Access Scheduling Research Articles

An Improved FCFS (IFCFS) Disk Scheduling Algorithm

the time movable head disk came into existence, the I/O performance has been improved by proper scheduling of disk accesses. Disk scheduling involves a careful examination of pending requests to determine the most efficient way to service the requests. The two most common types of scheduling are seek optimization and rotational (or latency) optimization. Most of the scheduling algorithms concentrate on reducing seek times for a set of requests, because seek times tend to be an order of magnitude greater than latency times. Some of the most important scheduling algorithms are First-Come-First-Served (FCFS), Shortest Seek Time First (SSTF), SCAN, Circular Scan (C-SCAN) and LOOK. FCFS is the simplest form of disk scheduling algorithm. This algorithm is simple to implement, but it generally does not provide the fastest service. This paper describes an improvement in FCFS. A simulator program has been designed and tested the improved FCFS. After improvement in FCFS it has been found that the service is fast and seek time has been reduced drastically.

ACHIEVE - active in children's health: integrating evidence, valuing experience

The article discusses a study to develop a comprehensive procedure for continued assessment of children aged between of 0-18 years with attention deficit hyperactivity disorder (ADHD). The authors have designed a pathway incorporating 6 key performance indicators (KPIs) including a standardized classroom observation schedule, structured and equitable training opportunities and access to paediatric and Child and Adolescent Mental Health Services (CAMHS) occupational therapy where appropriate.

Replication of Personal Contents Following a User with Personalized Access History and Schedule

The advent of ubiquitous computing environments enables users to access their digital contents when they want at any time once their devices are connected to the Internet. For efficient management of remote contents, we need a replication technique among servers. However, th existing approaches focus on shared contents using the access heuristics of groups of users. In this paper, we propose a personalized replication scheme especially for contents owned by one user. The proposed scheme selects target replication servers according to both the user’s past behavior and future movement plan. We periodically analyze each user’s access location in order to figure out where the user usually accesses contents. A user also can register his/her schedule information on personal or business trips to our system, which then expects that the user will be likely to access contents at a different location during the specified dates. With this simple reasoning, our replication scheme additionally replicates contents to another replication server near to the user’s destination. Simulations show that the proposed scheme reduces the expense of storage usage because we replicate contents only to selective servers, and it keeps content access time low because contents are accessed from nearby replication servers with high probability based on the user’s past and future location information. The proposed approach can be applied to distributed storage and personal content synchronization applications. Especially, it is appropriate to storage service for a photographer, who travels all over the world and deals with large amount of photograph data. As personal content management has been one of promising services in cloud computing systems, we expect that the proposed scheme also can be adopted in cloud computing nodes in order to efficiently manage contents as well.

A mean–variance model to optimize the fixed versus open appointment percentages in open access scheduling systems

Although healthcare quality may improve with short-notice scheduling and subsequently higher patient show-up rates, the variability in patient flow may negatively impact the service design. This study demonstrates how to select the percentage for short-notice or open appointments in an open access scheduling system subject to two quality performance metrics. Specifically, we develop a mean–variance model and an efficient solution procedure to help clinic administrators determine the open appointment percentage subject to increasing the average number of patients seen while also reducing the variability. Our numerical results indicate that for cases with high patient demand and high patient no-show rates for fixed appointments, one or more Pareto optimal percentages of open appointments significantly decrease the variability in the number of patients seen with only a negligible decrease in the expected number of patients seen. While our method provides a useful tool for clinic administrators, it also presents a modeling foundation for open access scheduling with quality management objectives to smooth patient flow and improve capacity utilization.

LAAP: A Learning Automata-based Adaptive Polling Scheme for Clustered Wireless Ad-Hoc Networks

In multi-hop ad hoc networks, besides collision-free transmissions, channel utilization should be also enhanced due to the scarce bandwidth. In this paper, we propose a learning automat-based adaptive polling scheme for medium access scheduling in clustered wireless ad-hoc networks to enhance the channel utilization. In this scheme, each cluster-head takes the responsibility of coordinating intra-cluster transmissions so that no collisions occur. Taking advantage of learning automaton, each cluster-head learns the traffic parameters of its own cluster members. Cluster members are prioritized based on these traffic parameters. Each cluster-head then takes the traffic parameters into consideration for finding an optimal channel access scheduling within its cluster. By the proposed polling scheme, each cluster member is assigned a portion of bandwidth proportional to its need (i.e., traffic load). The results show that the proposed channel assignment policy considerably improves the channel utilization. Simulation experiments also show the superiority of the proposed polling-based medium access scheme over the existing methods in terms of channel utilization, waiting time for packet transmission, and control overhead.

