These are my recent Pin​board​.in links:

• [1206.6866] Sto­chas­tic Opti­mal Con­trol in Con­tin­u­ous Space-​​Time Multi-​​Agent Systems

  “Recently, a the­ory for sto­chas­tic opti­mal con­trol in non-​​linear dynam­i­cal sys­tems in con­tin­u­ous space-​​time has been devel­oped (Kap­pen, 2005). We apply this the­ory to col­lab­o­ra­tive multi-​​agent sys­tems. The agents evolve accord­ing to a given non-​​linear dynam­ics with addi­tive Wiener noise. Each agent can con­trol its own dynam­ics. The goal is to min­i­mize the accu­mu­lated joint cost, which con­sists of a state depen­dent term and a term that is qua­dratic in the con­trol. We focus on sys­tems of non-​​interacting agents that have to dis­trib­ute them­selves opti­mally over a num­ber of tar­gets, given a set of end-​​costs for the dif­fer­ent pos­si­ble agent-​​target com­bi­na­tions. We show that opti­mal con­trol is the com­bi­na­to­r­ial sum of inde­pen­dent single-​​agent single-​​target opti­mal con­trols weighted by a fac­tor pro­por­tional to the end-​​costs of the dif­fer­ent com­bi­na­tions. Thus, multi-​​agent con­trol is related to a stan­dard graph­i­cal model infer­ence prob­lem. The addi­tional com­pu­ta­tional cost com­pared to single-​​agent con­trol is expo­nen­tial in the tree-​​width of the graph spec­i­fy­ing the com­bi­na­to­r­ial sum times the num­ber of tar­gets. We illus­trate the result by sim­u­la­tions of sys­tems with up to 42 agents.”
  
  coor­di­na­tion agent-​​based emergent-​​design nudge-​​targets control-​​theory

• [1205.6917] Robust self-​​triggered coor­di­na­tion with ternary controllers

  “This paper regards coor­di­na­tion of net­worked sys­tems, which is stud­ied in the frame­work of hybrid dynam­i­cal sys­tems. We design a coor­di­na­tion scheme which com­bines the use of ternary con­trollers with a self-​​triggered com­mu­ni­ca­tion pol­icy. The com­mu­ni­ca­tion pol­icy requires the agents to col­lect, at each sam­pling time, rel­a­tive mea­sure­ments of their neigh­bors’ states: the col­lected infor­ma­tion is then used to update the con­trol and deter­mine the fol­low­ing sam­pling time. We prove that the pro­posed scheme ensures finite-​​time con­ver­gence to a neigh­bor­hood of a con­sen­sus state. We then study the robust­ness of the pro­posed self-​​triggered coor­di­na­tion sys­tem with respect to skews in the agents’ local clocks, to delays, and to lim­ited pre­ci­sion in com­mu­ni­ca­tion. Fur­ther­more, we present two sig­nif­i­cant vari­a­tions of our scheme. First, we design a time-​​varying con­troller which asymp­tot­i­cally dri­ves the sys­tem to con­sen­sus. Sec­ond, we adapt our frame­work to a com­mu­ni­ca­tion model in which an agent does not poll all its neigh­bors simul­ta­ne­ously, but sin­gle neigh­bors instead. This com­mu­ni­ca­tion pol­icy actu­ally leads to a self-​​triggered “gos­sip” coor­di­na­tion system.”
  
  network-​​theory multi-​​agent-​​systems mechanism-​​design emergent-​​design consensus-​​systems nudge-​​targets algo­rithms

• [1205.2607] Simulation-​​Based Game The­o­retic Analy­sis of Key­word Auc­tions with Low-​​Dimensional Bid­ding Strategies

