Arbitrary Origin Research Articles

Temporal upscaling of solar radiation components using an analytical model for variability modeling

To properly design systems that harness the solar resource, reliable measurements or estimates of its availability are needed. Often, this data is only available at temporal resolutions that are not sufficiently fine to capture the short-term fluctuations of the solar resource, creating uncertainty in the design and performance assessment of solar-powered systems. Synthetic irradiance generation techniques aim to create high temporal resolution estimates starting from lower resolution data, however, a literature review on the topic shows opportunities for improvement regarding the generality of the generation and evaluation approaches. This work proposes novel methods to estimate a quantifiable indicator of short-term variability from hourly data, a new temporal upscaling methodology for time series of arbitrary origin and destination temporal resolution, based on explicit mathematical functions and sufficient generality for application in different contexts, and an improved assessment methodology. The method was applied tor ground and satellite upscaling up to 1 min, resulting in time series with characteristics consistent with those of a higher temporal resolution and exhibit minimum deviations against the original time series characteristics. This method has applications not only for upscaling of low temporal resolution data, but also for gap-filling techniques and the upscaling of hourly solar radiation forecasts.

Interpretable Machine Learning for Mode Choice Modeling on Tracking-Based Revealed Preference Data

Mode choice modeling is imperative for predicting and understanding travel behavior. For this purpose, machine learning (ML) models have increasingly been applied to stated preference and traditional self-recorded revealed preference data with promising results, particularly for extreme gradient boosting (XGBoost) and random forest (RF) models. Because of the rise in the use of tracking-based smartphone applications for recording travel behavior, we address the important and unprecedented task of testing these ML models for mode choice modeling on such data. Furthermore, as ML approaches are still criticized for leading to results that are hard to understand, we consider it essential to provide an in-depth interpretability analysis of the best-performing model. Our results show that the XGBoost and RF models far outperform a conventional multinomial logit model, both overall and for each mode. The interpretability analysis using the Shapley additive explanations approach reveals that the XGBoost model can be explained well at the overall and mode level. In addition, we demonstrate how to analyze individual predictions. Lastly, a sensitivity analysis gives insight into the relative importance of different data sources, sample size, and user involvement. We conclude that the XGBoost model performs best, while also being explainable. Insights generated by such models can be used, for instance, to predict mode choice decisions for arbitrary origin–destination pairs to see which impacts infrastructural changes would have on the mode share.

Can the Gravitational Wave Background Feel Wiggles in Spacetime?

Recently the international pulsar timing array collaboration has announced the first strong evidence for an isotropic gravitational-wave background (GWB). We propose that rapid small oscillations (wiggles) in the Hubble parameter would trigger a resonance with the propagating gravitational waves, leaving unique signatures in the GWB spectrum as sharp resonance peaks/troughs. The proposed signal can appear at all frequency ranges and is common to GWBs with arbitrary origin. The resonant signal can appear as a trough only when the GWB is primordial, and its amplitude will also be larger by one perturbation order than in the nonprimordial case. These properties serve as a smoking gun for the primordial origin of the observed GWB. We showcased the viability of the signal to near future observations using the recent NANOGrav 15 yr data.

Fishery and population characteristics of the Indian white shrimp, Penaeus indicus H. Milne Edwards, 1837 (Decapoda, Dendrobranchiata) in Pulicat Lake, southeast coast of India

Abstract Fishery and population characteristics of the Indian white shrimp, Penaeus indicus, were studied in Pulicat Lake, on the southeast coast of India, using the FiSAT software package. The asymptotic length (), growth coefficient (K) and arbitrary origin of growth (t0) were estimated by the ELEFAN method to be 16.18 cm, 0.60 year−1 and −0.18 year, respectively. The asymptotic length () was calculated as 16.09 cm using the Wetherall method. The growth performance index (Ø′) was found to be 2.19. The mortality parameters Z, F and M were computed to be 3.85, 2.30 and 1.55 year−1, respectively. The pattern of recruitment was observed to be year-round, with a peak from June to September. The total stock, annual catch and exploitation rate for P. indicus were estimated to be 1518.43 tonnes, 809.3 tonnes, and 0.59 year−1, respectively. The estimated Maximum Sustainable Yield (MSY) was found to be 131.95 tonnes less than the annual catch. The stock of P. indicus was found to be over-exploited, so it is suggested that the effort level be reduced by 16.3% in order to sustain this resource in Pulicat Lake.

