Table Occupancy Research Articles

The value of social distancing: A discrete choice experiment to examine golf tourists’ preferences for COVID-19 Safety protocols

This study investigates golf tourists’ preferences for diverse social distancing measures implemented by golf courses during the COVID-19 pandemic using a discrete choice experiment. With a sample of 430 South Korean golfers, this study provides a better understanding of how gender affects their trade-offs among several precautionary policies. Results suggest the maximum occupancy of each restaurant table is considered a critical factor in reducing infection risk, while golfers are willing to pay KR₩10,747 for a one-person reduction in table occupancy. Gender groups reveal different preference patterns regarding several safety measures. Female golfers show a higher willingness to pay for several preventive measures, particularly restaurant occupancy limits and locker spacing. These findings provide insights for golf course managers to develop targeted strategies that enhance customer safety and satisfaction during future health crises.

Digital Twins in Healthcare: an architectural proposal and its application in a social distancing case study.

The digital transformation process fostered by the development of Industry 4.0 technologies has largely affected the health sector, increasing diagnostic capabilities and improving drug effectiveness and treatment delivery. The Digital Twin (DT) technology, based on the virtualization of physical assets/processes and on a bidirectional communication between the digital and physical space for data exchange, is considered a game changer in modern health systems. Digital Twin applications in healthcare are various, ranging from virtualization of hospitals' physical spaces/organizational processes to individuals' physiological/genetic/lifestyle characteristics replication, and include the modeling of public health-related processes for monitoring, optimization and planning purposes. In this paper, motivated by the current COVID-19 pandemic, we focus on the application of the Digital Twin technology for virus containment on the workplace through social distancing. The contribution of this paper is three-fold: i) we review the existing literature on the adoption of the Digital Twin technology in the healthcare domain, and propose a classification of DT applications into four categories; ii) we propose a generalized Digital Twin architecture that can be used as reference to identify the main functional components of a Digital Twin system; iii) we present CanTwin, a real-life industrial case study developed by Hitachi and representing the Digital Twin of a canteen service serving 1100 workers, set up for social distancing monitoring, queue inspection, people counting and tracking, table occupancy supervision.

Correlation of room acoustic parameters and noise level in eating establishments

This article addresses the impact of the occupancy level, the average acoustic absorption and the so-called acoustic capacity of a space, which is proportional with the volume and inversely proportional with the reverberation time, on the behavior of talking people in an eating establishments. Four different settings were compared: two casual dining restaurants, a self-service student canteen and a small faculty club. The Lombard effect was observed in all cases. In a restaurant with an average amount of absorbing surface of 2.4 m2 or more per person, the sound pressure level increased with more than 3 dB per doubling of the number of people. Results for the student canteen show that people started to communicate less when the number of people present was so high that the absorbing surface dropped under 1.5 m2/person (80 people). The level even stopped to increase with increasing occupancy from 150 people present and beyond, corresponding with 0.8 m2 of absorbing surface per person. This is roughly consistent with an estimated value for the acoustic capacity of that space, which was 189 people (corresponding with a table occupancy of about 72%). In the latter circumstances, the background noise level, as expressed by LA,95 was as high as 69 dB. Overcoming this level for oral communication would require a not sustainable vocal effort. In the tests performed in other restaurants, the observed occupancy was below 60%, which, thanks to the higher number of absorbing surfaces in those restaurants, was well below the acoustic capacity.

A restaurant process with cocktail bar and relations to the three-parameter Mittag–Leffler distribution

AbstractIn addition to the features of the two-parameter Chinese restaurant process (CRP), the restaurant under consideration has a cocktail bar and hence allows for a wider range of (bar and table) occupancy mechanisms. The model depends on three real parameters, $\alpha$ , $\theta_1$ , and $\theta_2$ , fulfilling certain conditions. Results known for the two-parameter CRP are carried over to this model. We study the number of customers at the cocktail bar, the number of customers at each table, and the number of occupied tables after n customers have entered the restaurant. For $\alpha>0$ the number of occupied tables, properly scaled, is asymptotically three-parameter Mittag–Leffler distributed as n tends to infinity. We provide representations for the two- and three-parameter Mittag–Leffler distribution leading to efficient random number generators for these distributions. The proofs draw heavily from methods known for exchangeable random partitions, martingale methods known for generalized Pólya urns, and results known for the two-parameter CRP.