Multiple subtypes of opioid receptors regulate binge‐like (BE) feeding in rodents on an intermittent access schedule

Binge eating disorder (BED) affects approximately 3% of adults in the USA and is characterized by repeated episodes of eating unusually large amounts of food in a short period of time without engaging in compensatory behaviors. Interestingly, a significant comorbidity with substance abuse exists in patients with BED. Opioid peptides are known to regulate appetitive behavior. Moreover, opioid receptor antagonists (OpRA) are used clinically in the treatment of alcohol and substance abuse. In both rats and mice, the pan OpRA LY255582 was effective in reducing BE at doses that did not affect control 24 hour intake. In rats, similar reductions in BE were observed using the mu and delta selective OpRAs LY2491481 and naltriben, respectively. The kappa selective OpRA LY2444296 was ineffective in reducing BE in rats. In order to confirm our pharmacology findings using genetic models, we evaluated BE in OpR knockout mice using a similar intermittent access paradigm. Unlike our antagonist studies, no differences in BE were observed in either the mu or delta receptor mutants compared to wildtypes. Interestingly, spontaneous free access feeding and BE were increased in the kappa receptor specific and mu‐delta‐kappa combinatorial mutants in comparison to wildtypes. Our data support that endogenous opioids modulate BE in a complex manner in rodents.

A New TDMA Scheduling Algorithm for Data Collection over Tree-Based Routing in Wireless Sensor Networks

Data collection is one of the most important tasks in Wireless Sensor Networks (WSNs) where a set of sensors measure properties of a phenomenon of interest and send their data to the sink. Minimizing the delay of the data collection is important for applications in which certain actions based on deadline are needed, such as event-based and mission-critical applications. Time Division Multiple Access (TDMA) scheduling algorithms are widely used for quick delivery of data with the objective of minimizing the time duration of delivering data to the sink, that is, minimizing the delay. In this paper, we propose a new centralized TDMA scheduling algorithm that is based on nodes congestion for general ad hoc networks. In the proposed algorithm, the scheduling is obtained using colouring of the original network. Colouring the original network is accomplished based on congestion degree of nodes. The simulation results indicate that the performance of our algorithm is better than that of node-based and level-based scheduling algorithms. We will also show that the performance of our proposed algorithm depends on the distribution of the nodes across the network.

Intimate partner violence: patients' experiences and perceptions in family practice

To understand how women affected by intimate partner violence (IPV), felt their family physicians cared for them and to identify where gaps in care exist. Interviews were conducted with ten women (mean age 50 years and minimum to maximum ages of 40-73 years). Content analysis was used to identify common themes. Women acknowledged a lack of insight into their abusive relationships given a lack of physical violence, preconceptions about IPV or presumed reasons their abusers had for violence. After identifying abuse, most shared feelings of fear, preventing them from disclosure. They feared being judged, not believed and consequences from their abuser. Perceptions' about their family physician's role prevented disclosure particularly misconceptions regarding physician's interest and time to discuss non-medical issues. After disclosure, women valued their family physicians listening, following up, providing validation and advocacy. All women experienced isolation secondary to the abuser, the family practice clinic, the physician and/or the 'system' itself. Women were not aware of family doctors' interest in issues aside from physical health. They appreciated a confidential and non-threatening environment and valued follow-up and advocacy on their behalf. They expressed frustration with open access scheduling and multiple providers. To improve care, family physicians should educate patients about their role, provide safe environments for disclosure and offer follow-up and support. Recommended system changes include measures to ensure continuity of care and easy booking of appointments. Finally, family physicians should recognize that there is a need to follow these patients long term as the effects of IPV are long lasting.