First post-Minkowskian approach to turbulent gravity

We compute the metric fluctuations induced by a turbulent energy-matter tensor within the first order Post-Minkowskian approximation. It is found that the turbulent energy cascade can in principle interfere with the process of black hole formation, leading to a potentially strong coupling between these two highly nonlinear phenomena. It is further found that a power-law turbulent energy spectrum $E(k) \sim k^{-n}$ generates metric fluctuations scaling like $x^{n-2}$, where $x$ is a four-dimensional distance from an arbitrary origin in spacetime. This highlights the onset of metric singularities whenever $n <2$, meaning that $2d$ fluid turbulence ($n=3$) yields smooth %(differentiable) metric fluctuations, scaling like $x$, while $3d$ turbulence ($n=5/3$) yields a weakly singular metric $x^{-1/3}$and purely random fluctuations, $n=1$, generate a stronger $1/x$ singularity. Finally, the effect of metric fluctuations on the geodesic motion of test particles is also discussed as a potential technique to extract information on the spectral characteristics of fluctuating spacetime.

Fishery, population characteristics and stock status of the bigeye thresher Alopias superciliosus Lowe, 1841 off Thoothukudi, south-east coast of India

Fishery, population parameters and stock estimates of the bigeye thresher Alopias superciliosus Lowe, 1841 from the Thoothukudi coast of Gulf of Mannar Marine Biosphere Reserve (GoMMBR) was studied during the period 2015 to 2019. Results of the study reveals that the estimated annual average production of sharks from Thoothukudi region was 105 t of which the dominant shark species was A. supercilious (52.70%). The length of the sampled A. supercilious ranged between 108 and 265 cm. Results of the length-weight relationship showed negative allometric growth with b value of 2.66. The growth parameters viz, asymptotic length (L∞), growth co-efficient (K) and arbitrary origin of growth (t0 ) were estimated at 367 cm, 0.39 y-1 and 0.12 respectively. The mortality parameters viz, total mortality (Z), fishing mortality (F) and natural mortality (M) rates were estimated at 1.20, 0.70 and 0.50 y-1, respectively. In Thoothukudi, the recruitment season of A. superciliosus was found during March and October showing optimal exploitation with exploitation rate (E) of 0.58 and the estimated exploitation ratio (U) was 0.54. The virtual population analysis (VPA) showed a fishing pressure on the 240 to 320 cm length group. The estimated annual catch and maximum sustainable yield (MSY) were 58 and 68 t respectively. The present study gives valuable baseline information on the fishery and population characteristics of this vulnerable and data deficit resource A. superciliosus off Thoothukudi. Keywords: Growth and mortality parameters, Maximum sustainable yield, Recruitment overfishing, Virtual population analysis

