynamic module and convective diffusion module of MIKE21. Six pollution incident scenarios were simulated to investigate the transport process of pollutants, as affected by an upstream dam structure, the Changsha Comprehensive Control Project dam (CCCP). Analysis of the results suggests that the CCCP plays an essential role in controlling the transport and transformation of pollutants. With the CCCP, the process of transport is weakened, and the dispersion effect is strengthened. In particular, after the construction of the CCCP, the same amount of upstream discharge leads to lower peak pollutant concentrations and longer pollutant arrival times to each waterworks’ intake, thereby alleviating the impact of water pollution incidents. Further, comparative analysis suggests that the role of CCCP is much more significant with lower discharges (e.g., during the dry season), largely due to the higher amount of water quantity within the reach

Power-Efficient Pulse Width Modulation DC/DC Converters with Zero Voltage Switching Control

This paper proposes a power-efficient PWM DC/DC converter design with a novel zero voltage switching (ZVS) control technique. The ZVS control is realized by an inner feedback loop which is implemented by simple digital circuitry between the input and output of the power transistors and achieves real-time zero voltage switching (ZVS) for various loading and device parameters with power efficiencies over 90.0%. In addition, an outer feedback loop is used to ensure that the output precisely tracks a reference voltage level. We have also built the relationship between the output voltage ripple and the speed of the voltage comparators which has shown to introduce new low-frequency signals to the loops and cause significant output voltage ripples. Experiment results show that the output ripple could be reduced by 4x by carefully handling the generation and propagation of these low frequency signals

An experimental study of changes of beach profile and mean grain size caused by tsunami-like waves

Devastating tsunami waves can mobilize a substantial amount of coastal sediments and change the coastal morphology considerably. In this study, laboratory experiments were performed in a wave flume to investigate the changes of beach profile and mean grain size caused by tsunami-like waves that have a front similar to that of a solitary wave and an undulating tail following the wave front. A composite slope was constructed using a mixture of two sizes of sand. In addition to recording the wave rush-up and rush-down processes using video cameras, measurements were also made on water surface elevation, bed profile and the final size distribution of the sand mixture for three water depths. The results showed that sand suspension and erosion were caused mainly by sheet flows when water retreats from the beach, whereas the offshore sandbars, composed mainly of coarser sand, formed mainly from the run-down jumps caused by the collapsing of retreating water with waves in the undulating tail. The findings of this study have the potential to assist researchers in understanding nearshore tsunami flows from tsunami deposits