Access Time Analysis for IEEE P1687

The IEEE P1687 (IJTAG) standard proposal aims at providing a standardized interface between the IEEE Standard 1149.1 test access port (TAP) and on-chip embedded test, debug and monitoring logic (instruments), such as scan chains and temperature sensors. A key feature in P1687 is to include Segment Insertion Bits (SIBs) in the scan path to allow flexibility both in designing the instrument access network and in scheduling the access to instruments. This paper presents algorithms to compute the overall access time (OAT) for a given P1687 network. The algorithms are based on analysis for flat and hierarchical network architectures, considering two access schedules, i.e., concurrent schedule and sequential schedule. In the analysis, two types of overhead are identified, i.e., network configuration data overhead and JTAG protocol overhead. The algorithms are implemented and employed in a parametric analysis and in experiments on realistic industrial designs.

Utility maximisation in channel-aware and queue-aware orthogonal frequency division multiple access scheduling based on arrival rate control

A channel-aware and queue-aware (CAQA) scheduling scheme is proposed for the downlink of orthogonal frequency division multiple access (OFDMA) networks. The scheduling scheme cooperates with a rate control policy, which controls arrival rates to the base station queues. The network resource allocation is formulated as a utility maximisation problem, which is decomposed into a CAQA OFDMA scheduling problem and a rate control problem. The authors decompose the scheduling problem into subproblems of rate allocation to subcarriers and propose a joint subcarrier assignment and rate allocation (JSARA) solution for the problem. Simulation is conducted to evaluate the performance of JSARA in terms of throughput, queue length and dropping probability. In addition, JSARA performance gain in allocating users’ arrival rates and achieved aggregate utility, in cooperation with a rate control policy, is investigated.

Scheduling methods for multi-user optical wireless asymmetrically-clipped OFDM

Diffuse optical wireless (DOW) systems have the advantage that they do not require point-to-point siting so one transmitter can communicate with several receivers. In this paper, we investigate multiple access scheduling methods for downlink orthogonal frequency division multiplexing (OFDM) in diffuse optical wire- less networks. Unlike the radio frequency (RF) channel, the DOW channel has low-pass filter characteristics and so requires different scheduling methods than those developed for the RF channel. Multi-user diversity orthogonal frequency division multiple access (OFDMA) systems nominate a cluster of subcarriers with the largest signal-to-noise-ratio for transmission. However, in a DOW channel, most users would choose the lowest frequency clusters of subcarriers. To remedy this problem, we make two proposals. The first is to use a variable cluster size across the subcarriers; the lower frequency clusters will have fewer subcarriers while the higher frequency clusters will have more subcarriers. This will equalize the capacity of the clusters. The second proposal is to randomize a user's cluster selection from a group of clusters satisfying a minimum threshold. Through simulation it is shown that combining these strategies can increase the throughput while ensuring a fair distribution of the available spectrum.

Memory access schedule minimization for embedded systems

The growing gap between microprocessor speed and DRAM speed is a major problem that computer designers are facing. In order to narrow the gap, it is necessary to improve DRAM's speed and throughput. To achieve this goal, this paper proposes techniques to take advantage of the characteristics of the 3-stage access of contemporary DRAM chips by grouping the accesses of the same row together and interleaving the execution of memory accesses from different banks. A family of Bubble Filling Scheduling (BFS) algorithms are proposed in this paper to minimize memory access schedule length and improve memory access time for embedded systems. When the memory access trace is known in some application-specific embedded systems, this information can be fully utilized to generate efficient memory access schedules. The offline BFS algorithm can generate schedules which are 47.49% shorter than in-order scheduling and 8.51% shorter than existing burst scheduling on average. When memory accesses are received by the single memory controller in real time, the memory accesses have to be scheduled as they come. The online BFS algorithm in this paper serves this purpose and generates schedules which are 58.47% shorter than in-order scheduling and 4.73% shorter than burst scheduling on average. To improve the memory throughput and further reduce the memory access schedule, an architecture with dual memory controllers is proposed. According to the experimental results, the dual controller algorithm can generate schedules which are 62.89% shorter than in-order scheduling, 14.23% shorter than burst scheduling, and 10.07% shorter than single controller BFS algorithms on average.