Numerical simulation of the White sea

We describe our experience of three-dimensional numerical simulation of thermohydrodynamic and biogeochemical processes in the White Sea in collaboration with several institutes of the Russian Academy of Sciences and foreign colleagues. The comprehensive model of the White Sea, called JASMINE, is based on the FEMAO model of the Arctic Ocean. It reproduces the dynamics of sea water and ice and includes, i. a., a pelagic biogeochemical submodel BFM, which is able to describe fluxes of matter between scalar fields corresponding to groups of organisms or organic and inorganic matter of various forms and fractions. Matter and energy exchange with bottom sediments and sea ice has also been modeled, and the model includes a sea-ice ecology block BFMSI. Besides, it is possible to simulate contamination transport for tracers of arbitrary origin. We relate the history of developing the model, tell how the spatial resolution was increased, describe the resolved and yet unresolved problems. The problem of boundary values is discussed, as well as the possibility of a cascade simulation, where coarser models of larger objects provide data for more precise regional models. As an example, we introduce the already implemented interaction between the INM RAS model of the Earth system and JASMINE on INM RAS cluster. We touch upon the systemic problem of the development of complex computing systems in the field of Earth sciences, i. e. the lack of documentation and community, and the fact that the project depends on the availability of a single person: the author of the model. A prototype of a data assimilation system for the model is described: it allows correcting the phase state according to observational data (such as station data). The possibilities of carrying out numerical experiments are demonstrated: the transfer of a passive tracer with a delta-shaped initial distribution, the response of the sea to climate change and, in particular, to variations in river runoff, and other applications of the model to achieve a better understanding of the processes in the White Sea.

Tracking of atmospheric phenomena with artificial neural networks: a supervised approach

Tracking of atmospheric phenomena, such as Tropical Cyclones (TC) and Polar Mesocyclones (PMC), — is a frequently performed task in the climate sciences. It is a crucial part of any climatic or short-period study since the occurrence and characteristics of a phenomenon at some moment carries significantly less information compared to its evolution. In some cases of synoptic-scale phenomena, this problem has established well-developed solutions (e.g., for extratropical cyclones, ETC). However, in the majority of other cases, there are no reliable tracking algorithms at the moment. In this study, we present the generic framework for the tracking of atmospheric phenomena of an arbitrary kind in the source data of nearly arbitrary origin. The core entity of our approach is the function of dissimilarity of representations of a phenomenon in two subsequent data frames which is learned under supervision of an artificial neural network. As an implementation of the proposed approach, we present the results of the tracking of Tropical Cyclones and Polar Mesocyclones. We demonstrate the success of our approach in terms of formal metric MOTA (Multiple Object Tracking Accuracy) and the empirical distributions of key lifecycle characteristics of TC and PMC.

Microseismic event detection in large heterogeneous velocity models using Bayesian multimodal nested sampling

Abstract In passive seismic and microseismic monitoring, identifying and characterizing events in a strong noisy background is a challenging task. Most of the established methods for geophysical inversion are likely to yield many false event detections. The most advanced of these schemes require thousands of computationally demanding forward elastic-wave propagation simulations. Here we train and use an ensemble of Gaussian process surrogate meta-models, or proxy emulators, to accelerate the generation of accurate template seismograms from random microseismic event locations. In the presence of multiple microseismic events occurring at different spatial locations with arbitrary amplitude and origin time, and in the presence of noise, an inference algorithm needs to navigate an objective function or likelihood landscape of highly complex shape, perhaps with multiple modes and narrow curving degeneracies. This is a challenging computational task even for state-of-the-art Bayesian sampling algorithms. In this paper, we propose a novel method for detecting multiple microseismic events in a strong noise background using Bayesian inference, in particular, the Multimodal Nested Sampling (MultiNest) algorithm. The method not only provides the posterior samples for the 5D spatio-temporal-amplitude inference for the real microseismic events, by inverting the seismic traces in multiple surface receivers, but also computes the Bayesian evidence or the marginal likelihood that permits hypothesis testing for discriminating true vs. false event detection.

Population dynamics of spinycheek grouper Epinephelus diacanthus (Valenciennes, 1828) from the southwest coast of India

