Guaranteed Time Research Articles

Estimating ordered quantiles of two exponential populations with a common minimum guarantee time

The problem of estimating ordered quantiles of two exponential populations is considered, assuming equality of location parameters (minimum guarantee times), using the quadratic loss function. Under order restrictions, we propose new estimators which are the isotonized version of the MLEs, call it, restricted MLE. A sufficient condition for improving equivariant estimators is derived under order restrictions on the quantiles. Consequently, estimators improving upon the old estimators have been derived. A detailed numerical study has been done to evaluate the performance of proposed estimators using the Monte-Carlo simulation method and recommendations have been made for the use of the estimators.

Vertical integration maintenance commitments

To meet the maintenance of durable goods, it is considered that maintenance commitments have a significant impact on consuming decisions. To make this article more realistic, we are devoted to address maintenance commitments for goods with high expenditures to maintain under vertical integration structure. Establishing Principal-agent model of the guarantee time limited to maintain these special goods, this article argues the existence of optimal contract. In the light of the principal-agent model, the net profit of the higher efficiency maintainer is positive while the lower efficiency one attains zero profit. The vertical merger is also discussed in this work.

Resolving-Functions Method for Game Problems of Control with Integral Constraints

The method of resolving functions is investigated as applied to game problems of control with integral constraints. A scheme of the method is proposed that ensures the end of a game within a definite guaranteed time in the class of stroboscopic strategies. The results of comparison of the guaranteed times of this scheme of the resolving-functions method with those of the first direct Pontryagin method for integral constraints are shown.

Optimized Protocol of Multiple Post-Processing Techniques Improves Diagnostic Accuracy of Multi-Detector Computed Tomography for Assessing Small Bowel Obstruction Compared with Conventional Axial and Coronal Reformations

Background: To systemically evaluate the diagnostic accuracy and time efficiency of an optimized protocol of multiple post-processing techniques on multi-detector computed tomography (MDCT) used to small bowel obstruction (SBO) and secondary small bowel ischemia. Methods: A total of 106 adults with clinically suspected SBO were included in this institutional review board-approved retrospective study. Two abdominal radiologists performed image post-processing and interpretation for MDCT volume data of patients using three different post-processing protocols at intervals of every other month, respectively. With surgical and/or pathological findings as the gold standard, these protocols were compared regarding relevant time spend, number of images, diagnostic self-confidence, agreement, detection rate, accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of them used to assess SBO and secondary small bowel ischemia. Results: Time spend and number of images for protocol 2 were more than for protocols 1 and 3 (P .05). In the performance of protocol 3, both readers added multiple post-processing techniques at frequencies of 29.2% and 34.9% respectively for obstruction cause, and 32.1% and 30.2% respectively for secondary small bowel ischemia. For the total detection rate of obstruction cause and secondary small bowel ischemia, protocols 2 and 3 were higher (P = .001) than protocol 1, but no difference (P > .05) was detected between protocols 2 and 3. The accuracy, sensitivity, specificity, PPV and NPV of protocols 2 and 3 were superior to protocol 1 for evaluating obstruction cause and secondary small bowel ischemia. Conclusions: Optimized protocol of multiple post-processing techniques can both guarantee time efficiency and improve diagnostic accuracy of MDCT for assessing SBO and secondary small bowel ischemia. Funding: This work was supported in part by a research grant from the National Natural Science Foundation of China (81671943). The funder had no role in study design, data collection, data analysis, data interpretation, or the writing of the manuscript. Declaration of Interest: The authors have no financial conflicts to declare. Ethical Approval: This study was approved by the ethics committee of our hospital. A waiver of informed consent was obtained for this study.

