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i have old audio amplifier (jvc a-gx2b) produces crackling noises on 1 of outputs. so, opened , discovered 2 largest capacitors seem leaking : can replace capacitor same characteristics (4700uf 50v), or should instead take specific capacitors audio? if yes, ones ? in addition, have interest replace capacitors of amp (not 2 largest)? 1: wear safety gloves when handling toxic leaky capacitors, remove , clean safely isoprop. , mark note polarity (-) 2 : measure dia , lead pitch dxl [mm] sort parts this 3: audio or better low esr, highest ripple current caps. < 50mohm, > 3aripple 4: better caps run cooler lower esr , rated higher temp. may not fit. 5: japanese caps have better reliability i suggest 1st choice panasonic @ digikey .. cost of shipping may more cost of caps. as suggested: cap voltage must same or more - capacitance tolerance doesn't matter, , may larger value. - large e-caps may replaced @ same time.

i attempted make myself 2-in-1 programmer can program both at89cx051 , at89s52 on same board without having plugging/unplugging of port. the main issue strobe pin aka reset (rst in circuit). (pin 1 of db25 connector). tested pc , got no results. what seems work if connected rst vcc via 1k resistor. works because though output @ 3.8v instead of 5 (which vcc at), puts at89s52 in reset mode expected, i'm not getting 12v @ pin 1 of small at89cx051 socket. if don't make manual connection, 1.4v measured @ rst, after added 10k resistor between vcc , rst. without rst being forced ground, should 5v i'm not. i have tested transistors manually leg leg using diode setting on multimeter , turned out fine. resistors going base of transistors 2.2k , used 1k resistors in place of diodes. other resistors 10k. resistor going buffer (74hc125) 0 ohm. all capacitors 0.1uf. why getting such awkward voltages reset pin? using weak of resistors or something? update so ended ma...

below want select , edit bottom wire of 3 parallel wires: but when click on bottom wire program selects middle wire because share same net. is possible single out desired wire segment without selecting entire net in altium? yes you need use "break wire" feature first - split wire up. think it's in "edit" menu.

is ib current correct went kvl through first transistor your forgetting re. you need use effective resistances r4 , r6, value \$r4_e = r4 * (1+\beta) = 40,000 * 101 = 4,040,000\omega\$ \$r6_e = r6 * (1+\beta) = 1,000 * 101 = 101,000\omega\$ using base circuit looks this. simulate circuit – schematic created using circuitlab you solve using various methods, shortcut realise that, ideal vbe, voltage @ top of both emitter resistors identical. such can treat both legs being in parallel. circuit can further simplified to.. simulate circuit now should able calculate current through circuit as.. \$i_{rb} = (2.6 - 0.6)/(2,260 + 98,540) = 19.84ua\$ that makes base voltages both.. \$v_b = 2.6 - 19.84ua * 2.26k\omega = 2.555v\$ so \$ib1 = (2.555-0.6)/4.04m\omega = 0.484ua\$.. , \$ib2 = (2.555-0.6)/101k\omega = 19.356ua\$ however: these numbers make sense if transistor not saturated. question states \$i_e \approx \beta * i_b\$ indicates ...

i'm trying make push-pull audio amplifier pair of power darlingtons (tip142 , tip147), i'm having problems biasing. here's diagram of 1 of configurations: here i'm using 3 diodes, used different things in place try correct biasing voltage. with biasing voltage lower 2.2 v (between bases of transistors) has crossover distortion, because there'll small parts of signal none conducting. with 2.2 v or more, both conducting , there's no more distortion, there's problem: current flowing between them escalates heat until take on fire (being starting current isn't great , they're on large heatsink, heatsink doesn't have time heat, fast happens). they're stable biasing voltages lower 2.1 v, there's distortion. the components heating here output transistors, i've cheked , none of resistors or diodes heating up. i've checked if negative feedback help, didn't, because voltage in output doesn't change current flowing t...

i have apc ups 9 ah battery. would ok replace 18 ah battery? i realize modifications needed since won't fit in case. in theory shouldn't matter how bigger ah rating of battery long regulate current , voltage same. takes long transfer coulombs of charge. bigger battery of same chemistry have larger capacitance , may have lower esr.

i have no experience of dealing pcb manufacturers except time once used pcbway's service. know if there standard pcb board sizes 1 needs create when getting custom pcb made? my basic idea not incur cost loss of material pcb manufacturer faces. example, let's use board of 10*10 inch manufacture , submit custom board request dimension of 7*7 inch, increase cost of pcb? sometimes pcb makers have per-panel price. tell size using..or more importantly, area have work with-- usable area (not panel size) @ least 10" x 16", maybe 10.5" x 16.5" or bit more. small panel. large production believe larger panels more typical. typically phenolic single sided boards use larger panel sizes. this reference lists typical standard pcb panel sizes follows: panel borders (maybe 0.5" on each side) take away area. it not particularly important unless pcbs (or self-panelized pcbs) getting size few panel- materials not biggest part of pcb cost in prototype...

