502 research outputs found
MF-NeRF: Memory Efficient NeRF with Mixed-Feature Hash Table
Neural radiance field (NeRF) has shown remarkable performance in generating
photo-realistic novel views. Among recent NeRF related research, the approaches
that involve the utilization of explicit structures like grids to manage
features achieve exceptionally fast training by reducing the complexity of
multilayer perceptron (MLP) networks. However, storing features in dense grids
demands a substantial amount of memory space, resulting in a notable memory
bottleneck within computer system. Consequently, it leads to a significant
increase in training times without prior hyper-parameter tuning. To address
this issue, in this work, we are the first to propose MF-NeRF, a
memory-efficient NeRF framework that employs a Mixed-Feature hash table to
improve memory efficiency and reduce training time while maintaining
reconstruction quality. Specifically, we first design a mixed-feature hash
encoding to adaptively mix part of multi-level feature grids and map it to a
single hash table. Following that, in order to obtain the correct index of a
grid point, we further develop an index transformation method that transforms
indices of an arbitrary level grid to those of a canonical grid. Extensive
experiments benchmarking with state-of-the-art Instant-NGP, TensoRF, and DVGO,
indicate our MF-NeRF could achieve the fastest training time on the same GPU
hardware with similar or even higher reconstruction quality
An Improved Global Harmony Search Algorithm for the Identification of Nonlinear Discrete-Time Systems Based on Volterra Filter Modeling
This paper describes an improved global harmony search (IGHS) algorithm for identifying the nonlinear discrete-time systems based on second-order Volterra model. The IGHS is an improved version of the novel global harmony search (NGHS) algorithm, and it makes two significant improvements on the NGHS. First, the genetic mutation operation is modified by combining normal distribution and Cauchy distribution, which enables the IGHS to fully explore and exploit the solution space. Second, an opposition-based learning (OBL) is introduced and modified to improve the quality of harmony vectors. The IGHS algorithm is implemented on two numerical examples, and they are nonlinear discrete-time rational system and the real heat exchanger, respectively. The results of the IGHS are compared with those of the other three methods, and it has been verified to be more effective than the other three methods on solving the above two problems with different input signals and system memory sizes
Beyond Not-Forgetting: Continual Learning with Backward Knowledge Transfer
By learning a sequence of tasks continually, an agent in continual learning
(CL) can improve the learning performance of both a new task and `old' tasks by
leveraging the forward knowledge transfer and the backward knowledge transfer,
respectively. However, most existing CL methods focus on addressing
catastrophic forgetting in neural networks by minimizing the modification of
the learnt model for old tasks. This inevitably limits the backward knowledge
transfer from the new task to the old tasks, because judicious model updates
could possibly improve the learning performance of the old tasks as well. To
tackle this problem, we first theoretically analyze the conditions under which
updating the learnt model of old tasks could be beneficial for CL and also lead
to backward knowledge transfer, based on the gradient projection onto the input
subspaces of old tasks. Building on the theoretical analysis, we next develop a
ContinUal learning method with Backward knowlEdge tRansfer (CUBER), for a fixed
capacity neural network without data replay. In particular, CUBER first
characterizes the task correlation to identify the positively correlated old
tasks in a layer-wise manner, and then selectively modifies the learnt model of
the old tasks when learning the new task. Experimental studies show that CUBER
can even achieve positive backward knowledge transfer on several existing CL
benchmarks for the first time without data replay, where the related baselines
still suffer from catastrophic forgetting (negative backward knowledge
transfer). The superior performance of CUBER on the backward knowledge transfer
also leads to higher accuracy accordingly.Comment: Published as a conference paper at NeurIPS 202
Addressless: A New Internet Server Model to Prevent Network Scanning
Eliminating unnecessary exposure is a principle of server security. The huge
IPv6 address space enhances security by making scanning infeasible, however,
with recent advances of IPv6 scanning technologies, network scanning is again
threatening server security. In this paper, we propose a new model named
addressless server, which separates the server into an entrance module and a
main service module, and assigns an IPv6 prefix instead of an IPv6 address to
the main service module. The entrance module generates a legitimate IPv6
address under this prefix by encrypting the client address, so that the client
can access the main server on a destination address that is different in each
connection. In this way, the model provides isolation to the main server,
prevents network scanning, and minimizes exposure. Moreover it provides a novel
framework that supports flexible load balancing, high-availability, and other
desirable features. The model is simple and does not require any modification
to the client or the network. We implement a prototype and experiments show
that our model can prevent the main server from being scanned at a slight
performance cost
The intestinal γδ T cells: functions in the gut and in the distant organs
Located in the frontline against the largest population of microbiota, the intestinal mucosa of mammals has evolved to become an effective immune system. γδ T cells, a unique T cell subpopulation, are rare in circulation blood and lymphoid tissues, but rich in the intestinal mucosa, particularly in the epithelium. Via rapid production of cytokines and growth factors, intestinal γδ T cells are key contributors to epithelial homeostasis and immune surveillance of infection. Intriguingly, recent studies have revealed that the intestinal γδ T cells may play novel exciting functions ranging from epithelial plasticity and remodeling in response to carbohydrate diets to the recovery of ischemic stroke. In this review article, we update regulatory molecules newly defined in lymphopoiesis of the intestinal γδ T cells and their novel functions locally in the intestinal mucosa, such as epithelial remodeling, and distantly in pathological setting, e.g., ischemic brain injury repair, psychosocial stress responses, and fracture repair. The challenges and potential revenues in intestinal γδ T cell studies are discussed
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