Clear and Cloudy Exoplanet Forecasts for JWST: Maps, Retrieved Composition, and Constraints on Formation with MIRI and NIRCam

Abstract The James Webb Space Telescope (JWST) will measure exoplanet transmission and eclipse spectroscopy at unprecedented precisions to better understand planet structure, dynamics, chemistry, and formation. These are essential tools on the march toward biosignature searches on potentially habitable planets. We explore a range of exoplanet atmospheric conditions and forecast the expected results with JWST. We take realistic CHIMERA models that match existing Spitzer and Hubble Space Telescope results and simulate the spectra achievable with the JWST MIRI+NIRCam Guaranteed Time Observations survey, which includes observations of HD 189733 b, WASP-80 b, HAT-P-19 b, WASP-107 b, GJ 436 b, and HAT-P-26 b. We then retrieve atmospheric parameters from these spectra to estimate the precision to which the planets’ atmospheric compositions can be measured. We find that emission spectra have well-constrained unimodal solutions but transmission spectra near 10× solar abundance and solar C/O ratios can suffer from bimodal solutions. Broad wavelength coverage as well as higher-precision data can resolve bimodal solutions and provide dramatically better atmospheric parameter constraints. We find that metallicities can be measured to within 20%–170%, which approaches the precisions on solar system planets, and C/O ratios can be constrained to ∼10%–60%, assuming that observers can leverage short wavelength data to select the correct solution from the bimodal posteriors. These compositional precisions are sufficient to validate or refute predictions from disk formation models on final atmospheric abundances as long as their history is not erased by planet evolution processes. We also show the extent to which eclipse mapping with JWST is possible on our brightest system HD 189733 b.

The JWST Extragalactic Mock Catalog: Modeling Galaxy Populations from the UV through the Near-IR over 13 Billion Years of Cosmic History

We present an original phenomenological model to describe the evolution of galaxy number counts, morphologies, and spectral energy distributions across a wide range of redshifts (0.2<z<15) and stellar masses [Log10 M/Msun >6]. Our model follows observed mass and luminosity functions of both star-forming and quiescent galaxies, and reproduces the redshift evolution of colors, sizes, star-formation and chemical properties of the observed galaxy population. Unlike other existing approaches, our model includes a self-consistent treatment of stellar and photoionized gas emission and dust attenuation based on the BEAGLE tool. The mock galaxy catalogs generated with our new model can be used to simulate and optimize extragalactic surveys with future facilities such as the James Webb Space Telescope (JWST), and to enable critical assessments of analysis procedures, interpretation tools, and measurement systematics for both photometric and spectroscopic data. As a first application of this work, we make predictions for the upcoming JWST Advanced Deep Extragalactic Survey (JADES), a joint program of the JWST/NIRCam and NIRSpec Guaranteed Time Observations teams. We show that JADES will detect, with NIRCam imaging, thousands of galaxies at z>6, and tens at z>10 at m_AB<30 (5-sigma) within the 236 arcmin^2 of the survey. The JADES data will enable accurate constraints on the evolution of the UV luminosity function at z>8, and resolve the current debate about the rate of evolution of galaxies at z>8. Ready to use mock catalogs and software to generate new realizations are publicly available as the JAdes extraGalactic Ultradeep Artificial Realizations (JAGUAR) package.

Efficiency of a Two-Channel System with Restructuring and Insurance

We consider a system of two conditionally independent alternating renewal processes with restructuring and with a general form of the distribution densities of interval lengths. The system models the operation of two units taking into account operation and repair intervals. The restructuring time is associated with the instant when the two-dimensional process first reaches a state where both components are operational. For a process as a whole, each such time corresponds to the system’s Markov regeneration when it begins working anew, from another initial state. Time intervals between restructurings depend on the so-called fixed guaranteed service times. We use the evolution property of the two-dimensional process between Markov regeneration times, which transforms such an evolution into a breaking second-order semi-Markov process. We derive integral equations for the expectations of system efficiency over the time interval from zero to the time of restructuring.