i'm trying find "same or better" equivalent replacement 747 opamp. footprint / pinout can different, don't mind. using parametric search on arrow, while reading datasheet 747 found lt1355 might replacement. however, quite expensive; $16.89 1 single ic (dip package). searching lt1355 on octopart shows arrow cheapest one, price steep me. i'm fine around $8/pc. what other dual opamps can serve replacement 747? usually asking products/parts off-topic since can benefit wants better 741, i'm making exception. there literally hundreds of suitable 741 replacement opamps. the parts list waaaay expensive. have special properties few designs need. you should not looking 741 replacement per sé more "generic opamp". there usable opamps had less money. lm358, 10 1 euro (shipping included!) on ebay other examples: mcp602, ca3140, tlc271 most of these have versions 1, 2 or 4 opamps in 1 housing. you have compare datasheets see suits ...

i know in magnitude spectrum of single square dc pulse (0-8v) lobes 0 @ frequencies $$\frac{1}{t},\frac{2}{t},\frac{3}{t},...etc. $$ t=pulse duration. if square pulse goes -2v 6v, formula 0 points of spectrum still same, ie. $$\frac{n}{t}$$ n=1,2,3... etc. , t=pulse duration? what difference? applying offset signal change spectrum @ dc (frequency of 0hz). if single square pulse goes 0v 8v, value of dc \$\mathcal{f}\{ f(t)\}|_{\omega=0}=0\$. if square wave goes -2v 6v, \$\mathcal{f}\{f(t)\}|_{\omega=0}=-2\cdot\delta(0)\$.

can sample , recover signals non infinite "length" using nyquist shannon theorem? example if have signal $$ x(t)= u(t+5)-u(t-5) $$ , know sampling period t less 10s (t<10). can recover using nyquist theorem? if not , recover it? edit: have taken fourier transform of signal , : $$x(ω)=2i(\frac{1}{iω}+πδ(ω))sin(5ω)$$ can lead finding period $$\frac{2π}{5} $$ , see if f>= 5/π can recovered. may not possible because used theorem although on finite signal no need think "finite length". though continuous time signals defined infinite time interval, in practice analyse in finite interval only. x(t) defined in interval [-5 5]. the frequency domain representation of such signal infinite bandwidth sinc function. hence not possible define particular sample rate per nyquist theorem, reconstruct without losing information. can sample definite sample rate, implicitly band limits signal. sampled signal after reconstruction through dac , lpf, not pe...

hello have transformer ebay north court 50 amplifier. there not information online. has 400 0 400 volt ht think ran pair of kt66 valves gz34 rectifier dimensions l x b x h 4" 3" 4" if can me out on 1 great the main determiner of transformer power rating material , cross-sectional area of core. sets power level @ core saturate, , manufacturers don't want use more steel absolutely have to. as rough estimate, since these transformers use same kind of steel laminations , same relative geometry, sufficient make judgement based on volume/mass of core. since core majority of total mass of transformer (the windings tiny fraction), weighing enough, why marko made comment.

i using tps61021 boost converter ic increase input voltage 1.2v 3.3v. have designed boost converter application called ti webench. input voltage: 1.2v output voltage: 3.3v min current: 300ma the pcb have designed, measuring 3.3v, efficiency pathetic. below 25%. in bom, ti webench software recommends using 10uf 10v capacitor, using 10uf 6.3v. not able understand why efficiency low? datasheet inductor . below in tabular format have written current values have measured multimeter. fig.1 measurement of current @ different load resistance. fig.2 ti webench application output fig.3 schematic design of boost converter pin = 1.2v × 570ma = 684 mw pout = 3.3v × 105 ma = 346.5 mw efficiency = pout/pin = 346.5/684 = 50.7% how on earth did come 18.42%? similarly, 64% , 70% other 2 loads. these numbers sound pretty me @ these voltages. did webench give efficiency estimates specific configuration?

according miller effect, within amplifying devices such transistors have inverting voltage gain higher one, there should increased input capacitance increased voltage gain of amplifier. i has been said effect limiting amplifier @ higher frequencies. comes incorporation of method of increasing transistor's bandwidth. 1 of them dominant pole compensation. according wikipedia: "when capacitor introduced between input , output sides of amplifier intention of moving pole lowest in frequency (usually input pole) lower frequencies, pole splitting causes pole next in frequency (usually output pole) move higher frequency." i part when states 2nd pole should moved higher in frequency (that 2nd roll-off), why heck want decrease 1st pole , consequently first gain roll-off begins @ lower frequencies before. what point of it? i mean, shouldn't desired gain vs. frequency curve flat possible, long possible - higher frequencies? addition of capacitor betwee...