HybridFlow: Achieving Load Balancing in Software-Defined WANs With Scalable Routing

The scalability issue hinders the deployment of Software-Defined Networking (SDN) in the Wide Area Networks (WANs). Existing solutions have two issues: (1) network performance relies on complicated controller synchronization, which increases the complexity of network control; (2) fine-grained flow processing enables flexible flow control at the cost of high processing load on the controllers and high flow table occupancy on switches. In this paper, we propose a scalable routing solution named HybridFlow, which achieves a good load balancing performance using a single controller with low control overhead (i.e., flow routing and rerouting overhead). HybridFlow mainly employs two techniques: hybrid routing and crucial flow rerouting. Hybrid routing enabled by commercial SDN switches gives us opportunities to reduce the processing load of the controller by routing flows with the hybrid OpenFlow/OSPF mode. Thus, the majority of flows can be routed by OSPF without involving the controller. Crucial flow rerouting realizes load balancing by dynamically identifying crucial flows based on a new metric called Variation Slope and rerouting these flows with the hybrid OpenFlow/OSPF mode. The simulation based on the real traffic traces and network typologies shows that compared with the optimal solution, HybridFlow can achieve 87% of the optimal load balancing performance by rerouting 36% less flows on average.

Dynamic adjustment for proactive flow installation mechanism in SDN-based IoT

To satisfy various network requirements in the Internet of Things (IoT), software-defined networking (SDN) is viewed as an indispensable technology. Given the flow table resources in switches are limited, we proposed the periodic subflow-based proactive flow installation mechanism (PSPFIM) in our previous work. By separating subflows, PSPFIM can accurately detect the transmission periods and preinstall flow entry into switches before the transmissions arrive to reduce flow table occupancy. PSPFIM, however, is dysfunctional if transmission periods are at the millisecond level or subflows cannot be separated. In this paper, we propose the dynamic adjustment for PFIM (DAPFIM). DAPFIM is more widely applicable because the enhanced detection algorithm is less affected by noises and can detect transmission periods at the millisecond level. Besides, the adjustment algorithm can correct the error between an expected transmission period and a real transmission period. Through simulations, DAPFIM can detect transmission periods that cannot be detected by PSPFIM and other related work. Besides, DAPFIM averagely reduces up to 78% flow entry duration compared to other related work by changing the unit of the idle timeout from seconds to milliseconds, which saves much more flow table resources in switches.

Network Function Offloading Through Classification of Elephant Flows

With the move from traditional hardware appliance based network functions to Network Function Virtualization, software development is decoupled from the hardware. However, as a network function is no longer optimized for hardware, beneficial features of networking hardware may not be used any more. Solutions such as SDN or NIC offloading aim to overcome this antipodes by integrating networking hardware into the packet processing pipelines. On the one hand, offloading traffic of network functions to hardware can increase throughput and reduce resource consumption. On the other hand, the number of parallel flows in a network can be very high, exhausting the capacity of the tables of the networking hardware and force the system to fall back to software processing. Fortunately, it is known that a large portion of the flows in the Internet are mice flows, whereas the majority of the traffic is constituted by elephant flows. If the elephant flows can be detected efficiently, the hardware tables can be used more efficiently as a larger share of the traffic can be offloaded. We introduce a machine learning based approach that takes its decision with the first packet of a flow. A fundamentally different approach is using packet sampling for the offloading decision. We are evaluating both approaches in terms of complexity, offloaded share of the traffic and table occupation. The results show that a machine learning based offloading decision is possible with the first packet. The sampling approach only reaches a comparable performance at very high sampling rates.

Assessing the ease of conversation in multi-group conversation spaces: Effect of background music volume on acoustic comfort in a café

A “multi-group conversation space” refers to a space, such as restaurant or café, where more than one group of people share a space and make conversation within their respective group. From a field experiment in an actual café, we investigated the acoustic comfort in a multi-group conversation space considering speech intelligibility and speech privacy as major factors. In the experiment, noise measurements and a questionnaire survey taken by customers were conducted for 4 days. We were able to change the volume of the background music during operating hours, setting the level on each of the 4 days to low, mid, high, and none. Indoor noise levels were measured at six representative points with six sound level meters hung from the ceiling. The questionnaire consisted of eight items for subjective evaluation, including ease of conversation, comfort, and room atmosphere. After having their meal or drinks, the customers were asked to fill in the questionnaire at their table. The occupancy of neighboring tables and the number of customers in the café were also recorded. Results show that (1) overall, the respondents evaluated the café space positively; (2) high background music volume levels together with occupied neighboring tables tended to elicit negative evaluations; and (3) customer clustering analysis identified certain influences of distance from loudspeakers, neighboring table occupancy, and personal characteristics.