Study of Allocation Guaranteed Time Slot Wireless Body Area Networks Based on IEEE 802.15.4

This paper aims to determine the size of the Guaranteed Time Slot (GTS) on the super frame structure required for each sensor as well as to know the performance of the GTS resized system compared to the GTS standard on IEEE 802.15.4. This article proposes a scheme to improve IEEE 802.15.4 medium access control, called allocation Guaranteed Time Slot (ALGATIS). ALGATIS is expected to effectively allocate guaranteed time slot to the requested sensors, it adjusts the length of the slot in super frame duration based on the length of the packet data. This article presents a simulation experiment of IEEE 802.15.4, especially for star network, to predict the throughput of networks and average energy consumption. The simulation experiments show that the performance of ALGATIS is better than that of IEEE 802.15.4 standard in term of the throughput of networks and average energy consumption

A spectroscopic survey of the small near-Earth asteroid population: Peculiar taxonomic distribution and phase reddening

We present the results of the first-ever visible spectroscopic survey fully dedicated to the small (absolute magnitude H ≥ 20) near-Earth asteroid (NEA) population. Observations have been performed at the New Technology Telescope (NTT) of the European Southern Observatory (ESO), during a 30-night Guaranteed Time Observations programme, in the framework of the European Commission financed NEOShield-2 project. The visible spectra of 147 objects have been obtained and taxonomically classified. They show a peculiar taxonomic distribution, with respect to larger NEAs. In particular, olivine-rich A-types and organic-rich D-types are more abundant than what could be expected by extrapolating the taxonomic distribution of larger NEAs. Such results have implications for the investigation of the first phases of solar system history, including the delivery of prebiotic material on the early Earth. Having been obtained over a large range of solar phase angles, our data allowed us to evidence peculiar phase reddening behaviours for asteroids belonging to different taxonomic types. Low-albedo asteroids display no or limited phase reddening, compared to moderate- and high-albedo objects. This result suggests a promising novel way to distinguish primitive asteroids in the X-complex. In agreement with previous laboratory experiments, olivine-rich surfaces are the most affected by phase reddening.

Allogeneic Transplantation for Acute Myelogenous Leukemia in CR1

Allogeneic Transplantation for Acute Myelogenous Leukemia in CR1

An Optimal Path Model for the Risk-Averse Traveler

In this paper we discuss stochastic optimal path problems where the goal is to find a path that has minimal expected cost and at the same time is less risky (in terms of travel time) than a given benchmark path. The model is suitable for a risk-averse traveler who prefers a path with a more guaranteed travel time to another path that could be faster but could also be slower. Such risk attitude is incorporated using the concept of second order stochastic dominance constraints. A recently developed theory for optimization problems with stochastic dominance constraints ensures that the resulting problem can be written as a large linear integer program with binary variables; for networks of realistic size, however, such a direct approach is not practical because of the size of the resulting optimization problem. Moreover, the solution returned by the model may contain cycles, which is clearly undesirable from a practical perspective. A number of strategies are explored to solve the problem. First, we prove that cycles can be prevented by a simple modification of the model if the arc travel times are mutually independent. We then propose a sample average approximation approach to the problem using samples from the distribution of travel times. Because of the randomness resulting from sampling, it is important that statistical guarantees for the solution returned by the algorithm be given, and we provide heuristic procedures to deal with stochastic constraints. We also incorporate a branch-and-cut approach that exploits the structure of the problem to deal with the integrality constraints more efficiently. We present some numerical experiments for a 1,522-arc system that corresponds to a large portion of the Chicago area network. The results show that our approach can solve the problem very effectively, producing solutions with statistical guarantees of optimality within a reasonable computational time.

CONSTRUCTIONAL FIRE PROTECTION OF STEEL SIN BEAMS OF BUILDINGS AND STRUCTURES

The paper proposes an original method of determining of indicators of building fi re safety in regards to guaranteed resistance time for steel fi re-retardant SIN beams in conditions of standard fi re testing, evaluation of fi re-resistance design limits for steel fi re-retardant SIN beams during buildings design, construction and management, and cost saving during testing of steel structures for fi re-resistance. Operational benefi ts are obtained by non-destructive testing. Fire-resistance of fi re-retardant elements of SIN beam (corrugated wall, upper and lower beam fl anges) is evaluated by revealing of the most strong element of welded I beam.

