Loop Exit Research Articles

ВОПРОСЫ ПЕРЕУСТРОЙСТВА СЪЕЗДОВ РАЗВЯЗОК С ПОЗИЦИИ ОБЕСПЕЧЕНИЯ БЕЗОПАСНОСТИ ДВИЖЕНИЯ

The article describes the possibility of modernization of one of the common types of interchanges at different levels in our country named "cloverleaf". It's important because the zones of interlacing flows of loop exits with a significant traffic intensity reduces the safety of traffic along them and the overall throughput of the interchange. This study simulates the operation of an interchange with a left-turn semi-direct ramp at different levels on the busiest left-turn direction of traffic. The aim of the article is to show the significant effectiveness of this design solution.

Control of Heat Transfer in a Vertical Ground Heat Exchanger for a Geothermal Heat Pump System

This paper presents a mathematical model of heat transfer behavior between the liquid inside vertical underground geothermal pipes and the surrounding ground for heating (in the winter) and cooling (in the summer) modes in a ground heat exchanger (GHE) that can optimize its output temperature. The GHE’s output temperature reaches the appropriate value when the water velocity is lowered enough. Subsequently, the proposed model was applied to a case study of a 400-ton geothermal heat pump system (GHPS) at Oakland University, in both the heating and cooling modes, to assess its validity and improve the GHE’s performance. The model was implemented in MATLAB using an ordinary differential equation (ODE) solver. Four different water velocities were used to demonstrate the significant effect of velocity on the loop exit temperature. Model predictive control (MPC) was designed to optimize the GHE’s output temperature by controlling the water velocity, which could reduce the energy consumption used for heat and water circulating pumps. The results reveal that the acceptable range of the water velocity for Oakland University’s GHE was between 0.35 and 0.45 m/s, which ensured that the heat pump system delivered the proper temperature to provide the Human Health Building (HHB) with a comfortable temperature regardless of the season. The suggested water velocity ranges in vertical single U-tube pipes with diameters of De 25 mm, De 32 mm, and De 40 mm are between 0.33 and 0.43 m/s, 0.35 to 0.45 m/s, and 0.38 to 0.48 m/s, respectively.

Polarimetry fiber optic gyroscope.

We report a different mechanism for rotation sensing by analyzing the polarization of light exiting from a Sagnac loop. Unlike in an interferometric fiber optic gyroscope (I-FOG), here the counter-propagating waves in the Sagnac loop are orthogonally polarized at the loop exit and, consequently, cannot directly interfere with each other when recombined at the exit. We show that the Stokes parameters s2 and s3 of the combined waves are simply the cosine and sine functions of the phase difference between the counter propagation waves, which is linearly proportional to the rotation rate, allowing precise determination of the rotation rate by polarization analysis. We build such a proof-of-concept polarimetry FOG and achieved key performance parameters comparable to those of a high-end tactical-grade gyroscope. In particular, the device shows a bias instability of 0.09°/h and an angular random walk of 0.0015°/h, with an unlimited dynamic range, demonstrating its potential use for rotation sensing. This new approach eliminates the need for phase modulation required in I-FOGs, and promotes easy photonics integration, enabling the development of low-cost FOGs for price-sensitive applications, such as autonomous and robotic vehicles.

Glucose Control Using a Standard Versus an Enhanced Hybrid Closed Loop System: A Randomized Crossover Study.

Hybrid closed loop (HCL) insulin delivery with the Medtronic Minimed 670G system is effective and safe in people with type 1 diabetes (T1D). This study compared glucose control, closed loop (CL) exits, and alarm frequency with the standard HCL (s-HCL) versus enhanced HCL (e-HCL) Medtronic system. Pump-experienced T1D adults (n = 11; 9 female; mean [SD] age: 51 years [15 years]; HbA1c 7.5% [1.0%] or 58 mmol/mol [7.7 mmol/mol]) were assigned, in random order, s-HCL or e-HCL for 1 week each in a supervised live-in setting. e-HCL incorporated enhanced bolus reminders and iterative changes, broadening glucose and insulin delivery parameters permitting persistence in CL. For both s-HCL and e-HCL, insulin delivery was by a Medtronic pump with identical interventions (missed bolus, exercise, high-glycemic index, and high-fat meals), insulin action times, and insulin-carbohydrate ratios implemented. The primary outcome was continuous glucose monitoring time in target range. Analysis was by paired t-test for normally distributed data and Wilcoxon-signed rank test otherwise. e-HCL resulted in significantly fewer CL alerts and exits. Time in target and mean glucose favored e-HCL but did not reach statistical significance. No episodes of severe hypoglycemia or ketoacidosis occurred. Relative to s-HCL, e-HCL use significantly decreases CL exits and alerts, and tended to improve glycemia without compromising safety, despite multiple food and exercise challenges during the study. Longer term studies at home are merited.