  “We per­form a simulation-​​based analy­sis of key­word auc­tions mod­eled as one-​​shot games of incom­plete infor­ma­tion to study a series of mech­a­nism design ques­tions. Our first ques­tion addresses the degree to which incen­tive com­pat­i­bil­ity fails in gen­er­al­ized second-​​price (GSP) auc­tions. Our results sug­gest that sin­cere bid­ding in GSP auc­tions is a strik­ingly poor strat­egy and a poor pre­dic­tor of equi­lib­rium out­comes. We next show that the rank-​​by-​​revenue mech­a­nism is wel­fare opti­mal, cor­rob­o­rat­ing past results. Finally, we ana­lyze profit as a func­tion of auc­tion mech­a­nism under a series of alter­na­tive set­tings. Our con­clu­sions coin­cide with those of Lahaie and Pen­nock [2007] when val­ues and qual­ity scores are strongly pos­i­tively cor­re­lated: in such a case, rank-​​by-​​bid rules are clearly supe­rior. We diverge, how­ever, in show­ing that auc­tions that put lit­tle weight on qual­ity scores almost uni­ver­sally dom­i­nate the pure rank-​​by-​​revenue scheme.”
  
  game-​​theory agent-​​based sim­u­la­tion eco­nom­ics auc­tion nudge-​​targets

• Graph­ing the his­tory of phi­los­o­phy « Drunks&Lampposts

  “Each philoso­pher is a node in the net­work and the lines between them (or edges in the ter­mi­nol­ogy of graph the­ory) rep­re­sents lines of influ­ence. The node and text are sized accord­ing to the num­ber of con­nec­tions (both in and out). The algo­rithm that visu­alises the graph also tends to put the bet­ter con­nected nodes in the cen­tre of the dia­gram so we see the most influ­en­tial philoso­phers, in large text, clus­tered in the cen­tre. It all seems about right with the major fig­ures in the west­ern philo­soph­i­cal tra­di­tion tak­ing the cen­tre stage. (I need to also add the direc­tion of influ­ence with a arrow head – some­thing I’ve not got round to yet.) A short­com­ing how­ever is that this eval­u­a­tion only takes into account direct lines of influ­ence. Indi­rect influ­ence via another per­son in the net­work does not enter into it. This prob­a­bly explains why Descartes is smaller than you’d think. It would also be bet­ter if the nodes were sized only by the num­ber of out­ward con­nec­tions although I think over­all the dif­fer­ences would be slight. I’ll get round to that.”
  
  visu­al­iza­tion philosopher-​​mining

• [1206.3666] Unsu­per­vised adap­ta­tion of brain machine inter­face decoders

  “The per­for­mance of neural decoders can degrade over time due to non­sta­tion­ar­i­ties in the rela­tion­ship between neu­ronal activ­ity and behav­ior. In this case, brain-​​machine inter­faces (BMI) require adap­ta­tion of their decoders to main­tain high per­for­mance across time. One way to achieve this is by use of peri­od­i­cal cal­i­bra­tion phases, dur­ing which the BMI sys­tem (or an exter­nal human demon­stra­tor) instructs the user to per­form cer­tain move­ments or behav­iors. This approach has two dis­ad­van­tages: (i) cal­i­bra­tion phases inter­rupt the autonomous oper­a­tion of the BMI and (ii) between two cal­i­bra­tion phases the BMI per­for­mance might not be sta­ble but con­tin­u­ously decrease. A bet­ter alter­na­tive would be that the BMI decoder is able to con­tin­u­ously adapt in an unsu­per­vised man­ner dur­ing autonomous BMI oper­a­tion, i.e. with­out know­ing the move­ment inten­tions of the user. In the present arti­cle, we present an effi­cient method for such unsu­per­vised train­ing of BMI sys­tems for con­tin­u­ous move­ment con­trol. The pro­posed method uti­lizes a cost func­tion derived from neu­ronal record­ings, which guides a learn­ing algo­rithm to eval­u­ate the decod­ing para­me­ters. We ver­ify the per­for­mance of our adap­tive method by sim­u­lat­ing a BMI user with an opti­mal feed­back con­trol model and its inter­ac­tion with our adap­tive BMI decoder. The sim­u­la­tion results show that the cost func­tion and the algo­rithm yield fast and pre­cise tra­jec­to­ries towards tar­gets at ran­dom ori­en­ta­tions on a 2-​​dimensional com­puter screen. For ini­tially unknown and non-​​stationary tun­ing para­me­ters, our unsu­per­vised method is still able to gen­er­ate pre­cise tra­jec­to­ries and to keep its per­for­mance sta­ble in the long term. The algo­rithm can option­ally work also with neu­ronal error sig­nals instead or in con­junc­tion with the pro­posed unsu­per­vised adaptation.”
  