뿌리산업 제조현장 체계분석 및 데이터 기반 설비보전 환경구축

This paper describes the efficient equipment maintenance that can offer the exact time for repair and change of component in root industry. A conventional method offered the fixed time for repair and change of component because the method is based on early guarantee specification of the component. However the operating condition of manufacturing field is often under worse condition than early guarantee condition for high productivity. So, most components can’t use until early guarantee time due to the operation of various different condition. Therefore we suggest the useful method for efficient equipment-maintenance by manufacturing-field analysis and feedback database. For this, the classification of root industry and related equipment is performed and then the detail classification of the process and component for equipment maintenance. And the monitoring module is also designed to gather data for feedback process and the environment is basically implemented for aging and reliability test.

The bottleneck problem in large scale IEEE 802.15.4/ZigBee networks

In this paper, we handle the bottleneck problem of ZigBee-based networks. The bottleneck problem occurs at the nodes near the ZigBee coordinator since they have too many data to deliver during the data gathering process. This is a fundamental problem which reduces network throughput and prolongs transmission delay. A possible solution is to schedule each node's transmission/receiving time properly. Two fundamental problems we have to answer for such scheduling are when and how long a node should keep awake to transmit/receive packets. To achieve efficient scheduling, in this paper, we propose a centralised top-down-maximum-load-first (TDMLF) scheme which utilises the contention-free guaranteed time slots (GTS) defined in IEEE 802.15.4. By increasing the number of concurrent transmissions, the proposed scheme achieves high system utilisation and thus alleviates the bottleneck problem. Through simulation and real system implementation, we verify that TDMLF successfully reduces the negative effects caused by the bottleneck problem.

Scheduling the Real-Time Transmission of Periodic Measurements in 802.15.4 Wireless Sensor Network

Wireless sensor networks (WSN) are a major technological innovation developed in recent years with many important applications, for example in Cyber-Physical Systems and Internet of Things environments. Although there are many proposals for handling real-time traffic in WSNs, most of them fall into best-effort mechanisms that do not provide real-time guarantees. At the MAC level, the IEEE 802.15.4 standard defines a reservation mechanism called Guaranteed Time Slots (GTS) that uses a first-come first-served service policy, which is not enough to ensure the real-time delivery of packets. In this work, we present a formal definition of the scheduling problem for a sensor network using a reservation mechanism (such as GTS) that provides guarantees for the real-time delivery of packets. We also present a heuristic approach for finding feasible schedules when possible or determining if the requirements of a set of sensors are not feasible.

Performances Comparison of IEEE 802.15.6 and IEEE 802.15.4 Optimization and Exploitation in Healthcare and Medical Applications

In this paper, we simulate the energy consumption, throughput and reliability for both, Zigbee IEEE 802.15.4 Mac protocol and BAN IEEE 802.15.6 exploited in medical applications using Guaranteed Time Slot (GTS) and polling mechanisms by CASTALIA software. Then, we compare and analyze the simulation results. These results show that the originality of this work focuses on giving decisive factors to choose the appropriate MAC protocol in a medical context depending on the energy consumption, number of used nodes, and sensors data rates.