hi can make tone control circuit on arduino using lm386 , if not other ic used please me out? tone control circuit in audio system variable filter. it's used boost frequencies, attenuate other frequencies , let others is. purposes of such filtering: creative sound modifying (=adjustments subjectively result) compensating uneven frequency response of equipment , room, based on mesurements today high quality complex filtering possible in digital domain. signals ad-converted , filtering made calculations. arduino unfortunately slow , has low resolution ad conversion serious real time digital audio signal processing. if search "dsp arduino", audio examples @ best music or other sounds played through old-fashioned analog long distance phone line. thus arduino digital audio signal processor isn't serious option - except if have signal stored digital data , allow @ 10...100 times longer processing time duration of signal. in case use pc , excel or matla...

hello have cheap ftdi going recreate on pcb can flash atmega2560 chip onboard, ftdi has dtr line pulled low when sequence starts stays low instead of going low high after 1ms 50ms, need find out how create simple circuit when pulled low goes high, how can this, have simple components hand. my stocked parts: 103 ceramic caps 25uf aluminium caps 220uf aluminium caps some blue ceramic caps labeled "10" practically common resistors values 5v zener diodes 5v switching diodes npn transistors n channel mosfets 5v reflecting diodes can make using ? else can what's needed. many thank edwin sorry it's atmel atmega 2560 chip on pcb have serial lines , reset,5v,ground , 2 gpios on pin out. can flash ftdi. , ftdi dtr line stay low , need pluse rest line need figure out how use low signal pull reset low high right after. if try on arduino mega or uno holding down reset not work it's pulse going low high load boot manager. hence dfti dtr...

i establishing database students , courses using erd. style of erd using similar diagram below erd diagram question : note: picture above not erd, style of erd using. a simple create statment used attributes of each entity, other ddl statements enforce relationships, weak entities, , multi-way relationships? the way can enforce relationships between tables creating foreign key referencing primary key other table. both keys defined either creating or modifying table using create statement or alter statement, respectively.

i use postgresql 9.6.6 on centos linux 7.4 , after upgrading postgresql-jdbc package - # sudo yum update failed set locale, defaulting c loaded plugins: fastestmirror loading mirror speeds cached hostfile * base: mirror.fra10.de.leaseweb.net * epel: mirror.wiuwiu.de * extras: centosmirror.netcup.net * updates: mirror.wiuwiu.de resolving dependencies --> running transaction check ---> package java-1.8.0-openjdk.x86_64 1:1.8.0.151-5.b12.el7_4 updated ---> package java-1.8.0-openjdk.x86_64 1:1.8.0.161-0.b14.el7_4 update ---> package java-1.8.0-openjdk-headless.x86_64 1:1.8.0.151-5.b12.el7_4 updated ---> package java-1.8.0-openjdk-headless.x86_64 1:1.8.0.161-0.b14.el7_4 update ---> package postgresql-jdbc.noarch 0:42.1.4-1.rhel7 updated ---> package postgresql-jdbc.noarch 0:42.2.0-1.rhel7 update ---> package postgresql-jdbc-javadoc.noarch 0:42.1.4-1.rhel7 updated ---> package postgresql-jdbc-javadoc.noarch 0:42.2.0-1.rhel7 update --> finished depende...

is there limit number of listeners can created using sql server standard? i'm working dba has set 2017 standard server, cu3. have 12 databases, , able set 12 basic availability groups. able set 10 listeners, on 11th, getting error below: create failed availability group listener 'test12300'. (microsoft.sqlserver.smo) for help, click: http://go.microsoft.com/fwlink?prodname=microsoft+sql+server&prodver=14.0.17213.0+((ssms_rel).171128-2020)&evtsrc=microsoft.sqlserver.management.smo.exceptiontemplates.failedoperationexceptiontext&evtid=create+availabilitygrouplistener&linkid=20476 additional information: an exception occurred while executing transact-sql statement or batch. (microsoft.sqlserver.connectioninfo) the wsfc cluster not bring network name resource dns name 'test12300' online. dns name may have been taken or have conflict existing name services, or wsfc cluster service may not running or may inac...

i want create database program. use sqlite, although others option. i have columns a , b , c , d . a unique , primary key. b , c , d allowed contain duplicate value. however, don't want combinations of b , c , d repeat. instance, sample valid db: a b c d 0 18 n kiwi 1 12 v kiwi 2 15 t orange 3 12 j kiwi 4 12 t banana 5 31 f apple 6 10 h kiwi 7 15 y orange 8 20 b apple 9 1 m grapefruit 10 7 s apple 11 4 h banana 12 31 t egg sample invalid db (rows 2 , 7 ): a b c d 0 18 n kiwi 1 12 v kiwi 2 15 y orange 3 12 j kiwi 4 12 t banana 5 31 f apple 6 10 h kiwi 7 15 y orange 8 20 b apple 9 1 m grapefruit 10 7 s apple 11 4 h banana 12 31 t egg is there standard database rule or concept applies this? i can of course validation in code, manually querying db. believe construct fifth bcd column, concatenates other three, , required un...