  FOR-​​SCIENCE brain-​​machine-​​interface user-​​interface adaptive-​​control emergent-​​design

• [1206.3980] Visu­al­iz­ing Stream­ing Text Data with Dynamic Maps

  “The many end­less rivers of text now avail­able present a seri­ous chal­lenge in the task of glean­ing, ana­lyz­ing and dis­cov­er­ing use­ful infor­ma­tion. In this paper, we describe a method­ol­ogy for visu­al­iz­ing text streams in real time. The approach auto­mat­i­cally groups sim­i­lar mes­sages into “coun­tries,” with key­word sum­maries, using seman­tic analy­sis, graph clus­ter­ing and map gen­er­a­tion tech­niques. It han­dles the need for visual sta­bil­ity across time by dynamic graph lay­out and Pro­crustes pro­jec­tion tech­niques, enhanced with a novel sta­ble com­po­nent pack­ing algo­rithm. The result pro­vides a con­tin­u­ous, suc­cinct view of evolv­ing top­ics of inter­est. It can be used in pas­sive mode for overviews and sit­u­a­tional aware­ness, or as an inter­ac­tive data explo­ration tool. To make these ideas con­crete, we describe their appli­ca­tion to an online ser­vice called TwitterScope.”
  
  visu­al­iza­tion data algo­rithms user-​​experience

• [1205.3352] Revis­it­ing the effect of exter­nal fields in Axelrod’s model of social dynamics

  “The study of the effects of spa­tially uni­form fields on the steady-​​state prop­er­ties of Axelrod’s model has yielded plenty of con­tro­ver­sial results. Here we re-​​examine the impact of this type of field for a selec­tion of para­me­ters such that the field-​​free steady state of the model is het­ero­ge­neous or mul­ti­cul­tural. Analy­ses of both one and two-​​dimensional ver­sions of Axelrod’s model indi­cate that, con­trary to pre­vi­ous claims in the lit­er­a­ture, the steady state remains het­ero­ge­neous regard­less of the value of the field strength. Turn­ing on the field leads to a dis­con­tin­u­ous decrease on the num­ber of cul­tural domains, which we argue is due to the insta­bil­ity of zero-​​field het­ero­ge­neous absorb­ing con­fig­u­ra­tions. We find, how­ever, that spa­tially nonuni­form fields that imple­ment a con­sen­sus rule among the neigh­bor­hood of the agents enforces homog­e­niza­tion. Although the over­all effects of the fields are essen­tially the same irre­spec­tive of the dimen­sion­al­ity of the model, we argue that the dimen­sion­al­ity has a sig­nif­i­cant impact on the sta­bil­ity of the field-​​free homo­ge­neous steady state.”
  
  com­plex­ol­ogy agent-​​based exter­nal­i­ties sim­u­la­tion evolutionary-​​economics nudge-​​targets