The Automation of C Program Verification by Symbolic Method of Loop Invariants Elimination

During deductive verification of programs written in imperative languages, the generation and proof of verification conditions corresponding to loops can cause difficulties, because each one must be provided with an invariant whose construction is often a challenge. As a rule, the methods of invariant synthesis are heuristic ones. This impedes its application. An alternative is the symbolic method of loop invariant elimination suggested by V.A. Nepomniaschy in 2005. Its idea is to represent a loop body in a form of special replacement operation under certain constraints. This operation expresses loop effect in a symbolic form and allows to introduce an inference rule which uses no invariants in axiomatic semantics. This work represents the further development of this method. It extends the mixed axiomatic semantics method suggested for C-light program verification. This extension includes the verification method of iterations over changeable arrays possibly with loop exit in C-light programs. The method contains the inference rule for iterations without loop invariants. This rule was implemented in verification conditions generator which is a part of the automated system of C-light program verification. To prove verification conditions automatically in ACL2, two algorithms were developed and implemented. The first one automatically generates the replacement operation in ACL2 language, the second one automatically generates auxiliary lemmas which allow to prove the obtained verification conditions in ACL2 successfully in automatic mode. An example which illustrates the application of the mentioned methods is described.

Invariant Elimination of Definite Iterations over Arrays in C Programs Verification

This work represents the further development of the method for definite iteration verification [7]. It extends the mixed axiomatic semantics method [1] suggested for C-light program verification. This extension includes a verification method for definite iteration over unchangeable arrays with a loop exit in C-light programs. The method includes an inference rule for the iteration without invariants, which uses a special function that expresses loop body. This rule was implemented in verification conditions generator, which is the part of our C-light verification system. To prove generated verification conditions an induction is applied which is a challenge for SMT-solvers. At proof stage the SMT-solver CVC4 is used in our verification system. To overcome mentioned difficulty a rewriting strategy for verification conditions is suggested. A method based on theory extension by new theorems to prove verification conditions is suggested. An example, which illustrates the application of these methods, is considered. The article is published in the authors’ wording.

Redistribution of DNA loop domains in human lymphocytes under blast transformation with interleukin 2.

At higher order levels chromatin fibers in interphase nuclei are organized into loop domains. Gene regulatory elements (promoters and enhancers) are often located near the sites of loop attachments. Therefore, loop domains play a key role in regulation of cell transcriptional activity. We investigated the kinetics of DNA loop exit during single cell gel electrophoresis (the comet assay) of nucleoids obtained from two cell types that differ in their synthetic activity – human lymphocytes and lymphoblasts. Lymphocyte activation and transformation into lymphoblasts (blast transformation) was performed with interleukin 2. The results obtained suggest that a rearrangement of the loops occurs after lymphocyte activation. After blast transformation we observed an increase of the amount of loop domains on the surface of nucleoids against a decrease of the inner loop fraction. Therefore, the comet assay can be used for detection of large-scale changes in the cell nucleus that follow changes in cell functional state.

Technique for Early Reliability Prediction of Software Components Using Behaviour Models.

Behaviour models are the most commonly used input for predicting the reliability of a software system at the early design stage. A component behaviour model reveals the structure and behaviour of the component during the execution of system-level functionalities. There are various challenges related to component reliability prediction at the early design stage based on behaviour models. For example, most of the current reliability techniques do not provide fine-grained sequential behaviour models of individual components and fail to consider the loop entry and exit points in the reliability computation. Moreover, some of the current techniques do not tackle the problem of operational data unavailability and the lack of analysis results that can be valuable for software architects at the early design stage. This paper proposes a reliability prediction technique that, pragmatically, synthesizes system behaviour in the form of a state machine, given a set of scenarios and corresponding constraints as input. The state machine is utilized as a base for generating the component-relevant operational data. The state machine is also used as a source for identifying the nodes and edges of a component probabilistic dependency graph (CPDG). Based on the CPDG, a stack-based algorithm is used to compute the reliability. The proposed technique is evaluated by a comparison with existing techniques and the application of sensitivity analysis to a robotic wheelchair system as a case study. The results indicate that the proposed technique is more relevant at the early design stage compared to existing works, and can provide a more realistic and meaningful prediction.