Subtle bathymetric distribution of Epinephelus diacanthus as a function of age was observed during the exploratory survey conducted for the past 20 years (2000-2019) by deploying different fishing gears such as bottom trawl, perch trap, bottom set vertical line and hand line suitable for various niche from Muddy to rocky bottom. The juveniles and the individuals of maturing stages of less than 3 years age groups occupies predominantly in the shallow muddy areas and sporadically occurs in the neighbor rocky with sandy grounds. However, the larger specimens of more than 3 years age groups occupies exclusively the rocky habitat of the depth between 60- 110m. Moreover the larger size above 30cm total length of above 3 years age group was not recorded from shallow muddy grounds during the past 20 years survey is imperative. The Population parameters of E. diacanthus were estimated from length frequency data through ELEFAN I (FISAT programs). The asymptotic length (La) was 56.7 cm, K was 0.29 year­­­-1 and the arbitrary origin of growth curve (t0) was -0.66 year, hence von Bertalanffy growth equation was derived as Lt = 56.7 (1-e-0.29 (t – (-0.66)) during 2009. The length at- age was estimated as 13.7 cm, 22.8 cm, 33.8 cm, 41.1 cm, 44.4 cm, 48.61 cm, 52.9 cm,54.1 cm and 56.7 cm in the I, II, III, IV, V, VI, VII, VIII and IX year respectively. The annual rate of natural mortality (M) was found to be 0.66, the fishing mortality (F) and total mortality (Z) were 0.67 and 1.33 respectively. Exploitation ratio (E) was 0.50, whereas E max was found to be 0.48, so the present study revealed that the fishing pressure was more than the optimum level on the stock of E. diacanthus. The mean length at first capture (Lc) was found to be 14 cm total length. The VPA analysis revealed that more fishing mortality was occurred in 16-17cm size group and 36, 46 cm size groups. The recruitment of this species was peak in the month of July. Length weight relationship of this species was found to be W= 0.002 L2.89 for pooled data. The relative condition factor (Kn) and seasonal condition factor (K) were varying among size groups, juvenile had highest K value.

Modelling of the reference STARs procedures in the context of RPAS integration in non-segregated airspace

PurposeThis work presents the part of the research in the integration of the remotely piloted aircraft systems (RPAS) in non-segregated airspace. The purpose of this study is to elaborate the reference shape of the Standard Instrument Arrivals (STARs) procedures of controlled airports. The STARs parameters are unique for the aerodromes and depend on navigational aids (NAVAIDs), manoeuvres and aircraft categories. Therefore, the elaboration of reference shapes was advisable in the context of RPAS integration research.Design/methodology/approachThe models were based on the procedure design guidelines by International Civil Aviation Organization. The statistics of existing STARs were prepared using Aeronautical Information Publications to determine the representative procedural parameters. Construction of procedural shapes required to define the nominal flight path and tolerance areas.FindingsIn statistics, the standard deviation of distances was below the determined reference mean values, thus the models were convergent with existing procedures.Research limitations/implicationsThe modelling was limited to initial, intermediate, final and missed approach segments. Arrival segment was not modelled. NAVAIDs include Instrument Landing System Category 1 (in final and missed approach) and very high-frequency omni-directional ranging or global navigation satellite systems (in initial and intermediate approach segments).Practical implicationsPrepared models may be used in research in the integration of the new types of aerial vehicles in existing air traffic management systems.Originality/valueThe reference STARs possess commonly used procedural manoeuvres (straight-in, turn, racetrack and base turn) and different NAVAIDs. The parameters of approach segments were determined as representative of the existing procedures. Moreover, the models are suitable to place at arbitrary origin and runway axis bearing.

STARR‐seq and UMI‐STARR‐seq: Assessing Enhancer Activities for Genome‐Wide‐, High‐, and Low‐Complexity Candidate Libraries