• [1206.3421] Lin­ear Latent Vari­able Mod­els: The lava-​​package

  “An R pack­age for spec­i­fy­ing and esti­mat­ing lin­ear latent vari­able mod­els is pre­sented. The phi­los­o­phy of the imple­men­ta­tion is to sep­a­rate the model spec­i­fi­ca­tion from the actual data, which leads to a dynamic and easy way of mod­el­ing com­plex hier­ar­chi­cal struc­tures. Sev­eral advanced fea­tures are imple­mented includ­ing robust stan­dard errors for clus­tered cor­re­lated data, multi­group analy­ses, non-​​linear para­me­ter con­straints, infer­ence with incom­plete data, max­i­mum like­li­hood esti­ma­tion with cen­sored and binary obser­va­tions, and instru­men­tal vari­able esti­ma­tors. In addi­tion an exten­sive sim­u­la­tion inter­face cov­er­ing a broad range of non-​​linear gen­er­al­ized struc­tural equa­tion mod­els is described. The model and soft­ware are demon­strated in data of mea­sure­ments of the sero­tonin trans­porter in the human brain.”
  
  ontol­ogy sta­tis­tics algo­rithms R-​​language linear-​​models model-​​view-​​controller design-​​patterns

• [1205.6129] The Miss­ing Mem­ris­tor: Novel Nan­otech­nol­ogy or rather new Case Study for the Phi­los­o­phy and Soci­ol­ogy of Science?

  “In 2008, it was widely announced that the miss­ing mem­ris­tor, a basic two-​​terminal elec­tri­cal cir­cuit ele­ment, had finally been dis­cov­ered. The mem­ris­tor is the fourth and last such cir­cuit ele­ment and thus com­pletes cir­cuit the­ory. Pre­dicted already in 1971, the even­tual dis­cov­ery of some­thing seem­ingly so basic needed almost 40 years. How­ever, this dis­cov­ery is doubted. The pre­dicted mem­ris­tor has no mate­r­ial mem­ory and is based on mag­netic flux, but the dis­cov­ered devices con­sti­tute ana­logue mem­ory stor­age that do not involve mag­net­ism. The per­son who orig­i­nally pro­posed the mem­ris­tor did not reject the dis­cov­ery but instead changed his mind about what a mem­ris­tor is. We briefly intro­duce the his­tory and then care­fully mem­ris­tance and the mem­ris­tor as such. We dis­cuss its sta­tus as a model rather than a device. We dis­cuss the dis­cov­ered devices, their sta­bil­ity, and how sta­bil­ity relates to the con­sis­tency of the the­o­ret­i­cal enti­ties. A thought exper­i­ment assumes a world with­out mag­net­ism. Induc­tors can­not exist there, but mem­ory resis­tors could still be con­structed. On the same grounds as the mem­ris­tor was his­tor­i­cally pre­dicted, an “induc­tor” could then be pre­dicted. Likely, some­body would also ‘dis­cover’ one. A ten­ta­tive soci­o­log­i­cal analy­sis com­pares to the flawed detec­tion of grav­i­ta­tional waves but comes to very dif­fer­ent conclusions.”
  
  symmetry-​​is-​​the-​​way-​​things-​​ought-​​to-​​be history-​​of-​​science technical-​​assumptions engineering-​​philosophy

• [1205.2776] Trans­port on cou­pled spa­tial networks

  “Trans­port processes on spa­tial net­works are rep­re­sen­ta­tive of a broad class of real world sys­tems which, rather than being inde­pen­dent, are typ­i­cally inter­de­pen­dent. We pro­pose a mea­sure of util­ity to cap­ture key fea­tures that arise when such sys­tems are cou­pled together. The cou­pling is defined in a way that is not solely topo­log­i­cal, rely­ing on both the dis­tri­b­u­tion of sources and sinks, and the method of route assign­ment. Using a toy model, we explore rel­e­vant cases by sim­u­la­tion. For cer­tain para­me­ter val­ues, a pic­ture emerges of two regimes. The first occurs when the flows go from many sources to a small num­ber of sinks. In this case, net­work util­ity is largest when the cou­pling is at its max­i­mum and the aver­age short­est path is min­i­mized. The sec­ond regime arises when many sources cor­re­spond to many sinks. Here, the opti­mal cou­pling no longer cor­re­sponds to the min­i­mum aver­age short­est path, as the con­ges­tion of traf­fic must also be taken into account. More gen­er­ally, results indi­cate that cou­pled spa­tial sys­tems can give rise to behav­ior that relies sub­tly on the inter­play between the cou­pling and ran­dom­ness in the source-​​sink distribution.”
  