NPY receptor subtype specification for behavioral adaptive strategies during limited food access

The neuropeptide Y (NPY) system in the brain regulates a wide variety of behavioral, metabolic and hormonal homeostatic processes required for energy balance control. During times of limited food availability, NPY promotes behavioral hyperactivity necessary to explore and prepare for novel food resources. As NPY can act via 5 different receptor subtypes, we investigated the path through which NPY affects different behavioral components relevant for adaptation to such conditions. We tested NPY Y1 and Y2 receptor knockout mice and their wild-type littermate controls in a daily scheduled limited food access paradigm with unlimited access to running wheel. Here we show that NPY Y1 receptor deficient mice lack the expression of appetitive behavior and that NPY Y2 receptors control the level of hyperactive behavior under these conditions. Thus, receptor specificity determines the differential expression of NPY-mediated behavioral adaptations to overcome a negative energy status.

Behavioral Traits Predicting Alcohol Drinking in Outbred Rats: An Investigation of Anxiety, Novelty Seeking, and Cognitive Flexibility

Most adults in Western society consume alcohol regularly without negative consequences. For a small subpopulation, however, drinking can quickly progress to excessive and chronic intake. Given the dangers associated with alcohol abuse, it is critical to identify traits that may place an individual at risk for developing these behaviors. To that end, we used a rat model to determine whether anxiety-related behaviors, novelty seeking, or cognitive flexibility predict excessive alcohol drinking under both limited and continuous access conditions. Adult male rats were assessed in a series of behavioral tasks (elevated plus maze [EPM], locomotor activity, and discrimination/reversal learning in a Y-maze) followed by 6 weeks of daily, 1-hour access to alcohol in a free-choice, 2-bottle paradigm (10% alcohol vs. tap water). Next, subjects were given the opportunity to consume alcohol for 72 hours in drinking chambers that permit separate measures of each drinking bout. Half of the animals experienced a 2-week deprivation period between the limited and continuous access sessions. Time spent on the open arms of the EPM, but not novelty seeking or discrimination/reversal learning, predicted alcohol consumption during limited, 1-h/d access sessions to alcohol. Anxiety-related behavior also predicted the escalation of intake when animals were given 72 hours of continuous access to alcohol. Bout size, but not frequency, was responsible for the increased consumption by high-anxiety subjects during this period. Finally, intake during limited access sessions predicted intake during continuous access, but only in subjects with low intake during limited access. These findings confirm that preexisting anxiety-related behavior predicts alcohol intake under several schedules of alcohol access. Moreover, when access is unlimited, the high-anxiety-related group exhibited an increase in bout size, but not frequency, of drinking. In addition, we show that modest intake when alcohol is restricted may or may not progress to excessive intake when the drug is freely available.

Sucrose modifies c-fos mRNA expression in the brain of rats maintained on feeding schedules

Food intake is regulated according to circadian activity, metabolic needs and the hedonic value of food. Rodents placed on a fixed feeding schedule show behavioral and physiological anticipation of mealtime referred to as food-anticipatory activity (FAA). FAA is driven by the food-entrainable oscillator (FEO), whose anatomical substrate is not yet known. Recent data have shown that restricted feeding schedules for regular chow and daily limited access to palatable food in free-feeding rats activate distinct brain regions during FAA. The combination of a deprivation regimen and scheduled access to palatable food may give rise to a more global anticipatory mechanism because the temporal cycles of energy balance would be strongly modulated by the incentive properties of palatable food; however, the neuronal response to this combined treatment is not yet known. The present study investigated how adding palatable sucrose to feeding schedules affects the pattern of brain c-fos mRNA expression during FAA (0-3 h) and 1 h following feeding. The rats maintained on scheduled chow access increased their daily chow intake, while the rats maintained on scheduled sucrose and chow mainly increased their daily sucrose intake. Adding sucrose to scheduled feeding displaced c-fos mRNA expression from the dorsomedial and paraventricular hypothalamic nuclei and posterior lateral hypothalamus (LH) to the prefrontal cortex, lateral septum, nucleus accumbens and anterior LH. During refeeding, the rats on scheduled sucrose demonstrated higher activation of the nucleus of the solitary tract. The present results suggest that palatable sucrose combined with restricted feeding schedules activate a distinct neuronal network compared to neuronal activation produced by scheduled access to regular chow. These data provide evidence that the brain may contain different food-oscillatory systems and that food palatability may shift the neuronal activity from the medial hypothalamus to the limbic and reward-related areas even at the negative metabolic state.