Load-Aware and Mobility-Aware Flow Rules Management in Software Defined Vehicular Access Networks

To ensure high performance for vehicular access networks, Software Defined Networking (SDN) technology is an efficient solution offering programmability, flexibility and a centralized view of the network. Nevertheless, to guarantee an efficient mobility management, some improvements are needed. In particular, a limitation on the number of exchanges between SDN controller and network devices and a better flow tables’ management are required. To achieve that, the ideas of flow rules’ pre-deployment and mobility-aware management of flow rules’ lifetime have been proposed. However, existing approaches have two major limitations: accuracy and adaptability. Indeed, network load (accuracy) and network devices’ feedbacks (adaptability) are not considered, two factors impacting flow rules management. That is why, in this paper, we define a state-based approach using connection/disconnection information reported by network devices to improve adaptability. Moreover, we propose a mobility-aware and load-aware flow rules management to improve accuracy. Finally, we specify a new flow rules’ pre-deployment policy based on flow tables occupancy rate, vehicles mobility and SDN control channel load. The evaluations carried out confirm the benefits of the approach, compared to existing solutions, both in terms of recovery delay, control overhead, hard timeout calculation and flow table occupancy.

Delayed Installation and Expedited Eviction: An Alternative Approach to Reduce Flow Table Occupancy in SDN Switches

Limited flow table size in switches is a major concern for SDN applications. The common approach to overcome this problem is to identify elephant flows and solely focus on them. However, there is no gold standard to assess the effectiveness of such greedy solutions. In this paper, we formally define this problem by choosing a cost function ( hit ratio ) and an objective function to optimize the ( average table occupancy ) and present the optimum solution (i.e., theoretical gold standard) for it. We model the problem as a knapsack problem, analyze how its solution minimizes the table occupancy, and the similarities to and differences from the default idle timeout mechanism used in OpenFlow. We also present a new approach to minimize flow table occupancy based on the insight gained from the knapsack model analysis. Our solution expedites rule evictions by forecasting the TCP flow termination from RST/FIN packets and delays rule installation by incubating non-TCP flows. It reduces average flow table occupancy between 16%–62% in various networks with less than 1.5% reduction in hit ratio. Using three real-world packet traces, we compare the performance of our solution with the theoretically optimum solution, the static idle timeout approach used in current OpenFlow systems, and heavy hitter detection approaches that are commonly used to solve this problem. We provide in-depth analysis of when and where our approach outperforms other solutions, while discussing why it might be better to use rate-based heavy hitter detection in some scenarios.

Balancing flow table occupancy and link utilization in software-defined networks

Software-Defined Networking (SDN) employs a centralized control with a global network view and provides great opportunities to improve network performance. However, due to the limitation of flow-table space at the switches and unbalanced traffic allocation on links, an SDN may suffer from flow-table overflow and inefficient bandwidth allocation among flows, increasing the controller’s burden and degrading network performance. In this paper, we present a dynamic routing scheme named DIFF that differentiates flows based on their impact on network resource and adaptively selects routing paths for them to mitigate the problems of flow-table overflow and inefficient bandwidth allocation. DIFF pre-generates a set of paths for each pair of source–destination edge switches and intelligently selects the paths from the pre-generated path-sets for new flows with an objective to balance flow-table utilizations. It adaptively reroutes some elephant flows to achieve maximum throughput under the rule of max–min fair bandwidth allocation. Simulation results show that DIFF simultaneously balances the flow-table and link utilizations, reduces the controller’s workload and packet delay, while increasing network throughput, compared with baseline schemes.

Implications of the link between the Periodic Table and the Standard Model

The mathematics of quantum physics from the standard model using groups U(1)xSU(2)xSU(3) and the Pauli principle produces two sets of time independent quantum states n(n+1) and n(n-1) where n is the principal quantum number. Oscillations between these states result in a one to one mapping with the Roberts-Janet Nuclear Periodic Table by interpretation of n>0 for condensed matter and n<0 for plasma prior to fusion. The mechanism provides a framework for Periodic Tables for every supernova by excluding mass number. In the lower half of the table occupation by bosons leads to increased energy densities in which an ensemble of outcomes is discussed. An hypothesis of string theory is proposed at the nuclear end of the table merging into quantum loop gravity at the condensed matter at the top end of the table.