(this not production database. i'm practicing in staging enviroment.) i'm trying set rman backup/recovery. i did full backup, seems in state. i did archivelog backup, went well. , then, (here's f***ed up), i... created new tmp directory. ran rman archivelog only backup tmp directory destination changed mind , deleted tmp directory. i realize rman keeps track of paths written backups , can't go around , delete these files! now, after do run { restore database; recover database; } i get ora-27037: unable obtain file status linux-x86_64 error: 2: no such file or directory additional information: 3 failover previous backup rman-00571: =========================================================== rman-00569: =============== error message stack follows =============== rman-00571: =========================================================== rman-03002: failure of recover command @ 01/19/2018 20:21:01 rman-20506: no backup of archived log fou...

i have following query: alter procedure [dbo].[spsearchclient] @searchwords nvarchar(max) = null, @lowerdate date = null, @upperdate date = null, @usercreated nvarchar(450) begin set nocount on; declare @useraccountid smallint declare @searchwordcount int select @useraccountid = dbo.fngetuseraccountid(@usercreated) create table #searchwords ( id int identity(1,1), word nvarchar(50) ) insert #searchwords ( word ) select value string_split(@searchwords, ' ') trim(value) <> '' select @searchwordcount = @@rowcount; select c.clientid, c.firstname, c.lastname, c.fullname, c.dateofbirth, g.gendername, g.gendericon, c.verificationcode, v.lastvisitdate client c outer apply ( select max(startdate) lastvisitdate visit v ...

i have stored procedure calculates distance between 2 coordinate points: create proc loc.calcdistancebypostalcode ( @from varchar(10), @to varchar(10) ) begin declare @data table (from_place varchar(200), from_region varchar(200), "to_place" varchar(200), to_region varchar(200), distance decimal(8,2)) declare @postal1 table (id int identity(1,1), place_name varchar(200), region_name varchar(200), latitude decimal(12,9), longitude decimal(12,9)) declare @postal2 table (id int identity(1,1), place_name varchar(200), region_name varchar(200), latitude decimal(12,9), longitude decimal(12,9)) insert @postal1 select distinct l.place_name, l.region_name, l.latitude, l.longitude loc.locations l cross join loc.locations_postal lp postal_code @from , lp.city_id = l.id insert @postal2 select distinct l.place_name, l.region_name, l.latitude, l.longitude lo...

so, task prove following: if s schedule containing @ 1 write action, s conflict-serializable. the answer yes, disagree, because following schedule contains @ 1 write action, , not conflict-serializable: r1(a), r2(a), w2(a), r1(a). am wrong? or answer wrong?

i work small technology msp. having completed bachelor's in information science, focus in data science, boss has asked me build data warehouse (i think means data mart have read). i've been realizing education heavy on coding, math/stats, , ml aspect of data pipeline, light on data preparation aspect, claimed take 80% of time, opportunity me learn how of tidy data sets i've been analyzing come existence. we have 2 main systems, respectively run sql server (~60 gb), , mysql (~80 gb), , few other data sources come in csv. @ point, want simple asset reporting our clients, , simple pricing analysis of our monthly fees (e.g. boss has no idea costs support client's server per month, our prices best guesses). at point, main problem don't know don't know. i'm reading "the data warehouse toolkit" kimball, , taking edx.org course in t-sql microsoft. co-worker has small bit of experience in area, , says should figure out tables need our 2 main system...

i getting these errors on dedicated server because of database goes recovery mode. i have seen following error in sql server error log file: 2018-01-20 05:32:19.83 spid7s logwriter: operating system error 1117(the request not performed because of i/o device error.) encountered. 2018-01-20 05:32:19.83 spid7s write error during log flush. 2018-01-20 05:32:19.84 spid284 client unable reuse session spid 284, had been reset connection pooling. failure id 46. error may have been caused earlier operation failing. check error logs failed operations before error message. 2018-01-20 05:32:19.84 spid335 database newtrack shutdown due error 9001 in routine 'xdesrmfull::commit'. restart non-snapshot databases attempted after connections database aborted. 2018-01-20 05:35:03.35 spid22s recovery completed database aa(database id 7) in 151 second(s) (analysis 18856 ms, redo 115386 ms, undo 2023 ms.) informational message only. no user action required. at same ti...

i have data warehouse one-to-many relationship: "fact" table contains: product_group_id "product_bridge" table contains: product_group_id, product_id "product" table contains: product_id, product_name, other product attributes.. i've inserted data relevant tables, how can query database , retrieve products product group in 1 row result? i've never used bridge table before , not find decent/helpful examples online how query between bridge/fact/dimensions. i.e. desired result like: product_group_id product_id product_name product_id_1 product_name1 product_id_n product_name_n any suggestions appreciated. based on example output can use listagg. basic query can add whatever other criteria is; select distinct (p.product_group_id ||' '|| listagg(c.product_id||' '||c.product_name, ' ') within group(order p.product_group_id, c.product_id) ...

i using mysql innodb cluster. connect instance use \c root@localhost:3306 . error message pops out when issue var cluster = dba.getcluster('testcluster') . i've created cluster in last session. when reconnect not work anymore. the thing changed hostname localhost db005 , restart mysql server. don't know if has problem. has idea happened? did searches on google. seems resource mysql forum. still not able solve problem. https://forums.mysql.com/read.php?177,653826,657465#msg-657465 thx!

