Admission Problem Research Articles

Admission control and resource optimization for multiple-user OFDMA Cognitive Radio systems

In Cognitive Radio (CR) systems, the fluctuating nature of the available frequency resource due to Primary Users (PUs) activity necessitates the introduction of admission and eviction measures at the CR system if a guaranteed Quality of Service (QoS) is required by Real Time (RT) Secondary Users (SUs). This problem has been recently addressed in the literature with simplified assumptions that might become unrealistic in practical system setups. In this paper, we tackle the problem of admission and eviction control of RT SUs in multiple-user Orthogonal Frequency Division Multiple Access (OFDMA) CR systems and propose new solutions that are practical and efficient at the same time. In particular, we propose three different ways to install a Resource Buffer Zone (RBZ) at the time of admission to limit future call drops resulting from fluctuating PU activity. We also study the effect of PU activity on the feasibility of the resource allocation problem and propose three different methods to resolve system outages once they occur. Numerical results obtained through Monte Carlo simulations demonstrate the efficacy of the proposed techniques.

The College Admission Problem with Entrance Criterion

We study the college admission problem with entrance criterion. Each student receives a score from a central exam. The students are divided into two groups: those who are eligible to apply to colleges, and those who are not. Eligibility respects the students’ scores. Each college has a strict preference relation over the students and each student has a strict preference relation over the colleges. We extend the model studied by Perach and Rothblum (2010) to a general case where the students may have the same scores from the central exam. We study ways of assigning students to colleges that respect eligibility criteria. We define several notions of stability. We define three new rules based on the McVitie-Wilson algorithm that satisfy different notions of stability.

Best Unifiers in Transitive Modal Logics

This paper offers a brief analysis of the unification problem in modal transitive logics related to the logic S4: S4 itself, K4, Grz and Godel-Lob provability logic GL. As a result, new, but not the first, algorithms for the construction of `best' unifiers in these logics are being proposed. The proposed algorithms are based on our earlier approach to solve in an algorithmic way the admissibility problem of inference rules for S4 and Grz. The first algorithms for the construction of `best' unifiers in the above mentioned logics have been given by S. Ghilardi in [16]. Both the algorithms in [16] and ours are not much computationally efficient. They have, however, an obvious significant theoretical value a portion of which seems to be the fact that they stem from two different methodological approaches.

COLLEGE ADMISSIONS AND THE ROLE OF INFORMATION: AN EXPERIMENTAL STUDY*

Three well-known matching mechanisms designed to solve the college admissions problems are analyzed in the experimental laboratory in different informational settings. We observe that when the level of information is significantly increased, the proportion of schools and teachers that submit their true preferences decreases. This affects largely the efficiency and stability of the Gale–Shapley and the Boston mechanisms. The TTC mechanism is less sensitive to information and outperforms the other two mechanisms in terms of efficiency and stability, and it is as successful as them in extracting private information.

Discrete-order admission ATP model with joint effect of margin and order size in a MTO environment

Swarming demands and seasonality periodically induce a stringent capacity problem in the made-to-order (MTO) B2B environment. Desirable order admission is a tactic with minimal application cost for handling this problem. A real-time order admission problem with limited major-customer population and batch-size demand with heterogeneous distributions is modeled as a dynamic and stochastic knapsack problem. The optimality of the Markovian deterministic reward-threshold policy is verified. Optimal policy, basic policy, and the capacity rationing method are compared in the designed experiment. The numerical results suggest great potential for increasing profit using the optimal order admission policy for MTO businesses.