The identification of transcriptional enhancers and the quantitative assessment of enhancer activities is essential to understanding how regulatory information for gene expression is encoded in animal and human genomes. Further, it is key to understanding how sequence variants affect enhancer function. STARR‐seq enables the direct and quantitative assessment of enhancer activity for millions of candidate sequences of arbitrary length and origin in parallel, allowing the screening of entire genomes and the establishment of genome‐wide enhancer activity maps.In STARR‐seq, the candidate sequences are cloned downstream of the core promoter into a reporter gene's transcription unit (i.e., the 3′ UTR). Candidates that function as active enhancers lead to the transcription of reporter mRNAs that harbor the candidates’ sequences. This direct coupling of enhancer sequence and enhancer activity in cis enables the straightforward and efficient cloning of complex candidate libraries and the assessment of enhancer activities of millions of candidates in parallel by quantifying the reporter mRNAs by deep sequencing. This article describes how to create focused and genome‐wide human STARR‐seq libraries and how to perform STARR‐seq screens in mammalian cells, and also describes a novel STARR‐seq variant (UMI‐STARR‐seq) that allows the accurate counting of reporter mRNAs for STARR‐seq libraries of low complexity. © 2019 The Authors. Basic Protocol 1: STARR‐seq plasmid library cloning Basic Protocol 2: Mammalian STARR‐seq screening protocol Alternate Protocol: UMI‐STARR‐seq screening protocol—unique molecular identifier integration Support Protocol: Transfection of human cells using the MaxCyte STX scalable transfection system

Fishery and population dynamics of Epinephelus malabaricus (Bloch &amp; Schneider, 1801) off Tuticorin, southeast coast of India

Fishery, population characteristics and stock estimates of grouper with special reference to Epinephelus malabaricus from Tuticorin were carried out during 2015-2017. Among the groupers, E. malabaricus was the dominant resource contributing 42.2%, with an annual average production of 420t along this region. The asymptotic length (L∞), growth coefficient (K) and arbitrary origin of growth (t0) were estimated at 99.75 cm, 0.53 y-1 and 0.18 respectively. The mortality parameters, the instantaneous total mortality rate (Z), fishing mortality (F) and natural mortality rates (M) were estimated at 1.14 y-1, 0.62 y-1 and 0.52 y-1 respectively. The recruitment season was during April to August. The length structured virtual population (VPA) analysis revealed a heavy fishing pressure on length group between 40 and 55cm and there is no sign of recruitment over-fishing in this region. The estimated maximum sustainable yield (MSY) and annual catch were 384 t and 420 t respectively. E. malabaricus was optimally exploited as the exploitation ratio (E) was 0.54 but the study infers that further increase in effort may have a detrimental effect on the stock of this species. The results of this study will serve as baseline information for formulating future management measures for the resource along the coast.

A law of ordinal random error: The Rasch measurement model and random error distributions of ordinal assessments

Assessments in ordered categories are ubiquitous in educational, social and health sciences. These assessments are analogous to measurements in the natural sciences in that an idealised linear continuum is partitioned by successive thresholds into contiguous, ordered categories. In advanced analyses, the ordinal assessments are characterised with a probabilistic model as a function of a vector of threshold parameters defining the categories and a scalar parameter for the entity of measurement which is taken to be a measurement on an interval scale with an arbitrary origin and unit. One such model is the Rasch measurement model. If the ordinal assessments fit the model the probability distribution is taken to be a random error distribution of inferred replicated assessments. Therefore, it is analogous to the Gaussian random error distribution of replicated measurements known as the law of error. However, the Gaussian distribution is strictly log-concave which makes it unimodal with a smooth transition between probabilities of adjacent measurements. Such a distribution, referred to as randomly unimodal, ensures there is no evidence that unknown factors have produced systematic errors, and in turn justifies the mean as an estimate of the measure of the entity. The paper establishes that random unimodality arises from the natural ordering of the thresholds in the Rasch measurement model. Then by analogy to the Gaussian law of error, a distribution of ordinal assessments that has its thresholds in the natural order and fits the Rasch model may be said to satisfy the law of ordinal error. Again by analogy to Gaussian distribution with respect to replicated measurements, the law of ordinal error ensures that no unaccounted-for factors have produced systematic errors and that the estimates of the scalar parameter of the Rasch model can be taken as an estimate of the measure of the entity assessed.

