Parallel cleaning of a network with brushes

AbstractWe consider the process of cleaning a network where at each time step, all vertices that have at least as many brushes as incident, contaminated edges, send brushes down these edges and remove them from the network. An added condition is that, because of the contamination model used, the final configuration must be the initial configuration of another cleaning of the network. We find the minimum number of brushes required for trees, cycles, complete bipartite networks; and for all networks when all edges must be cleaned on each step. Finally, we give bounds on the number of brushes required for complete networks

Game Brush Number

We study a two-person game based on the well-studied brushing process on graphs. Players Min and Max alternately place brushes on the vertices of a graph. When a vertex accumulates at least as many brushes as its degree, it sends one brush to each neighbor and is removed from the graph; this may in turn induce the removal of other vertices. The game ends once all vertices have been removed. Min seeks to minimize the number of brushes played during the game, while Max seeks to maximize it. When both players play optimally, the length of the game is the game brush number of the graph $G$, denoted $b_g(G)$. By considering strategies for both players and modelling the evolution of the game with differential equations, we provide an asymptotic value for the game brush number of the complete graph; namely, we show that $b_g(K_n) = (1+o(1))n^2/e$. Using a fractional version of the game, we couple the game brush numbers of complete graphs and the binomial random graph $\mathcal{G}(n,p)$. It is shown that for $pn \gg \ln n$ asymptotically almost surely $b_g(\mathcal{G}(n,p)) = (1 + o(1))p b_g(K_n) = (1 + o(1))pn^2/e$. Finally, we study the relationship between the game brush number and the (original) brush number.Comment: 20 pages, 3 figure

Near-Optimal Coverage Path Planning with Turn Costs

Coverage path planning is a fundamental challenge in robotics, with diverse applications in aerial surveillance, manufacturing, cleaning, inspection, agriculture, and more. The main objective is to devise a trajectory for an agent that efficiently covers a given area, while minimizing time or energy consumption. Existing practical approaches often lack a solid theoretical foundation, relying on purely heuristic methods, or overly abstracting the problem to a simple Traveling Salesman Problem in Grid Graphs. Moreover, the considered cost functions only rarely consider turn cost, prize-collecting variants for uneven cover demand, or arbitrary geometric regions. In this paper, we describe an array of systematic methods for handling arbitrary meshes derived from intricate, polygonal environments. This adaptation paves the way to compute efficient coverage paths with a robust theoretical foundation for real-world robotic applications. Through comprehensive evaluations, we demonstrate that the algorithm also exhibits low optimality gaps, while efficiently handling complex environments. Furthermore, we showcase its versatility in handling partial coverage and accommodating heterogeneous passage costs, offering the flexibility to trade off coverage quality and time efficiency

HACCP plan fresh fish processing Marituna

In the past regulatory authorities for food products had a duty to ensure that foods offered tothe consumer are at least safe to eat. The authorities required a positive approach of using Good Manufacturing Practices (GMP), producing food in a hygienic manner, and by inspection of finished product. It is now realised that inspection of finished product gives a poor control over the safety of foods. Therefore, since 1 January 1993, regulatory authorities in Europe required that companies take a preventative approach to safety based on the principles of Hazard Analysis and Critical Control Points (HACCP). Anyone exporting fish products to Europe or North America will have to implement a programme based on HACCP. If a company cannot demonstrate to the satisfaction of regulating agencies in importing countries that it has an effective programme operating in their processing plant, importers will not be permitted to accept the products. The United Nations food standard group Codex Alimentarius Commission has recommended HACCP's adoption as a system for ensuring the safety of foods (including finfish and shellfish) and the prevention of foodborne diseases

The Cowl - v.2 - n.19 - Mar 12, 1937

The Cowl - student newspaper of Providence College. Volume 2, Number 19 - March 12, 1937. 6 pages. Note: Due to the way these issues were bound into volumes, some of the letters on extreme left- and right-hand columns are slightly truncated