100 year old brick house new front door. thee door awesome @ stoppiing cold, there space under door cold still comes in. put fiberglass pink insulation in there, didn’t much. think need stop air flow better. one option fill spray foam. i’m not sure if want glued eternity. , believe should fill cracks, not voids. another cut piece of plastic , glue/caulk along front (so insulation behind). any other ideas? that opening sealed off riser. make sure it's tight fit no gaps. horizontal pieces extend farther framing, add wood extend vertical framing make 4-sided box riser mounts against. caulk between riser , threshold "box" seal it. beyond that, fiberglass batting show should fine fill space.

i have existing junction box in attic powering exhaust system in summer. wire 12-2 , dedicated line, nothing else on it. putting bathroom on 3rd floor , have fan/heater/light combo run 12-3 unit switch. can connect 12/3 wire in junction box 12-2 wire power not have take 12-3 way breaker box? unit have 3 switches. it not number of conductors load. under best of conditions #12 can carry 15-amps extended period of time. check power requirements of heat-fan-light. amp draw attic ventilator. add together. if can stay under 15-amps ok. wire on. need 12-4 between control switch , new heat-fan-light or 1 12-3 , 1 12-2. need 1 12-2 between junction box , heat-fan-light.

i dealing fixture in photo. there 2 water inlets, 1 washing machine, , 1 dish washer. bottom valve opens , closes water flow to bottom pipe. however, top valve seems have no effect whether open or closed , nothing drip comes out of top pipe. working few days ago until shut off top valve fit new dishwasher. the turning mechanism of top valve seems light , thinking perhaps have broken loose valve valve shut regardless of position of handle. feasible? would appreciate pointers regarding waterflow problem , how resolve. thanks. it's possible valve has failed or blocking it. @ point, best bet turn off water upstream , remove valve. watch might have come loose somewhere , clogged up. should able shine flashlight in 1 end , see light looking in other. when valve open, see light, , closing valve darkens side opposite flashlight. if moving valve has no effect, benefit replacing it.

my garbage disposal empties trap. before trap, other sink drain joins vent tee. assuming in incorrect. occasionally, trap not empty fast enough , water + food climbs horizontal run of pipe, causing clog. assuming need replace vent tee sanitary tee. my problem can not find replacement sanitary tee has top threaded. can not find male adapter maintains proper diameter. seeking advice on how redo this. come think it, plumbing arrangement allowed? waste other drain, along dishwasher discharge flows line disposal. isn't other way around? try replacing tee sanitary tee. use couplers create threaded ends on tee.

i have kenmore 40318900 front loader started giving le error(motor stall). bought display model 5 years ago. tub spins freely hand, started troubleshooting according tech manual found inside(quite convenient) , said stator bad due resistance being way out of spec. took stator out , 100% sure measured windings directly, , lo , behold fine, around 8 ohms each. figured in harness , sure enough 1 of wires had 1.2k ohms between stator pin , pwb connector. started following wire harness , found melted , burnt section. while going through machine noticed 1 of 3 shock absorber missing mount pin. looked on laundry room , turned machine on it's side , found, no broken pieces. thought must've never been installed. washer has been pretty noisy , vibrates around on tile floor. hypothesis excess vibration may have frayed strands in wire , caused overheat due current flowing through lot less copper. fix should simple wire replacement, wanted opinions before power , risk fire. thoughts?...

i installing wall mounted light fixture. fixture can either plugged wall outlet or hardwired outlet. choosing plug fixture wall outlet. in addition cord/plug, there ground wire on fixture. i ground wire if fixture going hardwired, not i'm planning do. do ground wire. installation instructions address ground wire in context of hardwiring. can leave ground wire is, can cut off? i coil neatly , not cut off. knows, might decide install "wired" sometime down road. your plug being 2-prong (no ground), still tempted ground it.

hello, all. i'm designing dining room table, here mocked real size in 2x4s , plywood, prior final construction out of maple. table top 48" square, , base has outer dimensions of 24" x 24". we're putting int corner bench arrangement, want avoid legs on corners, started out pedestal design, have moved sort of trestle. my challnge inherent tippiness of design: lean down hard on edge, , thing tips. (see bottom right image) constraints: knee clearance means can't push trestle wider. maple vs pine make whole thing more massive, help. also, intend double thickness of legs, 1.5" 3". again, more wood = more mass. any thoughts on design improvement? thanks, dave the inset edge of table legs in either direction way bigger needed. main clearance knee room, persons feet can move around object lot easier. if have 16" offset edge of table legs end, more room need although if practical, nice, table needs work. 12" number work start,...