Admission and Power Control for Spectrum Sharing Cognitive Radio Networks

We investigate the problem of admission and power control considering a scenario where licensed, or primary, users and cognitive radios, or secondary users, are transmitting concurrently over the same band. The primary users share a common receiver and the interference on this receiver from secondary users should be strictly limited to a certain level. Each secondary link is assumed to have a minimum quality of service (QoS) requirement that should be satisfied together with the interference limit constraint, otherwise the secondary link is not admitted. Under those constraints, admission and power control for secondary users are investigated for two main optimization objectives. First, we maximize the number of admitted secondary links. Second, we maximize the sum throughput of the admitted secondary links. The first problem is NP-hard, hence we provide a distributed close-to-optimal solution based on local measurements at each user and a limited amount of signaling. For the second problem, which is non-convex, we propose a suboptimal algorithm based on sequential geometric programming. The proposed algorithms are compared with previously related work to demonstrate their relative efficiency in terms of outage probability, complexity and achievable throughput.

Robust Exponential Admissibility of Uncertain Switched Singular Time-delay Systems

This paper investigates the problem of robust exponential admissibility for a class of continuous-time uncertain switched singular systems with interval time-varying delay.By defining a properly constructed decay-rate-dependent Lyapunov function and the average dwell time approach,a delay-range-dependent sufficient condition is derived for the nominal system to be regular,impulse free,and exponentially stable.This condition is also extended to uncertain case.The obtained results provide a solution to one of the basic problems in continuous-time switched singular time-delay systems,that is,to identify a switching signal for which the switched singular time-delay system is regular,impulse free,and exponentially stable.Numerical examples are given to demonstrate the effectiveness of the obtained results.

Use of Technology for Supporting and Developing the National Open University of Nigeria

In a country with three million applicants every year, there is very high demand for university education. Conventional universities cannot cope with admission problems because they lack manpower and infrastructural facilities. One of the ways of solving this problem was the establishment of the National Open University of Nigeria. Coping with large population of students is not a problem in the National Open University of Nigeria because of the extensive use of information and communication technology (ICT) to reach learners even in remote locations. However, adequate measures need to be initiated so that more qualified technical staff are employed and basic infrastructure is put in place to cope with these challenges. Besides, it is suggested that students should be compelled to learn and compulsorily familiarize themselves with the use of computers and use of internet search engine regularly. Similarly, the university should upload more course materials promptly, produce more audio/video tapes and video compact disc for the students while radio and television should be utilised in providing both academic and administrative support for the students. Efforts should also be intensified on how to locate and attract professional organizations and individual experts in partnership for the advancement of using needed modern technology to support the university. Key Words: Synchronous Learning, Asynchronous Learning, On-Line Support, Student Counsellors, Customised Programmes

Implementation of the Core in College Admissions Problems When Colleagues Matter

This paper presents mechanisms implementing the core correspondence of many-to-one matching markets, such as college admissions problems, where the students have preferences over the other students who would attend the same college. We first present a sequential mechanism implementing the core. We then show that simple two-stage mechanisms, which mimics the real-life processes, cannot be used to implement the core correspondence in subgame perfect Nash equilibrium even with strong assumptions on agents’ preferences.

Robust Exponential Admissibility of Uncertain Switched Singular Time-delay Systems

This paper investigates the problem of robust exponential admissibility for a class of continuous-time uncertain switched singular systems with interval time-varying delay. By defining a properly constructed decay-rate-dependent Lyapunov function and the average dwell time approach, a delay-range-dependent sufficient condition is derived for the nominal system to be regular, impulse free, and exponentially stable. This condition is also extended to uncertain case. The obtained results provide a solution to one of the basic problems in continuous-time switched singular time-delay systems, that is, to identify a switching signal for which the switched singular time-delay system is regular, impulse free, and exponentially stable. Numerical examples are given to demonstrate the effectiveness of the obtained results.

Joint admission and power control for quality-of-service in the wireless downlink

This paper addresses the problem of joint admission and power control in the downlink of a single-cell code-division-multiple-access (CDMA) wireless network. The objective is to maximize the user-capacity (or base station revenue), while meeting the quality-of-service (QoS) requirements of each admitted user. This paper considers bounded maximum delay and bounded minimum data rate as the QoS measures. For applications with strict QoS requirements, we show that the joint problem can be solved to optimality by performing admission control and power allocation separately. To solve the admission control problem, we give an exact polynomial-time algorithm for user-capacity maximization, and an efficient approximation algorithm with guaranteed performance for base station revenue maximization. To solve the power control problem, we provide two simple power allocation heuristics. For applications with soft QoS requirements, we consider the problem of allocating transmit powers to all users such that the minimum fraction of QoS requirement satisfied for any user is maximized. Regardless of the number of users in the system, we show that the problem always reduces to one-dimensional search. This leads an efficient power control algorithm that provides, in O(1) iterations, solutions arbitrarily close to the optimal one.