  nudge-​​targets network-​​theory emergent-​​design epi­demi­ol­ogy sim­u­la­tion

• [1206.5849] Under­stand­ing the com­plex­ity of the L’evy-walk nature of human mobil­ity with a multi-​​scale cost/​benefit model

  “Prob­a­bil­ity dis­tri­b­u­tions of human dis­place­ments has been fit with expo­nen­tially trun­cated L’evy flights or fat tailed Pareto inverse power law prob­a­bil­ity dis­tri­b­u­tions. Thus, peo­ple usu­ally stay within a given loca­tion (for exam­ple, the city of res­i­dence), but with a non-​​vanishing fre­quency they visit nearby or far loca­tions too. Herein, we show that an impor­tant empir­i­cal dis­tri­b­u­tion of human dis­place­ments (range: from 1 to 1000 km) can be well fit by three con­sec­u­tive Pareto dis­tri­b­u­tions with sim­ple inte­ger expo­nents equal to 1, 2 and ($gtrap­prox$) 3. These three expo­nents cor­re­spond to three dis­place­ment range zones of about 1 km $less­sim Delta r less­sim$ 10 km, 10 km $less­sim Delta r less­sim$ 300 km and 300 km $less­sim Delta r less­sim $ 1000 km, respec­tively. These three zones can be geo­graph­i­cally and phys­i­cally well deter­mined as dis­place­ments within a city, vis­its to nearby cities that may occur within just one-​​day trips, and visit to far loca­tions that may require multi-​​days trips. The incre­men­tal inte­ger val­ues of the three expo­nents can be eas­ily explained with a three-​​scale mobil­ity cost/​benefit model for human dis­place­ments based on sim­ple geo­met­ri­cal con­strains. Essen­tially, peo­ple would divide the space into three major regions (close, medium and far dis­tances) and would assume that the travel ben­e­fits are randomly/​uniformly dis­trib­uted mostly only within spe­cific urban-​​like areas.”
  
  Levy-​​flights city-​​planning multiscale-​​phenomena self-​​similarity

• [1206.7011] Ultra­thin Ter­a­hertz Pla­nar Lenses

  “Con­ven­tional opti­cal com­po­nents shape the wave­front of prop­a­gat­ing light by adjust­ing the opti­cal path length, which requires the use of rather thick lenses, espe­cially for the adjust­ment of ter­a­hertz (THz) radi­a­tion due to its long wave­length. Two ultra­thin THz pla­nar lenses were designed and fab­ri­cated based on inter­face phase mod­u­la­tion of antenna res­o­nance. The lens thick­nesses were extremely reduced to 100 nm, which is only ¹⁄₄₀₀₀^th of the illu­mi­nat­ing light wave­length. The focus­ing and imag­ing func­tions of the lenses were exper­i­men­tally demon­strated. The ultra­thin opti­cal com­po­nents described herein are a sig­nif­i­cant step toward the devel­op­ment of a micro-​​integrated THz system.”
  
  optics engineering-​​design nudge-​​targets

• [1206.3789] Tree decom­po­si­tion and para­me­ter­ized algo­rithms for RNA structure-​​sequence align­ment includ­ing ter­tiary inter­ac­tions and pseudoknots

  “We present a gen­eral set­ting for structure-​​sequence com­par­i­son in a large class of RNA struc­tures that uni­fies and gen­er­al­izes a num­ber of recent works on spe­cific fam­i­lies on struc­tures. Our approach is based on tree decom­po­si­tion of struc­tures and gives rises to a gen­eral para­me­ter­ized algo­rithm, where the expo­nen­tial part of the com­plex­ity depends on the fam­ily of struc­tures. For each of the pre­vi­ously stud­ied fam­i­lies, our algo­rithm has the same com­plex­ity as the spe­cific algo­rithm that had been given before.”
  