Loop Invariants Elimination for Definite Iterations over Unchangeable Data Structures in C Programs

The C-program verification is an urgent problem of modern programming. To apply known methods of deductive verification it is necessary to provide loop invariants which might be a challenge in many cases. In this paper we consider the C-light language [18] which is a powerful subset of the ISO C language. To verify C-light programs the two-level approach [19, 20] and the mixed axiomatic semantics method [1, 3, 11] were suggested. At the first stage, we translate [17] the source C-light program into Ckernel one. The C-kernel language [19] is a subset of C-light. The theorem of translation correctness was proved in [10, 11]. The C-kernel has less statements with respect to the C-light, this allows to decrease the number of inference rules of axiomatic semantics during its development. At the second stage of this approach, the verification conditions are generated by applying the rules of mixed axiomatic semantics [10, 11] which could contain several rules for the same program statement. In such cases the inference rules are applied depending on the context. Let us note that application of the mixed axiomatic semantics allows to significantly simplify verification conditions in many cases. This article represents an extension of this approach which includes our verification method for definite iteration over unchangeable data structures without loop exit in C-light programs. The method contains a new inference rule for the deifinite iteration without invariants. This rule was implemented in verification conditions generator. At the proof stage the SMT-solver Z3 [12] is used. An example which illustrates the application of this technique is considered. he article is published in the authors’ wording.

Investigation Motorcycle Safety at Exit Ramp Sections by Analyzing Historical Crash Data and Rider’s Perception

The purpose of this study is to evaluate the safety performance of four exit ramp types and the major contributing factors on motorcycle crashes and injury severity of motorcycle riders. A six-year crash data were collected in Florida, and a web-based survey (234 samples) was conducted. 573 crashes were found at 419 exits, including 178 diamond exits, 71 directional exits, 85 loop exits and 85 outer connection exits. For a diamond exit, both the survey and crash data showed that this type was safer and more preferable by motorcycle riders; while a loop exit was the most dangerous exit due to the sharp curve and a certain length of curve with limited visibility. For a directional exit, longer ramp lengths and the reverse curvature are the major factors causing motorcycle crashes. For an outer connection exit, the riders rated it as a safe type; however, the data showed higher average crash frequency and rate than those at diamond exits or directional exits. The possible reason could be the unexpected curvature in the middle of the ramp, which could be dangerous if the rider is not familiar with the exit ramp location or doesn’t pay attention to the ramp curvatures. The crash predictive model was developed, and the result indicated that if all remained the same, a directional exit, a loop exit, or an outer connection exit will have 16%, 27%, and 42% more crashes than a diamond exit, respectively. The findings from this study can help policy-makers and engineers to develop and apply effective countermeasures to reduce motorcycle crashes and injury severity levels for different exit ramp types.

Unroll-based copy elimination for enhanced pipeline scheduling

Enhanced pipeline scheduling (EPS) is a software pipelining technique which can achieve a variable initiation interval (II) for loops with control flow via its code motion pipelining. EPS, however, leaves behind many renaming copy instructions that cannot be coalesced due to interferences. These copies take resources and, more seriously, they may cause a stall if they rename a multilatency instruction whose latency is longer than the II aimed for by EPS. This paper proposes a code transformation technique based on loop unrolling which makes those copies coalescible. Two unique features of the technique are its method of determining the precise unroll amount, based on an idea of extended live ranges, and its insertion of special bookkeeping copies at loop exits. The proposed technique enables EPS to avoid a serious slowdown from latency handling and resource pressure, while keeping its variable II and other advantages. In fact, renaming through copies, followed by unroll-based copy elimination, is EPS's solution to the cross-iteration register overwrite problem in software pipelining. It works for loops with arbitrary control flow that EPS must deal with, as well as for straightline loops. Our empirical study performed on a VLIW testbed with a two-cycle load latency shows that 86 percent of the otherwise uncoalescible copies in innermost loops become coalescible when unrolled 2.2 times on average. In addition, it is demonstrated that the unroll amount obtained is precise and the most efficient. The unrolled version of the VLIW code includes fewer no-op VLIW caused by stalls, improving the performance by a geometric mean of 18 percent on a 16-ALU machine.

Verification of Finite Iterations over Tuples of Data Structures

In order to eliminate loop invariants in the process of program verification, a new language construct called finite iteration over tuples of data structures is introduced. Simulation of such iterations by means of iterations over hierarchical data structures is described. This enables one to apply the symbolic verification method, which was developed earlier, to such iterations. The simulation also applies to the case of iterations over tuples of data structures that include a loop exit statement. A technique for deriving and proving correctness conditions based on the induction principles is described. For finite iterations over files, a problem-oriented technique for proving correctness conditions is proposed. By way of example, the verification of two programs designed for file processing is described.

Catheter ablation of ventricular tachycardia in patients with right ventricular dysplasia: Identification of target sites by entrainment mapping techniques.