Characterization of admissible linear estimators in the growth curve model with respect to inequality constraints

In terms of the theory of inequality and the vectorization transformation of a matrix, we study the admissibility problem of linear estimators in growth curve models with inequality constraints. Under the quadratic loss and the matrix loss, we obtain the necessary and sufficient conditions for a linear estimator of estimable/inestimable linear functions being admissible in the homogeneous and inhomogeneous classes separately.

Density-orbital embedding theory

In the article density-orbital embedding (DOE) theory is proposed. DOE is based on the concept of density orbital (DO), which is a generalization of the square root of the density for real functions and fractional electron numbers. The basic feature of DOE is the representation of the total supermolecular density ${\ensuremath{\rho}}_{s}$ as the square of the sum of the DO ${\ensuremath{\varphi}}_{a}$, which represents the active subsystem $A$ and the square root of the frozen density ${\ensuremath{\rho}}_{f}$ of the environment $F$. The correct ${\ensuremath{\rho}}_{s}$ is obtained with ${\ensuremath{\varphi}}_{a}$ being negative in the regions in which ${\ensuremath{\rho}}_{f}$ might exceed ${\ensuremath{\rho}}_{s}$. This makes it possible to obtain the correct ${\ensuremath{\rho}}_{s}$ with a broad range of the input frozen densities ${\ensuremath{\rho}}_{f}$ so that DOE resolves the problem of the frozen-density admissibility of the current frozen-density embedding theory. The DOE Euler equation for the DO ${\ensuremath{\varphi}}_{a}$ is derived with the characteristic embedding potential representing the effect of the environment. The DO square ${\ensuremath{\varphi}}_{a}^{2}$ is determined from the orbitals of the effective Kohn-Sham (KS) system. Self-consistent solution of the corresponding one-electron KS equations yields not only ${\ensuremath{\varphi}}_{a}^{2}$, but also the DO ${\ensuremath{\varphi}}_{a}$ itself.

Adverse drug reactions causing admission to a paediatric hospital: a pilot study

It is known that adverse drug reactions (ADRs) cause admission to hospital in adults and children. A recent adult study showed that ADRs are an important and frequent cause of hospital admission. The objective of this study is to develop methodology to ascertain the current burden of ADRs through a prospective analysis of all unplanned admissions to a paediatric hospital. Prospective observational study over a 2-week period. There were 19 admissions to the main hospital wards related to an ADR, giving an estimated incidence of 4%, with the ADR directly leading to the admission in 71% of cases. There were no deaths attributable to ADR. 33% of the reactions were possibly avoidable. The drugs most commonly implicated in causing admissions were anti-neoplastic agents. The most common reactions were neutropenia, vomiting and diarrhoea. The health burden of ADRs in the paediatric population is likely to be significant. This pilot study will be used to inform a much larger prospective study providing more detailed evidence of the burden of ill-health from ADRs in children. This larger study will add to a body of research aiming to identify drug-related problems within children to aid paediatric pharmacovigilance. This study provides knowledge regarding the methodology to be used for a larger study investigating ADRs in children. The study will allow authors who wish to replicate the study in their own populations (internationally) to avoid some of the pitfalls in planning a large epidemiological study of paediatric ADRs. The study also provides an estimate of the incidence and problem of admissions caused by ADRs in a UK paediatric population.