Implications of the Link between the Periodic Table and the Standard Model

The mathematics of quantum physics from the standard model using groups U(1)xSU(2)xSU(3) and the Pauli principle produces two sets of time independent quantum states n(n+1) and n(n-1) where n is the principal quantum number. Oscillations between these states result in a one to one mapping with the Roberts-Janet Nuclear Periodic Table by interpretation of n>0 for condensed matter and n<0 for plasma prior to fusion. The mechanism provides a framework for Periodic Tables for every supernova by excluding mass number. In the lower half of the table occupation by bosons leads to increased energy densities in which an ensemble of outcomes is discussed. An hypothesis of string theory is proposed at the nuclear end of the table merging into quantum loop gravity at the condensed matter at the top end of the table.

Analytical Model for SDN Signaling Traffic and Flow Table Occupancy and Its Application for Various Types of Traffic

Software defined networking (SDN) has emerged as a promising networking paradigm overcoming various drawbacks of current communication networks.The control and data plane of switching devices is decoupled and control functions are centralized at the network controller. In SDN, each new flow introduces additional signaling traffic between the switch and the controller. Based on this traffic, rules are created in the flow table of the switch, which specify the forwarding behavior. To avoid table overflows, unused entries are removed after a predefined time-out period. Given a specific traffic mix, the choice of this time-out period affects the tradeoff between signaling rate and table occupancy . As a result, network operators have to adjust this parameter to enable a smooth and efficient network operation. Due to the complexity of this problem caused by the various traffic flows in a network, a suitable abstraction is necessary in order to derive valid parameter values in time. The contribution of this paper is threefold. First, we formulate a simple analytical model that allows optimizing the network performance with respect to the table occupancy and the signaling rate. Second, we validate the model by means of simulation. Third, we illustrate the impact of the time-out period on the signaling traffic and the flow table occupancy for different data-plane traffic mixes and characteristics. This includes scenarios with single application instances, as well as multiple application instances of different application types in an SDN-enabled network.

Using Service Blueprinting to Analyze Restaurant Service Efficiency

A time and motion study of 152 transactions at six restaurants operated by a full-service casual chain in Florida illustrates the use of service blueprinting as a method for analyzing service process efficiency. At management’s request, the researchers conducted the time and motion study to observe the extent to which individual servers followed company-mandated policies and procedures, and how well those procedures worked. Although this is a case study only and the observations cannot be generalized, the researchers noted a mixed picture with regard to policy observance and service efficiency. The restaurant chain uses a wine presentation process as a suggestive selling technique on greeting guests, but in this study the wine presentation resulted in a smaller than anticipated number of glasses sold. Moreover, unlike most suggestive selling, the wine presentation was a separate process that did not mesh with the meal order and delivery. In addition, rather than follow policy and drop checks when they check back on entrées, servers were waiting until the end of the meal to present the check, often when guests requested it. This policy omission may have added time to the table occupancy and reduced table turns. One procedure that was regularly observed—and worked successfully—was the “food ready” policy, in which any server would carry food to any table when that food was ready (instead of having the food stand until the “official” server could get it). These examples demonstrate how a comparison of actual performance to the service blueprint can show areas of inefficiency, both in terms of failure to follow policy and in terms of policies that are not as effective as expected.

Sequential dynamic gadolinium magnetic resonance perfusion-weighted imaging: effects on transit time and cerebral blood volume measurements

To evaluate if two gadolinium perfusion studies can be performed during the same table occupancy without degradation of the derived data in the second study. Magnetic resonance (MR) perfusion studies of the whole brain were performed on 12 patients during the administration of two gadolinium boluses separated by 8 min. In six patients, gadolinium was given as two 20-ml administrations of standard 0.5 M chelate (Magnevist), whilst the other six patients received two 10-ml administrations of 1.0 M chelate (Gadovist). There were no significant differences in subjective quality between the time-intensity curves of the first and second perfusion studies using either the 0.5 M or 1.0 M gadolinium chelate. The objective measurements in quality of the time-intensity curves (maximum signal change and full width at half maximum) changed by less than 5% of the original values on the second perfusion study. The first-moment mean transit times did not change significantly on the sequential studies. The regional cerebral blood volume tended to increase on the second study (by 15% on average), but this did not reach statistical significance. The results from two sequential dynamic gadolinium-based perfusion studies can be compared in a meaningful manner using the technique described.