Closed-Loop MIMO-OFDM Wireless System Using Long-Term Pre-Weighting Scheme

Reverse logistics is a modern field of consideration, research and study, providing helpful information on the operation of the closed-loop supply chain. Although the starting point of this field is traced back to the early 90?s, no standard method has been suggested, neither prevailed. The purpose of this paper is to introduce a new approach on the study of reverse logistics. It is actually a review on how System Dynamics (SD) can be a helpful tool when it is used in the reverse logistics field. The paper explains the basic theory of the system modeling and next it utilizes the reverse logistics model. Finally, an illustrative example shows how SD modeling can be used to produce a powerful long-term decision-making tool.

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MIMO-OFDM AND SC-FDMA FOR LONG-TERM EVOLUTION

Communications ◽

10.2316/journal.214.2013.2.214-1063 ◽

2013 ◽

Vol 2 (2) ◽

Author(s):

Rahim Umar ◽

Haris Majeed ◽

Nayyer A. Zaidi

Keyword(s):

Long Term Evolution ◽

Term Evolution ◽

Mimo Ofdm

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Cognitive Issues in Virtual Reality

Virtual Environments and Advanced Interface Design ◽

10.1093/oso/9780195075557.003.0024 ◽

1995 ◽

Author(s):

Christopher D. Wickens ◽

Polly Baker

Keyword(s):

Virtual Reality ◽

Closed Loop ◽

Three Dimensional ◽

Open Loop ◽

Frame Of Reference ◽

Realistic View ◽

Static Images ◽

Sense Of Reality ◽

Inside Out

Virtual reality involves the creation of multisensory experience of an environment (its space and events) through artificial, electronic means; but that environment incorporates a sufficient number of features of the non-artificial world that it is experienced as “reality.” The cognitive issues of virtual reality are those that are involved in knowing and understanding about the virtual environment (cognitive: to perceive and to know). The knowledge we are concerned with in this chapter is both short term (Where am I in the environment? What do I see? Where do I go and how do I get there?), and long term (What can and do I learn about the environment as I see and explore it?). Given the recent interest in virtual reality as a concept (Rheingold, 1991; Wexelblat, 1993; Durlach and Mavor, 1994), it is important to consider that virtual reality is not, in fact, a unified thing, but can be broken down into a set of five features, any one of which can be present or absent to create a greater sense of reality. These features consist of the following five points. 1. Three-dimensional (perspective and/or stereoscopic) viewing vs. two-dimensional planar viewing. (Sedgwick, 1986; Wickens et al., 1989). Thus, the geography student who views a 3D representation of the environment has a more realistic view than one who views a 2D contour map. 2. Dynamic vs. static display. A video or movie is more real than a series of static images of the same material. 3. Closed-loop (interactive or learner-centered) vs. open-loop interaction. A more realistic closed-loop mode is one in which the learner has control over what aspect of the learning “world” is viewed or visited. That is, the learner is an active navigator as well as an observer. 4. Inside-out (ego-referenced) vs. outside-in (world-referenced) frame-of-reference. The more realistic inside-out frame-of-reference is one in which the image of the world on the display is viewed from the perspective of the point of ego-reference of the user (that point which is being manipulated by the control). This is often characterized as the property of “immersion.” Thus, the explorer of a virtual undersea environment will view that world from a perspective akin to that of a camera placed on the explorer’s head;

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Effect of Closed-Loop Vibration Stimulation on Heart Rhythm during Naps

Sensors ◽

10.3390/s19194136 ◽

2019 ◽

Vol 19 (19) ◽

pp. 4136 ◽

Cited By ~ 1

Author(s):

Sang Ho Choi ◽

Heenam Yoon ◽

Hyung Won Jin ◽

Hyun Bin Kwon ◽

Seong Min Oh ◽

...

Keyword(s):

High Frequency ◽

Closed Loop ◽

Low Frequency ◽

Heart Rhythm ◽

Quality Of Sleep ◽

Stimulation Condition ◽

Term Basis ◽

Stimulation System

Sleep plays a primary function for health and sustains physical and cognitive performance. Although various stimulation systems for enhancing sleep have been developed, they are difficult to use on a long-term basis. This paper proposes a novel stimulation system and confirms its feasibility for sleep. Specifically, in this study, a closed-loop vibration stimulation system that detects the heart rate (HR) and applies −n% stimulus beats per minute (BPM) computed on the basis of the previous 5 min of HR data was developed. Ten subjects participated in the evaluation experiment, in which they took a nap for approximately 90 min. The experiment comprised one baseline and three stimulation conditions. HR variability analysis showed that the normalized low frequency (LF) and LF/high frequency (HF) parameters significantly decreased compared to the baseline condition, while the normalized HF parameter significantly increased under the −3% stimulation condition. In addition, the HR density around the stimulus BPM significantly increased under the −3% stimulation condition. The results confirm that the proposed stimulation system could influence heart rhythm and stabilize the autonomic nervous system. This study thus provides a new stimulation approach to enhance the quality of sleep and has the potential for enhancing health levels through sleep manipulation.

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