SEQUIN: a grammar inference framework for analyzing malicious system behavior

Targeted attacks on IT systems are a rising threat to the confidentiality of sensitive data and the availability of critical systems. The emergence of Advanced Persistent Threats (APTs) made it paramount to fully understand the particulars of such attacks in order to improve or devise effective defense mechanisms. Grammar inference paired with visual analytics (VA) techniques offers a powerful foundation for the automated extraction of behavioral patterns from sequential event traces. To facilitate the interpretation and analysis of APTs, we present SEQUIN, a grammar inference system based on the Sequitur compression algorithm that constructs a context-free grammar (CFG) from string-based input data. In addition to recursive rule extraction, we expanded the procedure through automated assessment routines capable of dealing with multiple input sources and types. This automated assessment enables the accurate identification of interesting frequent or anomalous patterns in sequential corpora of arbitrary quantity and origin. On the formal side, we extended the CFG with attributes that help describe the extracted (malicious) actions. Discovery-focused pattern visualization of the output is provided by our dedicated KAMAS VA prototype.

Population dynamics and stock assessment of Delegoa threadfin bream, Nemipterus bipunctatus (Nemipteridae), from the Wadge Bank, South India

Fishery, population characteristics and stock estimates of Nemipterus bipunctatus were studied during June 2015 to May 2016 from Wadge Bank, South India. This region is characterised by rich biodiversity and has a conducive influence of the Indian Ocean and Arabian Sea. The asymptotic length (L?), growth coefficient (K) and arbitrary origin of growth (t0) were estimated as 30.5 cm, 0.85/year and 0.18 respectively. The mortality parameters, total mortality rate (Z), fishing mortality rate and natural mortality rate (M) were estimated as 2.20, 0.95 and 1.25 respectively. Exploitation ratio (E) was found to be 0.57 which showed marginal over exploitation of the species at Wadge Bank. This species has two recruitment seasons, one major season from October to December and another minor season in August. The length structured Virtual population analysis revealed heavy fishing pressure on the length group 24 to 28 cm and hence the delegoa threadfin bream was not found to suffer due to recruitment overfishing in Wadge Bank. Estimated total stock, Maximum Sustainable Yield (MSY) and annual catch were 5625.9348 tonnes, 1935.321t, 2419.152t respectively. Present level of Exploitation rate (U) and Exploitation ratio (F/Z) were estimated to be 0.43 and 0.57 respectively. The study infers the cod end mesh size of the trawls operated at Wadge Bank coast has to be increase from 10 to 25 mm to increase the yield per recruit, the effort could also be maintained as the exploitation ratio of 0.50 to have maximum yield per recruit. The study suggests reducing the present level of effort by 8 percent may be needed to sustain the stock of N. bipunctatus in Wadge Bank, South India

Spherical Wave Expansion With Arbitrary Origin for Near-Field Antenna Measurements

The far-field radiation pattern of an antenna under test (AUT) can be derived via a spherical wave expansion of near-field antenna measurement data. The transformation as well as the measurement time scales with the number of spherical mode coefficients which depends on the radius of the sphere enclosing the antenna. In existing transformation procedures, the radius is measured from the center of the measurement sphere. Thus, the radius increases for an offset-mounted antenna so that more spherical mode coefficients are required to represent the electromagnetic field. In this communication, a procedure is proposed where the origin of the spherical wave expansion can be specified independently of the measurement sphere. With this procedure, the number of coefficients can always be minimized by selecting an expansion origin that minimizes the sphere enclosing the AUT. A translated expansion origin requires to include the probe pointing direction in the probe response constant calculation. This is achieved by Euler rotations of the probe receiving coefficients. The benefits of the procedure are demonstrated by measurements of an offset-mounted AUT.