i replaced shower cartridge , after turning water on got water hammer sounded in wall every time turned water in part of house on or off! i've never had issue before , bang 5 times after shutting water off in anywhere in bathroom or other bathroom on other side of wall. drained pipes several times replenish air stops nothing helped. talked few plumbers , no 1 figure out... good news!!! after reading post halving trouble danco replacement went out , bought moen cartridge , water hammer went away! works perfect!! must have been cheap/faulty danco cartridge

we have 60 year old wood venetian blinds we're in process of replacing ladder tape on (that easy find). 1 of our blinds missing small wooden roller , we're @ loss find one. it's approximately 1/2" long, 5/16" wide, , has 3/8" hole. i'm attaching pictures. while i'd prefer wood, i'm ok other materials never seen. a quick google search produced more modern styles. i know route might more expensive - seems such simple part make. cabinet shop or furniture repair can that. if myself out lathe - buy wooden dowel rod big box hardware. cut down 3 inches. drill out center, , countersink center. use sand paper , file shape own matching roller. stain , done it. tedious yes sure - have roller. if have small drill press better - because put dowel in drill press , use dremel tool cut , sand have need , make lickity split. should done in 30 minutes or so.. below not endorsements of products or services provided useful information.. ...

is there possible mold growth going on ? leak has been on going 6 months. it leak inside wall lasting 6 months result in mold ( not saying there or not ). there no way tell unless opens wall. must done care presuming there mold , taking proper safety precautions. have informed landlord suspect mold , ill health effects result of mold due leak? do not assume or assert landlord health problems result of mold, inform them concerned , investigating. tell landlord going doctor see if symptoms result of mold growing in wall because of leak has not been fixed as requested . in his/her best interest investigate , mitigate health hazards on property lead financial repercussions them. may or may not enough motivate landlord deal issue. regardless of cause of health issues still need landlord address leak ( , make clear them ) if can not afford attorney contact local city ombudsman see if can advise (or intervene) on tenant/landlord rights , laws of town/city. keep rec...

the outlet on front panel of electric stove 3 prong , have been using coffee maker. because i've been looking wiring codes regarding issue, see coffee makers/toasters/kettles should on 20amp circuit 12 gauge wiring. so, i'm wondering if safe practice plug coffee maker stove outlet. i'm thinking why put outlet on stove if can't use small appliance... (it's quite old stove.) also, safe plug kettle or toaster outlet wired 14 gauge wire , 15 amp circuit breaker? thanks. the reason safe plug small appliances these kinds of outlets because wiring enclosed in frame of stove , possibly high tempature rated insulation there 1 15amp outlet. house wires sized protect insulation wire can handle more 5x max code value insulation starts melting. house wired many plugs in parallel. far these devices needing on 20 amp circuit not true no appliances require 20 amp circuit , if 1 blade 90 degrees. normal 15 amp plug can not plugged 15 amp outlet. current code require...

i did read through other questions , answers before posting question. i know solenoid fine clicks when connect 24v. 2 wires (brown , blue) coming controller has 27v regardless of settings on control switch (dial) - when on off position. firstly, should there voltage on on these 2 wires always? thought have voltage when controller wants turn on humidifier , let water flow. wires controller go inside connector plug. there 2 yellow wires come out , connect solenoid. there no voltage on yellow wires going solenoid. kind of hard check if fan turning on. put mark on 1 of fan blades. shows fan never moved. maybe connector plug on fan side not snugly fit plug on humidifier side. hard verify connects when snap in fan side. ok after typed above found out if unplug fan part 110 outlet, there no current in 2 wires said above. me not make sense. if fan part of unit supplying power controller! or missing here. in prev house had simple rotary humidifier. any appreciated. thanks....

i'm hunting alternative fuel sources other norm(propane, elec, natural gas) , i've been looking alcohol due fact live legal distill personal use , , although never drink such product inexperienced in process , not wish go blind methanol, have access fields of corn ... makes me curious if use corn alcohol complied on summer me through winter. question has tried nat gas conversion alcohol in boiler .... know burn temps relatively close , i'm assuming maybe able custom build orafice alcohol might fit may pipe dream . otherwise i'm looking concepts alcohol furnace or info on manufacturing them @ moment, ss (self sustainable) household in northeast grateful. thank you