  RNA structural-​​biology fold­ing bioin­for­mat­ics algo­rithms nudge-​​targets mod­el­ing

• [1206.3403] Topo­log­i­cal Mea­sure Locat­ing the Effec­tive Crossover between Seg­re­ga­tion and Inte­gra­tion in a Mod­u­lar Network

  “Com­pu­ta­tional analy­sis of time-​​course data with an under­ly­ing causal struc­ture is needed in a vari­ety of domains, includ­ing neural spike trains, stock price move­ments, and gene expres­sion lev­els. How­ever, it can be chal­leng­ing to deter­mine from just the numer­i­cal time course data alone what is coor­di­nat­ing the vis­i­ble processes, to sep­a­rate the under­ly­ing prima facie causes into gen­uine and spu­ri­ous causes and to do so with a fea­si­ble com­pu­ta­tional com­plex­ity. For this pur­pose, we have been devel­op­ing a novel algo­rithm based on a frame­work that com­bines notions of causal­ity in phi­los­o­phy with algo­rith­mic approaches built on model check­ing and sta­tis­ti­cal tech­niques for mul­ti­ple hypothe­ses test­ing. The causal rela­tion­ships are described in terms of tem­po­ral logic for­mu­lae, refram­ing the infer­ence prob­lem in terms of model check­ing. The logic used, PCTL, allows descrip­tion of both the time between cause and effect and the prob­a­bil­ity of this rela­tion­ship being observed. We show that equipped with these causal for­mu­lae with their asso­ci­ated prob­a­bil­i­ties we may com­pute the aver­age impact a cause makes to its effect and then dis­cover sta­tis­ti­cally sig­nif­i­cant causes through the con­cepts of mul­ti­ple hypoth­e­sis test­ing (treat­ing each causal rela­tion­ship as a hypoth­e­sis), and false dis­cov­ery con­trol. By explor­ing a well-​​chosen fam­ily of poten­tially all sig­nif­i­cant hypothe­ses with rea­son­ably min­i­mal descrip­tion length, it is pos­si­ble to tame the algorithm’s com­pu­ta­tional com­plex­ity while explor­ing the nearly com­plete search-​​space of all prima facie causes. We have tested these ideas in a num­ber of domains and illus­trate them here with two examples.”
  
  time-​​series sta­tis­tics frame­work dynamical-​​systems to-​​read

• [1206.5959] The Online Replace­ment Path Problem

  “We study a nat­ural online vari­ant of the replace­ment path prob­lem. The textit{replacement path prob­lem} asks to find for a given graph $G = (V,E)$, two des­ig­nated ver­tices $s,tin V$ and a short­est $s$-$t$ path $P$ in $G$, a textit{replacement path} $P_​e$ for every edge $e$ on the path $P$. The replace­ment path $P_​e$ is sim­ply a short­est $s$-$t$ path in the graph, which avoids the textit{failed} edge $e$. We adapt this prob­lem to deal with the nat­ural sce­nario, that the edge which failed is not known at the time of solu­tion imple­men­ta­tion. Instead, our prob­lem assumes that the iden­tity of the failed edge only becomes avail­able when the rout­ing mech­a­nism tries to cross the edge. This sit­u­a­tion is moti­vated by appli­ca­tions in dis­trib­uted net­works, where infor­ma­tion about recent changes in the net­work is only stored locally, and fault-​​tolerant opti­miza­tion, where an adver­sary tries to delay the dis­cov­ery of the mate­ri­al­ized sce­nario as much as pos­si­ble. Con­se­quently, we define the textit{online replace­ment path prob­lem}, which asks to find a nom­i­nal $s$-$t$ path $Q$ and detours $Q_​e$ for every edge on the path $Q$, such that the worst-​​case arrival time at the des­ti­na­tion is min­i­mized. Our main con­tri­bu­tion is a label set­ting algo­rithm, which solves the prob­lem in undi­rected graphs in time $O(m log n)$ and lin­ear space for all sources and a sin­gle des­ti­na­tion. We also present algo­rithms for exten­sions of the model to any bounded num­ber of failed edges.”
  