To identify target sites for radiofrequency ablation of ventricular tachycardia (VT) by entrainment mapping techniques in patients with arrhythmogenic right ventricular dysplasia. Entrainment mapping and radiofrequency ablation of eight VTs was performed in seven patients. Radiofrequency ablation was applied at 31 reentry circuits sites that were classified based on findings during entrainment. By entrainment criteria the 31 sites were classified as: exit sites (n = 12), proximal sites (n = 6), and outer loop sites (n = 13). Radiofrequency current application terminated VT at 7 of 31 sites: 2 of 12 exit sites (17%), 4 of 6 proximal sites (67%), and 1 of 13 outer loop sites (8%). Radiofrequency ablation terminated VTs most often at sites proximal to the exit as opposed to outer loop sites and exit sites (P = 0.05). The critical isthmus for ablation of VT in right ventricular dysplasia often may be distant to the exit.

GOTO Removal Based on Regular Expressions

We present an algorithm for eliminating GOTOs and replacing them with structured IF-THEN-ELSE and loop constructs. Previous approaches have treated GOTO removal as an isolated problem for programming languages. In this paper, we describe a way of reducing GOTO removal to the well-understood problem of converting a finite-state transition network to a regular expression. A semantics is provided showing how the regular expression form may be interpreted as a non-deterministic program. A set of pattern-based reduction rules is used to transform the regular expression form back to a conventional structured program. Besides achieving greater conceptual unity, the method leads to a simpler algorithm where the task of recognizing loop boundaries is separated from that of identifying loop exits. We have successfully applied the algorithm in systems for re-engineering COBOL/IMS database systems and assembly language code. © 1997 by John Wiley & Sons, Ltd. J. Software Maintenance 9: 47–66, 1997

Loop exits and structured programming

Internal exits from loops represent a critically important control structure that should be taught in the introductory CS1 curriculum. Without access to those facilities, students are often incapable of solving simple programming problems that occur frequently in applications. This paper reviews the existing evidence in support of such facilities and argues that it is important to reconsider our traditional pedagogical approach as we adopt new languages of instruction.

Interactive control restructuring

An interactive algorithm for improving control flow is introduced. This algorithm has been implemented within the ENCORE re-engineering environment. The objective of the algorithm is to restructure input code so as to simplify the control flow. A key feature of the algorithm is that is permits user control during the restructuring. The algorithm also handles, in a natural manner, multiple return statements, multiple loop exits, multi-level loop exits and endless loops.

Programming the premature loop exit

Programming the premature loop exit

Axiomatic semantics for “escape” statements

This paper introduces a new approach for specifying the axiomatic semantics of escape statements, e.g., loop exit. The association of an escape statement with the appropriate enclosing block is specified entirely within the proof rules. Our approach also handles multiple-level exit statements.

Eliminating go to's while preserving program structure

Suppose we want to eliminate the local go to statements of a Pascal program by replacing them with multilevel loop exit statements. The standard ground rules for eliminating go to's require that we preserve the flow graph of the program, but they allow us to completely rewrite the control structures that glue together the program's atomic tests and actions. The go to's can be eliminated from a program under those ground rules if and only if the flow graph of that program has the graph-theoretic property named reducibility. This paper considers a stricter set of ground rules, introduced by Peterson, Kasami, and Tokura, which demand that we preserve the program's original control structures, as well as its flow graph, while we eliminate its go to's. In particular, we are allowed to delete the go to statements and the labels that they jump to and to insert various exit statements and labeled repeat-endloop pairs for them to jump out of. But we are forbidden to change the rest of the program text in any way. The critical issue that determines whether go to's can be eliminated under these stricter rules turns out to be the static order of the atomic tests and actions in the program text. This static order can be encoded in the program's flow graph by augmenting it with extra edges. It can then be shown that the reducibility of a program's augmented flow graph, augmenting edges and all, is a necessary and sufficient condition for the eliminability of go to's from that program under the stricter rules.

Incremental data-flow analysis algorithms

An incremental update algorithm modifies the solution of a problem that has been changed, rather than re-solving the entire problem. ACINCF and ACINCB are incremental update algorithms for forward and backward data-flow analysis, respectively, based on our equations model of Allen-Cocke interval analysis. In addition, we have studied their performance on a “nontoy” structured programming language L. Given a set of localized program changes in a program written in L, we identify a priori the nodes in its flow graph whose corresponding data-flow equations may be affected by the changes. We characterize these possibly affected nodes by their corresponding program structures and their relation to the original change sites, and do so without actually performing the incremental updates . Our results can be refined to characterize the reduced equations possibly affected if structured loop exit mechanisms are used, either singly or together, thereby relating richness of programming language usage to the ease of incremental updating.