ТИПОЛОГИЧЕСКИЙ ПОДХОД К ОПРЕДЕЛЕНИЮ УРОВНЯ КАЧЕСТВА ОБЪЕКТОВ И ПРОЦЕССОВ В УПРАВЛЕНИИ ОРГАНИЗАЦИОННЫМИ СИСТЕМАМИ

The purpose of this work consists in the presentation of the results of the theoretical generalization of the problem in the quality level definition in processes and objects of arbitrary origin with the use of a typological approach as a basis of control in organization systems.&#x0D; In the investigation there were used methods of a system analysis, a mathematical modeling of multi-parametric social objects, methods of a structural anal-ysis and also a methodology of a universal quality management (UQM).&#x0D; Investigation results. A multidimensional information object space of matrices of groups of quality indices is considered, a generalized model of a twodimensional matrix of relations of quality indices parameters in Cartesian coordinates is presented, quality indices are shown and their application for adaptive marketing control is shown, a procedure for the quality assessment of objects with the aid of models of a neuro-network typification is offered, and the expediency of basic directions realization in strategy of quality control regarding the set of objects and processes of an organization system under analysis is also substantiated. As an example there is considered a neuro-network approach at the typification of engineering positions in modern mechanical engineering and procedures on the basis of a competence approach of the identification process of young specialists with available vacant seats.&#x0D; Conclusions. The quality parameters are a com-plex category in control of objects/processes and can be considered as a general methodological approach to the control of different organization systems. At the same time there can be used simulators of quality me-tering and typification, and also clusterization and grouping quality indices with the aid of which it is possible to ensure efficiently enough the realization of the identification procedure of objects/processes on quality indices with the application of neuro-network models.&#x0D;

Emergence of linguistic laws in human voice

Linguistic laws constitute one of the quantitative cornerstones of modern cognitive sciences and have been routinely investigated in written corpora, or in the equivalent transcription of oral corpora. This means that inferences of statistical patterns of language in acoustics are biased by the arbitrary, language-dependent segmentation of the signal, and virtually precludes the possibility of making comparative studies between human voice and other animal communication systems. Here we bridge this gap by proposing a method that allows to measure such patterns in acoustic signals of arbitrary origin, without needs to have access to the language corpus underneath. The method has been applied to sixteen different human languages, recovering successfully some well-known laws of human communication at timescales even below the phoneme and finding yet another link between complexity and criticality in a biological system. These methods further pave the way for new comparative studies in animal communication or the analysis of signals of unknown code.

A Target Searching Scenario in Undirected Acyclic Graph

In a generic problem in search theory we have some metric search space and two players - a target T and a searcher S. Mostly T is static in the space according to some specified probability distribution or in some cases dynamic, andS starts its search at some arbitrary start point. The usual goal will be to design a strategy that minimizes the expected time forS to findT .S knows the search space but has no other information and T could be a fully or partially informed target. In some versions, S has visibility characteristics allowing it to see a small distance ‘ ’ from its location. This kind of exploration problems relate to various contexts, such as robot motion planning in hazardous or inaccessible terrain, maintaining security of large networks, and searching, indexing, and analyzing digital data in the Internet [1] [2] [3]. One of the earliest examples of such problems is the linear search problem, proposed by Bellman [4] and Beck [5]. Here, the search space is an infinite line, with the searcher initially at an arbitrary origin, and the target located at an unknown point on the line, at distanced from the origin. The objective is to minimize the worst-case ratio of the distance traveled by the searcher over d. Different scenario (with cycles) is considered in cops and robbers problem [6] where the cops and robbers take alternate turns in movements and the question usually posed is how many pursuers are necessary to ensure the eventual capture of all the robbers. The Isaac’s Princess and Monster problem [7] is also a related problem but with different scenario. The Lost Cow problem [8] is stated as a short-sighted cow following along an infinite fence and wants to find the gate. The lost cow problem is limited in the idea that the target is static. In case of one dimensional space, if a moving target wants to escape, then it can do so by constantly moving away from the searcher. And in case of a cyclic graph, a fully informed target can move around in cycles and never be found by the searcher. The present study stands out in that it studies the problem in case of undirected acyclic graph which was not studied before. But the proposed search space offers an interesting environment to both target and the searcher. To the target, it provides an opportunity to move towards the searcher without being found; and to the searcher it provides an easier search space by removing the case of cyclic movement of the target. Sleator and Tarjan [9] suggested evaluating the performance of an online algorithm using competitive analysis. This paper proposes an online algorithm for the provided search space and also attempts to find upper and lower bounds of the competitive ratio. General Terms