  operations-​​research plan­ning algo­rithms online-​​algorithms nudge-​​targets

• [1206.6195] Par­rondo games with spa­tial depen­dence, II

  “…Again this sug­gests that the Par­rondo region (mu_​B is non­pos­i­tive and mu_[r,s] is pos­i­tive) has nonzero vol­ume in the limit. …”
  
  Parrondo-​​games game-​​theory counterintuitive-​​results sim­u­la­tion coop­er­a­tion

• [1206.4648] Two-​​Manifold Prob­lems with Appli­ca­tions to Non­lin­ear Sys­tem Identification

  “Recently, there has been much inter­est in spec­tral approaches to learn­ing manifolds—so-called ker­nel eigen­map meth­ods. These meth­ods have had some suc­cesses, but their applic­a­bil­ity is lim­ited because they are not robust to noise. To address this lim­i­ta­tion, we look at two-​​manifold prob­lems, in which we simul­ta­ne­ously recon­struct two related man­i­folds, each rep­re­sent­ing a dif­fer­ent view of the same data. By solv­ing these inter­con­nected learn­ing prob­lems together, two-​​manifold algo­rithms are able to suc­ceed where a non-​​integrated approach would fail: each view allows us to sup­press noise in the other, reduc­ing bias. We pro­pose a class of algo­rithms for two-​​manifold prob­lems, based on spec­tral decom­po­si­tion of cross-​​covariance oper­a­tors in Hilbert space, and dis­cuss when two-​​manifold prob­lems are use­ful. Finally, we demon­strate that solv­ing a two-​​manifold prob­lem can aid in learn­ing a non­lin­ear dynam­i­cal sys­tem from lim­ited data.”
  
  sta­tis­tics inverse-​​problems system-​​identification algo­rithms nudge-​​targets bench­mark­ing

• [1203.3367] Sto­chas­tic dif­fer­en­tial equa­tions for evo­lu­tion­ary dynam­ics with demo­graphic noise and mutations

  “We present a gen­eral frame­work to describe the evo­lu­tion­ary dynam­ics of an arbi­trary num­ber of types in finite pop­u­la­tions based on sto­chas­tic dif­fer­en­tial equa­tions (SDE). For large, but finite pop­u­la­tions this allows to include demo­graphic noise with­out requir­ing explicit sim­u­la­tions. Instead, the pop­u­la­tion size only rescales the ampli­tude of the noise. More­over, this frame­work admits the inclu­sion of muta­tions between dif­fer­ent types, pro­vided that muta­tion rates, $mu$, are not too small com­pared to the inverse pop­u­la­tion size 1/​N. This ensures that all types are almost always rep­re­sented in the pop­u­la­tion and that the occa­sional extinc­tion of one type does not result in an extended absence of that type. For $mu Nll1$ this lim­its the use of SDE’s, but in this case there are well estab­lished alter­na­tive approx­i­ma­tions based on time scale sep­a­ra­tion. We illus­trate our approach by a Rock-​​Scissors-​​Paper game with muta­tions, where we demon­strate excel­lent agree­ment with sim­u­la­tion based results for suf­fi­ciently large pop­u­la­tions. In the absence of muta­tions the excel­lent agree­ment extends to small pop­u­la­tion sizes.”
  
  finite-​​size-​​effects population-​​biology noise-​​in-​​design nudge-​​targets

• [1206.5352] The Sub­word Com­plex­ity of k-​​Automatic Sequences is k-​​Synchronized

  “We show that the sub­word com­plex­ity func­tion p_​x (n), which counts the num­ber of dis­tinct fac­tors of length n of a k-​​automatic sequence x, is k-​​synchronized in the sense of Carpi. As an appli­ca­tion, we gen­er­al­ize recent results of Gold­stein. In con­trast, we show that func­tion which counts the num­ber of unbor­dered fac­tors of length n is not k-​​synchronized.”
  