IST Austria Thesis

This thesis considers two examples of reconfiguration problems: flipping edges in edge-labelled triangulations of planar point sets and swapping labelled tokens placed on vertices of a graph. In both cases the studied structures – all the triangulations of a given point set or all token placements on a given graph – can be thought of as vertices of the so-called reconfiguration graph, in which two vertices are adjacent if the corresponding structures differ by a single elementary operation – by a flip of a diagonal in a triangulation or by a swap of tokens on adjacent vertices, respectively. We study the reconfiguration of one instance of a structure into another via (shortest) paths in the reconfiguration graph. For triangulations of point sets in which each edge has a unique label and a flip transfers the label from the removed edge to the new edge, we prove a polynomial-time testable condition, called the Orbit Theorem, that characterizes when two triangulations of the same point set lie in the same connected component of the reconfiguration graph. The condition was first conjectured by Bose, Lubiw, Pathak and Verdonschot. We additionally provide a polynomial time algorithm that computes a reconfiguring flip sequence, if it exists. Our proof of the Orbit Theorem uses topological properties of a certain high-dimensional cell complex that has the usual reconfiguration graph as its 1-skeleton. In the context of token swapping on a tree graph, we make partial progress on the problem of finding shortest reconfiguration sequences. We disprove the so-called Happy Leaf Conjecture and demonstrate the importance of swapping tokens that are already placed at the correct vertices. We also prove that a generalization of the problem to weighted coloured token swapping is NP-hard on trees but solvable in polynomial time on paths and stars

몽골 울란바타르에서 겨울철 입자상 물질의 개인노출 평가

학위논문(석사)--서울대학교 대학원 :보건대학원 환경보건학과,2019. 8. 이기영.Ulaanbaatar, the capital city of Mongolia has a serious air pollution during winter. Residents of ger, Mongolian traditional housing structure, used coal as indoor heating and cooking fuel. PM2.5 is one of the main air pollutants in coal combustion. It was critical to characterize personal exposure to PM2.5 to prevent adverse health effects by indoor coal burning. This study was conducted to compare personal exposure to PM2.5 of ger and apartment residents by residential characteristics and to evaluate the influence of time-activity patterns on personal exposure to PM2.5. Two-day personal exposures of 16 couples in ger and 16 couples in apartments in Ulaanbaatar, Mongolia were measured from January to February, 2019. All 32 couples were consisted of a full-time working husband and a homemaking housewife. Aslung monitor (Rododo Science, Taiwan) was used for measuring PM2.5. Co-location tests were performed to calibrate the data measured by Aslung with gravimetric methods. To record the time-activity patterns, participants were asked to write the logbook. Microenvironment was divided into home, workplace, outdoor, transportation, and other indoors. Face-to-face surveys were conducted to investigate housing characteristics. The geometric mean of personal exposure to PM2.5 of ger residents was 59.1(1.7) μg/m3 which was significantly higher than that of apartment residents of 26.8(2.0) μg/m3 (p<0.001). Personal exposure increased in the morning when people started activity, decreased in the afternoon, and increased again in the evening regardless of housing type. Similar to indoor air pollution, the ambient PM2.5 concentration was maximum at 10:00 and minimum at 17:00. PM2.5 concentrations at all microenvironment were higher in ger residents. A linear regression analysis identified housing type and ambient PM2.5 concentration as significant factors affecting hourly personal exposure (p<0.001). Exposure at home had the highest contribution to 24-hour personal exposure to PM2.5. The PM2.5/PM10 ratio was ranged from 0.73 – 0.96 in all microenvironment. This study found that ger residents were exposed to higher PM2.5 concentration than apartment residents by indoor coal burning. Reducing measures considering ambient PM2.5 concentration are required to prevent residents of Ulaanbaatar from adverse health effects of PM2.5 emitted by coal combustion.몽골의 수도 울란바타르는 겨울철 공기 중 높은 PM2.5 농도를 보이며 심각한 대기오염 문제를 겪고 있다. 몽골의 전통 가옥인 게르 주민들은 석탄을 실내 난방 및 조리 연료로 직접 연소한다. PM2.5는 석탄 연소로 인해 발생하는 주요 대기오염물질 중 하나로, PM2.5 개인노출의 특성을 파악을 통해 실내 석탄 연소로 인한 건강영향을 예방하는 것이 필요하다. 이 연구는 주거 특성의 차이에 따른 게르와 아파트 거주자의 PM2.5 개인노출을 비교하고, 시간활동패턴이 PM2.5 개인노출에 미치는 영향을 평가하기 위해 수행되었다. 2019년 1월과 2월, 울란바타르의 게르에 거주하는 부부 16쌍과 아파트에 거주하는 부부 16쌍을 대상으로 2일간 입자상 물질 개인노출을 측정하였다. 32쌍의 부부는 풀타임 근로자인 남편과 가정 주부인 아내로 구성되었으며, 모두 비흡연자였다. 입자상물질의 측정 기기로는 Aslung 모니터(Rododo Science, Taiwan)를 사용하였다. 광산식 측정 기기에 의해 측정된 입자상 물질의 농도를 중량법으로 측정한 농도로 보정하기 위해 현지에서 상관성테스트를 진행하였다. 시간활동패턴을 기록하기 위해 연구참여자들을 대상으로 48시간동안 머무는 미세환경에 대한 정보를 로그북에 기록하도록 하였으며, 주거 특성을 파악하기 위해 모든 가구를 대상으로 방문 설문조사가 수행되었다. 게르와 아파트 거주자의 24시간 PM2.5 개인노출의 기하 평균은 각각 59.1(1.7) 와 26.8(2.0) μg/m3 였으며, 통계적으로 유의한 차이가 있었다 (p<0.001). PM2.5 농도는 주거 특성에 관계없이 사람들이 활동을 시작한 아침에 증가했으며, 오후에 감소하여 다시 저녁에 증가했다. 선형회귀분석 결과, 주거 형태와 외기 PM2.5 농도가 개인노출에 통계적으로 유의한 영향을 미쳤다 (p<0.001). 각 미세환경이 PM2.5 개인노출에 기여하는 정도는 게르 거주자와 아파트 거주자 모두 집에서 가장 컸다. PM2.5/PM10 의 범위는 0.73-0.96로, PM2.5의 발생이 연소와 같은 인위적인 활동에 의한 것임을 확인하였다. 이 연구는 게르 거주자가 실내 석탄 연소로 아파트 거주자보다 PM2.5 개인노출이 높은 것을 확인하였다. 울란바타르 거주자가 석탄 연소에 의해 방출되는 PM2.5에 의한 건강영향을 줄이기 위해 외기농도를 고려한 국가적 대책이 필요하다.1. Introduction 1 2. Materials and methods 6 2.1 Study design 6 2.2 Equipment 7 2.3 Time-activity pattern 9 2.4 Questionnaire 10 2.5 Quality assurance 11 2.6 Data analysis 13 3. Result 14 3.1 Housing characteristics 14 3.2 Demographic information 18 3.3 Personal exposure to PM2.5 21 3.4 Microenvironmental PM2.5 concentration 32 3.5 Relationship with ambient PM2.5 concentration 39 3.6 Time-activity pattern 43 3.7 Microenvironmental contribution 45 3.8 Action radius 47 3.8 Ratio between different particle sizes 49 4. Discussion 53 5. Conclusion 59 References 60 국문초록 66 Appendix 1 (Logbook) 69 Appendix 2 (Questionnaire) 70Maste