the gamma function (over $\mathbb{r}$) allows express factorial function euler integral : $$ n! = \int_0^\infty x^n \, e^{-x} \, dx $$ happens if use trapezoid rule on improper integral on right hand side? general functions says: $$ \int_a^b f(x) \, dx \approx (b-a) \left[ \frac{f(a)+ f(b)}{2} \right] $$ can partition $\mathbb{r}_{\geq 0} $ union of segments $[n,n+1]$ on possible integers $n \geq 0$. therefore: $$ a! \approx \sum_{m \geq 0} 1 \cdot \frac{m^a \, e^{-m}+ m^{a+1}e^{-(m+1)}}{2} = - \frac{1}{2} + \sum_{m \geq 0} m^a e^{-m}$$ how bad trapezoid rule in kind of estimate? error term usually: $$ \left|\; \int_a^b f(x) \, dx \;- \;(b-a) \left[ \frac{f(a)+ f(b)}{2} \right] \; \right| \leq \frac{(b-a)^3}{12}f''(\xi) $$ so each term losing $\frac{1}{12} \times \text{constant}$. can understand error term better? related: an elementary proof of error estimates trapezoidal rule d. cruz-uribe , c. j. neugebauer

this derived $s_a=\sum_{i=0}^m(n+ai)=\frac12(m+1)(2n+am)$, $(n,m)\ge1$ when $a=3$ a number works number $n,m$ plugged $s_a$ result in number. $[n,m]=[1,2]$ plugged $s_1=6$, 6 works $s_1$ note: if $a=1$, $s_1$ can every number not power of $2$, , never power of $2$. if $a=2$, $s_2$ can every composite number never prime. i found same reasons $s_1$ can never power of $2$, $s_3$ can never power of $2$ i found $s_3$ can every odd number greater $4$($5$ being smallest number $s_3$ can ever be) because $(n)+n+3=2n+3$, if n positive, generate every odd number greater $4$. i found numbers generated $s_3=\{5+2x\}\cup\{12+3x\}\cup\{22+4x\}\cup\{35+5x\}\cup\cdots\cup\{\frac12(3k^2-k)+kx\}\cup\cdots$, $x=\{0,1,2,3,\cdots\}$ i used find numbers didn't work: https://www.desmos.com/calculator/ebklyzijdy $s_3\ne1,2,3,4,6,8,10,14,16,20,28,32,44,52,64,68,76,88,104,128,136,152,184,208,232,248,256,272,296,304,328,344,368,464,496,512,592,656,688,736,752,848,928,944,976,992,1024,1072,11...

in 1st lecture of mit ocw differential equations course , at around 25th minute, example y’=-x/y visualized multiple isoclines, intersect @ (0,0). @ (0,0) has multiple (possible?) slopes. also if substitute (0,0) y'=-x/y or rather y*y'=-x, 0*y’=0, true slope y’. but @ 37:45, professor argues "you can’t have 2 slopes" [at same point]. can resolve contradiction? an ordinary differential equation has form $$y'=f(x,y)\qquad\bigl((x,y)\in\omega\bigr)\ ,$$ whereby given function $f$ defined , continuous in region , i.e. connected open set $\omega\subset{\mathbb r}^2$. if $f$is given "analytical expression" in variables $x$ , $y$, in example, tacit understanding should take $\omega$ maximal region $f$ defined , continuous. $f(x,y):=-{x\over y}$ undefined when $y=0$. therefore can take $\omega$ either upper or lower half plane of ${\mathbb r}^2$. both choices $f$ defined , real analytic on $\omega$. if take $\omega$ upper half plane soluti...

let $g$ finite group has $g$-module $\mathbb{q}/\mathbb{z}$. note $\frac{1}{n}\mathbb{z}/\mathbb{z}$ $n$-torsion subgroup of $\mathbb{q}/\mathbb{z}$. it purpose give map $h^{i}(g;\mathbb{q}/\mathbb{z})$ $h^{i}(g;\frac{1}{n}\mathbb{z}/\mathbb{z})$. as singular cohomology coefficients, attempt use tensor product $\otimes\frac{1}{n}\mathbb{z}/\mathbb{z}$. however not sure right method it. thank time , effort.

let $k \subseteq l$ finite separable field extension. ($k$ infinite. not mind assume $k$ of characteristic zero). assume $a,b \in l$ 2 primitive elements extension, namely, $l=k(a)=k(b)$. is there criterion tells when $ab$ primitive element extension, namely, $l=k(ab)$? remarks: (1) primitive element theorem, $a+\lambda b$ primitive element, infinitely many $k \ni \lambda$'s, asking product not sum. (2) in few examples have in mind, $ab$ not primitive element, example: $a=i,b=-i,k=\mathbb{r},l=\mathbb{c}$; $a=\sqrt2,b=-\sqrt2,k=\mathbb{q},l=\mathbb{q}(\sqrt2)$; $a=\frac{-1+\sqrt3 i}{2},b=-\frac{-1-\sqrt3 i}{2},k=\mathbb{q},l=\mathbb{q}(\sqrt3 ,i)$. extensions splitting fields of $t^2+1$, $t^2-2$, $t^2+t+1$, respectively; guess in order find extensions $a,b,ab$ primitive higher degrees polynomials required. thank much! edit: (1) have found this paper , may (though deals $k$ finite). (2) perhaps this question relevant. (3) comments this quetion show answer ...