  automata strings com­plex­ity nudge-​​targets

• Con­vex hull algo­rithms — Wikipedia, the free encyclopedia

  “Com­put­ing the con­vex hull means that a non-​​ambiguous and effi­cient rep­re­sen­ta­tion of the required con­vex shape is con­structed. The com­plex­ity of the cor­re­spond­ing algo­rithms is usu­ally esti­mated in terms of n, the num­ber of input points, and h, the num­ber of points on the con­vex hull.”
  
  computational-​​geometry algo­rithms nudge-​​targets

• [1205.6363] What Should Devel­op­ers Be Aware Of? An Empir­i­cal Study on the Direc­tives of API Documentation

  “Appli­ca­tion Pro­gram­ming Inter­faces (API) are exposed to devel­op­ers in order to reuse soft­ware libraries. API direc­tives are natural-​​language state­ments in API doc­u­men­ta­tion that make devel­op­ers aware of con­straints and guide­lines related to the usage of an API. This paper presents the design and the results of an empir­i­cal study on the direc­tives of API doc­u­men­ta­tion of object-​​oriented libraries. Its main con­tri­bu­tion is to pro­pose and exten­sively dis­cuss a tax­on­omy of 23 kinds of API directives.”
  
  digital-​​humanities doc­u­men­ta­tion text-​​mining software-​​development cultural-​​norms

• Pub­li­ca­tions Avail­able Electronically

  God­fried T. Tou­s­saint, “The Erdos-​​Nagy the­o­rem and its ram­i­fi­ca­tions,” Proc. 11^th Cana­dian Con­fer­ence on Com­pu­ta­tional Geom­e­try, Van­cou­ver, Canada, August 16–18 1999, pp. 9–12. Long ver­sion avail­able at: http://​www​.cs​.ubc​.ca/​c​o​n​f​e​r​e​n​c​e​s​/​C​CCG. Also: Tech­ni­cal Report No. SOCS-99.2, School of Com­puter Sci­ence, McGill Uni­ver­sity, June 18, 1999.
  
  nudge-​​targets geom­e­try genetic-​​programming-​​target low-​​hanging-​​fruit

• Intro­duc­tion to Lam­ina Emer­gent Mech­a­nisms (LEMS) | Com­pli­ant Mechanisms

  “The fact that LEMs can be fab­ri­cated from pla­nar lay­ers influ­ences both what processes can be used for their man­u­fac­ture and what mate­ri­als may be used in their con­struc­tion. At the micro level, LEMS can be fab­ri­cated using single-​​layer MEMS fab­ri­ca­tion meth­ods and mate­ri­als, which offers sig­nif­i­cant cost and reli­a­bil­ity advan­tages. It also pro­vides oppor­tu­ni­ties for com­plex out-​​of-​​plane motion with only a sin­gle layer. At the macro level, man­u­fac­tur­ing processes used to make sta­tic struc­tures or com­po­nents for assem­bly can be used to cre­ate mech­a­nisms capa­ble of sophis­ti­cated motions and com­plex tasks. Example processes include stamp­ing, fine blank­ing, laser cut­ting, water jet cut­ting, plasma cut­ting, and wire elec­tri­cal dis­charge machin­ing (EDM). Some of these processes, such as stamp­ing, offer sig­nif­i­cant cost advan­tages for high-​​volume pro­duc­tion. Pla­nar fab­ri­ca­tion also allows the use of sheet goods to directly cre­ate mech­a­nisms. The use of low-​​cost, high-​​quality sheet goods has the poten­tial to dra­mat­i­cally reduce cost for high-​​volume pro­duc­tion. It also makes pos­si­ble the next char­ac­ter­is­tic: flat ini­tial state.”
  
  man­u­fac­tur­ing engineering-​​design fab­ri­ca­tion nudge-​​targets