Inscape Fall 1979

The Fall 1979 edition of the Inscape: Literary and Art Magazine.https://scholarworks.moreheadstate.edu/inscape_magazine_archive/1070/thumbnail.jp

Logs, labor, and living: an archaeological investigation of African-American laborers at the Upper and Middle Landing sawmills at Natchez-Under-the-Hill

By combining investigations of two sawmill complexes at Natchez-Under-the-Hill, Mississippi, and ethnohistoric data from contemporaneous mill operations in the region, this thesis analyzes aspects of two mid-nineteenth century lumber operations. It focuses not only on the machinery and technology involved in these operations, but also on the individuals, many of whom were enslaved prior to the Civil War, whose skills and labors provided the backbone for these early milling enterprises. The data for this research were derived from archival documents, oral testimonies, and artifacts recovered from archaeological survey and excavation. The archaeological data comes from excavations carried out at the circa 1841-1870 Brown Cozzens Sawmill (the Well site 22AD993) in the summer of 1999 and the survey in the spring of 1999 of the Learned Mill Road Area. Archaeological survey of the former Andrew Brown-Rufus Learned sawmill at Upper Landing and excavations at the Cozzens sawmill at Middle Landing yielded valuable information regarding the spatial layout of the mill complexes as well as details about the working and living conditions at these sawmills through time. At the former location of the Andrew Brown sawmill, only a few artifacts were recovered in the survey dating to the operation of the mill at this location from 1818 to 1917. Archaeological investigations at the former Cozzens Sawmill yielded information on the location and operation of this sawmill complex along the riverfront. A brick foundation provided information on the orientation and placement of the historic sawmill and its mechanical operation. Artifacts excavated from a brick-lined well represent an archaeological assemblage from a mid-nineteenth century sawmill complex. Parts of the mill\u27s machinery, food items, medicine bottles, clothing material, and personal items were excavated from the feature. Through the analysis of the Upper and Middle Landing sawmill operations, which involved the compilation of various textual source, a greater understanding of not only the financial and technical operation of a mid-nineteenth century sawmill in Natchez was garnered, but a greater insight was gained into the social and spatial workings of a mill operation and the dangers workers faced during this turbulent time