Adaptive granularity memory systems

We propose adaptive granularity to combine the best of fine-grained and coarse-grained memory accesses. We augment virtual memory to allow each page to specify its preferred granularity of access based on spatial locality and error-tolerance tradeoffs. We use sector caches and sub-ranked memory systems to implement adaptive granularity. We also show how to incorporate adaptive granularity into memory access scheduling. We evaluate our architecture with and without ECC using memory intensive benchmarks from the SPEC, Olden, PARSEC, SPLASH2, and HPCS benchmark suites and micro-benchmarks. The evaluation shows that performance is improved by 61% without ECC and 44% with ECC in memory-intensive applications, while the reduction in memory power consumption (29% without ECC and 14% with ECC) and traffic (78% without ECC and 66% with ECC) is significant.

Scheduled meals and scheduled palatable snacks synchronize circadian rhythms: Consequences for ingestive behavior

Food is a potent time signal for the circadian system and has shown to entrain and override temporal signals transmitted by the biological clock, the suprachiasmatic nucleus, which adjusts mainly to the daily light/dark (LD) alternation. Organisms mostly ingest food in their active period and this permits a correct coordination between the LD and the food elicited time signals with the circadian system. Under conditions when feeding opportunities are shifted to the usual resting/sleep phase, the potent entraining force of food, shifts circadian fluctuations in several tissues, organs, and brain structures toward meal time, resulting a desynchrony within the body and between the organism and the external LD cycle. The daily scheduled access to a palatable snack exerts similar changes specifically to brain areas involved in motivation and reward responses. This review describes the phenomenology of food entrainment and entrainment by a palatable snack. It suggests how scheduled feeding can lead to food addiction and how shifted feeding schedules toward the sleep phase can result in altered ingestive behavior, obesity and disturbed metabolic responses.

Advanced Access Scheduling Outcomes

Advanced ("open") access scheduling, which promotes patient-driven scheduling in lieu of prearranged appointments, has been proposed as a more patient-centered appointment method and has been widely adopted throughout the United Kingdom, within the US Veterans Health Administration, and among US private practices. To describe patient and physician and/or practice outcomes resulting from implementation of advanced access scheduling in the primary care setting. Comprehensive search of electronic databases (MEDLINE, Scopus, Web of Science) through August, 2010, supplemented by reference lists and gray literature. Studies were assessed in duplicate, and reviewers were blinded to author, journal, and date of publication. Controlled and uncontrolled English-language studies of advanced access implementation in primary care were eligible if they specified methods and reported outcomes data. Two reviewers collaboratively assessed risk for bias by using the Cochrane Effective Practice and Organisation of Care Group Risk of Bias criteria. Data were independently extracted in duplicate. Twenty-eight articles describing 24 studies met eligibility criteria. All studies had at least 1 source of potential bias. All 8 studies evaluating time to third-next-available appointment showed reductions (range of decrease, 1.1-32 days), but only 2 achieved a third-next-available appointment in less than 48 hours (25%). No-show rates improved only in practices with baseline no-show rates higher than 15%. Effects on patient satisfaction were variable. Limited data addressed clinical outcomes and loss to follow-up. Studies of advanced access support benefits to wait time and no-show rate. However, effects on patient satisfaction were mixed, and data about clinical outcomes and loss to follow-up were lacking.

A Distributed and Scalable Time Slot Allocation Protocol for Wireless Sensor Networks

There are performance deficiencies that hamper the deployment of Wireless Sensor Networks (WSNs) in critical monitoring applications. Such applications are characterized by considerable network load generated as a result of sensing some characteristics of the monitored system. Excessive packet collisions lead to packet losses and retransmissions, resulting in significant overhead costs and latency. In order to address this issue, we introduce a distributed and scalable scheduling access scheme that mitigates high data loss in data-intensive sensor networks and can also handle some mobility. Our approach alleviates transmission collisions by employing virtual grids that adopt Latin Squares characteristics to time slot assignments. We show that our algorithm derives conflict-free time slot allocation schedules without incurring global overhead in scheduling. Furthermore, we verify the effectiveness of our protocol by simulation experiments. The results demonstrate that our technique can efficiently handle sensor mobility with acceptable data loss, low packet delay, and low overhead.

Distributed Dynamic Channel Access Scheduling Method for Wireless Ad Hoc Network

Distributed Dynamic Channel Access Scheduling Method for Wireless Ad Hoc Network