can compact operator in $h=l^2$ have infinite rank , infinite kernel? guess no because such operator has more countable eigenvalues. i don't understand why such operator should have more countable eigenvalues. way, think possibile, take: $t : h \to h$ $(tx)_n = \begin{cases} 0 \quad \quad \,\,\,\text{if $n$ odd} \\ n^{-1}x_n \quad \text{if $n$ even} \end{cases} \quad \forall n \ \in \mathbb{n}$ then $ker(t) = \{ x \in h : x_{2k} =0 \quad \forall k \in \mathbb{n}\}$ $im(t) = \{x \in h : \exists k \in \mathbb{n} :x_{2k}\ne 0 \}$ which both infinite dimensional, $t$ compact since limit of finite rank operators.

basically title says. can provide proof space of holomorphic functions on open subset $u \subset \mathbb{c}$ equipped compact-open topology (a.k.a. topology of compact convergence) second countable? according professor should true.

the integral $\int (t^2 - 1)^{a} \cdot t^{b} \cdot \log(t)\,dt$ has following solution in terms of hypergeometric functions according wolfram: the solution has been check extensively. have tried use integration parts, did not find references on integral leading hypergeometric function resources. does know how final solution in terms of 2 hypergeometric functions? i got answer in terms of hypergeometric functions correct numerically , can transformed answer wolfram gives. the answer (i omit constant): $$\int t^b (t^2-1)^a \ln t~dt= \\ = \frac{t^{2a+b+1}}{2a+b+1} \bigg( (\ln t) {_2 f_1} \left(-a,-a-\frac{b+1}{2};-a-\frac{b-1}{2}; \frac{1}{t^2} \right) - \\ - \frac{1}{2a+b+1} {_3 f_2} \left(-a,-a-\frac{b+1}{2},-a-\frac{b+1}{2};-a-\frac{b-1}{2},-a-\frac{b-1}{2}; \frac{1}{t^2} \right) \bigg)$$ the formulas used (per wikipedia hypergeometric function , generalized hypergeometric function ): $$\mathrm {b} (b,c-b)\,_{2}f_{1}(a,b;c;z)=\int _{0}^{1}x^{b-1}(1-x...

i guidance here field of math or theorem into. have problem trying predict optimum solution. have n tries guess solution m total number of possible solutions , n less m. how go creating n solutions have best chance cover best solution given predictions solutions accurate possible? don't need answer necessarily. reference might able research subject great. you may find decision theory useful. includes study of how make best choices under uncertainty. https://en.wikipedia.org/wiki/decision_theory

this problem romanian g.m. , although short, (i think) hard. let $x, y, z$ real non-negative numbers such $x+y+z=3$. prove $$27 \leq (x^2+2)(y^2+2)(z^2+2) \leq 44 $$ i didn't succeed in of inequalities, managed find equality cases ($x=y=z=1$ first 1 , 1 of them $3$ , others $0$). hint/idea/solution welcome. for proof of left inequality it's enough prove $$(x^2+2)(y^2+2)(z^2+2)\geq3(x+y+z)^2,$$ true reals $x$, $y$ , $z$. the proof see here: contest inequality - gm? for proof of right inequality it's enough prove $$44(x+y+z)^6\geq(2(x+y+z)^2+9x^2)(2(x+y+z)^2+9y^2)(2(x+y+z)^2+9z^2),$$ $$\sum_{sym}\left(4x^5y+7x^4y^2+3x^3y^3+18x^4yz+70x^3y^2z+\frac{51}{4}x^2y^2z^2\right)\geq0,$$ obvious.

determine number of valid 6-digit integers (ie. no leading zeros) no digits can repeated , such divisible 4 my answer (correct): fact: integer divisible 4 if last 2 digits divisible 4 (eg. 4 16 , 7 56 ) there are $8\times7\times6\times5\times6$ valid 6-digit integers end in $04, 08, 20, 40, 60, 80$ (ie. divisible 4, contains 1 0 , no digit repeated) $7\times7\times6\times5\times16$ valid 6-digit integers end in $12, 16, 24, 28, 32, 36, 48, 52, 56, 64, 68, 72, 76, 84, 92, 96$ (ie. divisible 4, not contain zeros , no digit repeated) $\therefore$ there $(8\times7\times6\times5\times6) + (7\times7\times6\times5\times16)$ valid 6-digit integers no digits can repeated , such divisible 4 my question : is there better (as in less error-prone) way solve original problem hand? (enumerating two-digit numbers divisible 4 , adding amount of such integers correctly bit problematic me) is there better (as in less error-prone) way solve original problem? thi...