Modeling duration of FSA operating and farm ownership loan guarantees

Purpose The purpose of this paper is to identify determinants of feasible outcome events (expired with no loss, settled for loss, still performing) and time to event of Farm Service Agency (FSA) operating and farm ownership (FO) loan guarantees. Design/methodology/approach Data on 19,126 FSA guaranteed loans, which were made by various lenders to farmers who have limited ability to obtain loans from normal sources without the Federal guarantee, were collected. Cox proportional hazards models for operating loans (OLs) and FO loans are estimated to identify borrower characteristics, loan characteristics, lender types, and farm and macroeconomic environment factors that influence guarantee outcomes. Findings Loans with different characteristics (loan amount, loan term, lender type, region originated) and assistance programs (Beginning Farmer, Interest Assistance) have differing guarantee outcomes. Contemporaneous variables, in particular delinquency status, have a significant impact on guarantee outcomes. Research limitations/implications All loans were originated in calendar years 2004 and 2005. Since FO loans may have as long as 40 year terms, results are not as robust for FO loans as for OLs. Practical implications Different loan characteristics and macroeconomic conditions significantly influence the occurrence of possible guarantee outcomes and time to the outcomes. Originality/value Guaranteed loans are the primary method of government credit assistance to US farm operators. Data on individual borrowers have been difficult to obtain for much of the life of the guaranteed program because loan applications are held privately. This study provides insight on how various factors drive guarantee performance which is useful to policy makers trying to increase guaranteed loan program efficiency.

Stroboscopic Strategy in the Method of Resolving Functions for Game Control Problems with Terminal Payoff Function

The resolving-functions method is analyzed with respect to the theory of conflict-controlled processes with terminal payoff function. A scheme of the method is proposed. This scheme ensures the end of game in a definite guaranteed time in the class of stroboscopic strategies under minimum of additional conditions. The guaranteed times for this scheme of the resolving-functions method are compared with that of the first Pontryagin method.

A novel channel allocation method for time synchronization in wireless sensor networks

SummaryChannel allocation in the wireless sensor networks is one of the important issues, and these networks must allocate shared channels between sensor nodes in the transmission phase. This paper proposes a novel protocol for channel allocation, so it focuses on energy efficiency and collisions avoidance. The main idea of this protocol is based on the Guaranteed Time Slot approach by using novel high‐rate collaborative codes. The sum rate of the proposed collaborative codes is double than the conventional codes, thus increasing the capacity of codes and allowing more nodes to simultaneously transmit at a given time slot. The proposed protocol has a cluster‐based structure, so the sensor nodes of each cluster can communicate together only inside of the any cluster. The protocol performs clustering (grouping) of the nodes based on the geometric distance from the coordinator node and hence allocating different transmission power to each cluster. Because of the difference in transmission power among the groups, the same codes can be reused in the adjacent groups increasing the overall sum rate of the codes. The performance of a proposed protocol is evaluated through extensive simulation and analysis. It is shown from the results that the proposed scheme outperforms significantly the existing ZigBee Guaranteed Time Slot allocation schemes as well as the conventional collaborative codes. Copyright © 2016 John Wiley &amp; Sons, Ltd.

A really simple approximation of smallest grammar

In this paper we present a really simple linear-time algorithm constructing a context-free grammar of size 4glog3/2⁡(N/g) for the input string, where N is the size of the input string and g the size of the optimal grammar generating this string. The algorithm works for arbitrary size alphabets, but the running time is linear assuming that the alphabet Σ of the input string can be identified with numbers from {1,…,Nc} for some constant c. Algorithms with such an approximation guarantee and running time are known, however all of them were non-trivial and their analyses were involved. The here presented algorithm computes the LZ77 factorisation and transforms it in phases to a grammar. In each phase it maintains an LZ77-like factorisation of the word with at most ℓ factors as well as additional O(ℓ) letters, where ℓ was the size of the original LZ77 factorisation. In one phase in a greedy way (by a left-to-right sweep and a help of the factorisation) we choose a set of pairs of consecutive letters to be replaced with new symbols, i.e. nonterminals of the constructed grammar. We choose at least 2/3 of the letters in the word and there are O(ℓ) many different pairs among them. Hence there are O(log⁡N) phases, each of them introduces O(ℓ) nonterminals to a grammar. A more precise analysis yields a bound ℓ+4ℓlog⁡(N/ℓ). As ℓ≤g, this yields the desired bound g+4glog⁡(N/g).