The Blocking Lemma for a many-to-one matching model

The Blocking Lemma identifies a particular blocking pair for each non-stable and individually rational matching that is preferred by some agents of one side of the market to their optimal stable matching. Its interest lies in the fact that it has been an instrumental result to prove key results on matching. For instance, the fact that in the college admissions problem the workers-optimal stable mechanism is group strategy-proof for the workers and the strong stability theorem in the marriage model follow directly from the Blocking Lemma. However, it is known that the Blocking Lemma and its consequences do not hold in the general many-to-one matching model in which firms have substitutable preference relations. We show that the Blocking Lemma holds for the many-to-one matching model in which firms’ preference relations are, in addition to substitutable, quota q-separable. We also show that the Blocking Lemma holds on a subset of substitutable preference profiles if and only if the workers-optimal stable mechanism is group strategy-proof for the workers on this subset of profiles.

Admissible Estimation for Linear Combination of Fixed and Random Effects in General Mixed Linear Models

The general mixed linear model can be denoted by y = X β + Z u + e , where β is a vector of fixed effects, u is a vector of random effects, and e is a vector of random errors. In this article, the problem of admissibility of Q y and Q y + q for estimating linear functions, ϱ = L ′β + M ′ u , of the fixed and random effects is considered, and the necessary and sufficient conditions for Q y (resp. Q y + q ) to be admissible in the set of homogeneous (resp. potentially inhomogeneous) linear estimators with respect to the MSE and MSEM criteria are investigated. We provide a straightforward alternative proof to the method that was utilized by Wu (1988), Baksalary and Markiewicz (1990), and Groß and Markiewicz (1999). In addition, we derive the corresponding results on the admissibility problem under the generalized MSE criterion.

NICE guidance on reducing the risk of venous thromboembolism in patients admitted to hospital

NICE guidance on reducing the risk of venous thromboembolism in patients admitted to hospital

The College Admissions problem with lower and common quotas

We study two generalised stable matching problems motivated by the current matching scheme used in the higher education sector in Hungary. The first problem is an extension of the College Admissions problem in which the colleges have lower quotas as well as the normal upper quotas. Here, we show that a stable matching may not exist and we prove that the problem of determining whether one does is NP-complete in general. The second problem is a different extension in which, as usual, individual colleges have upper quotas, but, in addition, certain bounded subsets of colleges have common quotas smaller than the sum of their individual quotas. Again, we show that a stable matching may not exist and the related decision problem is NP-complete. On the other hand, we prove that, when the bounded sets form a nested set system, a stable matching can be found by generalising, in non-trivial ways, both the applicant-oriented and college-oriented versions of the classical Gale–Shapley algorithm. Finally, we present an alternative view of this nested case using the concept of choice functions, and with the aid of a matroid model we establish some interesting structural results for this case.

The roommates problem revisited

One of the oldest matching problems is Gale and Shapley's (1962) [8] “roommates problem”: is there a stable way to assign 2 N students into N roommate pairs? Unlike the classic marriage problem or college admissions problem, there need not exist a stable solution to the roommates problem. However, stability ignores the key physical constraint that roommates require a room and is therefore too restrictive. This motivates a new matching problem: matching agents subject to an initial assignment. A particularly important example is kidney exchange where after an assignment has been made, subsequent tests may determine that a patient and donor are incompatible. This paper introduces an efficient algorithm for finding a Pareto improvement starting from any status quo roommates assignment.

The singleton core in the college admissions problem and its application to the National Resident Matching Program (NRMP)

We show that in the marriage problem the student-optimal algorithm may in fact generate an equilibrium outcome that is college-optimal and student-pessimal in terms of the true preferences even though it is student-optimal and college-pessimal in terms of the submitted preferences. In the college admissions problem, the student-optimal algorithm generates either a matching that is not stable for the true preferences or a matching that is college-optimal and student-pessimal in terms of the true preferences. Thus, our results show that, in the absence of certain match variations, the newly designed student-optimal algorithm adopted by the NRMP since 1998 either may be bias in favor of hospitals in terms of the true preferences or fails to produce a true stable matching. We also discuss when the core is large and when the core is a singleton at a Nash equilibrium.